全文获取类型
收费全文 | 5355篇 |
免费 | 232篇 |
国内免费 | 44篇 |
专业分类
化学 | 3739篇 |
晶体学 | 77篇 |
力学 | 206篇 |
数学 | 889篇 |
物理学 | 720篇 |
出版年
2023年 | 49篇 |
2022年 | 44篇 |
2021年 | 100篇 |
2020年 | 122篇 |
2019年 | 121篇 |
2018年 | 74篇 |
2017年 | 50篇 |
2016年 | 143篇 |
2015年 | 156篇 |
2014年 | 179篇 |
2013年 | 285篇 |
2012年 | 410篇 |
2011年 | 429篇 |
2010年 | 252篇 |
2009年 | 202篇 |
2008年 | 346篇 |
2007年 | 312篇 |
2006年 | 306篇 |
2005年 | 292篇 |
2004年 | 250篇 |
2003年 | 222篇 |
2002年 | 239篇 |
2001年 | 74篇 |
2000年 | 58篇 |
1999年 | 63篇 |
1998年 | 42篇 |
1997年 | 62篇 |
1996年 | 70篇 |
1995年 | 44篇 |
1994年 | 42篇 |
1993年 | 36篇 |
1992年 | 39篇 |
1991年 | 20篇 |
1990年 | 26篇 |
1989年 | 29篇 |
1988年 | 18篇 |
1987年 | 20篇 |
1986年 | 20篇 |
1985年 | 29篇 |
1984年 | 33篇 |
1983年 | 23篇 |
1982年 | 30篇 |
1981年 | 18篇 |
1980年 | 27篇 |
1979年 | 25篇 |
1978年 | 23篇 |
1977年 | 25篇 |
1976年 | 21篇 |
1975年 | 18篇 |
1974年 | 20篇 |
排序方式: 共有5631条查询结果,搜索用时 31 毫秒
31.
A rooted graph is a pair (G,x), where G is a simple undirected graph and x ∈ V(G). If G is rooted at x, its kth rotation number hk (G,x) is the minimum number of edges in a graph F of order |G| + k such that for every v ∈ V(F) we can find a copy of G in F with the root vertex x at v. When k = 0, this definition reduces to that of the rotation number h(G,x), which was introduced in [“On Rotation Numbers for Complete Bipartite Graphs,” University of Victoria, Department of Mathematics Report No. DM-186-IR (1979)] by E.J. Cockayne and P.J. Lorimer and subsequently calculated for complete multipartite graphs. In this paper, we estimate the kth rotation number for complete bipartite graphs G with root x in the larger vertex class, thereby generalizing results of B. Bollobás and E.J. Cockayne [“More Rotation Numbers for Complete Bipartite Graphs,” Journal of Graph Theory, Vol. 6 (1982), pp. 403–411], J. Haviland [“Cliques and Independent Sets,” Ph. D. thesis, University of Cambridge (1989)], and J. Haviland and A. Thomason [“Rotation Numbers for Complete Bipartite Graphs,” Journal of Graph Theory, Vol. 16 (1992), pp. 61–71]. © 1993 John Wiley & Sons, Inc. 相似文献
32.
Lionel Joucla Florence Popowycz Olivier Lozach Laurent Meijer Benoît Joseph 《Helvetica chimica acta》2007,90(4):753-763
The syntheses of paullone ( 1a ) and three paullone derivatives, including a sulfur analogue ( 2a ), a tricyclic derivative ( 2b ), and a ring‐enlarged variant ( 2c ), are described, Pd‐catalyzed intramolecular Heck reaction being the key step. The kinase‐inhibitory properties of the novel paullone analogues were investigated. 相似文献
33.
Tevian Dray Corinne A. Manogue Robin W. Tucker 《General Relativity and Gravitation》1991,23(8):967-971
We consider the (massless) scalar field on 2-dimensional manifolds whose metric changes signature and which admit a spacelike isometry. Choosing the wave equation so that there will be a conserved Klein-Gordon product implicitly determines the junction conditions one needs to impose in order to obtain global solutions. The resulting mix of positive and negative frequencies produced by the presence of Euclidean regions depends only on the total width of the regions, and not on the detailed form of the metric.This essay received honorable mention in the 1991 competition of the Gravity Research Foundation. 相似文献
34.
Paolo Battocchio Francesco Menoncin Olivier Scaillet 《Annals of Operations Research》2007,152(1):141-165
In a financial market with one riskless asset and n risky assets whose prices are lognormal, we solve in a closed form the problem of a pension fund maximizing the expected
CRRA utility of its surplus till the (stochastic) death time of a representative agent. We consider a unique asset allocation
problem for both accumulation and decumulation phases. The optimal investment in the risky assets must decrease during the
first phase and increase during the second one. We accordingly suggest it is not optimal to manage the two phases separately,
and outsourcing of allocation decisions should be avoided in both phases.
JEL: G23, G11
MSC 2000: 62P05, 91B28, 91B30, 91B70, 93E20 相似文献
35.
S. Franchoo F. Ibrahim F. Le Blanc M. Lebois A. Olivier C. Phan Viet B. Roussière R. Sifi D. Verney 《Hyperfine Interactions》2006,171(1-3):117-119
The availability of both a tandem deuteron beam and a linac electron beam, the latter converted into Bremsstrahlung, at the
new ALTO facility at IPN-Orsay offers a unique opportunity to compare the performance of a laser ion guide under different
regimes. The ALTO accelerator has delivered its first electron beam at the end of 2005 and a design for a gas-cell prototype
is being studied. 相似文献
36.
37.
38.
Robin M. Hogarth 《Annals of Operations Research》1989,19(1):29-50
39.
John R. Peterson Tamara J. Winter Hoang D. Do Robin D. Rogers 《Journal of chemical crystallography》1989,19(1):135-145
Structural and conformational information obtained from the crystal structure and solution1H nmr investigations of the title compound are compared. The 4-aryltetralone, C24H24O10, crystallizes as a chloroform solvate in the monoclinic space group, P21/n, witha=12.519(4),b=17.938(6),c=12.534(9)Å,=111.90(5)°, and Dcalc=1.51 g cm–3 forZ=4. The data for this compound were collected at –150°C. Least-squares refinement of 2796 observed [F
o5(F
o)] reflections led to the final agreement index ofR=0.062. A threefold static disorder was observed for one of the carboxyl groups. The second carboxyl group participates in an intramolecular hydrogen bond and is thus ordered. The1H nmr spectrum revealed the title compound to exist as a keto-enol tautomeric mixture in solution. Vicinal hydrogen coupling constant analysis proved reliable in ascertaining B-ring stereochemistry of 2,3-disubstituted-4-aryltetralones. 相似文献
40.