全文获取类型
收费全文 | 9312篇 |
免费 | 1348篇 |
国内免费 | 1034篇 |
专业分类
化学 | 6907篇 |
晶体学 | 105篇 |
力学 | 470篇 |
综合类 | 110篇 |
数学 | 1186篇 |
物理学 | 2916篇 |
出版年
2024年 | 13篇 |
2023年 | 165篇 |
2022年 | 242篇 |
2021年 | 289篇 |
2020年 | 344篇 |
2019年 | 329篇 |
2018年 | 258篇 |
2017年 | 276篇 |
2016年 | 446篇 |
2015年 | 404篇 |
2014年 | 556篇 |
2013年 | 710篇 |
2012年 | 850篇 |
2011年 | 860篇 |
2010年 | 606篇 |
2009年 | 538篇 |
2008年 | 607篇 |
2007年 | 522篇 |
2006年 | 450篇 |
2005年 | 373篇 |
2004年 | 355篇 |
2003年 | 320篇 |
2002年 | 345篇 |
2001年 | 270篇 |
2000年 | 170篇 |
1999年 | 211篇 |
1998年 | 137篇 |
1997年 | 108篇 |
1996年 | 129篇 |
1995年 | 97篇 |
1994年 | 99篇 |
1993年 | 89篇 |
1992年 | 76篇 |
1991年 | 77篇 |
1990年 | 46篇 |
1989年 | 53篇 |
1988年 | 32篇 |
1987年 | 31篇 |
1986年 | 33篇 |
1985年 | 31篇 |
1984年 | 11篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1980年 | 7篇 |
1963年 | 7篇 |
1959年 | 12篇 |
1958年 | 11篇 |
1957年 | 15篇 |
1956年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
Sonia Herranz Markéta Bocková María Dolores Marazuela Ji?í Homola María Cruz Moreno-Bondi 《Analytical and bioanalytical chemistry》2010,398(6):2625-2634
A surface plasmon resonance (SPR) biosensor for the detection of microcystins (MCs) in drinking water has been developed.
Several assay formats have been evaluated. The selected format is based on a competitive inhibition assay, in which microcystin-LR
(MCLR) has been covalently immobilized onto the surface of an SPR chip functionalized with a self-assembled monolayer. The
influence of several factors affecting sensor performance, such as the nature and concentration of the antibody, the composition
of the carrier buffer, and the blocking and regeneration solutions, has been evaluated. The optimized SPR biosensor provides
an IC50 0.67 ± 0.09 μg L−1, a detection limit of 73 ± 8 ng L−1, and a dynamic range from 0.2 to 2.0 μg L−1 for MCLR. Cross-reactivity to other related MCs, such as microcystin-RR (88%) and microcystin-YR (94%), has also been measured.
The SPR biosensor can perform four simultaneous determinations in 60 min, and each SPR chip can be reused for at least 40
assay–regeneration cycles without significant binding capacity loss. The biosensor has been successfully applied to the direct
analysis of MCLR in drinking water samples, below the provisional guideline value of 1 μg L−1 established by the World Health Organization for drinking water. 相似文献
942.
HUANG Yu LIU JunLiang ZHANG Ji LIU Qiang HOU JiTing ZHANG Yu ZHANG DaWei LU QiaoSen CHEN ShanYong LIN HongHui & YU XiaoQi Key Laboratory of Green Chemistry Technology Ministry of Education College of Chemistry Sichuan University Chengdu China Key Laboratory of Bio-resources Eco-environment College of Life Sciences China. 《中国科学:化学》2010,(1)
A series of novel molecules with a cyclen(1,4,7,10-tetraazacyclododecane) moiety appended on and bearing different aromatic fragments in the structures were synthesized and characterized.The binding activities of these compounds towards DNA were systematically studied by spectroscopic,viscometric and gel electrophoresis methods.The results suggest that the stacking interaction plays an important role in improving the DNA binding ability of the compounds.The binding modes of the compounds towards DNA are als... 相似文献
943.
Yue Zhu Min Pu De-Cai Fang Yong-Qiang Ji Jing He David G. Evans 《Structural chemistry》2010,21(4):817-825
Abstract
The cis–trans isomerization pathways of 3,3′-azobenzene disulphonate in the S0 and T1 states are studied by DFT method at the B3LYP/6-31G(d,p) level. In the S0 state, the cis–trans isomerization concerns the complex pathway that is characterized by the inversion of one NNC angle combined with rotation around the NC bond, and the three sequential transition states are also found on the potential energy profile. Therefore, the cis–trans isomerization of 3,3′-azobenzene disulphonate can be understood in terms of a pathway involving successive rotation, inversion, and rotation processes. The energy barrier of the S0 state is 22.79 kcal mol−1. In the T1 state, the isomerization mainly concerns the rotational pathway around the NN double bond, and the two isomers are connected through only one transition state. The isomerization of the T1 state is related to a lower energy barrier, 5.02 kcal mol−1, but requires a change in spin-multiplicity. 相似文献944.
Jo E Jhon YH Choi SB Shim JG Kim JH Lee JH Lee IY Jang KR Kim J 《Chemical communications (Cambridge, England)》2010,46(48):9158-9160
A crystal structure of a carbamate of 2-amino-2-methyl-1-propanol (AMP-carbamate) has been elucidated and its structural and electronic properties investigated by density functional theory calculations and natural bond orbital analyses. 相似文献
945.
Asporyergosterol (1), a new steroid with an E double bond between C-17 and C-20, was identified from the culture extracts of Aspergillus oryzae, an endophytic fungus isolated from the marine red alga Heterosiphonia japonica. Moreover, four known steroids including (22E,24R)-ergosta-4,6,8(14),22-tetraen-3-one (2), (22E,24R)-3beta-hydroxyergosta-5,8,22-trien-7-one (3), (22E,24R)-ergosta-7,22-dien-3beta,5alpha,6beta-triol (4), and (22E,24R)-5alpha,8alpha-epidioxyergosta-6,22-dien-3beta-ol (5) were isolated. Structures of these compounds were unambiguously established by spectroscopic techniques and by comparison with literature values. All the isolates exhibited low activity to modulate acetylcholinesterase (AChE). 相似文献
946.
Polyurea-entrapped palladium nanoclusters have been prepared by interfacial polymerization in W/O emulsion and showed high thermal stability and chemical stability with the content of 0.12 mmol g?1 Pd. This catalyst exhibited dual catalytic activity for reduction of nitro compounds and hydrodehalogenation of aromatic chlorides in atmospheric hydrogen with 100% yield for reduction of nitro compounds and >99% yield for hydrodehalogenation of aromatic chlorides. This immobilizing method was particularly effective and eliminated the need of special chelating groups. 相似文献
947.
948.
Alexander Popkov Jiří Hanusek Jiří Čermák Vratislav Langer Robert Jirásko Michal Holčapek Milan Nádvorník 《Journal of Radioanalytical and Nuclear Chemistry》2010,285(3):621-626
In this communication the evaluation of eleven new metallocomplex alanine synthons bearing C2-symmetric benzyl groups with electron-donating and electron-withdrawing substituents is described. α-Methylated glycine synthons (alanine complexes) were evaluated alongside alanine synthons in order to obtain a deeper understanding of the relationship between their structures and stereochemistry of monoalkylated products and to choose several candidates for their further tests for stereospecific preparation of 6-[18F]FDOPA. Glycine-derived analogues of the complexes 3–5 are the best candidates for the development of a 6-[18F]FDOPA preparation procedure. In the model epimerisation reaction they demonstrated the best performance, much better compared to the previously described compound 2. Complexes 3, 5 and 8 are the best in asymmetric preparation of β-13C monolabelled α-aminoisobutyric acid. They have to be tested in the preparation of α-methyl amino acids like 6-[18F]-α-methylDOPA and 2-[18F]-α-methyltyrosine. 相似文献
949.
Michal Ilčin Oľga Holá Barbora Bakajová Jiří Kučerík 《Journal of Radioanalytical and Nuclear Chemistry》2010,283(1):9-13
Samples of pure polyvinyl alcohol (PVA) and PVA doped with humic acids were exposed to gamma radiation. Gamma rays induced
the degradation of the pure polymer. Degradation changes were observed using ATR FT-IR equipment. Dehydration, double bond
creation, and their subsequent oxidation (surrounding atmosphere was air) were found out. Also, other degradation reactions
(e.g. chain scission, cyclization) occur simultaneously. Formation of C=C and C=O bonds is apparent from FT-IR spectra. In
contrast the presence of humic acids in the PVA sample showed stabilizing effect on PVA structure within the concentration
range 0.5–10%. 相似文献
950.