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   25012篇
  免费   1094篇
  国内免费   56篇
电工技术   321篇
综合类   34篇
化学工业   4941篇
金属工艺   650篇
机械仪表   713篇
建筑科学   1069篇
矿业工程   110篇
能源动力   908篇
轻工业   2201篇
水利工程   192篇
石油天然气   74篇
武器工业   1篇
无线电   2518篇
一般工业技术   4629篇
冶金工业   3886篇
原子能技术   173篇
自动化技术   3742篇
  2023年   191篇
  2022年   261篇
  2021年   524篇
  2020年   390篇
  2019年   420篇
  2018年   546篇
  2017年   555篇
  2016年   623篇
  2015年   527篇
  2014年   808篇
  2013年   1625篇
  2012年   1252篇
  2011年   1629篇
  2010年   1145篇
  2009年   1164篇
  2008年   1296篇
  2007年   1147篇
  2006年   977篇
  2005年   958篇
  2004年   775篇
  2003年   699篇
  2002年   672篇
  2001年   448篇
  2000年   414篇
  1999年   438篇
  1998年   556篇
  1997年   433篇
  1996年   446篇
  1995年   379篇
  1994年   343篇
  1993年   321篇
  1992年   290篇
  1991年   185篇
  1990年   251篇
  1989年   224篇
  1988年   190篇
  1987年   189篇
  1986年   163篇
  1985年   204篇
  1984年   208篇
  1983年   175篇
  1982年   176篇
  1981年   173篇
  1980年   154篇
  1979年   169篇
  1978年   134篇
  1977年   130篇
  1976年   172篇
  1975年   128篇
  1974年   113篇
排序方式: 共有10000条查询结果,搜索用时 531 毫秒
71.
在未来勘探开发中研发的推动作用   总被引:2,自引:1,他引:1  
在过去的20年里,尽管油价和经营环境不断发生着变化,但勘探开发的产量和经济效益持续增长着,科学研究和先进技术起了关键作用。未来的勘探开发将更加依赖于先进的技术和科学的研究开发。 随着变化的经营环境和关键的先进科学技术强有力的结合,出现了新的研发模式和发展趋势。在这里我们  相似文献   
72.
73.
74.
Various high molecular weight copolymers of acrylonitrile and a vinyl comonomer containing an aryl amine, a pyridine, or an aliphatic hydroxyl group were synthesized via slurry polymerization techniques so as to contain from 1 to 15 mol % functional comonomer. The comonomer content was quantitated by ultraviolet absorbance, base titration of acid polymer salts, and/or relative chemical reactivity with trichloro-s-triazine. Thin films were cast from copolymer solutions, coagulated into unsupported ultrafiltration membrances, and characterized with respect to both water permeability and pore size distribution. Analysis by size exclusion chromatography of the membrane permeate of a pool of dextran fractions yielded a continuous distribution curve for membrane pore size over the range 1.5 to 70 nm. The ultrafiltration membranes were used for protein immobilization after appropriate chemical activation. The three distinct types of functional copolymers gave comparable results for α-chymotrypsin, with protein weight loadings of 6–12% and 40–65% retention of enzymatic specific activity.  相似文献   
75.
Friendship affects individual and organizational well-being through direct relations, social positions, and complex network structures. In this study, the authors use longitudinal data from 2 groups of master's of business administration students to increase understanding of how friendship networks develop. The authors propose and test a dynamic model in which attribute similarity facilitates dyadic friendship ties, as well as similar network centrality and social position; early friendship increases later similarity in structural position and centrality; and early structural similarity enhances the likelihood of future friendship. Findings largely supported the model, demonstrating how homophily and early social contacts can jointly shape maturing friendship networks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
76.
Like any other domain of human activity, psychology has its fads and fashions. One consequence of fads is an overconcentration of resources on specific problems or approaches, which leaves other important problems or approaches (holes) underappreciated and understudied. This article is primarily about different factors (such as negativity bias, polarization of positions, focus on internal causes of behavior, dedication to a narrow view of what science is) that result in holes and about explorations of some of these holes that have interested the author. Psychologists should look more in the holes left behind by current enthusiasms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
77.
Learning Organizations in Construction   总被引:1,自引:0,他引:1  
The transformation of organizations from production-oriented entities to proactive learning entities that continuously leverage the knowledge of the workforce is a primary objective of management researchers. This focus has significant relevance to the construction industry where production-related research has predominantly overshadowed organizational development research. As one effort to change this emphasis, the writers present a research effort designed to study current organization learning techniques and technologies fielded by organizations both inside and outside of the construction industry. Through a series of exploratory case studies, the writers developed a maturity model together with the Construction Industry Institute that provides construction organizations with a framework for developing a learning organization culture. The maturity model focuses on learning organization characteristics of leadership, processes and infrastructure, communication/collaboration, education, and culture at the organization, community, and individual levels. This paper introduces the results of that effort including a presentation of the learning organization maturity model, framework application, and the overall characteristics of a learning organization.  相似文献   
78.
79.
80.
Pervasive computing is as much about the user as it is about the technology. So, the Fifth International Conference on Pervasive Computing emphasized desirability rather than just feasibility. Featured themes included user benefits, human-computer interaction, group and social interactions, context awareness, finding and positioning people and objects, and personal privacy.  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