全文获取类型
收费全文 | 4566篇 |
免费 | 138篇 |
国内免费 | 16篇 |
专业分类
化学 | 2882篇 |
晶体学 | 14篇 |
力学 | 236篇 |
数学 | 797篇 |
物理学 | 791篇 |
出版年
2023年 | 50篇 |
2022年 | 138篇 |
2021年 | 132篇 |
2020年 | 109篇 |
2019年 | 98篇 |
2018年 | 82篇 |
2017年 | 91篇 |
2016年 | 185篇 |
2015年 | 145篇 |
2014年 | 139篇 |
2013年 | 245篇 |
2012年 | 258篇 |
2011年 | 289篇 |
2010年 | 172篇 |
2009年 | 149篇 |
2008年 | 281篇 |
2007年 | 268篇 |
2006年 | 222篇 |
2005年 | 236篇 |
2004年 | 162篇 |
2003年 | 156篇 |
2002年 | 113篇 |
2001年 | 49篇 |
2000年 | 48篇 |
1999年 | 44篇 |
1998年 | 32篇 |
1997年 | 31篇 |
1996年 | 54篇 |
1995年 | 44篇 |
1994年 | 40篇 |
1993年 | 34篇 |
1992年 | 28篇 |
1991年 | 27篇 |
1990年 | 28篇 |
1989年 | 29篇 |
1988年 | 29篇 |
1987年 | 39篇 |
1986年 | 23篇 |
1985年 | 39篇 |
1984年 | 38篇 |
1983年 | 20篇 |
1982年 | 21篇 |
1981年 | 26篇 |
1980年 | 27篇 |
1979年 | 20篇 |
1978年 | 16篇 |
1977年 | 28篇 |
1975年 | 16篇 |
1974年 | 13篇 |
1858年 | 11篇 |
排序方式: 共有4720条查询结果,搜索用时 15 毫秒
1.
Journal of Optimization Theory and Applications - Pollution management models of Shallow Lake type identify a well-known class of infinite horizon optimal control problems, characterized by the... 相似文献
2.
3.
Numerical Algorithms - We introduce a modulus-based formulation for vertical linear complementarity problems (VLCPs) with an arbitrary number ? of matrices. This formulation can be used to... 相似文献
4.
Vito Gigante Laura Aliotta Maria Beatrice Coltelli Patrizia Cinelli Luigi Botta Francesco Paolo La Mantia Andrea Lazzeri 《Journal of polymer science. Part A, Polymer chemistry》2020,58(23):3264-3282
The development of biodegradable materials for tailored applications, particularly in the field of polymeric films and sheets, is a challenging technological goal as well as a contribution to help protect the environment. Poly(lactic) acid (PLA) is a promising substitute for several oil-based polymers; however, to overcome its thermal and mechanical drawbacks, researchers have developed solutions such as blending PLA with polybutylene adipate terephthalate (PBAT), which is capable of increasing the ductility of the final material. In this study, PLA/PBAT binary blends, with minimum possible content of nonrenewable materials, were examined from processing, thermal, morphological, and rheological perspective. An optimized PLA/PBAT ratio was chosen as the polymeric basis to obtain a biodegradable formulation by adding a biobased plasticizer and appropriate fillers to produce a micrometer film with tailored flexibility and tear resistance. The processing technology involved flat-die extrusion, followed by calendering. The tearing resistance of the produced film was investigated, and the results were compared with literature data. A study on the essential work of fracture was implemented to explore the mode III out-of-plane fracture resistance starting from a trouser tear test. 相似文献
5.
6.
The concept of strong interactions need not be limited to the sector of physics taken by QCD. While this domain is investigated by RHIC, LHC will be able to probe potential new strong interactions simultaneously: Finding the precise mechanism for electroweak symmetry breaking is one of the prime problems of physics. Intricately linked to this point is the question after the true nature or even the existence of the Higgs boson. Here, we present stronly interacting theories providing an explanation for the hierarchy problem and leading to a light composite Higgs boson, favoured by experimental data. Our variation of the standard model is consistent with precision data. We achieve this accordance by using technifermions in a higher representation of their gauge group. Anomaly conditions require at least one extra lepton family for some of the theories whereby they contain a natural dark matter candidate. We can accurately determine the masses of said leptons from experimental data. 相似文献
7.
Franca M. Cordero Francesco De Sarlo Alberto Brandi 《Monatshefte für Chemie / Chemical Monthly》2004,40(2):649-669
The review outlines the various different azaheterocycles available from 5-spirocyclopropane isoxazolidines. These compounds can be regarded as versatile direct precursors of tetrahydro-, dihydropyridone and azetidinone derivatives. The current scope and limitations, and the selectivity aspects of the different processes are discussed therein. 相似文献
8.
A new microwave dielectric method for studying photoinitiated chain radical polymerization processes
Carlo Carlini Francesco Ciardelli Pier Angelo Rolla Elpidio Tombari 《Journal of Polymer Science.Polymer Physics》1987,25(6):1253-1261
Measurements of both real and imaginary parts of the dielectric constant at a fixed microwave frequency have been performed on n-butyl acrylate/poly(n-butyl acrylate) mixtures. The dielectric constant of the mixtures has been compared with that of neat n-butyl acrylate during UV photoinitiated polymerization. The values of the imaginary part of the dielectric constant thus obtained have allowed determination of the instantaneous monomer concentration and verified the kinetic equation for the photoinitiated polymerization process. The limits of validity of the method as well as its capability of providing detailed kinetic information are also discussed. 相似文献
9.
Francesco Catoni Roberto Cannata Paolo Zampetti 《Advances in Applied Clifford Algebras》2006,16(2):85-101
It is known that complex numbers can be associated with plane Euclidean geometry and their functions are successfully used
for studying extensions of Euclidean geometry, i.e., non-Euclidean geometries and surfaces differential geometry.
In this paper we begin to study the constant curvature spaces associated with the geometry generated by commutative elliptic-quaternions
and we show how the “mathematics” they generate allows us to introduce these spaces and obtain the geodesic equations without
developing a complete mathematical apparatus as the one developed for Riemannian geometry. 相似文献
10.