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   26470篇
  免费   4182篇
  国内免费   2714篇
电工技术   1269篇
技术理论   1篇
综合类   2046篇
化学工业   2161篇
金属工艺   840篇
机械仪表   1173篇
建筑科学   4307篇
矿业工程   1973篇
能源动力   701篇
轻工业   725篇
水利工程   864篇
石油天然气   1854篇
武器工业   112篇
无线电   1758篇
一般工业技术   2302篇
冶金工业   2446篇
原子能技术   135篇
自动化技术   8699篇
  2024年   417篇
  2023年   1294篇
  2022年   2240篇
  2021年   2146篇
  2020年   1825篇
  2019年   1284篇
  2018年   844篇
  2017年   842篇
  2016年   793篇
  2015年   862篇
  2014年   1408篇
  2013年   1496篇
  2012年   1431篇
  2011年   1725篇
  2010年   1365篇
  2009年   1441篇
  2008年   1280篇
  2007年   1467篇
  2006年   1369篇
  2005年   1239篇
  2004年   931篇
  2003年   858篇
  2002年   723篇
  2001年   569篇
  2000年   526篇
  1999年   476篇
  1998年   508篇
  1997年   311篇
  1996年   262篇
  1995年   180篇
  1994年   181篇
  1993年   140篇
  1992年   133篇
  1991年   121篇
  1990年   118篇
  1989年   67篇
  1988年   64篇
  1987年   49篇
  1986年   68篇
  1985年   78篇
  1984年   51篇
  1983年   47篇
  1982年   31篇
  1981年   17篇
  1980年   23篇
  1979年   17篇
  1978年   12篇
  1977年   8篇
  1975年   5篇
  1959年   5篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
岩石圈深部探测与青藏高原研究   总被引:2,自引:0,他引:2  
论述了岩石圈深部探测的作用和重大意义,它是一项国土基础地质情况的调查,可以为找矿预测、地震预报、能源开发及大陆动力学研究等多目标服务,是21世纪中国区域地质调查的重要内容,是一项伟大的科学工程;美国、前苏联和中国此前均已作了大量工作,但是有待深化和进一步开展调查;简要介绍了青藏高原近些年来开展深部调查的情况和取得的主要最新成果。  相似文献   
92.
马开连 《齐鲁石油化工》2003,31(2):108-109,118
论述了几种三相交流异步电动机的起动方式及其优缺点 ,介绍了新型的电子软启动方式在我厂深井泵电动机上的应用及取得的运行效果 ,为电动机软启动方式在工矿企业中的应用提供了应用经验。  相似文献   
93.
Professional psychologists are increasingly likely to encounter opportunities to work with patients and families facing end-of-life issues. Psychologists can provide psychological assessment, intervention for patients and families, consultation with and support of health care team members, grief therapy, and program development and evaluation. Psychological services are useful for healthy individuals who wish to make thoughtful plans about their own future care, patients with life-limiting illnesses, families stressed by providing end-of-life care, bereaved individuals, and health care providers who face issues of burnout and strain. Several challenges for psychologists working in end-of-life care are noted, including training, development of clear roles, and reimbursement. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
94.
The need for better protecting our vital infrastructure from being damaged or destroyed has received increased attention since the terrorist attacks on September 11, 2001. The tragedy of having thousands of innocent people die before the eyes of an entire nation awakened people to the reality of “managed” attacks of unthinkable magnitudes. However, tragedies of a smaller scale are a daily occurrence but accepted as “collateral damage” of work in an unsafe environment. This paper presents a cost-benefit analysis to address the question of how much money should be spent in protecting underground utilities from damage. During the study of an actual incident it was found that the total costs of such accidents are vastly underreported because only costs for emergency responses and repair are tallied up. This paper makes the case that a comprehensive approach for assessing the total economic impact of such incidents on the public, business, and government is the critical stepping stone to a mathematical optimization of expenditure for damage prevention. In addition, the reader will quickly realize that the use of the presented optimization model provides theoretical underpinning for the engineering profession in its effort to better protect our critical infrastructure from terrorist attacks.  相似文献   
95.
This paper reports how the study of formal logical reasoning provides insight into more everyday types of reasoning, such as that involved in language comprehension. Both of these types of cognition are thought to involve the use of mental models, and so it is reasonable to think that the cognitive operations needed for formal logical reasoning would be involved in everyday reasoning as well. We focused on three aspects of formal reasoning: (a) the integration of information into a common mental model, (b) the drawing of inferences, and (c) the coordination of alternative possibilities. We were able to show that the integration and inference components were related to narrative comprehension processes, but the coordination of alternative models was not. Thus, there is evidence for some overlap in the mental processes used in formal and everyday reasoning. This further justifies the study of formal logical reasoning as a window into certain types of everyday reasoning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
96.
97.
 In this paper, a new approach for powder cold compaction simulations is presented. A density-dependent plastic model within the framework of finite strain multiplicative hyperelastoplasticity is used to describe the highly nonlinear material behaviour; the Coulomb dry friction model is used to capture friction effects at die-powder contact; and an Arbitrary Lagrangian–Eulerian (ALE) formulation is used to avoid the (usual) excessive distortion of Lagrangian meshes caused by large mass fluxes. Several representative examples, involving structured and unstructured meshes are simulated. The results obtained agree with the experimental data and other numerical results reported in the literature. It is shown that, contrary to other Lagrangian and adaptive h-remeshing approaches recently reported for this type of problems, the present approach verifies the mass conservation principle with very low relative errors (less than 1% in all ALE examples and exactly in the pure Lagrangian examples). Moreover, thanks to the use of an ALE formulation and in contrast with other simulations, the presented density distributions do not present spurious oscillations. Received: 20 March 2002 / Accepted: 15 October 2002 The partial financial support of the Ministerio de Ciencia y Tecnología (grant number DPI 2001-2204) is gratefully acknowledged.  相似文献   
98.
This study is concerned with the assessment of risk for major construction activities. Risk has been defined as a measure of the probability, the severity, and the exposure of all hazards of an activity. A risk assessor model (RAM) was developed and computerized to determine the risk associated with a particular activity and the justification factor for a proposed remedy. Knowing the value of risk would help contractors identify the high risk of major construction activities and would enable them to allocate safety precautions in a more efficient manner.  相似文献   
99.
分析了上海兰心影剧院地下室深井修建后出现渗漏的原因,介绍了堵漏工程采用的防水材料和施工方法。  相似文献   
100.
生产装置在线模拟与优化技术的应用   总被引:5,自引:0,他引:5  
概述了以通用软件为基础开发化工生产装置严格在线模拟与优化系统的过程,介绍了在线模型的5个层次及其特点,以合成氨为例说明了在线模型的运行和应用情况。  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