全文获取类型
收费全文 | 6735篇 |
免费 | 914篇 |
国内免费 | 627篇 |
专业分类
化学 | 4430篇 |
晶体学 | 47篇 |
力学 | 189篇 |
综合类 | 76篇 |
数学 | 2576篇 |
物理学 | 958篇 |
出版年
2024年 | 10篇 |
2023年 | 32篇 |
2022年 | 115篇 |
2021年 | 171篇 |
2020年 | 207篇 |
2019年 | 225篇 |
2018年 | 156篇 |
2017年 | 259篇 |
2016年 | 322篇 |
2015年 | 278篇 |
2014年 | 417篇 |
2013年 | 666篇 |
2012年 | 458篇 |
2011年 | 456篇 |
2010年 | 413篇 |
2009年 | 445篇 |
2008年 | 488篇 |
2007年 | 513篇 |
2006年 | 388篇 |
2005年 | 329篇 |
2004年 | 268篇 |
2003年 | 239篇 |
2002年 | 179篇 |
2001年 | 193篇 |
2000年 | 147篇 |
1999年 | 137篇 |
1998年 | 95篇 |
1997年 | 93篇 |
1996年 | 85篇 |
1995年 | 80篇 |
1994年 | 65篇 |
1993年 | 72篇 |
1992年 | 64篇 |
1991年 | 46篇 |
1990年 | 15篇 |
1989年 | 24篇 |
1988年 | 22篇 |
1987年 | 13篇 |
1986年 | 15篇 |
1985年 | 17篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 17篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1973年 | 6篇 |
1972年 | 2篇 |
1969年 | 1篇 |
排序方式: 共有8276条查询结果,搜索用时 15 毫秒
991.
Bruce Rothschild 《Journal of Combinatorial Theory, Series A》2006,113(8):1783-1790
Consider the poset, ordered by inclusion, of subspaces of a four-dimensional vector space over a field with 2 elements. We prove that, for this poset, any cutset (i.e., a collection of elements that intersects every maximal chain) contains a maximal anti-chain of the poset. In analogy with the same result by Duffus, Sands, and Winkler [D. Duffus, B. Sands, P. Winkler, Maximal chains and anti-chains in Boolean lattices, SIAM J. Discrete Math. 3 (2) (1990) 197-205] for the subset lattice, we conjecture that the above statement holds in any dimension and for any finite base field, and we prove some special cases to support the conjecture. 相似文献
992.
羊亚平 《数学物理学报(B辑英文版)》1999,19(3)
1991MRSubjectionClassification81R05,20C351IntroductionIiiapreviouspaper['].wit11avediscussedhowtoconstructthewavefllucti()llsofL-S(\011piing,single-lferlllionsystelll.Alldthecoefficientsoffi.actiollalparentage(CFP)withfixs(1seniorityharebeedcalclllatedbyarecurrentformula.Practically,withthe11alpoftileoperatorsofferrxlionpairsthegeneralwavefunctionsofmanyfermionswithsixlgle-lcouldbeobtainedfi.omthewavefullctionswithoutfermionpairs.Asaresult,therecurrentforlllulaofdeterrxliningCFPissimplif… 相似文献
993.
994.
We introduce the potential-decomposition strategy (PDS), which can be used in Markov chain Monte Carlo sampling algorithms. PDS can be designed to make particles move in a modified potential that favors diffusion in phase space, then, by rejecting some trial samples, the target distributions can be sampled in an unbiased manner. Furthermore, if the accepted trial samples are insumcient, they can be recycled as initial states to form more unbiased samples. This strategy can greatly improve efficiency when the original potential has multiple metastable states separated by large barriers. We apply PDS to the 2d Ising model and a double-well potential model with a large barrier, demonstrating in these two representative examples that convergence is accelerated by orders of magnitude. 相似文献
995.
Akira ICHIHARA 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2010,86(7):707-716
This article summarizes my research over 40 years. The main theme of my work is nitrogen metabolism of amino acids, though later I focused on protein turnover in the cell. In the first years of my research work, I was busy dissecting the pathways involved in the metabolism of certain amino acids and their related enzymes. Then I became interested in the physiology and regulation of matabolism of these amino acids. For that, I used primary cultured hepatocytes, which contain many liver-specific enzymes. However, this play field was very rough around 1970 and hence I had to smooth them (differentiated) first. We discovered a specific growth factor (hepatocyte growth factor, HGF) in rat platelets. Exceptionally, I also worked on branched chain amino acids (valine, leucine and isoleucine). These amino acids are not efficiently metabolized in the liver, so I had to consider the physiology of extrahepatic tissues as well. Finally, I came across a huge protease complex, the proteasome. Whether these players, small amino acid metabolizing enzymes and the huge protease complex, danced well in harmony on my playground or not, I still do not know. 相似文献
996.
We have analyzed a linear molecular chain with exciton excitations when the number of excitons is not conserved. The dispersion law depends on two independent variables and it is surfaced in a 3D plot. The same conclusion is valid for the concentrations of excitons and exciton pairs. As it was expected, physical characteristics of the finite chain depend on spatial coordinates. All results are compared to the corresponding results of an infinite chain. 相似文献
997.
Yin-Zhong Wu 《Optics Communications》2010,283(7):1569-1574
With the introduction of Dzyaloshinskii-Moriya (DM) interaction, dynamics of the remote entanglement in one-dimensional Ising chains is investigated. It is found that the DM interaction can excite the remote entanglement from an initial Néel state. For a given strength of DM interaction, the concurrence between the end spins oscillates and decreases simultaneously with the increase of the chain’s length, and drops to zero at a critical length. For the chains with two and three spins, it is very interesting that the dynamics of the staggered magnetization (or the chiral parameter) can be used to qualitatively estimate the evolution of the remote concurrence between the end spins. At last, we discuss the generation of W state from the Ising chain with DM interactions, and it is obtained that W state can only be prepared in the three-qubit and four-qubit chains with a specific strength of DM interaction. 相似文献
998.
Using scanning tunneling microscopy we study the topographic properties of Ag structure on the Au induced, highly ordered Si(5 5 7) surface. Topography measurements show that a small amount of Ag (0.25 ML) deposited on that surface leads to considerable modifications of the one-dimensional structure induced by Au atoms. In particular, we observe two different chains on each terrace, which are identified as Si adatoms and Ag chain structures. The STM topography of those chains strongly depends on the bias voltage, indicating an important role of electronic effects in this system. 相似文献
999.
1000.
We analyze a supply chain with a Resale Price Maintenance (RPM) contract in which the manufacturer sets the retail price with a general multiplicative price–demand function and prove the existence/uniqueness of an equilibrium. We also compare the equilibrium prices and quantities, consumer surplus and total system welfare for the RPM and wholesale price contracts. We conclude that a manufacturer may capture a smaller share of the total supply chain profit despite her ability to set the retail price. 相似文献