全文获取类型
收费全文 | 331424篇 |
免费 | 3547篇 |
国内免费 | 943篇 |
专业分类
化学 | 165705篇 |
晶体学 | 5422篇 |
力学 | 15608篇 |
综合类 | 10篇 |
数学 | 38926篇 |
物理学 | 110243篇 |
出版年
2021年 | 3158篇 |
2020年 | 3391篇 |
2019年 | 3839篇 |
2018年 | 5293篇 |
2017年 | 5515篇 |
2016年 | 7476篇 |
2015年 | 4209篇 |
2014年 | 7132篇 |
2013年 | 16150篇 |
2012年 | 12510篇 |
2011年 | 14969篇 |
2010年 | 11165篇 |
2009年 | 11026篇 |
2008年 | 13393篇 |
2007年 | 13320篇 |
2006年 | 12222篇 |
2005年 | 10588篇 |
2004年 | 9904篇 |
2003年 | 8767篇 |
2002年 | 8723篇 |
2001年 | 10437篇 |
2000年 | 7691篇 |
1999年 | 5983篇 |
1998年 | 4989篇 |
1997年 | 4828篇 |
1996年 | 4496篇 |
1995年 | 3871篇 |
1994年 | 3824篇 |
1993年 | 3705篇 |
1992年 | 4095篇 |
1991年 | 4310篇 |
1990年 | 4103篇 |
1989年 | 4014篇 |
1988年 | 3785篇 |
1987年 | 3919篇 |
1986年 | 3687篇 |
1985年 | 4633篇 |
1984年 | 4693篇 |
1983年 | 3887篇 |
1982年 | 3977篇 |
1981年 | 3700篇 |
1980年 | 3651篇 |
1979年 | 3915篇 |
1978年 | 3904篇 |
1977年 | 3907篇 |
1976年 | 3881篇 |
1975年 | 3677篇 |
1974年 | 3620篇 |
1973年 | 3657篇 |
1972年 | 2605篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
251.
Using the continuous shape space formalism, we develop an immune system model involving both B lymphocytes and antibody molecules. The binding and cross-linking of receptors on B cells stimulates the cells to divide and, with a lag, to secrete antibody. Using the method of multiple scales, we show how to correctly formulate long-time-scale equations for the population dynamics of B cells, the total antibody concentration, and rate of antibody secretion. We compare our model with previous phenomenological formulations. 相似文献
252.
253.
The Schwinger representation of the SO(8) fermion pair algebra in terms ofd and quasispin vector (u, s, v) bosons is used in deriving a microscopic boson coherent state having both particle-hole and pair excitations. The coherent
state is the exact boson image of the HFB variational solution. We can study the shape phase transition and pairing behaviour
of the nuclear ground states using the coherent states. 相似文献
254.
We consider the growth of a spherical crystal in a supersaturatedsolution. In the first part, existence and uniqueness resultsfor radially symmetric growth are obtained, provided that thesupersaturation is not too large; conversely, when the far-fieldsupersaturation exceeds a critical value, it is shown that theradially symmetric solution ceases to exist in finite time.In the second part, we examine the linear stability of a radiallysymmetric similarity solution (in which the radius grows ast?) to shape perturbations. The results are compared with previousquasi-static analyses, and, in particular, the critical radiusat which the crystal becomes unstable is found to be largerfor small supersaturations, but smaller for large supersaturations,than those predicted by the quasi-static analysis 相似文献
255.
256.
A convenient method is proposed for the synthesis of all the individual methyl ethers of methyl 2-acetamido-2-deoxy-α-D-glucopyranoside based on the partial methylation of 2-acetamido-2-deoxy-α-D-glucopyranoside with dimethyl sulfate in an alkaline medium followed by preparative liquid column chromatography on silica gel of the resulting mixture of methyl ethers. 相似文献
257.
Let V be a hypersurface with an isolated singularity at the origin in ? n+1. It is a natural question to ask when V is defined by weighted homogeneous polynomial or homogeneous polynomial up to biholomorphic change of coordinates. In 1971, a beautiful theorem of Saito gives a necessary and sufficient condition for V to be defined by a weighted homogeneous polynomial. For a two-dimensional isolated hypersurface signularity V, Xu and Yau found a coordinate free characterization for V to be defined by a homogeneous polynomial. Recently Lin and Yau gave necessary and sufficient conditions for a 3-dimensional isolated hypersurface singularity with geometric genus bigger than zero to be defined by a homogeneous polynomial. The purpose of this paper is to prove that Lin-Yau’s theorem remains true for singularities with geometric genus equal to zero. 相似文献
258.
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
259.
S. P. Khekalo 《Journal of Mathematical Sciences》2006,132(1):136-145
Relations between the coefficients of gauge-related deformations and the solutions of a certain system of ordinary nonlinear
differential equations are studied. These coefficients are found in an explicit form. Bibliography: 14 titles.
Dedicated to P. V. Krauklis on the occasion of his seventieth birthday
__________
Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 308, 2004, pp. 235–251. 相似文献
260.
The main result of the paper is a theorem, using which a new proof of Roth’s theorem is obtained, a new solvability criterion
for the matrix equation AX-YB = C is proved, a formula for a particular solution of the latter is derived, and the least of
the orders of square nonsingular matrices containing a given rectangular matrix as a submatrix is determined. Bibliography:
5 titles.
__________
Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 323, 2005, pp. 15–23. 相似文献