全文获取类型
收费全文 | 10224篇 |
免费 | 771篇 |
国内免费 | 1855篇 |
专业分类
化学 | 9530篇 |
晶体学 | 94篇 |
力学 | 168篇 |
综合类 | 70篇 |
数学 | 1247篇 |
物理学 | 1741篇 |
出版年
2024年 | 33篇 |
2023年 | 128篇 |
2022年 | 263篇 |
2021年 | 294篇 |
2020年 | 308篇 |
2019年 | 303篇 |
2018年 | 282篇 |
2017年 | 286篇 |
2016年 | 354篇 |
2015年 | 374篇 |
2014年 | 401篇 |
2013年 | 805篇 |
2012年 | 607篇 |
2011年 | 559篇 |
2010年 | 486篇 |
2009年 | 650篇 |
2008年 | 631篇 |
2007年 | 682篇 |
2006年 | 622篇 |
2005年 | 559篇 |
2004年 | 506篇 |
2003年 | 461篇 |
2002年 | 366篇 |
2001年 | 300篇 |
2000年 | 305篇 |
1999年 | 293篇 |
1998年 | 267篇 |
1997年 | 250篇 |
1996年 | 200篇 |
1995年 | 192篇 |
1994年 | 157篇 |
1993年 | 156篇 |
1992年 | 138篇 |
1991年 | 90篇 |
1990年 | 77篇 |
1989年 | 47篇 |
1988年 | 52篇 |
1987年 | 49篇 |
1986年 | 49篇 |
1985年 | 43篇 |
1984年 | 34篇 |
1983年 | 13篇 |
1982年 | 31篇 |
1981年 | 34篇 |
1980年 | 27篇 |
1979年 | 25篇 |
1978年 | 13篇 |
1977年 | 10篇 |
1976年 | 11篇 |
1974年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
In this paper a class of impulsive differential inclusions is investigated. The existence of solution bundle is proved. And we also construct a nonlinear semigroup of operators on cb(E) (closed-bounded subset of E) to describe the set of attainable states. 相似文献
62.
Chin-Yuan Hu 《Journal of Mathematical Analysis and Applications》2007,328(1):201-219
Recently we established Matysiak and Szablowski's conjecture [V. Matysiak, P.J. Szablowski, Theory Probab. Appl. 45 (2001) 711-713] about a lower bound of real-valued characteristic functions. In this paper, applying an alternative approach we are able to give explicitly the ranges of argument for which the obtained inequalities hold true for general characteristic functions. 相似文献
63.
This paper deals with a model of time-dependent double diffusive convection in Darcy flow. In particular it is concerned with the spatial decay of solutions when the flow is confined to a semi-infinite cylinder. Decay bounds for an energy expression are derived. 相似文献
64.
Summary The enzymes a-amylase, invertase and glucoamylase were immobilized on acid activated montmorillonite using two techniques,
viz. adsorption and covalent binding, and their activities were tested in a batch and packed-bed reactor and were compared. The
packed-bed reactor showed an improved performance for all immobilized enzymes, which was attributed to lowering of diffusional
restrictions to mass transfer. Lower activity in case of batch reactor for immobilized invertase was due to a combined effect
of loss of native conformation of enzyme on account of immobilization and mass transfer resistances due to improper diffusion
of substrate to the active site of enzyme. For immobilized glucoamylase, the packed-bed reactor demonstrated exceptionally
high activity that was very close to the free enzyme. Covalently bound glucoamylase showed higher activity than the free enzyme. 相似文献
65.
现场拉曼光谱研究乙腈在金电极上的解离吸附行为 总被引:2,自引:1,他引:1
利用共焦显微拉曼系统、结合合适的电极表面粗糙方法研究了非水体系 0 1mol/LLiClO4 /CH3CN溶液中 ,乙腈分子在金表面的吸附和解离行为。结果表明非水体系中乙腈可在金表面发生还原反应 ,产物CN- 离子与电极表面作用形成的表面配合物可在较宽的电位区间吸附于电极表面。溶液中的微量水、激光照射以及电极电位均对该反应有较大的影响。通过拉曼谱图的比较得出乙腈分子解离出的CN- 在金电极表面比在银电极表面有更强的吸附作用。 相似文献
66.
67.
Th. Friedrich I. Kath A. Moroianu U. Semmelmann 《Journal of Geometry and Physics》1997,23(3-4):259-286
A nearly parallel G2-structure on a seven-dimensional Riemannian manifold is equivalent to a spin structure with a Killing spinor. We prove general results about the automorphism group of such structures and we construct new examples. We classify all nearly parallel G2-manifolds with large symmetry group and in particular all homogeneous nearly parallel G2-structures. 相似文献
68.
We investigate the propeties of differential algebras generated by an operator d satisfying the property dN = 0 instead of d2 = 0 as in the usual case. Several examples of realizations of such differential algebras are given, either in the context of ZN-graded N × N matrix algebras, or as a generalized differential calculus on manifolds. 相似文献
69.
Alain Lascoux 《Bulletin des Sciences Mathématiques》2006,130(4):354-359
Eliminating the arbitrary coefficients in the equation of a generic plane curve of order n by computing sufficiently many derivatives, one obtains a differential equation. This is a projective invariant. The first one, corresponding to conics, has been obtained by Monge. Sylvester, Halphen, Cartan used invariants of higher order. The expression of these invariants is rather complicated, but becomes much simpler when interpreted in terms of symmetric functions. 相似文献
70.
In CZE, the adsorption of the proteins on the capillary wall is a common problem. This paper describes the simple method of utilizing zwitterionic buffer additives to improve the separation of proteins in untreated fused silica capillaries at neutral pH. Three kinds of zwitterion are evaluated in the separation of acidic, neutral, and basic proteins, including their effect on protein efficiency, mobility, separation, and resolution; the difference between the effects of the different additives are also highlighted. The method has proved to be a possible means of reducing protein adsorption, especially for basic proteins. 相似文献