全文获取类型
收费全文 | 4395篇 |
免费 | 92篇 |
专业分类
公路运输 | 953篇 |
综合类 | 1317篇 |
水路运输 | 1295篇 |
铁路运输 | 473篇 |
综合运输 | 449篇 |
出版年
2024年 | 8篇 |
2023年 | 14篇 |
2022年 | 68篇 |
2021年 | 124篇 |
2020年 | 89篇 |
2019年 | 32篇 |
2018年 | 362篇 |
2017年 | 321篇 |
2016年 | 287篇 |
2015年 | 91篇 |
2014年 | 106篇 |
2013年 | 146篇 |
2012年 | 252篇 |
2011年 | 405篇 |
2010年 | 387篇 |
2009年 | 228篇 |
2008年 | 361篇 |
2007年 | 363篇 |
2006年 | 218篇 |
2005年 | 190篇 |
2004年 | 85篇 |
2003年 | 104篇 |
2002年 | 60篇 |
2001年 | 53篇 |
2000年 | 41篇 |
1999年 | 19篇 |
1998年 | 12篇 |
1997年 | 11篇 |
1996年 | 15篇 |
1995年 | 10篇 |
1994年 | 6篇 |
1993年 | 2篇 |
1992年 | 7篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
排序方式: 共有4487条查询结果,搜索用时 130 毫秒
421.
提高人口素质是顺应当今世界经济迅猛发展、迎接新的科技革命和促进社会主义现代化建设的客观要求。提高人口素质必须制定严格的计划生育政策与法规,控制人口增长,鼓励优生优育;坚持"两个文明"一起抓,大力发展教育事业。当前,在人口数量控制已取得较大进展的前提下,研究邓小平的人口素质观,对于人口研究和人口工作就具有更加重要的意义。认真学习邓小平人口思想,将有助于我们深刻认识我国的经济社会和人口发展的战略目标,坚定不移地贯彻执行计划生育、控制人口增长的基本国策。 相似文献
422.
利用BP网络分别结合L-M、贝叶斯算法研究溶解氧与BOD5、PH值、流量、水温关系,表明利用贝叶斯算法优化的网络更适合于预测。 相似文献
423.
Web应用已由原来的网站、电子商务发展成商业应用系统的一种架构-B/S架构,它已成为一个世界性的研究热点。但由于Internet网络协议固有的局限性以及Web应用中频繁的用户交互增加了在Internet上实现长事务的困难,从而,Web应用中的并发控制始终没能得到很好的解决。本文从Hibernate的乐观锁和悲观锁的实现原理出发,给出了实现悲观锁的基本思路和实现时的注意事项,在其它架构中得以推广和应用。 相似文献
424.
Eleftheria Eliopoulou Apostolos Papanikolaou 《Journal of Marine Science and Technology》2007,12(4):240-250
This article presents detailed results of a comprehensive analysis of recorded accidents of large oil tankers (deadweight
greater than 80 000 tonnes) occurring between 1978 and 2003. The analysis encompasses a thorough review of available raw accident
data and their postprocessing in a way to produce appropriate statistics useful for the implementation of risk-based assessment
methodologies. The processing of the captured data led to the identification of significant qualitative historical trends
of tanker accidents and of quantitative characteristics of large tanker accidents, such as overall accident rates per ship-year.
Data were also analyzed for all major accident categories separately, taking into account tanker ship size/type, the degree
of accident severity, and the oil spill tonne rates per ship-year; this led to the identification of heavily polluted worldwide
geographical areas as a result of large tanker accidents. 相似文献
425.
运用FLAC~(3D)软件对郑州某基坑工程进行了开挖与支护模拟计算,对基坑稳定性进行了分析,对土钉支护工作机理进行初步研究,得到基坑边坡变形和受力以及土钉受力的规律。最后结果表明应用FLAC~(3D)程序对基坑土钉支护的数值模拟是可行的,通过计算得出不同开挖阶段的基坑边坡位移、基底隆起以及对土钉拉力为工程设计与施工提供参考。 相似文献
426.
Phase change analysis of an underwater glider propelled by the ocean's thermal energy 总被引:1,自引:0,他引:1
KONG Qiao-ling MA Jie 《船舶与海洋工程学报》2007,6(4):37-43
The phase change characteristic of the power source of an underwater glider propelled by the ocean's thermal energy is the key factor in glider attitude control. A numerical model has been established based on the enthalpy method to analyze the phase change heat transfer process under convective boundary conditions. Phase change is not an isothermal process, but one that occurs at a range of temperature. The total melting time of the material is very sensitive to the surrounding temperature. When the temperature of the surroundings decreases 8 degrees, the total melting time increases 1.8 times. But variations in surrounding temperature have little effect on the initial temperature of phase change, and the slope of the temperature time history curve remains the same. However, the temperature at which phase change is completed decreases significantly. Our research shows that the phase change process is also affected by container size, boundary conditions, and the power source's cross sectional area. Materials stored in 3 cylindrical containers with a diameter of 38ram needed the shortest phase change time. Our conclusions should be helpful in effective design of underwater glider power systems. 相似文献
427.
薪酬问题是所有企业都非常关注而又费神的一个问题,长期以来,受各种因素的影响,我国中小民营企业的薪酬管理已成为企业发展过程中的一个"雷区",制定合理的民企薪酬管理制度对转变民营企业经营理念和行为,适应市场竞争,实现企业永续经营有着重要意义.本文揭示了当前我国中小民营企业在薪酬管理方面存在的一些普遍性问题,相信对民营企业的改革和发展具有一定的借鉴意义. 相似文献
428.
Proshanto K. Mukherjee 《WMU Journal of Maritime Affairs》2007,6(2):147-166
Within the comprehensive body of law encompassed by the International Convention on Safety of Life at Sea, 1974 (SOLAS), there
are two regimes that are topical and outstanding in the current maritime milieu. These are the international safety management
and the international ship and port facility regimes, both characterized by two codes serving as the centre of gravity of
each, namely, the ISM Code and the ISPS Code, respectively. In this article the concept of the code as a legal instrument
is perused following which a critical legal analysis is carried out of the two above-mentioned Codes, including their backgrounds,
the evolutionary process culminating into the regimes and their interrelationships. Several anomalies and inadequacies in
the two regimes are identified but in the final analysis it is concluded that both instruments are salutary additions to the
body of convention law generated by the International Maritime Organization (IMO). They will undoubtedly influence the continuing
development of international law in the field of maritime safety and security. 相似文献
429.
Junbo Jia 《Journal of Marine Science and Technology》2007,12(1):43-57
To reduce the area on deck occupied by each car and the labour and time required for lashing and unlashing cars, it has been
proposed by the author that in some conditions, cars on decks could be transported without lashing. To evaluate cargo securing
based on this “lashing-free” concept, computational code was developed to calculate the vehicle–deck interactions for various
ship motions. The code was structured by incorporating a vehicle model into a piece of ship motion calculation code. A series
of time-domain simulations were conducted to evaluate vehicle securing. It was found that for a target ship consisting of
a 6000-unit Ro-Ro vessel, vehicle securing is mainly influenced by the ship's rolling motions and is highly dependent on the
wave height and loading conditions. It was suggested from the analysis that vehicles could be secured without being lashed
in a large area of the ship in specific weather conditions and on some routes with less adverse sea states. However, it is
still suggested that conventional lashing holes should be constructed on the deck because in severe sea states the cars will
still need to be lashed. The limitations of the current investigations are also presented.
The relevant research work was carried out at the Division of Ship Design and Engineering, Department of Shipping and Marine
Technology, Chalmers University of Technology. 相似文献
430.
随着各国越来越重视保护海洋环境,船舶垃圾的处理问题也越来越受到人们的关注。通过对水面舰艇固体垃圾的种类、数量和处理方法的介绍,并根据国内外船舶垃圾处理方面的一些法规要求,考虑到不同类型水面舰艇的特点,提出了相应的固体垃圾处理对策。 相似文献