全文获取类型
收费全文 | 1441篇 |
免费 | 30篇 |
国内免费 | 8篇 |
专业分类
化学 | 1101篇 |
晶体学 | 23篇 |
力学 | 20篇 |
数学 | 91篇 |
物理学 | 244篇 |
出版年
2023年 | 6篇 |
2022年 | 5篇 |
2021年 | 6篇 |
2020年 | 14篇 |
2019年 | 25篇 |
2018年 | 18篇 |
2017年 | 13篇 |
2016年 | 26篇 |
2015年 | 30篇 |
2014年 | 34篇 |
2013年 | 86篇 |
2012年 | 84篇 |
2011年 | 88篇 |
2010年 | 46篇 |
2009年 | 65篇 |
2008年 | 79篇 |
2007年 | 78篇 |
2006年 | 79篇 |
2005年 | 81篇 |
2004年 | 92篇 |
2003年 | 84篇 |
2002年 | 70篇 |
2001年 | 24篇 |
2000年 | 19篇 |
1999年 | 15篇 |
1998年 | 21篇 |
1997年 | 22篇 |
1996年 | 23篇 |
1995年 | 14篇 |
1993年 | 8篇 |
1992年 | 9篇 |
1991年 | 16篇 |
1990年 | 14篇 |
1989年 | 13篇 |
1988年 | 8篇 |
1987年 | 14篇 |
1986年 | 6篇 |
1985年 | 22篇 |
1984年 | 10篇 |
1983年 | 8篇 |
1982年 | 6篇 |
1981年 | 12篇 |
1980年 | 10篇 |
1979年 | 5篇 |
1978年 | 7篇 |
1977年 | 11篇 |
1976年 | 8篇 |
1975年 | 6篇 |
1974年 | 6篇 |
1973年 | 9篇 |
排序方式: 共有1479条查询结果,搜索用时 15 毫秒
121.
122.
123.
Hitoshi Konno 《Czechoslovak Journal of Physics》2005,55(11):1455-1460
We give a level-2 representation of the elliptic algebra
in terms of one free boson and one free fermion. We show that
-modules have a natural direct sum decomposition into the irreducible (deformed) super-Virasoro modules associated with the
coset
.
Presented at the International Colloquium “Integrable Systems and Quantum Symmetries”, Prague, 16–18 June 2005. 相似文献
124.
The hydrothermal synthesis, single crystal X-ray structures and magnetic properties of two layered cobalt-carboxylate complexes, ∞2[CoII(O2C∗CH(OH)C6H5)2] (1) and ∞2[CoII(O2C∗CH(NH2)C6H5)2] (2), where O2CCH(OH)C6H5 is mandalate and O2CCH(NH2)C6H5 is phenylglycinate, are described. Pale pink crystals of 1 and 2 were obtained by the reaction of cobalt nitrate and the enantiomer-pure acids at 120 °C. In each case, the structure consists of stacks of quasi square-grid polymeric sheets consisting of carboxylato- bridges, M-O-C-O-M, and the presence of both d- and l-enantiomers of the ligands segregated on each face of the layer. The ligands exhibit both chelating and bridging functions with the carboxylate group adopting an anti-anti mode. The magnetic properties are characteristic of weakly interacting paramagnets where the moments are elevated by an important orbital contribution via spin-orbit coupling. 相似文献
125.
Karataev P Araki S Hamatsu R Hayano H Muto T Naumenko G Potylitsyn A Terunuma N Urakawa J 《Physical review letters》2004,93(24):244802
An experiment on the investigation of optical diffraction radiation (ODR) from a slit target as a possible tool for noninvasive electron beam-size diagnostics has been performed at the KEK accelerator test facility. The experimental setup has been installed at the diagnostics section of the extraction line. We have performed the first incoherent ODR observation from a slit target. The measured angular distributions are in reasonable agreement with the theoretical expectation. The beam-size effect onto the ODR angular pattern has been observed. Moreover, the sensitivity to the beam size as small as 14 microm has been achieved. 相似文献
126.
Hitoshi Watarai Hideaki Monjushiro Satoshi Tsukahara Masayori Suwa Yoshinori Iiguni 《Analytical sciences》2004,20(3):423-434
The recent development of new migration methods of micro-particles in liquids using various external fields is reviewed. The combination of a laser scattering force and a photothermal effect produced photothermal-conversion laser-photophoresis. A dielectric field generated in a planer or a capillary quadrupole electrode realized dielectrophoresis. Using a micrometer-scaled magnetic field gradient, the "Magnetophoretic velocimetry" of micro-particles was invented. Furthermore, the Lorentz force generated by combining an electric field and a magnetic field was utilized for electromagnetophoresis. These new methods were overlooked and the advantages in analytical use were discussed. 相似文献
127.
Ikeda S Sanuki R Miyachi H Miyashita H Taniguchi M Odashima K 《Journal of the American Chemical Society》2004,126(33):10331-10338
A Ni(0)/ZnCl(2) system effectively promotes the coupling of enones and alkene-tethered alkynes. In the reaction with 1,6-enynes, the oxidative cyclization of Ni(0) species on enones across the alkyne part followed by ZnCl(2)-promoted cleavage generates alkenylnickel intermediates. Subsequent migratory insertion of the tethered alkene occurs with 5-exo-cyclization. When the resulting sigma-alkylnickel intermediates have beta-hydrogen atoms, the reaction terminates by beta-hydrogen elimination to provide cyclopentane derivatives. On the other hand, a sigma-alkylnickel intermediate that does not have beta-hydrogen atoms undergoes the insertion of a second alkene unit to cause a domino effect via a three-fold C-C bond formation process with and without the cleavage of one C-C bond. 相似文献
128.
Development of a novel analytical method for determination of chondroitin sulfate using an in-capillary enzyme reaction 总被引:3,自引:0,他引:3
A novel analytical method for determination of total amount of chondroitin sulfate (CS) based on its conversion to desulfated chondro-disaccharide via an enzyme-catalyzed reaction, was developed. Using the in-capillary enzyme reaction, the method was also applied to the successful construction of an on-line analytical system. Within this system, electrophoretic migration was used to mix zones containing the enzyme mixture (chondroitinase ABC, chondro-4-sulfatase, chondro-6-sulfatase and 2-o-sulfatase) and the substrate (CS). The reaction was then allowed to proceed in the presence of a weak electric field and, finally, the product (desulfated chondro-disaccharide) of enzyme reaction migrated to the detector under the influence of an applied electric field. A polyvinyl alcohol-coated capillary was used to reduce protein adsorption. Desulfated chondro-disaccharide was successfully migrated toward the anode in 10 mM Tris-acetate buffer (pH 7.0) under reversed polarity and detected at 232 nm. The established method was validated and demonstrated to be applicable in the determination of total amount of CS in a commercial ophthalmic solution. No interference from the formulation excipients was observed. Good linearity was obtained, with correlation coefficients above 0.999. Recoveries and precisions ranged from 100.0 to 100.5%, and from 0.2 to 0.6% of the relative standard deviation, respectively. Good agreement was obtained between the established method and traditional photometric method based on carbazole reaction. In this study, application of the method to disaccharide compositional analysis was also performed. 相似文献
129.
In this article, we report successful preparation of dense [(Na0.5K0.5)1−xSrx](Nb1−xTix)O3 (x=0.005-0.100) ceramics by ordinary sintering in air. The dependence of phase structure on doping content of SrO and TiO2 has been determined by the X-ray diffraction technique. It was found that the crystal structure changed from orthorhombic to tetragonal at x≈0.040. Dielectric study revealed that the dielectric relaxor behavior was induced by doping of SrO and TiO2 into (Na0.5K0.5)NbO3. The samples in the composition range from x=0.005 to 0.020 exhibited excellent electrical properties, piezoelectric constant of electromechanical planar and thickness coupling coefficients of kp=26.6-32.5% and kt=39.8-43.8%. The results show that the [(Na0.5K0.5)1−xSrx](Nb1−xTix)O3 ceramics are one of the promising lead-free materials for electromechanical transducer applications. 相似文献
130.
By imaging the dark states that are due to coherent population trapping in Na atomic vapor, we have succeeded in depicting a spatially inhomogeneous magnetic field. Highly resolved dark lines represent cross sections of the surfaces of constant magnetic fields, and they agree well with the predicted hyperfine Zeeman splitting and the two-photon selection rules of the Na atom. Mapping was made two dimensionally in real time, but extension to three dimensions is straightforward. Furthermore, unlike the previous techniques based on optical pumping, this method can be used for any magnetic-field directions. 相似文献