全文获取类型
收费全文 | 64369篇 |
免费 | 9903篇 |
国内免费 | 5521篇 |
专业分类
电工技术 | 4964篇 |
技术理论 | 25篇 |
综合类 | 8077篇 |
化学工业 | 1377篇 |
金属工艺 | 898篇 |
机械仪表 | 3729篇 |
建筑科学 | 4253篇 |
矿业工程 | 1461篇 |
能源动力 | 1756篇 |
轻工业 | 1185篇 |
水利工程 | 1355篇 |
石油天然气 | 1639篇 |
武器工业 | 605篇 |
无线电 | 10350篇 |
一般工业技术 | 2996篇 |
冶金工业 | 1607篇 |
原子能技术 | 158篇 |
自动化技术 | 33358篇 |
出版年
2025年 | 23篇 |
2024年 | 1789篇 |
2023年 | 1753篇 |
2022年 | 2398篇 |
2021年 | 2679篇 |
2020年 | 2655篇 |
2019年 | 2009篇 |
2018年 | 1843篇 |
2017年 | 2149篇 |
2016年 | 2491篇 |
2015年 | 2808篇 |
2014年 | 5272篇 |
2013年 | 4573篇 |
2012年 | 5394篇 |
2011年 | 5422篇 |
2010年 | 3972篇 |
2009年 | 3943篇 |
2008年 | 3911篇 |
2007年 | 4414篇 |
2006年 | 3886篇 |
2005年 | 3247篇 |
2004年 | 2642篇 |
2003年 | 2325篇 |
2002年 | 1603篇 |
2001年 | 1323篇 |
2000年 | 1062篇 |
1999年 | 843篇 |
1998年 | 517篇 |
1997年 | 438篇 |
1996年 | 387篇 |
1995年 | 365篇 |
1994年 | 295篇 |
1993年 | 203篇 |
1992年 | 172篇 |
1991年 | 142篇 |
1990年 | 125篇 |
1989年 | 121篇 |
1988年 | 111篇 |
1987年 | 40篇 |
1986年 | 44篇 |
1985年 | 65篇 |
1984年 | 56篇 |
1983年 | 40篇 |
1982年 | 36篇 |
1981年 | 26篇 |
1980年 | 16篇 |
1979年 | 22篇 |
1977年 | 10篇 |
1976年 | 10篇 |
1975年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Kevin Yale Teichman 《Indoor air》1994,4(3):202-211
Deciding between the different policy approaches available for reducing human exposures to indoor pollutants is an exceptionally complex task. These options can range from waiting until more definitive information is available to enacting regulatory standards, with many variations in between. This paper presents some of the factors policy-makers must consider in establishing indoor air quality policies, and the role researchers should play in ensuring that indoor air policies are based on the best available scientific information. 相似文献
2.
Colin Hines 《Energy Policy》1985,13(2):188-189
This communication illustrates the work of the London Energy and Employment Network. LEEN has the twin aims of promoting a rational energy policy for London and, in the process, generating much needed employment. In cooperation with Hackney, one of Britain's poorest boroughs, LEEN organized Hackney's Cold War — a series of initiatives showing the practical measures, informational back-up and funding sources necessary for a local energy policy. LEEN intends to repeat this project in other London Boroughs, with the eventual aim of helping to persuade central government to adopt a more comprehensive approach to energy conservation nationally. 相似文献
3.
4.
Markus Stolze 《Knowledge》1994,7(4):271-273
System development is strongly influenced by the perspectives used by system developers. Current development methods for knowledge-based systems are based on an information processing perspectives of experts and users which has been criticized by a number of researchers. The paper argues that work-oriented development of knowledge-based systems requires the parallel use of multiple perspectives (including the information processing perspective), and that the use of any single perspective is potentially dangerous. As an example of the importance of using multiple perspectives, thepaper presents the situated action perspective, and shows how it complements the information processing perspective. 相似文献
5.
6.
G. Anandalingam 《Energy Policy》1985,13(4):335-339
This paper begins by examining the most energy-intensive industries and methods by which fuel efficiency can be improved. Next the author analyses the economics of energy conservation using specific case studies drawn from India. It is shown that investing in energy efficiency is more economical Btu per Btu than investing in the enhancement of domestic energy resources. The author also assesses changes in the economics of conservation for private firms when there are government incentives. Finally government policies that can overcome economic and non-economic disincentives for investing in energy conservation are examined. 相似文献
7.
8.
To confirm the reliability of the theory of phase equibria of multicomponent polymer 1/multicomponent polymer 2 systems (i.e. quasi-binary systems) and the method of computer experiment based on this theory (Brit. Polym. J., 23 (1990)285; 23 (1990)299; Polym. Int., 29 (1992)219), could point curves (CPC), two-phase volume ratios ( R ) and critical solution points (CSP) have been determined experimentally for the quasi-binary mixtures of poly(ethylene oxide) (M¯w = 647, M¯w/M¯n = 1.15; M¯w and M¯n, the weight-average and numberaverage molecular weights, respectively) and poly(propylene oxide) (M¯w = 2028, M¯w/M¯n = 1.08; and Mw = 2987, Mw/Mn = 1.13). The hydroxyl end groups of both polymers were methoxylated in advance by the Cooper & Booth method (Polymer, 18 (1977)164). The thermodynamic interaction parameter between both polymers, χ12, and the concentration dependence parameters for the above quasi-binary systems were determined by the method proposed in a previous paper (Brit. Polym. J., 23 (1990)299). CPC, R and CSP values calculated on the basis of the theory are in good agreement with the values determined experimentally. 相似文献
9.
A survey was carried out of past and current Canadian experiences with machine-aided translation (MAT) systems of non-literary texts in one government institution and three industrial settings. Each organization requires a great deal of translation and had conducted several experiments in the use of MAT. The survey supports positive conclusions about the prospects for expanded use of computers in translation.The authors express their thanks to all those who helped in the preparation of this paper. We are particularly grateful to the staff of the translation departments of the organizations mentioned in the paper for their kind cooperation and their willingness to answer our questions: Chantal Delorme ofIBM Canada, Lorraine Desmarais and Mr. Plamondon of Bell Canada, Pierre Tellier of the Department of the Secretary of State, Maria Russo and Raymond Lapointe of the Xerox Corporation. Furthermore we thank Prof. Graeme Hirst for helpful discussion. 相似文献
10.
MARCO SCHAERF 《Computational Intelligence》1991,7(3):154-159
The use of multivalued logics for knowledge representation and nonmonotonic reasoning has often been advocated, in particular within the general framework proposed by Ginsberg in his paper "Multivalued logics: a uniform approach to reasoning in artificial intelligence." His system is based on a multivalued logic with an arbitrary number of truth values classified with respect to two partial orders, a truth order and a knowledge order. This classification is very interesting and gives an intuitive appeal to the framework. In this paper the work by Ginsberg is critically reviewed, pointing out some flaws and ways to overcome them. Moreover, we present some ideas on how to modify the original schema in order to obtain a more semantically well-founded framework.
L'utilisation de la Iogique multivalente pour la représentation des connaissances et le raisonnement non monotone a souvent été préconisée, en particulier à l'intérieur du cadre général proposé par Ginsberg dans son article intitulé〘 Multivalued logics: a uniform approach to reasoning in artificial intelligence 〙 Son système est basé sur une logique multivalente comportant un nombre arbitraire de valeurs de vérité classées selon deux ordres partiels: un ordre de vérité et un ordre de connaissances. Cette classification est très intéressante et donne un attrait intuitif au cadre. Dans cet article, l'auteur examine le travail de Ginsberg, y relève des lacunes et propose des moyens de les corriger. De plus, il expose certaines idées en vue de modifier le schéma original et ainsi obtenir un meilleur cadre du point de vue de la sémantique. 相似文献
L'utilisation de la Iogique multivalente pour la représentation des connaissances et le raisonnement non monotone a souvent été préconisée, en particulier à l'intérieur du cadre général proposé par Ginsberg dans son article intitulé〘 Multivalued logics: a uniform approach to reasoning in artificial intelligence 〙 Son système est basé sur une logique multivalente comportant un nombre arbitraire de valeurs de vérité classées selon deux ordres partiels: un ordre de vérité et un ordre de connaissances. Cette classification est très intéressante et donne un attrait intuitif au cadre. Dans cet article, l'auteur examine le travail de Ginsberg, y relève des lacunes et propose des moyens de les corriger. De plus, il expose certaines idées en vue de modifier le schéma original et ainsi obtenir un meilleur cadre du point de vue de la sémantique. 相似文献