全文获取类型
收费全文 | 14273篇 |
免费 | 1429篇 |
国内免费 | 1296篇 |
专业分类
化学 | 2880篇 |
晶体学 | 68篇 |
力学 | 1326篇 |
综合类 | 433篇 |
数学 | 7712篇 |
物理学 | 4579篇 |
出版年
2024年 | 24篇 |
2023年 | 110篇 |
2022年 | 243篇 |
2021年 | 321篇 |
2020年 | 318篇 |
2019年 | 321篇 |
2018年 | 303篇 |
2017年 | 364篇 |
2016年 | 421篇 |
2015年 | 303篇 |
2014年 | 567篇 |
2013年 | 891篇 |
2012年 | 611篇 |
2011年 | 831篇 |
2010年 | 840篇 |
2009年 | 1043篇 |
2008年 | 1023篇 |
2007年 | 996篇 |
2006年 | 953篇 |
2005年 | 744篇 |
2004年 | 623篇 |
2003年 | 627篇 |
2002年 | 557篇 |
2001年 | 509篇 |
2000年 | 444篇 |
1999年 | 419篇 |
1998年 | 361篇 |
1997年 | 318篇 |
1996年 | 270篇 |
1995年 | 212篇 |
1994年 | 168篇 |
1993年 | 140篇 |
1992年 | 143篇 |
1991年 | 104篇 |
1990年 | 85篇 |
1989年 | 90篇 |
1988年 | 72篇 |
1987年 | 63篇 |
1986年 | 38篇 |
1985年 | 71篇 |
1984年 | 63篇 |
1983年 | 35篇 |
1982年 | 63篇 |
1981年 | 50篇 |
1980年 | 40篇 |
1979年 | 60篇 |
1978年 | 34篇 |
1977年 | 34篇 |
1976年 | 21篇 |
1973年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Bush连续不可微函数的分形性质 总被引:1,自引:0,他引:1
本文对用递推关系确定的Bush连续不可微函数,找出了迭代函数系(IFS),从而得到它的级数表达式和所具有的自仿射分形的有关性质.最后还计算出函数图象的Hausdorff 维数的准确值. 相似文献
62.
63.
Ekatherina A. Karatsuba 《Numerical Algorithms》2007,45(1-4):127-137
A new approach to the study of the Jaynes–Cummings sum, which determines the atomic inversion in quantum model of a single
two-level atom interacting with a single mode of the quantized radiation field, based on the number theory theorems on approximation
of trigonometric sums is presented.
相似文献
64.
M. Feng 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(3):371-377
The Raman interaction of a ultracold ion trapped with two travelling wave lasers is studied analytically with series solutions,
in the absence of the rotating wave approximation (RWA) and without restrictions of both the Lamb-Dicke limit and the weak
excitation regime. The comparison is made between our solutions and those obtained under the RWA in order to demonstrate the
validity region of the RWA. As a practical example, the preparation of Schr?dinger-cat states is proposed beyond the weak
excitation regime, using our calculations.
Received 12 March 2001 and Received in final form 16 October 2001 相似文献
65.
Summary Campaign results of high-repetition ionospheric soundings, performed at the ionospheric station of Rome using a Digisonde
128P, are presented. We introduce an index derived from run rapid ionograms that can be used to detect oscillations of isodensity
surfaces ofF ionospheric region started by morning solar terminator. 相似文献
66.
现场抽样调查中,由于测量误差的存在,使得所测变量实测值的方差增大,通过增加每个体的测量次数可以控制测量误差,但这样每个体调查费用增大。本文对测量信度R,每个体测量次数m与相应所需的样本含量nm、调查费用Tn的关系进行了探讨,并介绍了如何根据R,及每个体测量费用占其总费用构成比C,确定最佳测量次数m值,以达到最佳控制调查费用的目的,这对我们在大型现场调查中进行经济效益分析具有重大的理论指导意义。 相似文献
67.
T. Charitat B. Fourcade 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,1(3):333-336
An o-ring takes spontaneously the shape of a chair when strong enough torsion is applied in its tangent plane. This state
is metastable, since work has to be done on the o-ring to return to the circular shape. We show that this metastable state
exists in a Hamiltonian where curvature and torsion are coupled via an intrinsic curvature term. If the o-ring is constrained to be planar (2d case), this metastable state displays a kink-anti-kink
pair. This state is metastable if the ratio is less than , where C and A are the torsion and the bending elastic constants [#!landau!#]. In three dimensions, our variational approach shows that
. This model can be generalized to the case where the bend is induced by a concentration field which follows the variations
of the curvature.
Received: 27 August 1997 / Revised: 23 October 1997 / Accepted: 12 November 1997 相似文献
68.
A multidimensional version of the first Darboux problem is considered for a model second-order degenerating hyperbolic equation. Using the technique of functional spaces with a negative norm, the correct formulation of this problem in the Sobolev weighted space is proved. 相似文献
69.
We provide some inequalities and integral inequalities connected to the Jensen-Hadamard inequalities for convex functions.
In particular, we give some refinements to these inequalities. Some natural applications and further extensions are given.
Sunto Forniamo alcune diseguaglianze e diseguaglianze integrali connesse alle dise-gueglianze di Jensen-Hadamard per funzioni convesse. In particolare, diamo qualche miglioramento di queste diseguaglianze. Alcune applicazioni naturali ed ulteriori estensioni sono date.相似文献
70.
既不离散也不连续的随机变量 总被引:2,自引:1,他引:1
讨论了既不离散也不连续的随机变量 ,并纠正了有关文献中关于连续型随机变量定义中的错误 . 相似文献