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   10571篇
  免费   169篇
  国内免费   20篇
电工技术   114篇
综合类   32篇
化学工业   1148篇
金属工艺   117篇
机械仪表   311篇
建筑科学   248篇
矿业工程   39篇
能源动力   194篇
轻工业   878篇
水利工程   49篇
石油天然气   11篇
武器工业   2篇
无线电   654篇
一般工业技术   1269篇
冶金工业   4824篇
原子能技术   121篇
自动化技术   749篇
  2022年   53篇
  2021年   66篇
  2020年   67篇
  2019年   82篇
  2018年   64篇
  2017年   72篇
  2016年   74篇
  2015年   62篇
  2014年   111篇
  2013年   391篇
  2012年   191篇
  2011年   276篇
  2010年   211篇
  2009年   213篇
  2008年   242篇
  2007年   241篇
  2006年   238篇
  2005年   175篇
  2004年   189篇
  2003年   176篇
  2002年   155篇
  2001年   148篇
  2000年   145篇
  1999年   255篇
  1998年   1479篇
  1997年   830篇
  1996年   624篇
  1995年   353篇
  1994年   313篇
  1993年   366篇
  1992年   139篇
  1991年   143篇
  1990年   148篇
  1989年   152篇
  1988年   127篇
  1987年   149篇
  1986年   139篇
  1985年   140篇
  1984年   114篇
  1983年   91篇
  1982年   95篇
  1981年   135篇
  1980年   120篇
  1979年   101篇
  1978年   87篇
  1977年   168篇
  1976年   305篇
  1975年   82篇
  1974年   50篇
  1973年   73篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
The sector - also known as the proportional, geometric, or military compass - was an analog calculating instrument used widely from the late 16th century until modern times. The origins and usage of this commonly encountered instrument are not well known. This article provides historical background on the sector's invention and on its precursor instruments, and describes the uses for many of the scales commonly found on these instruments.  相似文献   
72.
73.
Literature suggests that a complex and often hostile relationship exists between the science and practice of clinical psychology. Contributors to this conflict of viewpoints are reconsidered within the proposition that there are different roads to discovery and that there may be good reasons to keep the science and practice of clinical psychology somewhat separate. Results of a national survey of 325 psychologists are reviewed that support the view that psychological practitioners value research and consider their practices to be augmented by scientific findings. However, they are in need of vehicles of communication that will help them translate scientific findings into practice. Results suggest that practitioners do more to understand scientific findings than scientists do to understand the problems that face clinical practitioners. Ways to facilitate communication between and among these groups are considered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
74.
75.
A competitive enzyme-linked immunoadsorbent assay (ELISA) technique has been developed to facilitate quantitative analysis of the earliest step in the initiation of the extrinsic pathway of coagulation, i.e., complex formation of factor VII/VIIa with tissue factor. The ELISA measures the binding of biotinylated human plasma factor VII to relipidated recombinant human tissue factor. Quantitation of the relative affinity (expressed as IC50) of any factor VII molecular population or structural analogue for tissue factor can be determined by competitive binding. Subnanomolar concentrations of both wild-type recombinant human factor VII (rFVII) and rFVII(R152Q), a mutation at the FVII activation site, competed effectively with biotinylated plasma-derived factor VII in binding to tissue factor. In contrast, the affinity of rFVII(R79Q), a mutation in the first epidermal growth factor-like domain, was 12-fold lower. Following activation of rFVII(R79Q), its affinity for tissue factor and enzymatic activity increased 4-fold and 6-fold, respectively. For wild-type rFVII, enzymatic activity rose significantly following activation. However, its affinity for tissue factor was unchanged. We conclude that both the activation state of factor VII and the mutation of amino-acid residues within the first epidermal growth factor-like domain may alter the affinity of factor VII for tissue factor.  相似文献   
76.
Memory reallocation is used to construct a run-time data structure for fast/efficient storage of information during collection and analysis. The data structure presented uses dynamic memory but does not require the use of pointers to link nodes of information together. It allows for simple and efficient access to data via array indexing rather than through the use of lists or tree structures and it provides flexibility for competing storage requirements that are determined dynamically. The data structure is developed in the C programming language and a suite of ANSI standard C subroutines that make up a run-time data structure management system is provided.  相似文献   
77.
Electrical characterization of evaporated ZnS:Mn alternating-current thin-film electroluminescent (ACTFEL) devices is accomplished by capacitance-voltage (C-V) analysis. Interpretation of these C-V characteristics is aided by SPICE modeling and by electrical characterization of an ideal ACTFEL device constructed from discrete components, based on a simple equivalent circuit for the ACTFEL device. Various features of the C -V curve are ascribed to equivalent circuit parameters and associated device physics parameters  相似文献   
78.
This article examines factors that may contribute to errors in drug administration. These can range from the omission of a single dose of a non-essential drug to a major overdose resulting in serious harm to a patient. It concludes that a combination of being observant and well-informed can help to prevent errors.  相似文献   
79.
80.
Free radicals react with nitrones to form stable nitroxides which can be identified by ESR spectroscopy. Unfortunately, little is known regarding the pharmacological properties of these compounds. In this study, three commonly used nitrones, 5,5-dimethylpyrroline-N-oxide (DMPO), alpha-phenyl-tert-butylnitrone (PBN), and alpha-(4-pyridyl 1-oxide)-N-tert-butylnitrone (POBN), were found to induce relaxation of preconstricted isolated rat pulmonary artery rings. Additional experiments with PBN indicated that vasorelaxation could not be attributed to production of endothelial derived factors, prostaglandins, or free radicals. Patch-clamp techniques revealed reversible calcium channel blockade with PBN at a concentration below that needed to detect free radicals. Calcium channel blockade probably accounts for the vasorelaxation observed in the isolated ring preparations described here, and should be considered when using nitrone spin-traps both in in vivo and clinical studies.  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