全文获取类型
收费全文 | 6929篇 |
免费 | 1167篇 |
国内免费 | 741篇 |
专业分类
化学 | 4653篇 |
晶体学 | 72篇 |
力学 | 407篇 |
综合类 | 41篇 |
数学 | 646篇 |
物理学 | 3018篇 |
出版年
2024年 | 16篇 |
2023年 | 149篇 |
2022年 | 168篇 |
2021年 | 173篇 |
2020年 | 262篇 |
2019年 | 217篇 |
2018年 | 205篇 |
2017年 | 185篇 |
2016年 | 292篇 |
2015年 | 288篇 |
2014年 | 356篇 |
2013年 | 502篇 |
2012年 | 540篇 |
2011年 | 609篇 |
2010年 | 408篇 |
2009年 | 411篇 |
2008年 | 434篇 |
2007年 | 370篇 |
2006年 | 363篇 |
2005年 | 335篇 |
2004年 | 276篇 |
2003年 | 204篇 |
2002年 | 222篇 |
2001年 | 173篇 |
2000年 | 168篇 |
1999年 | 176篇 |
1998年 | 130篇 |
1997年 | 128篇 |
1996年 | 151篇 |
1995年 | 107篇 |
1994年 | 113篇 |
1993年 | 108篇 |
1992年 | 100篇 |
1991年 | 83篇 |
1990年 | 63篇 |
1989年 | 74篇 |
1988年 | 52篇 |
1987年 | 46篇 |
1986年 | 38篇 |
1985年 | 34篇 |
1984年 | 19篇 |
1983年 | 18篇 |
1982年 | 14篇 |
1981年 | 13篇 |
1980年 | 9篇 |
1979年 | 6篇 |
1976年 | 4篇 |
1973年 | 3篇 |
1970年 | 3篇 |
1957年 | 3篇 |
排序方式: 共有8837条查询结果,搜索用时 234 毫秒
991.
Li W Zhang M Zheng YN Li J Wang YP Wang YJ Gu J Jin Y Wang H Chen L 《Molecules (Basel, Switzerland)》2011,16(12):10093-10103
To investigate the protective effects of protopanaxadiol-type ginsenoside (PDG) and its metabolite ginsenoside M1 (G-M1) on carbon tetrachloride (CCl(4))-induced chronic liver injury in ICR mice, we carried out conversion of protopanaxadiol-type ginsenosides to ginsenoside M1 using snailase. The optimum time for the conversion was 24 h at a constant pH of 4.5 and an optimum temperature of 50 °C. The transformation products were identified by high-performance liquid chromatography and electrospray ion-mass spectrometry. Subsequently, most of PDG was decomposed and converted into G-M1 by 24 h post-reaction. During the study on hepatoprotective in a mice model of chronic liver injury, PDG or G-M1 supplement significantly ameliorated the CCl(4)-induced liver lesions, lowered the serum levels of select hepatic enzyme markers (alanine aminotransferase, ALT, and aspartate aminotransferase, AST) and malondialdehyde and increased the activity of superoxide dismutase in liver. Histopathology of the liver tissues showed that PDG and G-M1 attenuated the hepatocellular necrosis and led to reduction of inflammatory cell infiltration. Therefore, the results of this study show that PDG and G-M1 can be proposed to protect the liver against CCl(4)-induced oxidative injury in mice, and the hepatoprotective effect might be attributed to amelioration of oxidative stress. 相似文献
992.
993.
994.
995.
Yan Gu Wen Chen Chuan-Zeng Zhang 《International Journal of Solids and Structures》2011,48(18):2549-2556
This study documents the first attempt to apply the singular boundary method (SBM), a novel boundary only collocation method, to two-dimensional (2D) elasticity problems. Unlike the method of fundamental solutions (MFS), the source points coincide with the collocation points on the physical boundary by using an inverse interpolation technique to regularize the singularity of the fundamental solution of the equation governing the problems of interest. Three benchmark elasticity problems are tested to demonstrate the feasibility and accuracy of the proposed method through detailed comparisons with the MFS, boundary element method (BEM), and finite element method (FEM). 相似文献
996.
997.
For 0≤k≤n, let be the entries in Euler’s difference table and let . Dumont and Randrianarivony showed equals the number of permutations on [n] whose fixed points are contained in {1,2,…,k}. Rakotondrajao found a combinatorial interpretation of the number in terms of k-fixed-points-permutations of [n]. We show that for any n≥1, the sequence is essentially 2-log-concave and reverse ultra log-concave. 相似文献
998.
文章研究了一类函数增量的局部渐近性质,发现这类函数增量的局部渐近性对于一元实函数,二元及多元实函数,向量值函数和复函数在一定条件下都会保持不变,进而提出了两个相关的猜想:此类函数增量的渐近性是关于函数变换的拓扑不变量。 相似文献
999.
Given an isotropic random vector X with log-concave density in Euclidean space
\mathbbRn{\mathbb{R}^n} , we study the concentration properties of |X| on all scales, both above and below its expectation. We show in particular that
l \mathbbP( | |X| - ?n | 3 t?n ) £ C exp ( -cn1/2 min(t3, t) ) "t 3 0, \begin{array}{l} \mathbb{P}\left ( \left | |X| - \sqrt{n} \right | \geq t\sqrt{n} \right ) \leq C \, {\rm exp} \left ( -cn^{1/2} {\rm min}(t^{3}, t) \right) \; \forall t \geq 0, \end{array} 相似文献
1000.
We present a partial first-order affine-scaling method for solving smooth optimization with linear inequality constraints. At each iteration, the algorithm considers a subset of the constraints to reduce the complexity. We prove the global convergence of the algorithm for general smooth objective functions, and show it converges at sublinear rate when the objective function is quadratic. Numerical experiments indicate that our algorithm is efficient. 相似文献
|