全文获取类型
收费全文 | 3570篇 |
免费 | 95篇 |
国内免费 | 18篇 |
专业分类
化学 | 2585篇 |
晶体学 | 98篇 |
力学 | 47篇 |
数学 | 467篇 |
物理学 | 486篇 |
出版年
2022年 | 52篇 |
2021年 | 50篇 |
2020年 | 40篇 |
2019年 | 51篇 |
2018年 | 34篇 |
2017年 | 29篇 |
2016年 | 78篇 |
2015年 | 80篇 |
2014年 | 82篇 |
2013年 | 194篇 |
2012年 | 232篇 |
2011年 | 305篇 |
2010年 | 170篇 |
2009年 | 132篇 |
2008年 | 219篇 |
2007年 | 218篇 |
2006年 | 199篇 |
2005年 | 178篇 |
2004年 | 142篇 |
2003年 | 122篇 |
2002年 | 122篇 |
2001年 | 70篇 |
2000年 | 54篇 |
1999年 | 42篇 |
1998年 | 33篇 |
1997年 | 34篇 |
1996年 | 53篇 |
1995年 | 47篇 |
1994年 | 28篇 |
1993年 | 32篇 |
1992年 | 40篇 |
1991年 | 27篇 |
1990年 | 25篇 |
1989年 | 33篇 |
1988年 | 20篇 |
1987年 | 24篇 |
1986年 | 17篇 |
1985年 | 37篇 |
1984年 | 34篇 |
1983年 | 18篇 |
1982年 | 24篇 |
1981年 | 20篇 |
1980年 | 26篇 |
1979年 | 24篇 |
1978年 | 18篇 |
1977年 | 32篇 |
1976年 | 23篇 |
1975年 | 12篇 |
1973年 | 18篇 |
1972年 | 12篇 |
排序方式: 共有3683条查询结果,搜索用时 296 毫秒
61.
Ignés-Mullol J Claret J Albalat R Crusats J Reigada R Romero MT Sagués F 《Langmuir : the ACS journal of surfaces and colloids》2005,21(7):2948-2955
Preparation of Langmuir monolayers of a mixture of trans- and cis-isomers of an azobenzene derivative, 4-[4-[(4-octylphenyl)azo]phenoxy]butanoic acid, results in the segregation of birefringent trans-isomer domains embedded in an isotropic medium of cis-isomers. Brewster angle microscopy observations allow us to identify different textures inside the domains depending on surface pressure, temperature, and domain size. The evolution of the monolayer in the dark, from initial droplets formed after spreading to a stable stripe texture, is described. The dynamics of domain coalescence and some morphological transitions induced by temperature and surface pressure changes are also discussed. A simple theoretical model is included to supplement some of these experimental observations. 相似文献
62.
Cyclisation of the title compounds leads to mixtures of the expected 4H-cyclopental[b]pyrrol-4-ones (1), the corresponding 6-ones (3) by a single rearrangement, and the cyclopenta[c]pyrrol-4-ones (4) by a double rearrangement, the proportions depending upon the substituents.The 1H NMR spectra of 2-methyl-4H-cyctopenta[b]thiophen-6-one (3f) shows 6J long range coupling, but this is absent in the corresponding pyrroles (3c,d). The 13C spectra of 1 and 3 cannot be interpreted on the basis of substituent chemical shifts in pyrroles and thiophens, and are clearly -CH = CH-X (X = NMe, NPh, S) bridged derivatives of cyclopent-2-enone. 相似文献
63.
Teresa Kowalska 《Monatshefte für Chemie / Chemical Monthly》1985,116(10):1129-1132
An explanation is given for the two possible ways of determination of the activity coefficients of solutes, when applying a new thermodynamic model of adsorption and partition chromatography, i. e. the binary solutions model. 相似文献
64.
Quintanar L Yoon J Aznar CP Palmer AE Andersson KK Britt RD Solomon EI 《Journal of the American Chemical Society》2005,127(40):13832-13845
65.
Heterogeneous fluorescence immunoassays have been automated using flow injection manifolds incorporating thiophilic gel solid phase reactors to separate antibody-bound and unbound analyte molecules. Antibody elution is achieved by changes in ionic strength, thus allowing the use of pH sensitive fluorescent labels. This facilitates the development of dual analyte systems, in which two competitive immunoassays with separate labels are monitored in parallel. Detection of the fluorophores by high speed synchronous fluorescence scanning while the flow is briefly stopped utilises either one synchronous interval which detects both fluorophores, or two separate scans at different wavelength intervals, one for each fluorophore. Simultaneous analyses of serum albumin and transferrin exemplify these novel approaches. Spectroscopic interferences are very small, analyte recoveries are close to 100%, with a relative standard deviation of 5-6% and a sampling rate of 20 h-1. 相似文献
66.
Teresa Borowia Marek Mączyński Marek Pietraszkiewicz Oksana Pietraszkiewicz 《Journal of inclusion phenomena and macrocyclic chemistry》1999,35(1-2):131-138
The crystal structure of the molecular complex of C-undecylcalix[4]resorcinarene with dioxane has been determined by X-ray analysis. The asymmetric unit contains one host and four guest molecules. The calix[4]resorcinarene moiety adopts a bowl conformation with C4v
symmetry. Four undecyl chains are axially oriented. Calix molecules are packed in a bowl-to-bowl fashion with alternating hydrophilic and hydrophobic layers. One of the hydrophilic dioxane molecules is located at the rim of the calix moiety and is hydrogen bonded to the other one. There is no interaction to attract, or direct the dioxane molecule into the interior of the cavity. There is an exo complex formed. The dioxane molecules – located in the hydrophobic part – are highly disordered. 相似文献
67.
68.
Tapan K. Chattopadhyay Rex A Palmer Daruka Mahadevan 《Journal of chemical crystallography》1995,25(4):195-199
The crystal and molecular structure of pindolol, 1-(1H indol-4-yloxy)-3-[(1-methylethyl)amino]-2-propanol, has been determined by direct methods. Crystals are tetragonal,
,a=b=15.809(4),c=11.246(2) Å,Z=8,D
c=1.174 mg m–3. The finalR-factor for 2271 reflections withI>2(I) is 0.038. Refinement by full-matrix least-squares on F2 also enabled the absolute configuration of the structure to be established. The molecule is essentially planar, including much of the side-chain which is stabilized by the existence of two intramolecular H-bonds, between the ethyl oxygen and OH group, and between the OH and side-chain amide groups, respectively. The crystal structure is formed by three intermolecular hydrogen bonds including two side-chain-side-chain interactions, between ethyl oxygen to amide and OH to amide, and an interaction between the side-chain OH to indole NH. 相似文献
69.
70.
Cinabro D Henderson S Liu T Saulnier M Wilson R Yamamoto H Bergfeld T Eisenstein BI Gollin G Ong B Palmer M Selen M Thaler JJ Sadoff AJ Ammar R Ball S Baringer P Bean A Besson D Coppage D Copty N Davis R Hancock N Kelly M Kwak N Lam H Kubota Y Lattery M Nelson JK Patton S Perticone D Poling R Savinov V Schrenk S Wang R Alam MS Kim IJ Nemati B O'Neill JJ Severini H Sun CR Zoeller MM Crawford G Daubenmier CM Fulton R Fujino D Gan KK Honscheid K Kagan H Kass R Lee J Malchow R Morrow F Skovpen Y 《Physical review letters》1994,72(10):1406-1410