全文获取类型
收费全文 | 20010篇 |
免费 | 1688篇 |
国内免费 | 1301篇 |
专业分类
化学 | 5462篇 |
晶体学 | 137篇 |
力学 | 1462篇 |
综合类 | 246篇 |
数学 | 11304篇 |
物理学 | 4388篇 |
出版年
2024年 | 36篇 |
2023年 | 278篇 |
2022年 | 458篇 |
2021年 | 523篇 |
2020年 | 692篇 |
2019年 | 676篇 |
2018年 | 639篇 |
2017年 | 719篇 |
2016年 | 704篇 |
2015年 | 599篇 |
2014年 | 1037篇 |
2013年 | 2120篇 |
2012年 | 1078篇 |
2011年 | 1124篇 |
2010年 | 911篇 |
2009年 | 1239篇 |
2008年 | 1302篇 |
2007年 | 1138篇 |
2006年 | 948篇 |
2005年 | 887篇 |
2004年 | 706篇 |
2003年 | 599篇 |
2002年 | 611篇 |
2001年 | 464篇 |
2000年 | 487篇 |
1999年 | 476篇 |
1998年 | 391篇 |
1997年 | 384篇 |
1996年 | 281篇 |
1995年 | 191篇 |
1994年 | 155篇 |
1993年 | 137篇 |
1992年 | 101篇 |
1991年 | 89篇 |
1990年 | 62篇 |
1989年 | 64篇 |
1988年 | 60篇 |
1987年 | 59篇 |
1986年 | 42篇 |
1985年 | 91篇 |
1984年 | 93篇 |
1983年 | 43篇 |
1982年 | 53篇 |
1981年 | 51篇 |
1980年 | 40篇 |
1979年 | 43篇 |
1978年 | 31篇 |
1977年 | 21篇 |
1976年 | 21篇 |
1974年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
A finite support product of clones of Jensen's minimal singleton forcing is used to define a model in which any non-empty analytically definable set of reals contains an analytically definable real (the full basis theorem), but there is no analytically definable wellordering of the reals. 相似文献
2.
3.
Synthesis of diisocyanides with phenolic groups and their polymerization to helically chiral poly(quinoxaline‐2,3‐diyl)s 下载免费PDF全文
Johannes Scholz Michael Reggelin 《Journal of polymer science. Part A, Polymer chemistry》2015,53(11):1320-1329
The development of synthetic routes which lead to five new diisocyanide monomers with one or two phenolic groups is described. Their polymerization behavior is studied with Pd‐ and Ni‐based initiators, as well as under microwave irradiation. The polymerizability is mainly dominated by steric effects as is concluded from experiments using different protecting groups. Chiroptical properties of these new polymers are studied by CD‐spectroscopy. After deprotection, helically chiral poly(quinoxalin‐2,3‐diyl)s are obtained which display a Brønsted function attached to a stereolabile biaryl axis whose configuration should be influenced by the chiral polymer backbone. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1320–1329 相似文献
4.
5.
In this paper, the deformation of the Heisenberg algebra, consistent with both the generalized uncertainty principle and doubly special relativity, has been analyzed. It has been observed that, though this algebra can give rise to fractional derivative terms in the corresponding quantum mechanical Hamiltonian, a formal meaning can be given to them by using the theory of harmonic extensions of function. Depending on this argument, the expression of the propagator of the path integral corresponding to the deformed Heisenberg algebra, has been obtained. In particular, the consistent expression of the one dimensional free particle propagator has been evaluated explicitly. With this propagator in hand, it has been shown that, even in free particle case, normal generalized uncertainty principle and doubly special relativity show very much different result. 相似文献
6.
7.
A method using third order moments for estimating the regression coefficients as well as the latent state scores of the reduced-rank regression model when the latent variable(s) are non-normally distributed is presented in this paper. It is shown that the factor analysis type indeterminacy of the regression coefficient matrices is eliminated. A real life example of the proposed method is presented. Differences of this solution with the reduced-rank regression eigen solution are discussed. 相似文献
8.
Debendra K. Mohapatra Dhananjoy Mondal Mukund S. Chorghade Mukund K. Gurjar 《Tetrahedron letters》2006,47(52):9215-9219
The non-proteinogenic amino acid 3-hydroxy-4-methylproline (HMP) is an active constituent of some potent antimicrobials including echinocandins, nostopeptins, pneumocandins, sporiofungin and mulundocandins. A synthesis has been achieved in 10 steps with 29% overall yield; the Evans’ aldol reaction using Crimmins’ modified method was pivotal to the success of the strategy. 相似文献
9.
We consider immersions: and construct a subspace of which corresponds to a set of embedded manifolds which are either parallel to f, tubes around f or, in general, partial tubes around f. This space is invariant under the action of the normal holonomy group, We investigate the case where is non-trivial and obtain some results on the number of connected components of .
Received 24 March 2000. 相似文献
10.
Taekyun Kim 《Journal of Mathematical Analysis and Applications》2002,273(1):236-242
The purpose of this paper is to give a proof of Kummer type congruence for the q-Bernoulli numbers of higher order, which is an answer to a part of the problem in a previous publication (see Indian J. Pure Appl. Math. 32 (2001) 1565-1570). 相似文献