全文获取类型
收费全文 | 38049篇 |
免费 | 6611篇 |
国内免费 | 4327篇 |
专业分类
化学 | 26110篇 |
晶体学 | 519篇 |
力学 | 2472篇 |
综合类 | 285篇 |
数学 | 4428篇 |
物理学 | 15173篇 |
出版年
2024年 | 143篇 |
2023年 | 777篇 |
2022年 | 1285篇 |
2021年 | 1327篇 |
2020年 | 1485篇 |
2019年 | 1414篇 |
2018年 | 1255篇 |
2017年 | 1174篇 |
2016年 | 1773篇 |
2015年 | 1760篇 |
2014年 | 2137篇 |
2013年 | 2693篇 |
2012年 | 3263篇 |
2011年 | 3397篇 |
2010年 | 2323篇 |
2009年 | 2289篇 |
2008年 | 2485篇 |
2007年 | 2235篇 |
2006年 | 2137篇 |
2005年 | 1650篇 |
2004年 | 1328篇 |
2003年 | 1120篇 |
2002年 | 1038篇 |
2001年 | 832篇 |
2000年 | 870篇 |
1999年 | 823篇 |
1998年 | 733篇 |
1997年 | 684篇 |
1996年 | 691篇 |
1995年 | 616篇 |
1994年 | 540篇 |
1993年 | 430篇 |
1992年 | 425篇 |
1991年 | 329篇 |
1990年 | 302篇 |
1989年 | 239篇 |
1988年 | 204篇 |
1987年 | 172篇 |
1986年 | 153篇 |
1985年 | 152篇 |
1984年 | 104篇 |
1983年 | 71篇 |
1982年 | 60篇 |
1981年 | 36篇 |
1980年 | 16篇 |
1979年 | 10篇 |
1977年 | 2篇 |
1971年 | 1篇 |
1959年 | 1篇 |
1957年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
Chunxiang Wang Yanhui Liu Yangtao Fan Yijun Liu Qiancheng Li Houqiang Xu 《Journal of Experimental and Theoretical Physics》2016,122(6):1117-1121
In cell environments crowded with macromolecules, the depletion effects act and assist in the assembly of a wide range of cellular structures, from the cytoskeleton to the chromatin loop, which are well accepted. But a recent quantum dot experiment indicated that the dimensions of the receptor–ligand complex have strong effects on the size-dependent exclusion of proteins in cell environments. In this article, a continuum elastic model is constructed to resolve the competition between the dimension of the receptor–ligand complex and depletion effects in the endocytosis of a spherical virus-like bioparticle. Our results show that the depletion effects do not always assist endocytosis of a spherical virus-like bioparticle; while the dimension of the ligand–receptor complex is larger than the size of a small bioparticle in cell environments, the depletion effects do not work and reverse effects appear. The ligand density covered on the virus can be identified quantitatively. 相似文献
993.
994.
A comprehensive study on Raman spectroscopy with different excitation wavelengths, sample sizes, and sample shapes for optic phonons (OPs) and acoustic phonons (APs) in polar and non-polar nano-semiconductors has been performed. The study affirms that the finite size effect does not appear in the OPs of polar nano-semiconductors, while it exists in all other types of phonons. The absence of the FSE is confirmed to originate from the long-range Fr¨ohlich interaction and the breaking of translation symmetry. The result indicates that the Raman spectra of OPs cannot be used as a method to characterize the scale and crystalline property of polar nano-semiconductors. 相似文献
995.
996.
997.
Binhang Yan Pengcheng Xu Xuan Li Cliff Yi Guo Yong Jin Yi Cheng 《Plasma Chemistry and Plasma Processing》2012,32(6):1203-1214
Liquid hydrocarbons including n-hexane, cyclohexane and toluene are pyrolyzed in H2/Ar plasma to investigate the effects of feedstock properties and key operating conditions (e.g., the feedstock specific input power and residence time) on the reaction performance. The experiments verify that the non-aromatic hydrocarbons show better chemical reactivity than partially aromatic substances. Meanwhile, the straight-chain alkanes and cycloalkanes have better yields of ethylene during the pyrolysis. The results also demonstrate that the pyrolysis reactions are almost completed within the first 0.8?ms in Ar/H2 plasma independent of the feed substances (i.e., liquid hydrocarbons), where the increased feedstock specific input power enhances the reactant conversions and correspondingly raises the yields of acetylene. At a feedstock specific input power of 4.7?×?104?kJ/kg, the n-hexane conversion is over 90?% and the yield of acetylene reaches 70?%. In addition, when using n-hexane as the feedstock, very little coke is formed during the course of reaction. Comprehensive comparisons of the current experiments with the data reported in the literature are made to point out the key influencing factors, i.e., the effective mass ratio of C/H (R C/H) in the gaseous phase and the quench temperature. Both two factors would need to be enhanced in order to get a better performance. Finally, the improvements on the specific energy requirement of this process are discussed. 相似文献
998.
Pd nanoparticles have been successfully supported on nanoscale metal-organic frameworks (NMOFs) by using a simple and effective microwave-assisted impregnation process. The resulting composite, representing as a highly active NMOFs supported metal nanoparticles catalyst for the Suzuki cross-coupling reaction between aryl/heteroaryl halides and arylboronic acids, is well characterized, and its high activity and good recyclability are discussed in details. It reveals that, compared to the corresponding bulk MOFs and conventional active carbon materials, nanoscale MOFs as novel support materials for heterogeneous catalysts can exhibit superior performance in the catalytic reactions. 相似文献
999.
1000.