全文获取类型
收费全文 | 2640篇 |
免费 | 71篇 |
国内免费 | 4篇 |
专业分类
化学 | 1423篇 |
晶体学 | 42篇 |
力学 | 119篇 |
数学 | 527篇 |
物理学 | 604篇 |
出版年
2023年 | 25篇 |
2022年 | 31篇 |
2021年 | 32篇 |
2020年 | 55篇 |
2019年 | 60篇 |
2018年 | 75篇 |
2017年 | 60篇 |
2016年 | 127篇 |
2015年 | 76篇 |
2014年 | 105篇 |
2013年 | 323篇 |
2012年 | 110篇 |
2011年 | 113篇 |
2010年 | 102篇 |
2009年 | 97篇 |
2008年 | 91篇 |
2007年 | 88篇 |
2006年 | 91篇 |
2005年 | 46篇 |
2004年 | 67篇 |
2003年 | 34篇 |
2002年 | 46篇 |
2001年 | 44篇 |
2000年 | 37篇 |
1999年 | 48篇 |
1998年 | 40篇 |
1997年 | 37篇 |
1996年 | 27篇 |
1995年 | 31篇 |
1994年 | 38篇 |
1993年 | 29篇 |
1992年 | 19篇 |
1991年 | 19篇 |
1990年 | 23篇 |
1989年 | 16篇 |
1988年 | 22篇 |
1986年 | 26篇 |
1985年 | 25篇 |
1984年 | 18篇 |
1983年 | 22篇 |
1982年 | 15篇 |
1981年 | 21篇 |
1980年 | 18篇 |
1979年 | 21篇 |
1978年 | 15篇 |
1977年 | 17篇 |
1976年 | 12篇 |
1975年 | 23篇 |
1974年 | 15篇 |
1965年 | 15篇 |
排序方式: 共有2715条查询结果,搜索用时 15 毫秒
21.
The NMR enhancement factor of a frozenCuMn spin glass has been measured at a temperatureT?T g /5. The measurements were performed as function of static magnetic fields of different directions. A two component model of a spin glass has been outlined. One component being a “system of single spins” and the other one being a “subsystem of clusters”. Both components were attributed to different kinds of interaction being RKKY and dipole interaction respectively. The effective anisotropy field of the single spin system consists of two unidirectional contributionsH a s andH a c , which have been measured for different conditions. A second anisotropy fieldH d binds the cluster system to the system of single spins. All anisotropy fields depend on the annealing temperature of the alloys. 相似文献
22.
H. C. Öttinger 《Colloid and polymer science》1987,265(2):101-105
The idea of consistently averaging the hydrodynamic interaction and its various consequences for Hookean dumbbells are reviewed. For long chains this idea can be used to generalize the Rouse-Zimm model for polymer solutions. Unlike the usual Rouse-Zimm model, the new model for steady shear flow predicts a nonzero second normal stress coefficient and shear rate dependent material functions. In the limit of long chains, the viscosity and the normal stress coefficients are universal functions of the reduced shear rate.This paper was presented at the Frühjahrstagung des Fachausschusses Polymerphysik der Deutschen Physikalischen Gesellschaft at Kaiserslautern (West Germany), March 12–14, 1986. 相似文献
23.
Zusammenfassung Ein Gemisch von-Naphthylisocyanat mit etwa 6 1,4-Diazabicyklo-[2,2,2]-oktan (10–15 ml) reagiert quantitativ und sofort mit mg-Mengen Wasser unter Bildung von Kohlendioxid, das anschließend automatisch titriert wird. Wassermengen von etwa 0,3–3 mg lassen sich in etwa 8 min mit einer Standardabweichung von 0,8% rel. bestimmen.
The automatic determination of carbon and hydrogen. IV
Summary A mixture of about 10–15 ml of-naphthylisocyanate with about 6%. 1,4-diazabicyclo [2,2,2]-octane reacts instantaneously and quantitatively with water in mg quantities. The resulting carbon dioxide is automatically titrated. Amounts of water of about 0.3–3 mg were determined within 8 min. with a standard deviation of 0.8% rel.相似文献
24.
25.
This preliminary study describes the concentration of radionuclides 238U, 232Th, 40K, and 226Ra in Afin-Elbistan lignite samples which are primarily used for power generation in the Afin-Elbistan Coal-Fired Power Plant. The results show that the concentration of 238U is higher in the Afin-Elbistan lignite compared to various world coals whereas the opposite is observed with 232Th and 40K. 相似文献
26.
27.
B. Saatçi M. Ari M. Gündüz S. Türktekin F. Meydaneri S. Durmuş M. Özdemir 《Continuum Mechanics and Thermodynamics》2013,25(6):739-748
In this work, the structural and transport properties of Mg-doped Sn-based alloys have been investigated. The temperature-dependent transport and structural properties of Sn–Mg alloys were investigated for five different samples (Pure Sn, Sn-1.0 wt% Mg, Sn-2.0 wt% Mg, Sn-6.0 wt% Mg and Pure Mg). Scanning electron microscopy (SEM), X-ray diffraction and energy dispersive X-ray analysis measurements were carried out in order to clarify the structural properties of the samples. It was found that the samples had tetragonal crystal symmetry, except for pure Mg which had hexagonal crystal symmetry. We also found that the cell parameters changed slightly with the addition of Mg element. The SEM micrographs of the samples showed that they had smooth surfaces with a clear grain boundary. The electrical and thermal conductivity of the samples were measured by four-point probe and the radial heat flow method, respectively. The electrical resistivity of the samples increased almost linearly with the increasing temperature. The thermal conductivity values ranged between 0.60 and 1.00 W/Km, while they decreased slightly with temperature and increased with Mg composition. The thermal conductivity values of the alloys were in between the values of pure Sn and Mg. The thermal conductivity results of the alloys were compared with other available results, and a good agreement was seen between the results. In addition, the temperature coefficients of electrical resistivity and thermal conductivity were determined; these were independent of the composition of the alloying elements. 相似文献
28.
Özlem Yeşiltaş 《Central European Journal of Physics》2013,11(12):1674-1679
In this paper, we have provided a matrix Hamiltonian model for honeycomb lattices and subsequently obtained the dispersion relation. Furthermore, we have constructed the C operator for the given non-Hermitian Hamiltonian model. The quadratic surfaces are sketched and the quantum Brachistochrone problem is discussed for the given honeycomb lattice model. 相似文献
29.
30.
Dr. Cemal Albayrak Gözde Barım Prof. Ömer Dag 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(44):15026-15035
Hydrated CaCl2, LiI, and MgCl2 salts induce self‐assembly in nonionic surfactants (such as C12H25(OCH2CH2)10OH) to form lyotropic liquid‐crystalline (LLC) mesophases that undergo a phase transition to a new type of soft mesocrystal (SMC) under ambient conditions. The SMC samples can be obtained by aging the LLC samples, which were prepared as thin films by spin‐coating, dip‐coating, or drop‐casting of a clear homogenized solution of water, salt, and surfactant over a substrate surface. The LLC mesophase exists up to a salt/surfactant mole ratio of 8, 10, and 4 (corresponding to 59, 68, and 40 wt % salt/surfactant) in the CaCl2, LiI, and MgCl2 mesophases, respectively. The SMC phase can transform back to a LLC mesophase at a higher relative humidity. The phase transformations have been monitored using powder X‐ray diffraction (PXRD), polarized optical microscopy (POM), and FTIR techniques. The LLC mesophases only diffract at small angles, but the SMCs diffract at both small and wide angles. The broad surfactant features in the FTIR spectra of the LLC mesophases become sharp and well resolved upon SMC formation. The unit cell of the mesophases expands upon SMC transformation, in which the expansion is largest in the MgCl2 and smallest in the CaCl2 systems. The POM images of the SMCs display birefringent textures with well‐defined edges, similar to crystals. However, the surface of the crystals is highly patterned, like buckling patterns, which indicates that these crystals are quite soft. This unusual phase behavior could be beneficial in designing new soft materials in the fields of phase‐changing materials and mesostructured materials, and it demonstrates the richness of the phase behavior in the salt–surfactant mesophases. 相似文献