全文获取类型
收费全文 | 9667篇 |
免费 | 555篇 |
国内免费 | 1034篇 |
专业分类
化学 | 8815篇 |
晶体学 | 257篇 |
力学 | 277篇 |
综合类 | 32篇 |
数学 | 66篇 |
物理学 | 1809篇 |
出版年
2024年 | 6篇 |
2023年 | 89篇 |
2022年 | 127篇 |
2021年 | 113篇 |
2020年 | 177篇 |
2019年 | 168篇 |
2018年 | 170篇 |
2017年 | 251篇 |
2016年 | 369篇 |
2015年 | 299篇 |
2014年 | 350篇 |
2013年 | 688篇 |
2012年 | 550篇 |
2011年 | 558篇 |
2010年 | 478篇 |
2009年 | 749篇 |
2008年 | 623篇 |
2007年 | 661篇 |
2006年 | 532篇 |
2005年 | 521篇 |
2004年 | 453篇 |
2003年 | 371篇 |
2002年 | 311篇 |
2001年 | 285篇 |
2000年 | 243篇 |
1999年 | 232篇 |
1998年 | 222篇 |
1997年 | 189篇 |
1996年 | 161篇 |
1995年 | 169篇 |
1994年 | 180篇 |
1993年 | 124篇 |
1992年 | 92篇 |
1991年 | 76篇 |
1990年 | 61篇 |
1989年 | 40篇 |
1988年 | 62篇 |
1987年 | 56篇 |
1986年 | 58篇 |
1985年 | 60篇 |
1984年 | 67篇 |
1983年 | 38篇 |
1982年 | 79篇 |
1981年 | 40篇 |
1980年 | 37篇 |
1979年 | 41篇 |
1978年 | 13篇 |
1976年 | 5篇 |
1973年 | 5篇 |
1966年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
101.
A new class of low melting liquid crystalline octaalkyloxyporphyrins have been synthesised. Their Zn(II)-complexes display an interesting ligation behaviour towards amines (of varying shapes and sizes), ascribed to the steric hindrance or hydrophobic pockets on both the faces of the porphryin as evidenced from the crystal structure of Zn(II)-octabutyloxyporphyrin. 相似文献
102.
103.
Joël J. E. Moreau Luc Vellutini Catherine Bied Michel Wong Chi Man 《Journal of Sol-Gel Science and Technology》2004,32(1-3):63-67
The acid-hydrolysis of an organo-bridged bisdiethoxysilylated molecular precursor bearing urea groups, (EtO)2MeSi(CH2)3NHCONH(CH2)12NHCONH(CH2)3SiMe(OEt)2, has been performed in pure aqueous medium. Scanning electron microscopy (SEM) analysis of the resulting insoluble solid revealed plate-like forms with a lamellar structure as determined by powder X-ray diffraction (PXRD) studies with a sharp peak at 28.5 Å. The solid state 29Si MAS-NMR spectrum of this bridged siloxane hybrid is consistent with a moderately condensed material with complete preservation of the Si–C bonds throughout the hybrid network. In comparison, the classical sol–gel hydrolysis-condensation of the molecular precursor in ethanol with stoichiometric amount of water and fluoride anion as catalyst produced an amorphous featureless solid. 相似文献
104.
合成了两种含氰基联苯液晶基团的新型聚对亚苯基亚乙炔基(PPE)类交替共聚物,并对其进行了结构表征和性能研究.示差扫描量热仪(DSC)和偏光显微镜(POM)的结果证明了在液晶单元含量较大时聚合物才会出现明显的液晶形态.荧光光谱表明,在降温前后液晶聚合物的发光光谱发生了明显的变化.同时,对聚合物进行能量转移研究发现随着溶液浓度的增加,Frster能量转移更加完全;另外,利用原子力显微镜(AFM)对聚合物降温前后的形态变化进行了观察.结果表明,液晶性质可以导致聚合物形态的变化进而带来发光光谱的改变,为今后制备液晶可控型发光聚合物提供了理论依据. 相似文献
105.
Yanfeng Zhao Nengsheng Ye Rongli Zhang Xue Feng Guoan Luo Yiming Wang 《Frontiers of Chemistry in China》2007,2(4):422-427
High-resolution two-dimensional gel electrophoresis (2-DE), followed by computer-assisted image analysis was used to screen
protein patterns of normal and infarcted myocardial tissues for quantitative and qualitative differences in protein expression.
In the gels of pH 5–8 immobilized pH gradient (IPG) strips, 851 protein spots were detected in normal myocardial tissue and
1 032 protein spots were resolved in infarcted myocardial tissue. Thirteen protein spots only expressed in normal myocardial
tissue, and 14 protein spots only expressed in infarcted myocardial tissue. Results also showed that 49 protein spots displayed
quantitative changes in expression between normal and infarcted myocardial tissue. Eleven protein spots were subjected to
mass spectrometry (MS) analysis and seven proteins were identified by peptide mass fingerprinting (PMF). These proteins may
be involved in cardiovascular injury, and could play an important role in the treatment of coronary heart disease.
__________
Translated from Chemical Journal of Chinese Universities, 2006, 8(27): 1467–1471 [译自: 高等学校化学学报] 相似文献
106.
107.
The aim of this work was to investigate, for the first time, the potential of the enzyme glutathione S-transferase I (isoenzyme GST-I) for uses in analytical chemistry. A novel fiber-optic biosensor for the detection and determination of the triazine herbicide atrazine was developed based on maize GST-I expressed in E. coli. The sensing bioactive material was a three-layer mini-sandwich. The enzyme was immobilized on the outer layer that consisted of a hydrophilic polyvinylidenefluoride membrane. This membrane was supported on an inner glass disk by means of an intermediate binder sol–gel layer that incorporated bromcresol green (BCG). The biosensor operated in a static mode at 25 °C and the rate of the enzymatic reaction, using atrazine as a substrate, served as an analytical signal. A calibration curve was obtained for atrazine, with analytically useful concentration range 2.52–125 μM. The sensor detection limit was 0.84 μM. The reproducibility of atrazine sensing was in the order of ±3–5%. The method was successfully applied to the determination of this herbicide in real water samples, without sample preparation steps. Atrazine recovery ranged between 85 and 110%. No interference from other pesticides, such as alachlor and carbaryl was observed in the absence of atrazine. The immobilized enzyme retained about 75% of its original activity after 1 month use. Simply unscrewing the terminal holding ring of the probe and placing a new bioactive sandwich could easily replace a deteriorated mini-sandwich. 相似文献
108.
109.
Summary The equation for the potential energy of interactions established for gas-liquid chromatography has been confirmed in reversed phase liquid chromatography. Equations derived for molecular polarizabilities of PAHs and their retention data have very high correlation coefficients. The results indicate that the inductive effect between solute and stationary phase is the main one and the dispersive effect is very small compared with the inductive effect but its contribution increases with the carbon chain length of the stationary phase. 相似文献
110.
R. Leboda 《Chromatographia》1980,13(9):549-554
Summary The surface properties of complex adsorbents prepared through the pyrolysis of benzyl and n-heptyl alcohols and their mixtures
on the surface of silica gel were investigated. The reactions were carried out in an autoclave at 500°C. A series of adsorbents
having different porous structure, chemical nature of the adsorption centers and their topography were obtained. The best
resolution of different mixtures was obtained by the carbon-silica adsorbent prepared through the pyrolysis of n-heptanol. 相似文献