全文获取类型
收费全文 | 4223篇 |
免费 | 340篇 |
国内免费 | 228篇 |
专业分类
化学 | 672篇 |
晶体学 | 7篇 |
力学 | 451篇 |
综合类 | 31篇 |
数学 | 814篇 |
物理学 | 1069篇 |
综合类 | 1747篇 |
出版年
2024年 | 8篇 |
2023年 | 42篇 |
2022年 | 66篇 |
2021年 | 68篇 |
2020年 | 108篇 |
2019年 | 84篇 |
2018年 | 91篇 |
2017年 | 112篇 |
2016年 | 125篇 |
2015年 | 100篇 |
2014年 | 225篇 |
2013年 | 218篇 |
2012年 | 211篇 |
2011年 | 254篇 |
2010年 | 240篇 |
2009年 | 289篇 |
2008年 | 297篇 |
2007年 | 301篇 |
2006年 | 274篇 |
2005年 | 283篇 |
2004年 | 240篇 |
2003年 | 197篇 |
2002年 | 144篇 |
2001年 | 137篇 |
2000年 | 98篇 |
1999年 | 76篇 |
1998年 | 69篇 |
1997年 | 66篇 |
1996年 | 48篇 |
1995年 | 39篇 |
1994年 | 38篇 |
1993年 | 30篇 |
1992年 | 30篇 |
1991年 | 27篇 |
1990年 | 27篇 |
1989年 | 25篇 |
1988年 | 28篇 |
1987年 | 11篇 |
1986年 | 15篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 8篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1976年 | 2篇 |
1971年 | 2篇 |
1955年 | 1篇 |
排序方式: 共有4791条查询结果,搜索用时 36 毫秒
1.
Martin Kellert Jan-Simon Jeshua Friedrichs Nadine Anke Ullrich Alexander Feinhals Jonas Tepper Peter Lnnecke Evamarie Hey-Hawkins 《Molecules (Basel, Switzerland)》2021,26(7)
The development of novel, tumor-selective and boron-rich compounds as potential agents for use in boron neutron capture therapy (BNCT) represents a very important field in cancer treatment by radiation therapy. Here, we report the design and synthesis of two promising compounds that combine meta-carborane, a water-soluble monosaccharide and a linking unit, namely glycine or ethylenediamine, for facile coupling with various tumor-selective biomolecules bearing a free amino or carboxylic acid group. In this work, coupling experiments with two selected biomolecules, a coumarin derivative and folic acid, were included. The task of every component in this approach was carefully chosen: the carborane moiety supplies ten boron atoms, which is a tenfold increase in boron content compared to the l-boronophenylalanine (l-BPA) presently used in BNCT; the sugar moiety compensates for the hydrophobic character of the carborane; the linking unit, depending on the chosen biomolecule, acts as the connection between the tumor-selective component and the boron-rich moiety; and the respective tumor-selective biomolecule provides the necessary selectivity. This approach makes it possible to develop a modular and feasible strategy for the synthesis of readily obtainable boron-rich agents with optimized properties for potential applications in BNCT. 相似文献
2.
4.
Natalia L. Calvo Sebastian O. SimonettiRubén M. Maggio Teodoro S. Kaufman 《Analytica chimica acta》2015
Exposure of cimetidine (CIM) to dry heat (160–180 °C) afforded, upon cooling, a glassy solid containing new and hitherto unknown products. The kinetics of this process was studied by a second order chemometrics-assisted multi-spectroscopic approach. Proton and carbon-13 nuclear magnetic resonance (NMR), as well as ultraviolet and infrared spectroscopic data were jointly used, whereas multivariate curve resolution with alternating least squares (MCR-ALS) was employed as the chemometrics method to extract process information. It was established that drug degradation follows a first order kinetics. 相似文献
5.
石清俊 《大庆师范学院学报》2004,24(3):1-5
政治控制是国家为了共同的价值目标对社会进行规约与调控的过程。政治控制的核心问题即是公共权力的合理性与合法性问题 ,并具有表现为政治权利运作的结构、方式、及其限度。对这一问题的理解为我们全面地认识政治控制这一范畴 ,提供了个新的视角 相似文献
6.
Fabio Fagnani Sandro Zampieri 《Transactions of the American Mathematical Society》1997,349(5):1993-2006
In this paper we study symbolic dynamics over alphabets which are modules over a principal ideal domain, considering topological shifts which are also submodules. Our main result is the classification, up to algebraic and topological conjugacy, of the torsion-free, transitive, finite memory shifts.
7.
We investigate the replica symmetry breaking (RSB) in a neighborhood of the instability point of the replica-symmetric solution in the axial quadrupolar glass model. We show that the solution with the first-stage RSB is stable against the subsequent RSB. Although there is no reflection symmetry, the first-stage RSB solution continuously bifurcates from the replica-symmetric one. This implies that our model does not belong to either of the two classes into which spin glasses are usually divided. 相似文献
8.
Based on the vectorial Rayleigh–Sommerfeld diffraction integrals, analytical expressions for the transversal and axial field distribution of plane waves propagating through a thin lens followed by a small circular aperture are derived and used to study the focusing and diffraction properties of plane waves. Some special cases of our general result are discussed, and illustrative numerical calculation results are given. It is found that the vectorial nonparaxial approach should be applied if the aperture dimension is comparable with the wavelength or the focusing is strong. 相似文献
9.
10.
对专科综合英语教学的探索与思考 总被引:1,自引:0,他引:1
康素霞 《曲靖师范学院学报》2002,21(2):93-95
综合英语教学是英语专业学习中的核心内容。文章就如何抓好专科综合英语教学中的语音基础及以学生为中心的教学模式展开探索与思考 相似文献