全文获取类型
收费全文 | 1180篇 |
免费 | 39篇 |
国内免费 | 1篇 |
专业分类
化学 | 905篇 |
晶体学 | 6篇 |
力学 | 17篇 |
数学 | 36篇 |
物理学 | 256篇 |
出版年
2021年 | 13篇 |
2020年 | 9篇 |
2019年 | 24篇 |
2018年 | 15篇 |
2017年 | 10篇 |
2016年 | 17篇 |
2015年 | 14篇 |
2014年 | 30篇 |
2013年 | 62篇 |
2012年 | 58篇 |
2011年 | 59篇 |
2010年 | 33篇 |
2009年 | 24篇 |
2008年 | 59篇 |
2007年 | 62篇 |
2006年 | 79篇 |
2005年 | 65篇 |
2004年 | 41篇 |
2003年 | 49篇 |
2002年 | 49篇 |
2001年 | 33篇 |
2000年 | 31篇 |
1999年 | 23篇 |
1998年 | 11篇 |
1997年 | 10篇 |
1996年 | 12篇 |
1995年 | 13篇 |
1994年 | 11篇 |
1993年 | 16篇 |
1992年 | 16篇 |
1991年 | 10篇 |
1990年 | 23篇 |
1989年 | 13篇 |
1988年 | 17篇 |
1987年 | 13篇 |
1986年 | 21篇 |
1985年 | 16篇 |
1984年 | 26篇 |
1983年 | 13篇 |
1982年 | 15篇 |
1981年 | 12篇 |
1980年 | 12篇 |
1979年 | 7篇 |
1978年 | 8篇 |
1977年 | 5篇 |
1976年 | 10篇 |
1975年 | 9篇 |
1974年 | 9篇 |
1971年 | 4篇 |
1968年 | 4篇 |
排序方式: 共有1220条查询结果,搜索用时 15 毫秒
1.
Three new cytotoxic polyacetylenes, PQ-1 (1), PQ-2 (2) and PQ-3 (3), have been isolated from Panax quinquefolium. The structures of these acetylenes were determined by analyses of their 1H-1H and 1H-13C COSY spectra. All these compounds exhibited strong cytotoxic activities against leukemia cells (L 1210) in tissue culture. 相似文献
2.
J. Fujimoto T. Ishikawa M. Jimbo T. Kaneko T. Kon Y. Kurihara M. Kuroda Y. Shimizu Y. Yasui 《Pramana》2007,69(5):943-946
We report the recent development on the SUSY calculations with the help of GRACE system. GRACE/SUSY/1LOOP is the computer
code which can generate Feynman diagrams in the MSSM automatically and compute one-loop amplitudes in the numerical way. We
present new results of various two-body decay widths and chargino pair production at ILC (international linear collider) at
one-loop level.
相似文献
3.
Within the large literature on inter-organizational networks, there has been some discussion of linking-pin organizations and the role they play in integrating these networks. Based on this verbal specification of linking-pin organizations, we construct operational criteria and empirical methods for identifying these structurally important organizations in potentially large and complex inter-organizational networks. These methods are based on ideas drawn from blockmodeling, structural holes, centrality and centralization of networks, and identifying cut-points in networks. These methods are applied to a constructed example and then to real empirical inter-organizational networks. Implications and contrasts with other methods are discussed, together with some open problems. 相似文献
4.
S Watanabe R R Anderson S Brorson G Dalickas J G Fujimoto T J Flotte 《Photochemistry and photobiology》1991,53(6):757-762
Threshold radiant exposures for grossly apparent immediate whitening and ultrastructural alterations of melanosomes in black guinea pig skin were determined for a series of red visible laser pulses ranging from 4 x 10(-4) to 6.5 x 10(-14) s. Threshold exposures for melanosomal injury were found to be independent of pulsewidth when the pulsewidths were below the estimated thermal relaxation time of melanosomes. Threshold radiant exposures for melanosomal injury were found to increase when the pulsewidths were approximately equal to or above the thermal relaxation time of melanosomes. At longer pulse durations, fracturing of melanosomes was not observed despite the longer exposures necessary for injury. Instead, perimelanosomal vacuoles were noted. These findings are consistent with the theory of selective photothermolysis and provide evidence for the thermal initiation of melanosomal disruption. 相似文献
5.
Shigeru Tasaka Norihiro Inagaki Masaaki Igawa 《Journal of Polymer Science.Polymer Physics》1991,29(6):691-694
The permeability of annealed poly (l-(trimethylsilyl)-l-propyne) was studied from the viewpoint of structural information obtained from x-ray diffraction and density. The sample cast from benzene solution had low density (0.82 g/cm3) and high permeability, whereas the annealed sample had a higher density (0.88 g/cm3) and permeability lower by two orders of magnitude. The smaller-angle x-ray diffraction peak for each sample, which was likely to reflect the distance between intermolecular chains, increased in intensity and shifted toward higher angle, corresponding to the change of the density with annealing. The logarithmic oxygen permeability was proportional to the density, namely the free volume fraction correlated with the diffusion coefficient and controlled by annealing and swelling by alcohols. 相似文献
6.
13C NMR studies showed that the population of the norcaradiene form of the title systems containing p-CH3O, H, and p-CF3 on the 7-aryl group increases in this order. The result is consistent with the prediction from the π-acceptor strength of the aryl group estimated by INDO calculations. 相似文献
7.
8.
9.
Bond IA Budding E Conway MJ Fenton KB Fujii H Fujii Z Fujimoto M Hasegawa H Hayashida N Honda M Hotta N Humble JE Kabe S Kasahara K Kifune T Masaike A Matsubara Y Mitsui K Miura Y Mori M Murakami K Muraki Y Nagano M Nakamura K Nakamura T Norris PM Ohashi Y Okada A Saito T Sakata M Sato H Shibata S Shima M Storey JR Tanimori T Teshima M Torii S Uchino K Watase Y Woodhams MD Yamamoto Y Yock PC Yuda T 《Physical review letters》1988,61(20):2292-2295
10.
Adachi I Aihara H Dijkstra HB Enomoto R Fujii H Fujii K Fujii T Fujimoto J Fujiwara N Hayashii H Higashi S Iida N Imanishi A Ikeda H Ishii T Itoh R Iwasaki H Iwata S Kajikawa R Kamae T Kato S Kawabata S Kichimi H Kishida T Kobayashi M Kuroda S Kusuki N Maruyama A Maruyama K Masuda H Matsuda T Miyamoto A Morimoto T Nakamura K Nitoh O Noguchi S Ochiai F Okuno H Okusawa T Ohshima T Ozaki H Sato T Sai F Shimonaka J Shimozawa K Shirahashi A Sugahara R Sugiyama A Suzuki S Suwada T Takahashi K 《Physical review letters》1988,60(2):97-100