全文获取类型
收费全文 | 12744篇 |
免费 | 1873篇 |
国内免费 | 1920篇 |
专业分类
化学 | 6866篇 |
晶体学 | 215篇 |
力学 | 488篇 |
综合类 | 206篇 |
数学 | 1155篇 |
物理学 | 2874篇 |
无线电 | 4733篇 |
出版年
2024年 | 25篇 |
2023年 | 205篇 |
2022年 | 353篇 |
2021年 | 367篇 |
2020年 | 413篇 |
2019年 | 378篇 |
2018年 | 359篇 |
2017年 | 382篇 |
2016年 | 502篇 |
2015年 | 547篇 |
2014年 | 710篇 |
2013年 | 869篇 |
2012年 | 972篇 |
2011年 | 1061篇 |
2010年 | 946篇 |
2009年 | 907篇 |
2008年 | 1019篇 |
2007年 | 1021篇 |
2006年 | 944篇 |
2005年 | 713篇 |
2004年 | 615篇 |
2003年 | 509篇 |
2002年 | 493篇 |
2001年 | 419篇 |
2000年 | 341篇 |
1999年 | 247篇 |
1998年 | 198篇 |
1997年 | 155篇 |
1996年 | 124篇 |
1995年 | 100篇 |
1994年 | 80篇 |
1993年 | 92篇 |
1992年 | 75篇 |
1991年 | 62篇 |
1990年 | 56篇 |
1989年 | 37篇 |
1988年 | 32篇 |
1987年 | 36篇 |
1986年 | 24篇 |
1985年 | 25篇 |
1984年 | 16篇 |
1983年 | 20篇 |
1982年 | 12篇 |
1981年 | 11篇 |
1980年 | 14篇 |
1979年 | 5篇 |
1978年 | 7篇 |
1976年 | 5篇 |
1969年 | 3篇 |
1928年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 703 毫秒
971.
The global responses characteristics of a rotor/stator rubbing system with dry friction effects 总被引:2,自引:0,他引:2
Rotor/stator rubbing systems may undertake a number of quite different responses. Recent experiments on rotor/stator rubbing have revealed that two or three different responses may coexist. In this paper the global response characteristics of a general rotor/stator rubbing system, which takes into account the dominant factors in the process of rotor/stator rubbing, especially, the dry friction effect that is mostly neglected in the previous works and is the main factor for the self-excited dry friction backward whirl, are studied. The different solutions of the piecewise nonlinear system are derived and their stability are analyzed to get the existence boundaries of the different responses. An overall picture of the global response characteristics of this model is then obtained by drawing the existence boundaries in a same parameter space. The present results provide good understanding on the coexistence of different rubbing responses observed in tests. Moreover, deeper insight into the types of coexistence of different rubbing responses and their relationship with the system parameters is gained. 相似文献
972.
In this article, we consider a stochastic hydrodynamical equation in Heisenberg paramagnet driven by additive noise. We prove
the existence and uniqueness of smooth solutions to this equation with difference method. 相似文献
973.
葛洵 《纯粹数学与应用数学》2010,26(3)
证明了如果空间类κ为D-空间类或闭遗传不可约空间类,则I(κ)(∈)κ.这一结果对于κ为D空间类和闭遗传不可约空间类,肯定地回答了I(κ)是否包含I2(κ)问题. 相似文献
974.
975.
Influence of non-gelling methylcellulose(MC)on gelation behavior of wheat gliadins in 13 wt%alkaline propanol/water(50:50, v/v)solution was investigated using dynamic rheological time sweep test.Increasing MC concentration(C_(MC))up to C_(MC)=1wt% caused a significant reduction in gelation time(t_(gel))of the solution and an increase in loss tangent(tanδ)value of the resultant gel at T<30℃. 相似文献
976.
A number of novel strobilurin analogues containing substituted N-phenylpyrimidin-2-amines were synthesized.The structures of these new compounds were confirmed by ~1H NMR,IR and elemental analysis.Biological evaluation in the greenhouse showed several compounds have good fungicidal activities at 25 mg/L. 相似文献
977.
The expansion coefficient CD|L| of Coulomb potential 1/r12 of atomic system in hyper‐spherical harmonics is derived and the explicit expression is given. 相似文献
978.
979.
980.
Two new secolignans from the roots of Urtica mairei Levl. 总被引:1,自引:0,他引:1
Twonew secolignans(1 and 2)were isolated from the roots of Urtica mairei Levl.The structures of these two compounds were determined on the basis of extensive spectroscopic methods including HR-E1-MS.1D and 2D NMR experiments. 相似文献