全文获取类型
收费全文 | 35663篇 |
免费 | 1192篇 |
国内免费 | 71篇 |
专业分类
化学 | 24441篇 |
晶体学 | 243篇 |
力学 | 697篇 |
数学 | 5103篇 |
物理学 | 6442篇 |
出版年
2023年 | 282篇 |
2022年 | 302篇 |
2021年 | 513篇 |
2020年 | 610篇 |
2019年 | 575篇 |
2018年 | 771篇 |
2017年 | 703篇 |
2016年 | 1384篇 |
2015年 | 1125篇 |
2014年 | 1147篇 |
2013年 | 2348篇 |
2012年 | 2524篇 |
2011年 | 2769篇 |
2010年 | 1598篇 |
2009年 | 1282篇 |
2008年 | 2321篇 |
2007年 | 2253篇 |
2006年 | 2024篇 |
2005年 | 1812篇 |
2004年 | 1475篇 |
2003年 | 1135篇 |
2002年 | 1014篇 |
2001年 | 701篇 |
2000年 | 616篇 |
1999年 | 442篇 |
1998年 | 350篇 |
1997年 | 255篇 |
1996年 | 379篇 |
1995年 | 249篇 |
1994年 | 241篇 |
1993年 | 291篇 |
1992年 | 268篇 |
1991年 | 183篇 |
1990年 | 156篇 |
1989年 | 131篇 |
1988年 | 129篇 |
1987年 | 131篇 |
1986年 | 131篇 |
1985年 | 199篇 |
1984年 | 172篇 |
1983年 | 132篇 |
1982年 | 121篇 |
1981年 | 119篇 |
1980年 | 93篇 |
1979年 | 104篇 |
1978年 | 97篇 |
1977年 | 88篇 |
1976年 | 81篇 |
1975年 | 72篇 |
1973年 | 90篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Albo Carlos Cavalheiro 《Applications of Mathematics》2006,51(6):619-628
In the paper we study the equation L
u
= f, where L is a degenerate elliptic operator, with Neumann boundary condition in a bounded open set μ. We prove existence and uniqueness
of solutions in the space H(μ) for the Neumann problem. 相似文献
3.
Complementary regioselective esterification of non-reducing oligosaccharides catalyzed by different hydrolases 总被引:1,自引:0,他引:1
The enzymatic transesterification of several tri- and tetrasaccharides with vinyl laurate is described. The lipases from Candida antarctica B (Novozym 435) and Thermomyces lanuginosus (Lipozyme TL IM) and the alkaline protease from Bacillus licheniformis (subtilisin Carlsberg) have been used with each carbohydrate to obtain different regioisomers. By using the sugars in their amorphous form, complete solubility is achieved in the reaction media (tert-butanol/pyridine mixtures for the lipases and pyridine for the protease) and high isolated yields of the corresponding monoesters are obtained. Good to excellent regioselectivity is observed for all the enzymes, showing a final complementary picture respect to the primary hydroxyls of the oligosaccharides studied. 相似文献
4.
Lubomír Kubáček 《Applications of Mathematics》2006,51(6):565-582
Some remarks to problems of point and interval estimation, testing and problems of outliers are presented in the case of multivariate
regression model.
This work was supported by the Council of Czech Government J14/98:153100011. 相似文献
5.
Ricardo Celorrio Vı́ctor Domínguez Francisco-Javier Sayas 《Comptes Rendus Mathematique》2002,334(10):923-926
In this work we study the solution of Laplace's equation in a domain with holes by an iteration consisting of splitting the problem in an exterior one, around the holes, plus an interior problem in the unholed domain. We show the existence of a decomposition of the solution when the exterior problem is represented by means of a single-layer protential. Also, for the three-dimensional case and with some adjustments for the two-dimensional case, we prove convergence of the method by writing the iteration as a Jacobi iteration for an operator equation and studying the spectrum of the iteration operator. To cite this article: R. Celorrio et al., C. R. Acad. Sci. Paris, Ser. I 334 (2002) 923–926. 相似文献
6.
Marcelo Queiroz Joaquim Jú dice Carlos Humes Jr.. 《Mathematics of Computation》2004,73(248):1849-1863
In this paper the Eigenvalue Complementarity Problem (EiCP) with real symmetric matrices is addressed. It is shown that the symmetric (EiCP) is equivalent to finding an equilibrium solution of a differentiable optimization problem in a compact set. A necessary and sufficient condition for solvability is obtained which, when verified, gives a convenient starting point for any gradient-ascent local optimization method to converge to a solution of the (EiCP). It is further shown that similar results apply to the Symmetric Generalized Eigenvalue Complementarity Problem (GEiCP). Computational tests show that these reformulations improve the speed and robustness of the solution methods.
7.
Mart Abel 《Rendiconti del Circolo Matematico di Palermo》2005,54(3):409-429
It is shown, that the category ℰ
A
(X) ofA-bundles over a topological spaceX is an additive pseudo-Abelian category for each Waelbroeck algebraA.
This research was supported by Greek State Scholarship Foundation and Estonian Science Foundation grant 6205. 相似文献
8.
Ana Luísa Daniel‐da‐Silva João Carlos Moura Bordado José Miguel Martín‐Martínez 《Journal of Polymer Science.Polymer Physics》2007,45(22):3034-3045
The degree of phase separation in several moisture‐cured poly(urethane urea)s (PUUs) was studied by FTIR spectroscopy, wide angle X‐ray diffraction (WAXD), and temperature‐modulated differential scanning calorimetry (TMDSC). This latter technique was shown to be particularly useful in analysing the degree of phase separation in PUU polymers. Both phase mixing and phase segregation coexisted in the PUUs and the degree of phase separation increased as the urea hard segment (HS) content in the PUU increased. The maximum solubility of urea HSs into the polyol soft segments (SSs) was achieved for 50 wt % urea HS content in diol‐based PUUs, whereas for triol‐based PUUs the highest solubility between HS and SS was reached for lower urea HS amount. Finally, the higher the urea HS content the higher the extent of phase separation in the PUU. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3034–3045, 2007 相似文献
9.
Monika Goikoetxea María J. Barandiaran José M. Asua 《Journal of polymer science. Part A, Polymer chemistry》2007,45(24):5838-5846
The mechanisms involved in the formation of n‐butanol during the synthesis of butyl acrylate containing latices were investigated. The experimental results showed that neither the hydrolysis of butyl acrylate nor of the ester bond in the butyl acrylate segments of the polymer played a major role in the formation of n‐butanol, which was mainly generated from the polymer backbone, by transfer reactions to polymer chain followed by cyclization. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5838–5846, 2007 相似文献
10.