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   18757篇
  免费   796篇
  国内免费   21篇
电工技术   255篇
综合类   18篇
化学工业   3946篇
金属工艺   331篇
机械仪表   411篇
建筑科学   1034篇
矿业工程   49篇
能源动力   534篇
轻工业   1725篇
水利工程   131篇
石油天然气   56篇
武器工业   1篇
无线电   1630篇
一般工业技术   3216篇
冶金工业   3075篇
原子能技术   190篇
自动化技术   2972篇
  2023年   171篇
  2022年   318篇
  2021年   490篇
  2020年   357篇
  2019年   398篇
  2018年   445篇
  2017年   403篇
  2016年   515篇
  2015年   463篇
  2014年   550篇
  2013年   1118篇
  2012年   897篇
  2011年   1170篇
  2010年   782篇
  2009年   845篇
  2008年   882篇
  2007年   784篇
  2006年   727篇
  2005年   612篇
  2004年   502篇
  2003年   455篇
  2002年   433篇
  2001年   305篇
  2000年   329篇
  1999年   352篇
  1998年   757篇
  1997年   494篇
  1996年   399篇
  1995年   293篇
  1994年   283篇
  1993年   272篇
  1992年   184篇
  1991年   158篇
  1990年   141篇
  1989年   141篇
  1988年   123篇
  1987年   119篇
  1986年   114篇
  1985年   139篇
  1984年   135篇
  1983年   117篇
  1982年   90篇
  1981年   102篇
  1980年   87篇
  1979年   96篇
  1978年   89篇
  1977年   117篇
  1976年   139篇
  1975年   79篇
  1974年   73篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
4.
Software and Systems Modeling - Many model transformation scenarios require flexible execution strategies as they should produce models with the highest possible quality. At the same time,...  相似文献   
5.
6.
Antibiotics are potentially a cause of neurotoxicity in dialysis patients, the most common are the beta‐lactams as ceftazidime and cefepime, and few cases have been reported after piperacillin/tazobactam use. This report presents a case of a hypertensive and diabetic 67‐year‐old woman in regular hemodialysis, which previously had a stroke. She was hospitalized presenting pneumonia, which was initially treated with cefepime. Two days after treatment, she presented dysarthria, left hemiparesis, ataxia, and IX and X cranial nerves paresis. Computed tomography showed no acute lesions and cefepime neurotoxicity was hypothesized, and the antibiotic was replaced by piperacillin/tazobactam. The neurologic signs disappeared; however, 4 days after with piperacillin/tazobactam treatment, the neurological manifestations returned. A new computed tomography showed no new lesions, and the second antibiotic regimen withdrawn. After two hemodialysis sessions, the patient completely recovered from neurological manifestations. The patient presented sequentially neurotoxicity caused by two beta‐lactams antibiotics. This report meant to alert clinicians that these antibiotics have dangerous neurological effects in chronic kidney disease patients.  相似文献   
7.
A novel compact stop band filter consisting of a 50 /spl Omega/ coplanar waveguide (CPW) with split ring resonators (SRRs) etched in the back side of the substrate is presented. By aligning SRRs with the slots, a high inductive coupling between line and rings is achieved, with the result of a sharp and narrow rejection band in the vicinity of the resonant frequency of the rings. In order to widen the stop band of the filter, several ring pairs tuned at equally spaced frequencies within the desired gap are cascaded. The frequency response measured in the fabricated prototype device exhibits pronounced slopes at either side of the stop band and near 0 dBs insertion loss outside that band. Since SRR dimensions are much smaller than signal wavelength, the proposed filters are extremely compact and can be used to reject frequency parasitics in CPW structures by simply patterning properly tuned SRRs in the back side metal. Additional advantages are easy fabrication and compatibility with MMIC or PCB technology.  相似文献   
8.
Methods are described for sample preparation of polycrystalline Ni-based superalloys in order to perform a detailed microstructural characterization. Specific techniques for the precise definition of the various phases present are outlined and these are shown to be useful for the measurement of size, volume fractions and distribution. A number of optical, scanning and transmission microscopy techniques are used to provide the necessary information.  相似文献   
9.
The present empirical investigation had a 3-fold purpose: (a) to cross-validate L. R. Offermann, J. K. Kennedy, and P. W. Wirtz's (1994) scale of Implicit Leadership Theories (ILTs) in several organizational settings and to further provide a shorter scale of ILTs in organizations; (b) to assess the generalizability of ILTs across different employee groups, and (c) to evaluate ILTs' change over time. Two independent samples were used for the scale validation (N1 = 500 and N2 = 439). A 6-factor structure (Sensitivity, Intelligence, Dedication, Dynamism, Tyranny, and Masculinity) was found to most accurately represent ELTs in organizational settings. Regarding the generalizability of ILTs, although the 6-factor structure was consistent across different employee groups, there was only partial support for total factorial invariance. Finally, evaluation of gamma, beta, and alpha change provided support for ILTs' stability over time. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
10.
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