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991.
二硫化钼粘结固体润滑涂层的径向和切向微动损伤的比较研究 总被引:7,自引:6,他引:7
通过径向和切向微动试验考察了二硫化钼粘结固体润滑涂层的微动摩擦学特性 ,并利用扫描电子显微镜、能量色散谱和X射线光电子能谱等分析了两类微动损伤区的微观特征 .结果表明 :二硫化钼粘结固体润滑涂层具有良好的抗径向微动损伤性能 ;切向微动条件下无混合区存在 ,涂层损伤强烈依赖于位移幅值 ,并伴随MoS2 的氧化 ;径向微动损伤呈现切向微动部分滑移区的特征 相似文献
992.
Y. Ootao R. Kawamura Y. Tanigawa T. Nakamura 《Archive of Applied Mechanics (Ingenieur Archiv)》1998,68(10):662-676
Summary A neural network model is applied to optimization problems of material compositions for a functionally graded material plate
with arbitrarily distributed and continuously varied material properties in the thickness direction. Unsteady temperature
distribution is evaluated by taking into account the bounds of the number of the layers. Thermal stress components for an
infinite functionally graded material plate are formulated under traction-free mechanical conditions. As a numerical example,
a plate composed of zirconium oxide and titanium alloy is considered. In the optimization problem of minimizing the thermal
stress distribution, the numerical calculations are carried out making use of the neural network. The optimum material composition
is determined by taking into account the effect of temperature-dependence of material properties. The results obtained by
neural network and ordinary nonlinear programming method are compared.
Received 3 March 1998; accepted for publication 22 May 1998 相似文献
993.
改进的移动最小二乘法 总被引:4,自引:2,他引:4
近年来发展的无网格方法大多采用移动员小二乘法来构造试函数,而应用移动最小二乘法形成的方程组有时会是病态的甚至奇异的,从而限制了它的发展和应用。本文采用带权正交函数作为基函数对移动最小二乘法做了改进,避免出现病态方程组,且在计算过程中不需要进行短阵求逆运算,提高了计算速度。之后,借鉴牛顿法、平衡法和摄动法对由移动最小二乘法得到的非线性代数方程组提出了新的求解方法。 相似文献
994.
G. G. Pereira W. V. Pinczewski D. Y. C. Chan L. Paterson P. E. Øren 《Transport in Porous Media》1996,24(2):167-201
Drainage displacements in three-phase flow under strongly wetting conditions are completely described by a simple generalisation of well understood two-phase drainage mechanisms. As in two-phase flow, the sequence of throat invasions in three-phase flow is determined by fluid connectivity and threshold capillary pressure for the invading interface. Flow through wetting and intermediate spreading films is important in determining fluid recoveries and the progress of the displacement in three-phase flow. Viscous pressure drops associated with flow through films give rise to multiple filling and emptying of pores. A three-phase, two-dimensional network model based on the pore-scale fluid distributions and displacement mechanisms reported by Øren et al. and which accounts for flow through both wetting and intermediate fluid films is shown to correctly predict all the important characteristics of three-phase flow observed in glass micromodel experiments. 相似文献
995.
This paper is devoted to the stationary problem of third-grade fluids in two and three dimensions. In two dimensions, we show existence of solutions and uniqueness, for a boundary of class C2,1 and small data, by generalizing the method used by J.M. Bernard for the stationary problem of second-grade fluids (we deal with a polynomial of four degrees instead of two degrees). Contrary to the case of two dimensions, the resolution of the problem of third-grade fluids in three dimensions requires the physical condition |α1+α2|<(24νβ)1/2. From this condition, we derive two “pseudo ellipticities” for the operator ν|A(u)|2+(α1+α2)tr(A(u)3)+β|A(u)|4, where A(u) is a 3-order symmetric matrix such that tr(A(u))=0. Thus, with, in addition, a sharp estimate of the scalar product (|A(u)|2A(u)-|A(v)|2A(v),A(u)-A(v)), we are able to prove existence of solutions and uniqueness, for a boundary of class C2,1 and small data, in three dimensions.
Résumé
Cet article est consacré au problème stationnaire des fluides de grade trois en dimension deux et trois. En dimension deux, nous montrons l’existence de solutions et l’unicité, pour une frontière de classe C2,1 et une donnée petite, en généralisant la méthode utilisée par J.M. Bernard pour le problème stationnaire des fluides de grade deux (nous avons affaire à un polynôme de degré quatre au lieu de deux). Contrairement au cas de la dimension deux, la résolution du problème des fluides de grade trois en dimension trois requière la condition physique |α1+α2|<(24νβ)1/2. De cette condition, nous déduisons deux “pseudo matrice” pour l’opérateur ν|A(u)|2+(α1+α2)tr(A(u)3)+β|A(u)|4, où A(u) est une matice symétrique d’ordre 3 à trace nulle. De là, avec, en plus, une fine estimation du produit scalaire (|A(u)|2A(u)-|A(v)|2A(v),A(u)-A(v)), nous sommes capables de prouver l’existence de solutions et l’unicité, pour une frontière de classe C2,1 et une donnée petite, en dimension trois. 相似文献996.
Steady convective mass transfer to or from fluid interfaces in pores of angular cross-section is theoretically investigated.
This situation is relevant to a variety of mass transport process in porous media, including the fate of residual non-aqueous
phase liquid ganglia and gas bubbles. The model incorporates the essential physics of capillarity and solute mass transfer
by convection and diffusion in corner fluid filaments. The geometry of the corner filaments, characterized by the fluid–fluid
contact angle, the corner half-angle and the interface meniscus curvature, is accounted for. Boundary conditions of zero surface
shear (‘perfect-slip’) and infinite surface shear (‘no-slip’) at the fluid–fluid interface are considered. The governing equations
for laminar flow within the corner filament and convective diffusion to or from the fluid–fluid interface are solved using
finite-element methods. Flow computations are verified by comparing the dimensionless resistance factor and hydraulic conductance
of corner filaments against recent numerical solutions by Patzek and Kristensen (J. Colloid Interface Sci 236, 305–317 2001). Novel results are obtained for the average effluent concentration as a function of flow geometry and pore-scale
Peclet number. These results are correlated to a characteristic corner length and local pore-scale Peclet number using empirical
equations appropriate for implementation in pore network models. Finally, a previously published “2D-slit” approximation to
the problem at hand is checked and found to be in considerable error. 相似文献
997.
This paper describes the formulation of a quasi-1-D network model, referred to as the ‘bubble model’, and its application
for simulating particle transport and filtration through a granular filter bed. The model comprises a series of homogeneous
sites linked through bundles of cylindrical bonds that represent flow pathways through distributions of pores and pore throats.
This model incorporates pore scale processes of particle sieving and infiltration are based on numerical simulations described
in a companion paper. The modeling of infiltration is further refined based on detailed experimental observations and measurements
of the filtration of a dilute suspension of acrylic particles through a column of glass beads reported by Yoon et al. (2005 Water Resour. Res., to appear). Their data distinguish (a) between the collection of particles on grain surfaces and at grain-to-grain contact
points, and (b) between particles that are fully entrapped and those that are hindered (temporarily collected) and can later
become detached. These effects are represented by two parameters that characterize the probability of attachment and are linked
to the surface roughness of the grains; one that describes the minimum particle size that can be fully entrapped, and one
that describes the detachment rate. These parameters can be readily calibrated from conventional measurements of effluent
concentration and effluent particle size distribution. Detailed comparisons with the data reported by Yoon et al. show that the proposed bubble model is able to achieve reliable predictions of the spatial distribution of particles within
the filter bed following phases of particle injection and washing. 相似文献
998.
Different from the approaches used in the earlier papers, in this paper, the Halanay inequality technique, in combination
with the Lyapunov method, is exploited to establish a delay-independent sufficient condition for the exponential stability
of stochastic Cohen–Grossberg neural networks with time-varying delays and reaction–diffusion terms. Moreover, for the deterministic
delayed Cohen–Grossberg neural networks, with or without reaction–diffusion terms, sufficient criteria for their global exponential
stability are also obtained. The proposed results improve and extend those in the earlier literature and are easier to verify.
An example is also given to illustrate the correctness of our results. 相似文献
999.
STABILITY ANALYSIS OF HOPFIELD NEURAL NETWORKS WITH TIME DELAY 总被引:3,自引:0,他引:3
IntroductionInrecentyearsthedynamicbehaviorofthefollowingHopfieldneuralnetworksmodelwithtimedelayhavebeeninvestigatedthoroughlyCi xi(t) =-xiRi + ∑nj=1Tijfj(xj(t-τij) ) +Ii (i=1 ,2 ,… ,n) ,( 1 )whereRi,CiandIirepresentresistance ,capacitanceandelectriccurrent.Ri,Ciarepa… 相似文献
1000.