全文获取类型
收费全文 | 202723篇 |
免费 | 2279篇 |
国内免费 | 504篇 |
专业分类
化学 | 111083篇 |
晶体学 | 3653篇 |
力学 | 8007篇 |
综合类 | 11篇 |
数学 | 19211篇 |
物理学 | 63541篇 |
出版年
2020年 | 1736篇 |
2019年 | 1935篇 |
2018年 | 2248篇 |
2017年 | 2364篇 |
2016年 | 3539篇 |
2015年 | 2206篇 |
2014年 | 3557篇 |
2013年 | 9106篇 |
2012年 | 6556篇 |
2011年 | 8056篇 |
2010年 | 5723篇 |
2009年 | 5676篇 |
2008年 | 7186篇 |
2007年 | 7101篇 |
2006年 | 6738篇 |
2005年 | 6097篇 |
2004年 | 5554篇 |
2003年 | 5122篇 |
2002年 | 4882篇 |
2001年 | 6157篇 |
2000年 | 4638篇 |
1999年 | 3529篇 |
1998年 | 2753篇 |
1997年 | 2711篇 |
1996年 | 2601篇 |
1995年 | 2444篇 |
1994年 | 2340篇 |
1993年 | 2174篇 |
1992年 | 2839篇 |
1991年 | 2738篇 |
1990年 | 2678篇 |
1989年 | 2698篇 |
1988年 | 2718篇 |
1987年 | 2728篇 |
1986年 | 2597篇 |
1985年 | 3309篇 |
1984年 | 3326篇 |
1983年 | 2601篇 |
1982年 | 2718篇 |
1981年 | 2769篇 |
1980年 | 2549篇 |
1979年 | 2884篇 |
1978年 | 2875篇 |
1977年 | 2993篇 |
1976年 | 2825篇 |
1975年 | 2563篇 |
1974年 | 2514篇 |
1973年 | 2470篇 |
1972年 | 1705篇 |
1968年 | 1707篇 |
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
971.
F. M. Tukhtaboeva K. S. Davronov I. Zh. Kurbonbaev K. K. Kuchkarov 《Chemistry of Natural Compounds》2006,42(4):477-478
The protein composition of seeds treated with a suspension of ultradisperse iron was studied using electrophoresis on PAAG.
Changes were noted in the fractions with relative electrophoretic mobility (REM) 0.11 of water-soluble and REM 0.37 of buffer-soluble
An-9 cotton seed proteins.
__________
Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 384–385, July–August, 2006. 相似文献
972.
Half-lives of the 2νββ decay are calculated in the proton-neutron QRPA for76Ge,82Se,100Mo,128,130Te,136Xe and150Nd. The strength of the particle-particle interaction, which plays a decisive role for a reliable evaluation of the half-lives, is determined from a QRPA calculation of singleβ + decays. The 2ν decay rates calculated with the interaction strength fitted in this way are strongly suppressed and found to be consistent with the existing experimental data. Effects of the ground-state correlations on the suppression are investigated. On the other hand, the present calculation indicates limitations of the QRPA approach. 相似文献
973.
Oil migration in filled chocolates limits shelf life due to texture changes and loss of visual appeal. Spatial and temporal
oil concentration changes of a two-layer chocolate and peanut butter filling system, which models a filled chocolate, were
monitored by magnetic resonance imaging. Formulations of chocolate varied with respect to particle size, milk fat content
and emulsifier level. Sorption-time experimental data was used to establish the best fit diffusion coefficient for a Fickian
diffusion model. On the basis of the comparison of spatial experimental data to the model, Fickian diffusion alone does not
account for oil migration.
Authors' address: Michael J. McCarthy, Department of Food Science and Technology, University of California, One Shields Avenue,
Davis, CA 95616, USA 相似文献
974.
The structure of Y2Rh3Ge has been determined and refined from single-crystal X-ray diffraction data (R = 0.042). It is a rhombohedral, ternary, ordered variant of the cubic Laves structure type MgCu2, with space group
and c = 11.82(1)Å for the triple hexagonal cell. The c/a ratio (2.13) is significantly lower than the value for the triple hexagonal cell of the cubic lattice of the parent structure type (2.45), resulting in shorter distances between Rh and Ge atoms than between Rh atoms. The isotypy of Pr2Rh3Si, Er2Rh3Si, Pr2Rh3Ge, and Er2Rh3Ge has been established from Guinier films. The Y2Rh3Ge structure is compared with the binary compound YRh2, crystallizing with the MgCu2 structure, and with three other simple, ternary, ordered substitution derivatives of the Laves phase types MgZn2 and MgCu2. 相似文献
975.
On the basis of the model “polymer chain in an array of obstacles” the influence of the topology effects on the dynamics of concentrated polymer systems is investigated theoretically. The 1/z-expansion (where z is the coordinational number of the lattice of obstacles) is proposed for this problem. By means of this expansion the diffusion coefficient of a linear unclosed polymer chain is calculated. The equilibrium properties of linear closed chain (i.e. ring) unentangled with either of the edges of the lattice are investigated in detail. In particular, it is shown that the diffusion coefficient D of the center of mass of closed chain consisting of N links is proportional to N−5/2. 相似文献
976.
S. Sarkar A. D. Thakur C. V. Tomy G. Balakrishnan D. McK Paul S. Ramakrishnan A. K. Grover 《Pramana》2006,66(1):193-207
New experimental data are presented on the scan rate dependence of the magnetization hysteresis width ΔM(H) (∞ critical current densityJ
c(H)) in isothermalMH scans in a weakly pinned single crystal of Ca3Rh4Sn13, which displays second magnetization peak (SMP) anomaly as distinct from the peak effect (PE). We observe an interesting
modulation in the field dependence of a parameter which purports to measure the dynamical annealing of the disordered bundles
of vortices injected through the sample edges towards the destined equilibrium vortex state at a givenH. These data, in conjunction with the earlier observations made while studying the thermomagnetic history dependence inJ
c(H) in the tracing of the minor hysteresis loops, imply that the partially disordered state heals towards the more ordered state
between the peak field of the SMP anomaly and the onset field of the PE. The vortex phase diagram in the given crystal of
Ca3Rh4Sn13 has been updated in the context of the notion of the phase coexistence of the ordered and disordered regions between the
onset field of the SMP anomaly and the spinodal line located just prior to the irreversibility line. A multi-critical point
and a critical point in the (H,T) region of the Bragg glass phase have been marked in this phase diagram and the observed behavior is discussed in the light
of recent data on multi-critical point in the vortex phase diagram in a single crystal of Nb. 相似文献
977.
Iron oxide catalyst with spinel structure used for dehydrogenation of ethylbenzene is one kind of important catalyst in petrochemical industry. In this work several series of industrial catalyst were prepared with different components and different manufacturing processes. Mössbauer Spectroscopy has been used to determine the optimal components and the better manufacturing process for spinel structure formation. The results may prove useful for producing the industrial dehydrogenation catalyst with better catalytic property. 相似文献
978.
979.
Solid solutions of CsCl-Br in five different concentrations were prepared in sealed quartz tubes by heating the mixture to
1123°K for 6–8 hr and quenching to room temperature. X-ray diffractograms were taken at eight different temperatures between
room temperature and 90°K for these solid solutions using the YPC50NM powder diffractometer and a continuous flow cryostat.
The observed lattice parameters for each sample at each temperature obtained from the powder diffractograms were then extrapolated
to give the true lattice parameters using the least square method with Nelson-Riley extrapolation scheme. The values of the
true lattice parameters at each concentration and at each temperature were tabulated and the results discussed. It is shown
that the lattice parameters vs temperature for some concentrations exhibit an anomalous behaviour.
Contribution No. 691 相似文献
980.
The use of multigrid methods in complex fluid flow problems is still under development. In this paper a full multigrid procedure has been incorporated in a finite volume solution for predicting fully developed fluid flow in a streamwise periodic geometry. Steady computations in two-dimensional body fitted co-ordinates have shown considerable savings in computation time by this multigrid method. 相似文献