全文获取类型
收费全文 | 599篇 |
免费 | 14篇 |
专业分类
化学 | 433篇 |
晶体学 | 3篇 |
力学 | 8篇 |
数学 | 18篇 |
物理学 | 151篇 |
出版年
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 9篇 |
2018年 | 4篇 |
2017年 | 5篇 |
2016年 | 13篇 |
2015年 | 9篇 |
2014年 | 10篇 |
2013年 | 15篇 |
2012年 | 24篇 |
2011年 | 29篇 |
2010年 | 14篇 |
2009年 | 6篇 |
2008年 | 32篇 |
2007年 | 25篇 |
2006年 | 41篇 |
2005年 | 36篇 |
2004年 | 17篇 |
2003年 | 16篇 |
2002年 | 12篇 |
2001年 | 18篇 |
2000年 | 16篇 |
1999年 | 11篇 |
1998年 | 13篇 |
1997年 | 12篇 |
1996年 | 10篇 |
1995年 | 13篇 |
1994年 | 14篇 |
1993年 | 4篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 13篇 |
1989年 | 10篇 |
1988年 | 11篇 |
1987年 | 16篇 |
1986年 | 7篇 |
1985年 | 13篇 |
1984年 | 11篇 |
1983年 | 14篇 |
1982年 | 9篇 |
1981年 | 8篇 |
1980年 | 4篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1975年 | 9篇 |
1974年 | 5篇 |
1973年 | 2篇 |
1966年 | 4篇 |
1927年 | 2篇 |
排序方式: 共有613条查询结果,搜索用时 209 毫秒
11.
12.
Y. Yamada T. Kumagawa Y. T. Yamada T. Tominaga 《Journal of Radioanalytical and Nuclear Chemistry》1995,201(5):417-429
Mössbauer parameters of tin compounds, Sn(CH3)2H4–n (n=0, 1, 2, 3, 4), isolated in low temperature matrices were related to electronic properties at the tin nuclei obtained by molecular orbital calculations. Structures of novel species, Sn(CH3)2 and Sn(CH3)H, produced via photodissociation of matrix-isolated Sn(CH3)3H and Sn(CH3)2H2, respectively, were determined on the basis of molecular orbital calculations as compared with Mössbauer parameters. The correlations between Mössbauer quadrupole splitting and calculated electric field gradient using STO-3G or MINI-4 were found to depend on the valence of tin atoms because of poor allowance for basis sets in describing highly polar molecules. 相似文献
13.
Kihachiro Takahara Masahide Sasaki Arthur J. Tomisek Samuel Natelson 《Microchemical Journal》1974,19(3):319-329
A reagent is developed for increasing the sensitivity of the direct o-toluidine procedure for glucose so that the reaction may be carried out at temperatures as low as 37 °C.The sensitivity is achieved by eliminating all water from the system, except for a minute percentage introduced with the samples and by using a high boric acid concentration. Under these conditions protein does not precipitate and lipids remain dissolved. At 55 °C, interference from bilirubin at a concentration of 20 mg/100 ml is 3.5%.Blood may be collected with sodium fluoride since it does not interfere in the procedure. The rate of color development is slower for aqueous standards than it is for serum at the lower temperatures. This may be corrected by preparing the standards in a 6% albumin solution.Results obtained by applying the reagent with the continuous flow system of analysis (Technicon), and with the discrete sample analyzers, Beckman DSA, Lars Jungberg Autolab (Sweden), Robot Chemist, and RaBA (Japan) are reported.The reagent is useful as a spray reagent for sugar identification on thin-layer chromatography plates. Heating at different temperatures permits the differentiation between certain sugars with similar Rf values. 相似文献
14.
A new hydroformylation of alkenes using carbon dioxide as a reactant is shown to take place in the presence of ruthenium cluster complexes and halide salts. Similar or even better yields of alcohols were formed as compared to the conventional hydroformylation with CO under the same reaction conditions. The reaction proceeded in three steps: CO2 is first converted to CO; then it is used as a reagent for hydroformylation to give aldehyde; subsequently, it is hydrogenated to alcohol. ESI-mass spectrometric analyses of the reaction solutions indicated formation of four kinds of ruthenium anionic complexes including tetra-, tri-, and mononuclear species. On the basis of experimental findings, possible roles of these complexes are discussed. 相似文献
15.
16.
Yoshinori Tominaga Hiroto Okuda Shinya Kohra Hisako Mazume 《Journal of heterocyclic chemistry》1991,28(5):1245-1255
Reaction of various types of enaminones, which are prepared by the condensation of 1,3-dicarbonyl compounds with aromatic amines, with carbon disulfide in the presence of sodium hydroxide as the base in dimethyl sulfoxide to give the corresponding enamino dithiocarboxylates, 1,3-thiazines and trithiones. Enamino dithiocarboxylates are cyclized under refluxing in diphenyl ether to give the fused quinoline derivatives. The reaction of 6-arylamino-1,3-dimethyluracils with excess carbon disulfide in the presence of sodium hydroxide and subsequent methylation with dimethyl sulfate gave directly the corresponding 1,3-dimethyl-5-methylthiopyrimido[4,5-b]quinoline-2,4(1H,3H)-diones. 相似文献
17.
Masahide Shimokawabe Atsushi Ohi Nobutsune Takezawa 《Reaction Kinetics and Catalysis Letters》1994,52(2):393-397
Over metal oxides (SiO2, ZrO2, Al2O3, MgO, La2O3, and CaO) with-H values of metal oxide formation higher than 700 kJ/mol, C3H6 reacts with NO2 in preference to O2. 相似文献
18.
Yoshinori Tominaga Syuichirou Ohno Shinya Kohra Hiroshi Fujito Hisako Mazurae 《Journal of heterocyclic chemistry》1991,28(4):1039-1042
N-Bis(methylthio)methylenecyanamide ( 1 ) was allowed to react with active methylene compounds (methyl cyanoacetate, dimethyl malonate, ethyl acetoacetate, ethyl phenylacetate) in the presence of potassium carbonate or potassium hydroxide in dimethyl sulfoxide followed by the treatment using appropriate a base or an acid to give the corresponding 6-methylthiouracil derivatives in 15–80% yields. These uracil derivatives are found to be useful intermediates for the synthesis of 6-aminouracils and fused pyrimidine derivatives. 相似文献
19.
H. Kagetsu N. Shioyasu N. Fukunishi M. K. Kubo Y. Sakai T. Tominaga K. Nishiyama K. Nagamine 《Hyperfine Interactions》1994,84(1):517-520
We have carried out SR experiments on [Co(NH3)6]Cl3 and [Co(ND3)6]Cl3. At 293 K, all the muons implanted into the complexes were in the diamagnetic state. The observed Gaussian-type muon spin relaxation function proved that the internal magnetic field was caused by nuclear dipole moments of the atoms in the complexes. In addition, another exponential-type muon spin relaxation function was observed in [Co(ND3)6]Cl3 below 50 K. 相似文献
20.