全文获取类型
收费全文 | 3104篇 |
免费 | 213篇 |
国内免费 | 193篇 |
专业分类
化学 | 1997篇 |
晶体学 | 51篇 |
力学 | 111篇 |
综合类 | 1篇 |
数学 | 639篇 |
物理学 | 711篇 |
出版年
2024年 | 7篇 |
2023年 | 39篇 |
2022年 | 65篇 |
2021年 | 87篇 |
2020年 | 102篇 |
2019年 | 105篇 |
2018年 | 129篇 |
2017年 | 155篇 |
2016年 | 152篇 |
2015年 | 134篇 |
2014年 | 193篇 |
2013年 | 415篇 |
2012年 | 227篇 |
2011年 | 232篇 |
2010年 | 195篇 |
2009年 | 146篇 |
2008年 | 187篇 |
2007年 | 167篇 |
2006年 | 117篇 |
2005年 | 83篇 |
2004年 | 76篇 |
2003年 | 53篇 |
2002年 | 69篇 |
2001年 | 35篇 |
2000年 | 33篇 |
1999年 | 22篇 |
1998年 | 19篇 |
1997年 | 14篇 |
1996年 | 15篇 |
1995年 | 12篇 |
1994年 | 9篇 |
1993年 | 8篇 |
1992年 | 8篇 |
1990年 | 7篇 |
1989年 | 10篇 |
1988年 | 7篇 |
1987年 | 9篇 |
1986年 | 11篇 |
1985年 | 19篇 |
1984年 | 11篇 |
1983年 | 12篇 |
1982年 | 14篇 |
1981年 | 16篇 |
1980年 | 7篇 |
1979年 | 9篇 |
1977年 | 7篇 |
1976年 | 11篇 |
1974年 | 9篇 |
1973年 | 9篇 |
1968年 | 9篇 |
排序方式: 共有3510条查询结果,搜索用时 15 毫秒
101.
Journal of Inclusion Phenomena and Macrocyclic Chemistry - Newly phthalocyanine derivative which carries 2,6-dimethoxyphenoxy bioactive groups as tetrakis from non-peripheral positions of the... 相似文献
102.
103.
For a scalar evolution equation ut = K(t, x, u, ux, . . . , u2m+1) with m ≥ 1, the cohomology space H1,2() is shown to be isomorphic to the space of variational operators and an explicit isomorphism is given. The space of symplectic operators for ut = K for which the equation is Hamiltonian is also shown to be isomorphic to the space H1,2() and subsequently can be naturally identified with the space of variational operators. Third order scalar evolution equations admitting a first order symplectic (or variational) operator are characterized. The variational operator (or symplectic) nature of the potential form of a bi-Hamiltonian evolution equation is also presented in order to generate examples of interest. 相似文献
104.
Annals of Operations Research - We develop search algorithms based on local search, and a matheuristic that solves a set of mixed integer programming models to improve the robustness of a set of... 相似文献
105.
Structural Chemistry - Metal carbonyl complexes, which have been known as effective catalysts since early days, find use in many fields both directly and indirectly. Although the use of metal... 相似文献
106.
In this paper, we study the difference spaces \({\mathcal {F}}(\varDelta )\), \({\mathcal {F}}_0(\varDelta )\), \({\mathcal {[F]}}(\varDelta )\) and \({\mathcal {[F]}}_0(\varDelta )\) of double sequences obtained as the domain of four-dimensional backward difference matrix \(\varDelta \) in the spaces \({\mathcal {F}}\), \({\mathcal {F}}_{0}\), \({\mathcal {[F]}}\) and \({\mathcal {[F]}}_{0}\) of almost convergent, almost null, strongly almost convergent and strongly almost null double sequences; respectively. We examine general topological properties of those spaces and give some inclusion theorems. Furthermore, we deal with their dual spaces.
相似文献107.
Fırıncı Rukiye Fırıncı Erkan Başbülbül Gamze Dabanca Mustafa Berk Barut Celepci Duygu Günay M. Emin 《Transition Metal Chemistry》2019,44(4):391-397
Transition Metal Chemistry - Three 1,3-dimethylbarbiturate-enamine derivatives and their symmetrical palladium(II) complexes were prepared and characterized by spectroscopic methods. In addition,... 相似文献
108.
109.
110.
A series of piperidoimidazolinium salts which differ in the chain lengths (butyl, octyl, dodecyl, octadecyl) and their Pd–N‐heterocyclic carbene complexes with pyridine were synthesized and characterized using elemental analysis and spectroscopic methods. The effects of these ligands on catalyst activation and the performance of the complexes were studied in Suzuki–Miyaura reactions of arylboronic acid with aryl chlorides. The complex with the ligand having the longest chain length was found to be most active. The results demonstrated that the length of the alkyl chain of the piperidoimidazolin‐2‐ylidene controlled the dispersion and composition of the nanoparticles and it affected the catalytic activity. The impact of alkyl chain length of piperidoimidazolin‐2‐ylidene on the Suzuki–Miyaura reactions of arylboronic acid with aryl halides was systematically investigated. 相似文献