全文获取类型
收费全文 | 41521篇 |
免费 | 1507篇 |
国内免费 | 1452篇 |
专业分类
化学 | 29547篇 |
晶体学 | 326篇 |
力学 | 799篇 |
综合类 | 10篇 |
数学 | 5746篇 |
物理学 | 8052篇 |
出版年
2023年 | 298篇 |
2022年 | 527篇 |
2021年 | 708篇 |
2020年 | 677篇 |
2019年 | 688篇 |
2018年 | 792篇 |
2017年 | 773篇 |
2016年 | 1502篇 |
2015年 | 1214篇 |
2014年 | 1282篇 |
2013年 | 2782篇 |
2012年 | 3035篇 |
2011年 | 3263篇 |
2010年 | 1885篇 |
2009年 | 1924篇 |
2008年 | 2536篇 |
2007年 | 2475篇 |
2006年 | 2178篇 |
2005年 | 2066篇 |
2004年 | 2113篇 |
2003年 | 1548篇 |
2002年 | 1425篇 |
2001年 | 911篇 |
2000年 | 776篇 |
1999年 | 589篇 |
1998年 | 482篇 |
1997年 | 385篇 |
1996年 | 463篇 |
1995年 | 344篇 |
1994年 | 306篇 |
1993年 | 360篇 |
1992年 | 308篇 |
1991年 | 220篇 |
1990年 | 212篇 |
1989年 | 173篇 |
1988年 | 172篇 |
1987年 | 158篇 |
1986年 | 161篇 |
1985年 | 261篇 |
1984年 | 230篇 |
1983年 | 172篇 |
1982年 | 148篇 |
1981年 | 153篇 |
1980年 | 119篇 |
1979年 | 130篇 |
1978年 | 105篇 |
1977年 | 103篇 |
1976年 | 96篇 |
1975年 | 93篇 |
1973年 | 99篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
Testing goodness of fit for the distribution of errors in multivariate linear models 总被引:2,自引:0,他引:2
M.D. Jimnez Gamero J. Muoz García R. Pino Mejías 《Journal of multivariate analysis》2005,95(2):301-322
In this paper, to test goodness of fit to any fixed distribution of errors in multivariate linear models, we consider a weighted integral of the squared modulus of the difference between the empirical characteristic function of the residuals and the characteristic function under the null hypothesis. We study the limiting behaviour of this test statistic under the null hypothesis and under alternatives. In the asymptotics, the rank of the design matrix is allowed to grow with the sample size. 相似文献
62.
63.
If a and b are trace-class operators, and if u is a partial isometry, then , where ∥⋅∥1 denotes the norm in the trace class. The present paper characterises the cases of equality in this Young inequality, and
the characterisation is examined in the context of both the operator and the Hilbert–Schmidt forms of Young's inequality.
Received: 20 December 2001 / Revised version: 11 July 2002 / Published online: 10 February 2003
Mathematics Subject Classification (2000): 47A63, 15A60 相似文献
64.
Bruzón M. S. Gandarias M. L. Muriel C. Ramírez J. Saez S. Romero F. R. 《Theoretical and Mathematical Physics》2003,137(1):1367-1377
We use the classical and nonclassical methods to obtain symmetry reductions and exact solutions of the (2+1)-dimensional integrable Calogero–Bogoyavlenskii–Schiff equation. Although this (2+1)-dimensional equation arises in a nonlocal form, it can be written as a system of differential equations and, in potential form, as a fourth-order partial differential equation. The classical and nonclassical methods yield some exact solutions of the (2+1)-dimensional equation that involve several arbitrary functions and hence exhibit a rich variety of qualitative behavior. 相似文献
65.
66.
F. Tercero J. A. López Fernández E. García L. de Haro M. C. Carter A. Barcia B. Galocha J. L. Besada 《International Journal of Infrared and Millimeter Waves》2003,24(5):669-681
The Beam Mode Expansion (BME) approach for corrugated conical feed horn plus meniscus lens is presented. This approach is useful for providing the radiation pattern as it propagates through an optical system. A developed theoretical model has been verified measuring near and far field of a built horn and lens. These results have been used for designing the optical system of a Cassegrain antenna at 100GHz using the fundamental Gaussian beam mode (GBM) of the new approach. Multimode analysis has been performed with the pre-designed system in order to test the fundamental GBM results. 相似文献
67.
José M. Arrieta Neus Cónsul Anibal Rodríguez-Bernal 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2004,23(2):1-14
We prove the existence of nonconstant stable stationary
solutions of
an evolution problem with a nonlinear reaction acting on the
boundary. These solutions present layers at certain points of the
boundary. We also study the behavior of these solutions as the small
parameter appearing in the equation approaches zero and show some
stability properties of the profiles given by these equilibrium
solutions. 相似文献
68.
P. Pellegrino B. Garrido C. García R. Ferr J. A. Moreno J. R. Morante 《Physica E: Low-dimensional Systems and Nanostructures》2003,16(3-4):424
The ability of surface passivation to enhance the photoluminescence (PL) emission of Si nanocrystals in SiO2 has been investigated. Silicon precipitation in implanted samples takes place in a time scale of few minutes at 1100°C. For longer annealing at the same temperature, the PL intensity of the Si nanocrystals increases and eventually reaches saturation, while it correlates inversely with the amount of Si dangling bonds at the Si–SiO2 interface (Pb centers), as measured by electron spin resonance. This combined behavior is independent on the silica matrix properties, implantation profiles and annealing atmosphere and duration. The observation that the light emission enhancement is directly related to the annealing of Pb centers is confirmed by treatment in forming gas. This mild hydrogenation at much lower temperature (450°C) leads to a complete passivation of the Pb defects, increasing at the same time the PL yield and the lifetime. 相似文献
69.
70.
The effects of n‐hexanol, n‐pentanol, and n‐butanol on the critical micelle concentration (cmc), on the micellar ionization degree (α), and on the rate of the reaction methyl 4‐nitrobenzenesulfonate + Br? have been investigated in cetyltrimethylammonium bromide (CTAB) aqueous solutions. An increase in the alcohol concentration present in the solution produces a decrease in the cmc and an increase in the micellar ionization degree. Kinetic data show that the observed rate constant decreases as alcohol concentration increases. This result was rationalized by considering variations in the equilibrium binding constant of the methyl 4‐nitrobenzenesulfonate molecules to the micelles, variations in the interfacial bromide ion concentration, and variations in the characteristics of the water–alcohol bulk phase provoked by the presence of alcohols. When these operative factors are considered, kinetic data in this and other works show that the second‐order rate constants in the micellar pseudophases of water–alcohol micellar solutions are quite similar to those estimated in the absence of alcohols. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 634–641, 2004 相似文献