全文获取类型
收费全文 | 6873篇 |
免费 | 228篇 |
国内免费 | 31篇 |
专业分类
化学 | 4534篇 |
晶体学 | 47篇 |
力学 | 167篇 |
数学 | 1053篇 |
物理学 | 1331篇 |
出版年
2023年 | 48篇 |
2022年 | 96篇 |
2021年 | 122篇 |
2020年 | 109篇 |
2019年 | 103篇 |
2018年 | 133篇 |
2017年 | 99篇 |
2016年 | 217篇 |
2015年 | 196篇 |
2014年 | 230篇 |
2013年 | 403篇 |
2012年 | 443篇 |
2011年 | 477篇 |
2010年 | 270篇 |
2009年 | 242篇 |
2008年 | 360篇 |
2007年 | 382篇 |
2006年 | 330篇 |
2005年 | 292篇 |
2004年 | 268篇 |
2003年 | 207篇 |
2002年 | 180篇 |
2001年 | 109篇 |
2000年 | 80篇 |
1999年 | 65篇 |
1998年 | 69篇 |
1997年 | 52篇 |
1996年 | 56篇 |
1995年 | 59篇 |
1994年 | 48篇 |
1993年 | 42篇 |
1992年 | 43篇 |
1991年 | 37篇 |
1990年 | 37篇 |
1989年 | 32篇 |
1988年 | 34篇 |
1987年 | 24篇 |
1986年 | 30篇 |
1985年 | 42篇 |
1984年 | 31篇 |
1983年 | 29篇 |
1982年 | 30篇 |
1981年 | 32篇 |
1977年 | 26篇 |
1934年 | 26篇 |
1933年 | 24篇 |
1932年 | 29篇 |
1930年 | 24篇 |
1929年 | 25篇 |
1927年 | 28篇 |
排序方式: 共有7132条查询结果,搜索用时 0 毫秒
141.
Microchimica Acta - Es wird die Forderung erhoben, den chemischen Nachweis von E 605 in biologischem Material auf den positiven Ausfall sämtlicher drei Komponenten von E 605 (p-Nitrophenol,... 相似文献
142.
V. Wedelich W. Mehnert K. -H. Frömming 《Journal of inclusion phenomena and macrocyclic chemistry》1987,5(5):621-624
-, and -cyclodextrin and heptakis-2,6-di-O-methyl--cyclodextrin enhance the nitrosation rate of l-ephedrine if the nitrosation assay procedure (NAP test) is applied. During this reaction with -cyclodextrin a solid inclusion compound of -cyclodextrin andN-nitrosoephedrine precipitates. Solubilities and stabilities of inclusion compounds of the cyclodextrins with ephedrine and nitrosoephedrine, respectively, explain especially the catalytic effects of some cyclodextrins on ephedrine.Part of the PhD thesis of V. Wedelich, Freie Universität Berlin, 1985. 相似文献
143.
The results of dielectric studies performed in a broad frequency range for two compounds, 4-cyanophenyl 4-n-heptylbenzoate (7BBCN) and 4-(4-cyanobutyloxy)phenyl 4- n-heptylbenzoate (7BB4CN), are compared. They have the same molecular core whereas the strongly polar CN group is attached to the benzene ring in 7BBCN or is separated from it by the butyloxy chain in 7BB4CN. 7BBCN has a nematic phase, whereas 7BB4CN exhibits a monotropic nematic and smectic A2 polymorphism. Large differences in the dielectric properties of the two substances were found. The analysis of the results led to the conclusion that the antiparallel dipole-dipole associations are considerably stronger in the substance with a decoupled CN group. 相似文献
144.
Frédérique Tellier 《合成通讯》2013,43(22):2287-2294
A stereospecific synthesis of (E,E)-9, 11, 13-tetradecatrienyl acetate and aldehyde is described. The key steps are two sequential palladium-catalyzed cross-coupling reactions between adequate organometalic reagents and the (E)-1,2-dibromoethylene. 相似文献
145.
Pawel J. Kulesza Silvia Zamponi Marcin A. Malik Krzysztof Miecznikowski Mario Berrettoni Roberto Marassi 《Journal of Solid State Electrochemistry》1997,1(1):88-93
Using Prussian blue (PB) electrodeposited on gold-covered foil as a model system, we have demonstrated the usefulness of
the time-derivative measurements of absorbance versus potential (linear potential-scan voltabsorptometry) for spectroelectrochemical
characterization of thin electrochromic films. The time-derivative signals were monitored for PB at 680 and 420 nm in potassium,
sodium and lithium electrolytes. Information obtained from cyclic voltabsorptometry is equivalent or complementary to that
from conventional cyclic voltammetry. In the case of PB films investigated in lithium electrolyte, the voltabsorptometric
time-derivative peaks are better defined than the respective voltammetric peaks. The combination of voltabsorptometry with
voltammetry enables molar absorptivity and/or film loading to be determined. Also, concentration changes of differently colored
mixed-valence redox centers can be monitored as a function of applied potential.
Received: 16 January 1997 / Accepted: 11 March 1997 相似文献
146.
K. Helios H. Maniak M. Sowa W. Zierkiewicz M. Wąsińska-Kałwa M. Giurg 《Journal of Coordination Chemistry》2017,70(20):3471-3487
The first metal complex of Phx-1 ligand, bis(2-amino-4,4α-dihydro-4α,7-dimethyl-3H-phenoxazin-3-one)nitratosilver(I), [Ag(Phx-1)2NO3], has been obtained and investigated by single crystal X-ray diffraction and vibrational spectroscopy methods. The Ag+ is bonded to heterocyclic nitrogen atoms of two organic ligands and one oxygen atom of a nitrate anion. The Phx-1 ligand coordination mode is supported by IR and Raman spectra, interpreted with the help of theoretical DFT studies. The antibacterial activity of the ligand and its Ag(I) complex as well as some reference compounds were screened against Gram-positive and Gram-negative bacteria, applying microdilution procedures. High sensitivity to the studied complex was found for Rhodococcus erythropolis and Bacillus licheniformis strains. Modified Phx-1 ligand preparation procedures are also presented. 相似文献
147.
148.
Our recent developments concerning the fabrication of polymer microchips and their applications for biochemical analyses are reviewed. We first describe two methods of fabrication of polymer microfluidic chips, namely UV-laser photoablation and plasma etching that are well suited for the prototyping and mass fabrication of microchannel networks with integrated microelectrodes. These microanalytical systems can be coupled with various detection means including mass spectrometry, and their applications in capillary electrophoresis are presented here. We also present how UV laser photoablation can be used for the patterning of biomolecules on polymer surfaces for generating two-dimensional arrays of microspots to carry out affinity assays. Finally, the use of the microchips for the development of fast affinity and immunological assays with electrochemical detection is presented, demonstrating the potential of these polymer microchips for medical diagnostics and drug discovery. 相似文献
149.
150.