全文获取类型
收费全文 | 4470篇 |
免费 | 218篇 |
国内免费 | 446篇 |
专业分类
化学 | 1503篇 |
晶体学 | 11篇 |
力学 | 37篇 |
综合类 | 21篇 |
数学 | 3174篇 |
物理学 | 388篇 |
出版年
2024年 | 4篇 |
2023年 | 69篇 |
2022年 | 82篇 |
2021年 | 92篇 |
2020年 | 123篇 |
2019年 | 129篇 |
2018年 | 127篇 |
2017年 | 117篇 |
2016年 | 80篇 |
2015年 | 93篇 |
2014年 | 154篇 |
2013年 | 648篇 |
2012年 | 117篇 |
2011年 | 171篇 |
2010年 | 130篇 |
2009年 | 217篇 |
2008年 | 264篇 |
2007年 | 281篇 |
2006年 | 258篇 |
2005年 | 231篇 |
2004年 | 228篇 |
2003年 | 216篇 |
2002年 | 198篇 |
2001年 | 160篇 |
2000年 | 159篇 |
1999年 | 132篇 |
1998年 | 140篇 |
1997年 | 139篇 |
1996年 | 78篇 |
1995年 | 48篇 |
1994年 | 33篇 |
1993年 | 39篇 |
1992年 | 35篇 |
1991年 | 18篇 |
1990年 | 10篇 |
1989年 | 17篇 |
1988年 | 16篇 |
1987年 | 7篇 |
1986年 | 7篇 |
1985年 | 18篇 |
1984年 | 11篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1974年 | 2篇 |
1973年 | 2篇 |
排序方式: 共有5134条查询结果,搜索用时 31 毫秒
51.
吴炎 《数学物理学报(A辑)》2004,4(6):772-785
设R=Z/2\+kZ(k>1)是\{2\}[TX-]为非单位的有限局部环. 该文首先确定了R上斜对称矩阵标准形. 设G\+m\-p(R,H)={P∈GL\-m(R)|PHP′=H}是由矩阵H确定的伪辛群,其中H=[JB((][HL(2]0[]I\+\{(v)\}\=-I\+\{(v)\}[]0[HL)][JB))]Δ,Δ=[JB((][HL(2]\{2\}[TX-]\+\{k-1\}[]\{1\}[TX-]\=-\{1\}[TX-][]0[HL)][JB))]. 其次,计算了伪辛群G\+m\-P(R,H)的阶|G\+m\-P(R,H)|. 相似文献
52.
Sz.-Nagy's dilation theorem for a contraction on a Hilbert space has been extended by Mlak to the case of a contraction semigroup whose indices are the positive elements of a totally ordered discrete group. We generalize to this case the intertwining lifting theorem of Sz.-Nagy and Foias. Some previous interpolation results on ordered groups are obtained as consequences. 相似文献
53.
在本文中,我们讨论了带作用群的群系的临界结构,给出了处理允许某些作用群的群的问题的一般方法,作为应用,我们特别给出了关于幂零群及p-幂零群的一些结果。 相似文献
54.
55.
Synthesis and characterization of several new anomerically pure galactose derivatives, based on simple and effective protective group manipulations of benzyl β-d-galactopyranoside, are reported. The monosaccharides described contain selectively protected/deprotected hydroxyl functionalities at their 1,2,3,4- and 6-positions rendering them useful as building blocks for construction of branched oligosaccharides. 相似文献
56.
A new hydrophilic copolymer having three kinds of hydroxyl groups, i.e. primary OH on -hydroxy allyl alcohol component, secondary OH on cyclic hemiacetal component and tertiary OH on -hydroxy acrylate component, was prepared by reducing a ‘polylactone’, poly(1-oxa-2-oxobutane-1,4:3,3-tetrayl), with NaBH4 in mixed solvents containing an alcohol. The structural analyses were performed by the solution 1H NMR and the solid state 13C NMR spectroscopies of the reduced samples. The composition of the three components turned out to be variable to the alcohol species used for the mixed solvent. 相似文献
57.
If
is a quasitriangular Lie bialgebra, the formal Poisson group
can be given a braiding structure. This was achieved by Weinstein and Xu using purely geometrical means, and independently by the authors by means of quantum groups. In this paper we compare these two approaches. First, we show that the braidings they produce share several similar properties (in particular, the construction is functorial); secondly, in the simplest case (G=SL2) they do coincide. The question then rises of whether they are always the same this is positively answered in a separate paper. 相似文献
58.
Richard P. Kent IV 《Geometriae Dedicata》2004,106(1):145-159
We answer a question of J. Anderson's by producing infinitely many commensurability classes of fibered hyperbolic 3-manifolds whose fundamental groups contain subgroups that are locally free and not free. These manifolds are obtained by performing 0–surgery on a collection of knots with the same properties. 相似文献
59.
Martin R. Bridson Charles F. Miller III 《Proceedings of the American Mathematical Society》2004,132(1):59-65
We give examples of direct products of three hyperbolic groups in which there cannot exist an algorithm to decide which finitely presented subgroups are isomorphic.
60.
We have prepared glucose and cellobiose conjugates at the phenolic 3- and hydroxylic 17-positions of the pure anti-estrogenic compound fulvestrant (ICI 182,780), which has recently been approved in the USA for the treatment of advanced postmenopausal breast cancer. Glycosylation at the 17-position was achieved most effectively using pivaloyl protection of the sugar imidates employed, which we found suppressed the competing transacylation reaction and led to improved yields of the product glycosides. 相似文献