全文获取类型
收费全文 | 4517篇 |
免费 | 665篇 |
国内免费 | 382篇 |
专业分类
化学 | 3252篇 |
晶体学 | 51篇 |
力学 | 237篇 |
综合类 | 23篇 |
数学 | 527篇 |
物理学 | 1474篇 |
出版年
2024年 | 7篇 |
2023年 | 110篇 |
2022年 | 171篇 |
2021年 | 180篇 |
2020年 | 165篇 |
2019年 | 146篇 |
2018年 | 140篇 |
2017年 | 108篇 |
2016年 | 201篇 |
2015年 | 204篇 |
2014年 | 248篇 |
2013年 | 279篇 |
2012年 | 346篇 |
2011年 | 386篇 |
2010年 | 239篇 |
2009年 | 234篇 |
2008年 | 281篇 |
2007年 | 258篇 |
2006年 | 234篇 |
2005年 | 198篇 |
2004年 | 168篇 |
2003年 | 152篇 |
2002年 | 127篇 |
2001年 | 103篇 |
2000年 | 90篇 |
1999年 | 114篇 |
1998年 | 100篇 |
1997年 | 90篇 |
1996年 | 90篇 |
1995年 | 78篇 |
1994年 | 54篇 |
1993年 | 33篇 |
1992年 | 37篇 |
1991年 | 32篇 |
1990年 | 23篇 |
1989年 | 17篇 |
1988年 | 20篇 |
1987年 | 19篇 |
1986年 | 13篇 |
1985年 | 9篇 |
1984年 | 15篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 9篇 |
1978年 | 2篇 |
1976年 | 7篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1972年 | 2篇 |
排序方式: 共有5564条查询结果,搜索用时 0 毫秒
21.
THE NECESSARY AND SUFFICIENT CONDITIONS FOR THE SOLVABILITY OF A CLASS OF THE MATRIX INVERSE PROBLEM
Censider the solutions of the matrix inverse problem, which are symmetric positive semide finite on a subspace. Necessary and sufficient conditions for the solvability, as well as the general solution are obtained. The best approximate solution by the above solution set is given. Thus the open problem in [1] is solved. 相似文献
22.
We apply the least‐squares finite element method with adaptive grid to nonlinear time‐dependent PDEs with shocks. The least‐squares finite element method is also used in applying the deformation method to generate the adaptive moving grids. The effectiveness of this method is demonstrated by solving a Burgers' equation with shocks. Computational results on uniform grids and adaptive grids are compared for the purpose of evaluation. The results show that the adaptive grids can capture the shock more sharply with significantly less computational time. For moving shock, the adaptive grid moves correctly with the shock. © 2005 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2006 相似文献
23.
We give a Euclidean wormhole solution in the vacuum Bergmann-Wagoner scalar-tensor gravitational theory. We show that this wormhole, unlike others, has complex charge and is a baby universe (half a wormhole). 相似文献
24.
廖代正 《高等学校化学学报》1988,(7)
本文报道了2个新的Cu(Ⅱ)-Co(Ⅱ)双核配合物的制备。经元素分析和红外、电子光谱以及变温磁化率的测定,研究了配合物的某些性质。 相似文献
25.
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
26.
27.
A rapid method for the derivatization of phenolic antioxidants using microwave irradiation has been developed. Six antioxidatively active phenolic components of wines and fruits, namely gallic acid, gentisic acid, vanillic acid, caffeic acid, ferulic acid and p-coumaric acid were used in the model study. The solution of phenolic acids was evaporated to dryness on a rotary evaporator followed by further drying under microwave irradiation (600 W, 30 s). The resultant residue was dissolved in pyridene and treated with bis(trimethylsilyl)acetamide while irradiated by microwave using high power for 30 s. Controlled reaction was carried out employing bis(trimethylsilyl)trifluoroacetamide under conventional heating for 30 min. The trimethylsilyl derivatives were identified and quantified on a gas chromatography/mass selective detector. The mass spectral fragmentation patterns of the derivatives obtained by microwave irradiation were identical to those prepared by heating. The yields of microwave-assisted silylation were comparable to those from conventional heating. The rsd were less than 8% for six replicates. The linearity in wine matrix was nearly perfect. This method is a useful protocol to examine the phenolic constituents in wines and agricultural products. 相似文献
28.
29.
30.