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   37688篇
  免费   1588篇
  国内免费   43篇
电工技术   488篇
综合类   71篇
化学工业   8408篇
金属工艺   719篇
机械仪表   679篇
建筑科学   2306篇
矿业工程   89篇
能源动力   994篇
轻工业   3436篇
水利工程   329篇
石油天然气   180篇
武器工业   3篇
无线电   2559篇
一般工业技术   6869篇
冶金工业   5863篇
原子能技术   256篇
自动化技术   6070篇
  2023年   297篇
  2022年   494篇
  2021年   771篇
  2020年   561篇
  2019年   641篇
  2018年   790篇
  2017年   775篇
  2016年   1010篇
  2015年   937篇
  2014年   1178篇
  2013年   2171篇
  2012年   1886篇
  2011年   2361篇
  2010年   1718篇
  2009年   1675篇
  2008年   1970篇
  2007年   1886篇
  2006年   1644篇
  2005年   1424篇
  2004年   1277篇
  2003年   1071篇
  2002年   1044篇
  2001年   651篇
  2000年   627篇
  1999年   612篇
  1998年   585篇
  1997年   536篇
  1996年   545篇
  1995年   516篇
  1994年   478篇
  1993年   513篇
  1992年   467篇
  1991年   286篇
  1990年   385篇
  1989年   381篇
  1988年   308篇
  1987年   363篇
  1986年   346篇
  1985年   379篇
  1984年   334篇
  1983年   320篇
  1982年   304篇
  1981年   283篇
  1980年   250篇
  1979年   254篇
  1978年   219篇
  1977年   192篇
  1976年   193篇
  1975年   193篇
  1974年   179篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
Michael Brady 《Energy》1985,10(10):1113-1118
Current energy policies have severely eroded the earth's natural atmospheric waste-receptor capacity. Present acid rain concentrations may require a switch to an alternative energy-resource emphasis. This policy recommendation follows directly from a deductive control theory demonstration which shows that, if fossil-fuel use is continued at present rates, then there is an ever-increasing risk of a man-made environmental crisis of uncertain nature and scope.  相似文献   
22.
To eliminate potential "backward" priming effects, S. Glucksberg et al (see record 1986-29080-001) introduced a variant of the cross-modal lexical priming task in which subjects made lexical decisions to nonword targets that were modeled on a word related to either the contextually biased or unbiased sense of an ambiguous word. Lexical decisions to nonwords were longer than controls only when the nonword was related to the contextually biased sense of the ambiguous word, leading Glucksberg et al to conclude that context does constrain lexical access and that the multiple access pattern observed in previous studies was probably an artifact of backward priming. We did not find nonword interference when the nonword targets used by Glucksberg et al were preceded by semantically related ambiguous or unambiguous word primes. However, we did replicate their sentence context results when the ambiguous words were removed from the sentences. We conclude that the interference obtained by Glucksberg et al is due to postlexical judgments of the congruence of the sentence context and the target, not to context constraining lexical access. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
23.
This article describes a circuit model for infinitesimally thin inductive strips centered in homogeneous finline. The model is valid for 0.1 ≤ W/b ≤ 1.0, 0.01 ≤ T/a, and 0.4 ≤ b/a ≤ 0.5 when frequency is in the normal operating band for the rectangular waveguide shield. The error is less than 2.5%.  相似文献   
24.
The University of Maryland's Computer Aided Life Cycle Engineering (CALCE) research effort is aimed at developing techniques for design, analysis, prediction, and optimization of electronics with respect to a variety of design goals. Performance, producibility, reliability, maintainability, life-cycle cost, safety, etc., are the design criteria which are being integrated through the application of interactive heuristic and algorithmic design optimization techniques. The University of Maryland Reliability and Maintainability Computer-Aided Design (RAMCAD) research is CALCE and is focused on second- and third-level electronic package design with respect to interfacing thermal, mechanical, and reliability analysis. The goal is to make reliability and maintainability an integral, real-time, and upfront part of the design process, such that the need to resubmit designs will be eliminated. The motivation behind this project was the fact that schedule constraints are often compromising the effectiveness and efficiency of the design process. To achieve the goal of CALCE/RAMCAD, a cohesive and extensible design environment for analysis and tradeoff tools was developed. A system executive controller that integrates tools for analysis while providing system transparency, design data management, and process management was developed to guide the user through the design process and provide direct access to the design tools. These developments required the integration of computer-aided design (CAD), artificial intelligence (AI), and decision support (DS) techniques. Attention to human factors and the use of interactive graphics were also instrumental in the development.  相似文献   
25.
Government energy pricing policies have multiple and often conflicting objectives: economic efficiency, government revenues (for both parastatal supply companies and the treasury), maintenance or improvement of income distribution, promotion of particular sectors (such as industrial exporters and local resource development) demand management and security of supply. It is important to examine the impacts on and the trade-offs between these objectives resulting from alternative policies in order to assist in policy selection. This article discusses the more important objectives and their conflicts and outlines an approach for the quantitative examination of alternative policies.  相似文献   
26.
27.
The objective of the present study was to generate submicrometer calcium hydroxide aerosols and to investigate the effectiveness of such aerosols in sulfur capture. The effectiveness of SO2 removal by Ca(OH)2 aerosol has been investigated in an isothermal reactor. Ca(OH) 2 aerosol was generated by a novel fluidizer system in which submicrometer-sized powders were entrained in gases. SO2 was added to this aerosol to a concentration of 2000 ppm. The aerosol-SO2 mixture was heated to 550°C-750°C in an isothermal tube reactor. The SO2 removal efficiency, which varied from 20% to 70%, was determined to be a function of the aerosol concentration, reactor temperature and residence time. The fraction of aerosol reacted was not affected strongly by the aerosol concentration. The reaction kinetics were determined from the experimental data using a simple analytical model in which the rate is first order in both SO2 and calcium hydroxide aerosol concentrations.  相似文献   
28.
EFFECTOFTHERATIOTh/UONTLDATINGACCURACY¥P.L.Leung(梁宝鎏);MichaelJ.Stokes(DepartmentofPhysicsandMaterialsScience,CityPolytechnico...  相似文献   
29.
30.
Explored the construct validity of transactional analysis (TA) ego state concepts. Ego states are defined as coherent systems of thoughts, feelings, and behaviors. 65 university students seeking therapy and 95 university students not receiving therapy completed the Adjective Checklist (ACL) and the Brief Symptom Inventory (BSI). Ego state scores from the ACL correlated with BSI psychological distress in predicted directions. Four of the 5 TA ego state scores differentiated Ss seeking therapy from Ss not seeking therapy. Furthermore, ego state scores changed over the course of therapy, indicating a reduction of distress. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  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