全文获取类型
收费全文 | 975篇 |
免费 | 16篇 |
国内免费 | 6篇 |
专业分类
化学 | 610篇 |
晶体学 | 16篇 |
力学 | 13篇 |
数学 | 89篇 |
物理学 | 269篇 |
出版年
2021年 | 11篇 |
2020年 | 6篇 |
2019年 | 4篇 |
2018年 | 5篇 |
2017年 | 4篇 |
2016年 | 18篇 |
2015年 | 13篇 |
2014年 | 7篇 |
2013年 | 43篇 |
2012年 | 47篇 |
2011年 | 41篇 |
2010年 | 33篇 |
2009年 | 25篇 |
2008年 | 41篇 |
2007年 | 59篇 |
2006年 | 54篇 |
2005年 | 77篇 |
2004年 | 49篇 |
2003年 | 50篇 |
2002年 | 42篇 |
2001年 | 29篇 |
2000年 | 26篇 |
1999年 | 18篇 |
1998年 | 4篇 |
1997年 | 9篇 |
1996年 | 8篇 |
1995年 | 9篇 |
1994年 | 5篇 |
1993年 | 9篇 |
1992年 | 13篇 |
1991年 | 11篇 |
1990年 | 17篇 |
1989年 | 13篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 15篇 |
1985年 | 12篇 |
1984年 | 15篇 |
1983年 | 7篇 |
1982年 | 14篇 |
1981年 | 14篇 |
1980年 | 14篇 |
1979年 | 11篇 |
1978年 | 6篇 |
1977年 | 11篇 |
1976年 | 6篇 |
1975年 | 8篇 |
1974年 | 7篇 |
1968年 | 6篇 |
1967年 | 8篇 |
排序方式: 共有997条查询结果,搜索用时 15 毫秒
91.
Fujiwara M Akimune H van Den Berg AM Cribier M Daito I Ejiri H Fujimura H Fujita Y Goodman CD Hara K Harakeh MN Ihara F Ishikawa T Janecke J Kawabata T Raghavan RS Schwarz K Tanaka M Yamanaka T Yosoi M Zegers RG 《Physical review letters》2000,85(21):4442-4445
Discrete Gamow-Teller (GT) transitions 176Yb-->176Lu at low excitation energies have been measured via the ( 3He,t) reaction at 450 MeV and at 0 degrees. For 176Yb, two low-lying states are observed, setting low thresholds Q(nu) = 301 and 445 keV for neutrino ( nu) capture. Capture rates estimated from the measured GT strengths, the simple two-state excitation structure, and the low Q(nu) in Yb-Lu indicate that Yb-based nu detectors are well suited for a direct measurement of the sub-MeV solar electron-neutrino ( nu(e)) spectrum including pp neutrinos. 相似文献
92.
Hatakeyama A Oe K Ota K Hara S Arai J Yabuzaki T Young AR 《Physical review letters》2000,84(7):1407-1410
At temperatures below 2.1 K, long-lived gaseous Rb atoms in glass cells have been generated with a simple method: irradiating the cells, containing 4He gas and Rb metal, with a cw laser. The obtained atomic Rb density ( approximately 10(8) cm(-3)) decreases with a 1/e time constant of about 10 s at 1.85 K. We have performed optical pumping of the Rb atoms and measured the longitudinal electronic spin relaxation time at 1.85 K as well. For processes (such as Rb-He collisions) which do not remove the atomic Rb from the vapor, this relaxation time is found to be about 60+/-15 s. 相似文献
93.
Shinsuke Hara Hidekazu Kobayashi Hiroki I. Fujishiro Hirofumi Miki 《Surface science》2007,601(12):2415-2419
We have studied Si(0 0 1)-Ga surface structures formed at Ga coverages of slightly above 0.50 monolayer (ML) at 250 °C by scanning tunneling microscopy (STM). 4 × 2-, 5 × 2-, and 6 × 2-Ga structures were observed in a local area on the surface. The 4 × 2-Ga structure consists of three protrusions, as observed in filled- and empty-state STM images. The characters of these structures are clearly different from those of other Si(0 0 1)-Ga structures. We also performed an ab initio calculation of the energetics for several possible models for the 4 × 2-Ga structure, and clarified that the three-orthogonal-Ga-dimer model is the most stable. Also, the results of comparing the simulated STM images and observation images at various bias voltages indicate that this structural model is the most favorable. 相似文献
94.
Effect of tea polyphenols on glucan synthesis by glucosyltransferase from Streptococcus mutans 总被引:3,自引:0,他引:3
M Hattori I T Kusumoto T Namba T Ishigami Y Hara 《Chemical & pharmaceutical bulletin》1990,38(3):717-720
In the course of our studies on the development of anti-plaque agents for prevention of dental caries, we investigated effects of some of tea preparations and their individual components on the glucan synthesis catalyzed by glucosyltransferase (GTF) from Streptococcus mutans. Extracts of green tea and black tea, and polyphenol mixtures showed appreciable inhibition in the synthesis of insoluble glucan. Among the components isolated from tea infusions, theaflavin and its mono- and digallates had potent inhibitory activities at concentrations of 1-10 mM against GTF. (+)-Catechin, (-)-epicatechin and their enantiomers had moderate inhibitory activities at these concentrations, while galloyl esters of (-)-epicatechin, (-)-epigallocatechin and (-)-gallocatechin had increased inhibitory activities. 相似文献
95.
96.
Hiroaki Miyaoka Yoshinori Hara Ikuo Shinohara Takao Kurokawa Yasuji Yamada 《Tetrahedron letters》2005,46(46):7945-7949
Synthesis of the marine eicosanoid agardhilactone has been achieved. The relative and absolute configuration of agardhilactone was successfully determined. 相似文献
97.
J. Unterzaucher A. Stoll E. Wiedemann A. Friedrich F. Blumer I. Marek W. R. Kirner H. A. Taylor H. E. Achilles S. Abe R. Hara H. Sinozaki D. T. Gibson Th H. Caulfield P. L. Kirk K. Dod und E. C. Kendall 《Fresenius' Journal of Analytical Chemistry》1937,110(7-8):291-298
Ohne Zusammenfassung 相似文献
98.
Chitrasen Gupta Subedar Prasad Mahendra Sahai Teigo Asai Noriyuki Hara Yoshinori Fujimoto 《Helvetica chimica acta》2010,93(10):1925-1932
Six new lanostane triterpenes, artabotryols A, B, C1, C2, D, and E ( 1, 2, 3a, 3b, 4 , and 5 , resp.) have been isolated from the seeds of Artabotrys odoratissimus (Annonaceae). Their structures have been established as (3α,22S,25R)‐3‐hydroxy‐22,26‐epoxylanost‐8‐en‐26‐one ( 1 ), (3α,22S,25R)‐22,26‐epoxylanost‐8‐ene‐3,26‐diol ( 2 ), (3α,22S,25R,26R)‐26‐methoxy‐22,26‐epoxylanost‐8‐en‐3‐ol ( 3a ), (3α,22S,25R, 26S)‐26‐methoxy‐22,26‐epoxylanost‐8‐en‐3‐ol ( 3b ), (3α,22S,25R)‐3,22‐dihydroxylanost‐8‐en‐26‐oic acid ( 4 ) and (3α,7α,11α,22S,25R)‐3,7,11‐trihydroxy‐22,26‐epoxylanost‐8‐en‐26‐one ( 5 ) by spectroscopic studies and chemical correlations. 相似文献
99.
100.