全文获取类型
收费全文 | 104343篇 |
免费 | 28163篇 |
国内免费 | 26734篇 |
专业分类
化学 | 68560篇 |
晶体学 | 2243篇 |
力学 | 6976篇 |
综合类 | 1322篇 |
数学 | 13693篇 |
物理学 | 66446篇 |
出版年
2024年 | 493篇 |
2023年 | 978篇 |
2022年 | 1741篇 |
2021年 | 1651篇 |
2020年 | 1935篇 |
2019年 | 2426篇 |
2018年 | 2280篇 |
2017年 | 3374篇 |
2016年 | 3236篇 |
2015年 | 3806篇 |
2014年 | 4020篇 |
2013年 | 6005篇 |
2012年 | 6582篇 |
2011年 | 8440篇 |
2010年 | 11724篇 |
2009年 | 12120篇 |
2008年 | 6299篇 |
2007年 | 5322篇 |
2006年 | 5056篇 |
2005年 | 5057篇 |
2004年 | 5343篇 |
2003年 | 4248篇 |
2002年 | 4031篇 |
2001年 | 4347篇 |
2000年 | 3659篇 |
1999年 | 3251篇 |
1998年 | 2521篇 |
1997年 | 2221篇 |
1996年 | 2533篇 |
1995年 | 2985篇 |
1994年 | 3048篇 |
1993年 | 3071篇 |
1992年 | 2664篇 |
1991年 | 2206篇 |
1990年 | 1901篇 |
1989年 | 1961篇 |
1988年 | 1961篇 |
1987年 | 1235篇 |
1986年 | 1281篇 |
1985年 | 889篇 |
1984年 | 1020篇 |
1982年 | 913篇 |
1981年 | 758篇 |
1980年 | 775篇 |
1979年 | 566篇 |
1978年 | 535篇 |
1977年 | 634篇 |
1976年 | 1043篇 |
1972年 | 533篇 |
1971年 | 441篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Applied Mathematics and Mechanics - Spiral springs have a wide range of applications in various fields. As a result of the complexity of friction, few theoretical analyses of spring belts under... 相似文献
2.
Mathematical Programming - In the general equilibrium with incomplete asset markets (GEI) model, the excess demand functions are typically not continuous at the prices for which the assets have... 相似文献
4.
For an integer , a graph is -hamiltonian if for any vertex subset with , is hamiltonian, and is -hamiltonian connected if for any vertex subset with , is hamiltonian connected. Thomassen in 1984 conjectured that every 4-connected line graph is hamiltonian (see Thomassen, 1986), and Ku?zel and Xiong in 2004 conjectured that every 4-connected line graph is hamiltonian connected (see Ryjá?ek and Vrána, 2011). In Broersma and Veldman (1987), Broersma and Veldman raised the characterization problem of -hamiltonian line graphs. In Lai and Shao (2013), it is conjectured that for , a line graph is -hamiltonian if and only if is -connected. In this paper we prove the following.(i) For an integer , the line graph of a claw-free graph is -hamiltonian if and only if is -connected.(ii) The line graph of a claw-free graph is 1-hamiltonian connected if and only if is 4-connected. 相似文献
5.
利用n维有限射影空间上的一些性质,构作了组合群验的数学模型de-析取矩阵,并研究了它的参数和Hamming距离. 相似文献
6.
Zhen Xi 《中国科学:化学(英文版)》2015,(3):434-435
Redox-based post-translational modification of protein thiols has become an attractive strategy in cellular homeostasis and cell signaling.Due to the reductive end of the redox buffer network,the vicinal dithiol-containing proteins(VDPs)maintains an appropriate oxidation-reduction state of proteins through the reversible transformation from vicinal dithiols to disulfide,which is responsible for a variety of 相似文献
7.
8.
量子自旋液体是最近几年刚被人们证实除铁磁体、反铁磁体之外的第三种磁性类型,因其有望解释高温超导的运行机制、改变计算机硬盘信息存储方式而在物理、材料等领域备受关注。自旋阻挫作为量子自旋液体的最小单元可能是解开量子自旋液体诸多问题的钥匙,所以在磁学、电学研究领域再一次成为人们研究的热点。基于文献报道的三核铜配合物[Cu3(μ3-OH)(μ-OPz)3(NO3)2(H2O)2]·CH3OH(1),我们合成了三维金属有机框架配合物{[Ag(HOPz)Cu3(μ3-OH)(NO3)3(OPz)2Ag(NO3)]·6H2O}n(2)(HOPz=甲基(2-吡嗪基)酮肟),并从自旋阻挫的角度对二者磁性质进行对比和详细分析。磁化率数据表明自旋间有很强的反铁磁相互作用和反对称交换。通过包含各向同性和反对称交换的哈密顿算符对两者磁学数据进行拟合并研究其磁构关系,所获最佳拟合参数为:配合物1:Jav=-426 cm^-1,g⊥=1.83,g∥=2.00;配合物2:Jav=-401 cm^-1,g⊥=1.85,g∥=2.00。 相似文献
9.
We present the fabrication of core-shell-satellite Au@SiO2-Pt nanostructures and demonstrate that LSPR excitation of the core Au nanoparticle can induce plasmon coupling effect to initiate photocatalytic hydrogen generation from decomposition of formic acid. Further studies suggest that the plasmon coupling effect induces a strong local electric field between the Au core and Pt nanoparticles on the SiO2 shell, which enables creation of hot electrons on the non-plasmonic-active Pt nanoparticles to participate hydrogen evolution reaction on the Pt surface. In addition, small SiO2 shell thickness is required in order to obtain a strong plamon coupling effect and achieve efficient photocatalytic activities for hydrogen generation. 相似文献
10.
Hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) have been deemed as clean and sustainable strategies to solve the energy crisis and environmental problems. Various catalysts have been developed to promote the process of HER and OER. Among them, two-dimensional covalent organic frameworks (2D COFs) have received great attention due to their diverse and designable structure. In this minireview, we mainly summarize the diverse linkages of 2D COFs and strategies for enhancing the catalytic performance of 2D COFs for HER and OER, such as introducing active building blocks, metal ions and tailored linkages. Furthermore, a brief outlook for the development directions of COFs in the field of HER and OER is provided, expecting to stimulate new opportunities in future research. 相似文献