全文获取类型
收费全文 | 3381篇 |
免费 | 72篇 |
国内免费 | 22篇 |
专业分类
化学 | 2571篇 |
晶体学 | 46篇 |
力学 | 40篇 |
数学 | 212篇 |
物理学 | 606篇 |
出版年
2022年 | 19篇 |
2020年 | 26篇 |
2019年 | 64篇 |
2018年 | 23篇 |
2017年 | 25篇 |
2016年 | 54篇 |
2015年 | 39篇 |
2014年 | 45篇 |
2013年 | 188篇 |
2012年 | 160篇 |
2011年 | 175篇 |
2010年 | 89篇 |
2009年 | 107篇 |
2008年 | 174篇 |
2007年 | 182篇 |
2006年 | 189篇 |
2005年 | 162篇 |
2004年 | 114篇 |
2003年 | 132篇 |
2002年 | 143篇 |
2001年 | 68篇 |
2000年 | 61篇 |
1999年 | 36篇 |
1998年 | 45篇 |
1997年 | 37篇 |
1996年 | 40篇 |
1995年 | 28篇 |
1994年 | 33篇 |
1993年 | 37篇 |
1992年 | 42篇 |
1991年 | 33篇 |
1990年 | 49篇 |
1989年 | 34篇 |
1988年 | 45篇 |
1987年 | 28篇 |
1986年 | 42篇 |
1985年 | 46篇 |
1984年 | 55篇 |
1983年 | 43篇 |
1982年 | 54篇 |
1981年 | 50篇 |
1980年 | 40篇 |
1979年 | 48篇 |
1978年 | 49篇 |
1977年 | 44篇 |
1976年 | 32篇 |
1975年 | 35篇 |
1974年 | 34篇 |
1973年 | 31篇 |
1972年 | 18篇 |
排序方式: 共有3475条查询结果,搜索用时 0 毫秒
81.
82.
Atsuo Yasumori Hiroshi Matsumoto Shigeo Hayashi Kiyoshi Okada 《Journal of Sol-Gel Science and Technology》2000,18(3):249-258
The magnetic composite materials that consist of transparent matrix and magnetic fine particles are expected to have large residual magnetization and coercive force because of their fine magnetic domain structure, and also to show magneto-optical effects. Silica gels containing magnetite (Fe3O4) fine particles were prepared by sol-gel method. The magnetic, optical and magneto-optical properties of the composites were investigated by measurements of magnetization curves, UV-visible spectra and Faraday rotation in visible range. The saturation magnetization of the composite was almost as same as that expected from the amount of magnetite fine particles in it. Although the composites had large and broad absorption at around 400 nm, they still maintained their transparency. The origins of decrement of transparency attributed to the optical absorption of magnetite and scattering due to magnetite fine particles. The whole composites showed positive Faraday rotation under external static magnetic field due to the large contribution of diamagnetic silica gel matrix. Magnetite contributed negative Faraday rotation with maximum at around 470–480 nm to the magneto-optical spectra of the composites. 相似文献
83.
Two-dimensional infrared photon echo and pump probe studies of the OH stretch vibration provide a sensitive probe of the correlations and couplings in the hydrogen bond network of liquid water. The nonlinear response is simulated using numerical integration of the Schrodinger equation with a Hamiltonian constructed to explicitly treat intermolecular coupling and nonadiabatic effects in the highly disordered singly and doubly excited vibrational exciton manifolds. The simulated two-dimensional spectra are in close agreement with our recent experimental results. The high sensitivity of the OH stretch vibration to the bath dynamics is found to arise from intramolecular mixing between states in the two-dimensional anharmonic OH stretch potential. Surprisingly small intermolecular couplings reproduce the experimentally observed intermolecular energy transfer times. 相似文献
84.
Norio Shibata Banibrata Das Masamichi Hayashi Shuichi Nakamura Takeshi Toru 《Journal of fluorine chemistry》2009,130(12):1164-1170
Synthesis of 1,3-butadiyne-bridged perfluoroisopropyl binuclear phthalocyanine 2 has been successfully achieved from unsymmetrical A3B-type iodo-perfluoroisopropyl phthalocyanine by palladium-catalyzed cross-coupling with trimethylsilylacetylene and copper-catalyzed Glaser homo-coupling as key reactions. The dyad 2 essentially remains non-aggregated irrespective of solvent and concentration. Electrochemical analysis suggests oxidation is not possible whereas the molecule is more easily reduced. All the results are advantages for photodynamic therapy (PDT). 相似文献
85.
H. Tsuchiya M. Sato H. Hayashi H. Kato H. Kureshiro T. Hayashi 《Chromatographia》1996,43(7-8):419-425
Summary Reversed-phase ion-pair HPLC with fluorimetric detectors connected in series was studied for the simultaneous determination of two tetrahydro--carbolines and two -carbolines. After additon of internal standards the samples were reacted with fluorescamine, and then subjected to serial extractions to remove their precursor (tryptamine) from the analytical system. This treatment not only suppressed the artefactual formation of tetrahydro--carbolines and -carbolines during analysis, but also effectively purified them. Under optimum conditions, using trifluoroacetic acid as counter ion, all analytes were separated within 14 min and without major interfering peaks. The quantitative ranges were 0.25–80.0 ng mL–1 for both tetrahydro--carbolines and 0.1–30.0 ng mL–1 for both -carbolines. Replicate spiking experiments showed that recovery from most of the samples tested was over 90% and the relative standard deviation ranged from 0.7 to 10.4% within and between assays. The proposed method was applicable to various materials such as soy sauce, vinegar, ketchup, tabasco, beer, wine, sake, whisky, brandy, cows' milk, coffee, cocoa, cheese, cigarette smoke and urine. 相似文献
86.
Behrends R Fuchs K Kaatze U Hayashi Y Feldman Y 《The Journal of chemical physics》2006,124(14):144512
At six temperatures T between 10 and 50 degrees C and at mole fractions x(g) of glycerol (0相似文献
87.
Retro-allylation of homoallyl alcohol by rhodium catalysis occurs to generate allylrhodium species. This allylrhodium reacts with aldehydes to give the corresponding secondary alcohols in situ. Isomerization of these alcohols proceeds in the same pots to furnish the corresponding saturated ketones in good yields. [reaction: see text] 相似文献
88.
89.
To prepare powdered medicines without bitter taste, film coating is required to cover the surface of core particles. In this study, effect of formulation and operating conditions of agitation fluidized bed on the core particle properties was investigated. In order to prevent breakage of the core particles during coating process, which sometimes causes variation of drug dissolution rate, addition of maltose syrup powder during the formulation process of the core particles was investigated. Also, a method for friability test in which the core particles were subjected to strong impact was proposed to evaluate strength of the core particles. The friability of the core particles determined by this test method correlated well with the actual friability of the particles during the coating process. Based on this result, we confirmed this novel friability test method could predict the core particle endurance during the coating process. 相似文献
90.
Efficient monocyclic 1,2-diazepine formation via a tandem electrocyclization reaction of cyclobutenones with lithiodiazoacetate is demonstrated. The reaction proceeds through an oxy anion-accelerated 4π-ring opening of cyclobutene followed by an 8π-ring closure of the resultant oxy anion-substituted diazo-diene under mild conditions to furnish a 1,2-diazepine via formal diazomethylene insertion into the C-C bond of cyclobutenone. 相似文献