全文获取类型
收费全文 | 2784篇 |
免费 | 71篇 |
国内免费 | 11篇 |
专业分类
化学 | 2102篇 |
晶体学 | 28篇 |
力学 | 40篇 |
数学 | 151篇 |
物理学 | 545篇 |
出版年
2022年 | 30篇 |
2021年 | 21篇 |
2020年 | 37篇 |
2019年 | 47篇 |
2018年 | 30篇 |
2017年 | 18篇 |
2016年 | 47篇 |
2015年 | 33篇 |
2014年 | 48篇 |
2013年 | 112篇 |
2012年 | 117篇 |
2011年 | 160篇 |
2010年 | 71篇 |
2009年 | 85篇 |
2008年 | 145篇 |
2007年 | 146篇 |
2006年 | 156篇 |
2005年 | 142篇 |
2004年 | 117篇 |
2003年 | 94篇 |
2002年 | 83篇 |
2001年 | 66篇 |
2000年 | 52篇 |
1999年 | 46篇 |
1998年 | 30篇 |
1997年 | 34篇 |
1996年 | 48篇 |
1995年 | 37篇 |
1994年 | 25篇 |
1993年 | 34篇 |
1992年 | 46篇 |
1991年 | 29篇 |
1990年 | 32篇 |
1989年 | 35篇 |
1988年 | 41篇 |
1987年 | 34篇 |
1986年 | 29篇 |
1985年 | 63篇 |
1984年 | 37篇 |
1983年 | 30篇 |
1982年 | 33篇 |
1981年 | 32篇 |
1980年 | 30篇 |
1979年 | 40篇 |
1978年 | 33篇 |
1977年 | 28篇 |
1976年 | 22篇 |
1975年 | 24篇 |
1974年 | 27篇 |
1973年 | 25篇 |
排序方式: 共有2866条查询结果,搜索用时 15 毫秒
51.
Hisami Yumoto Shigekazu Onozumi Yoshinori Kato Masatou Ishihara Kiyoshi Kishi 《Crystal Research and Technology》1996,31(2):159-164
Indium tin oxide (ITO) whiskers were grown by VLS (vapour-liquid-solid) mechanism, using the electron shower method. The whiskers were grown above 200 °C, and the deposition rate was above 0.6 nm/s. The electron shower controlled the size of the whiskers, and the size was 30 nm in diameter and 600 nm in length. The whiskers grew along the substrate at t < 300 s, but grew in a direction perpendicular to the substrate at t > 300 s. When the ITO whiskers grown along the substrate were used as NO2 gas sensor, the sensitivity was 340, and about 300 times higher than those of the whiskers grown in a direction perpendicular to the substrate and plate-like ITO crystallites. 相似文献
52.
To induce degradabilities in polymers in response to environmental conditions, endm odification reactions of poly(α-methylstyrene) (PMS) derivatives were carried out. 2-Phenylallyl halide derivatives such as 2-phenylallyl bromide, 2-(p-tolyl)allyl bromide, and α-trifluoromethylstyrene were found to be suitable end-modification agents. For example, the ω-2-phenylallyl-PMS derivative was prepared with almost quantitative functionality by the reaction of the living PMS derivative with 2-phenylallyl bromide. In a similar way, ω-3,3-difluoro-2-phenylallyl- and ω-2-(4-toly)allyl-PMS derivatives were synthesized. Based on thermogravimetric analysis, the onset of the degradation temperature of the endmodified PMS derivatives decreased in the following order: ω-hydrogen- > ω-3,3-difluoro-2-phenylallyl- > ω-2-phenylallyl- > ω-2-(p-tolyl)allyl-PMS. Actually, the onset temperature of ω-2-(p-tolyl)allyl-PMS derivatives was 50°C lower than that of ω-H-PMS derivatives. These results indicate that the active species is produced effectively at the endunsaturated bond, which initiates depolymerization of the polymer at rather low temperatures. Therefore, it is concluded that a 2-phenylallyl substituent at the end of the PMS chain induces effective degradation through a radical mechanism. 相似文献
53.
Tomohiro Takano Chutiparn Lertvachirapaiboon Yasuo Ohdaira Akira Baba Keizo Kato 《Molecular Crystals and Liquid Crystals》2019,685(1):93-99
AbstractGas sensing by using the transmission surface plasmon resonance (T-SPR) technique was demonstrated. Polyacrylic acid (PAA)/5-nm-thick gold/40-nm-thick silver/polycarbonate grating substrate structure (Sensor A) responded to ammonia; however, it exhibited a strong humidity dependence. Polyvinyl alcohol (PVA)/5-nm-thick gold/40-nm-thick silver/polycarbonate grating substrate structure (Sensor B) as the sensing material was also prepared and it mainly responded to humidity. The T-SPR properties of Sensors A and B were observed simultaneously by a stacking arrangement that enabled us to obtain the responses by using a single spectrophotometer. The ammonia concentration under various humidity conditions could be accurately obtained by simultaneous measurement of Sensors A and B. 相似文献
54.
The electronic states of the Cr overlayers on TiO2(0 0 1) surfaces have been investigated using angle-resolved and resonant photoemission spectroscopy with synchrotron radiation. At lower coverages, Cr deposition on TiO2(0 0 1) creates two well separated in-gap emissions due to the formation of surface Ti3+ (3d1) ions and Cr3+ (3d3) ions. At higher coverages, the in-gap emission is developed into the 2-peak-structure emission of Cr 3d character. The corresponding state is considered to be of metallic nature from the viewpoint of the high ability of oxygen adsorption, but has no Fermi edge, indicating a possibility of forming small Cr clusters on TiO2(0 0 1) at this stage. 相似文献
55.
Kando M Fukuda Y Pirozhkov AS Ma J Daito I Chen LM Esirkepov TZh Ogura K Homma T Hayashi Y Kotaki H Sagisaka A Mori M Koga JK Daido H Bulanov SV Kimura T Kato Y Tajima T 《Physical review letters》2007,99(13):135001
In a plasma wake wave generated by a high power laser, modulations of the electron density take the shape of paraboloidal dense shells, moving almost at the speed of light. A counterpropagating laser pulse is partially reflected from the shells, acting as relativistic flying mirrors, producing a time-compressed frequency-multiplied pulse due to the double Doppler effect. The counterpropagating laser pulse reflection from the plasma wake wave accompanied by its frequency multiplication (with a factor from 50 to 114) was detected in our experiment. 相似文献
56.
57.
The authors prove that the maximum norm of the vorticity controls the breakdown of smooth solutions of the 3-D Euler equations. In other words, if a solution of the Euler equations is initially smooth and loses its regularity at some later time, then the maximum vorticity necessarily grows without bound as the critical time approaches; equivalently, if the vorticity remains bounded, a smooth solution persists.Partially supported by O.N.R. Contract No. N00014-76-C-0316 and N.S.F. Grant No. MCS-81-01639Partially supported by N.S.F. Grant No. MCS-82-00171Partially supported by N.S.F. Grant No. MCS-81-02360 相似文献
58.
The effect of a geometrical relationship between a grain boundary (GB) plane and a tensile axis on intergranular fatigue cracking along 3(1 1 2) twin boundaries has been investigated in Fe-30%Cr alloy crystals. Fatigue experiments were carried out on the three kinds of the specimens containing the 3(1 1 2) twin boundary. It was found that the fatigue cracking behavior was sensitive to the geometry of the GB plane. In a specimen where both the GB plane and a slip vector lying in the GB plane in adjacent grains are inclined to the tensile axis at 45°, the fatigue cracks were nucleated preferentially along the twin boundary at a stress amplitude of 170 MPa. The specimen with the GB plane normal to the tensile axis showed that the fatigue crack was initiated from a slip band formed within a constituent grain at a stress amplitude of 300 MPa. When the GB plane was inclined to the tensile axis but the slip vector lying in the GB plane was normal to the tensile axis, development of additional slips formed perpendicular to the GB plane were observed at a specific site of the GB. Initiation of intergranular fatigue cracks at the site was recognized at a stress amplitude of 250 MPa. It can be suggested that the GB plane normal to the tensile axis provides the highest fatigue performance among them. The difference in the cracking property among these specimens could be understood in terms of the effective Schmid factor derived from elastically incompatible stress. 相似文献
59.
60.
Tosio Kato 《纯数学与应用数学通讯》1980,33(4):501-505
We prove that any nontrivial solution of certain nonlinear hyperbolic partial differential equations of second order blows up in a finite time if the initial data are localized, the initial velocity being on the average non-negative. 相似文献