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   24695篇
  免费   958篇
  国内免费   33篇
电工技术   329篇
综合类   38篇
化学工业   5655篇
金属工艺   380篇
机械仪表   476篇
建筑科学   1307篇
矿业工程   100篇
能源动力   621篇
轻工业   1888篇
水利工程   233篇
石油天然气   71篇
无线电   1818篇
一般工业技术   4503篇
冶金工业   4531篇
原子能技术   196篇
自动化技术   3540篇
  2023年   214篇
  2022年   359篇
  2021年   567篇
  2020年   338篇
  2019年   431篇
  2018年   535篇
  2017年   463篇
  2016年   632篇
  2015年   558篇
  2014年   749篇
  2013年   1419篇
  2012年   1161篇
  2011年   1510篇
  2010年   1075篇
  2009年   1014篇
  2008年   1147篇
  2007年   1085篇
  2006年   944篇
  2005年   761篇
  2004年   745篇
  2003年   659篇
  2002年   563篇
  2001年   428篇
  2000年   362篇
  1999年   402篇
  1998年   752篇
  1997年   553篇
  1996年   442篇
  1995年   411篇
  1994年   377篇
  1993年   362篇
  1992年   270篇
  1991年   195篇
  1990年   268篇
  1989年   260篇
  1988年   215篇
  1987年   224篇
  1986年   226篇
  1985年   265篇
  1984年   224篇
  1983年   223篇
  1982年   207篇
  1981年   194篇
  1980年   168篇
  1979年   193篇
  1978年   164篇
  1977年   185篇
  1976年   231篇
  1975年   160篇
  1974年   123篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
201.
Two experiments were conducted in which participants looked at photographs (Experiment 1, n?=?129) or slides (Experiment 2, n?=?90) of people engaging in positive or negative facial expressions. Participants attempted to communicate these facial expressions as accurately as they could to a video camera while viewing themselves in a mirror or without viewing themselves in a mirror. Participants in a control group maintained neutral facial expressions. Participants experienced increased positive moods when they engaged in positive facial expressions and decreased positive moods when they engaged in negative facial expressions. These effects were enhanced when participants viewed themselves in a mirror. The effects of facial expressions on positive affect were stronger for participants with high private self-consciousness. Results were integrated with research identifying individuals who are responsive to self-produced versus situational cues and with theory and research on self-awareness. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
202.
Based on a rearrangement inequality by Hardy, Littlewood, and Polya, we define two-operator algebras for independent random variables. These algebras are called Huffman algebras since the Huffman algorithm on these algebras produces an optimal binary tree that minimizes the weighted lengths of leaves. Many examples of such algebras are given. For the case with random weights of the leaves, we prove the optimality of the tree constructed by the power-of-2 rule, i.e., the Huffman algorithm assuming identical weights, when the weights of the leaves are independent and identically distributed.  相似文献   
203.
204.
205.
The anticipated, dramatic shift in the demographics of European societies over the next half a century begs many questions about the state of relations between generations. Papers and speculations portraying a world in which the elderly rule through parliamentary majorities, preventing reductions in pensions and ??enslaving?? the working population are surprisingly common. Existing literature on these hypotheses focus on the policy preference differences between the young and the old with evidence mixed as to the accuracy of these predictions. This paper aims to build on this debate by looking at the effects that the dependency ratio has on intergenerational relations. By using a multilevel methodology and data from the 2008 European Social Survey, the effect of demographic structure can be observed on the individual level. Yet whilst evidence is found of decreasing legitimacy of welfare for the elderly, this paper argues that this does not point to increasing intergenerational conflict in Europe.  相似文献   
206.
The kaolinite-mullite reaction series in single crystal kaolinite has been characterized by transmission electron microscopy. The exotherm observed at 980° C is attributed to the formation of a spinel phase. Mullite crystallites have also been observed with the spinel phase and both phases have a composition near that of 32 mullite. Subsequent heat treatment leads to the growth of mullite crystallites on the original kaolinite plates with the c-axis perpendicular to the plate.  相似文献   
207.
208.
The Journal of Supercomputing - Scientific application codes are often long-running time- and energy-consuming parallel codes, and the tuning of these methods towards the characteristics of a...  相似文献   
209.
Requirements Engineering - To reduce program risks, engineering methods capitalizing on modeling and machine assistance have been extensively investigated within systems engineering (and more...  相似文献   
210.
In spite of great improvements in early diagnosis and interventions, most children diagnosed with autism spectrum disorders (ASD) are unlikely to live independently when they reach adulthood. We have been conducting research on novel computer-based interventions with the goal of promoting social skills. Working with 26 children with ASD, their teachers, and other stakeholders, we have iteratively developed a set of activities based on applications that run on multitouch tablets. Our observations suggest these activities increased pro-social behaviors such as collaboration and coordination, augmented appreciation for social activities, and provided children with novel forms of expression.  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