全文获取类型
收费全文 | 3935篇 |
免费 | 105篇 |
国内免费 | 34篇 |
专业分类
化学 | 2594篇 |
晶体学 | 38篇 |
力学 | 96篇 |
数学 | 742篇 |
物理学 | 604篇 |
出版年
2022年 | 41篇 |
2021年 | 43篇 |
2020年 | 32篇 |
2019年 | 48篇 |
2018年 | 44篇 |
2017年 | 33篇 |
2016年 | 66篇 |
2015年 | 82篇 |
2014年 | 72篇 |
2013年 | 205篇 |
2012年 | 184篇 |
2011年 | 274篇 |
2010年 | 122篇 |
2009年 | 111篇 |
2008年 | 229篇 |
2007年 | 225篇 |
2006年 | 236篇 |
2005年 | 192篇 |
2004年 | 174篇 |
2003年 | 159篇 |
2002年 | 172篇 |
2001年 | 60篇 |
2000年 | 51篇 |
1999年 | 77篇 |
1998年 | 54篇 |
1997年 | 63篇 |
1996年 | 73篇 |
1995年 | 38篇 |
1994年 | 45篇 |
1993年 | 55篇 |
1992年 | 44篇 |
1991年 | 46篇 |
1990年 | 42篇 |
1989年 | 37篇 |
1988年 | 27篇 |
1987年 | 35篇 |
1986年 | 23篇 |
1985年 | 44篇 |
1984年 | 54篇 |
1983年 | 37篇 |
1982年 | 34篇 |
1981年 | 50篇 |
1980年 | 33篇 |
1979年 | 29篇 |
1978年 | 35篇 |
1977年 | 32篇 |
1976年 | 36篇 |
1975年 | 27篇 |
1974年 | 37篇 |
1973年 | 22篇 |
排序方式: 共有4074条查询结果,搜索用时 15 毫秒
11.
12.
Glow Discharge Yuan Mei Douglas C. Duckworth Paula R. Cable R. Kenneth Marcus 《Journal of the American Society for Mass Spectrometry》1994,5(9):845-851
Collision-induced dissociation (CID) of polyatomic ions sampled from an rf-powered glow discharge is examined by using three target gases including atomic (Ar and Xe) and molecular species (N2). Collisions with these targets in the first quadrupole of the double quadrupole system result in the loss of discharge species by dissociation, symmetric and asymmetric charge exchange, and scattering, each to varying degrees. These processes are seen to be a function of the relative mass, size... and ionization potentials of the target species, as well as the collision center-of-mass energies. In light of the comparisons, xenon appears to be the best collision target for both CID and charge exchange because of its relatively low ionization potential and high dissociation efficiency of polyatornic species. Evidence for both symmetric and asymmetric charge exchange is presented for Ar and Xe target gases. 相似文献
13.
Lisa Higham David Kirkpatrick Karl Abrahamson Andrew Adler 《Journal of Algorithms in Cognition, Informatics and Logic》1997,23(2):291-328
Probabilistic algorithms are developed for a basic problem in distributed computation, assuming anonymous, asynchronous, unidirectional rings of processors. The problem, known as Solitude Detection, requires that a nonempty subset of the processors, calledcontenders, determine whether or not there is exactly one contender. Monte Carlo algorithms are developed that err with probability bounded by a specified parameter and exhibit either message or processor termination. The algorithms transmit an optimal expected number of bits, to within a constant factor. Their bit complexities display a surprisingly rich dependence on the kind of termination exhibited and on the processors' knowledge of the size of the ring. Two probabilistic tools are isolated and then combined in various ways to achieve all our algorithms. 相似文献
14.
We consider the minimum number of edges in ak-edge-connected graph of ordern with chromatic number at leastc, obtaining the optimal bounds in most cases. 相似文献
15.
Renewal systems are symbolic dynamical systems originally introduced by Adler. IfW is a finite set of words over a finite alphabetA, then the renewal system generated byW is the subshiftX
W ⊂A
Z formed by bi-infinite concatenations of words fromW. Motivated by Adler’s question of whether every irreducible shift of finite type is conjugate to a renewal system, we prove
that for every shift of finite type there is a renewal system having the same entropy. We also show that every shift of finite
type can be approximated from above by renewal systems, and that by placing finite-type constraints on possible concatenations,
we obtain all sofic systems.
The authors were supported in part by NFS grants DMS-8706284, DMS-8814159 and DMS-8820716. 相似文献
16.
Alick KT Law Deepak Gupta Shawn Levy Douglas C Wallace Robert J McKeon Charles R Buck 《BMC neuroscience》2004,5(1):1
Background
The adenine nucleotide translocator 1 (Ant1) is an inner mitochondrial membrane protein involved with energy mobilization during oxidative phosphorylation. We recently showed that rodent Ant1 is upregulated by transforming growth factor-beta (TGF-β) in reactive astrocytes following CNS injury. In the present study, we describe the molecular mechanisms by which TGF-β1 regulates Ant1 gene expression in cultured primary rodent astrocytes. 相似文献17.
18.
If a and b are trace-class operators, and if u is a partial isometry, then , where ∥⋅∥1 denotes the norm in the trace class. The present paper characterises the cases of equality in this Young inequality, and
the characterisation is examined in the context of both the operator and the Hilbert–Schmidt forms of Young's inequality.
Received: 20 December 2001 / Revised version: 11 July 2002 / Published online: 10 February 2003
Mathematics Subject Classification (2000): 47A63, 15A60 相似文献
19.
20.