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   3672篇
  免费   246篇
  国内免费   5篇
电工技术   39篇
综合类   2篇
化学工业   1196篇
金属工艺   75篇
机械仪表   61篇
建筑科学   86篇
矿业工程   11篇
能源动力   105篇
轻工业   659篇
水利工程   19篇
石油天然气   19篇
无线电   246篇
一般工业技术   574篇
冶金工业   418篇
原子能技术   5篇
自动化技术   408篇
  2024年   9篇
  2023年   44篇
  2022年   231篇
  2021年   233篇
  2020年   82篇
  2019年   124篇
  2018年   140篇
  2017年   140篇
  2016年   137篇
  2015年   105篇
  2014年   144篇
  2013年   250篇
  2012年   209篇
  2011年   217篇
  2010年   181篇
  2009年   189篇
  2008年   196篇
  2007年   129篇
  2006年   138篇
  2005年   103篇
  2004年   96篇
  2003年   77篇
  2002年   82篇
  2001年   52篇
  2000年   54篇
  1999年   45篇
  1998年   141篇
  1997年   93篇
  1996年   59篇
  1995年   42篇
  1994年   28篇
  1993年   29篇
  1992年   10篇
  1991年   5篇
  1990年   8篇
  1989年   10篇
  1988年   4篇
  1987年   7篇
  1986年   13篇
  1985年   7篇
  1984年   6篇
  1983年   7篇
  1982年   3篇
  1981年   3篇
  1978年   5篇
  1977年   9篇
  1976年   15篇
  1975年   2篇
  1973年   2篇
  1911年   2篇
排序方式: 共有3923条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
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   
6.
A paralytic peptide, psi-conotoxin Piiie has been purified and characterized from Conus purpurascens venom. Electrophysiological studies indicate that the peptide inhibits the nicotinic acetylcholine receptor (nAChR). However, the peptide does not block the binding of alpha-bungarotoxin, a competitive nAChR antagonist. Thus, psi-conotoxin Piiie appears to inhibit the receptor at a site other than the acetylcholine-binding site. As ascertained by sequence analysis, mass spectrometry, and chemical synthesis, the peptide has the following covalent structure: HOOCCLYGKCRRYOGCSSASCCQR* (O = 4-trans hydroxyproline; * indicates an amidated C-terminus). The disulfide connectivity of the toxin is unrelated to the alpha- or the alphaA-conotoxins, the Conus peptide families that are competitive inhibitors of the nAChR, but shows homology to the mu-conotoxins (which are Na+ channel blockers).  相似文献   
7.
Catalytic hydrolysis of NaBH4 and NH3BH3 has been studied. It was shown that the nature of the support and the active component of the catalyst affect the H2 generation rate. Despite similar sizes of rhodium particles formed on the surface of different supports (γ-Al2O3, TiO2, carbon), their reactivity is different. Rh/TiO2 with low rhodium concentration (1 wt.%) is the most active catalyst both in the hydrolysis of NaBH4 and NH3BH3. The obtained results show that the rhodium chloride interaction with titania determines the reactivity of rhodium particles formed under action of NaBH4 medium. TEM, DRS UV–vis and XPS were used to characterize the catalysts.  相似文献   
8.
In finite-difference micromagnetic simulations, the electric field originated from time variations of magnetic induction is evaluated by means of a discrete version of Faraday's law. The electric field can be then calculated as the convolution of a tensor and the time derivative of the magnetic induction. This paper presents an analytical expression for the tensor. The paper also reports on a quantitative test of the tensor that simulates the electric field of an oscillating magnetic point dipole.  相似文献   
9.
Photocatalytic ozonation (1O3 + VUV + TiO2), ozonation (O3), catalytic ozonation (O3 + TiO2), ozone photolysis (O3 + VUV), photocatalysis (TiO2 + VUV) and photolysis (VUV) have been compared in terms of formation of intermediates, extent of, mineralization (TOC, COD, chloride, nitrate) and kinetics in the aqueous treatment of three phenols (phenol, p‐chlorophenol and p‐nitrophenol). In all cases, photocatalytic ozonation led to lower degradation times for chemical oxygen demand and total organic carbon removal. Intermediates formed were similar in the different oxidation systems with some exceptions. They can be classified into three different types: polyphenols (resorcinol, catechol, hydroquinone), unsaturated carboxylic acids (maleic and fumaric acids) and saturated carboxylic acids (glyoxylic, formic and oxalic acids). First order kinetic equations have been checked for the oxidation processes studied in the case of the parent compound. Rate constants of these systems have also been calculated. Copyright © 2005 Society of Chemical Industry  相似文献   
10.
Two hundred twenty-eight patients with successful coronary stent implantation were randomized either to protamine administration and femoral sheath removal (group I, n = 117) or no heparin neutralization and delayed sheath removal (group II, n = 111). The hospital stay after treatment was shorter in patients receiving protamine; therefore, protamine use for neutralizing circulating heparin may be safely administered immediately after stent implantation.  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