全文获取类型
收费全文 | 20712篇 |
免费 | 813篇 |
国内免费 | 318篇 |
专业分类
电工技术 | 462篇 |
综合类 | 543篇 |
化学工业 | 3714篇 |
金属工艺 | 515篇 |
机械仪表 | 727篇 |
建筑科学 | 847篇 |
矿业工程 | 180篇 |
能源动力 | 558篇 |
轻工业 | 2065篇 |
水利工程 | 243篇 |
石油天然气 | 177篇 |
武器工业 | 27篇 |
无线电 | 2365篇 |
一般工业技术 | 2773篇 |
冶金工业 | 3670篇 |
原子能技术 | 168篇 |
自动化技术 | 2809篇 |
出版年
2023年 | 109篇 |
2022年 | 340篇 |
2021年 | 464篇 |
2020年 | 263篇 |
2019年 | 332篇 |
2018年 | 380篇 |
2017年 | 357篇 |
2016年 | 394篇 |
2015年 | 346篇 |
2014年 | 522篇 |
2013年 | 1010篇 |
2012年 | 786篇 |
2011年 | 964篇 |
2010年 | 741篇 |
2009年 | 806篇 |
2008年 | 792篇 |
2007年 | 814篇 |
2006年 | 703篇 |
2005年 | 602篇 |
2004年 | 677篇 |
2003年 | 896篇 |
2002年 | 1185篇 |
2001年 | 1013篇 |
2000年 | 588篇 |
1999年 | 532篇 |
1998年 | 1328篇 |
1997年 | 857篇 |
1996年 | 631篇 |
1995年 | 426篇 |
1994年 | 314篇 |
1993年 | 348篇 |
1992年 | 193篇 |
1991年 | 152篇 |
1990年 | 145篇 |
1989年 | 133篇 |
1988年 | 130篇 |
1987年 | 109篇 |
1986年 | 112篇 |
1985年 | 150篇 |
1984年 | 86篇 |
1983年 | 90篇 |
1982年 | 82篇 |
1981年 | 102篇 |
1980年 | 98篇 |
1979年 | 61篇 |
1978年 | 49篇 |
1977年 | 100篇 |
1976年 | 192篇 |
1975年 | 51篇 |
1973年 | 52篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
De Geronimo G. Bolotnikov A.E. Carini G. Fried J. O'Connor P. Soldner S.A. 《IEEE transactions on nuclear science》2006,53(2):456-461
A new version of the front-end application specific integrated circuit (ASIC) for co-planar-grid (CPG) sensors is presented. Compared to the first version, the ASIC is optimized for signal/noise performance, modified in peaking time, and it implements timing signals to measure the depth of interaction using the grids signals only. Experimental results using state-of the-art CPG sensors and different approaches for reducing the error due to electron trapping are reported. A new technique that makes use of the sum and difference of the grids signals is also presented. 相似文献
43.
44.
Yu Yang Hugo Bender Kai Arstila Bart Swinnen Bert Verlinden Ingrid De Wolf 《Microelectronics Reliability》2008,48(8-9):1517-1520
Focused ion beam (FIB) and nano-probing were applied for failure analysis of three-dimensional stacked circuits with copper through-silicon-vias between the stacked chips. The failure analysis was done after high temperature storage and thermal cycling tests. Passive voltage contrast in FIB allowed to pinpoint the open sites. FIB cross-sections showed the presence of opens at the bottom of the copper vias. The failure cause was suspected to be an interlayer particle, which was confirmed by optical profilometry. Nano-probing was used on another sample to pinpoint the failure location through the measurement of the local resistance within the daisy chains. The failure was traced out to be related with surface contamination. 相似文献
45.
The Y2O3: Yb3 , Er3 microstructures were fabricated by a hydrothermal method without surfactants.The microstructures structure was characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM,KYKY 1000B).The up-conversion luminescence spectra were studied under 978 nm laser diode excitation.In Yb3 and Er3 codoped Y2 O3 microcrystals, the relative intensity of green emission became stronger as the morphology of sample changed from wires to films. 相似文献
46.
This study provides a meta-analysis of research on the associations between relationship conflict, task conflict, team performance, and team member satisfaction. Consistent with past theorizing, results revealed strong and negative correlations between relationship conflict, team performance, and team member satisfaction. In contrast to what has been suggested in both academic research and introductory textbooks, however, results also revealed strong and negative (instead of the predicted positive) correlations between task conflict, team performance, and team member satisfaction. As predicted, conflict had stronger negative relations with team performance in highly complex (decision making, project, mixed) than in less complex (production) tasks. Finally, task conflict was less negatively related to team performance when task conflict and relationship conflict were weakly, rather than strongly, correlated. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
47.
A. Bianconi Y. Busby M. Fratini V. Palmisano L. Simonelli M. Filippi S. Sanna F. Congiu A. Saccone M. Giovannini S. De Negri 《Journal of Superconductivity and Novel Magnetism》2007,20(7-8):495-501
Here we report synthesis and characterization of high quality samples of the superconducting system Mg1−x
Al
x
B2, with a novel optimized preparation method, in a wide range of Al concentration. All the physical properties of the samples
can be tuned continuously with increasing Al content. We have characterized the samples for their structural, morphological
and magnetic properties with high resolution XRD, SEM-EDS and susceptibility measurements. We have prepared a large number
of Al doped MgB2 in the range 0<x<0.57. All the samples are bulk superconductors and the critical temperature show a smooth and regular behavior as a function
of x.
This work was supported by European project 517039 “Controlling Mesoscopic Phase Separation” (COMEPHS) (2005).
An erratum to this article can be found at 相似文献
48.
Recent years have witnessed major governmental initiatives regarding critical infrastructure protection (CIP). During that same time, critical infrastructures (CIs) have undergone massive institutional restructuring under the headings of privatization, deregulation and liberalization. Little research has gone into understanding the interactions between these two developments. In this article, we outline the consequences of institutional restructuring for the changing ways in which CIs ensure the reliability and security of their networks and services. Neither Normal Accident Theory nor High‐Reliability Theory can account for reliability under these conditions. We then investigate the implications of these findings for CIP. 相似文献
49.
框架结构焦仓的定向倒塌爆破 总被引:4,自引:1,他引:3
介绍了框架结构焦仓定向爆破拆除的设计与施工,着重介绍了爆破参烽的选取及安全防护措施。达到预期的爆破效果。 相似文献
50.
The key synchronization aspects in the system design of a QQPSK (quadrature-quadrature phase-shift-keying) modem are addressed. The sensitivity of the data demodulator to synchronization errors is discussed, and contextually the performances of some IF and baseband carrier phase and symbol timing recovery schemes are evaluated both theoretically and by computer simulations. In particular, a fourth-power IF carrier/clock regenerator and two baseband clock recovery schemes, with and without the aid of data decisions, respectively, are taken into account. The analysis shows on the one hand the substantial robustness of QQPSK to carrier phase errors and the adequacy of the examined carrier extraction scheme. On the other hand, the remarkable sensitivity of QQPSK to symbol timing inaccuracy is stressed and the need to resort to the newly proposed decision-aided baseband clock recovery scheme is pointed out 相似文献