全文获取类型
收费全文 | 58643篇 |
免费 | 13515篇 |
国内免费 | 5399篇 |
专业分类
化学 | 57214篇 |
晶体学 | 760篇 |
力学 | 2104篇 |
综合类 | 370篇 |
数学 | 5145篇 |
物理学 | 11964篇 |
出版年
2024年 | 48篇 |
2023年 | 368篇 |
2022年 | 719篇 |
2021年 | 949篇 |
2020年 | 2023篇 |
2019年 | 3349篇 |
2018年 | 1801篇 |
2017年 | 1497篇 |
2016年 | 4399篇 |
2015年 | 4578篇 |
2014年 | 4748篇 |
2013年 | 5730篇 |
2012年 | 4995篇 |
2011年 | 4439篇 |
2010年 | 4446篇 |
2009年 | 4520篇 |
2008年 | 4156篇 |
2007年 | 3412篇 |
2006年 | 3047篇 |
2005年 | 2820篇 |
2004年 | 2429篇 |
2003年 | 2132篇 |
2002年 | 2971篇 |
2001年 | 2213篇 |
2000年 | 1921篇 |
1999年 | 942篇 |
1998年 | 467篇 |
1997年 | 347篇 |
1996年 | 363篇 |
1995年 | 304篇 |
1994年 | 220篇 |
1993年 | 214篇 |
1992年 | 159篇 |
1991年 | 150篇 |
1990年 | 125篇 |
1989年 | 129篇 |
1988年 | 83篇 |
1987年 | 74篇 |
1986年 | 63篇 |
1985年 | 48篇 |
1984年 | 27篇 |
1983年 | 29篇 |
1982年 | 18篇 |
1981年 | 15篇 |
1980年 | 11篇 |
1979年 | 11篇 |
1976年 | 5篇 |
1974年 | 5篇 |
1972年 | 4篇 |
1936年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
111.
J. Giroire T. Ha‐Duong V. Moumas 《Mathematical Methods in the Applied Sciences》2005,28(13):1527-1552
This article deals with a boundary value problem for Laplace equation with a non‐linear and non‐local boundary condition. This problem comes from petroleum engineering and is used to obtain an estimation of well productivity. The non‐linear and non‐local boundary condition is written on the well boundary. On the outer reservoir boundaries, we have both Dirichlet and Neumann conditions. In this paper, we prove the existence and uniqueness of a solution to this problem. The existence is proved by Schauder theorem and the uniqueness is obtained under more restricted conditions, when the involved operator is a contraction. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
112.
113.
A stochastic approximation algorithm for estimating multichannel coefficients is proposed, and the estimate is proved to converge to the true parameters a.s. up-to a constant scaling factor. The estimate is updated after receiving each new observation, so the output data need not be collected in advance. The input signal is allowed to be dependent and the observation is allowed to be corrupted by noise, but no noise statistics are used in the estimation algorithm. 相似文献
114.
通过用毛细管测量纯水表面张力系数实验,得到管内径d与接触角θ的相对误差之间的关系曲线,由此说明实验测得的表面张力系数α和理论公式相比呈现一定的偏差,并简单地讨论了实验的理想状态与实际情况的差别. 相似文献
115.
You‐Liang Zhao Chuan‐Fu Chen Fu Xi 《Journal of polymer science. Part A, Polymer chemistry》2003,41(14):2156-2165
The atom transfer radical copolymerization of N‐substituted maleimides such as N‐phenylmaleimide (PhMI), N‐cyclohexylmaleimide (ChMI), and N‐butylmaleimide (NBMI) with styrene initiated with dendritic polyarylether 2‐bromoisobutyrates in an ionic liquid, 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([bmim][PF6]), at room temperature and anisole at 110 °C was investigated. The dendritic‐linear block copolymers obtained in ionic liquid possessed well‐defined molecular weight and low polydispersity (1.05 < Mw/Mn < 1.32) and could be used as a macroinitiator for chain‐extension polymerization, suggesting the living nature of the reaction system. The ionic liquids containing catalyst could be recycled in the atom transfer radical polymerization systems without further treatment. Compared with polymerization conducted in anisole, the polymerization in ionic liquid had a stronger tendency for alternation. The tendency for alternation decreased in the order PhMI > NBMI > ChMI in [bmim][PF6] and PhMI > ChMI > NBMI in anisole. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2156–2165, 2003 相似文献
116.
Julien Ferrari Christian Terreaux Tibor Kurtn Attila Szikszai‐Kiss Sndor Antus JeromeD. Msonthi Kurt Hostettmann 《Helvetica chimica acta》2003,86(8):2768-2778
Investigation of the methanol extract of the roots of Gnidia involucrata (Thymelaeaceae) led to the isolation and characterization of two new 3,8″‐biflavonoid diastereoisomers, named GB‐4 ( 6a ) and GB‐4a ( 6b ). Their absolute configurations were determined in mixture by on‐line LC/CD measurements, which also allowed the revision of absolute configurations of the biflavanoids GB‐1 and GB‐2, and the configurational assignment of GB‐3. 相似文献
117.
In this Note, we shall consider the Riemannian distance on loop groups, which will be identified to one introduced by Hino and Ramirez [M. Hino, J.A. Ramirez, Small-time Gaussian behavior of symmetric diffusion semigroups, Ann. Probab. 31 (2003) 1254–1295]. A transportation cost inequality is established. To cite this article: S. Fang, J. Shao, C. R. Acad. Sci. Paris, Ser. I 341 (2005). 相似文献
118.
119.
120.