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1.
The microscopic mechanisms of ion hydration and ion selectivity in biomolecular systems are long-standing research topics,in which the difficulty is how to reasonably and accurately describe the ion-water and ion-biomolecule interactions.This paper summarizes the development and applications of the atom-bond electronegativity equalization fluctuating charge force field model,ABEEM/MM,in the investigations of ion hydration,metalloproteins and ion-DNA bases systems.Based on high-level quantum chemistry calculations,the parameters were optimized and the molecular potential functions were constructed and applied to studies of structures,activities,energetics,and thermodynamic and kinetic properties of these ion-containing systems.The results show that the performance of ABEEM/MM is generally better than that of the common force fields,and its accuracy can reach or approach that of the high-level ab initio MP2 method.These studies provide a solid basis for further investigations of ion selectivity in biomolecular systems,the structures and properties of metalloproteins and other related ion-containing systems.  相似文献   
2.
The amino acid ionic liquids(AAILs) [C3mim][Gly](1-propyl-3-methylimidazolium glycine) and [C4mim][Gly](1-butyl-3methylimidazolium glycine) have been prepared by the neutralization method and characterized by 1 H NMR spectroscopy and differential scanning calorimetry(DSC).The values of their density,surface tension and refractive index were measured at(298.15 ± 0.05) K.Since the AAILs can form strong hydrogen bonds with water,small amounts of water are difficult to remove from the AAILs by common methods.In order to eliminate the effect of the impurity water,the standard addition method(SAM) was applied to these measurements.A new concept which is called the ionic parachor has been put forward.The [C n mim] + cations were treated as a group of reference ions and the individual values of their ionic parachor were evaluated in terms of an extrathermodynamic assumption.Then,using the values of the ionic parachor of reference ions,the parachor,surface tension γ and refractive index n D of the ionic liquids investigated in this work were estimated.The estimated values correlate quite well with the corresponding experimental values.  相似文献   
3.
Love’s first approximation theory is used to analyze the natural frequencies of rotating functionally graded cylindrical shells.To verify the validity of the present method,the natural frequencies of the simply supported non-rotating isotropic cylindrical shell and the functionally graded cylindrical shell are compared with available published results.Good agreement is obtained.The effects of the power law index,the wave numbers along the x-and θ-directions,and the thickness-to-radius ratio on the natural frequencies of the simply supported rotating functionally graded cylindrical shell are investigated by several numerical examples.It is found that the fundamental frequencies of the backward waves increase with the increasing rotating speed,the fundamental frequencies of the forward waves decrease with the increasing rotating speed,and the forward and backward waves frequencies increase with the increasing thickness-to-radius ratio.  相似文献   
4.
In this paper, the dynamic surface control (DSC) algorithm is proposed for a class of stochastic nonlinear systems with nonminimum phase and the standard output-feedback form. The proposed algorithm is a stochastic vision by combining the traditional back-stepping together with the DSC technique, which can overcome the problem of ‘explosion of complexity’ in the back-stepping designing procedure for the stochastic nonlinear systems. Thus, it can reduce the computation complexity and is easy to be used in the actual implementation. It is shown that all the signals of the resulting closed-loop system are uniformly ultimately bounded.  相似文献   
5.
This paper is concerned with the fault detection filter design problem for a class of discrete-time switched systems whose output can track a time-varying and known frequency region reference input under arbitrary switchings. Faults detection filters are designed to guarantee that the disturbance attenuation performance is satisfied for all subsystems, the reference input attenuation performance is satisfied for the fault-free case, meanwhile, the reference input sensitivity performance is satisfied for the fault cases. With the aid of virtue of the frequency of the reference input in the finite-frequency region which is known beforehand, the finite-frequency H ? performance for switched systems is firstly defined. Sufficient conditions for the fault detection filter are given in terms of solutions to a set of linear matrix inequalities, furthermore, the filter gains are characterized in terms of the solution of a convex optimization problem. A numerical example is used to demonstrate the effectiveness of the proposed design method.  相似文献   
6.
泥岩三轴蠕变实验研究   总被引:1,自引:0,他引:1  
张向东  傅强 《应用力学学报》2012,29(2):154-158,238
采用MTS伺服刚性压力实验机对高家梁煤矿泥岩进行了三轴蠕变实验研究,获得了泥岩在不同应力条件下的蠕变变形规律。实验表明围压对泥岩微观缺陷的发展有一定的限制作用。随着围压的增加,泥岩的三轴抗压强度和弹性模量均有所增加。在围压一定时:衰减蠕变量随轴压的增大而增大;衰减蠕变率随偏应力的增加而增大;稳态蠕变率随偏应力的增大而增大。在偏应力一定时,稳态蠕变率随围压的增大而减小。当围压大于4MPa后,围压的限制作用将明显减小。随着围压继续增大,稳态蠕变率变化并不明显。根据获得的实验数据,用回归法求出了H-K模型蠕变方程的参数。结果表明H-K模型能较好地模拟实验结果。在实际工程中可通过支护增加围压以提高围岩屈服强度,也可根据实际工程中泥岩蠕变的变化趋势确定合理的二次支护时间,避免流变破坏的发生。  相似文献   
7.
利用球磨法将具有纤维束结构的一维纳米凹凸棒石粉体进行亚微米颗粒化改造.将亚微米颗粒化凹凸棒石粉体分散在长城牌柴油机润滑油CD 15W/40中,利用端面摩擦磨损试验和环-块摩擦磨损试验考察其减摩与自修复性能,并与未添加凹凸棒石粉体的CD 15W/40进行对比.借助XRD、SEM、TEM、EDX和XPS对试验样品进行了分析测试,并探讨了亚微米颗粒化凹凸棒石粉体对45#钢磨损表面的自修复机理.结果表明:高能球磨可以完成将纤维状的凹凸棒石粉体向颗粒状转变的过程,改造后的粉体物相组成为凹凸棒石和石英,粒度属于亚微米级;CD15W/40添加亚微米颗粒化凹凸棒石粉体后,其减摩性提升58.4%;与CD 15W/40润滑表面相比,加入亚微米颗粒化凹凸棒石粉体后,磨损表面光滑,没有明显犁沟、点蚀坑和表面材料塑性变形等现象;磨痕处存在与基体材料不同的修复区域,该修复区域沉积了O、Si、Fe等元素,说明亚微米颗粒化凹凸棒石粉体对45#钢具有优良的减摩性和自修复性能.  相似文献   
8.
The existence of solution for the 2D-Keller-Segel system in the subcritical case, i.e. when the initial mass is less than 8π, is reproved. Instead of using the entropy in the free energy and free energy dissipation, which was used in the proofs (Blanchet et al. in SIAM J. Numer. Anal. 46:691–721, 2008; Electron. J. Differ. Equ. Conf. 44:32, 2006 (electronic)), the potential energy term is fully utilized by adapting Delort’s theory on 2D incompressible Euler equation (Delort in J. Am. Math. Soc. 4:553–386, 1991).  相似文献   
9.
This paper describes a higher-order global-local theory for thermal/mechanical response of moderately thick laminated composites with general lamination configurations. In-plane displacement fields are constructed by superimposing the third-order local displacement field to the global cubic displacement field. To eliminate layer-dependent variables, interlaminar shear stress compatibility conditions have been employed, so that the number of variables involved in the proposed model is independent of the number of layers of laminates. Imposing shear stress free condition at the top and the bottom surfaces, derivatives of transverse displacement are eliminated from the displacement field, so that C0 interpolation functions are only required for the finite element implementation. To assess the proposed model, the quadratic six-node C0 triangular element is employed for the interpolation of all the displacement parameters defined at each nodal point on the composite plate. Comparing to various existing laminated plate models, it is found that simple C0 finite elements with non-zero normal strain could produce more accurate displacement and stresses for thick multilayer composite plates subjected to thermal and mechanical loads. Finally, it is remarked that the proposed model is quite robust, such that the finite element results are not sensitive to the mesh configuration and can rapidly converge to 3-D elasticity solutions using regular or irregular meshes.  相似文献   
10.
In this study, a novelty mathematical model is established to formulate the continuous culture of glycerol to 1,3-Propanediol (1,3-PD) by Klebsiella pneumoniae, in which the inhibition of 3-hydroxypropionaldehyde (3-HPA) to cells growth and activity of some enzymes (such as glycerol dehydratase (GDHt) and 1,3-PD oxidoreductase (PDOR)), and the passive diffusion and active transport of glycerol and 1,3-PD across cell membrane are all taken into consideration. Taking the mean relative error between the experimental data and calculated values as the performance index, a parameter identification model involving multiple nonlinear dynamic systems is presented. The identifiability of the parameter identification model is also proved. Finally, an improved particle swarm optimization (PSO) algorithm is constructed to find the optimal parameters for the systems under substrate limitation and excess conditions, respectively. Numerical results not only show that the established model can be used to describe the continuous fermentation reasonably, but also the improved PSO algorithm is valid.  相似文献   
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