首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   76019篇
  免费   8838篇
  国内免费   5186篇
电工技术   6366篇
技术理论   5篇
综合类   6095篇
化学工业   10627篇
金属工艺   4525篇
机械仪表   5278篇
建筑科学   6453篇
矿业工程   2708篇
能源动力   2256篇
轻工业   5599篇
水利工程   1882篇
石油天然气   3799篇
武器工业   958篇
无线电   9714篇
一般工业技术   7713篇
冶金工业   2896篇
原子能技术   1091篇
自动化技术   12078篇
  2024年   499篇
  2023年   1499篇
  2022年   3113篇
  2021年   4314篇
  2020年   3198篇
  2019年   2393篇
  2018年   2655篇
  2017年   2999篇
  2016年   2584篇
  2015年   3959篇
  2014年   4873篇
  2013年   5617篇
  2012年   6674篇
  2011年   6843篇
  2010年   6088篇
  2009年   5611篇
  2008年   5315篇
  2007年   4705篇
  2006年   4047篇
  2005年   3235篇
  2004年   2109篇
  2003年   1406篇
  2002年   1269篇
  2001年   963篇
  2000年   837篇
  1999年   734篇
  1998年   460篇
  1997年   421篇
  1996年   369篇
  1995年   294篇
  1994年   234篇
  1993年   160篇
  1992年   117篇
  1991年   109篇
  1990年   69篇
  1989年   53篇
  1988年   52篇
  1987年   27篇
  1986年   22篇
  1985年   10篇
  1984年   11篇
  1983年   3篇
  1982年   11篇
  1981年   11篇
  1980年   22篇
  1979年   17篇
  1978年   2篇
  1976年   2篇
  1959年   15篇
  1951年   11篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
介绍了超声波固井质量检测仪(UCT)的原理、结构及测井方法,分析了UCT测井资料的应用情况。实践表明,UCT能准确地探测套管腐蚀,直观评价水泥与套管、水泥与地层一、二界面的胶结质量。  相似文献   
82.
根据胜利油田建立实施HSE管理体系工作的现状,提出现阶段推行HSE管理体系要做好五方面的工作。在日常管理工作中,要做到高标准、高质量、严要求、严考核。  相似文献   
83.
We point out that a simpler expression could be derived for the outage probability considered by Chalise and Vandendorpe (2008). As a result, the computation of confluent hypergeometric function of two variables is not needed and the required computational effort is significantly reduced.  相似文献   
84.
In CFD simulation of diesel combustion, the predictive capabilities of the spray model play the most important role. Consequently, under the strict guidelines of the V&V, a method to adjust parameters of diesel spray model WAVE to accompany with the in-cylinder physical progress has been investigated in this paper. Moreover, the simulation of the spray has been validated by high-speed photography experiments and verified by the equation proposed by Hiroyasu. Finally, a modified setup for the WAVE spray model has been proposed and applied in the spray and combustion simulation for Deutz1013 diesel in different engine speed.  相似文献   
85.
Polyoxymethylene (POM) composites filled with low-density polyethylene (LDPE) and rice husk flour (RHF) were prepared by injection molding. The POM/5 wt % LDPE/7.5 wt % RHF composite exhibited the lowest wear rate, whereas the coefficient of friction remained low, and the POM/5 wt % LDPE/5 wt % RHF composite had the best mechanical properties. X-ray diffraction analysis was carried out, and the worn surfaces were examined with scanning electron microscopy. The results showed that the addition of the filler reduced the crystallinity degree of the POM composites. The main wear mechanism for unfilled POM was adhesion, whereas for the POM composites, wear seemed to occur mainly by fatigue and abrasion. It was experimentally confirmed that the POM composite filled with LDPE and RHF, which is well-performing, low-cost, and environmentally friendly, could be a potential material for tribological applications. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   
86.
Recent experiments have shown that metallic materials display significant size effects when the characteristic length scale of non-uniform plastic deformation is close to a micron. Couple stress plasticity has been developed to explain such phenomena by Fleck and Hutchinson. The mechanical behaviors of ultra-thin nickel beams in different boundary conditions were studied with the hybrid element developed for couple stress plasticity before. Strong scale effects are found when the beam's thickness is close to the material characteristic length scale. Such phenomena will disappear if the beam' s thickness is greatly larger than the material characteristic length scale. The scale effect is the beams inherent property and it does not change with the change of support conditions.  相似文献   
87.
Parylene is an emerging material for MEMS. It is an organic material that is grown by using the chemical vapor deposition method at room temperature. The deposition thickness is commonly controlled by the amount of solid-phase dimer loaded in a sublimation chamber. In a conventional deposition machine, the end point of the process is designated by the moment the dimer is exhausted. However, this end-of-process criterion does not offer precise, repeatable control of film thickness. We present the results of the development of an in situ end-point detector for a Parylene chemical vapor deposition process. The detector is based on the thermal transfer principle and can be implemented on commercial parylene deposition systems with minimal system modification. Such a sensor enables a user to stop the deposition when a targeted thickness is reached. The end point detector is very simple to implement on existing parylene deposition systems. A series of such sensors with different target deposition thickness would allow extraction of the actual deposition rate within a deposition run.  相似文献   
88.
本文介绍了配电自动化系统,提出了在兖矿集团驻地6kV配电系统实现自动化的意义,并提出了该系统的实现方案及功能特点。  相似文献   
89.
The ears of lizards are highly directional. The directionality is generated by strong acoustical coupling of the eardrums. A simple lumped-parameter model of the ear followed by binaural comparisons has been shown to perform successful phonotaxis in robot implementations. However, such a model will produce localization errors in the form of response bias if the ears are asymmetrical. We have evaluated how large errors are generated by asymmetry using simulations of the ear model in Mathematica 5.2. The study shows that the effect of asymmetry is minimal around the most directional frequency of the ear, but that biases reduce the useful bandwidth of localization. This work was presented in part at the First European Workshop on Artificial Life and Robotics, Vienna, Austria, July 12–13, 2007  相似文献   
90.
In this work the synergistic effects of microwave (MW) irradiation induced oxidation processes and CoFe2O4 were studied for the degradation of brilliant green (BG) from aqueous solutions. Under the optimum condition, the ratio of solid to liquid was 1:167 (0.3 g CoFe2O4 mixed with 50 mL of 20 mg L−1 BG solution), MW power 600 W, and the time of the irradiation 2 min. And the decolorization rate could reach up to 100%. Further investigation showed that BG was degraded by MW-induced oxidation combined with CoFe2O4 surface adsorption. The CoFe2O4 could increase the efficiencies of MW degradation and be used repeatedly. The experimental results indicated that the method of MW degradation BG in the presence of CoFe2O4 could reduce reaction time and increase product yield.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号