全文获取类型
收费全文 | 20982篇 |
免费 | 2091篇 |
国内免费 | 2169篇 |
专业分类
化学 | 963篇 |
晶体学 | 14篇 |
力学 | 1431篇 |
综合类 | 529篇 |
数学 | 19232篇 |
物理学 | 3073篇 |
出版年
2024年 | 19篇 |
2023年 | 210篇 |
2022年 | 215篇 |
2021年 | 322篇 |
2020年 | 451篇 |
2019年 | 515篇 |
2018年 | 525篇 |
2017年 | 600篇 |
2016年 | 653篇 |
2015年 | 454篇 |
2014年 | 902篇 |
2013年 | 1533篇 |
2012年 | 926篇 |
2011年 | 1202篇 |
2010年 | 1097篇 |
2009年 | 1394篇 |
2008年 | 1476篇 |
2007年 | 1554篇 |
2006年 | 1312篇 |
2005年 | 1212篇 |
2004年 | 972篇 |
2003年 | 985篇 |
2002年 | 925篇 |
2001年 | 748篇 |
2000年 | 806篇 |
1999年 | 688篇 |
1998年 | 635篇 |
1997年 | 566篇 |
1996年 | 410篇 |
1995年 | 322篇 |
1994年 | 261篇 |
1993年 | 204篇 |
1992年 | 151篇 |
1991年 | 129篇 |
1990年 | 125篇 |
1989年 | 72篇 |
1988年 | 56篇 |
1987年 | 48篇 |
1986年 | 51篇 |
1985年 | 67篇 |
1984年 | 71篇 |
1983年 | 29篇 |
1982年 | 63篇 |
1981年 | 36篇 |
1980年 | 40篇 |
1979年 | 43篇 |
1978年 | 43篇 |
1977年 | 36篇 |
1976年 | 21篇 |
1974年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
3.
The row iterative method is popular in solving the large‐scale ill‐posed problems due to its simplicity and efficiency. In this work we consider the randomized row iterative (RRI) method to tackle this issue. First, we present the semiconvergence analysis of RRI method for the overdetermined and inconsistent system, and derive upper bounds for the noise error propagation in the iteration vectors. To achieve a least squares solution, we then propose an extended version of the RRI (ERRI) method, which in fact can converge in expectation to the solution of the overdetermined or underdetermined, consistent or inconsistent systems. Finally, some numerical examples are given to demonstrate the convergence behaviors of the RRI and ERRI methods for these types of linear system. 相似文献
4.
5.
Given a graph sequence denote by T3(Gn) the number of monochromatic triangles in a uniformly random coloring of the vertices of Gn with colors. In this paper we prove a central limit theorem (CLT) for T3(Gn) with explicit error rates, using a quantitative version of the martingale CLT. We then relate this error term to the well-known fourth-moment phenomenon, which, interestingly, holds only when the number of colors satisfies . We also show that the convergence of the fourth moment is necessary to obtain a Gaussian limit for any , which, together with the above result, implies that the fourth-moment condition characterizes the limiting normal distribution of T3(Gn), whenever . Finally, to illustrate the promise of our approach, we include an alternative proof of the CLT for the number of monochromatic edges, which provides quantitative rates for the results obtained in [7]. 相似文献
6.
Feng Cheng Shuqi Wu Wenwei Zheng Shengqun Su Takumi Nakanishi Wenhuang Xu Pritam Sadhukhan Hibiki Sejima Shimon Ikenaga Kaoru Yamamoto Kaige Gao Shinji Kanegawa Prof. Osamu Sato 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(59):e202202161
The crystallization of a complex having electron transfer properties in a polar space group can induce the polarization switching of a crystal in a specific direction, which is attractive for the development of sensors, memory devices, and capacitors. Unfortunately, the probability of crystallization in a polar space group is usually low. Noticing that enantiopure compounds crystallize in Sohncke space groups, this paper reports a strategy for the molecular design of non-ferroelectric polarization switching crystals based on the use of intramolecular electron transfer and chirality. In addition, this paper describes the synthesis of a mononuclear valence tautomeric (VT) cobalt complex bearing an enantiopure ligand. The introduction of enantiomer enables the crystallization of the complex in the polar space group (P21). The polarization of the crystals along the b-axis direction is not canceled out and the VT transition is accompanied by a change in the macroscopic polarization of the polar crystal. Polarization switching via electron transfer is realized at around room temperature. 相似文献
7.
8.
Hasan Kara Muhammad Aamir Ali Hüseyin Budak 《Mathematical Methods in the Applied Sciences》2021,44(1):104-123
In this paper, we define interval‐valued left‐sided and right‐sided generalized fractional double integrals. We establish inequalities of Hermite‐Hadamard like for coordinated interval‐valued convex functions by applying our newly defined integrals. 相似文献
9.
探讨了经济增长及金融发展与城乡收入差距之间互动影响,刻画了三者间的逻辑关系,并基于广西1990-2017年的统计数据,运用状态空间模型及卡尔曼滤波算法对三者间动态关系进行了实证分析.结果显示:经济增长对城乡收入差距呈现倒U型曲线形态,而金融发展则显示出具有不断缩小城乡收入差距的趋势. 相似文献
10.
在完备的度量空间中,讨论了一类新型的非线性压缩映射ρ(Tx,Ty)≤a(ρ(x,y))ρ(x,Tx)+b(ρ(x,y))ρ(y,Ty)+c(ρ(x,y))ρ(x,y)通过构造迭代序列,指出该映射的不动点的存在性和唯一性,并给出相应的误差估计式,拓展和改进了有关文献的范围. 相似文献