全文获取类型
收费全文 | 6214篇 |
免费 | 1118篇 |
国内免费 | 1091篇 |
专业分类
化学 | 5332篇 |
晶体学 | 60篇 |
力学 | 262篇 |
综合类 | 81篇 |
数学 | 770篇 |
物理学 | 1918篇 |
出版年
2024年 | 19篇 |
2023年 | 102篇 |
2022年 | 119篇 |
2021年 | 148篇 |
2020年 | 231篇 |
2019年 | 271篇 |
2018年 | 227篇 |
2017年 | 172篇 |
2016年 | 283篇 |
2015年 | 318篇 |
2014年 | 351篇 |
2013年 | 477篇 |
2012年 | 529篇 |
2011年 | 506篇 |
2010年 | 421篇 |
2009年 | 417篇 |
2008年 | 439篇 |
2007年 | 401篇 |
2006年 | 376篇 |
2005年 | 335篇 |
2004年 | 319篇 |
2003年 | 300篇 |
2002年 | 354篇 |
2001年 | 227篇 |
2000年 | 191篇 |
1999年 | 193篇 |
1998年 | 124篇 |
1997年 | 103篇 |
1996年 | 72篇 |
1995年 | 59篇 |
1994年 | 59篇 |
1993年 | 33篇 |
1992年 | 37篇 |
1991年 | 43篇 |
1990年 | 30篇 |
1989年 | 22篇 |
1988年 | 17篇 |
1987年 | 11篇 |
1986年 | 18篇 |
1985年 | 20篇 |
1984年 | 9篇 |
1983年 | 8篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1979年 | 4篇 |
1977年 | 2篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1968年 | 3篇 |
1936年 | 2篇 |
排序方式: 共有8423条查询结果,搜索用时 234 毫秒
901.
Lin S Shi T Chen KY Zhang ZX Shan L Shen YH Zhang WD 《Chemical communications (Cambridge, England)》2011,47(37):10413-10415
Cyclopenicillone (1), possessing a unique 2,5-dimethylcyclopent-2-enone carbon skeleton, has been isolated from the cultures broth of the fungus Penicillium decumbens. The structure and absolute configuration of 1 were elucidated using a combination of NMR spectroscopy, CD data and computational approaches. Cyclopenicillone (1) demonstrated a dose-dependent (10-100 μM) inhibition against LPS-induced NO production in RAW264.7 macrophages. 相似文献
902.
Huang YX Liu XW Xie JF Sheng GP Wang GY Zhang YY Xu AW Yu HQ 《Chemical communications (Cambridge, England)》2011,47(20):5795-5797
Bridging microbes and electrode to facilitate the extracellular electron transfer (EET) is crucial for bio-electrochemical systems (BESs). Here, a significant enhancement of the EET process was achieved by biomimetically fabricating a network structure of graphene oxide nanoribbons (GONRs) on the electrode. This strategy is universal to enhance the adaptability of GONRs at the bio-nano interface to develop new bioelectronic devices. 相似文献
903.
Tandem mass spectrometry (MS/MS) of intact, noncovalently-bound protein-ligand complexes can yield structural information on the site of ligand binding. Fourier transform ion cyclotron resonance (FT-ICR) top-down MS of the 29 kDa carbonic anhydrase-zinc complex and adenylate kinase bound to adenosine triphosphate (ATP) with collisionally activated dissociation (CAD) and/or electron capture dissociation (ECD) generates product ions that retain the ligand and their identities are consistent with the solution phase structure. Increasing gas phase protein charging from electrospray ionization (ESI) by the addition of supercharging reagents, such as m-nitrobenzyl alcohol and sulfolane, to the protein analyte solution improves the capability of MS/MS to generate holo-product ions. Top-down proteomics for protein sequencing can be enhanced by increasing analyte charging. 相似文献
904.
A series of quinoxaline 1,4-di-N-oxide analogues were prepared from benzofurazan N-oxide derivatives and β-diketone ester compounds by the improved Beirut reaction. The structures of the target products were characterized by NMR, MS, IR and elemental analysis measurements, and that of 2-carbomethoxy-3-hydroxyquinoxaline- di-N-oxide was further confirmed by single-crystal X-ray diffraction. Its crystal structure belongs to the monoclinic system, space group C2/c with a = 14.4320 (12) ?, b = 10.7514 (9) ?, c = 13.2728 (11) ?, V = 1958.5 (3) ? 3, Z = 8. The X-ray crystallographic analysis reveals that quinoxaline 1,4-di-N-oxide displays acyloin-endiol tautomerism. 相似文献
905.
906.
907.
Liu C Pan J Li S Zhao Y Wu LY Berkman CE Whorton AR Xian M 《Angewandte Chemie (International ed. in English)》2011,50(44):10327-10329
908.
Charge separation in excited states upon visible light absorption is a central process in photovoltaic solar cell applications. Employing state-of-the-art first principles calculations based on time-dependent density functional theory (TDDFT), we simulate electron-hole dynamics in real time and illustrate the microscopic mechanism of charge separation at the interface between organic dye molecules and oxide semiconductor surfaces in dye-sensitized solar cells. We found that electron-hole separation proceeds non-adiabatically on an ultrafast timescale <100 fs at an anthocyanin/TiO(2) interface, and it is strongly mediated by the vibrations of interface Ti-O bonds, which anchor the dye onto the TiO(2) surface. The obtained absorption spectrum and electron injection timescale agree with experimental measurements. 相似文献
909.
Mesoporous carbon catalyst supports are attractive due to their wide chemical stability while potentially increasing mass-transport through and providing a path for larger molecules to access catalytic sites. Herein we report the synthesis of a phosphorylated mesoporous carbon solid-acid catalyst characterized by NH(3)-TPD and isopropanol dehydration. 相似文献
910.
Optical waveguides synthesized at the micro/nanoscale have drawn great interest for their potential applications in high speed miniaturized photonic integrations. In this Perspective article, we mainly focus on the related works on active optical waveguides based on functional small organic molecules in micro/nano regime. We begin with a general overview of recent progress in sub-wavelength optical waveguides, including the development of waveguide materials of inorganic semiconductors, polymers, and small organic molecules. Then brief highlights are put on the recently reported organic optical waveguides with various unique optical properties induced by the ordered molecular aggregations in the micro/nano-sized solid-state structures, such as polarized emission, lasing, aggregation-induced enhanced emission, etc. This article concludes with a summary and our personal view about the direction of future development in organic opto-functional waveguides as photonic devices. 相似文献