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   2097篇
  免费   108篇
  国内免费   1篇
电工技术   13篇
化学工业   424篇
金属工艺   17篇
机械仪表   31篇
建筑科学   94篇
矿业工程   7篇
能源动力   31篇
轻工业   296篇
水利工程   14篇
石油天然气   4篇
无线电   96篇
一般工业技术   250篇
冶金工业   590篇
原子能技术   5篇
自动化技术   334篇
  2024年   9篇
  2023年   22篇
  2022年   74篇
  2021年   91篇
  2020年   42篇
  2019年   47篇
  2018年   68篇
  2017年   72篇
  2016年   70篇
  2015年   48篇
  2014年   71篇
  2013年   109篇
  2012年   122篇
  2011年   93篇
  2010年   91篇
  2009年   89篇
  2008年   105篇
  2007年   72篇
  2006年   48篇
  2005年   44篇
  2004年   46篇
  2003年   42篇
  2002年   49篇
  2001年   28篇
  2000年   18篇
  1999年   25篇
  1998年   151篇
  1997年   93篇
  1996年   54篇
  1995年   40篇
  1994年   33篇
  1993年   29篇
  1992年   19篇
  1991年   9篇
  1990年   13篇
  1989年   11篇
  1988年   12篇
  1987年   14篇
  1986年   10篇
  1985年   10篇
  1984年   14篇
  1983年   12篇
  1982年   6篇
  1981年   8篇
  1979年   6篇
  1978年   7篇
  1977年   9篇
  1976年   11篇
  1975年   7篇
  1974年   6篇
排序方式: 共有2206条查询结果,搜索用时 0 毫秒
1.
One of the goals of computational chemistry is the automated de novo design of bioactive molecules. Despite significant progress in computational approaches to ligand design and efficient evaluation of binding energy, novel procedures for ligand design are required. Evolutionary computation provides a new approach to this design issue. This paper presents an automated methodology for computer-aided peptide design based on evolutionary algorithms. It provides an automatic tool for peptide de novo design, based on protein surface patches defined by user. Regarding the restrictive constrains of this problem a special emphasis has been made on the design of the evolutionary algorithms implemented.  相似文献   
2.
We consider the switchbox routing problem of two-terminal nets in the case when all thek nets lie on two adjacent sides of the rectangle. Our routing model is the standard two-layer model. We develop an optimal algorithm that routes all the nets whenever a routing exists. The routing obtained uses the fewest possible number of vias. A more general version of this problem (adjacent staircase) is also optimally solved.This research was supported in part by NSA Contract No. MDA-904-85H-0015, NSF Grant No. DCR-86-00378, and by NSF Engineering Research Centers Program NSFD CDR 88003012.  相似文献   
3.
The TELEMAC project brings new methodologies from the Information and Science Technologies field to the world of water treatment. TELEMAC offers an advanced remote management system which adapts to most of the anaerobic wastewater treatment plants that do not benefit from a local expert in wastewater treatment. The TELEMAC system takes advantage of new sensors to better monitor the process dynamics and to run automatic controllers that stabilise the treatment plant, meet the depollution requirements and provide a biogas quality suitable for cogeneration. If the automatic system detects a failure which cannot be solved automatically or locally by a technician, then an expert from the TELEMAC Control Centre is contacted via the internet and manages the problem.  相似文献   
4.
Four hundred forty-six patients with Tourette Syndrome (TS) and/or their parents completed a 52-item self-report survey about vocal and motor tics, and the frequency of associated co-morbid conditions of aggression, obsessions and compulsions, attentional problems, sleep disturbance, mood disturbance, anxiety, and self-mutilative behaviours which have been frequently reported in the literature on TS. Respondents also responded to an open-ended question regarding the most disabling aspects of TS. Results were analyzed within two age groups; under 18 years of age (N = 245) and 18 years of age or older (N = 177). Tics and associated conditions were the most frequently reported disabling aspect by both age groups. Subjects under age 18, however, reported significantly more frequent problems with hyperactivity, temper control, aggressive behaviours and sleepwalking than adults with TS.  相似文献   
5.
6.
7.
Manual responses can be defined by differing response parameters. Any of them may generate a Simon effect. For all those response parameters, the same implementation of the Simon effect (in terms of subserving mechanism) is assumed. In 3 experiments, subjects had to respond with either fingers or sticks. Temporal properties of the Simon effect changed with response parameters relevant in a task. The Simon effect for manual responses decayed. For stick responses, in which the action goal differed from the anatomical mapping of the acting hand, a sustained Simon effect was observed. However, if the action goal for stick responses was not instrumental for selecting the correct response, the Simon effect decayed. The findings are consistent with the notion of different mechanisms involved in generating a Simon effect. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
8.
Thyroid hormone plays a key role in trophic events during development of the central nervous system. In spite of neurological and psychiatric symptoms associated with adult hypothyroidism, the role of thyroid hormone in mature brain function is less clear. In this paper we investigated the effect of thyroid status on kainic acid-induced up-regulation of mRNAs for members of the nerve growth factor family and related receptors in adult male rats by means of in situ hybridization. We found that in hypothyroid rats there is a dramatic attenuation of the kainic acid-induced up-regulation of mRNA levels for nerve growth factor, brain-derived neurotrophic factor and tyrosine kinase trkB in euthyroid rats. A trend to reduced c-fos mRNA up-regulation, which did not reach significance, was also found, whereas the increase in c-jun mRNA after kainic acid was similar in eu-, hypo- and hyperthyroid rats. These data indicate a severe impairment of the regulation of neurotrophin synthesis after excitotoxin administration in the hippocampus during adult hypothyroidism. Possible roles of thyroid hormone in molecular, biochemical and metabolic mechanisms of this defect are discussed.  相似文献   
9.
Contends, on the basis of posited social-role theory of gender and helping, that the male gender role fosters helping that is heroic and chivalrous, whereas the female gender role fosters helping that is nurturant and caring. In social psychological studies, helping behavior has mainly been examined in the context of short-term encounters with strangers. This focus has tended to exclude from the research literature those helping behaviors prescribed by the female gender role, because they are displayed primarily in long-term, close relationships. In contrast, the helping behaviors prescribed by the male gender role have been generously represented in research findings because they are displayed in relationships with strangers as well as in close relationships. Results from a meta-analytic review of sex differences in 172 studies (appended) in helping behavior indicate that in general men helped more than women and women received more help than men. Nevertheless, sex differences in helping were inconsistent across studies and were successfully predicted by various attributes of the studies and the helping behaviors. (96 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
10.
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