全文获取类型
收费全文 | 500326篇 |
免费 | 5786篇 |
国内免费 | 1898篇 |
专业分类
化学 | 271163篇 |
晶体学 | 7266篇 |
力学 | 20769篇 |
综合类 | 9篇 |
数学 | 60817篇 |
物理学 | 147986篇 |
出版年
2020年 | 3585篇 |
2019年 | 3749篇 |
2018年 | 4219篇 |
2017年 | 4031篇 |
2016年 | 7215篇 |
2015年 | 5444篇 |
2014年 | 7759篇 |
2013年 | 22943篇 |
2012年 | 17042篇 |
2011年 | 21291篇 |
2010年 | 13508篇 |
2009年 | 13406篇 |
2008年 | 19201篇 |
2007年 | 19552篇 |
2006年 | 18580篇 |
2005年 | 17101篇 |
2004年 | 15311篇 |
2003年 | 13535篇 |
2002年 | 13227篇 |
2001年 | 14783篇 |
2000年 | 11436篇 |
1999年 | 9082篇 |
1998年 | 7461篇 |
1997年 | 7297篇 |
1996年 | 7193篇 |
1995年 | 6645篇 |
1994年 | 6322篇 |
1993年 | 6240篇 |
1992年 | 6838篇 |
1991年 | 6765篇 |
1990年 | 6323篇 |
1989年 | 6159篇 |
1988年 | 6392篇 |
1987年 | 6066篇 |
1986年 | 5841篇 |
1985年 | 8264篇 |
1984年 | 8436篇 |
1983年 | 6913篇 |
1982年 | 7544篇 |
1981年 | 7427篇 |
1980年 | 7168篇 |
1979年 | 7251篇 |
1978年 | 7506篇 |
1977年 | 7335篇 |
1976年 | 7411篇 |
1975年 | 6987篇 |
1974年 | 6955篇 |
1973年 | 7284篇 |
1972年 | 4403篇 |
1971年 | 3308篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
The Al2O3−CdSe interface of a thin-film transistor is investigated in the frequency range 30 Hz-30 kHz under weak depletion and accumulation.
The surface states are, most likely, located in the insulator Al2O3 with a concentration varying from 4·1018 to 1019 cm−3 eV−1. The surface states have a negligible influence on the thin-film transistor operation. 相似文献
22.
Using an integral theory of grating diffraction we calculate efficiencies greater than 100% if a coating with gain is taken into account. A connection with guided modes is conjectured. The application in optical computing seems to be possible. 相似文献
23.
R. F. Bikbaev 《Theoretical and Mathematical Physics》1989,80(3):1004-1006
Physics and Mathematics Division with Computational Center of the Bashkir Branch of the USSR Academy of Sciences. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 80, No. 3, pp. 470–473, September, 1989. 相似文献
24.
25.
In this paper, the authors studied certain properties of the estimate of Liang and Krishnaiah (1985, J. Multivariate Anal. 16, 162–172) for multivariate binary density. An alternative shrinkage estimate is also obtained. The above results are generalized to general orthonormal systems. 相似文献
26.
J. Berny 《The Journal of the Operational Research Society》1989,40(12):1121-1127
This paper presents an alternative to the beta continuous probability distribution for risk analysis. Particular attention has been given to two major applications of distributions, namely project management risk and critical path analysis (PERT). In conjunction with the beta, the triangular and normal distributions are frequently employed in order to give sufficient robustness to risk analysis. The beta distribution, as used in PERT, has a major theoretical implementation flaw. The new distribution was developed to give a possible alternative method of assessing risk. It is shown that the requirement to estimate the most pessimistic variate may be replaced by the probability to exceed the mode. Proposals for other simplifications in risk analysis are discussed. Practical means to validate the most appropriate distributions for risk analysis are outlined, and a cost-data case study is included. 相似文献
27.
28.
We consider the growth of a spherical crystal in a supersaturatedsolution. In the first part, existence and uniqueness resultsfor radially symmetric growth are obtained, provided that thesupersaturation is not too large; conversely, when the far-fieldsupersaturation exceeds a critical value, it is shown that theradially symmetric solution ceases to exist in finite time.In the second part, we examine the linear stability of a radiallysymmetric similarity solution (in which the radius grows ast?) to shape perturbations. The results are compared with previousquasi-static analyses, and, in particular, the critical radiusat which the crystal becomes unstable is found to be largerfor small supersaturations, but smaller for large supersaturations,than those predicted by the quasi-static analysis 相似文献
29.
30.