全文获取类型
收费全文 | 253501篇 |
免费 | 2812篇 |
国内免费 | 873篇 |
专业分类
电工技术 | 4813篇 |
综合类 | 194篇 |
化学工业 | 36220篇 |
金属工艺 | 9526篇 |
机械仪表 | 7565篇 |
建筑科学 | 6083篇 |
矿业工程 | 880篇 |
能源动力 | 7249篇 |
轻工业 | 21111篇 |
水利工程 | 2210篇 |
石油天然气 | 3231篇 |
武器工业 | 15篇 |
无线电 | 34408篇 |
一般工业技术 | 50092篇 |
冶金工业 | 48583篇 |
原子能技术 | 5077篇 |
自动化技术 | 19929篇 |
出版年
2022年 | 1474篇 |
2021年 | 2210篇 |
2020年 | 1579篇 |
2019年 | 1946篇 |
2018年 | 3310篇 |
2017年 | 3327篇 |
2016年 | 3425篇 |
2015年 | 2236篇 |
2014年 | 3978篇 |
2013年 | 11513篇 |
2012年 | 6265篇 |
2011年 | 8599篇 |
2010年 | 6936篇 |
2009年 | 7906篇 |
2008年 | 8427篇 |
2007年 | 8318篇 |
2006年 | 7388篇 |
2005年 | 6516篇 |
2004年 | 6292篇 |
2003年 | 6565篇 |
2002年 | 6045篇 |
2001年 | 6527篇 |
2000年 | 5980篇 |
1999年 | 6396篇 |
1998年 | 16490篇 |
1997年 | 11417篇 |
1996年 | 8803篇 |
1995年 | 6611篇 |
1994年 | 5910篇 |
1993年 | 5851篇 |
1992年 | 4141篇 |
1991年 | 4026篇 |
1990年 | 3859篇 |
1989年 | 3653篇 |
1988年 | 3566篇 |
1987年 | 3020篇 |
1986年 | 2944篇 |
1985年 | 3207篇 |
1984年 | 2929篇 |
1983年 | 2834篇 |
1982年 | 2641篇 |
1981年 | 2544篇 |
1980年 | 2464篇 |
1979年 | 2307篇 |
1978年 | 2109篇 |
1977年 | 2607篇 |
1976年 | 3566篇 |
1975年 | 1765篇 |
1974年 | 1731篇 |
1973年 | 1667篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
RM Torres CL Law L Santos-Argumedo PA Kirkham K Grabstein RM Parkhouse EA Clark 《Canadian Metallurgical Quarterly》1992,149(8):2641-2649
The human B lymphocyte-specific Ag, CD22, is a cell adhesion molecule expressed on the surface during a narrow window of B cell development, coincident with surface IgD. A ligand for CD22 has recently been identified on human T cells as the low molecular mass isoform of the leukocyte common Ag, CD45RO. CD22 has been reported to function in the regulation of both T and B cell activation in vitro. In this study, we report the isolation and expression of a molecular cDNA clone encoding the murine homologue of CD22, mCD22. Within their predicted protein sequences, murine and human sequences overall have 62% identity, which includes 18 of 20 extracellular cysteines and six of six cytoplasmic tyrosines. BHK cells transfected with mCD22 cDNA specifically adhere to resting and activated T lymphocytes and in addition bound activated, but not resting, B cells. Five Th clones were analyzed for their ability to adhere to mCD22; two Th0 clones and one Th1 clone bound CD22+ BHK transfectants, but not all T cell clones bound CD22+ cells: another Th1 clone and a Th2 clone did not. mCD22+ BHK transfectants were also specifically bound by the B cell-specific mAb, NIM-R6, demonstrating that this mAb is specific for murine CD22. Human cell lines expressing the counter-receptors for human CD22 were also examined for adhesion to the murine CD22 homologue; the epitope responsible for B cell adhesion to CD22 is conserved, whereas the T cell epitope binding to CD22 is not. The cDNA and mAb to murine CD22 will be useful for defining the in vivo function of CD22. 相似文献
993.
The main principles of a measurement procedure are given and its implementation with the aid of an IR-imager AGA-780 is shown.State Institute of Applied Optics, Kazan. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 63, No. 1, pp. 109–113. July, 1992. 相似文献
994.
On the Theory of Electrical Phenomena in Combustion of Heterogeneous Systems with Condensed Products
V. K. Smolyakov A. I. Kirdyashkin Yu. M. Maksimov 《Combustion, Explosion, and Shock Waves》2002,38(6):675-680
The effect of the electromotive force arising in combustion of heterogeneous systems with condensed products is explained. A convective mechanism of arising regions with different charge densities due to charge transfer by the gas filtered in the pores is formulated on the basis of the developed physical concepts, estimates, and analysis of experimental data. Key words: combustion, electron emission, filtration, electromotive force. 相似文献
995.
Novel high voltage pumping circuits for low supply voltages are proposed. Utilising a small pumping circuit and the new substrate-connected techniques can enhance charge transfer efficiency and eliminate the body effect at low supply voltages. Furthermore, a diode-connected transistor technique can improve the reverse charge sharing phenomenon when the output has a load current. With this technique high boosted voltages can be obtained at low supply voltages 相似文献
996.
P. Kristiansson C. M. Nilsson H. Busk L. Malmqvist M. Elfman K. G. Malmqvist J. Pallon K. A. Sj land R. J. Utui C. Yang 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》1997,130(1-4):303-307
A technique for measuring optical dot gain, i.e. the relative difference between the actual screen dot and the optically perceived one, is presented. By combining measurements from the non-optical nuclear microprobe with data from image analyzing technique the optical dot gain can be determined. The procedure to reach pixel by pixel correlation on a micrometer scale is discussed. In the newsprint sample studied in this investigation a typical optical dot gain between 15 and 20% was deduced. The variation in the optical dot gain was correlated with other characteristic parameters of the print and newsprint and especially a positive correlation to the mass density of the newsprint was observed. 相似文献
997.
998.
A simple method (based on Floquet theory) for obtaining the characteristic equation (and hence stability) of periodic discrete-time systems is presented. Using this method it is shown that 2-periodic controllers can be used to relocate the zeros of SISO plants. Some examples are considered to illustrate the use of 2-periodic controllers for robust control of finite gain margin problems 相似文献
999.
1000.