全文获取类型
收费全文 | 851篇 |
免费 | 8篇 |
国内免费 | 65篇 |
专业分类
化学 | 399篇 |
晶体学 | 9篇 |
力学 | 28篇 |
综合类 | 1篇 |
数学 | 273篇 |
物理学 | 214篇 |
出版年
2023年 | 11篇 |
2022年 | 18篇 |
2021年 | 13篇 |
2020年 | 11篇 |
2019年 | 18篇 |
2018年 | 12篇 |
2017年 | 24篇 |
2016年 | 16篇 |
2015年 | 18篇 |
2014年 | 40篇 |
2013年 | 58篇 |
2012年 | 54篇 |
2011年 | 57篇 |
2010年 | 38篇 |
2009年 | 73篇 |
2008年 | 84篇 |
2007年 | 69篇 |
2006年 | 51篇 |
2005年 | 32篇 |
2004年 | 25篇 |
2003年 | 19篇 |
2002年 | 18篇 |
2001年 | 16篇 |
2000年 | 11篇 |
1999年 | 10篇 |
1998年 | 13篇 |
1997年 | 8篇 |
1996年 | 9篇 |
1995年 | 19篇 |
1994年 | 9篇 |
1993年 | 8篇 |
1992年 | 10篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 6篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1971年 | 1篇 |
排序方式: 共有924条查询结果,搜索用时 15 毫秒
31.
Pekka J. Korhonen Kari Silvennoinen Jyrki WalleniusAnssi Öörni 《European Journal of Operational Research》2012
We investigate in a simple bi-criteria experimental study, whether subjects are consistent with a linear value function while making binary choices. Many inconsistencies appeared in our experiment. However, the impact of inconsistencies on the linearity vs. non-linearity of the value function was minor. Moreover, a linear value function seems to predict choices for bi-criteria problems quite well. This ability to predict is independent of whether the value function is diagnosed linear or not. Inconsistencies in responses did not necessarily change the original diagnosis of the form of the value function. Our findings have implications for the design and development of decision support tools for Multiple Criteria Decision Making problems. 相似文献
32.
Induced twisted-grain-boundary phases in the binary mixtures of a cholesteric and a nematic compound
Thermodynamical, optical-texture and dielectric studies have been performed to study the phase diagram of the binary system of 5-cholesten-3β-ol-octanoate and 4-n-nonyloxybenzoic acid. It is observed that low concentrations of 5-cholesten-3β-ol-octanoate (2–30?mol?%) in 4-n-nonyloxybenzoic acid induce a mean-field phase diagram derived by Renn within the framework of the chiral Chen–Lubenski model. Various optical textures of the twisted-grain-boundary (TGB) phases under different conditions of molecular anchoring have been observed. Weak transitions related to the TGB phases have been detected by temperature dependent dielectric spectroscopy. 相似文献
33.
The non-equilibrium electron–positron–photon plasma thermalization process is studied using relativistic Boltzmann solver, taking into account quantum corrections both in non-relativistic and relativistic cases. Collision integrals are computed from exact QED matrix elements for all binary and triple interactions in the plasma. It is shown that in non-relativistic case (temperatures ) binary interaction rates dominate over triple ones, resulting in establishment of the kinetic equilibrium prior to final relaxation towards the thermal equilibrium, in agreement with the previous studies. On the contrary, in relativistic case (final temperatures ) triple interaction rates are fast enough to prevent the establishment of kinetic equilibrium. It is shown that thermalization process strongly depends on quantum degeneracy in initial state, but does not depend on plasma composition. 相似文献
34.
Burkhardt I. Wilke Mark H. Dornan Jon Yeung Christopher N. Boddy Atahualpa Pinto 《Tetrahedron letters》2014
Symmetric diols are useful compounds in the synthesis of natural products, their value often dependent on their successful monoprotection. A general and simple method for the monosilylation of symmetrical primary and secondary diols is reported. The method exploits the solubility differential of diols and their monosilylated counterparts in a binary hexanes/acetonitrile solvent system. 相似文献
35.
We study optical analogues of higher-order Dirac solitons (HODSs) in binary waveguide arrays. Like higher-order solitons obtained from the well-known nonlinear Schrödinger equation governing the pulse propagation in an optical fiber, these HODSs have amplitude profiles which are numerically shown to be periodic over large propagation distances. At the same time, HODSs possess some unique features. Firstly, the period of a HODS depends on its order parameter. Secondly, the discrete nature in binary waveguide arrays imposes the upper limit on the order parameter of HODSs. Thirdly, the order parameter of HODSs can vary continuously in a certain range. 相似文献
36.
Densities and speeds of sound of the (2,2,4-trimethylpentane + methylbenzene + butan-1-ol) ternary system as well as all its binary sub-systems were measured at four temperatures, namely 298.15 K, 308.15 K, 318.15 K, and 328.15 K at atmospheric pressure by a vibrating-tube densimeter DSA 5000. The binary (isooctane + toluene) system was studied previously. Excess quantities (molar volume, adiabatic compressibility, and isobaric thermal expansivity) of the mixtures studied were calculated from the experimental densities and speed of sounds. The excess molar volume data were correlated using the Redlich–Kister equation. Both the positive and S-shaped excess molar volume curves were found for the systems studied. The excess molar volumes versus concentration of binary systems differed in the shape and temperature dependence. The experimental binary data were compared with literature data. The experimental excess molar volumes were analyzed by means of the Extended Real Associated Solution (ERAS) model. The experimental data and the ERAS model can help to estimate real behaviour of the systems studied. 相似文献
37.
The problem of sorting by a genome rearrangement event asks for the minimum number of that event required to sort the elements of a given permutation. In this paper, we study a variant of the rearrangement event called prefix and suffix transreversal. A transreversal is an operation which reverses the first block before exchanging two adjacent blocks in a permutation. A prefix (suffix) transreversal always reverses and moves a prefix (suffix) of the permutation to another location. Interestingly, we will apply transreversal not on permutations but on strings over an alphabet of fixed size. We determine the minimum number of prefix and suffix transreversals required to sort the binary and ternary strings, with polynomial time algorithms for these sorting problems. 相似文献
38.
39.
《Physics letters. A》2020,384(22):126535
We consider the mass-imbalanced sensibility for the emergence of vortex patterns in the Bose-Einstein condensed binary mixture of rubidium-cesium (85Rb-133Cs), confined in quasi-two-dimensional harmonic traps, with one species linearly perturbed in one direction. Non-dipolar coupled species are chosen to highlight mass symmetry effects. We first analyze the condensed mixture in the unperturbed non-rotating regime, where radial phase separation is verified in the immiscible regime, which occurs for large ratio between inter- and intra-species repulsive interactions. By going to the linear perturbed regime, the radial phase separation that occurs in the immiscible condition splits up with the two densities having their maxima at distinct positions. In the rotating regime of both unperturbed and perturbed cases, the minimum rotation is determined in terms of the inter-species interaction to observe vortex structures. In the immiscible regime a dramatic spatial interchange between the species is verified by increasing the rotation. 相似文献
40.
基于图像处理的模拟尾流气泡幕研究 总被引:2,自引:1,他引:1
利用图像处理技术,对模拟的尾流气泡幕进行了定性和定量分析.压强较小时,位于不同层面上气泡的重叠少,通过二值图像处理可清楚地观察气泡的尺度大小及密度分布;而当压强较大时,不同层面气泡重叠幅度大,大部分气泡的边界难以判断,不能够得到气泡尺度参量及密度分布等信息.利用区域分割技术对获取的气泡幕灰度图像进行伪彩色显示,定性分析了气泡幕中气泡尺度、分布等信息.基于形状分析的等效直径、气泡幕剩余面积和剩余面积变化显示,不同压强下气泡的等效直径分布均在5~100像素范围,平均等效直径为55像素,压强较小条件下小气泡比例较大. 相似文献