全文获取类型
收费全文 | 2317篇 |
免费 | 66篇 |
国内免费 | 5篇 |
专业分类
化学 | 1758篇 |
晶体学 | 23篇 |
力学 | 20篇 |
数学 | 85篇 |
物理学 | 502篇 |
出版年
2023年 | 17篇 |
2022年 | 15篇 |
2021年 | 19篇 |
2020年 | 34篇 |
2019年 | 27篇 |
2018年 | 15篇 |
2017年 | 11篇 |
2016年 | 43篇 |
2015年 | 39篇 |
2014年 | 39篇 |
2013年 | 112篇 |
2012年 | 92篇 |
2011年 | 107篇 |
2010年 | 64篇 |
2009年 | 57篇 |
2008年 | 126篇 |
2007年 | 137篇 |
2006年 | 153篇 |
2005年 | 134篇 |
2004年 | 139篇 |
2003年 | 92篇 |
2002年 | 95篇 |
2001年 | 49篇 |
2000年 | 60篇 |
1999年 | 54篇 |
1998年 | 21篇 |
1997年 | 37篇 |
1996年 | 42篇 |
1995年 | 33篇 |
1994年 | 33篇 |
1993年 | 37篇 |
1992年 | 37篇 |
1991年 | 23篇 |
1990年 | 16篇 |
1989年 | 21篇 |
1988年 | 18篇 |
1987年 | 25篇 |
1986年 | 23篇 |
1985年 | 29篇 |
1984年 | 27篇 |
1983年 | 15篇 |
1982年 | 26篇 |
1981年 | 23篇 |
1980年 | 19篇 |
1979年 | 23篇 |
1978年 | 14篇 |
1977年 | 16篇 |
1976年 | 20篇 |
1974年 | 17篇 |
1973年 | 18篇 |
排序方式: 共有2388条查询结果,搜索用时 93 毫秒
51.
Alfred Trautwein Yutaka Maeda Frank E. Harris Helmuth Formanek 《Theoretical chemistry accounts》1974,36(1):67-76
Experimental Mössbauer spectra of the Fe57-enriched CO complex of sperm whale myoglobin (MbCO) at T= 4.2 K with and without applied magnetic field (H⊥γ) were measured to derive the sign of the electric field gradient (EFG), the quadrupole splitting ΔE Q, and the isomer shift δ of the heme iron. We find a positive EFG, δE Q = 0.363 mm/sec, and δ + 0.266 mm/sec. Molecular orbital calculations were carried out to obtain theoretical estimates of EFG and ΔE Q for several steric arrangements of the CO ligand relative to the heme group. Our results are most consistent with the conclusion that the iron is situated in the heme plane, and that a bent geometry with a Fe-C-O angle of about 135 ° is more favorable than a more symmetric structure with a linear Fe-C-O geometry. 相似文献
52.
Y. Akiyama F. Mizukami H. Izutsu M. Sato K. Maeda Y. Kiyozumi K. Sakaguchi 《Journal of Sol-Gel Science and Technology》1998,13(1-3):421-425
A novel organic-inorganic composite was prepared by a sol-gel process using hydrolysis and condensation of tetraethoxysilane (TEOS) reacted with a saccharide. During the process, ethoxy groups of the TEOS were replaced with hydroxyl groups of the saccharide and, consequently, saccharide molecules were combined with silica through their hydroxyl groups. Samples obtained under different reaction conditions were used for optical resolution of a metal chelate compound. The resolution ability of the composites was affected by the amount of water added for hydrolysis and of the saccharide. In particular, the amount of water drastically influenced the optical resolution performance. Composites obtained at the lower H2O/TEOS ratio gave the metal chelate compound a higher optical rotation. Three types of composites with the same composition were prepared by kneading, impregnation and by the sol-gel method, and were compared. The sol-gel composite showed the best optical resolution ability. It was concluded that the optical resolution ability was closely related to dispersibility of saccharide in the silica matrix. 相似文献
53.
54.
Beker H Boggild H Boissevain J Cherney M Dodd J Esumi S Fabjan CW Fields DE Franz A Hansen KH Holzer EB Humanic TJ Jacak BV Jayanti R Kalechofsky H Kobayashi T Kvatadze R Lee YY Leltchouk M Lörstad B Maeda N Medvedev A Miake Y Miyabayashi A Murray M Nagamiya S Nishimura S Noteboom E Pandey SU Piuz F Polychronakos V Potekhin M Poulard G Sakaguchi A Sarabura M Shigaki K Simon-Gillo J Sondheim W Sugitate T Sullivan JP Sumi Y van Hecke H Willis WJ Wolf K Xu N 《Physical review letters》1995,74(17):3340-3343
55.
W. K. A. Kumuduni Y. Nakata T. Okada M. Maeda 《Applied physics. B, Lasers and optics》1994,58(4):289-294
One-dimensional imaging laser-induced fluorescence spectroscopy has been used for in-situ measurements of spatial distributions of YO molecules produced during the ArF-laser ablation of YBa2 Cu3 O
7–x
in vacuum and oxygen gas environment. The time-integrated angular distribution of particles ejected in vacuum has a cos
n
form, where 11 <n < 13. When oxygen gas was introduced, YO molecules were confined in a smaller volume, and temporal changes of their spatial distribution were interpreted in terms of blast-wave formation. 相似文献
56.
Espy MA Dehnhard D Edwards CM Palarczyk M Langenbrunner JL Davis B Burleson GR Blanchard S Gibbs WR Lail B Nelson B Park BK Zhao Q Cummings WJ Delheij PP Jennings BK Henderson R Häusser O Thiessen D Brash E Jones MK Larson B Brinkmöller B Maeda K Morris CL O'Donnell JM Penttilä S Swenson D Tupa D Bennhold C Kamalov SS 《Physical review letters》1996,76(20):3667-3670
57.
58.
Changes in the fluorescence intensity of polyanions bearing 4-acryloylbenzo-18-crown-6 units on the addition of cations were studied in a mixed solvent of methanol and water at 30°C. The sensitivity of the change in fluorescence intensities of the polymers toward cations was strongly enhanced compared to that of the corresponding model compound. When alkali metal cations were added, the fluorescence intensity of the polymers decreased in the orders Li+>Na+>Cs+>Rb+>K+ in a methanol-water (19) mixture and Li+>Na+>Rb+>K+Cs+ in a methanol-water (91) mixture. Alkaline earth metal cations and alkylamine hydrochlorides decreased the fluorescence intensity of the polymers in a methanol-water (19) mixture. The cation-dependent decrease in the fluorescence intensity of the polymers was affected by the water fraction in a mixed solvent of methanol and water. 相似文献
59.
Viscous properties of partially hemolyzed erythrocyte suspensions were studied with a cone-plate viscometer. A Casson plot was successfully applied for analysis of the viscous properties. When the degree of hemolysis was increased, Casson viscosity (
c) of the partially hemolyzed erythrocyte suspensions increased, but the substitution of hemoglobin solution with the same O2-carrying capacity of hemolyzed fraction (containing ghost) reduced the
c remarkably. The yield stress (f
c) of the intact erythrocyte suspension increased with increasing hematocrit, but thef
c of partially hemolyzed erythrocyte suspension was dependent on both hematocrit and the degree of hemolysis. The apparent viscosity (
a) of erythrocyte suspension was drastically increased with the slight hemolysis, and became maximum at a certain degree of hemolysis which was dependent on both total hemoglobin concentration and shear rate. Such influence of hemolysis on the
a was also evident in the mixture of erythrocyte suspension and hemoglobin solution. These results suggest that the hemoglobin molecule plays a certain role in erythrocyte-erythrocyte interaction in their suspension, which modifies the viscosity. 相似文献
60.