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   2746篇
  免费   75篇
  国内免费   4篇
电工技术   25篇
化学工业   524篇
金属工艺   53篇
机械仪表   41篇
建筑科学   115篇
矿业工程   6篇
能源动力   38篇
轻工业   253篇
水利工程   21篇
石油天然气   3篇
无线电   184篇
一般工业技术   429篇
冶金工业   660篇
原子能技术   30篇
自动化技术   443篇
  2023年   26篇
  2022年   32篇
  2021年   46篇
  2020年   41篇
  2019年   41篇
  2018年   67篇
  2017年   60篇
  2016年   62篇
  2015年   46篇
  2014年   58篇
  2013年   139篇
  2012年   115篇
  2011年   152篇
  2010年   121篇
  2009年   94篇
  2008年   127篇
  2007年   111篇
  2006年   94篇
  2005年   98篇
  2004年   93篇
  2003年   74篇
  2002年   65篇
  2001年   54篇
  2000年   39篇
  1999年   46篇
  1998年   127篇
  1997年   78篇
  1996年   76篇
  1995年   46篇
  1994年   59篇
  1993年   46篇
  1992年   39篇
  1991年   29篇
  1990年   27篇
  1989年   31篇
  1988年   19篇
  1987年   24篇
  1986年   20篇
  1985年   26篇
  1984年   26篇
  1983年   24篇
  1982年   30篇
  1981年   22篇
  1980年   16篇
  1979年   29篇
  1978年   11篇
  1977年   13篇
  1976年   24篇
  1975年   12篇
  1974年   9篇
排序方式: 共有2825条查询结果,搜索用时 8 毫秒
1.
Thirty patients who had undergone either a right or left unilateral temporal lobectomy (14 RTL; 16 LTL) and 16 control participants were tested on a computerized human analogue of the Morris Water Maze. The procedure was designed to compare allocentric and egocentric spatial memory. In the allocentric condition, participants searched for a target location on the screen, guided by object cues. Between trials, participants had to walk around the screen, which disrupted egocentric memory representation. In the egocentric condition, participants remained in the same position, but the object cues were shifted between searches to prevent them from using allocentric memory. Only the RTL group was impaired on the allocentric condition, and neither the LTL nor RTL group was impaired on additional tests of spatial working memory or spatial manipulation. The results support the notion that the right anterior temporal lobe stores long-term allocentric spatial memories. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
2.
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   
3.
A series of studies of top European and other firms has revealed patterns of design management associated with commercial success. Firms that invest resources and professional expertise in product and industrial design in traditional and new industries have been commercially more successful than firms that pay less attention to these aspects of design. As an industry matures there is a shift in emphasis from design associated with technological innovation, to designs supporting technical improvements, and then to supporting user needs, fashion and product variants. These issues are illustrated through the history of the evolution of the bicycle.  相似文献   
4.
Action calculi, which generalise process calculi such as Petri nets, π-calculusand ambient calculus, have been presented in terms of action graphs. We here offer linear action graphs as a primitive basis for action calculi. This paper presents the category of embeddings of undirected linear action graphs without nesting, using a novel form of graphical reasoning which simplifies some otherwise complex manipulations in regular algebra. The results are adapted in a few lines to directed graphs. This work is part of a long-term search for a uniform behavioural theory for process calculi. Received October 2000 / Accepted in revised form April 2001  相似文献   
5.
A model of the pathways controlling the size of the human pupil is presented. Computer simulation of this model demonstrates the role played by each of the elements in the pupil pathways. Simulations of the effects of drugs and a few common abnormalities in the system also help to illustrate the workings of the internal processes. Computer models of this type can be used as teaching aids or as tools for testing of hypotheses regarding the system.  相似文献   
6.
On the basis of the behavioral approach system (BAS) dysregulation theory of bipolar disorder, this study examined the relation between occurrence of a BAS activation-relevant life event--goal striving--and onset of hypomanic and depressive episodes and symptoms. In particular, the authors examined the relation between preparing for and completing final exams (a goal-striving event) and onset of bipolar spectrum episodes and symptoms in college students with bipolar II disorder or cyclothymia (i.e., "soft" bipolar spectrum conditions). One hundred fifty-nine individuals with either a bipolar spectrum disorder (n=68) or no major affective psychopathology (controls; n=91) were further classified on the basis of whether they were college students (i.e., completed final exams). Consistent with the BAS dysregulation theory, preparing for and completing final exams was associated with an increase in hypomanic but not depressive episodes and symptoms in individuals with a soft bipolar spectrum diagnosis. Furthermore, self-reported BAS sensitivity moderated the presence of certain hypomanic symptoms during final exams. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
7.
We studied the effect of premedication (1 microgram/kg fentanyl and 0.04 mg/kg midazolam 5 min before induction of anesthesia) on airway reactivity and hemodynamic stability during inhaled induction using desflurane in 10 ambulatory surgical patients. Eight patients who were anesthetized without premedication served as the controls. Induction and emergence were rapid and unaffected by premedication. End-tidal and inspired concentrations of desflurane at loss of consciousness were significantly reduced by premedication (10.1% end-tidal/14.1% inspired, no premedication, vs. 5.3% end-tidal/8.9% inspired, premedication). Airway irritability was markedly attenuated by premedication (100% no premedication versus 30% premedicated), as was apnea (37.5% no premedication versus 0% premedicated). We observed an increase in mean arterial blood pressure and heart rate after loss of consciousness (mean arterial pressure 103 vs 121 mm Hg, heart rate 73 vs 100 bpm) in the unpremedicated patients, whereas both groups demonstrated a decrease in mean arterial blood pressure with no change in heart rate when baseline values were compared to those at incision (103 vs 74 mm Hg, no premedication, 99 vs 81 mm Hg premedicated). Patient acceptability was satisfactory and unchanged by premedication. We recommend the use of such premedication when desflurane is used during the induction of anesthesia.  相似文献   
8.
Two important elements in problem solving are the abilities to encode relevant task features and to combine multiple actions to achieve the goal. The authors investigated these 2 elements in a task in which gorillas (Gorilla gorilla) and orangutans (Pongo pygmaeus) had to use a tool to retrieve an out-of-reach reward. Subjects were able to select tools of an appropriate length to reach the reward even when the position of the reward and tools were not simultaneously visible. When presented with tools that were too short to retrieve the reward, subjects were more likely to refuse to use them than when tools were the appropriate length. Subjects were proficient at using tools in sequence to retrieve the reward. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
9.
10.
A family of energy/economic/environmental (E3) models is presented as a mechanism for analysing national policy issues. The family consists of discrete models which are designed to be run in an integrated manner. The outputs of certain models provide the inputs to the next. This structure allows the analyst to readily incorporate an understanding of regional factors such as local energy prices, concerns over air quality, water availability, or attitudes towards construction of new energy facilities, into national assessments of energy policies. This paper reviews the analytic framework within which energy policy issues are currently addressed. The initial family of E3 models is described with the emphasis on the data linkages and feedback which are provided when these models are run sequentially. The ongoing MITRE research programme with the E3 family of models is presented and plans and opportunities for future work are outlined.  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