全文获取类型
收费全文 | 1245篇 |
免费 | 205篇 |
国内免费 | 111篇 |
专业分类
化学 | 652篇 |
晶体学 | 17篇 |
力学 | 50篇 |
综合类 | 25篇 |
数学 | 190篇 |
物理学 | 627篇 |
出版年
2024年 | 4篇 |
2023年 | 28篇 |
2022年 | 47篇 |
2021年 | 50篇 |
2020年 | 41篇 |
2019年 | 24篇 |
2018年 | 37篇 |
2017年 | 36篇 |
2016年 | 49篇 |
2015年 | 43篇 |
2014年 | 62篇 |
2013年 | 64篇 |
2012年 | 84篇 |
2011年 | 99篇 |
2010年 | 80篇 |
2009年 | 75篇 |
2008年 | 75篇 |
2007年 | 55篇 |
2006年 | 50篇 |
2005年 | 51篇 |
2004年 | 44篇 |
2003年 | 50篇 |
2002年 | 38篇 |
2001年 | 36篇 |
2000年 | 24篇 |
1999年 | 43篇 |
1998年 | 47篇 |
1997年 | 39篇 |
1996年 | 30篇 |
1995年 | 30篇 |
1994年 | 23篇 |
1993年 | 21篇 |
1992年 | 13篇 |
1991年 | 12篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 12篇 |
1986年 | 12篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 7篇 |
1978年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有1561条查询结果,搜索用时 15 毫秒
991.
Hui Fang Pi Zhi Hong Zhong Han Li Ruan Peng Zhang Yong Hui Zhang Ji Zhou Wu 《中国化学快报》2008,19(7):835-836
A new hopane triterpenoid, hopane 22, 29-diol-29-formate (1), has been isolated from the whole herbs of Saxiglossum angustissimum (Cries.) Ching and its structure has been successfully determined on the basis of spectroscopic evidences. 相似文献
992.
提出了第三代同步辐射光源中的低温超导电流扭摆器和室温水冷电流扭摆器的物理设计方案。文中还讨论了电流扭摆器内腔中的磁场的分布特性,测量方法和电流扭摆器的制造技术的可行性。 相似文献
993.
994.
Shujuan Guo Jiong Ruan Lijuan Li Aifen Fang 《Communications in Nonlinear Science & Numerical Simulation》1998,3(4):248-251
We establish sufficient conditions for asymptotical stability of some nonlinear systems with delay which include populations systems by using Lyapunov functional. Furthermore, we get the results of global stability of these systems when the delays are less than the critical values. 相似文献
995.
低重复率的Ti:Al2O3飞秒激光放大器研究 总被引:5,自引:1,他引:4
本文报道了重复频率为10Hz的Ti:Al2O3飞秒激光放大器的研究.基于脉冲啁啾放大技术和采用再生/多通放大装置,得到了能量为8mJ的放大光脉冲,在该放大系统中,激光脉冲获M净增益约8×107. 相似文献
996.
997.
An epidemic model with a constant removal rate of infective individuals is proposed to understand the effect of limited resources for treatment of infectives on the disease spread. It is found that it is unnecessary to take such a large treatment capacity that endemic equilibria disappear to eradicate the disease. It is shown that the outcome of disease spread may depend on the position of the initial states for certain range of parameters. It is also shown that the model undergoes a sequence of bifurcations including saddle-node bifurcation, subcritical Hopf bifurcation, and homoclinic bifurcation. 相似文献
998.
Enguo Gu Jiong Ruan Zhenxun Huang 《Communications in Nonlinear Science & Numerical Simulation》1998,3(4):242-247
In this paper, a problem of stabilizing a period-T orbit in discrete chaotic m degree polynomial dynamical systems is studied. The aim is to present a new method for determining the neighborhood of a period-T point in which the system remains stable when subjected to a linear feedback control. A theorem on the existence of neighborhood is rigorously proved using idea from functional analysis and polar coordinate transformation. The ways of implementing the obtained theorem in the Hénon map are proposed. The validity of this method is shown by numerical simulation. 相似文献
999.
For any complete noncompact Kähler manifold with nonnegative and bounded holomorphic bisectional curvature, we provide the necessary and sufficient condition for the immortal solution to the Ricci flow. 相似文献
1000.
General formulae for the transient evolution of the susceptibility (absorption) induced by the quantum interference effect in a four-level N-type EIT medium is presented. The influence of the signal light on the transient susceptibility for the probe beam is studied for two typical cases when the strength of the coupling beam is much greater or less than that of the signal field. An interesting level reciprocity relationship between these two cases is found. 相似文献