全文获取类型
收费全文 | 19896篇 |
免费 | 3546篇 |
国内免费 | 2857篇 |
专业分类
化学 | 13769篇 |
晶体学 | 257篇 |
力学 | 1437篇 |
综合类 | 195篇 |
数学 | 2444篇 |
物理学 | 8197篇 |
出版年
2024年 | 58篇 |
2023年 | 381篇 |
2022年 | 677篇 |
2021年 | 689篇 |
2020年 | 785篇 |
2019年 | 714篇 |
2018年 | 701篇 |
2017年 | 629篇 |
2016年 | 916篇 |
2015年 | 1032篇 |
2014年 | 1180篇 |
2013年 | 1561篇 |
2012年 | 1713篇 |
2011年 | 1772篇 |
2010年 | 1334篇 |
2009年 | 1233篇 |
2008年 | 1367篇 |
2007年 | 1247篇 |
2006年 | 1193篇 |
2005年 | 1015篇 |
2004年 | 756篇 |
2003年 | 638篇 |
2002年 | 590篇 |
2001年 | 515篇 |
2000年 | 404篇 |
1999年 | 401篇 |
1998年 | 345篇 |
1997年 | 267篇 |
1996年 | 294篇 |
1995年 | 262篇 |
1994年 | 234篇 |
1993年 | 197篇 |
1992年 | 164篇 |
1991年 | 176篇 |
1990年 | 169篇 |
1989年 | 137篇 |
1988年 | 107篇 |
1987年 | 91篇 |
1986年 | 77篇 |
1985年 | 74篇 |
1984年 | 30篇 |
1983年 | 35篇 |
1982年 | 28篇 |
1981年 | 21篇 |
1980年 | 14篇 |
1979年 | 12篇 |
1978年 | 8篇 |
1977年 | 11篇 |
1974年 | 6篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
84.
We construct functions Mα which are piecewise homogeneous polynomials on the (d+1)-dimensional torus Ud+1. These functions possess complete symmetry with respect to the independent variables. The symmetry and homogeneous relations
for these functions are exploited to obtain a recurrence relation and explicit representations. Furthermore, we show that
, where ω=e12x/k, 0≤jt≤k−1, are linearly independent. By restricting Mα to Ud, we obtain the complex analogue of polynomial box splines on a (d+1)-direction mesh on Ud, which is a multivariate analogue of B-splines on the circle studied by I.J. Schoenberg[8]. 相似文献
85.
86.
The principle of structure correlation is applied to 28 crystal structures which contain 44 different five-coordinate molybdenum fragments. The data derived map the reaction pathway for a bimolecular ligand substitution reaction at tetrahedral molybdenum centers. The dihedral-angle method from Muetterties and Guggenberger is employed in order to describe the interconversion between the trigonal bipyramidal (TBP) and the square pyramidal (SQP) conformations via the Berry pseudorotation mechanism in the system of Mo(L)_5 complexes. This structure correlation method provides a convincing mapping of the Berry pathway in this paper. 相似文献
87.
用自由生长系统研究了三硼酸锂LiB_3O_5(LBO)晶体的实际生长形态。实验表明,它的各晶面簇的重要性的顺序为:{110}>{011}>{201}>{111}。讨论了LBO晶体的生长习性与内部结构之间的关系并应用负离子配位多面体理论模型解释了LBO晶体的生长形态。 相似文献
88.
The selectivity of intermolecular force is caused by the special interaction between two adaptable groups on the molecules. π bond and conjugated π bonds such as benzene ring are negative charged groups,which may attract stongly positively charged H groups such as 3H in β-C_6H_6Cl_6, and repulse other ne- gatively charged groups such as-C=O(Q). Our experiments show that the reduced retention time tr of benzene on non- polar β-C_6H_6Cl_6 is much greater than that on polar fixed phases such as CH_3— —NO_2 in gas chromatography and that the het of solvation of β-C_6H_6Cl_6 in benzene is also much greater than that of the polar α-C_6H_6Cl_6 and γ-C_6H_6Cl_6. This can′t be explained by the usual Van de Waals′ force. It results from the selective intermoleccular force.... 相似文献
89.
Weiping Huang Suwen Liu Xianghai Tang Menachem Motiei Yuri Koltypin A. Gedanken 《Research on Chemical Intermediates》2004,30(7-8):793-805
Ag-TiO2, Cu-TiO2 and Ni-TiO2 were prepared by sonication. The interactions of Ti-gel with silver, copper and nickel ions under ultrasound irradiation are very different, although these ions can be dispersed very well in titania. The results of EDXA and XRD analysis indicate that Ti-gel does not react with AgCl and crystallizes unaffectedly to form rutile. M(OH)2 (M = Cu and Ni), on the other hand, favors polycondensation with Ti-gel and affects the crystallization of Ti-gel. CuO favors stabilization of the anatase phase. Ni2+ ions tend to incorporate more easily into titania than Cu2+ ions do when the samples are calcined. TEM, and BET were also used to characterize the samples. 相似文献
90.