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   243570篇
  免费   2953篇
  国内免费   1243篇
电工技术   4834篇
综合类   264篇
化学工业   35424篇
金属工艺   10861篇
机械仪表   7070篇
建筑科学   6241篇
矿业工程   481篇
能源动力   6281篇
轻工业   24154篇
水利工程   1836篇
石油天然气   1335篇
武器工业   3篇
无线电   31047篇
一般工业技术   44895篇
冶金工业   50128篇
原子能技术   3860篇
自动化技术   19052篇
  2021年   1566篇
  2019年   1428篇
  2018年   2324篇
  2017年   2224篇
  2016年   2448篇
  2015年   1909篇
  2014年   3160篇
  2013年   10799篇
  2012年   5452篇
  2011年   7791篇
  2010年   6287篇
  2009年   6968篇
  2008年   7562篇
  2007年   7663篇
  2006年   7032篇
  2005年   6521篇
  2004年   6246篇
  2003年   6262篇
  2002年   6241篇
  2001年   6373篇
  2000年   5801篇
  1999年   6420篇
  1998年   16572篇
  1997年   11602篇
  1996年   8950篇
  1995年   6689篇
  1994年   5909篇
  1993年   5730篇
  1992年   4051篇
  1991年   3997篇
  1990年   3583篇
  1989年   3506篇
  1988年   3440篇
  1987年   2907篇
  1986年   2843篇
  1985年   3415篇
  1984年   3051篇
  1983年   2743篇
  1982年   2547篇
  1981年   2568篇
  1980年   2430篇
  1979年   2271篇
  1978年   2235篇
  1977年   2810篇
  1976年   4171篇
  1975年   1899篇
  1974年   1795篇
  1973年   1783篇
  1972年   1460篇
  1971年   1317篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Growth hormone (GH) has recently been shown to affect polymorphonuclear neutrophil granulocyte (PMN) function and to be secreted by mononuclear cells, indicating that the hormone may be active in an immunophysiologic network, acting as an endo- or paracrine priming agent. The purpose of the present study was to evaluate the chemotactic responsiveness of canine peripheral PMN in a dog with acromegaly, caused by spontaneous, progesterone-induced hypersecretion of GH and, secondary to this, a seven-fold increase in insulin-like growth factor I (IGF-I). The chemotactic responsiveness towards zymosan-activated serum (ZAS) and leukotriene B4 (LTB4) was evaluated at a time when the dog suffered from acromegaly and again 57 days after corrective surgery (ovariohysterectomy). The experiments showed that PMN from the patient exhibited enhanced chemotactic migration that appeared to be associated with the hypersomatotropic condition as judged from the reversibility of the phenomenon. The glucose intolerance and elevated serum alkaline phosphatase that were observed in the acromegalic dog were also shown to be reversible following surgery.  相似文献   
92.
93.
94.
95.
Studied how 26 senior managers and 47 senior professional technical staff (recently repatriated) of 4 US owned multinational organizations viewed their international posting, specifically with respect to career path satisfaction. Results of satisfaction scales indicate that many Ss felt under-prepared for their international assignment. It is suggested that a comprehensive international employee development program should assess, provide feedback, and coach individuals on career path, culture shock and adjustment, and performance issues prior, during, and on return from the expatriate assignment. Results suggest that opportunities exist for individual and organizational intervention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
96.
An automated gel electrophoresis apparatus, recently available commercially, allows one to follow the band during electrophoresis in real time, and lends itself therefore to an evaluation of bandwidth as a function of migration time (the dispersion coefficient), resolution and band shape. These determinations assume the constancy of band area with migration time and at various gel concentrations. The purpose of the present study was to verify these assumptions. Representative proteins and sodium dodecyl sulfate (SDS)-proteins, either natively fluorescent or fluorescein carboxylate labeled, were found to exhibit band areas which approach constancy as a function of migration time in both agarose and polyacrylamide gel electrophoresis, provided that (i) the protein concentration under the band was low enough to obviate self-quenching of fluorescence; (ii) the separation of the protein of interest from contaminants had progressed sufficiently during the time at which band areas were measured; (iii) the baseline under the peak was sufficiently well defined. However, band areas decrease with increasing gel concentration. Protein peaks exhibited leading and trailing tails. The ratio of the combined tail area to total area appeared to be near-constant at varying migration times. However, that ratio increases with increasing gel concentration. The tail area does not appear to be an artifact of fluorometric detection since it is reproduced upon fluorimetric analysis of the protein eluted from gel slices after electrophoresis. However, it may be due to photochemical destruction under the conditions of repetitive fluorometric peak detection.  相似文献   
97.
98.
99.
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