全文获取类型
收费全文 | 3901篇 |
免费 | 718篇 |
国内免费 | 611篇 |
专业分类
化学 | 3296篇 |
晶体学 | 67篇 |
力学 | 192篇 |
综合类 | 75篇 |
数学 | 430篇 |
物理学 | 1170篇 |
出版年
2024年 | 25篇 |
2023年 | 89篇 |
2022年 | 148篇 |
2021年 | 187篇 |
2020年 | 213篇 |
2019年 | 210篇 |
2018年 | 190篇 |
2017年 | 173篇 |
2016年 | 227篇 |
2015年 | 252篇 |
2014年 | 292篇 |
2013年 | 345篇 |
2012年 | 365篇 |
2011年 | 361篇 |
2010年 | 309篇 |
2009年 | 282篇 |
2008年 | 260篇 |
2007年 | 233篇 |
2006年 | 186篇 |
2005年 | 145篇 |
2004年 | 97篇 |
2003年 | 89篇 |
2002年 | 92篇 |
2001年 | 71篇 |
2000年 | 53篇 |
1999年 | 49篇 |
1998年 | 24篇 |
1997年 | 18篇 |
1996年 | 13篇 |
1995年 | 24篇 |
1994年 | 15篇 |
1993年 | 20篇 |
1992年 | 16篇 |
1991年 | 7篇 |
1990年 | 20篇 |
1989年 | 11篇 |
1988年 | 9篇 |
1987年 | 9篇 |
1985年 | 8篇 |
1982年 | 5篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 7篇 |
1976年 | 4篇 |
1975年 | 9篇 |
1974年 | 8篇 |
1972年 | 12篇 |
1971年 | 6篇 |
1970年 | 5篇 |
1969年 | 5篇 |
排序方式: 共有5230条查询结果,搜索用时 46 毫秒
61.
Zhen‐Ting Du Guo‐Ren Yue An‐Pai Li Jun‐Ying Ma Tong‐Xing Wu Xue‐Gong She Xin‐Fu Pan 《中国化学会会志》2004,51(3):505-508
A facile total synthesis of (±)‐nimbiol 1 has been achieved. In order to decrease the dioxo byproduct 2a , an improved oxidation system of CrO3/H2O/HOAc/NaOAc was used. 相似文献
62.
Three novel supramolecular arrays of zigzag polyaromatic salts are reported. Both the conformation and disposition of the dications are subjected to various noncovalent interactions. Thus, the presence or absence of the π‐π interacting enclathrated molecules, the efficient packing and the involved hydrogen bonding interactions of anions, as well as the increased hydrophobic property of the dications themselves exert influence. 相似文献
63.
Shen R Lin CT Bowman EJ Bowman BJ Porco JA 《Journal of the American Chemical Society》2003,125(26):7889-7901
The total synthesis and stereochemical assignment of the potent antitumor macrolide lobatamide C, as well as synthesis of simplified lobatamide analogues, is reported. Cu(I)-mediated enamide formation methodology has been developed to prepare the highly unsaturated enamide side chain of the natural product and analogues. A key fragment coupling employs base-mediated esterification of a beta-hydroxy acid and a salicylate cyanomethyl ester. Three additional stereoisomers of lobatamide C have been prepared using related synthetic routes. The stereochemistry at C8, C11, and C15 of lobatamide C was assigned by comparison of stereoisomers and X-ray analysis of a crystalline derivative. Synthetic lobatamide C, stereoisomers, and simplified analogues have been evaluated for inhibition of bovine chromaffin granule membrane V-ATPase. The salicylate phenol, enamide NH, and ortho-substitution of the salicylate ester have been shown to be important for V-ATPase inhibitory activity. 相似文献
64.
65.
The enhanced lanthanide white-emission in solid by cucurbituril-based supramolecular assembly may provide a new strategy for smart light-emitting materials. 相似文献
66.
Jia Hui Xu Ting Ting Zhuang Yi Cao Dr. Jing Yang Jing Jia Wen Zheng Ying Wu Dr. Chun Fang Zhou Dr. Li Huang Ying Wang Prof. Dr. Ming Bo Yue Dr. Jian Hua Zhu Prof. Dr. 《化学:亚洲杂志》2007,2(8):996-1006
Copper oxide was incorporated into MCM‐41 by a one‐pot synthesis under acidic conditions to prepare a new mesoporous nitrosamines trap for protection of the environment. The resulting composites were characterized by XRD, N2 adsorption–desorption, and H2 temperature‐programmed reduction techniques, and their adsorption capabilities were assessed in the gaseous adsorption of N‐nitrosopyrrolidine (NPYR). The adsorption isotherms were consistent with the Freundlich equation. The copper salt was deposited onto MCM‐41 during the evaporation stage and was fixed on the host in the calcination process that followed. MCM‐41 was able to capture NPYR in air below 373 K but not at 453 K. Loading of copper oxide on MCM‐41 greatly improved its adsorption capability at elevated temperatures. The influence of the incorporation of copper into MCM‐41 samples and the adsorption behavior of these samples are discussed in detail. 相似文献
67.
Ting Zhang 《Analytica chimica acta》2003,489(2):199-206
A novel inorganic-organic hybrid titania sol-gel nanocomposite film was prepared to fabricate a sensitive tyrosinase biosensor for the amperometric detection of trace phenolic compounds without additional electron mediators. Acetylacetone worked as a complexing ligand to chelate with Ti atom in the synthesis process, and the pH of the titania solution could be adjusted to the value which was optimum for retaining tyrosinase activity and such a membrane was stably attached on to the surface of a glassy carbon electrode (GCE). This titania matrix could supply a good environment for enzyme loading, which resulted in a high sensitivity of 15.78 μA μM−1 cm−2 for monitoring phenols with a detection limit of 1×10−8 M at a signal-to-noise ratio of 3. The TiO2 sol-gel derived biosensor exhibited a fast response less than 10 s and a good stability for more than 2 months. 相似文献
68.
Kedong Xia Junpo Guo Cuijuan Xuan Ting Huang Zhiping Deng Lingxuan Chen Deli Wang 《中国化学快报》2019,30(1):192-196
Nitrogen doped carbon nanosheets supported molybdenum carbides nanoparticles (MoxC/NCS) have been synthesized by tuning the mass ratio of melamine and ammonia molybdate. The Mo2C/NCS-10 exhibits superior electrocatalytic performance and stability for HER, which was attributed to N-doped carbon nanosheets, small particle size, mesoporous structure, and large electrochemical active surface area. 相似文献
69.
A modified method has been developed to purify retine from pig liver. The crude extract of retine can be separated into five fractions by paper chromatography, each of them having been tested for the effect on the proliferation of protozoal Tetrahymena Pyriformis. One of the fractions, G3, has the strongest effect. The present results show that G3 fraction showed positive reactions toward 2,4-dinitro-phenyl hydrazine, ethylene diamine, and ninhydrin. Other properties of the fraction has also been studied. 相似文献
70.
In this study, poly(N-methylolacrylamide)/polymethylacrylamide (PNMA/PMAA) hybrids were produced successfully by frontal free-radical polymerization
at ambient pressure. In a typical run, the appropriate amounts of reactants (N-methylolacrylamide, NMA; methylacrylamide, MAA) and initiator (ammonium persulfate) were dissolved in dimethyl sulfoxide
at ambient temperature. Frontal polymerization (FP) was initiated by heating the wall of the tube with a soldering iron, and
the resultant hot fronts were allowed to self-propagate throughout the reaction vessel. Once initiated, no further energy
was required for polymerization to occur. The dependences of the front velocity and front temperature on the initiator concentration,
reactant dilution, and NMA/MAA components were thoroughly investigated. The front temperatures were between 69 and 116 °C,
depending on the persulfate concentration. We have also investigated the FP of PNMA/PMAA hybrids with N-methyl-2-pyrrolidone as solvent. Results show that FP can be exploited as a means for the preparation of PNMA/PMAA hybrids
with the potential advantage of higher throughput compared to the traditional mode. 相似文献