首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   248255篇
  免费   3483篇
  国内免费   1457篇
化学   123075篇
晶体学   3229篇
力学   8883篇
综合类   61篇
数学   24453篇
物理学   65684篇
无线电   27810篇
  2020年   1905篇
  2019年   2098篇
  2018年   2683篇
  2017年   2736篇
  2016年   3953篇
  2015年   2614篇
  2014年   3909篇
  2013年   9455篇
  2012年   8174篇
  2011年   10011篇
  2010年   7249篇
  2009年   7314篇
  2008年   9911篇
  2007年   10272篇
  2006年   9748篇
  2005年   8944篇
  2004年   8067篇
  2003年   7160篇
  2002年   7029篇
  2001年   7814篇
  2000年   6102篇
  1999年   4581篇
  1998年   3893篇
  1997年   3908篇
  1996年   3763篇
  1995年   3369篇
  1994年   3507篇
  1993年   3362篇
  1992年   3506篇
  1991年   3586篇
  1990年   3399篇
  1989年   3283篇
  1988年   3097篇
  1987年   2789篇
  1986年   2795篇
  1985年   3621篇
  1984年   3648篇
  1983年   3026篇
  1982年   3262篇
  1981年   3026篇
  1980年   2794篇
  1979年   2954篇
  1978年   3179篇
  1977年   3180篇
  1976年   3203篇
  1975年   2951篇
  1974年   3040篇
  1973年   3085篇
  1972年   2410篇
  1971年   1938篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
The cellular neural network (CNN) architecture combines the best features from traditional fully-connected analog neural networks and digital cellular automata. The network can rapidly process continuous-valued (gray-scale) input signals (such as images) and perform many computation functions which traditionally were implemented in digital form. Here, we briefly introduce the the theory of CNN circuits, provide some examples of CNN applications to image processing, and discuss work toward a CNN implementation in custom CMOS VLSI. The role of analog computer-aided design (CAD) will be briefly presented as it relates to analog neural network implementation.This work is supported in part by the Office of Naval Research under Contract N00014-89-J1402, and the National Science Foundation under grant MIP-8912639.  相似文献   
992.
A detailed study on the leverage of high-fT transistors for advanced high-speed bipolar circuit applications is presented. It is shown that for the standard ECL (emitter-coupled logic) circuit, the leverage of high fT is limited by the passive resistors (emitter-follower resistor and collector load resistor) and wire delay, especially in the low-power regime. For the standard NTL (nonthreshold logic) circuit, the leverage is higher due to its front-end configuration and lower power supply value. As the passive resistors are decoupled from the delay path in various advanced circuits utilizing active-pull-down schemes, the leverage of high FT becomes more significant  相似文献   
993.
994.
Liquid-phase chlorination of a number of chloro(chlorovinyl)methylsilanes was investigated. A number of novelC-chlorosilanes were characterized by IR and1H NMR spectra. Some regularities of these reactions were determined; correlations between the structure of chloro(chlorovinyl)methylsilanes and their reactivities were identified.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2256–2260, November, 1995.  相似文献   
995.
996.
Based on the Lenard relations, we completely classify integrable deformations of general algebraic curves. We construct the general solution of the Lenard relation from the invariance condition with respect to an element of the Galois group of the curve. We give some examples and also some associated conservation laws. __________ Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 151, No. 3, pp. 458–469, June, 2007.  相似文献   
997.
998.
999.
We present a study of the temporal compression of nanosecond laser pulses resulting from the coherent control peculiarities of the propagation dynamics in a regime of electromagnetically induced transparency. We describe the general theoretical framework and discuss the crucial conditions required in order to experimentally realize such a temporal compression scheme. A proof-of-concept experimental realization of a scheme of this type in a sample of hot sodium vapors is currently being implemented: we describe in detail the experimental setup designed for this purpose.  相似文献   
1000.
Nanostructuring of natural isoferroplatinum crystals is revealed by atomic-force microscopy for the first time. Typical scales of ~30, 50, and 100 nm are determined and the self-affine character of their relation is established using a wavelet analysis.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号