全文获取类型
收费全文 | 43690篇 |
免费 | 873篇 |
国内免费 | 329篇 |
专业分类
化学 | 21223篇 |
晶体学 | 303篇 |
力学 | 1729篇 |
综合类 | 12篇 |
数学 | 11234篇 |
物理学 | 10391篇 |
出版年
2023年 | 121篇 |
2022年 | 142篇 |
2021年 | 248篇 |
2020年 | 352篇 |
2019年 | 347篇 |
2018年 | 1387篇 |
2017年 | 1630篇 |
2016年 | 1210篇 |
2015年 | 1097篇 |
2014年 | 1040篇 |
2013年 | 1454篇 |
2012年 | 4209篇 |
2011年 | 3444篇 |
2010年 | 2458篇 |
2009年 | 2102篇 |
2008年 | 1438篇 |
2007年 | 1481篇 |
2006年 | 1391篇 |
2005年 | 5163篇 |
2004年 | 4477篇 |
2003年 | 2779篇 |
2002年 | 967篇 |
2001年 | 518篇 |
2000年 | 263篇 |
1999年 | 332篇 |
1998年 | 277篇 |
1997年 | 233篇 |
1996年 | 182篇 |
1995年 | 151篇 |
1994年 | 148篇 |
1993年 | 137篇 |
1992年 | 252篇 |
1991年 | 234篇 |
1990年 | 206篇 |
1989年 | 190篇 |
1988年 | 168篇 |
1987年 | 104篇 |
1986年 | 96篇 |
1985年 | 113篇 |
1984年 | 91篇 |
1983年 | 94篇 |
1982年 | 85篇 |
1981年 | 97篇 |
1979年 | 88篇 |
1978年 | 77篇 |
1977年 | 78篇 |
1976年 | 142篇 |
1975年 | 90篇 |
1974年 | 75篇 |
1973年 | 96篇 |
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
51.
52.
53.
L. Bugliaro J. Fröhlich G.M. Graf J. Stubbe C. Fefferman 《Communications in Mathematical Physics》1997,187(3):567-582
A Lieb-Thirring-Sobolev type inequality for Pauli Hamiltonians with magnetic fields is derived. The bound is in terms of an
effective field, whose energy is comparable to that of the magnetic field itself. An application to the stability of matter
in magnetic fields is given.
Received: 19 September 1996 / Accepted: 3 January 1997 相似文献
54.
Christian Prins 《The Journal of the Operational Research Society》1994,45(6):611-623
Satellite communications, like batches of work in a job shop, need to be scheduled in order to use their resources as efficiently as possible. The most common satellite communications system in use today is known as Time Division Multiple Access (TDMA), in which data from earth stations is buffered before being transmitted to the appropriate receiver on a satellite. Cycles of transmission are fixed for all stations. Since the same satellite will be used for routeing data in several different ways, a schedule must be devised to use the receivers, repeaters and transmitters on board to minimize the time needed for completion of a batch of work. This paper is a survey of current scheduling algorithms used for optimizing satellite communications resources. Apart from telecommunications, the methods presented here could be applied to more general scheduling problems with renewable resources but without precedence constraints. 相似文献
55.
Ingrid Lukkari Jaromir Ruzicka Gary D. Christian 《Fresenius' Journal of Analytical Chemistry》1993,346(6-9):813-818
Summary Automated methods for the determination of ammonium and ammonia are reviewed, and techniques based on gas diffusion using a semi-permeable membrane were selected for the determination of both total ammonium-nitrogen and free ammonia in fermentation samples. A simple and robust instrument based on sequential injection analysis (SIA) consisting of a piston pump and two selector valves was used. Two different methods of ammonia detection, the Berthelot method and detection using pH-indicators, have been evaluated and compared. The indicator method showed higher reproducibility and the range of determination could easily be adjusted to match the concentrations of the samples. The range of determination could be adjusted from 0.05 mmol/l to 350 mmol/l, depending on choice of acceptor solution. This method has been evaluated with fermentation medium samples and tested on-line in a yeast fermentation process.Dedicated to Professor Dr. Wilhelm Fresenius on the occasion of his 80th birthday 相似文献
56.
This Note deals with optimal control problems with only one control variable and one state constraint, of arbitrary order. We consider the case of finitely many boundary arcs and touch times. We obtain a no-gap theory of second-order conditions, allowing us to characterize second-order quadratic growth. To cite this article: J.F. Bonnans, A. Hermant, C. R. Acad. Sci. Paris, Ser. I 343 (2006). 相似文献
57.
We prove that RANDOM EDGE, the simplex algorithm that always chooses a random improving edge to proceed on, can take a mildly exponential number of steps in the model of abstract objective functions (introduced by Williamson Hoke [Completely unimodal numberings of a simple polytope, Discrete Appl. Math. 20 (1988) 69-81.] and by Kalai [A simple way to tell a simple polytope from its graph, J. Combin. Theory Ser. A 49(2) (1988) 381-383.] under different names). We define an abstract objective function on the n-dimensional cube for which the algorithm, started at a random vertex, needs at least exp(const·n1/3) steps with high probability. The best previous lower bound was quadratic. So in order for RANDOM EDGE to succeed in polynomial time, geometry must help. 相似文献
58.
Sudoku’s french ancestors 总被引:1,自引:0,他引:1
Christian Boyer 《Mathematical Intelligencer》2007,29(1):37-44
This column is a place for those bits of contagious mathematics that travel from person to person in the community, because
they are so elegant, suprising, or appealing that one has an urge to pass them on.
Contributions are most welcome. 相似文献
59.
Christian Remling 《Communications in Mathematical Physics》2007,271(1):275-287
I present an example of a discrete Schrödinger operator that shows that it is possible to have embedded singular spectrum and, at the same time, discrete eigenvalues that approach the edges of the essential spectrum (much) faster than exponentially. This settles a conjecture of Simon (in the negative). The potential is of von Neumann-Wigner type, with careful navigation around a previously identified borderline situation. 相似文献
60.
This paper establishes a link between a generalized matrix Matsumoto-Yor (MY) property and the Wishart distribution. This link highlights certain conditional independence properties within blocks of the Wishart and leads to a new characterization of the Wishart distribution similar to the one recently obtained by Geiger and Heckerman but involving independences for only three pairs of block partitionings of the random matrix.In the process, we obtain two other main results. The first one is an extension of the MY independence property to random matrices of different dimensions. The second result is its converse. It extends previous characterizations of the matrix generalized inverse Gaussian and Wishart seen as a couple of distributions.We present two proofs for the generalized MY property. The first proof relies on a new version of Herz's identity for Bessel functions of matrix arguments. The second proof uses a representation of the MY property through the structure of the Wishart. 相似文献