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以煤矿供电网越级跳闸现象为研究对象,在分析电流纵联差动保护、级联闭锁工作原理和防越级跳闸保护逻辑的基础上,介绍了一种煤矿供电网防越级跳闸保护装置的研制过程。保护装置以32位ARM处理器MB9BF618S为控制核心,可以实时检测供电网输电线路的工作状态,对输电线路故障进行有效的保护。文中主要叙述了保护装置的总体结构,给出了电流/电压输入模块、开关量输入/输出模块和通信模块的设计方案。该保护装置具有结构简单、操作方便、可靠性高等特点,能够满足煤矿供电网防越级跳闸保护的要求,具有较高的应用价值。 相似文献
95.
针对局部二值模式(LBP)特征在低分辨率的人脸图 像上识别率较低的问题,提出了一种基于分块中心对称局部二值模式(CS-LBP,center symmetric local binary pattern)和加权主成分分析(PCA)算法的低分辨率人脸识别算法。 首先利用分块CS-LBP算子提取低分辨率人脸图像的特征;然后利用加权PCA算子对特 征进行降维, 从而得到更强的分类特征;最后利用最近邻分类器选出人脸最优分类类别并计算识别率。在 ORL人脸库上的实验表明,在人脸图像分辨率下降到(12×10)时,本 文算法的识别率仍能达 到85.00%,基本满足了实际运用中对识别率的要求,并且降低了运算 时间。 相似文献
96.
1introductionWithregardtomobilecommunicationsystems,theincreasingdemandformobilecommunicationserviceandthefinitespectrumallocatedtothisserviceleadtotheproposalofthecellularstructure.Thefrequencyreuseconceptisthecoreofthecellularmobilecommunicationsystems.Mostcellularnetworkstodayusefixedchannelallocation(FCA),inwhichasmallnumberofchannelsareallocatedpermanentlytoeverycell.Tosupporthighsubscriberdensities,differentdynamicchannelallocation(DCA)schemes11avebeenstudiedtoincreasethechannelutiliza… 相似文献
97.
The use of real time channel borrowing in digital cellular asynchronous hybrid FDMA/TDMA systems is considered. These systems, which are exemplified by North American digital cellular (IS-54), are asynchronous in the sense that time slots in different cells are not aligned. CBWL (channel borrowing without locking) techniques can be applied but (without cell-to-cell synchronization) borrowing individual time slots from adjacent cells would violate co-channel interference constraints. Instead, frequency carriers can be borrowed. In IS-54, a carrier supports three TDMA slots. So if only one TDMA slot is needed in the borrowing cell, two TDMA slots are unnecessarily transferred. We devised an appropriate carrier borrowing scheme and an analytical model to determine the traffic performance of TDMA/CBWL. Fast carrier returning is used to increase channel utilization by returning borrowed carriers as soon as possible. An efficient computational method that uses macro-states, decomposition, combinatorial analysis and the convolution algorithm is devised to find blocking probabilities. The results show that in comparison with FCA, the new CBWL scheme can significantly improve system performance of asynchronous TDMA cellular systems that use FDMA/TDMA multiplexing. 相似文献
98.
Yu. K. Tovbin 《Russian Chemical Bulletin》1999,48(8):1450-1461
Principles of the theory of adsorption of large molecules blocking more than one adsorption center on a surface in slit-like
pores are proposed. The theory takes into account lateral adsorbate—adsorbate interactions and nonuniformity of the pore walls.
The equations of adsorption isotherms are derived using the cluster approach. The lateral interactions are taken into account
in the quasi-chemical approximation, preserving effects of direct correlations, and in the mean field approximation without
effects of correlations. The following problems are discussed: 1) distinguishing of partial contributions of nonuniform adsorption
centers on the pore walls; 2) exact solution for dimer adsorption in a two-layer pore with uniform walls; 3) basic types of
adsorption isotherms, for which the differences are due to various orientations of the adsorbate in micropores with uniform
walls; 4) estimates of the pressure responsible for volume filing of micropores; and 5) the effect of nonuniformity of the
pore walls on the pressure values.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1467–1478, August, 1999. 相似文献
99.
P. Sigmund A. Schinner 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(3):425-434
The Bohr theory treats charged-particle stopping as a sequence of interactions with classical target electrons bound harmonically
to their equilibrium positions. We demonstrate that equivalent results can be derived on the assumption of free binary collisions
governed by a suitable effective potential. This kind of mapping is rigorous in the limits of distant and close collisions
and therefore provides a tool to evaluate energy losses via binary-scattering theory. This model was developed with the aim of calculating stopping forces for heavy ions at moderately
high velocities, where a classical-orbital calculation is typically superior to the Born approximation. The effective potential
employed holds equally well for dressed as for stripped ions. Unlike the Bohr theory, the present evaluation avoids a formal
division into regimes of close and distant collisions that do not necessarily join smoothly. Moreover, no perturbation expansion
is necessary. For these reasons the overall accuracy as well as the range of validity of the Bohr model are significantly
enhanced. Extensive tests have been performed, including comparisons with rigorous evaluations of the Z
1
3 effect, with excellent agreement even where such was not necessarily expected. Moreover, credible results have been obtained
under conditions where the perturbation expansion shows poor convergence. A comparison with experimental data on O–Al is encouraging,
even though shell corrections and projectile excitation/ionization have not yet been incorporated and input has not yet been
optimized.
Received 21 April 2000 and Received in final form 16 June 2000
An erratum to this article is available at . 相似文献
100.
Gerd Rpke 《等离子体物理论文集》2019,59(4-5)
The Mott effect describes the dissolution of bound states in a dense partially ionized plasma. It occurs when the ionization potential depression, owing to effects of correlation and degeneracy, compensates the binding energy of the bound state. At high densities and moderate temperatures, the Pauli blocking becomes important and influences significantly the degree of ionization in the region of degenerate plasmas. A quantum statistical approach is used where the total density is decomposed in an uncorrelated, “free” part and correlations, as a consequence of the cluster decomposition of the self‐energy. The contribution of correlations to the total density is given by bound states and continuum correlations. Exact solutions for a separable potential are compared to perturbation theory and numerical solutions of the in‐medium Schrödinger equation. The in‐medium scattering phase shifts are evaluated, and the role of continuum correlations is discussed. The Pauli blocking of bound states and the density of states are considered for warm dense matter conditions. 相似文献