全文获取类型
收费全文 | 52700篇 |
免费 | 1398篇 |
国内免费 | 36篇 |
专业分类
化学 | 31560篇 |
晶体学 | 346篇 |
力学 | 893篇 |
综合类 | 1篇 |
数学 | 10077篇 |
物理学 | 11257篇 |
出版年
2023年 | 355篇 |
2022年 | 347篇 |
2021年 | 533篇 |
2020年 | 739篇 |
2019年 | 705篇 |
2018年 | 1064篇 |
2017年 | 967篇 |
2016年 | 1811篇 |
2015年 | 1551篇 |
2014年 | 1536篇 |
2013年 | 3382篇 |
2012年 | 3144篇 |
2011年 | 3043篇 |
2010年 | 2078篇 |
2009年 | 1741篇 |
2008年 | 2653篇 |
2007年 | 2396篇 |
2006年 | 2160篇 |
2005年 | 2137篇 |
2004年 | 1882篇 |
2003年 | 1541篇 |
2002年 | 1361篇 |
2001年 | 1051篇 |
2000年 | 1054篇 |
1999年 | 753篇 |
1998年 | 590篇 |
1997年 | 511篇 |
1996年 | 671篇 |
1995年 | 493篇 |
1994年 | 560篇 |
1993年 | 517篇 |
1992年 | 533篇 |
1991年 | 459篇 |
1990年 | 498篇 |
1989年 | 403篇 |
1988年 | 398篇 |
1987年 | 365篇 |
1986年 | 359篇 |
1985年 | 507篇 |
1984年 | 482篇 |
1983年 | 388篇 |
1982年 | 379篇 |
1981年 | 390篇 |
1980年 | 316篇 |
1979年 | 314篇 |
1978年 | 323篇 |
1977年 | 318篇 |
1976年 | 322篇 |
1974年 | 293篇 |
1973年 | 293篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
141.
J. Adámek 《Algebra Universalis》2004,51(2-3):215-234
A simple, direct proof of the following characterization of varieties of (finitary)
algebras is presented: a cocomplete category is equivalent to a variety iff it has an algebraic
generator, i.e., a regular generator which is exactly projective and finitely generated. This
improves somewhat a recent restatement, due to Pedicchio and Wood, of the classical
characterization theorem of Lawvere. A bijective correspondence between algebraic theories
and algebraic generators is established. 相似文献
142.
We consider a discretized volume V consisting of finite, congruent and attached copies of a tile t. We find a group L
V
the orbit of which, when applied to t, is just V. We show the connection between the structural matrixQ in the formal solution of a boundary value problem formulated for volume V and the so called auxiliary matrix of the graph Γ
v
associated with V. We show boundary value problems to be isomorphic if the graphs associated with the volumes are isomorphic, or, if the covering
groups are Sunada pairs. 相似文献
143.
András Sütő 《Journal of statistical physics》2003,112(1-2):375-396
We study condensation of trapped bosons in the limit when the number of particles tends to infinity. For the noninteracting gas we prove that there is no phase transition in any dimension, but in any dimension, at any temperature the system is 100% condensated into the one-particle ground state. In the case of an interacting gas we show that for a family of suitably scaled pair interactions, the Gross–Pitaevskii scaling included, a less-than-100% condensation into a single-particle eigenstate, which may depend on the interaction strength, persists at all temperatures. 相似文献
144.
Summary The potential of liquid chromatography-mass spectrometry (LC-MS) has been studied for the simultaneous determination of sixteen carbamate and organophosphorus pesticides in honeybees using a traditional sample preparation protocol based on acetone extraction and dichloromethane partitioning. The performances of both atmospheric pressure chemical ionization (APCI) and electrospray (ES) interfaces were compared. APCI offered better sensitivity and specificity for a higher range of pesticides. Limits of quantification were from 0.01 to 0.17 mg kg–1, at which recoveries obtained were between 64 and 93%, except for pirimicarb that was at 13%, with relative standard deviations ranging from 7 to 20%. Fenitrothion, fenoxycarb, methiocarb and phoxim were found in bees from Valencian Community beehives at concentrations between 0.03 and 3.75 mg kg–1. 相似文献
145.
146.
147.
148.
We prove lower bounds of the form exp(nε d), εd > 0, on the length of proofs of an explicit sequence of tautologies, based on the Pigeonhole Principle, in proof systems using formulas of depth d, for any constant d. This is the largest lower bound for the strongest proof system, for which any superpolynomial lower bounds are known. 相似文献
149.
150.