全文获取类型
收费全文 | 15282篇 |
免费 | 632篇 |
国内免费 | 67篇 |
专业分类
化学 | 10562篇 |
晶体学 | 106篇 |
力学 | 440篇 |
数学 | 2479篇 |
物理学 | 2394篇 |
出版年
2023年 | 111篇 |
2022年 | 155篇 |
2021年 | 271篇 |
2020年 | 291篇 |
2019年 | 285篇 |
2018年 | 291篇 |
2017年 | 243篇 |
2016年 | 582篇 |
2015年 | 483篇 |
2014年 | 483篇 |
2013年 | 982篇 |
2012年 | 1026篇 |
2011年 | 1133篇 |
2010年 | 618篇 |
2009年 | 571篇 |
2008年 | 1012篇 |
2007年 | 970篇 |
2006年 | 883篇 |
2005年 | 791篇 |
2004年 | 642篇 |
2003年 | 562篇 |
2002年 | 554篇 |
2001年 | 279篇 |
2000年 | 251篇 |
1999年 | 180篇 |
1998年 | 157篇 |
1997年 | 165篇 |
1996年 | 193篇 |
1995年 | 123篇 |
1994年 | 144篇 |
1993年 | 143篇 |
1992年 | 122篇 |
1991年 | 84篇 |
1990年 | 83篇 |
1989年 | 78篇 |
1988年 | 65篇 |
1987年 | 69篇 |
1986年 | 52篇 |
1985年 | 102篇 |
1984年 | 118篇 |
1983年 | 75篇 |
1982年 | 79篇 |
1981年 | 58篇 |
1980年 | 62篇 |
1979年 | 38篇 |
1978年 | 52篇 |
1977年 | 43篇 |
1976年 | 25篇 |
1975年 | 28篇 |
1974年 | 30篇 |
排序方式: 共有10000条查询结果,搜索用时 703 毫秒
981.
In this paper we deal with a slight modification of the extended rapid transit network design problem to allow circular lines. A two-stage approach is proposed for solving this problem. In the first stage, an integer model is solved for selecting the stations to be constructed and the links between them. It drastically reduces the dimension of a modification of a 0–1 model given in the literature to adapt it to our problem. In the second stage, the line design problem is solved by means of a procedure that assigns each selected link to exactly one line under certain constraints. We report some computational experiments that show that our approach also produces a drastic reduction on the computational effort required for solving the modification of the 0–1 model given in the literature. 相似文献
982.
983.
Antonio Gaudiello Rejeb Hadiji 《Calculus of Variations and Partial Differential Equations》2010,39(3-4):593-619
In this paper, starting from the classical 3D micromagnetic energy, we determine, via an asymptotic analysis, the free energy of two joined ferromagnetic thin films. We distinguish different regimes depending on the limit of the ratio between the small thicknesses of the two films. 相似文献
984.
985.
ZDM – Mathematics Education - Our article aims to show how illuminating mathematical work as a concept from didactics of mathematics is useful in understanding issues relating to proving and... 相似文献
986.
987.
988.
989.
Ana Erica Paramo Susana Palmero Aranzazu Heras Alvaro Colina David Ibañez 《Electroanalysis》2016,28(4):890-897
The purpose of this work is to develop simple and reproducible ways to fabricate carbon nanofibers (CNFs) electrodes. Disposable CNFs electrodes were fabricated after filtering CNFs through polytetrafluoroethylene filters (PTFE), using directly as electrodes these filters with the CNFs film. The electrochemical behaviour of CNFs/PTFE electrodes were tested with ferrocenemethanol and tris(2,2′‐bypyridyl)dichlororuthenium(II) (Ru(bipy)32+). As a proof of concept of the analytical usefulness of the CNFs/PFTE electrodes, the study of vitamin B12 was carried out. Multivariate calibrate has been successfully used to determine vitamin B12 in a complex medium with vitamins B1 and B6 as interferents. 相似文献
990.
Antonio Di Martino Pavel Kucharczyk Zdenka Capakova Petr Humpolicek Vladimir Sedlarik 《Journal of nanoparticle research》2017,19(2):71
In the presented work, amphiphilic nanoparticles based on chitosan and carboxy-enriched polylactic acid have been prepared to improve the stability of the pro-drug temozolomide in physiological media by encapsulation. The carrier, with a diameter in the range of 150–180 nm, was able to accommodate up to 800 μg of temozolomide per mg of polymer. The obtained formulation showed good stability in physiological condition and preparation media up to 1 month. Temozolomide loaded inside the carrier exhibited greater stability than the free drug, in particular in simulated physiological solution at pH 7.4 where the hydrolysis in the inactive metabolite was clearly delayed. CS-SPLA nanoparticles demonstrated a pH-dependent TMZ release kinetics with the opportunity to increase or decrease the rate. Mass spectroscopy, UV-Vis analysis, and in vitro cell tests confirmed the improvement in temozolomide stability and effectiveness when loaded into the polymeric carrier, in comparison with the free drug. 相似文献