全文获取类型
收费全文 | 34867篇 |
免费 | 1267篇 |
国内免费 | 265篇 |
专业分类
化学 | 24687篇 |
晶体学 | 280篇 |
力学 | 684篇 |
综合类 | 1篇 |
数学 | 5963篇 |
物理学 | 4784篇 |
出版年
2023年 | 167篇 |
2022年 | 324篇 |
2021年 | 433篇 |
2020年 | 611篇 |
2019年 | 599篇 |
2018年 | 417篇 |
2017年 | 389篇 |
2016年 | 943篇 |
2015年 | 831篇 |
2014年 | 1007篇 |
2013年 | 1709篇 |
2012年 | 2181篇 |
2011年 | 2462篇 |
2010年 | 1330篇 |
2009年 | 1182篇 |
2008年 | 2275篇 |
2007年 | 2093篇 |
2006年 | 2119篇 |
2005年 | 1968篇 |
2004年 | 1687篇 |
2003年 | 1380篇 |
2002年 | 1335篇 |
2001年 | 486篇 |
2000年 | 469篇 |
1999年 | 408篇 |
1998年 | 398篇 |
1997年 | 419篇 |
1996年 | 449篇 |
1995年 | 314篇 |
1994年 | 368篇 |
1993年 | 335篇 |
1992年 | 303篇 |
1991年 | 279篇 |
1990年 | 244篇 |
1989年 | 210篇 |
1988年 | 210篇 |
1987年 | 221篇 |
1986年 | 180篇 |
1985年 | 376篇 |
1984年 | 331篇 |
1983年 | 280篇 |
1982年 | 342篇 |
1981年 | 277篇 |
1980年 | 288篇 |
1979年 | 240篇 |
1978年 | 227篇 |
1977年 | 217篇 |
1976年 | 208篇 |
1975年 | 186篇 |
1974年 | 160篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Mathematical Programming - We provide a control-theoretic perspective on optimal tensor algorithms for minimizing a convex function in a finite-dimensional Euclidean space. Given a function... 相似文献
2.
Cavitation erosion is caused in solids exposed to strong pressure waves developing in an adjacent fluid field. The knowledge of the transient distribution of stresses in the solid is important to understand the cause of damaging by comparisons with breaking points of the material. The modeling of this problem requires the coupling of the models for the fluid and the solid. For this purpose, we use a strategy based on the solution of coupled Riemann problems that has been originally developed for the coupling of 2 fluids. This concept is exemplified for the coupling of a linear elastic structure with an ideal gas. The coupling procedure relies on the solution of a nonlinear equation. Existence and uniqueness of the solution is proven. The coupling conditions are validated by means of quasi‐1D problems for which an explicit solution can be determined. For a more realistic scenario, a 2D application is considered where in a compressible single fluid, a hot gas bubble at low pressure collapses in a cold gas at high pressure near an adjacent structure. 相似文献
3.
4.
随着经济的飞速发展,社会对能源的需求日益扩大,对工业废水的无害化处理也提出了更高的要求。光催化燃料电池 (photocatalytic fuel cell, PFC) 在燃料电池中引入半导体光催化材料作为电极,实现了有机污染物高效降解和同步对外产电的双重功能,在废水无害化与资源化利用方面具有潜在的应用价值。半导体光催化电极是PFC系统高效运行的核心组件,增强其可见光响应和光生载流子分离是提高PFC性能的关键策略。反应器结构设计和运行参数优化也有利于改善PFC性能。本文从PFC基本原理和应用入手,综述了PFC在环境污染物资源化处理中的研究进展,并详细阐述了提高PFC的污染控制性能和产电效率的优化手段,为进一步设计高效稳定的PFC系统并实现其在水污染控制和清洁能源生产中的应用提供理论指导。 相似文献
5.
Synthesis of diisocyanides with phenolic groups and their polymerization to helically chiral poly(quinoxaline‐2,3‐diyl)s 下载免费PDF全文
Johannes Scholz Michael Reggelin 《Journal of polymer science. Part A, Polymer chemistry》2015,53(11):1320-1329
The development of synthetic routes which lead to five new diisocyanide monomers with one or two phenolic groups is described. Their polymerization behavior is studied with Pd‐ and Ni‐based initiators, as well as under microwave irradiation. The polymerizability is mainly dominated by steric effects as is concluded from experiments using different protecting groups. Chiroptical properties of these new polymers are studied by CD‐spectroscopy. After deprotection, helically chiral poly(quinoxalin‐2,3‐diyl)s are obtained which display a Brønsted function attached to a stereolabile biaryl axis whose configuration should be influenced by the chiral polymer backbone. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1320–1329 相似文献
6.
7.
8.
Mourad Kainane Mezadek Mohamed Kainane Mezadek Michael Reissig 《Mathematical Methods in the Applied Sciences》2020,43(6):3117-3147
In this paper, we study the global (in time) existence of small data solutions to the Cauchy problem for the semilinear wave equation with friction, viscoelastic damping, and a power nonlinearity. We are interested in the connection between regularity assumptions for the data and the admissible range of exponents p in the power nonlinearity. 相似文献
9.
10.
Amphiphilic thermoset elastomers from metal‐free,click crosslinking of PEG‐grafted silicone surfactants 下载免费PDF全文
Michael A. Brook Frances Lasowski Heather Sheardown 《Journal of polymer science. Part A, Polymer chemistry》2015,53(9):1082-1093
The hydrophobicity of silicone elastomers can compromise their utility in some biomaterials applications. Few effective processes exist to introduce hydrophilic groups onto a polysiloxane backbone and subsequently crosslink the material into elastomers. This problem can be overcome through the utilization of metal‐free click reactions between azidoalkylsilicones and alkynyl‐modified silicones and/or PEGs to both functionalize and crosslink silicone elastomers. Alkynyl‐functional PEG was clicked onto a fraction of the available azido groups of a functional polysiloxane, yielding azido reactive PDMS‐g‐PEG rake surfactants. The reactive polymers were then used to crosslink alkynyl‐terminated PDMS of different molecular weights. Using simple starting materials, this generic yet versatile method permits the preparation and characterization of a library of amphiphilic thermoset elastomers that vary in their composition, crosslink density, elasticity, hydrogel formation, and wettability. An appropriate balance of PEG length and crosslink density leads to a permanently highly wettable silicone elastomer that demonstrated very low levels of protein adsorption. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1082–1093 相似文献