全文获取类型
收费全文 | 2390篇 |
免费 | 21篇 |
专业分类
公路运输 | 328篇 |
综合类 | 799篇 |
水路运输 | 787篇 |
铁路运输 | 124篇 |
综合运输 | 373篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 7篇 |
2021年 | 17篇 |
2020年 | 20篇 |
2019年 | 3篇 |
2018年 | 339篇 |
2017年 | 293篇 |
2016年 | 254篇 |
2015年 | 17篇 |
2014年 | 20篇 |
2013年 | 25篇 |
2012年 | 83篇 |
2011年 | 238篇 |
2010年 | 255篇 |
2009年 | 101篇 |
2008年 | 211篇 |
2007年 | 179篇 |
2006年 | 64篇 |
2005年 | 91篇 |
2004年 | 46篇 |
2003年 | 62篇 |
2002年 | 36篇 |
2001年 | 10篇 |
2000年 | 14篇 |
1999年 | 2篇 |
1998年 | 6篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1984年 | 2篇 |
排序方式: 共有2411条查询结果,搜索用时 9 毫秒
361.
深水SPAR平台截断技术研究 总被引:1,自引:0,他引:1
To solve the dimensional limitations of physical models in tests, an equivalent water depth truncated design for a classical SPAR working in 913 m water was investigated. The water depth was reduced to 736m and then to 552m. As this was done, the mooring line lengths, EA value, and mass per meter were adjusted. Truncation rules and formulas for parameters and truncation factors were proposed. SPAR static characteristics were made to be consistent with those at full water depth. Then further time-domain coupled analysis was carried out for the SPAR when the mooring system experienced waves. The mooring lines were simulated by quasi-static method. Global responses and mooring line forces were found to agree well with test results for a prototype at that water depth. The truncation method proved to be robust and reliable. 相似文献
362.
实际海浪环境大尺度模型试验遥控遥测系统 总被引:1,自引:0,他引:1
Physical testing of large-scale ship models at sea is a new experimental method. It is a cheap and reliable way to research the environment adaptability of a ship in complex and extreme wave conditions. It is necessary to have a stable experimental system for the test. Since the experimental area is large, a remote control system and a telemetry system are essential, and were designed by the authors. An experiment was conducted on the Songhuajiang River to test the systems. The relationship between the model’s speed and its electromotor’s revolutions was also measured during the model test. The results showed that the two systems make it possible to carry out large-scale model tests at sea. 相似文献
363.
基于SPH方法的波浪对水平板冲击的数值模拟 总被引:1,自引:0,他引:1
A numerical model was established for simulating wave impact on a horizontal deck by an improved incompressible smoothed particle hydrodynamics (ISPH). As a grid-less particle method, the ISPH method has been widely used in the free-surface hydrodynamic flows with good accuracy. The improvement includes the employment of a corrective function for enhancement of angular momentum conservation in a particle-based calculation and a new estimation method to predict the pressure on the horizontal deck. The simulation results show a good agreement with the experiment. The present numerical model can be used to study wave impact load on the horizontal deck. 相似文献
364.
基于相位差的方位估计 总被引:2,自引:0,他引:2
The phase difference method (PDM) is presented for the direction of arrival (DOA) estimation of the narrowband source. It estimates the DOA by measuring the reciprocal of the phase range of the sensor output spectra at the interest frequency bin. The peak width and variance of the PDM are presented. The PDM can distinguish closely spaced sources with different and unknown center frequencies as long as they are separated with at least one frequency bin. The simulation results show that the PDM has a better resolution than that of the conventional beamforming. 相似文献
365.
366.
To evaluate the clinical outcome, effectiveness and safety of the surgical management of traumatic lumbar spondylolisthesis with transforaminal lumbar interbody fusion (TLIF) with short segmental instrumentation fixation. A retrospective review of a consecutive series of 24 patients with traumatic lumbar spondylolisthesis treated with TLIF procedure was carried out. Intraoperative spinal cord monitoring was used to confirm the peripheral neural function intact during the reduction of the spondylolisthesis. Preoperative clinical and radiographic evaluation of all cases were originally collected prospectively. Data regarding blood loss, operative time, duration of hospital stay, radiographic fusion, instrumentation failure and clinical result were collected and observed at regular follow-up periods. All patients were engaged in high-energy accidents in the lower back and 16 patients had concomitant injuries. The mean operative time was 124 min, mean blood loss was 350 mL, and mean hospital stay was 6.5 days. There were no complications such as incision infection, cerebrospinal fluide (CSF) leakage and nerve root injury and so on. All patients demonstrated a solid lumbar interbody fusion within 4 months, and no evidence of spondylolisthesis correction loss, instrumentation failure and loosing. They all were completely asymptomatic, with normal neurologic findings, and had resumed their previous level of physical activities on the final follow-up. Meticulous clinical examination and careful imaging assessment could assist an early diagonosis in cases of traumatic lumbar spondylolisthesis. Performing open reduction and the TLIF procedure as soon as possible could restore segmental stability and painless function. The TLIF procedure was a safe, effective technique to treat traumatic lumbar spondylolisthesis. 相似文献
367.
China National Stadium, also known as “Bird’s Nest”, is the main stadium of the 29th Olympic Games in Beijing in 2008, which has successfully held not only the Opening and the Closing ceremonies but also the track and field events. A new problem of rain preventing is brought out to improve the utilization of the Bird’s Nest after the Olympic Games. The scheme of installing an air inflated membrane at the opening of the steel structure is proposed in this paper to solve the rainproof problem of the Bird’s Nest. The form-finding and mechanical analyses of the air inflated membrane are carried out. Comparison between the mechanical performance and dynamical character before and after installing the air inflated membrane structure is given. To verify the analysis results, based on the practical structure of the Bird’s Nest, a test of a 1:20 model membrane is worked out. 相似文献
368.
Face recognition via adaptive image combination 总被引:1,自引:0,他引:1
于威威 《上海交通大学学报(英文版)》2010,15(5):600-603
Dimension reduction and manifold learning are the two most popular feature extraction methods. The two methods focus on spatial locality as a guiding principle to find a low-dimensional basis for describing high-dimensional data, but no bases or features are more spatially localized than the original image pixels. So, adaptive image combination is presented to represent a class by a combined sample. The combined sample is a linear combination of original samples in the same class. Adaptive image combination (AIC) find the best combination coefficients by minimizing the intrapersonal distance and maximizing the interpersonal distance. Experimental results show that AIC is effective. 相似文献
369.
结合现行国际法制计量组织(OIML)国际建议R106《自动轨道衡》以及我国轨道衡检定的实际情况,分析对JJG234—1990《动态称量轨道衡》的修订应关注的若干问题,包括检定规程的名称,准确度等级、分度值和最大允许误差,法制管理要求和检定方法等方面。 相似文献
370.