全文获取类型
收费全文 | 2373篇 |
免费 | 74篇 |
国内免费 | 10篇 |
专业分类
化学 | 1825篇 |
晶体学 | 32篇 |
力学 | 31篇 |
数学 | 143篇 |
物理学 | 426篇 |
出版年
2020年 | 24篇 |
2019年 | 53篇 |
2018年 | 18篇 |
2017年 | 21篇 |
2016年 | 40篇 |
2015年 | 26篇 |
2014年 | 32篇 |
2013年 | 112篇 |
2012年 | 126篇 |
2011年 | 130篇 |
2010年 | 63篇 |
2009年 | 78篇 |
2008年 | 123篇 |
2007年 | 123篇 |
2006年 | 135篇 |
2005年 | 110篇 |
2004年 | 72篇 |
2003年 | 83篇 |
2002年 | 88篇 |
2001年 | 52篇 |
2000年 | 39篇 |
1999年 | 30篇 |
1998年 | 28篇 |
1997年 | 22篇 |
1996年 | 23篇 |
1995年 | 15篇 |
1994年 | 14篇 |
1993年 | 26篇 |
1992年 | 28篇 |
1991年 | 28篇 |
1990年 | 37篇 |
1989年 | 26篇 |
1988年 | 28篇 |
1987年 | 25篇 |
1986年 | 34篇 |
1985年 | 35篇 |
1984年 | 41篇 |
1983年 | 31篇 |
1982年 | 35篇 |
1981年 | 34篇 |
1980年 | 35篇 |
1979年 | 30篇 |
1978年 | 40篇 |
1977年 | 32篇 |
1976年 | 23篇 |
1975年 | 20篇 |
1974年 | 25篇 |
1973年 | 22篇 |
1972年 | 14篇 |
1967年 | 14篇 |
排序方式: 共有2457条查询结果,搜索用时 171 毫秒
161.
162.
The proton magnetic resonance spectra of the three title carbanions have been observed in THF with potassium as a counter ion. The ortho-protons in the α-methylbenzyl carbanion are nonequivalent at room temperature. This shows that the α-carbon in this carbanion is in the near-sp2 configuration. The aromatic proton chemical shifts of the benzylpotassium obtained here are at higher shielding than those of benzyllithium reported previously by Sandel and Freedman. This seems to arise from the different ionic nature of the bonds between carbon and metal in the carbanions. 相似文献
163.
Yuji Hayashi Takeshi Matsumoto Motokazu Uemura Masato Koreeda 《Magnetic resonance in chemistry : MRC》1980,14(2):86-91
Carbon-13 NMR signals of the biologically active norditerpenoid dilactones from Podocarpus plants were fully assigned by using selective 1H decoupling, coupling constants (2JCH), spin-lattice relaxation times (T1) and correlation of the spectra of more than thirty dilactone congeners. The spectra of five nagilactones, B, C, D, E and F, which constitute representative members of three major structural types of the dilactones: (A) 8:14, 9:11-dienolide (α-pyrone) type, (B) 7α:8α-epoxy-9:11-enolide type, and (C) 7:8,9:11-dienolide type, were extensively analysed. Some characteristic steric interactions for the substituents on the ring system can be demonstrated from the spectral properties. 相似文献
164.
Soukil Mah Yukio Yamamoto Koichiro Hayashi 《Journal of polymer science. Part A, Polymer chemistry》1982,20(7):1709-1716
Radiation-induced cationic polymerization of styrene was studied in methylene chloride in the presence of triphenylsulfonium hexafluorophosphate. Acceleration in polymerization and an increase in molecular weight at a low temperature (?78°C) were observed in the presence of triphenylsulfonium salt. A study of pulse radiolysis revealed that both effects are due mainly to PF?6, which forms ion pairs with the cationic species involved in the polymerization. 相似文献
165.
166.
167.
Yukiji Shimojima Hiroshi Hayashi Tadaaki Ooka Mitsuru Shibukawa Yoichi Iitaka 《Tetrahedron letters》1982,23(51):5435-5438
The structures of a novel gastroprotective substance AI-77-B and its analogues AI-77-C, D, F and G, which are produced by Bacillus pumilus, are described. Five of the asymmetric centers of AI-77-B have S absolute stereochemistry confirmed by X-ray in combination with chemical studies. 相似文献
168.
169.
Aliu E Andringa S Aoki S Argyriades J Asakura K Ashie R Berns H Bhang H Blondel A Borghi S Bouchez J Burguet-Castell J Casper D Cavata C Cervera A Cho KO Choi JH Dore U Espinal X Fechner M Fernandez E Fukuda Y Gomez-Cadenas J Gran R Hara T Hasegawa M Hasegawa T Hayashi K Hayato Y Helmer RL Hill J Hiraide K Hosaka J Ichikawa AK Iinuma M Ikeda A Inagaki T Ishida T Ishihara K Ishii T Ishitsuka M Itow Y Iwashita T Jang HI Jeon EJ Jeong IS Joo K Jover G Jung CK Kajita T Kameda J Kaneyuki K Kato I 《Physical review letters》2005,94(8):081802
We present results for nu(mu) oscillation in the KEK to Kamioka (K2K) long-baseline neutrino oscillation experiment. K2K uses an accelerator-produced nu(mu) beam with a mean energy of 1.3 GeV directed at the Super-Kamiokande detector. We observed the energy-dependent disappearance of nu(mu), which we presume have oscillated to nu(tau). The probability that we would observe these results if there is no neutrino oscillation is 0.0050% (4.0 sigma). 相似文献
170.