全文获取类型
收费全文 | 84471篇 |
免费 | 688篇 |
国内免费 | 404篇 |
专业分类
化学 | 28622篇 |
晶体学 | 817篇 |
力学 | 6851篇 |
数学 | 32844篇 |
物理学 | 16429篇 |
出版年
2023年 | 67篇 |
2021年 | 97篇 |
2020年 | 130篇 |
2019年 | 136篇 |
2018年 | 10493篇 |
2017年 | 10306篇 |
2016年 | 6290篇 |
2015年 | 1072篇 |
2014年 | 510篇 |
2013年 | 676篇 |
2012年 | 4188篇 |
2011年 | 10907篇 |
2010年 | 5894篇 |
2009年 | 6285篇 |
2008年 | 6951篇 |
2007年 | 9048篇 |
2006年 | 556篇 |
2005年 | 1655篇 |
2004年 | 1814篇 |
2003年 | 2183篇 |
2002年 | 1167篇 |
2001年 | 329篇 |
2000年 | 356篇 |
1999年 | 204篇 |
1998年 | 228篇 |
1997年 | 243篇 |
1996年 | 285篇 |
1995年 | 217篇 |
1994年 | 168篇 |
1993年 | 206篇 |
1992年 | 142篇 |
1991年 | 122篇 |
1990年 | 105篇 |
1989年 | 113篇 |
1988年 | 102篇 |
1987年 | 111篇 |
1986年 | 104篇 |
1985年 | 90篇 |
1984年 | 90篇 |
1983年 | 74篇 |
1982年 | 83篇 |
1981年 | 88篇 |
1980年 | 87篇 |
1979年 | 84篇 |
1978年 | 78篇 |
1977年 | 63篇 |
1976年 | 59篇 |
1974年 | 48篇 |
1973年 | 73篇 |
1914年 | 47篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Central European Journal of Operations Research - In this note, we consider the antibandwidth problem, also known as dual bandwidth problem, separation problem and maximum differential coloring... 相似文献
2.
Jared P. Klein Zachary M. Gdowski Richard A. Register 《Journal of polymer science. Part A, Polymer chemistry》2022,60(2):266-275
Though polynorbornene synthesized by ring-opening metathesis polymerization has an intrinsically all-cis configuration of the cyclopentylene backbone rings, a fraction of these rings can be epimerized to the trans configuration during hydrogenation over suitable catalysts. By varying the method of hydrogenation, semicrystalline hydrogenated polynorbornenes (hPNs) with trans levels between 0 and 36% were obtained. With increasing trans content, the glass transition temperature, melting point, and enthalpy of melting decrease modestly. By contrast, the temperature at which the hPN crystal transitions into a rotationally disordered polymorph varies strongly with trans content, ranging from 126 °C (all-cis) to 71 °C at 27% trans; at trans contents of 34% and above, no rotationally-ordered phase is observed at any temperature. The room-temperature Young's modulus shows no dependence on trans content, while the yield stress drops by 20% at 1% trans content and slowly decreases further with additional epimerization. The temperature dependence of the Young's modulus differs for trans-containing versus all-cis polymers, while the temperature dependence of the yield stress is set by the polymorph type (rotationally ordered vs. disordered). 相似文献
3.
4.
5.
<正>The generation of stretchable conductors is a mandatory precondition for the next-generation electronic devices including flexible, wearable electronics, smart skins and bioinspired devices [1–4]. This new class of electronic materials takes up external mechanical deformations and maintains structural integrity and electronic performance throughout bending, folding and stretching processes. Al- 相似文献
6.
Yuliang Zhao 《中国科学:化学(英文版)》2018,61(12):1481-1482
正Living organisms have developed their unique strategies during the natural evolution for building hard tissues with minerals, including silica, calcium carbonate, calcium phosphate, and ferric oxide [1]. Such biomineralized materials generally have complex hierarchical structures with excellent mechanical properties. Although bioinspired approaches have led to the creation of well-defined synthetic structural materials ranging from micro to macro scales, the rational design of discrete biomimetic structures at the nanoscale remains a grand challenge. 相似文献
7.
JuHong Ge 《Nonlinear dynamics》2018,94(1):87-98
A five-neuron network model with multiple delays is proposed. This paper presents the combined effect of different delays on the dynamics of the proposed network. Pitchfork bifurcation is discussed in detail with the variation of the value of coupled weight or attenuation rate of internal neurons. By analyzing the corresponding characteristic equation, some stable criteria on delay-dependence and delay-independence are derived including multiple delays and coupled weights and the periodic oscillation arises bifurcated from the trivial equilibrium after the network loses its stability. Stable regions on delay-dependence are displayed in the two delayed parameter plane. It is shown that multiple delays can produce stability switching between resting state and periodic activity. Finally, theoretical results are justified by providing two illustrative examples. 相似文献
8.
It is shown that the countably infinite dimensional pointed vector space (the vector space equipped with a constant) over a finite field has infinitely many first order definable reducts. This implies that the countable homogeneous Boolean-algebra has infinitely many reducts. 相似文献
9.
10.