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991.
本文给出了变质量非完整系统相对于非惯性系的第一积分存在的条件,建立了这类系统的正则方程和变分方程,证明了由第一积分可直接构造系统的积分不变量,并给出一系列推论和一个例子. 相似文献
992.
WEI Yueguang ZHU Chen & WU Xiaolei LNM Institute of Mechanics Chinese Academy of Sciences Beijing China Correspondence should be addressed to Wei Yueguang 《中国科学G辑(英文版)》2004,47(1):86-100
Recentresearchesshowthatthehighstrengthnano-structuredmaterialscanbefabricatedbyusingsomeadvancedtechniques,andthemechanicalbehavioroftheconventionalmaterialscanbeimprovedbyusingasurface-nanocrystallinetechnique.Forexample,byusingthesevereplasticdeformation(SPD)method,onecanfabricatethenanocrystallinematerials[15].TheadoptedSPDmethodsmainlyincludethelargetorsionmethod[1],thelargepressingmethod[4]andtheultrasonicshotpeening(USP)method[5],etc.Theconstructionfeaturesofboththenano-structuredbl… 相似文献
993.
一种可用于离面位移测量的光路的优化设计 总被引:3,自引:1,他引:2
为了实现对复杂三维物体表面轮廓、小空间内物体的纵向位移或振动等测量,有必要研制高分辨力、非接触的光学检测系统。由于激光多普勒技术具有动态响应快、线性度好、非接触、测量精度高等特点而优先被用于复杂三维物体离面位移的测量。但是物体表面散射光的多普勒信号非常微弱,因此解决信号的强度、信噪比则是实现测量的关键。研究了激光多普勒技术及散射光相位的无规变化的统计规律,设计出一种空间分辨力很高的参考光路,将它用于固体离面位移测量效果很好,其相对误差为0.3%。 相似文献
994.
Ping Lin. 《Mathematics of Computation》2003,72(242):657-675
In many applications materials are modeled by a large number of particles (or atoms) where any one of particles interacts with all others. Near or nearest neighbor interaction is expected to be a good simplification of the full interaction in the engineering community. In this paper we shall analyze the approximate error between the solution of the simplified problem and that of the full-interaction problem so as to answer the question mathematically for a one-dimensional model. A few numerical methods have been designed in the engineering literature for the simplified model. Recently much attention has been paid to a finite-element-like quasicontinuum (QC) method which utilizes a mixed atomistic/continuum approximation model. No numerical analysis has been done yet. In the paper we shall estimate the error of the QC method for this one-dimensional model. Possible ill-posedness of the method and its modification are discussed as well.
995.
以单分散SiO2 胶态晶体球形成的三维有序结构为模板 ,利用胶体晶模板技术合成了三维长程有序的二氧化锰大孔材料 .通过X射线粉末衍射 (XRD)和扫描电子显微镜 (SEM)对产物进行了表征 .其中XRD数据显示所得产物为纯四方相二氧化锰 .SEM结果表明 ,所合成的二氧化锰大孔材料孔大小均匀 ,空间排列高度有序 ,很好地复制了SiO2 胶态晶体球的自组装方式 .此外 ,对三维有序二氧化锰大孔材料的合成过程进行了分析 ,研究了前体填充次数对产物孔结构的完整性和有序性的影响 ,还发现产物孔径的收缩存在异常现象 . 相似文献
996.
A. Zochowski 《Journal of Optimization Theory and Applications》1992,73(2):387-407
A method for computing the sensitivities of functionals depending on the solutions of elliptic equations defined over variable domains is presented. It is based on the material derivative approach and allows the uniform treatment of both singular and nonsingular cases. The novelty consists in defining the vector field connected with the domain transformation as the solution of an auxiliary elliptic equation. Such a choice does not restrict the range of admissible goal functionals and has many advantages from the numerical point of view. It allows one also to consider singular domain variations. 相似文献
997.
998.
Kanetada Nagamine 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2004,80(4):179
By using a well-defined mono-energetic, pencil-like, high-energy and intense muon beam, one can realize, via simultaneous measurements of energy-loss and multiple-scattering, a quick and element-selective radiography to detect e.g. a few kg of U which is shielded in a thick Fe container or hidden within 2–3 m of low-Z material. A source of such an ideal beam of muons can be realized in transportable form via truck trailers, by combining a compact 400 MeV electron accelerator for photo π/μ production, a superconducting solenoid for full-solid-angle π/μ capture and transport, a stopping in hot tungsten metal for cooling of energetic μ+ to sub-eV μ+, and finally a compact linear accelerator for rapid acceleration to 600 MeV. Principle and some details are described. 相似文献
999.
The complex velocity field of an oscillating Couette flow is measured with a Laser-Doppler velocimeter. Different evaluation methods are used for the determination of material functions such as relaxation times and the dynamic complex viscosity. 相似文献
1000.
H. D. Baecker 《BIT Numerical Mathematics》1970,10(4):405-414
The implications of the heap, reference variables and global generators in ALGOL 68 are examined and some notes on possible implementation mechanisms are presented. In particular the use or simulation of hardware with segment addressing facilities is discussed. 相似文献