全文获取类型
收费全文 | 14944篇 |
免费 | 2009篇 |
国内免费 | 1573篇 |
专业分类
化学 | 5483篇 |
晶体学 | 385篇 |
力学 | 2472篇 |
综合类 | 141篇 |
数学 | 2757篇 |
物理学 | 7288篇 |
出版年
2024年 | 25篇 |
2023年 | 148篇 |
2022年 | 341篇 |
2021年 | 392篇 |
2020年 | 417篇 |
2019年 | 346篇 |
2018年 | 383篇 |
2017年 | 516篇 |
2016年 | 601篇 |
2015年 | 525篇 |
2014年 | 793篇 |
2013年 | 1416篇 |
2012年 | 842篇 |
2011年 | 1046篇 |
2010年 | 946篇 |
2009年 | 1023篇 |
2008年 | 908篇 |
2007年 | 977篇 |
2006年 | 836篇 |
2005年 | 697篇 |
2004年 | 671篇 |
2003年 | 575篇 |
2002年 | 491篇 |
2001年 | 413篇 |
2000年 | 395篇 |
1999年 | 390篇 |
1998年 | 328篇 |
1997年 | 255篇 |
1996年 | 228篇 |
1995年 | 185篇 |
1994年 | 180篇 |
1993年 | 202篇 |
1992年 | 176篇 |
1991年 | 122篇 |
1990年 | 112篇 |
1989年 | 96篇 |
1988年 | 107篇 |
1987年 | 79篇 |
1986年 | 54篇 |
1985年 | 55篇 |
1984年 | 45篇 |
1983年 | 28篇 |
1982年 | 38篇 |
1981年 | 33篇 |
1980年 | 16篇 |
1979年 | 23篇 |
1978年 | 17篇 |
1977年 | 10篇 |
1976年 | 7篇 |
1974年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
991.
High-temperature generalized synthesis of stable ordered mesoporous silica-based materials by using fluorocarbon-hydrocarbon surfactant mixtures 总被引:4,自引:0,他引:4
992.
Sanghyun Cho 《Journal of Mathematical Analysis and Applications》2003,283(2):386-397
Let Ω be a smoothly bounded pseudoconvex domain in and let be a point of finite type. We also assume that the Levi form of bΩ is comparable in a neighborhood of z0. Then we get a quantity which bounds from above and below the Bergman kernel function in a small constant and large constant sense. 相似文献
993.
We discuss integral transformations of the QCD renormalization-invariant coupling (running coupling constant). Special attention is paid to the Fourier transformation, i.e., to the transition from the space–time to the energy–momentum representation. Our first conclusion is that the condition for the possibility of such a transition provides one more argument against the real existence of unphysical singularities observed in the perturbative QCD. The second conclusion relates to a way to translate some singular long-wave asymptotic behaviors to the infrared region of transferred momenta. Such a transition must be performed with the Tauberian theorem taken into account. This comment relates to the recent ALPHA collaboration results on the asymptotic behavior of the QCD effective coupling obtained by numerical lattice simulation. 相似文献
994.
Finite element approximation of spectral problems with Neumann boundary conditions on curved domains
This paper deals with the finite element approximation of the spectral problem for the Laplace equation with Neumann boundary conditions on a curved nonconvex domain . Convergence and optimal order error estimates are proved for standard piecewise linear continuous elements on a discrete polygonal domain in the framework of the abstract spectral approximation theory.
995.
BaoShanWANG JiPingZHANG 《数学学报(英文版)》2003,19(1):29-34
In this paper,we shall mainly study the p-solvable finite group in terms of p-local rank,and a group theoretic characterization will be given of finite p-solvabel groups with p-local rank two.Theorem A Let G be a finite p-solvable group with p-local rank plr(G)=2 and Op(G)=1.If P is a Sylow p-subgrounp of G,then P has a normal subgroup Q such that P/Q is cyclic or a generalized quaternion 2-group and the p-rank of Q is at most two.Theorem B Let G be a finite p-solvable group with Op(G)=1.Then the p-length lp(G)≤plr(G);if in addition plr(G)=lp (G) and p≥5 is odd,then plr(G)=0 or 1. 相似文献
996.
We propose the novel preparation method, Self-seeding Process, based on the following concept for low temperature crystallization of oxide films. Introduction of desirable inhomogeneity should give lowering of a crystallization temperature through heterogeneous nucleation accompanied with reduced activation energy. We carried out inspection of the above concept through use of PZT films. PZT gel films with the desirable inhomogeneity of microstructure were prepared, and their crystallization behaviors was examined. The PZT film was successfully crystallized at 500°C by the self-seeding process. The single phase (001) oriented PZT film with 0.55 m in thickness was obtained at 550°C for 5 min. The self-seeding process by microstructure control is efficient for the low temperature process of the oxide thin film. 相似文献
997.
Let G be a finite group written multiplicatively and k a positive integer. If X is a non-empty subset of G, write X
2 = |xy | x, y X . We say that G has the small square property on k-sets if |X
2| < k
2 for any k-element subset X of G. For each group G, there is a unique m = m
G
such that G has the small square property on (m + 1)-sets but not on m-sets. In this paper we show that given any positive integer d, there is a finite group G with m
G
= d. 相似文献
998.
Emilio Carrizosa Horst W. Hamacher Rolf Klein Stefan Nickel 《Journal of Global Optimization》2000,18(2):195-210
It is well-known that some of the classical location problems with polyhedral gauges can be solved in polynomial time by finding a finite dominating set, i.e. a finite set of candidates guaranteed to contain at least one optimal location.In this paper it is first established that this result holds for a much larger class of problems than currently considered in the literature. The model for which this result can be proven includes, for instance, location problems with attraction and repulsion, and location-allocation problems.Next, it is shown that the approximation of general gauges by polyhedral ones in the objective function of our general model can be analyzed with regard to the subsequent error in the optimal objective value. For the approximation problem two different approaches are described, the sandwich procedure and the greedy algorithm. Both of these approaches lead - for fixed - to polynomial approximation algorithms with accuracy for solving the general model considered in this paper. 相似文献
999.
In this paper we construct elliptic boundary value problems whose standard finite element approximations converge arbitrarily slowly in the energy norm, and show that adaptive procedures cannot improve this slow convergence. We also show that the -norm and the nodal point errors converge arbitrarily slowly. With the -norm two cases need to be distinguished, and the usual duality principle does not characterize the error completely. The constructed elliptic problems are one dimensional.
1000.
We investigate certain finite subgroups of , where is a finite nilpotent group. Such a group gives rise to a -module; we study the characters of these modules to limit the structure of . We also exhibit some exotic subgroups .