全文获取类型
收费全文 | 85341篇 |
免费 | 749篇 |
国内免费 | 411篇 |
专业分类
化学 | 29466篇 |
晶体学 | 804篇 |
力学 | 6894篇 |
数学 | 33204篇 |
物理学 | 16133篇 |
出版年
2023年 | 77篇 |
2022年 | 112篇 |
2021年 | 135篇 |
2020年 | 189篇 |
2019年 | 191篇 |
2018年 | 10500篇 |
2017年 | 10334篇 |
2016年 | 6380篇 |
2015年 | 1142篇 |
2014年 | 573篇 |
2013年 | 766篇 |
2012年 | 4290篇 |
2011年 | 11060篇 |
2010年 | 5973篇 |
2009年 | 6326篇 |
2008年 | 7036篇 |
2007年 | 9152篇 |
2006年 | 634篇 |
2005年 | 1689篇 |
2004年 | 1852篇 |
2003年 | 2263篇 |
2002年 | 1276篇 |
2001年 | 408篇 |
2000年 | 402篇 |
1999年 | 269篇 |
1998年 | 281篇 |
1997年 | 244篇 |
1996年 | 297篇 |
1995年 | 199篇 |
1994年 | 133篇 |
1993年 | 154篇 |
1992年 | 105篇 |
1991年 | 97篇 |
1990年 | 85篇 |
1989年 | 87篇 |
1988年 | 92篇 |
1987年 | 83篇 |
1986年 | 88篇 |
1985年 | 70篇 |
1984年 | 64篇 |
1983年 | 50篇 |
1982年 | 63篇 |
1981年 | 54篇 |
1980年 | 64篇 |
1979年 | 54篇 |
1978年 | 55篇 |
1914年 | 45篇 |
1912年 | 41篇 |
1909年 | 42篇 |
1908年 | 41篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
In the paper, the authors establish several integral representations for the generating functions of the large and little Schröder numbers and for the large and little Schröder numbers. 相似文献
2.
Mesoscopic modeling at the pore scale offers great promise in exploring the underlying structure transport performance of flow through porous media. The present work studies the fluid flow subjected to capillarity-induced resonance in porous media characterized by different porous structure and wettability. The effects of porosity and wettability on the displacement behavior of the fluid flow through porous media are discussed. The results are presented in the form of temporal evolution of percentage saturation and displacement of the fluid front through porous media. The present study reveals that the vibration in the form of acoustic excitation could be significant in the mobilization of fluid through the porous media. The dependence of displacement of the fluid on physicochemical parameters like wettability of the surface, frequency along with the porosity is analyzed. It was observed that the mean displacement of the fluid is more in the case of invading fluid with wetting phase where the driving force strength is not so dominant. 相似文献
3.
4.
Sarah Peluse 《Israel Journal of Mathematics》2018,227(1):379-396
We prove that the group of diffeomorphisms of the interval [0, 1] contains surface groups whose action on (0, 1) has no global fix point and such that only countably many points of the interval (0, 1) have non-trivial stabiliser. 相似文献
5.
6.
7.
8.
Mechanistic Aspects of a Highly Active Dinuclear Zinc Catalyst for the Co‐polymerization of Epoxides and CO2
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Stefan Kissling Peter T. Altenbuchner Dr. Maximilian W. Lehenmeier Dr. Eberhardt Herdtweck Dr. Peter Deglmann Dr. Uwe B. Seemann Prof. Dr. Bernhard Rieger 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(22):8148-8157
The dinuclear zinc complex reported by us is to date the most active zinc catalyst for the co‐polymerization of cyclohexene oxide (CHO) and carbon dioxide. However, co‐polymerization experiments with propylene oxide (PO) and CO2 revealed surprisingly low conversions. Within this work, we focused on clarification of this behavior through experimental results and quantum chemical studies. The combination of both results indicated the formation of an energetically highly stable intermediate in the presence of propylene oxide and carbon dioxide. A similar species in the case of cyclohexene oxide/CO2 co‐polymerization was not stable enough to deactivate the catalyst due to steric repulsion. 相似文献
9.
10.
S. V. Panin I. V. Vlasov V. P. Sergeev B. B. Ovechkin P. O. Marushchak Sunder Ramasubbu P. S. Lyubutin V. V. Titkov 《Physical Mesomechanics》2015,18(3):261-272
The structure and properties of 12Cr1MoV steel irradiated with a zirconium ion beam were studied by optical microscopy, scanning electron microscopy, and micro- and nanoindentation. It is shown that the modification covers the entire cross-section of the irradiated specimens to a depth of 1 mm. The data on irradiation-induced structural changes are used to interpret the changes in mechanical properties of the irradiated specimens under static and cyclic loading. Particular attention is given to analysis of strain estimation by the digital image correlation method. 相似文献