全文获取类型
收费全文 | 40010篇 |
免费 | 1301篇 |
国内免费 | 65篇 |
专业分类
电工技术 | 502篇 |
综合类 | 49篇 |
化学工业 | 6679篇 |
金属工艺 | 742篇 |
机械仪表 | 785篇 |
建筑科学 | 1946篇 |
矿业工程 | 155篇 |
能源动力 | 1095篇 |
轻工业 | 3867篇 |
水利工程 | 460篇 |
石油天然气 | 97篇 |
无线电 | 3318篇 |
一般工业技术 | 6093篇 |
冶金工业 | 9484篇 |
原子能技术 | 276篇 |
自动化技术 | 5828篇 |
出版年
2023年 | 192篇 |
2022年 | 299篇 |
2021年 | 613篇 |
2020年 | 395篇 |
2019年 | 503篇 |
2018年 | 664篇 |
2017年 | 656篇 |
2016年 | 740篇 |
2015年 | 620篇 |
2014年 | 959篇 |
2013年 | 1961篇 |
2012年 | 1595篇 |
2011年 | 2193篇 |
2010年 | 1522篇 |
2009年 | 1586篇 |
2008年 | 1708篇 |
2007年 | 1656篇 |
2006年 | 1394篇 |
2005年 | 1359篇 |
2004年 | 1163篇 |
2003年 | 1074篇 |
2002年 | 1006篇 |
2001年 | 724篇 |
2000年 | 654篇 |
1999年 | 813篇 |
1998年 | 2489篇 |
1997年 | 1603篇 |
1996年 | 1203篇 |
1995年 | 847篇 |
1994年 | 819篇 |
1993年 | 776篇 |
1992年 | 491篇 |
1991年 | 377篇 |
1990年 | 459篇 |
1989年 | 420篇 |
1988年 | 391篇 |
1987年 | 314篇 |
1986年 | 306篇 |
1985年 | 392篇 |
1984年 | 356篇 |
1983年 | 275篇 |
1982年 | 291篇 |
1981年 | 298篇 |
1980年 | 245篇 |
1979年 | 275篇 |
1978年 | 214篇 |
1977年 | 277篇 |
1976年 | 340篇 |
1975年 | 213篇 |
1974年 | 184篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
101.
MarcelvanRoosmalen MatthiasLocher 《世界电子元器件》2004,(12):75-76
射频存储系统的目标市场有两个,一个是宽带网络,一个是无线局域网:下图介绍的是第一公里的无线宽带接入系统。图的中央有一个中枢(hub),它的周围是一个分布网络。这是一个包括光和电的、数据和模拟结合的网络,这种系统在中国的大城市都有广泛的部署。圆圈是飞利浦开发的一些结点、中枢和分布网络,包括放大器和光电设备。 相似文献
102.
Additional remarks are given for the data of auroras during the earlier centuries. 相似文献
103.
Paul I. Dalven James R. Hildebrandt Abraham Shamir Anthony J. Laccetti Leonard T. Hodgins Harry P. Gregor 《应用聚合物科学杂志》1985,30(3):1113-1132
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
104.
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
105.
van Baaren Rick B.; Maddux William W.; Chartrand Tanya L.; de Bouter Cris; van Knippenberg Ad 《Canadian Metallurgical Quarterly》2003,84(5):1093
The present studies demonstrated the moderation of self-construal orientation on mimicry. Recent research has indicated that an interdependent self-construal is associated with assimilation of the other to the self whereas an independent self-construal is associated with minimizing the influence of others on the self (H. R. Markus & S. Kitayama, 1991; D. Stapel & W. Koomen, 2001). Therefore, the authors hypothesized that an interdependent self-construal would be associated with more mimicry than an independent self-construal. When self-construal orientations were experimentally primed. as in Studies 1 and 2, independent self-construals produced less nonconscious mimicry than interdependent self-construals. When self-construals were examined as cultural differences with either a chronically dominant independent (Americans) or interdependent (Japanese) construal of the self, these results were replicated. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
106.
van der Wielen P.C.J.M. Steennis E.F. Wouters P.A.A.F. 《Dielectrics and Electrical Insulation, IEEE Transactions on》2003,10(4):678-688
On-line partial discharge (PD) detection of three-phase belted medium voltage cable connections results in a number of interpretation differences as compared to off-line measurements where only one phase is energized. The induced currents and charges in the phase conductors and earth screen upon a PD not only depend on the discharge site, but also become phase angle dependent. Furthermore, simulations show that the PD distribution itself varies with the amount of eccentricity of the rotating electric field and may differ from the off-line distributions obtained with a linear field. Finally, the PD propagation in a multi-conductor cable also alters the signals measured at the cable terminals. In this paper, induced charges and PD distributions are studied by means of computer simulation. The cable propagation characteristics are verified by measurements. 相似文献
107.
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
108.
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
109.
110.