全文获取类型
收费全文 | 871篇 |
免费 | 23篇 |
国内免费 | 1篇 |
专业分类
化学 | 796篇 |
晶体学 | 4篇 |
力学 | 4篇 |
数学 | 16篇 |
物理学 | 75篇 |
出版年
2023年 | 5篇 |
2022年 | 5篇 |
2021年 | 7篇 |
2020年 | 11篇 |
2019年 | 13篇 |
2018年 | 8篇 |
2017年 | 11篇 |
2016年 | 12篇 |
2015年 | 8篇 |
2014年 | 31篇 |
2013年 | 69篇 |
2012年 | 54篇 |
2011年 | 67篇 |
2010年 | 27篇 |
2009年 | 40篇 |
2008年 | 70篇 |
2007年 | 44篇 |
2006年 | 55篇 |
2005年 | 55篇 |
2004年 | 54篇 |
2003年 | 42篇 |
2002年 | 50篇 |
2001年 | 13篇 |
2000年 | 11篇 |
1999年 | 9篇 |
1998年 | 11篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 6篇 |
1994年 | 6篇 |
1993年 | 13篇 |
1992年 | 6篇 |
1990年 | 2篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 7篇 |
1982年 | 9篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 9篇 |
1978年 | 6篇 |
1977年 | 2篇 |
1976年 | 6篇 |
1975年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有895条查询结果,搜索用时 46 毫秒
251.
252.
253.
A remarkable enhancement of the extraction of lanthanoids(Ⅲ)(Ln) with β-diketones in the presence of a Lewis base, so-called synergistic effects, would be caused by the adduct formation of the β-diketonates with the Lewis base. The trend of the variation of the adduct formation constants across the lanthanoid series may be different among β-diketones used. It has also been observed that the trend across lanthanoid series and also the values of the enthalpy change in the adduct formation of the 2-thenoyltrifluoroacetonates(TTA) with 1,10-phenanthroline(phen) are very similar to those with 2,25-bipyridyl(bpy), although the values of the adduct formation constants with the former are larger than those with the latter. 相似文献
254.
255.
Naotoshi Nakashima Takeshi Tokunaga Yuko Nonaka Takashi Nakanishi Hiroto Murakami Takamasa Sagara 《Angewandte Chemie (International ed. in English)》1998,37(19):2671-2673
Two reversible one-electron transfers are observed for an electrode device made from C60 and an artificial lipid (see schematic drawing). Cyclic voltammetric studies reveal that the redox couples are unchanged even after 50 cycles, thus indicating that the C60 radical monoanion and the C60 dianion generated in aqueous solution are very stable. 相似文献
256.
257.
Various spatiotemporal patterns of dark and light stripes are formed in the Ag and Sb co-electrodeposition system. In this research, we investigate the time-evolution of the stripe width of a spatiotemporal stripe pattern with a size of ca. 10 μm. The results show that the stripe width increases with time and is eventually saturated. Such a phenomenon is predicted by some theories of spinodal decomposition of materials with chemical reactions in a nonequilibrium system. This suggests that the pattern is formed by the spinodal decomposition of metal alloys, Ag and Sb, with chemical reactions in a nonequilibrium system, which has not yet been reported in a metallic system. 相似文献
258.
Yasuko Matsumoto Yuko Matsushima-Hibiya Tsuyoshi Nakano Masafumi Yamamoto Kikuo Iwabuchi Takashi Sugimura Keiji Wakabayashi 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2007,83(6):175-178
Crude extracts from larvae, pupae and adults of cabbage white butterflies, Pieris rapae and Pieris brassicae, and green-veined butterfly, Pieris napi, have an ability to induce apoptosis in the human cancer cell lines. As apoptosis inducing protein, pierisin-1 and -2 have been isolated from pupae of P. rapae and P. brassicae, respectively, and shown to exhibit DNA ADP-ribosylating activity. Although the highest activity was detected in the late phase of larvae and early phase of pupae, certain activity was found in adult butterflies. In order to investigate distribution of substances having pierisin-like activities in butterflies, many species need to be analyzed. However, fresh samples of larvae and pupae are hard to obtain, especially if samples are of scarce species or from overseas. The usage of adult butterflies is practical to examine the distribution of pierisin-like activity in many species. In this study, we examined the cytotoxicity of crude extracts from adults of P. rapae against HeLa cells and DNA ADP-ribosylation ability during storage for 1, 2 and 8 weeks at room temperature after killing adult butterflies after eclosion. Body weights decreased to 18% for 8 weeks through dehydration. Cytotoxicity of samples from butterfly kept for 1, 2 and 8 weeks decreased to 47, 39 and 22%, respectively, of the control value. DNA ADP-ribosylating activity of the samples also decreased to 30, 27 and 23%. Similar reduction was observed on western blot analysis with anti-pierisin-1 antibody. Fortunately, these results suggest that cytotoxic and DNA ADP-ribosylating activity persists to some extent in the body after killing, at least for 8 weeks. Thus, butterfly adult samples kept for two months at room temperature can still be useful for examination of the presence of substance having pierisin-like activity. 相似文献
259.
Kazuo Sasazawa Yuko Yamada Akiko Fujisawa Toshikazu Saitoh Katsuya Ueno Kazuya Oharu Hideo Sawada 《Colloid and polymer science》2005,283(7):812-816
Self-assembled fluorinated molecular aggregates formed by fluoroalkyl end-capped N-(1,1-dimethyl-3-oxobutyl)acrylamide oligomers, N,N-dimethylacrylamide oligomers, and acrylic acid oligomers in methanol could selectively recognize fluoresceins as guest molecules to form a new class of fluorinated aggregates-fluorescein nanocomposites. These fluorinated fluorescein nanocomposites that are obtained exhibit an extraordinarily enhanced light absorption (max ca. 440 nm) compared to that (maxs 452, 480 nm) of the parent fluorescein in the absence of fluorinated aggregates. 相似文献
260.
Photochemical efficiency of o-quinodimethane (3) ring closure at room temperature was determined by using a time-delayed, two-color photolysis technique. o-Quinodimethane (3) was generated by the photolysis of 1,2-bis[(phenylseleno)methyl]benzene (1) by a KrF (248 nm) laser pulse and thus-generated 3 was photolyzed by a subsequent XeCl (308 nm)/XeF (351 nm) laser pulse with varying delay time of 0 to 3 s. The time profile of 3 was monitored by the chemical analyses of benzocyclobutene (5) (a photochemical product of 3), which was formed by a one-photon process, and the spiro dimer of 3 (4) (a thermal product of 3) in the two-color photolysis experiments. The time profile of 3 followed a second-order decay kinetics. The photochemical efficiency was obtained by the analysis of the delay-time dependence of the product yields; those of the consumption of 3 and the conversion 3-->5 by a single pulse of the excimer laser were 81% and 5.7% for the XeCl laser, and 73% and 2.3% for the XeF laser. This difference was attributed to the different excited states involved in the photolysis. In contrast to the photolysis of 3 in argon or rigid organic matrixes, it was revealed that photochemical conversion 3-->5 was not the main path in the solutions, and intermolecular reactions predominated. 相似文献