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   18534篇
  免费   479篇
  国内免费   19篇
电工技术   239篇
综合类   9篇
化学工业   3642篇
金属工艺   283篇
机械仪表   319篇
建筑科学   1105篇
矿业工程   109篇
能源动力   507篇
轻工业   1427篇
水利工程   163篇
石油天然气   196篇
武器工业   1篇
无线电   1096篇
一般工业技术   2929篇
冶金工业   4340篇
原子能技术   166篇
自动化技术   2501篇
  2022年   138篇
  2021年   216篇
  2020年   176篇
  2019年   227篇
  2018年   275篇
  2017年   265篇
  2016年   325篇
  2015年   246篇
  2014年   389篇
  2013年   1119篇
  2012年   676篇
  2011年   889篇
  2010年   686篇
  2009年   669篇
  2008年   875篇
  2007年   882篇
  2006年   696篇
  2005年   729篇
  2004年   565篇
  2003年   579篇
  2002年   516篇
  2001年   334篇
  2000年   311篇
  1999年   311篇
  1998年   345篇
  1997年   327篇
  1996年   320篇
  1995年   352篇
  1994年   282篇
  1993年   319篇
  1992年   275篇
  1991年   168篇
  1990年   240篇
  1989年   288篇
  1988年   208篇
  1987年   221篇
  1986年   216篇
  1985年   271篇
  1984年   268篇
  1983年   235篇
  1982年   222篇
  1981年   217篇
  1980年   174篇
  1979年   191篇
  1978年   176篇
  1977年   179篇
  1976年   162篇
  1975年   182篇
  1974年   167篇
  1973年   133篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
International Journal of Computer Vision -  相似文献   
32.
33.
A gypsum wall assembly was exposed to an intense real‐scale compartment fire. For the wall assembly, temperatures were measured at the exposed face, within the stud cavity, and at the unexposed face during the fire exposure. Total heat flux gauges were used to measure the temporal variation of the energy incident on the walls, and cameras, both visual and infrared, were used to image the unexposed face of the wall assembly during the fire exposure. The behaviour of the wall assembly under the fire load is discussed as are current model results for a simulation of the fire test. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
34.
This paper describes a design for an analog phase shifter operating at 915 MHz and suitable for use in a phased array microwave hyperthermia system. Here, the major operating constraint was minimization of amplitude variation over a 1800 phase shift, whereas previous phase shifters were designed to obtain a linear relationship between phase and control voltage. The result is a simple, inexpensive hybrid coupler phase shifter that operates over a narrow bandwidth and provides 180°of continuous phase shift with input powers up to 1 W.  相似文献   
35.
36.
A failure analysis case study is presented for a two-piece aerosol containing tetrafluoroethane, commonly referred to as Refrigerant 134a. A gentleman was preparing to recharge the air conditioning system of an automobile when the bottom exploded off the aerosol container, propelling the body of the aerosol container like a rocket, which hit the man in the eye and blinded him in that eye. The aerosol was never connected to the air conditioner, therefore backpressure from the air conditioner (AC) compressor was ruled out as a cause for the explosion. The objective of the study was to determine why the aerosol exploded. Several recently developed test methods were used, including two types of heat-to-burst tests and a puncture chamber to measure the pressure-versus-temperature behavior of aerosols. More common test methods were also used, such as water bath pressure tests, hydro pressure burst tests, pneumatic pressure burst tests, hardness measurements, weight measurements, metallography, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and an accident scenario recreation. A semi-empirical correlation between the hardness and weights of the container bottoms was used to determine the explosion temperature and/or pressure. This semi-empirical correlation agrees in principle with an analysis of the explosion pressures using finite-element analysis (FEA). The root cause for the explosion was determined to be a lack of strength of the bottom of the two-piece aerosol coupled with heating the aerosol to temperatures significantly above room temperature.  相似文献   
37.
38.
This article compiles results from a century of social psychological research, more than 25,000 studies of 8 million people. A large number of social psychological conclusions are listed alongside meta-analytic information about the magnitude and variability of the corresponding effects. References to 322 meta-analyses of social psychological phenomena are presented, as well as statistical effect-size summaries. Analyses reveal that social psychological effects typically yield a value of r equal to .21 and that, in the typical research literature, effects vary from study to study in ways that produce a standard deviation in r of .15. Uses, limitations, and implications of this large-scale compilation are noted. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
39.
Failure surface orientations are determined for states of uniaxail tensile stress and shiar stree appropriate to fracture Modes I and II. The method uses a newly developed failure criterion along with the associated flow rule. The failure angles show a sharp demarcation between ductile and brittle material types. Only the brittle materials class show consistency and likely represents a shear localization effect rether than explicit fracture.  相似文献   
40.
The dimensional changes of liver sections during the course of processing with glycol methacrylate (GMA) or with ethanol are described. Tissue processing with ethanol served as a control. During prolonged processing steps (24 h each), linear shrinkage of tissue specimens dehydrated with GMA at room temperature was 13.2%. Subsequent infiltration with GMA resulted in trivial swelling, and polymerization in slight shrinkage (2.3%). In comparison, processing with cold GMA resulted in shrinkage during dehydration (about 10.8%), a slight swelling in pure GMA, followed by shrinkage during polymerization (2.2%). Short routine processing schedules resulted in similar shrinkage/swelling patterns, although precise values differed slightly. In all experiments, ethanolic dehydration resulted in smaller dimensional tissue changes than did GMA dehydration. The dimensional changes of tissue sections during stretching on water, mounting and drying compensated for the major part of the shrinkage manifested during processing.  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