全文获取类型
收费全文 | 905篇 |
免费 | 17篇 |
专业分类
电工技术 | 13篇 |
化学工业 | 147篇 |
金属工艺 | 16篇 |
机械仪表 | 14篇 |
建筑科学 | 24篇 |
能源动力 | 13篇 |
轻工业 | 75篇 |
水利工程 | 6篇 |
石油天然气 | 1篇 |
无线电 | 92篇 |
一般工业技术 | 126篇 |
冶金工业 | 307篇 |
原子能技术 | 6篇 |
自动化技术 | 82篇 |
出版年
2022年 | 9篇 |
2021年 | 13篇 |
2020年 | 8篇 |
2019年 | 11篇 |
2018年 | 8篇 |
2017年 | 14篇 |
2016年 | 7篇 |
2015年 | 6篇 |
2014年 | 11篇 |
2013年 | 35篇 |
2012年 | 25篇 |
2011年 | 52篇 |
2010年 | 24篇 |
2009年 | 31篇 |
2008年 | 37篇 |
2007年 | 38篇 |
2006年 | 35篇 |
2005年 | 47篇 |
2004年 | 28篇 |
2003年 | 28篇 |
2002年 | 25篇 |
2001年 | 14篇 |
2000年 | 15篇 |
1999年 | 19篇 |
1998年 | 44篇 |
1997年 | 31篇 |
1996年 | 33篇 |
1995年 | 17篇 |
1994年 | 18篇 |
1993年 | 15篇 |
1992年 | 18篇 |
1991年 | 11篇 |
1990年 | 18篇 |
1989年 | 17篇 |
1988年 | 12篇 |
1987年 | 22篇 |
1986年 | 20篇 |
1985年 | 8篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1980年 | 9篇 |
1979年 | 6篇 |
1977年 | 14篇 |
1976年 | 10篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1971年 | 3篇 |
1970年 | 4篇 |
1966年 | 3篇 |
1964年 | 3篇 |
排序方式: 共有922条查询结果,搜索用时 0 毫秒
1.
2.
Metal-clad ridge waveguide (MCRW), double quantum well, separately confined heterostrucuture (DQW-SCH) lasers have been fabricated having continuous-wave (CW) threshold currents of 10?12 mA and external differential quantum efficiencies of 41?46% per uncoated facet. Light/current characteristics are linear to >70 mW, and zero-order lateral mode operation was measured at 56 mW. The CW burn-off power density is nearly double the best previously reported value. 相似文献
3.
4.
5.
Whiteaway J.E.A. Garrett B. Thompson G.H.B. Collar A.J. Armistead C.J. Fice M.J. 《Quantum Electronics, IEEE Journal of》1992,28(5):1277-1293
The influence of longitudinal mode spatial hole burning (LMSHB) on the performance of distributed feedback (DFB) laser structures is examined in detail. A comprehensive model has been used to interpret the experimental results and to construct a theoretical framework that was utilized to develop more advanced device designs. An increasing side mode intensity with output power, movement of the lasing mode relative to the stopband, and curvature of the light-current characteristic at low power can all be manifestations of the influence of LMSHB on the static device performance. The dynamic behavior can also be affected, with extended wavelength chirp and amplitude patterning effects on the timescale of the effective carrier recombination time being particularly important 相似文献
6.
Reddy R. Garrett R. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1995,83(8):1188-1195
The paper examines the changes in computer and communications capabilities over the next 10-15 years which are most likely to affect the central components of distributed interactive simulation (DIS): manned simulators, synthetic environments, and semi-automated forces (SAF). Because these components of DIS are currently very resource intensive, improvements in computer and communications capabilities translate into direct and immediate improvements in DIS capabilities. These improved capabilities in turn allow DIS to contribute in much broader arenas, enhancing troop readiness and reducing system acquisition costs. These improvements will not all come automatically, however. Substantial planning is required to ensure that DIS can take advantage of the coming changes, rather than being overcome by them 相似文献
7.
Eric Keto Roger Ball John Arens Garrett Jernigan Margaret Meixner 《Journal of Infrared, Millimeter and Terahertz Waves》1992,13(11):1709-1725
We present a characterization of some processes affecting the performance of solid state array cameras designed for ground based astronomical imaging in the 8–13μm atmospheric window. Our discussion includes a novel model for electron-hole generationrecombination noise based on the probable pathlength of an electron in a photoconductor. We use the Berkeley mid-IR Array Camera as an example. For this camera, the results show that the total optical system composed of the camera, a 3m telescope, and the atmosphere has an efficiency of about 3%, a 1σ noise equivalent flux density of 25 mJy min?1/2arcsec?2 measured over a Δλ/λ=10% band width, and a noise equivalent expressed as the ambient temperature thermal black body noise of 23%. 相似文献
8.
Garrett J.E. Ruehli A.E. Paul C.R. 《Antennas and Propagation, IEEE Transactions on》1998,46(12):1824-1832
The partial element equivalent circuit (PEEC) technique is a formulation which transforms an electric field integral equation (EFIE) into a full-wave equivalent circuit solution. In this paper, improvements are made to the PEEC model through the development of a refined method of computing both the partial inductances as well as the coefficients of potential. The method does not increase the number of unknowns. In addition, damping is added to the PEEC model in order to further reduce nonphysical resonances which may occur above the useful frequency range, The observations and solutions presented in this paper are especially important for time domain solvers. The effectiveness of the method is illustrated with several examples 相似文献
9.
The long-term effects of the Cognitive Adaptation Theory Index (CATI) on psychological and physical health outcomes among men (n=199) and women (n=99) treated for coronary artery disease with percutaneous transluminal coronary angioplasty were examined. The CATI reflects a positive view of the self, a positive view of one's future, and a sense of personal control over daily life. This index was created from questionnaires administered during hospitalization for the initial angioplasty. Four years later, the CATI predicted positive adjustment to disease, even when initial adjustment was taken into consideration. In addition, the CATI predicted a reduced likelihood of sustaining a subsequent cardiac event over 4 yrs. This association was more robust for men. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
10.