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92.
Pattern formation and self-organization are phenomena that occur across the board, in animate and inanimate systems. In this paper, we rely on the constructal law to explain the generation of patterns (shapes, structures) in aggregates of organisms-pedestrian crowds and stony corals. In pedestrian crowds a variety of patterns are often observed, from ‘chaotic’ appearances to spontaneous organization in lanes of uniform walking direction. Stony corals and other organisms also present intraspecific variability in shape. We show that flow systems develop in time patterns which provide easier access to the nutrients and space, within a set of constraints imposed by each situation. Flow systems have the freedom to morph their shape in search for architectures that allows them to have greater access to the space that they inhabit. We identify the mechanisms allowing pedestrians to evolve in space and time. We also show that stony corals may develop branched or spherical shapes, depending on which shape performs best in response to the environmental conditions. The constructal law allows systems with complex internal flows to be described and understood for a unified view. 相似文献
93.
94.
We present a theoretical study of the collisions of atomic oxygen with O-precovered β-cristobalite (1 0 0) surface. We have constructed a multidimensional potential energy surface for the O2/β-cristobalite (1 0 0) system based mainly on a dense grid of density functional theory points by using the interpolation corrugation-reducing procedure. Classical trajectories have been computed for quasithermal (100–1500 K) and state-specific (e.g., collision energies between 0.01 and 4 eV) conditions of reactants for different O incident angles (θv). Atomic sticking and O2(adsorbed) formation are the main processes, although atomic reflection and Eley–Rideal (ER) reaction (i.e., O2 gas) are also significant, depending their reaction probabilities on the O incident angle. ER reaction is enhanced by temperature increase, with an activation energy derived from the atomic recombination coefficient (γO(θv = 0°, T)) equal to 0.24 ± 0.02 eV within the 500–1500 K range, in close agreement with experimental data. Calculated γO(θv = 0°, T) values compare quite well with available experimental γO(T) although a more accurate calculation is proposed. Chemical energy accommodation coefficient βO(T) is also discussed as a function of ER and other competitive contributions. 相似文献
95.
96.
The aim of this paper is to present a thorough reassessment of the Snyman–Fatti (SF) Multi-start Global Minimization Algorithm with Dynamic Search Trajectories, first published twenty years ago. The reassessment is done with reference to a slightly modified version of the original
method, the essentials of which are summarized here. Results of the performance of the current code on an extensive set of
standard test problems commonly in use today, are presented. This allows for a fair assessment to be made of the performance
of the SF algorithm relative to that of the popular Differential Evolution (DE) method, for which test results on the same
standard set of test problems used here for the SF algorithm, are also given. The tests show that the SF algorithm, that requires
relatively few parameter settings, is a reliably robust and competitive method compared to the DE method. The results also
indicate that the SF trajectory algorithm is particularly promising to solve minimum potential energy problems to determine
the structure of atomic and molecular clusters. 相似文献
97.
A nonlinear optimal impulsive control problem with trajectories of bounded variation subject to intermediate state constraints at a finite number on nonfixed instants of time is considered. Features of this problem are discussed from the viewpoint of the extension of the classical optimal control problem with the corresponding state constraints. A necessary optimality condition is formulated in the form of a smooth maximum principle; thorough comments are given, a short proof is presented, and examples are discussed. 相似文献
98.
文章运用Maple语言程序,在没有假设的条件下,得到了α螺旋蛋白质螺旋链运动模型方程组的行波精确解组,它涵盖了所有的耦合解组与非耦合解组,具有任意性.耦合解组的算例函数及其特性分析,解释了α螺旋蛋白质螺旋链运动模型的行波孤立子解的耦合效应,揭示了增加、稳定和控制蛋白质活性和功能的方向,文章的研究方法,为求解生物大分子螺旋链运动模型的行波精确解组探索了溪径. 相似文献
99.
We use a semiclassical approximation to study the transport through the weakly open chaotic Sinai quantum billiards which can be considered as the schematic of a Sinai mesoscopic device,with the diffractive scatterings at the lead openings taken into account.The conductance of the ballistic microstructure which displays universal fluctuations due to quantum interference of electrons can be calculated by Landauer formula as a function of the electron Fermi wave number,and the transmission amplitude can be expressed as the sum over all classical paths connecting the entrance and the exit leads.For the Sinai billiards,the path sum leads to an excellent numerical agreement between the peak positions of power spectrum of the transmission amplitude and the corresponding lengths of the classical trajectories,which demonstrates a good agreement between the quantum theory and the semiclassical theory. 相似文献
100.
通过探讨牵张力对甲状旁腺激素相关蛋白(Parathyroid hormone related protein,PTHrP)表达、分布的影响,为深入了解正畸牙齿移动过程的骨改建机理提供参考,本文使用体重200±20g、6~8W龄的健康雄性Wistar大鼠42只适应性喂养1W后随机分为7组,每组6只。选择每只大鼠的左侧上颌第一磨牙作为实验牙,以左侧上颌切牙作为支抗牙,安装正畸用0.012英寸(inch)步镍钛螺旋拉簧,力值为50g(0.49N)。分别于安装牙齿移动装置后1d、3d、5d、7d、14d、21d处死实验组大鼠,取含左侧上颌第一磨牙及其周围牙槽骨的组织块,常规进行HE染色和SABC法免疫组织化学染色。利用图像分析系统(0BI200高清晰度彩色病理图文分析系统),对每张免疫组化染色后的切片做定量分析。SPSS17.0建立数据库并进行统计学分析,显示在张力区牙周膜及牙槽骨组织中的成骨细胞、成纤维细胞以及间充质细胞PTHrP呈阳性表达,且张力区牙周组织中PTHrP的表达在加力第5天达到高峰。表明PTHrP牙周组织的改建有一定的调节作用,使张力区与压力区向不同的方向发展。 相似文献