全文获取类型
收费全文 | 3326篇 |
免费 | 134篇 |
国内免费 | 14篇 |
专业分类
化学 | 2606篇 |
晶体学 | 42篇 |
力学 | 34篇 |
数学 | 218篇 |
物理学 | 574篇 |
出版年
2023年 | 21篇 |
2022年 | 28篇 |
2021年 | 37篇 |
2020年 | 34篇 |
2019年 | 56篇 |
2018年 | 43篇 |
2017年 | 27篇 |
2016年 | 87篇 |
2015年 | 83篇 |
2014年 | 79篇 |
2013年 | 140篇 |
2012年 | 190篇 |
2011年 | 208篇 |
2010年 | 111篇 |
2009年 | 101篇 |
2008年 | 204篇 |
2007年 | 205篇 |
2006年 | 195篇 |
2005年 | 202篇 |
2004年 | 182篇 |
2003年 | 172篇 |
2002年 | 142篇 |
2001年 | 59篇 |
2000年 | 66篇 |
1999年 | 31篇 |
1998年 | 30篇 |
1997年 | 32篇 |
1996年 | 44篇 |
1995年 | 28篇 |
1994年 | 31篇 |
1993年 | 25篇 |
1992年 | 33篇 |
1991年 | 30篇 |
1990年 | 33篇 |
1989年 | 25篇 |
1988年 | 19篇 |
1986年 | 25篇 |
1985年 | 41篇 |
1984年 | 40篇 |
1983年 | 23篇 |
1982年 | 29篇 |
1981年 | 34篇 |
1980年 | 29篇 |
1979年 | 18篇 |
1978年 | 25篇 |
1977年 | 31篇 |
1976年 | 25篇 |
1975年 | 24篇 |
1974年 | 13篇 |
1973年 | 17篇 |
排序方式: 共有3474条查询结果,搜索用时 15 毫秒
61.
The determination of nanometer thick layers of poly(methyl methacrylate) coated on to the surface of poly(ethylene terephthalate) film has been investigated by high resolution pyrolysis gas chromatography without sample pretreatment or modification of the instrumentation used. A good linear relationship was observed between the quantity of the characteristic pyrolysate and the thickness of the poly(methyl methacrylate) layer; the detection limit was sufficient to enable the quantitation of poly(methyl methacrylate)-to-poly(ethylene terephthalate) film thickness ratios of 1:20000 in composite materials. 相似文献
62.
Sadowsky JD Schmitt MA Lee HS Umezawa N Wang S Tomita Y Gellman SH 《Journal of the American Chemical Society》2005,127(34):11966-11968
Molecules that bind to specific surface sites on proteins are of great interest from both fundamental and practical perspectives. We are exploring a ligand development strategy that is based on oligomers with discrete folding propensities ("foldamers"); we target a specific cleft on the cancer-associated protein Bcl-xL because this system is well characterized structurally. In vivo, this cleft binds to alpha-helical segments (BH3 domains) of other proteins. We evaluated several types of helical foldamer, built entirely from beta-amino acid residues or from mixtures of alpha- and beta-amino acid residues, and ultimately identified foldamers in the latter class that bind very tightly to Bcl-xL. Our results suggest that combining different types of foldamer backbones will be an effective and general strategy for creating high-affinity and specific ligands for protein surface sites. 相似文献
63.
64.
65.
N. Takahashi T. Shimoda Y. Fujita T. Itahashi H. Miyatake 《Zeitschrift für Physik B Condensed Matter》1995,98(3):347-351
Short-lived ions12B (beta-radioactive, T1/2=20.3 ms) sustaining nuclear spin polarization were introduced into superfluid helium at 1.7 K. It was found that the12B ions were transported as charged entities under a static electric field and that the nuclear polarization was maintained throughout the lifetime of12B nuclei. Polarization of12B was determined through beta-NMR method. Snowball, a singly charged microcluster of helium atoms formed around an impurity ion, is responsible for the behaviour and thus constitutes a suitable environment for preserving nuclear polarization of the core ions12B. In a separate experiment snowballs were produced by implanting8Li (T1/2=830 ms) into liquid helium and detected by means of alpha particles from the core ions to guarantee that the snowballs survive longer than the lifetime of12B. 相似文献
66.
The equations for a barotropic viscous gas in one space dimensiondν=(μ(?νε)ε?p ε)dt+dG,? t +?2νε=0,p=?γ with a perturbationdG are considered under the assumption thatG is only a function of bounded variation inL 2(Θ) orH 0 1 (Θ) (Θ=]0, α[) and the esistence and the uniqueness of the global solution in a class of solutions of «strong type» as well as in a class of solutions of «weak type» are proved. This result constitutes a generalization of the result of Kazhikhov [8] and that of Shelukhin [10] and contains preliminary considerations for the corrisponding stochastic equations. 相似文献
67.
68.
Katsunori Wakabayashi Mitsutaka Fujita Koichi Kusakabe Kyoka Nakada 《Czechoslovak Journal of Physics》1996,46(4):1865-1866
Anoble mechanism of spin polarization is proposed for finite graphite sheet with edge. For graphite ribbon with zigzag edge, there appear peculiar ‘edge states’. These localized states comprise nearly flat band at the Fermi level, which easily causes magnetic instability. Magnetic structure is suggested from Hartree-Fock analysis of the Hubbard model, where huge magnetic moments are induced at around both of edges by weak HubbardU and are coupled antiferromagnetically with each other. 相似文献
69.
Fujita M Nakao Y Matsunaga S Seiki M Itoh Y Yamashita J Van Soest RW Fusetani N 《Journal of the American Chemical Society》2003,125(51):15700-15701
A novel MMP inhibitor, ageladine A (1) with antiangiogenic activity was isolated from a marine sponge Agelas nakamurai. Structure 1 was determined by a combination of spectroscopic and chemical methods to be an unprecedented structure of 4-(4,5-dibromo-1H-pyrrol-2-yl)]-1H-imidazo[4,5-c]pyridin-2-amine. 相似文献
70.
Eietsu Hasegawa Shinya Takizawa Akira Yamaguchi Naoki Chiba Hiroshi Ikeda 《Tetrahedron》2006,62(27):6581-6588
Photoinduced electron-transfer reactions of several ketone substrates were studied to evaluate the utilities of 1,6-bis(dimethylamino)pyrene (BDMAP), 1,6-dimethoxypyrene (DMP), 9,10-bis(dimethylamino)anthracene (BDMAA), and 9,10-dimethoxyanthracene (DMA) as electron-donating sensitizers cooperating with 2-aryl-1,3-dimethylbenzimidazolines. BDMAP and DMP generally led higher conversion of ketones and better yield of reduction products compared to BDMAA and DMA. 相似文献