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   11014篇
  免费   549篇
  国内免费   20篇
电工技术   121篇
综合类   9篇
化学工业   2641篇
金属工艺   301篇
机械仪表   250篇
建筑科学   401篇
矿业工程   30篇
能源动力   261篇
轻工业   1160篇
水利工程   132篇
石油天然气   50篇
武器工业   2篇
无线电   814篇
一般工业技术   2012篇
冶金工业   2078篇
原子能技术   75篇
自动化技术   1246篇
  2023年   88篇
  2022年   196篇
  2021年   288篇
  2020年   225篇
  2019年   211篇
  2018年   284篇
  2017年   273篇
  2016年   286篇
  2015年   232篇
  2014年   320篇
  2013年   649篇
  2012年   532篇
  2011年   627篇
  2010年   425篇
  2009年   442篇
  2008年   501篇
  2007年   473篇
  2006年   384篇
  2005年   357篇
  2004年   314篇
  2003年   269篇
  2002年   279篇
  2001年   138篇
  2000年   145篇
  1999年   150篇
  1998年   210篇
  1997年   180篇
  1996年   184篇
  1995年   161篇
  1994年   150篇
  1993年   166篇
  1992年   121篇
  1991年   116篇
  1990年   138篇
  1989年   110篇
  1988年   84篇
  1987年   132篇
  1986年   103篇
  1985年   133篇
  1984年   126篇
  1983年   132篇
  1982年   105篇
  1981年   98篇
  1980年   78篇
  1979年   74篇
  1978年   92篇
  1977年   74篇
  1976年   82篇
  1975年   79篇
  1974年   83篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
In their public statements, politicians and leaders of mostdeveloped countries espouse the doctrine that the growth oftheir respective economies is highly dependent on innovationsresulting from scientific research and development. Many countriessupport science directly or indirectly using a variety of subsidies,grants, contracts, or other financial mechanisms. But, the lion'sshare of support for research and development is usually providedby industry. The statistic often quoted is the percentage ofgross domestic product  相似文献   
92.
Visual comfort and electric lighting energy issues are essential criteria to justify daylighting schemes. The evaluation of energy efficiency due to daylight linked lighting control systems is best demonstrated by case studies. This paper presents field measurements on daylighting for a fully air-conditioned daylit corridor. Artificial lighting load, brightness of the fluorescent luminaires, daylight availability for various switching illuminance levels were systematically recorded and analyzed. The general features and characteristics of the findings including the number of switching operations and electric-lighting energy savings are presented and discussed. Daylighting theories, using cumulative frequency distribution of outdoor illuminance and regression models based on brightness of light output, outdoor illuminance and electric light power to estimate daylight-linked lighting control savings, have been developed and assessed. It has been found that data from both approaches show reasonably good agreements with measured results. The findings from this study provide some operational and energy information, which would be useful and applicable to other interior spaces with similar architectural designs.  相似文献   
93.
As transistor feature sizes continue to shrink intothe sub-90nm range and beyond, the effects of process variationson critical path delay and chip yields have amplified. A commonconcept to remedy the effects of variation is speed-binning, bywhich chips from a single batch are rated by a discrete range offrequencies and sold at different prices. In this paper, we discussstrategies to modify the number of chips in different bins andhence enhance the profits obtained from them. Particularly, wepropose a scheme that introduces a small Substitute Cacheassociated with each cache way to replicate the data elementsthat will be stored in the high latency lines. Assuming a fixedpricing model, this method increases the revenue by as much as13.8% without any impact on the performance of the chips.  相似文献   
94.
Two studies explored how domestic violence may be implicitly or explicitly sanctioned and reinforced in cultures where honor is a salient organizing theme. Three general predictions were supported: (a) female infidelity damages a man's reputation, particularly in honor cultures; (b) this reputation can be partially restored through the use of violence; and (c) women in honor cultures are expected to remain loyal in the face of jealousy-related violence. Study 1 involved participants from Brazil (an honor culture) and the United States responding to written vignettes involving infidelity and violence in response to infidelity. Study 2 involved southern Anglo, Latino, and northern Anglo participants witnessing a "live" incident of aggression against a woman (actually a confederate) and subsequently interacting with her. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
95.
The aim of this study is to investigate means of efficiently assessing the effects of distributed structural modification on the dynamic properties of a complex structure. The dynamic properties of the modified structure can be determined by experimental testing or numerical simulation, both of which are complex, expensive and time-consuming. Assuming that the original dynamic characteristics are already established and that the modification is a relatively simple attachment, the modified dynamic properties may be determined numerically without solving the equations of motion of the full-modified structure. The frequency response functions (FRFs) of the modified structure can be computed by coupling the original FRFs and a delta dynamic stiffness matrix for the modification introduced. The validity of this approach is investigated by applying it to a cantilever beam to which a smaller beam is attached as modification. The original FRFs were obtained experimentally as well as numerically. The delta dynamic stiffness matrix was determined numerically by modeling the attachment and part of the original structure including the attachment points. The FRFs of the modified beam were then computed. Good agreement is obtained by comparing the results to the FRFs of the modified beam determined experimentally as well as by numerical modeling of the complete modified structure.  相似文献   
96.
Neutron reflectometry (NR) was used to directly measure the interface width between a titanium dioxide and a silicon dioxide film deposited by sol-gel processing. In a bilayer heated to 450°C, NR measurements showed that the interface width is 0.8 nm. This width is the same as the roughness of a sol-gel silicon dioxide surface after the same heat treatment, suggesting no interdiffusion or mixing at the bilayer interface.  相似文献   
97.
This paper describes a fault tolerant mechanical architecture with four levels devised and implemented in concert with NASA (Tesar, D. & Sreevijayan, D., Four-level fault tolerance in manipulator design for space operations. In First Int. Symp. Measurement and Control in Robotics (ISMCR '90), Houston, Texas, 20–22 June 1990.) Subsequent work has clarified and revised the architecture. The four levels proceed from fault tolerance at the actuator level, to fault tolerance via in-parallel chains, to fault tolerance using serial kinematic redundancy, and finally to the fault tolerance multiple arm systems provide. This is a subsumptive architecture because each successive layer can incorporate the fault tolerance provided by all layers beneath. For instance a serially-redundant robot can incorporate dual fault-tolerant actuators. Redundant systems provide the fault tolerance, but the guiding principle of this architecture is that functional redundancies actively increase the performance of the system. Redundancies do not simply remain dormant until needed. This paper includes specific examples of hardware and/or software implementation at all four levels.  相似文献   
98.
99.
100.
Isolated left atrial mural endocarditis is rare. We report a case where the diagnosis was made clinically and supported by blood cultures and transoesophageal echocardiography. Appropriate intravenous antibiotics were administered and serial transoesophageal echocardiograms helped in monitoring the decrease in size and final disappearance of the vegetation, thus avoiding the need for surgical intervention.  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