全文获取类型
收费全文 | 2793篇 |
免费 | 88篇 |
国内免费 | 72篇 |
专业分类
化学 | 183篇 |
晶体学 | 1篇 |
力学 | 13篇 |
综合类 | 1篇 |
数学 | 2538篇 |
物理学 | 217篇 |
出版年
2023年 | 9篇 |
2022年 | 11篇 |
2021年 | 9篇 |
2020年 | 12篇 |
2019年 | 61篇 |
2018年 | 71篇 |
2017年 | 51篇 |
2016年 | 54篇 |
2015年 | 30篇 |
2014年 | 92篇 |
2013年 | 255篇 |
2012年 | 111篇 |
2011年 | 224篇 |
2010年 | 212篇 |
2009年 | 275篇 |
2008年 | 293篇 |
2007年 | 231篇 |
2006年 | 158篇 |
2005年 | 87篇 |
2004年 | 97篇 |
2003年 | 77篇 |
2002年 | 39篇 |
2001年 | 28篇 |
2000年 | 32篇 |
1999年 | 57篇 |
1998年 | 37篇 |
1997年 | 35篇 |
1996年 | 39篇 |
1995年 | 47篇 |
1994年 | 32篇 |
1993年 | 27篇 |
1992年 | 15篇 |
1991年 | 11篇 |
1990年 | 7篇 |
1989年 | 8篇 |
1988年 | 14篇 |
1987年 | 11篇 |
1986年 | 6篇 |
1985年 | 10篇 |
1984年 | 10篇 |
1983年 | 4篇 |
1982年 | 11篇 |
1981年 | 7篇 |
1980年 | 10篇 |
1979年 | 9篇 |
1978年 | 9篇 |
1977年 | 10篇 |
1976年 | 5篇 |
1974年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有2953条查询结果,搜索用时 312 毫秒
21.
We consider the support problem of Erdös in the context of l-adic representations of the absolute Galois group of a number field. Main applications of the results of the paper concern Galois cohomology of the Tate module of abelian varieties with real and complex multiplications, the algebraic K-theory groups of number fields and the integral homology of the general linear group of rings of integers. We answer the question of Corrales-Rodrigáñez and Schoof concerning the support problem for higher dimensional abelian varieties. 相似文献
22.
In this paper the neo-classical economic Solow-Swan model (1956) has been improved replacing its Malthusian manpower law with
the Verhulst (logistic) one. The relevant ordinary differential equation for the ratio capital/work has been then integrated
in closed form via the Hypergeometric function2
F
1. The logistic growth injection for the manpower is detected to induce a more slow dynamics onto the Solow-Swan system, which
keeps its stability. Increasing developments are displayed as the technologic progress rises. Further sceneries are tested
and the congruence of the new solution with the classical one is shown switching to zero the selflimitation coefficent in
the logistic law.
Research supported by MURST grant:Metodi matematici in economia 相似文献
23.
Ewa Stró?yna 《Journal of Differential Equations》2003,193(1):239-259
We solve completely the problem of classification of germs of complex planar vector fields with nilpotent singularity with respect to formal orbital equivalence. 相似文献
24.
Summary.
This paper is concerned with a high order convergent
discretization for the semilinear reaction-diffusion problem:
,
for , subject to ,
where .
We assume that on
, which
guarantees uniqueness of a solution to
the problem. Asymptotic properties of
this solution are discussed. We consider a
polynomial-based three-point
difference scheme on a simple piecewise
equidistant mesh of Shishkin type.
Existence and local uniqueness of a solution
to the scheme are analysed. We
prove that the scheme is almost fourth order
accurate in the discrete maximum
norm, uniformly in the perturbation parameter
. We present numerical
results in support of this result.
Received February 25, 1994 相似文献
25.
In this paper, by using fixed point theorems in cones, we study the existence of at least one, two and three positive solutions of a nonlinear second-order three-point boundary value problem for dynamic equations on time scales. As an application, we also give some examples to demonstrate our results. 相似文献
26.
CAI Guang-Yu LlU Zhong-Min SHI Ren-Min HE Chang-Qing YANG Li-Xin SUN Cheng-LinDalian Institute of Chemical Physics Acadernia Sinica Dalian Iiaorting 《天然气化学杂志》1995,(2)
A new route named as SDTO method for the synthesis of lightolefins from syngas has been proposed.That is to convert syngas todimethylether and then to convert dimethylether to light olefins.The catalystsfor the two conversion reactions have been developed.For the first reaction,the catulySt was synthesized by the combination of methanol synthesis catalystwith γ-Al_2O_3or zeolites which possesses both metallic and acidic functions.Thecatalyst for the second reaction was modified SAPO-34 molecular sieve.Thevariables of the reactions have also been investigated.The results from theserial connection of the two conversion steps without any separation show thatthe yield of C_2~-C_4~- olefins Could be>100g/(m~3 syngas). 相似文献
27.
In this paper we define and study an extension of the g-Drazin for elements of a Banach algebra and for bounded linear operators based on an isolated spectral set rather than on
an isolated spectral point. We investigate salient properties of the new inverse and its continuity, and illustrate its usefulness
with an application to differential equations. Generalized Mbekhta subspaces are introduced and the corresponding extended
Mbekhta decomposition gives a characterization of circularly isolated spectral sets. 相似文献
28.
Perch Melik-Adamyan 《Complex Analysis and Operator Theory》2007,1(3):423-438
An analog of the Kreĭn–Saakyan formula is derived for any pair of relatively prime self-adjoint extensions of a minimal symmetric
canonical differential operator. This allows us to deduce a trace formula in the matrix case.
I am grateful to Sh. Saakyan for his interest in this work and lively discussion.
Received: December 8, 2006. Accepted: December 30, 2006. 相似文献
29.
A delayed stage-structured predator–prey model with non-monotone functional responses is proposed. It is assumed that immature individuals and mature individuals of the predator are divided by a fixed age, and that immature predators do not have the ability to attack prey. Some new and interesting sufficient conditions are obtained for the global existence of multiple positive periodic solutions of the stage-structured predator–prey model. Our method is based on Mawhin’s coincidence degree and novel estimation techniques for the a priori bounds of unknown solutions to Lx = λNx. An example is given to illustrate the feasibility of our main result. 相似文献
30.
Masahiro Kubo 《Journal of Evolution Equations》2007,7(4):701-717
We study an abstract second order nonlinear evolution equation in a real Hilbert space. We consider time-dependent convex
functions and their subdifferentials operating on the first derivative of the unknown function. Introducing appropriate assumptions
on the convex functions and other data, we prove the existence and uniqueness of a strong solution, and give some applications
of the abstract theorem to hyperbolic variational inequalities with time-dependent constraints.
相似文献