全文获取类型
收费全文 | 2138篇 |
免费 | 105篇 |
国内免费 | 13篇 |
专业分类
化学 | 1586篇 |
晶体学 | 10篇 |
力学 | 65篇 |
数学 | 321篇 |
物理学 | 274篇 |
出版年
2024年 | 6篇 |
2023年 | 15篇 |
2022年 | 36篇 |
2021年 | 41篇 |
2020年 | 31篇 |
2019年 | 41篇 |
2018年 | 32篇 |
2017年 | 41篇 |
2016年 | 88篇 |
2015年 | 54篇 |
2014年 | 110篇 |
2013年 | 130篇 |
2012年 | 162篇 |
2011年 | 185篇 |
2010年 | 109篇 |
2009年 | 111篇 |
2008年 | 144篇 |
2007年 | 133篇 |
2006年 | 121篇 |
2005年 | 113篇 |
2004年 | 114篇 |
2003年 | 81篇 |
2002年 | 73篇 |
2001年 | 39篇 |
2000年 | 35篇 |
1999年 | 22篇 |
1998年 | 22篇 |
1997年 | 19篇 |
1996年 | 17篇 |
1995年 | 14篇 |
1994年 | 13篇 |
1993年 | 9篇 |
1992年 | 6篇 |
1991年 | 8篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 17篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 6篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1971年 | 2篇 |
1958年 | 2篇 |
排序方式: 共有2256条查询结果,搜索用时 15 毫秒
61.
Synthesis of grafting silane on a hydro soluble cellulose ether (HPMC) was described. In alkaline medium, this derivate is under gel form. With a decrease of the pH, a self-hardening occurs due to the silanol condensation. For potential biomedical use, we described the silated-HPMC synthesis, the gel behavior after steam sterilization and the parameters of the silanol condensation i.e. pH, silane percentage and temperature. Minimum kinetic of the condensation was observed for pH between 5.5 and 6.5. So temperature catalyzed the reaction and the self-hardening speed was increased by silane percentage. 相似文献
62.
63.
The indirect exchange interaction between localized magnetic moments via virtual excitations from the valence band in intrinsic semiconductors is calculated taking into account the temperature, energy gaps, finite valence bands and effective masses. The inclusion of finite temperature effects changes significantly the phase and magnitude of the oscillations. For small gap semiconductors the oscillatory character and the possibility of ferro-magnetic as well as anti-ferromagnetic coupling are obtained. The exchange interaction oscillates with temperature suggesting interesting applications of this model. 相似文献
64.
Xavier L. Hubaut 《Discrete Mathematics》1975,13(4):357-381
In this paper we have tried to summarize the known results on strongly regular graphs. Both groupal and combinatorial aspects of the theory have been included. We give the list of all known strongly regular graphs and a large bibliography of this subject. 相似文献
65.
The fracture of porous media subjected to a constant load is studied. Contrary to homogeneous solids in which fracture usually happens instantaneously at a well-defined breaking strength, the fracture of a porous medium can occur with a delay, allowing us to quantify the average lifetime of the unbroken material. We show that the average fracture probability, a key property for risk analysis in civil engineering, is given by the probability of crack nucleation. The nucleation process can be understood qualitatively by calculating the activation energy for crack nucleation, taking into account the porosity of the medium. 相似文献
66.
67.
Domínguez M Alvarez R Martras S Farrés J Parés X de Lera AR 《Organic & biomolecular chemistry》2004,2(22):3368-3373
Ring-oxidized retinoids have been synthesized stereoselectively using the Stille cross-coupling reaction. Kinetic constants of mouse class I alcohol dehydrogenase (ADH1) with these retinoids were determined. 相似文献
68.
Using a mathematical framework which provides a generalization of the de Rham complex (well-designed for p-form gauge fields), we have studied the gauge structure and duality properties of theories for free gauge fields transforming in arbitrary irreducible representations of GL(D, ). We have proven a generalization of the Poincaré lemma which enables us to solve the above-mentioned problems in a systematic and unified way. 相似文献
69.
We first present a method to compute the electro-optic tensor from first principles, explicitly taking into account the electronic, ionic and piezoelectric contributions. We then study the nonlinear optic behavior of three paradigmatic ferroelectric oxides. Our calculations reveal the dominant contribution of the soft mode to the electro-optic coefficients in LiNbO3 and BaTiO3 and its minor role in PbTiO3. We identify the coupling between the electric field and the polar atomic displacements along the B-O chains as the origin of the large electro-optic response in perovskite ABO3 compounds. 相似文献
70.
In 1978 De Giorgi formulated the following conjecture. Let be a solution of in all of such that and 0$"> in . Is it true that all level sets of are hyperplanes, at least if ? Equivalently, does depend only on one variable? When , this conjecture was proved in 1997 by N. Ghoussoub and C. Gui. In the present paper we prove it for . The question, however, remains open for . The results for and 3 apply also to the equation for a large class of nonlinearities .