全文获取类型
收费全文 | 81565篇 |
免费 | 460篇 |
国内免费 | 385篇 |
专业分类
化学 | 26414篇 |
晶体学 | 923篇 |
力学 | 6828篇 |
数学 | 32246篇 |
物理学 | 15999篇 |
出版年
2022年 | 76篇 |
2021年 | 79篇 |
2020年 | 73篇 |
2019年 | 83篇 |
2018年 | 10480篇 |
2017年 | 10311篇 |
2016年 | 6159篇 |
2015年 | 941篇 |
2014年 | 406篇 |
2013年 | 671篇 |
2012年 | 3980篇 |
2011年 | 10681篇 |
2010年 | 5772篇 |
2009年 | 6183篇 |
2008年 | 6756篇 |
2007年 | 8875篇 |
2006年 | 323篇 |
2005年 | 1415篇 |
2004年 | 1624篇 |
2003年 | 2037篇 |
2002年 | 1104篇 |
2001年 | 298篇 |
2000年 | 331篇 |
1999年 | 194篇 |
1998年 | 212篇 |
1997年 | 178篇 |
1996年 | 242篇 |
1995年 | 161篇 |
1994年 | 106篇 |
1993年 | 140篇 |
1992年 | 89篇 |
1991年 | 105篇 |
1990年 | 88篇 |
1989年 | 109篇 |
1988年 | 98篇 |
1987年 | 88篇 |
1986年 | 94篇 |
1985年 | 87篇 |
1984年 | 90篇 |
1983年 | 77篇 |
1982年 | 74篇 |
1981年 | 79篇 |
1980年 | 87篇 |
1979年 | 86篇 |
1978年 | 64篇 |
1977年 | 68篇 |
1975年 | 44篇 |
1973年 | 46篇 |
1914年 | 45篇 |
1909年 | 41篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Russian Journal of Organic Chemistry - A highly efficient green protocol has been proposed for the synthesis of symmetrical S-aryl arenesulfonothioates by irradiation of N-hydroxy arenesulfonamides... 相似文献
2.
Journal of Applied Spectroscopy - The elemental composition of one- and two-rupee coins issued in different years by the Reserve Bank of India (RBI) was investigated using laser-induced breakdown... 相似文献
3.
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
4.
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
5.
6.
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
7.
8.
9.
Self‐Assembly and Gelation of Poly(aryl ether) Dendrons Containing Hydrazide Units: Factors Controlling the Formation of Helical Structures 下载免费PDF全文
Partha Malakar Prof. Dr. Edamana Prasad 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(13):5093-5100
Self‐assembly of AB2 and AB3 type low molecular weight poly(aryl ether) dendrons that contain hydrazide units were used to investigate mechanistic aspects of helical structure formation during self‐assembly. The results suggest that there are three important aspects that control helical structure formation in such systems with acyl hydrazide/hydrazone linkage: i) J‐type aggregation, ii) the hydrogen‐bond donor/acceptor ability of the solvent, and iii) the dielectric constant of the solvent. The monomer units self‐assemble to form dimer structures through hydrogen‐bonding and further assembly of the hydrogen‐bonded dimers leads to macroscopic chirality in the present case. Dimer formation was confirmed by NMR spectroscopy and by mass spectrometry. The self‐assembly in the system was driven by hydrogen‐bonding and π–π stacking interactions. The morphology of the aggregates formed was examined by scanning electron microscopy, and the analysis suggests that aprotic solvent systems facilitate helical fibre formation, whereas introduction of protic solvents results in the formation of flat ribbons. This detailed mechanistic study suggests that the self‐assembly follows a nucleation–elongation model to form helical structures, rather than the isodesmic model. 相似文献
10.