全文获取类型
收费全文 | 6501篇 |
免费 | 891篇 |
国内免费 | 527篇 |
专业分类
化学 | 2666篇 |
晶体学 | 1153篇 |
力学 | 470篇 |
综合类 | 102篇 |
数学 | 1367篇 |
物理学 | 2161篇 |
出版年
2024年 | 7篇 |
2023年 | 67篇 |
2022年 | 151篇 |
2021年 | 182篇 |
2020年 | 205篇 |
2019年 | 155篇 |
2018年 | 119篇 |
2017年 | 179篇 |
2016年 | 282篇 |
2015年 | 217篇 |
2014年 | 348篇 |
2013年 | 466篇 |
2012年 | 365篇 |
2011年 | 488篇 |
2010年 | 444篇 |
2009年 | 439篇 |
2008年 | 471篇 |
2007年 | 476篇 |
2006年 | 448篇 |
2005年 | 361篇 |
2004年 | 336篇 |
2003年 | 273篇 |
2002年 | 192篇 |
2001年 | 161篇 |
2000年 | 180篇 |
1999年 | 139篇 |
1998年 | 130篇 |
1997年 | 129篇 |
1996年 | 73篇 |
1995年 | 62篇 |
1994年 | 62篇 |
1993年 | 47篇 |
1992年 | 42篇 |
1991年 | 47篇 |
1990年 | 35篇 |
1989年 | 26篇 |
1988年 | 26篇 |
1987年 | 16篇 |
1986年 | 13篇 |
1985年 | 16篇 |
1984年 | 11篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1973年 | 2篇 |
1959年 | 2篇 |
排序方式: 共有7919条查询结果,搜索用时 31 毫秒
91.
设计了一套具有一定实用意义和科学价值的薄膜生长荧光显微图像实时采集与分析系统,可以实现透明衬底上有机荧光分子薄膜生长的实时原位监测。进一步阐明了系统的硬件构筑思路和软件设计架构,并依据薄膜的形貌特征,给出8个主要生长信息参数及其求取算法,并利用自行搭建的实验系统,针对联六苯(p-6P)分子在云母衬底上的纳米纤维生长过程,得出了其准一维的线性生长规律。该系统作为重要的薄膜生长成像监测技术,有望在薄膜与衬底表面相互作用和衬底微区结构特性研究等方面起到积极的作用。 相似文献
92.
93.
94.
A priori bounds and multiplicity for fully nonlinear equations with quadratic growth in the gradient
We consider fully nonlinear uniformly elliptic equations with quadratic growth in the gradient, such asin a bounded domain with a Dirichlet boundary condition; here , , , and the matrix M satisfies . Recently this problem was studied in the “coercive” case , where uniqueness of solutions can be expected; and it was conjectured that the solution set is more complex for noncoercive equations. This conjecture was verified in 2015 by Arcoya, de Coster, Jeanjean and Tanaka for equations in divergence form, by exploiting the integral formulation of the problem. Here we show that similar phenomena occur for general, even fully nonlinear, equations in nondivergence form. We use different techniques based on the maximum principle.We develop a new method to obtain the crucial uniform a priori bounds, which permit to us to use degree theory. This method is based on basic regularity estimates such as half-Harnack inequalities, and on a Vázquez type strong maximum principle for our kind of equations. 相似文献
95.
96.
In this work, we reported the effect of Li2CO3 addition on the structural, optical, ferroelectric properties and electric-field-induced strain of Bi0.5(Na,K)0.5TiO3 (BNKT) solid solution with CaZrO3 ceramics. Both rhombohedral and tetragonal structures were distorted after adding Lithium (Li). The band gap values decreased from 2.91 to 2.69 eV for 5 mol% Li-addition. The maximum polarization and remanent polarization decreased from 49.66 μC/cm2 to 27.11 μC/cm2 and from 22.93 μC/cm2 to 5.35 μC/cm2 for un-doped and 5 mol% Li- addition BNKT ceramics, respectively. The maximum Smax/Emax value was 567 pm/V at 2 mol% Li2CO3 access. We expected this work will help to understand the role of A-site dopant in lead-free ferroelectric BNKT materials. 相似文献
97.
98.
Dr. María Jose Capitán Dr. Jesús Álvarez Dr. Yang Wang Dr. Roberto Otero Dr. Manuel Alcamí Prof. Fernando Martín Prof. Rodolfo Miranda 《Chemphyschem》2013,14(14):3294-3302
The structure and stability of adenine crystals and thin layers has been studied by using scanning tunneling microscopy, X‐ray diffraction, and density functional theory calculations. We have found that adenine crystals can be grown in two phases that are energetically quasi‐degenerate, the structure of which can be described as a pile‐up of 2D adenine planes. In each plane, the structure can be described as an aggregation of adenine dimers. Under certain conditions, kinetic effects can favor the growth of the less stable phase. These results have been used to understand the growth of adenine thin films on gold under ultra‐high vacuum conditions. We have found that the grown phase corresponds to the α‐phase, which is composed of stacked prochiral planes. In this way, the adenine nanocrystals exhibit a surface that is enantiopure. These results could open new insight into the applications of adenine in biological, medical, and enantioselective or pharmaceutical fields. 相似文献
99.
100.