全文获取类型
收费全文 | 13739篇 |
免费 | 1038篇 |
国内免费 | 35篇 |
专业分类
电工技术 | 174篇 |
综合类 | 8篇 |
化学工业 | 3239篇 |
金属工艺 | 322篇 |
机械仪表 | 516篇 |
建筑科学 | 475篇 |
矿业工程 | 27篇 |
能源动力 | 518篇 |
轻工业 | 2568篇 |
水利工程 | 181篇 |
石油天然气 | 67篇 |
武器工业 | 2篇 |
无线电 | 894篇 |
一般工业技术 | 2322篇 |
冶金工业 | 1355篇 |
原子能技术 | 112篇 |
自动化技术 | 2032篇 |
出版年
2024年 | 32篇 |
2023年 | 145篇 |
2022年 | 174篇 |
2021年 | 667篇 |
2020年 | 444篇 |
2019年 | 508篇 |
2018年 | 613篇 |
2017年 | 622篇 |
2016年 | 623篇 |
2015年 | 450篇 |
2014年 | 604篇 |
2013年 | 1032篇 |
2012年 | 915篇 |
2011年 | 1092篇 |
2010年 | 735篇 |
2009年 | 791篇 |
2008年 | 697篇 |
2007年 | 587篇 |
2006年 | 464篇 |
2005年 | 355篇 |
2004年 | 287篇 |
2003年 | 271篇 |
2002年 | 249篇 |
2001年 | 191篇 |
2000年 | 193篇 |
1999年 | 173篇 |
1998年 | 445篇 |
1997年 | 290篇 |
1996年 | 204篇 |
1995年 | 148篇 |
1994年 | 120篇 |
1993年 | 91篇 |
1992年 | 58篇 |
1991年 | 46篇 |
1990年 | 41篇 |
1989年 | 51篇 |
1988年 | 34篇 |
1987年 | 30篇 |
1986年 | 30篇 |
1985年 | 35篇 |
1984年 | 39篇 |
1983年 | 32篇 |
1982年 | 18篇 |
1981年 | 23篇 |
1980年 | 23篇 |
1979年 | 17篇 |
1977年 | 27篇 |
1976年 | 38篇 |
1975年 | 10篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
AR Santos JC Nery NC Duppre ME Gallo JT Filho PN Suffys WM Degrave 《Canadian Metallurgical Quarterly》1997,46(2):170-172
A case is described in which a pericardial branch of a nongrafted left internal mammary artery communicated directly with the distal left anterior descending artery, following saphenous vein bypass grafting. This type of collateralization following coronary artery bypass surgery seems to be very rare, and perhaps could protect the myocardium from severe ischemia. 相似文献
62.
By Cooperative Editing we mean the coordinated manipulation of information by a group of authors. During the editing process the (co-)authors need to communicate their ideas, drafts and constraints (remotely or face-to-face) until a final version of the information is achieved. For the different phases of this process - discussion of ideas, editing, cross-checking - different media or media integration are adequate. Furthermore, analysing the transition from individual work to group work, within different human activities, two pitfalls are often detected if computer support is considered: a) technological communication difficulties, especially if the group is remotely located on heterogeneous hardware, associated with a fall in productivity and frequent social inadequacies of the group's computer support; b) the lack of integrated media processing tools available for group editing. In order to solve these problems, we suggest that Multimedia can be applied in two ways: to effectively support the necessary group communication links; and to enhance the expressiveness of the information edited. To test this statement we have been conceptualising and implementing a prototype system. Most of the techniques involved can be used in other tools that need multimedia capabilities or that support other specific types of group activities. The innovative aspects of the work are the use of multimedia techniques to support demanding applications, possibly on cross-platforms, and the integration of several concepts to support cooperation. 相似文献
63.
64.
Adelino Santos 《计算机科学技术学报》1993,8(3):67-79
CoMEdiA is a groupware tool which enables co-authors to cooperatively produce hypermedia documents.CoMEdiA allows co-authors to communicate their ideas,drafts,guidelines,constraints and annotations to other co-authors.In uses a mix of communication patterns,media and document organization to enable co-authors to keep on exchanging information(remotely or face-to-face),improving passages and modifying notes until a final document is achieved.We did not concentrate on th depth but on the breath of the features.Our efforts were on integrating and corrdinating concepts from collaboration,multimedia and hyper organization rather than on making a specialized system in any of them.We began with the text medium and are now including bitmaps and raster images.Later sound and video will also be integrated.In this paper we describe and sustain the available capacites. 相似文献
65.
66.
67.
Román Gómez Gonz ález Cosío 《International Planning Studies》1998,3(3):367-389
The concept of capacity building for environmental protection and management refers to the process by which the abilities of societies to identify and solve environmental problems are developed. This work assumes a social constructivist perspective to the process of capacity building for environmental governance and thus depicts it as critically dependent on broader processes of political and socioeconomic modernization. In an attempt to depict such a process, a heuristic device is put forward as a model of capacity analysis. A theoretical discourse and new institutionalist perspectives are used to test such a model on a theoretical plane. Some preliminary conclusions are drawn from this theoretical exercise. 相似文献
68.
A model stomach, containing a food matrix and a synthetic gastric fluid, was used to study the bactericidal effect of ingested wine on Listeria innocua. Volumes of wine equivalent to the ingestion of one glass and half a bottle, led, over a period of less than 2 h, to a reduction of 3 and 4 logarithmic cycles of the initial population respectively. The influence of ethanol and organic acids, wine constituents with known antimicrobial properties, was investigated. Ethanol exhibited a higher bactericidal effect than the mixture of the main wine organic acids. When testing the organic acids separately, malic and lactic acids were found to have the strongest effect. The combination of ethanol with the organic acids acted synergistically but to a lesser extent than wine itself. The results suggest that the ingestion of wine during a meal may diminish the quantity of Listeria persisting further in the alimentary tract. 相似文献
69.
Paulo S. André António L. Teixeira Armando N. Pinto Lara P. Pellegrino Berta B. Neto José F. Rocha Joäo L. Pinto Paulo N. Monteiro 《ETRI Journal》2006,28(2):257-259
In this letter, we will evaluate the performance degradation of a 40 km high‐speed (40 Gb/s) optical system, induced by optical fiber variations of the chromatic dispersion induced by temperature changes. The chromatic dispersion temperature sensitivity will be estimated based on the signal quality parameters. 相似文献
70.
Fbio Gomes Costa Elias Andrade Braga Soraia Teixeira Brando Alexandre de Freitas Espeleta Zênis Novais da Rocha Lílian Maria Tosta Simplício Emerson Andrade Sales 《Applied Catalysis A: General》2005,290(1-2):221-226
Infrared and UV–vis studies of metallocene immobilization on silica are reported here. The results have indicated changes in the Zr coordination sphere of metallocene depending on the immobilization route used. The reaction of [(Cp)2ZrCl2] with silica formed [(Cp)2ZrCl]+[SiO]− species. The same metallocene, reacting with TMA modified silica, formed monomethylated and dimethylated species by the substitution of chloro for methyl ligands, stabilized on the surface by interaction with “MAO-like” species (methylaluminoxane, MAO). These monomethylated and dimethylated cationic zirconium species are the active centers for the polymerization reaction. Different order of TMA addition in the silica modification step generated surface species of a similar nature, differing in their relative quantities. The highest amount of these active species was obtained when the support was added to the TMA solution rather than adding the TMA solution to the silica support. This was the most significant parameter affecting catalytic activity in ethylene polymerization. 相似文献