全文获取类型
收费全文 | 34416篇 |
免费 | 5445篇 |
国内免费 | 5144篇 |
专业分类
化学 | 25960篇 |
晶体学 | 477篇 |
力学 | 1977篇 |
综合类 | 421篇 |
数学 | 3753篇 |
物理学 | 12417篇 |
出版年
2024年 | 43篇 |
2023年 | 508篇 |
2022年 | 702篇 |
2021年 | 961篇 |
2020年 | 1187篇 |
2019年 | 1152篇 |
2018年 | 988篇 |
2017年 | 894篇 |
2016年 | 1467篇 |
2015年 | 1504篇 |
2014年 | 1846篇 |
2013年 | 2431篇 |
2012年 | 3004篇 |
2011年 | 3090篇 |
2010年 | 2211篇 |
2009年 | 2121篇 |
2008年 | 2517篇 |
2007年 | 2265篇 |
2006年 | 2187篇 |
2005年 | 1804篇 |
2004年 | 1554篇 |
2003年 | 1369篇 |
2002年 | 1457篇 |
2001年 | 1178篇 |
2000年 | 939篇 |
1999年 | 874篇 |
1998年 | 580篇 |
1997年 | 573篇 |
1996年 | 565篇 |
1995年 | 489篇 |
1994年 | 449篇 |
1993年 | 366篇 |
1992年 | 345篇 |
1991年 | 263篇 |
1990年 | 236篇 |
1989年 | 198篇 |
1988年 | 156篇 |
1987年 | 118篇 |
1986年 | 98篇 |
1985年 | 79篇 |
1984年 | 57篇 |
1983年 | 41篇 |
1982年 | 25篇 |
1981年 | 32篇 |
1980年 | 16篇 |
1978年 | 11篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1973年 | 7篇 |
1957年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
951.
Yang G Miao R Jin C Mei Y Tang H Hong J Guo Z Zhu L 《Journal of mass spectrometry : JMS》2005,40(8):1005-1016
Interaction of carboplatin with cytochrome c (Cyt. c) has been investigated by electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (MS/MS). ESI-MS studies revealed that the ring-opened adducts of carboplatin with Cyt. c were formed in the stoichiometric ratio of 1:1 and 2:1 at pH 5.0 and 37 degrees C and in the stoichiometric ratio of 1:1 only at pH 7.0 and 37 degrees C. It was also found that Cyt. c could be cleaved by carboplatin at pH 2.5 and 50 degrees C. The cleaved fragments of Cyt. c were determined by ESI-MS and MS/MS analysis to be Glu66 approximately Met80, Ac-Gly01 approximately Met65, Glu66 approximately Glu104, Ac-Gly01 approximately Met80 and Ile81 approximately Glu104. The carboplatin prefers to anchor to Met65 first, then to Met80. To further confirm the binding site of Met, AcMet-Gly was used as the model molecule to investigate its interaction with carboplatin and its hydrolysis reaction. On the basis of species detected during the reaction monitored by ESI-MS, a possible pathway of the cleavage reaction was proposed. 相似文献
952.
953.
Liang Hong Chen Zhen-Feng Hu Rui-Xiang Yu Qing Zhou Zhong-Yuan Zhou Xiang-Ge 《Transition Metal Chemistry》2002,27(1):102-104
(n-Bu4N)4[Mo8O26] reacts with the Na salt of 2-mercaptopyridine N-oxide (NaPT) in MeCN to give the complex (n-Bu4N)2[MoO2(PT)2·Mo4O8(-O)2(3-O)2(PT)2] (1) which contains two metal centres: one being mononuclear molybdenum chelating to two PT ligands, and the other a tetranuclear oxomolybdenum cluster with two PT ligands at the terminal point. The i.r. spectrum of the title complex exhibits absorption bands at 911.5 and 881.9 cm–1, characteristic of the [cis-MoO2]2+ fragment. 相似文献
954.
955.
Zhao Y Kan ZY Zeng ZX Hao YH Chen H Tan Z 《Journal of the American Chemical Society》2004,126(41):13255-13264
Nucleic acid molecules may fold into secondary structures, and the formation of such structures is involved in many biological processes and technical applications. The folding and unfolding rate constants define the kinetics of conformation interconversion and the stability of these structures and is important in realizing their functions. We developed a method to determine these kinetic parameters using an optical biosensor based on surface plasmon resonance. The folding and unfolding of a nucleic acid is coupled with a hybridization reaction by immobilization of the target nucleic acid on a sensor chip surface and injection of a complementary probe nucleic acid over the sensor chip surface. By monitoring the time course of duplex formation, both the folding and unfolding rate constants for the target nucleic acid and the association and dissociation rate constants for the target-probe duplex can all be derived from the same measurement. We applied this method to determine the folding and unfolding rate constants of the G-quadruplex of human telomere sequence (TTAGGG)(4) and its association and dissociation rate constants with the complementary strand (CCCTAA)(4). The results show that both the folding and unfolding occur on the time scale of minutes at physiological concentration of K(+). We speculate that this property might be important for telomere elongation. A complete set of the kinetic parameters for both of the structures allows us to study the competition between the formation of the quadruplex and the duplex. Calculations indicate that the formation of both the quadruplex and the duplex is strand concentration-dependent, and the quadruplex can be efficiently formed at low strand concentration. This property may provide the basis for the formation of the quadruplex in vivo in the presence of a complementary strand. 相似文献
956.
957.
芳香酸淋洗液的单柱阳离子色谱法测定碱金属,铵离子和烷基胺 总被引:7,自引:0,他引:7
研究了邻苯二甲酸、苯甲酸和对羟基苯甲酸3种芳香酸分别做淋洗液的单柱阳离子色谱法分离测定Li+、Na+、NH4+、K+、甲胺、乙胺和正丙胺7种物质。3种芳香酸做淋洗液均可将7种物质分离开,且分离结果差异不大。在淋洗液浓度相同的条件下,邻苯二甲酸做淋洗液测定的检出限较低。选择3.0 mmol/L邻苯二甲酸做淋洗液测得了上述7种物质的检出限和线性范围,并进行了叶面肥试样分析,7种物质的加标回收率在96.4%~98.6%之间。 相似文献
958.
IntroductionTheintramolecularenergytransferprocessandmechanismofrareearthcomplexeswithβ-diketoneshavebeengeneralystudiedandac... 相似文献
959.
汞电极表面电荷的快速估算 总被引:1,自引:0,他引:1
本文报导了用交流示波极谱快速估算电极表面电荷的方法。该方法使用仪器简单,测量快速,操作简便,在吸附研究中很有用处。 相似文献
960.
A novel heteronuclear complex, [Tb2Zn2L10(bipy)(H2O)2]2 (HL = -methylacrylic acid, bipy = 4,4-bipyridine), was synthesized and characterized by elemental analysis and i.r. absorption spectra. Its structure, determined by X-ray diffraction, is a discrete octanuclear molecule, in which two ZnII ions are linked by a bipy molecule and between TbIII ions, or TbIII and ZnII ions are bridged by bidentate -methylacrylato groups. The temperature dependence of the magnetic susceptibility of the complex shows strong ferromagnetic interaction between the terbium atoms. 相似文献