全文获取类型
收费全文 | 20079篇 |
免费 | 769篇 |
国内免费 | 158篇 |
专业分类
化学 | 13636篇 |
晶体学 | 143篇 |
力学 | 529篇 |
数学 | 3087篇 |
物理学 | 3611篇 |
出版年
2023年 | 161篇 |
2022年 | 326篇 |
2021年 | 425篇 |
2020年 | 481篇 |
2019年 | 455篇 |
2018年 | 315篇 |
2017年 | 269篇 |
2016年 | 727篇 |
2015年 | 591篇 |
2014年 | 707篇 |
2013年 | 1095篇 |
2012年 | 1439篇 |
2011年 | 1660篇 |
2010年 | 854篇 |
2009年 | 755篇 |
2008年 | 1253篇 |
2007年 | 1185篇 |
2006年 | 1158篇 |
2005年 | 1053篇 |
2004年 | 893篇 |
2003年 | 654篇 |
2002年 | 656篇 |
2001年 | 265篇 |
2000年 | 236篇 |
1999年 | 223篇 |
1998年 | 177篇 |
1997年 | 162篇 |
1996年 | 219篇 |
1995年 | 151篇 |
1994年 | 160篇 |
1993年 | 164篇 |
1992年 | 116篇 |
1991年 | 114篇 |
1990年 | 100篇 |
1989年 | 93篇 |
1988年 | 90篇 |
1987年 | 81篇 |
1986年 | 79篇 |
1985年 | 111篇 |
1984年 | 111篇 |
1982年 | 123篇 |
1981年 | 126篇 |
1980年 | 104篇 |
1979年 | 89篇 |
1978年 | 116篇 |
1977年 | 96篇 |
1976年 | 78篇 |
1975年 | 75篇 |
1974年 | 71篇 |
1973年 | 72篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
21.
Sang Kyu Lee Min Ju Cho Jung‐Il Jin Dong Hoon Choi 《Journal of polymer science. Part A, Polymer chemistry》2007,45(3):531-542
New photocrosslinkable maleimide copolymers have been synthesized by the attachment of a tricyanopyrrolidene‐based chromophore. The 2‐(3‐cyano‐4‐(2‐{4‐[hexyl‐(6‐hydroxy‐hexyl)‐amino]‐phenyl}‐vinyl)‐5‐oxo‐1‐{4‐[4‐(3‐oxo‐3‐phenyl‐propenyl)‐ phenoxy]‐butyl}‐1,5‐dihydro‐pyrrol‐2‐ylidene)‐malononitrile chromophore exhibits nonlinear optical activity and contains a chalcone moiety that is sensitive to UV light (λ = 330–360 nm) for crosslink formation. The maleimide monomers have also been functionalized with chalcone moieties. The resultant copolymers exhibit great processability, and one of them shows a maximum electrooptic coefficient of 90 pm/V at 1300 nm. We could control the thermal stability of the electrooptic coefficient with the newly synthesized photoreactive copolymers successfully. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 531–542, 2007 相似文献
22.
Daniel Pa?ca 《Journal of Mathematical Analysis and Applications》2007,325(1):90-100
Some existence results are obtained for periodic solutions of nonautonomous second-order differential inclusions systems with p-Laplacian. 相似文献
23.
Daniel Maerten 《Annals of Global Analysis and Geometry》2007,32(4):391-414
We prove a Penrose-like inequality for the mass of a large class of constant mean curvature (CMC) asymptotically flat n-dimensional spin manifolds which satisfy the dominant energy condition and have a future converging, or past converging compact
and connected boundary of non-positive mean curvature and of positive Yamabe invariant. We prove that for every n ≥ 3 the mass is bounded from below by an expression involving the norm of the linear momentum, the volume of the boundary,
dimensionless geometric constants and some normalized Sobolev ratio. 相似文献
24.
This note discusses the need to use various data-compaction schemes in the implementation of sophisticated large-scale linear programming codes on modest personal computers. It demonstrates a method whereby the overhead of using these schemes is significantly reduced on Intel 80 x 86 processors. 相似文献
25.
Expert Rule Versus Majority Rule Under Partial Information, II 总被引:1,自引:0,他引:1
The main purpose of this paper is clarifying the connection between some characteristics of a deciding body and the probability of its making correct decisions. In our model a group of decision makers is required to select one of two alternatives. We assume the probabilities of the decision makers being correct are independent random variables distributed according to the same given distribution rule. This distribution belongs to a general family, containing the uniform distribution as a particular case. We investigate the behavior of the probability of the expert rule being optimal, as well as that of the majority rule, both as functions of the distribution parameter and the group size. The main result is that for any value of the distribution parameter the expert rule is far more likely to be optimal than the majority rule, especially as the deciding body becomes larger. 相似文献
26.
Daniel W. Stroock 《Journal of Functional Analysis》2007,242(1):295-303
The purpose of this note is to describe a procedure for transferring familiar estimates for transition probabilities on RN to transition probabilities on compact manifolds. 相似文献
27.
We show that the tenure lengths for managers of sport teams follow a power law distribution with an exponent between 2 and 3. We develop a simple theoretical model which replicates this result. The model demonstrates that the empirical phenomenon can be understood as the macroscopic outcome of pairwise interactions among managers in a league, threshold effects in managerial performance evaluation, competitive market forces, and luck at the microscopic level. 相似文献
28.
D. Fong J. H. Hamilton A. V. Ramayya J. K. Hwang C. Goodin K. Li J. Kormicki J. O. Rasmussen Y. X. Luo S. C. Wu I. Y. Lee A. V. Daniel G. M. Ter-Akopian G. S. Popeko A. S. Fomichev A. M. Rodin Yu. Ts. Oganessian M. Jandel J. Kliman L. Krupa J. D. Cole M. A. Stoyer R. Donangelo W. C. Ma 《Physics of Atomic Nuclei》2006,69(7):1161-1167
The hot bimodal fission of 252Cf is reexamined with new high-statistics data. We constructed a γ-γ-γ coincidence cube for binary fission and LCP-gated γ-γ matrix for ternary fission. By identifying the secondary fission fragments from their γ-ray transitions, we measured the yields for various fission splits. The normal neutron yield distribution is found to be
Gaussian for Xe-Ru. However, the binary fission split of Ba-Mo is found to exhibit a bimodal neutron distribution with the
“hot mode” corresponding to ≈3.1% of the total yield. In α ternary fission, the first measurements of yields for specific fission splits are presented. The Te-α-Ru and Xe-α-Mo neutron yields fit well with a single mode, but the Ba-α-Zr split shows evidence for an enhanced hot mode with an intensity of ≈13.8% of the normal mode.
The text was submitted by the authors in English. 相似文献
29.
The European Physical Journal C - The CMS experiment&;nbsp;[1] uses a general purpose detector designed for detecting the diverse signatures associated with Higgs production and new physics... 相似文献
30.
Monodisperse polyaniline nanoparticles (PAPSSA) were synthesized from an oxidative dispersion polymerization using poly(sodium 4-styrenesulfonate) (PSSA) as both a polymeric stabilizer and a dopant agent due to its acidity. The nanoparticles were being stabilized with two different molecular weight of PSSA. Size effect of PAPSSA particles were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and dynamic light scattering (DLS). The d.c. electrical conductivity of composite films on the glass substrate was measured by a four-probe method. It was found that the electrical properties of the composite films are affected by the content of nano-sized polyaniline and different molecular weights of stabilizer in the poly(vinyl alcohol) (PVA) matrix. 相似文献