全文获取类型
收费全文 | 18833篇 |
免费 | 616篇 |
国内免费 | 342篇 |
专业分类
化学 | 11677篇 |
晶体学 | 108篇 |
力学 | 630篇 |
综合类 | 30篇 |
数学 | 2801篇 |
物理学 | 4545篇 |
出版年
2023年 | 119篇 |
2022年 | 282篇 |
2021年 | 349篇 |
2020年 | 273篇 |
2019年 | 291篇 |
2018年 | 263篇 |
2017年 | 214篇 |
2016年 | 497篇 |
2015年 | 454篇 |
2014年 | 520篇 |
2013年 | 1033篇 |
2012年 | 906篇 |
2011年 | 1061篇 |
2010年 | 704篇 |
2009年 | 652篇 |
2008年 | 940篇 |
2007年 | 931篇 |
2006年 | 794篇 |
2005年 | 786篇 |
2004年 | 735篇 |
2003年 | 721篇 |
2002年 | 764篇 |
2001年 | 488篇 |
2000年 | 440篇 |
1999年 | 352篇 |
1998年 | 250篇 |
1997年 | 249篇 |
1996年 | 271篇 |
1995年 | 269篇 |
1994年 | 252篇 |
1993年 | 207篇 |
1992年 | 179篇 |
1991年 | 183篇 |
1990年 | 210篇 |
1989年 | 173篇 |
1988年 | 147篇 |
1987年 | 150篇 |
1986年 | 134篇 |
1985年 | 230篇 |
1984年 | 246篇 |
1983年 | 172篇 |
1982年 | 188篇 |
1981年 | 155篇 |
1980年 | 162篇 |
1979年 | 151篇 |
1978年 | 131篇 |
1977年 | 175篇 |
1976年 | 153篇 |
1975年 | 124篇 |
1973年 | 118篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
101.
A path-integral molecular dynamics technique for strongly interacting atoms using ab initio potentials derived from density functional theory is implemented. This allows the efficient inclusion of nuclear quantum dispersion in ab initio simulations at finite temperatures. We present an application to the quantum cluster H
5
+
. 相似文献
102.
Given an integer n ≥ 2, let λ(n) := (log n)/(log γ(n)), where γ(n) = Π
p|n p, stand for the index of composition of n, with λ(1) = 1. We study the distribution function of (λ(n) – 1) log n as n runs through particular sets of integers, such as the shifted primes, the values of a given irreducible cubic polynomial
and the shifted powerful numbers.
Research supported in part by a grant from NSERC.
Research supported by the Applied Number Theory Research Group of the Hungarian Academy of Science and by a grant from OTKA.
Professor M.V. Subbarao passed away on February 15, 2006.
Received: 3 March 2006 Revised: 28 October 2006 相似文献
103.
Yan Shun MA Qing Hua MENG Hong Yu SHI Yuan De LONG Tian Bao HUANG 《中国化学快报》2006,17(6):807-808
Dencichine (β-N-oxalyl-L-α, β-diaminopropionic acid, L-ODAP), a nonprotein amino acid, is a haemostatic agent present in important Chinese medicinal herbs such as Panax notoginseng, as well as other Panax species1. It was first isolated from the seeds … 相似文献
104.
Carolina Pereira De Souza Margareth Spangler Andrade Bernardo Ruegger Almeida Neves 《Microscopy and microanalysis》2002,8(6):509-517
In this work, effective, yet simple, recycling mechanisms for used scanning probe microscopy (SPM) tips were implemented. Comprising a tip profile characterization methodology and specific cleaning procedures, which decontaminate SPM tips whether the contamination nature is known or not, such routes were optimized during numerous tests with brand new, previously used, and already discarded categories of SPM tips. The results show that if the used tip suffered contamination only, but no physical damages, during its scanning lifetime, it becomes readily available for reutilization after the cleansing process, characterizing a recycling route. On the other hand, if the tip went through wear and breakages during its utilization, it still can be decontaminated, but may not be directly reutilized due to its inadequate physical profile. Nevertheless, the methodology developed in this work may yet be applied as part of a more complex recycling route. 相似文献
105.
106.
Guido Momerency Karel Van Cauwenberghe Ernst A. De Bruijn Allan T. Van Oosterom Martin S. Highley Peter G. Harper 《Journal of separation science》1994,17(9):655-661
A method is described for the determination of the antitumor agent iphosphamide and seven of its metabolites in the plasma of cancer patients by multiple ion monitoring (MIM) GC-MS, mainly using the electron capture chemical ionization mode, of stable methyl and/or trifluoroacetyl derivatives. The metabolites determined were 2- and 3-dechloroethyliphosphamide, 4-ketoiphosphamide, carboxyiphosphamide, iphosphamide mustard, and two previously undetected metabolites, chloroethylamine and 1,3-oxazolidine-2-one. The isolation of the acidic and neutral metabolites was performed by solid phase extraction on to C18 adsorbent at pH 4. The weakly acidic iphosphamide mustard, isolated under these conditions with a yield of ca 50%, was measured as a stable methyltrifluoroacetyl derivative, in contrast to the corresponding phosphoramide mustard of the isomer cyclophosphamide which decomposes during derivatization. Chloroethylamine and 1,3-oxazolidine-2-one were isolated with high yield by liquid extraction with ethyl acetate at pH 10. Selective measurement of several metabolite derivatives with similar retention times was performed by multiple ion monitoring MS of specific ion masses, using a methyl phenyl siloxane capillary column previously employed in the study of cyclophosphamide metabolites. Quantitation of metabolites in patient plasma samples could be performed in the concentration range 3 ng to 20 μg per ml of original plasma. 相似文献
107.
108.
关于RNP和SCS的若干等价条件 总被引:1,自引:0,他引:1
使用切片方法,讨论了Banach空间中有界闭凸子集的RNP和SCS的若干等价条件. 相似文献
109.
Michele Ciarletta 《Journal of Elasticity》1995,39(3):229-246
This paper is concerned with the dynamic theory of a binary mixture consisting of a gas and an elastic solid. First, we derive general theorems (reciprocal theorem, uniqueness theorem, minimum principle). The, we establish a Galerkin representation and the fundamental solutions in the case of steady vibrations.Work performed under the auspices of G.N.F.M. of the Italian Research Council (C.N.R.), with the grant 60% M.U.R.S.T. (ITALY). 相似文献
110.
Anne Boutet De Monvel-Berthier Louis Boutet De Monvel Gilles Lebeau 《Journal d'Analyse Mathématique》1992,58(1):39-60
Sans résumé
Dedicated to Professor Shmuel Agmon 相似文献