全文获取类型
收费全文 | 566734篇 |
免费 | 6227篇 |
国内免费 | 1004篇 |
专业分类
电工技术 | 10508篇 |
综合类 | 466篇 |
化学工业 | 90039篇 |
金属工艺 | 23335篇 |
机械仪表 | 18497篇 |
建筑科学 | 12529篇 |
矿业工程 | 4312篇 |
能源动力 | 14429篇 |
轻工业 | 45756篇 |
水利工程 | 6941篇 |
石油天然气 | 14961篇 |
武器工业 | 39篇 |
无线电 | 60278篇 |
一般工业技术 | 116218篇 |
冶金工业 | 95555篇 |
原子能技术 | 14681篇 |
自动化技术 | 45421篇 |
出版年
2021年 | 5481篇 |
2019年 | 5267篇 |
2018年 | 9201篇 |
2017年 | 9409篇 |
2016年 | 9831篇 |
2015年 | 6025篇 |
2014年 | 10243篇 |
2013年 | 26100篇 |
2012年 | 15771篇 |
2011年 | 21087篇 |
2010年 | 16968篇 |
2009年 | 18817篇 |
2008年 | 19067篇 |
2007年 | 18765篇 |
2006年 | 16285篇 |
2005年 | 14742篇 |
2004年 | 14007篇 |
2003年 | 13691篇 |
2002年 | 13246篇 |
2001年 | 12850篇 |
2000年 | 12330篇 |
1999年 | 12011篇 |
1998年 | 27648篇 |
1997年 | 20038篇 |
1996年 | 15628篇 |
1995年 | 12005篇 |
1994年 | 10858篇 |
1993年 | 10612篇 |
1992年 | 8332篇 |
1991年 | 8102篇 |
1990年 | 7990篇 |
1989年 | 7763篇 |
1988年 | 7478篇 |
1987年 | 6747篇 |
1986年 | 6533篇 |
1985年 | 7390篇 |
1984年 | 6700篇 |
1983年 | 6437篇 |
1982年 | 5776篇 |
1981年 | 5896篇 |
1980年 | 5630篇 |
1979年 | 5733篇 |
1978年 | 5663篇 |
1977年 | 6178篇 |
1976年 | 7685篇 |
1975年 | 5108篇 |
1974年 | 4903篇 |
1973年 | 4980篇 |
1972年 | 4279篇 |
1971年 | 4038篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
Crosstalk between microstrip transmission lines 总被引:1,自引:0,他引:1
Hill D.A. Cavcey K.H. Johnk R.T. 《Electromagnetic Compatibility, IEEE Transactions on》1994,36(4):314-321
Methods for prediction of crosstalk between microstrip transmission lines are reviewed and simplified for the weak-coupling case. Classical coupled transmission line theory is used for uniform lines, and potential and induced EMF methods are used for crosstalk between nonuniform lines. It is shown that the potential method is equivalent to classical coupled transmission line theory for the case of uniform lines. An experiment was performed for uniform coupled microstrip lines for frequencies from 50 MHz to 5 GHz, and good agreement between theory and measurement was obtained for both near- and far-end crosstalk 相似文献
102.
A. A. Presnyakov 《Strength of Materials》1994,26(2):162-165
The author examines the problems of spontaneous and stationary localization of deformation on the development of plastic yielding in pressure working of metals. It is established that localization of plastic yielding results in the dispersion of the geometrical dimensions, structure, texture and properties, and also in changes in their general level. Possible methods of affecting the deformation region are discussed with special reference to controlling the development of localization of plastic yielding and properties of the component.Translated from Problemy Prochnosti, No. 2, pp. 89–92, February, 1994. 相似文献
103.
A. A. Kovalev A. F. Kotyuk B. N. Levinskii A. A. Liberman 《Measurement Techniques》1994,37(2):151-158
The authors survey published results on the application of metal diffraction gratings as laser power or energy dividers when the laser beam is split into two approximately equal pans. The normal incidence of laser radiation on metal diffraction gratings of various profiles in the case of three propagating diffraction orders n=0, ±1 is discussed, along with the case of oblique incidence with only two propagating diffraction orders n=0 and n =–1.Translated from Izmeritel'naya Tekhnika, No. 2, pp. 22–26, February, 1994. 相似文献
104.
A.S. Fomichev I. David S.M. Lukyanov Yu.E. Penionzhkevich N.K. Skobelev O.B. Tarasov 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1994,350(3):605-607
The mass and charge identification of secondary particles with Z < 4 by a large CsI(T1) scintillation detector is performed using pulse shape analysis and time-of-flight methods. The dependence of the light output on E, A and Z is studied in the energy range of 1–20 MeV/A and special attention is paid to the integration time of the photomultiplier anode signal. It is found that the behaviour of the calibration curves strongly depends on the choice of the integration time interval. 相似文献
105.
106.
107.
MA Nowak AL Lloyd GM Vasquez TA Wiltrout LM Wahl N Bischofberger J Williams A Kinter AS Fauci VM Hirsch JD Lifson 《Canadian Metallurgical Quarterly》1997,71(10):7518-7525
Mathematical modeling of viral replication dynamics, based on sequential measurements of levels of virion-associated RNA in plasma during antiretroviral treatment, has led to fundamental new insights into human immunodeficiency virus type 1 pathogenesis. We took advantage of the simian immunodeficiency virus (SIV)-infected macaque model to perform detailed measurements and mathematical modeling during primary infection and during treatment of established infection with the antiretroviral drug (R)-9-(2-phosphonylmethoxypropyl)adenine (PMPA). The calculated clearance half-life for productively infected cells during resolution of the peak viremia of primary infection was on the order of 1 day, with slightly shorter clearance half-lives calculated during PMPA treatment. Viral reproduction rates upon discontinuation of PMPA treatment after 2 weeks were approximately twofold greater than those obtained just prior to initiation of treatment in the same animals, likely reflecting accumulation of susceptible target cells during treatment. The basic reproductive ratio (R0) for the spread of SIV infection in vivo, which represents the number of productively infected cells derived from each productively infected cell at the beginning of infection, was also estimated. This parameter quantifies the extent to which antiviral therapy or vaccination must limit the initial spread of virus to prevent establishment of chronic disseminated infection. The results thus provide an important guide for efforts to develop vaccines against SIV and, by extension, human immunodeficiency virus. 相似文献
108.
Based on a variational analysis, the authors demonstrate that the noise-induced Gordon-Haus timing jitter in a dispersion-managed soliton transmission system can be substantially reduced by appropriate placement of the amplifiers 相似文献
109.
110.
An antenna array for wideband operation (up to 70%) is presented. The structure has low windloading area and consists of parallel printed circuit boards (PCB) with microstrip dipoles, feed network and metal fences placed between the PCBs. The low profile, low weight antenna array forms the main beam and three difference patterns for sidelobe cancellation. Experimental results are compared with calculations for both microstrip dipole and array 相似文献