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31.
The expansion coefficient CD|L| of Coulomb potential 1/r12 of atomic system in hyper‐spherical harmonics is derived and the explicit expression is given. 相似文献
32.
Norbert Polat 《Discrete Mathematics》2009,309(8):2119-2133
A graph G has the Median Cycle Property (MCP) if every triple (u0,u1,u2) of vertices of G admits a unique median or a unique median cycle, that is a gated cycle C of G such that for all i,j,k∈{0,1,2}, if xi is the gate of ui in C, then: {xi,xj}⊆IG(ui,uj) if i≠j, and dG(xi,xj)<dG(xi,xk)+dG(xk,xj). We prove that a netlike partial cube has the MCP if and only if it contains no triple of convex cycles pairwise having an edge in common and intersecting in a single vertex. Moreover a finite netlike partial cube G has the MCP if and only if G can be obtained from a set of even cycles and hypercubes by successive gated amalgamations, and equivalently, if and only if G can be obtained from K1 by a sequence of special expansions. We also show that the geodesic interval space of a netlike partial cube having the MCP is a Pash-Peano space (i.e. a closed join space). 相似文献
33.
34.
Objectives
A patient with a breast tissue expander may require a diagnostic assessment using magnetic resonance imaging (MRI). To ensure patient safety, this type of implant must undergo in vitro MRI testing using proper techniques. Therefore, this investigation evaluated MRI issues (i.e., magnetic field interactions, heating, and artifacts) at 3-Tesla for a breast tissue expander with a remote port.Methods
A breast tissue expander with a remote port (Integra Breast Tissue Expander, Model 3612-06 with Standard Remote Port, PMT Corporation, Chanhassen, MN) underwent evaluation for magnetic field interactions (translational attraction and torque), MRI-related heating, and artifacts using standardized techniques. Heating was evaluated by placing the implant in a gelled-saline-filled phantom and MRI was performed using a transmit/receive RF body coil at an MR system reported, whole body averaged specific absorption rate of 2.9-W/kg. Artifacts were characterized using T1-weighted and GRE pulse sequences.Results
Magnetic field interactions were not substantial and, thus, will not pose a hazard to a patient in a 3-Tesla or less MRI environment. The highest temperature rise was 1.7 °C, which is physiologically inconsequential. Artifacts were large in relation to the remote port and metal connector of the implant but will only present problems if the MR imaging area of interest is where these components are located.Conclusions
A patient with this breast tissue expander with a remote port may safely undergo MRI at 3-Tesla or less under the conditions used for this investigation. These findings are the first reported at 3-Tesla for a tissue expander. 相似文献35.
H. A. Sodano 《Experimental Mechanics》2006,46(5):627-635
When a conductive material is subjected to a time changing magnetic field, eddy currents are induced in that structure. The
eddy currents circulate inside the conductor resulting in a magnetic field that interacts with the applied field. The eddy
current field is such that it opposes the change in flux resulting in a force between the source and conductor. The time changing
magnetic field necessary to induce an electrometric force in the materials can be generated through a variety of different
ways. In the present study, a permanent magnet will be mounted to the tip of an electromagnetic shaker such that the motion
of the magnet relative to the structure will cause a time changing field and the formation of eddy currents. The actuator
will be demonstrated to be beneficial due to its ability to apply actuation forces without contacting the structure. This
study will show that the non-contact nature of the system eliminates mass loading and added stiffness which are downfalls
of traditional excitation techniques. Additionally, it will be shown that the use of a non-contact device preserves the mode
shapes of the structure, whereas a stinger results in distortions due to the added constraint. Using this concept, a model
of the actuation system will be developed, allowing the beams response to be simulated. The actuation system will then be
used to excite a cantilever beam to obtain the modal parameters without contacting the structure. The novel non-contact actuation
system developed in this paper provides a new method performing vibration testing of on lightweight or flexible structures
while preserving their dynamics. 相似文献
36.
Johan van Benthem 《Logica Universalis》2007,1(1):125-138
We prove new Lindstr?m theorems for the basic modal propositional language, and for some related fragments of first-order
logic. We find difficulties with such results for modal languages without a finite-depth property, high-lighting the difference
between abstract model theory for fragments and for extensions of first-order logic. In addition we discuss new connections
with interpolation properties, and the modal invariance theorem.
Mathematics Subject Classification (2000): Primary 03B45; Secondary 03C95 相似文献
37.
Maxwell equations are solved in a layer comprising a finite number of homogeneous isotropic dielectric regions ended by anisotropic perfectly matched layers (PMLs). The boundary-value problem is solved and the dispersion relation inside the PML is derived. The general expression of the eigenvalues equation for an arbitrary number of regions in each layer is obtained, and both polarization modes are considered. The modal functions of a single layer ended by PMLs are found, and their orthogonality relation is derived. The present method is useful to simulate scattering problems from dielectric objects as well as propagation in planar slab waveguides. Its potential to deal with more complex problems such as the scattering from an object with arbitrary cross section in open space using the multilayer modal method is briefly discussed. 相似文献
38.
The dayan tabla is a percussion instrument used as an accompaniment to classical Indian singing or music. In this work, a mathematical model was developed to describe the response of this instrument and to analytically determine the areal density distribution required to obtain overtones that were rational multiples of each other. The model was verified by comparing the exact Bessel function solution of the constant density drum with the results obtained using the approximate method outlined in this paper. The maximum error obtained for the first 10 natural frequencies was less than 1% while the associated mode shapes differed by less than 5%. The bi-density model of the tabla, with a mass ratio of 4.1 and a radius ratio of 0.49, predicted natural frequency ratios of approximately 1.1:2:3 (twice):4 (twice) for the fundamental and the first few overtones. This compares well with previously reported experimental data. 相似文献
39.
This work concerns the control of sound transmission through double laminated panels with viscoelastic core using semi-passive piezoelectric shunt technique. More specifically, the system consists of two laminated walls, each one composed of three layers and called sandwich panel with an air cavity in between. The external sandwich panel has a surface-mounted piezoelectric patches. The piezoelectric elements, connected with resonant shunt circuits, are used for the vibration damping of some specific resonance frequencies of the coupled system. Firstly, a finite element formulation of the fully coupled visco-electro-mechanical-acoustic system is presented. This formulation takes into account the frequency dependence of the viscoelastic material. A modal reduction approach is then proposed to solve the problem at a lower cost. In the proposed technique, the coupled system is solved by projecting the mechanical displacement unknown on a truncated basis composed by the first real short-circuit structural normal modes and the pressure unknown on a truncated basis composed by the first acoustic modes with rigid boundaries conditions. The few initial electrical unknowns are kept in the reduced system. A static correction is also introduced in order to take into account the effect of higher modes. Various results are presented in order to validate and illustrate the efficiency of the proposed finite element reduced order formulation. 相似文献
40.
Nahmias introduced the concept of a fuzzy variable as a possible axiomatic framework from which a rigorous theory of fuzziness may be constructed. In this paper we attempt to shed more light on fuzzy variables in analogy with random variables. In particular, we study the problem: if X1, X2,…,Xn are mutually unrelated fuzzy variables with common membership function μ and α1, α2,…,αn are real numbers satisfying αi ? o for every i and Σi=1nαi=1, when does does Z = Σi = 1nαiXi have the same membership function μ? 相似文献