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   52795篇
  免费   3341篇
  国内免费   67篇
电工技术   1730篇
综合类   431篇
化学工业   15362篇
金属工艺   969篇
机械仪表   1111篇
建筑科学   2595篇
矿业工程   278篇
能源动力   1145篇
轻工业   4572篇
水利工程   542篇
石油天然气   185篇
武器工业   5篇
无线电   2799篇
一般工业技术   8916篇
冶金工业   6738篇
原子能技术   291篇
自动化技术   8534篇
  2023年   815篇
  2022年   726篇
  2021年   1305篇
  2020年   1097篇
  2019年   1158篇
  2018年   1287篇
  2017年   1062篇
  2016年   1401篇
  2015年   1494篇
  2014年   1814篇
  2013年   3701篇
  2012年   2181篇
  2011年   2476篇
  2010年   2380篇
  2009年   2409篇
  2008年   2188篇
  2007年   2136篇
  2006年   1854篇
  2005年   1698篇
  2004年   1385篇
  2003年   1322篇
  2002年   1156篇
  2001年   809篇
  2000年   611篇
  1999年   683篇
  1998年   759篇
  1997年   705篇
  1996年   742篇
  1995年   752篇
  1994年   680篇
  1993年   728篇
  1992年   650篇
  1991年   407篇
  1990年   569篇
  1989年   560篇
  1988年   456篇
  1987年   513篇
  1986年   489篇
  1985年   582篇
  1984年   583篇
  1983年   493篇
  1982年   448篇
  1981年   484篇
  1980年   434篇
  1979年   438篇
  1978年   365篇
  1977年   373篇
  1975年   396篇
  1974年   361篇
  1973年   529篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
Six measures of divergent thinking were administered to 825 men ranging in age from 17 to 101 over the period from 1959 to 1972; repeat administrations were given to a subset of 278 men after a 6-year interval. Cross-sectional analyses showed curvilinear trends, with an increase in scores for men under 40 and a decline thereafter. Repeated measures analyses on subjects initially aged 33 to 74 generally replicated this finding, whereas cross-sequential analyses suggested a decline for all cohorts tested at a later time. Additional analyses suggested that not all of the decline could be attributed to reduced speed of response production. These longitudinal findings confirm earlier cross-sectional reports of decline in divergent thinking abilities with age. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
92.
93.
94.
Whether tolerance develops to the "anorexia" induced by haloperidol (HAL) was determined. Rats were given HAL (2.5 or 5 mg/kg) either before or after access to milk for 53 days. Controls were given injections of saline. On Day 54, when all groups received pretest injections of the drug, only rats previously given posttest injections of HAL were tolerant. The absence of tolerance in rats previously given pretest injections suggests that tolerance is suppressed when rats are given access to food in the drugged state. It is concluded that tolerance develops to HAL as a result of pharmacological exposure but is suppressed by the "anhedonic" effect of the drug. The relevance of these findings to the role of reinforcement in behavioral tolerance is briefly discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
95.
A method is described which produces guaranteed bounds for a solution of the generalized complex eigenproblem. The method extends a similar approach for general systems of nonlinear equations to the special case of complex pencils, where under weaker assumptions stronger assertions can be proved.  相似文献   
96.
97.
The morphology of surfaces of several ceramic materials has been examined using transmission electron microscopy. The approach used was to prepare a sample for examination in the microscope, carefully clean it, and then heat-treat it. In the case of the oxides studied (alumina and spinel) the samples were heated in air; the non-oxides (α-SiC and β -SiC) were annealed under vacuum. The morphology in all but one case was such that the surface faceted parallel to the nearest low-index plane to give well-defined terraces; these were separated by ledges which also tended to facet parallel to the traces of low-index planes. The exception was the {1100} alumina surface, which appears to be unstable in air at temperatures close to 1400°C. A computer program using a multislice approach was used to estimate the height of the steps on the (0001) surface; the step heights appear to be multiples of the c lattice parameter. A reconstruction of this surface as a result of this heat treatment is also proposed.  相似文献   
98.
Editorial     
David Grimsrud 《Indoor air》1996,6(3):149-150
  相似文献   
99.
The Santa Amalia building in Barcelona is a block of six flats incorporating a duct by which ligth is sent to the kitchens - previously without natural ligthing- and also allows natural ventilation. Moreover, the passive solar gains obtained from the extensive glazed surfaces and the conservation of internal heat gains, along with a high degree of isulation, give energy saving of 68% for heating.  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