全文获取类型
收费全文 | 375034篇 |
免费 | 3122篇 |
国内免费 | 1698篇 |
专业分类
化学 | 170845篇 |
晶体学 | 4972篇 |
力学 | 20631篇 |
综合类 | 61篇 |
数学 | 74868篇 |
物理学 | 108477篇 |
出版年
2020年 | 1799篇 |
2019年 | 1948篇 |
2018年 | 18830篇 |
2017年 | 19382篇 |
2016年 | 12237篇 |
2015年 | 3999篇 |
2014年 | 4104篇 |
2013年 | 9724篇 |
2012年 | 14550篇 |
2011年 | 28718篇 |
2010年 | 17478篇 |
2009年 | 17740篇 |
2008年 | 23634篇 |
2007年 | 28422篇 |
2006年 | 9000篇 |
2005年 | 15027篇 |
2004年 | 11429篇 |
2003年 | 10969篇 |
2002年 | 8242篇 |
2001年 | 7145篇 |
2000年 | 5680篇 |
1999年 | 3890篇 |
1998年 | 3302篇 |
1997年 | 3198篇 |
1996年 | 3360篇 |
1995年 | 2855篇 |
1994年 | 2890篇 |
1993年 | 2771篇 |
1992年 | 2985篇 |
1991年 | 3049篇 |
1990年 | 2858篇 |
1989年 | 2784篇 |
1988年 | 2740篇 |
1987年 | 2674篇 |
1986年 | 2678篇 |
1985年 | 3484篇 |
1984年 | 3556篇 |
1983年 | 2993篇 |
1982年 | 3227篇 |
1981年 | 2969篇 |
1980年 | 2784篇 |
1979年 | 2971篇 |
1978年 | 3205篇 |
1977年 | 3118篇 |
1976年 | 3183篇 |
1975年 | 2896篇 |
1974年 | 3012篇 |
1973年 | 3098篇 |
1972年 | 2405篇 |
1971年 | 1899篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
L. A. Khalfin 《Journal of Mathematical Sciences》1987,36(5):616-626
The article surveys the main results of the statistical approach to the solution of ill-posed problems of mathematical physics, in application to specific ill-posed inverse problems in geophysics.Invited paper presented at the International Seminar on Mathematical Foundations of the Interpretation of Geophysical Fields, Moscow, May–June 1972.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 79, pp. 67–81, 1978. 相似文献
32.
Alcindo A. Dos Santos Renan S. Ferrarini Jefferson L. Princival João V. Comasseto 《Tetrahedron letters》2006,47(50):8933-8935
A masked lithium homoenolate, generated by tellurium/lithium exchange, was reacted with epoxides. The lithium compound was also converted into other organometallics such as Grignard, and cuprates and the reactivity of those organometallics with epoxides was evaluated. The same building block was employed in the synthesis of (+/−)-frontalin. 相似文献
33.
Mark L. Agranovsky E. K. Narayanan 《Proceedings of the American Mathematical Society》2006,134(7):2117-2123
A test for a function to be a solution of an elliptic PDE is given in terms of extensions, as solutions, from the boundaries inside the domains belonging to an isotopic family. It generalizes a result of Ehrenpreis for spheres moved along a straight line.
34.
Data Envelopment Analysis (DEA) offers a piece-wise linear approximation of the production frontier. The approximation tends to be poor if the true frontier is not concave, eg in case of economies of scale or of specialisation. To improve the flexibility of the DEA frontier and to gain in empirical fit, we propose to extend DEA towards a more general piece-wise quadratic approximation, called Quadratic Data Envelopment Analysis (QDEA). We show that QDEA gives statistically consistent estimates for all production frontiers with bounded Hessian eigenvalues. Our Monte-Carlo simulations suggest that QDEA can substantially improve efficiency estimation in finite samples relative to standard DEA models. 相似文献
35.
36.
A. L. Apanasenko A. V. Kuznichenko Yu. B. Govyadovskii V. G. Yakunin 《Journal of Applied Spectroscopy》1991,54(3):271-276
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 3, pp. 438–444, March, 1991. 相似文献
37.
Rainer Löwen 《Journal of Geometry》1989,36(1-2):110-116
We prove that a spread S over a locally compact nondlscrete field F defines a topological translation plane if and only if the spread is compact. For F=R, this is implicit in Breuning's thesis [Bre], cf. [B 2]. For the proof, we describe the point set of the projective translation plane as a quotient space of some projective space, with identifications taking place in one hyperplane. This is new even for F=R. 相似文献
38.
The quantitative rainbow schlieren deflectometry (RSD) technique was applied to measure temperature and oxygen concentration in an axisymmetric hydrogen gas-jet diffusion flame burning in quiescent air at fuel jet exit Reynolds number of 70. Schlieren measurements were compared with conventional measurements using a thermocouple and a gas-sampling probe. Good agreement between the two measurement techniques was achieved on the fuel-lean side of the flame. 相似文献
39.
L. Aggoun 《Mathematical and Computer Modelling》2002,36(11-13)
In this paper, finite-dimensional recursive filters for space-time Markov random fields are derived. These filters can be used with the expectation maximization (EM) algorithm to yield maximum likelihood estimates of the parameters of the model. 相似文献
40.