全文获取类型
收费全文 | 1456篇 |
免费 | 31篇 |
国内免费 | 12篇 |
专业分类
化学 | 935篇 |
晶体学 | 19篇 |
力学 | 10篇 |
数学 | 135篇 |
物理学 | 400篇 |
出版年
2021年 | 11篇 |
2020年 | 12篇 |
2019年 | 23篇 |
2018年 | 8篇 |
2017年 | 15篇 |
2016年 | 21篇 |
2015年 | 16篇 |
2014年 | 32篇 |
2013年 | 66篇 |
2012年 | 75篇 |
2011年 | 95篇 |
2010年 | 38篇 |
2009年 | 48篇 |
2008年 | 82篇 |
2007年 | 83篇 |
2006年 | 86篇 |
2005年 | 88篇 |
2004年 | 84篇 |
2003年 | 68篇 |
2002年 | 52篇 |
2001年 | 38篇 |
2000年 | 32篇 |
1999年 | 18篇 |
1998年 | 19篇 |
1997年 | 21篇 |
1996年 | 24篇 |
1995年 | 9篇 |
1994年 | 16篇 |
1993年 | 15篇 |
1992年 | 15篇 |
1991年 | 18篇 |
1990年 | 15篇 |
1989年 | 17篇 |
1988年 | 17篇 |
1987年 | 8篇 |
1986年 | 13篇 |
1985年 | 23篇 |
1984年 | 26篇 |
1983年 | 11篇 |
1982年 | 17篇 |
1981年 | 19篇 |
1980年 | 15篇 |
1979年 | 11篇 |
1978年 | 12篇 |
1976年 | 8篇 |
1975年 | 16篇 |
1974年 | 5篇 |
1973年 | 8篇 |
1972年 | 5篇 |
1968年 | 4篇 |
排序方式: 共有1499条查询结果,搜索用时 15 毫秒
1.
Yamashita Hiromi Ariyuki Masao Yoshizawa Katsuhiro Kida Keiko Ohshiro Satoshi Anpo Masakazu 《Research on Chemical Intermediates》2004,30(2):235-245
The photocatalytic reactivities of chromium-containing mesoporous silica molecular sieves (Cr-HMS) under visible light irradiation have been investigated. Cr-HMS involves tetrahedral chromium oxide (Cr-oxide) moieties which are highly dispersed and incorporated in the framework of molecular sieve with two terminal Cr=O groups. In the presence of propane with molecular oxygen, a partial oxidation proceeded under visible light irradiation to produce acetone and acrolein, with high selectivity, while a complete oxidation proceeded under UV light irradiation mainly to produce CO2. The charge-transfer excited state of the tetrahedral Cr-oxide moieties plays a significant role in the photocatalytic reactions. 相似文献
2.
3.
4.
Masato Matsugi Masakazu Hasegawa Sachina Okamoto Yoshimi Ikeya Yuji Mori 《Tetrahedron letters》2007,48(23):4147-4150
A modified light-fluorous Mukaiyama reagent bearing a C8F17 tag was prepared and examined in ester and amide forming condensation reactions. Following the reactions, the desired product was effectively separated from the fluorous pyridone by-product using a simple fluorous solid phase extraction. 相似文献
5.
Yasuhiko Iwasaki Keiko Shimakata Nobuyuki Morimoto Kimio Kurita 《Journal of polymer science. Part A, Polymer chemistry》2003,41(1):68-75
To obtain a hydrogel‐like elastic membrane, we prepared semi‐interpenetrating polymer networks (IPNs) by the radical polymerization of methacrylates such as 2‐methacryloyloxyethyl phosphorylcholine (MPC), 2‐hydroxyethylmethacrylate, and triethyleneglycol dimethacrylate diffused into segmented polyurethane (SPU) membranes swollen with a monomer mixture. The values of Young's modulus for the hydrated semi‐IPN membranes were less than that for an SPU membrane because of higher hydration, but they were much higher than that for a hydrated MPC polymer gel (non‐SPU). According to a thermal analysis, the MPC polymer influenced the segment association of SPU. The diffusion coefficient of 8‐anilino‐1‐naphthalenesulfonic acid sodium salt from the semi‐IPN membrane could be controlled with different MPC unit concentrations in the membrane, and it was about 7 × 102 times higher than that of the SPU membrane. Fibroblast cell adhesion on the semi‐IPN membrane was effectively reduced by the MPC units. We concluded that semi‐IPNs composed of the MPC polymer and SPU may be novel polymer materials possessing attractive mechanical, diffusive‐release, and nonbiofouling properties. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 68–75, 2003 相似文献
6.
Masakazu Muramatsu 《Mathematical Programming》1998,83(1-3):393-406
In this paper, we introduce an affine scaling algorithm for semidefinite programming (SDP), and give an example of a semidefinite
program such that the affine scaling algorithm converges to a non-optimal point. Both our program and its dual have interior
feasible solutions and unique optimal solutions which satisfy strict complementarity, and they are non-degenerate everywhere. 相似文献
7.
The Heat Kernel on Hyperbolic Space 总被引:1,自引:0,他引:1
The purpose of this note is to provide a new proof for the explicitformulas of the heat kernel on hyperbolic space. By definition,the hyperbolic space Hn is a (unique) simply connected completen-dimensional Riemannian manifold with a constant negative sectionalcurvature 1. 1991 Mathematics Subject Classification58G32, 58G11. 相似文献
8.
Kentaro Suzuki Taro Toyota Katsuhiko Sato Masakazu Iwasaka Shoogo Ueno Tadashi Sugawara 《Chemical physics letters》2007,440(4-6):286-290
Collagen-containing tubular giant vesicles (Col–tGVs) under a high static magnetic field were found to constitute characteristic curved structures (e.g. circular, 8-figure, and hairpin-loop), which were sustained by polymerization of collagen units inside the tGV. We ascribed the formation of these structures to the elasticity of the tGV and to the competing diamagnetic anisotropies between collagen and the tGV. These curved structures can be well expressed by the equation of elastica. 相似文献
9.
10.
K. Kawahta T. Tetsuka J. Fujita M. Nagatsu H. Ohnishi S. Okajima T. Iwasaki 《International Journal of Infrared and Millimeter Waves》1988,9(7):655-665
A 4-channel HCN laser scattering system has been developed and applied to the JIPP T-IIU tokamak. Main aim of this system is to study microturbulence excited in the plasma, especially in the high power ICRF heating experiment. The observed density fluctuations are in a frequency range of the electron diamagnetic drift wave and have broad frequency spectra. The main part of the wavenumber is found to satisfy the condition of
. In the heating experiments, deterioration of the energy confinement time is observed, and the density fluctuation level increases with the increase of the heating power. 相似文献