全文获取类型
收费全文 | 12766篇 |
免费 | 566篇 |
国内免费 | 883篇 |
专业分类
化学 | 1023篇 |
晶体学 | 9篇 |
力学 | 647篇 |
综合类 | 71篇 |
数学 | 6929篇 |
物理学 | 1549篇 |
综合类 | 3987篇 |
出版年
2024年 | 17篇 |
2023年 | 106篇 |
2022年 | 124篇 |
2021年 | 144篇 |
2020年 | 224篇 |
2019年 | 199篇 |
2018年 | 252篇 |
2017年 | 272篇 |
2016年 | 302篇 |
2015年 | 252篇 |
2014年 | 506篇 |
2013年 | 761篇 |
2012年 | 573篇 |
2011年 | 602篇 |
2010年 | 514篇 |
2009年 | 755篇 |
2008年 | 830篇 |
2007年 | 859篇 |
2006年 | 775篇 |
2005年 | 686篇 |
2004年 | 541篇 |
2003年 | 615篇 |
2002年 | 544篇 |
2001年 | 410篇 |
2000年 | 395篇 |
1999年 | 403篇 |
1998年 | 315篇 |
1997年 | 322篇 |
1996年 | 235篇 |
1995年 | 204篇 |
1994年 | 191篇 |
1993年 | 150篇 |
1992年 | 122篇 |
1991年 | 109篇 |
1990年 | 126篇 |
1989年 | 117篇 |
1988年 | 101篇 |
1987年 | 72篇 |
1986年 | 56篇 |
1985年 | 56篇 |
1984年 | 58篇 |
1983年 | 19篇 |
1982年 | 38篇 |
1981年 | 35篇 |
1980年 | 37篇 |
1979年 | 28篇 |
1978年 | 31篇 |
1977年 | 39篇 |
1976年 | 26篇 |
1974年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 828 毫秒
101.
给出了 n元函数极值的一个充分条件 ,并结合矩阵的初等变换建立了 n元函数极值的一种快速判别法 ,最后给出了一个例子 相似文献
102.
We give combinatorial proofs that certain families of differences of products of Schur functions are monomial-positive. We
show in addition that such monomial-positivity is to be expected of a large class of generating functions with combinatorial
definitions similar to Schur functions. These generating functions are defined on posets with labelled Hasse diagrams and
include for example generating functions of Stanley's (P,ω)-partitions.
T.L. was supported in part by NSF DMS-0600677. 相似文献
103.
For any Sturm-Liouville problem with a separable boundary condition and whose leading coefficient function changes sign (exactly once), we first give a geometric characterization of its eigenvalues λn using the eigenvalues of some corresponding problems with a definite leading coefficient function. Consequences of this characterization include simple proofs of the existence of the λn's, their Prüfer angle characterization, and a way for determining their indices from the zeros of their eigenfunctions. Then, interlacing relations among the λn's and the eigenvalues of the corresponding problems are obtained. Using these relations, a simple proof of asymptotic formulas for the λn's is given. 相似文献
104.
郭秋丽 《浙江万里学院学报》2003,16(2):45-47
设p为正整数,)(pA表示单位圆盘内形如+=+=1)(pkkkpzazzf的解析函数全体,对给定的复 常数p-l及)(zf )(pA, 用 )()()(zfzhzfJ*=ll 定义算子lJ,其中kpkzkpzhlll++==)(,文章得出当)()()(alpnRzfJ(p相似文献
105.
We analyze the critical length for design purposes of six-dimensional spaces invariant under translations and reflections
containing the functions 1, cos t and sin t. These spaces also contain the first degree polynomials as well as trigonometric and/or hyperbolic functions. We identify
the spaces whose critical length for design purposes is greater than 2π and find its maximum 4π. By a change of variables,
two biparametric families of spaces arise. We call shape preservation region to the set of admissible parameters in order
that the space has shape preserving representations for curves. We describe the shape preserving regions for both families.
To our friend Mariano Gasca on occasion of his 60th birthday
Research partially supported by the Spanish Research Grant MTM2006-03388, by Gobierno de Aragón and Fondo Social Europeo. 相似文献
106.
Yan Xu 《Journal of Mathematical Analysis and Applications》2007,329(2):1343-1354
In this paper, we obtain some normality criteria for families of meromorphic functions that concern the exceptional functions of derivatives. 相似文献
107.
The difference between the classical treatment offlexible body impact and the treatment of impact in flexiblemultibody dynamics is due to several fundamental reasons. Inthe classical impact theory, simple structures such as beamsand plates are used. Infinite dimensional models can bedeveloped for these simple structural elements to study theimpact dynamics and the wave propagation problem. Flexiblemultibody impact problems, on the other hand, involve bodieswith complex geometry that cannot be modeled using infinitenumber of degrees of freedom. Furthermore, the classicalimpact theory has been mainly concerned with the impactbetween a rigid mass that moves without constraints beforeit impacts a simple flexible structure. This is not amultibody simulation scenario in which the impact occursbetween kinematically constrained bodies that are subjectedto impulsive constraint forces in addition to the impactforces. These constraint forces can influence the motion ofthe two bodies immediately after impact, and as aconsequence, the simple classical theory scenario of impactdoes not apply. It is the objective of this paper to discussthe use of the restitution condition in flexible multibodyimpact problems and demonstrate that the use of thisapproach does not exclude the classical formulation.Nonetheless, the impulse momentum balance approach can serveas an effective and efficient procedure for solving theimpact problem in finite dimensional models that do not obeythe classical wave theory. Energy results of simplestructural elements are presented in order to demonstratethe consistency of using the impulse momentum balanceapproach in solving impact problems in finite dimensionalflexible body applications. 相似文献
108.
Won-Sang Chung 《International Journal of Theoretical Physics》2003,42(12):2941-2946
In this paper we use the bosonic realization of ospq(1/2) algebra to obtain its metaplectic representation. The group element for this algebra is shown to be described in terms of the basic hypergeometric function. 相似文献
109.
The excess molar enthalpy of ternary mixture for 3-diethylaminopropylamine+heptane+cyclohexane were measured using a Calvet
microcalorimeter at 303.15 K.
Empirical equations, Redlich-Kister, Tsao-Smith, and Kohler and group contribution models, UNIFAC (modified version) and DISQUAC
have been applied. A reasonable representation of ternary data is obtained.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
110.
A uniqueness theorem for two distinct non-constant meromorphic functions that share three values of finite weights is proved, which generalizes two previous results by H.X. Yi, and X.M. Li and H.X. Yi. As applications of it, many known results by H.X. Yi and P. Li, etc. could be improved. Furthermore, with the concept of finite-weight sharing, extensions on Osgood-Yang's conjecture and Mues' conjecture, and a generalization of some prevenient results by M. Ozawa and H. Ueda, ect. could be obtained. 相似文献