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   18217篇
  免费   1371篇
  国内免费   404篇
电工技术   701篇
综合类   486篇
化学工业   3181篇
金属工艺   591篇
机械仪表   667篇
建筑科学   900篇
矿业工程   166篇
能源动力   472篇
轻工业   1783篇
水利工程   246篇
石油天然气   268篇
武器工业   75篇
无线电   2087篇
一般工业技术   2646篇
冶金工业   3048篇
原子能技术   188篇
自动化技术   2487篇
  2024年   72篇
  2023年   251篇
  2022年   483篇
  2021年   746篇
  2020年   555篇
  2019年   480篇
  2018年   619篇
  2017年   591篇
  2016年   608篇
  2015年   639篇
  2014年   779篇
  2013年   1122篇
  2012年   1080篇
  2011年   1183篇
  2010年   887篇
  2009年   801篇
  2008年   864篇
  2007年   730篇
  2006年   616篇
  2005年   491篇
  2004年   419篇
  2003年   370篇
  2002年   380篇
  2001年   305篇
  2000年   285篇
  1999年   288篇
  1998年   1033篇
  1997年   620篇
  1996年   436篇
  1995年   251篇
  1994年   250篇
  1993年   240篇
  1992年   102篇
  1991年   116篇
  1990年   89篇
  1989年   112篇
  1988年   74篇
  1987年   68篇
  1986年   62篇
  1985年   82篇
  1984年   63篇
  1983年   63篇
  1982年   75篇
  1981年   66篇
  1980年   49篇
  1979年   42篇
  1978年   42篇
  1977年   85篇
  1976年   108篇
  1975年   31篇
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
91.
92.
SKOR, a K+ channel identified in Arabidopsis, displays the typical hydrophobic core of the Shaker channel superfamily, a cyclic nucleotide-binding domain, and an ankyrin domain. Expression in Xenopus oocytes identified SKOR as the first member of the Shaker family in plants to be endowed with outwardly rectifying properties. SKOR expression is localized in root stelar tissues. A knockout mutant shows both lower shoot K+ content and lower xylem sap K+ concentration, indicating that SKOR is involved in K+ release into the xylem sap toward the shoots. SKOR expression is strongly inhibited by the stress phytohormone abscisic acid, supporting the hypothesis that control of K+ translocation toward the shoots is part of the plant response to water stress.  相似文献   
93.
94.
95.
96.
This paper describes the application of an expert system for the evaluation of the short-term thermal rating and temperature rise of overhead conductors. The expert system has been developed using a database and Leonardo expert system shell which is gaining popularity among commercial tools for developing expert system applications. The expert system has been found to compare well when evaluated against site tests. A practical application is given to demonstrate the usefulness of the expert system developed  相似文献   
97.
The adolescent's breaking of the voice is the result of the substitution of the chest voice (or heavy mechanism) for the head voice (or light mechanism). In cases of late breaking, the voice is abnormally high-pitched and feeble, often with a distorted timbre, while the larynx is normal and pubescent. Such people are generally not fully aware of their voices' real nature. Therapy classically resorts to laryngeal manipulations, of which a new technique is put forward. Another therapeutic approach is based, on the one hand, on critical listening compared with a control male voice, thus enabling the subject to become aware of his own voice, and, on the other hand, on high intensity work which helps passing from head to chest voice.  相似文献   
98.
This second article deals with using the Comsis software for a particular application. Simulation is used to determine the maximum channel density in presence of crosstalk. In a first part, the modelling of the system is described. The simulation parameters of different optical elements are given. The results show that in the case of channels modulated at 500 Mbitls using fsk modulation format, and a direct detection operation at 1,5 μm, a minimum spacing of 6 GHz can be obtained with a 2 dB penalty. Thus if only the bandwidth of the erbium doped fibre amplifier is taken into account, the maximum number of channels which can be used is 250. However if the fsr (free spectral range) of optical filter is taken into account, the maximun number of channels is limited to 30.  相似文献   
99.
Crescentic glomerulonephritis in interferon-gamma receptor deficient mice   总被引:1,自引:0,他引:1  
Activation of macrophages by T cells is considered an initiating event in glomerular crescent formation. Since interferon-gamma (INF gamma) is a key mediator in T-cell-mediated activation of macrophages, we decided to test its role in a model of crescentic glomerulonephritis. An anti-glomerular basement membrane (GBM) serum was injected intravenously in presensitized wild-type or IFN gamma receptor deficient (IFN gamma(R)-/-) mice. Glomerulonephritis with glomerular crescents and tubulointerstitial inflammation developed in both strains, even though most evaluated morphological parameters and proteinuria indicated a less severe pathology in the mutant mice compared to the wild type. Thus, IFN gamma is not essential either for glomerular crescent formation or for tubulointerstitial involvement in anti-GBM glomerulonephritis in mice. In conclusion, the role of macrophages in this model might have been overestimated, or other cytokines may compensate for deficient IFN gamma signaling in the activation of macrophages.  相似文献   
100.
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