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901.
文中采用溶胶-凝胶法,以正硅酸乙酯(TEOS)为硅源,氨水为催化剂,醇为溶剂,制备了 SiO2微球,并研究了正硅酸乙酯添加方式、溶剂类型、反应温度对其形貌和粒径的影响。通过 SEM,XRD,FT - IR,UV - Vis 测试分析 SiO2微球的形貌、结构、成分以及光学性能。结果表明,正硅酸乙酯水解对醇溶剂有选择性,乙醇作为溶剂合成 SiO2的分散性和球形较好,溶剂类型对 SiO2紫外吸收影响不大,SiO2对200~250 nm 紫外线吸收最强。逐步滴定法更利于 SiO2的合成,而 TEOS 添加方式对其非晶化程度影响不大。温度变化会影响氨水催化效率,进而会影响生成 SiO2的粒径。 相似文献
902.
903.
Ella Graham-Rowe Stephen Skippon 《Transportation Research Part A: Policy and Practice》2011,45(5):401-418
Transport accounts for nearly a quarter of current energy-related carbon dioxide emissions with car travel constituting more than three quarters of all vehicle kilometres travelled. Interventions to change transport behaviour, and especially to reduce car use, could reduce CO2 emissions from road transport more quickly than technological measures. It is unclear, however, which interventions are effective in reducing car use and what the likely impact of these interventions would be on CO2 emissions. A two-stage systematic search was conducted focusing on reviews published since 2000 and primary intervention evaluations referenced therein. Sixty-nine reviews were considered and 47 primary evaluations found. These reported 77 intervention evaluations, including measures of car-use reduction. Evaluations of interventions varied widely in the methods they employed and the outcomes measures they reported. It was not possible to synthesise the findings using meta-analysis. Overall, the evidence base was found to be weak. Only 12 of the 77 evaluations were judged to be methodologically strong, and only half of these found that the intervention being evaluated reduced car use. A number of intervention approaches were identified as potentially effective but, given the small number of methodologically strong studies, it is difficult to draw robust conclusions from current evidence. More methodologically sound research is needed in this area. 相似文献
904.
把一种基于stirling内插公式的插值滤波器(DDF),应用于单站外辐射源无源定位中的非线性滤波问题。与传统扩展kalman滤波(EKF)相比,插值滤波器避免了非线性方程泰勒展开求解的过程,同时实现复杂性和计算量都很小。计算机仿真表明,一阶插值滤波(DD1)滤波精度相当EKF,而二阶插值滤波(DD2)滤波精度接近甚至略优于无轨迹kalman滤波(UKF)。 相似文献
905.
为了处理动态需求和实现需求到设计的映射,本文提出基于目标和模式的体系结构设计过程,实现了需求到设计的过渡,并提出目标层次和元素层次,实现了需求的可跟踪。最后针对缺陷和测试用例管理等方面的计算机辅助工具的设计给出了基于J2EE模式的体系结构设计的一个实例。 相似文献
906.
纳米TiO_2光催化空气净化技术研究进展 总被引:3,自引:0,他引:3
本文对纳米TiO2光催化净化空气中挥发性有机化合物(VOCs)的技术原理、国内外研究现状和进展进行概述,简介部分使用光催化空气净化技术的商业产品,展望该技术的应用前景。 相似文献
907.
京郑既有线CTCS2级信号系统方案研究 总被引:2,自引:0,他引:2
分析了京郑线信号系统既有低频信息的特殊性,提出了在京郑线提速200km/h,车载设备能够兼容其他提速200km/h线路的CTCS2解决方案,工程可实施性强。 相似文献
908.
Alexandra Weiss Joachim Kuss Gerhard Peters Bernd Schneider 《Journal of Marine Systems》2007,66(1-4):130
Long-term observations of the marine atmospheric boundary layer were performed by an eddy correlation system, which was set-up on a platform in the Baltic Sea. In this experiment the three-dimensional wind vector and the turbulent fluxes of momentum, sensible and latent heat and CO2 were measured for one and a half years. Simultaneously the CO2 partial pressure pCO2 in surface water was measured by a submersible autonomous moored instrument for CO2 at the platform in 7-m depth. The high-resolution eddy correlation measurements of the atmospheric CO2 flux FCO2, together with the measurements of the CO2 partial pressure differences between air and sea ΔpCO2 led to a long-term data set which provided the possibility to investigate the parameterization of the CO2 transfer velocity k as a function of 10-m wind speed u in a statistical manner. From half-hour mean CO2 fluxes and CO2 partial pressure differences, k was calculated using k = FCO2 / (K0ΔpCO2), with K0 the CO2 solubility. The half-hour mean data points, used for the determination of the k–u parameterization, show large scatter. However, assuming a linear, quadratic dependency the analysis yields: k660 = 0.365u2 + 0.46u (k at 20 °C and salinity 35 psu) with a correlation coefficient of r2 = 0.81. The large scatter indicates that the kinetics of the air–sea CO2 transfer velocity is not only a function of the wind speed alone, but might also be controlled by other environmental parameters and mechanisms, such as sea state and surface coverage with surfactants. 相似文献
909.
研究目的:上海地铁2号线既有线和2号线东延伸在龙阳路与张江高科区间的高架梁上完成拨接,为国内首次在高架梁上整体道床的拨移工程,具有很大的技术难度。本文结合该项目的成功实施,阐述整体道床拨移工程的设计思路及施工方案,对类似工程具有借鉴意义。研究结论:针对该工程封锁时间短、精度要求高、首次实施等特点,比选多种设计方案。3号梁采用了在既有轨枕间浇注承轨台方案,4~7号梁道床采用在梁场预制纵向短枕承轨台的方案,无缝线路采用现场焊接方案,并成功实施拨移工程。该工程对整体道床改造、维修方法的探索,对城市轨道交通延伸线路与既有线的轨道拨接具有重要的参考意义。 相似文献
910.