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71.
为考查阻尼参数对空爆荷载等效静载动力系数的影响,理论推导了空爆荷载下结构等效单自由体系弹塑性位移解及延性比解,设计并计算了阻尼比0.000 1~0.1、延性比1~4的20种典型工况的动力系数,并与现行抗爆设计规范动力系数公式结果进行了对比。结果表明:阻尼比小于0.000 1时可基本代表无阻尼状态,阻尼比0.01的动力系数比无阻尼的最大降低幅度为2.08%,数值差异很小,因此阻尼比为0.01以内时,可忽略阻尼对动力系数的影响;阻尼比0.05的动力系数比无阻尼的降低幅度约9.92%,数值差异较大,认为阻尼比0.05以上时将具有明显的经济效益;现行设计规范动力系数更适用于柔性结构体系,运用于刚性结构抗爆设计时,计算误差较大,对阻尼比较小的结构设计更不利。 相似文献
72.
LIU HaiFeng LIU HaiYan & SONG WeiDong State Key Laboratory of Explosion Science Technology Beijing Institute of Technology Beijing China School of Civil Hydraulic Engineering Ningxia University Yinchuan School of Science 《中国科学:物理学 力学 天文学(英文版)》2010,(2)
This paper takes concrete as a four-phase composite made of the intact matrix and three mutually perpendicular groups of penny-shaped micro-cracks. The intact matrix is assumed to be elastic,homogeneous and isotropic,and the micro-cracks are penny-shaped. Combined with the failure mechanism of concrete subjected to impact loading,a dynamic constitutive model for concrete is developed based on Mori-Tanaka's average stress concept and Eshelby's equivalent inclusion theory. Experimental results show that concr... 相似文献
73.
74.
In this work, porous graphite nanofibers (PGNFs) were manufactured as promising catalyst supporter by a physical activation method for direct methanol fuel cells, and Pt nanoparticles were loaded on the PGNFs in order to prepare electrode materials by a chemical reduction method. The pore structures of the Pt/PGNFs were analyzed by N2 adsorption isotherms at 77 K. Electrocatalytic activities of final products were investigated by voltammetry and conductivity measurements in a 1.0 M CH3OH/0.5 M H2SO4. As a result, electrocatalytic activities of Pt/PGNFs were increased in the presence of Pt particles on the PGNFs and with increasing the specific surface area of the carbons. 相似文献
75.
T. V. Brantseva A. V. Antonov Yu. A. Gorbatkina M. L. Kerber T. P. Kravchenko A. A. Rybin 《Mechanics of Composite Materials》1999,35(6):453-460
A new device for studying the dynamic adhesive strength is created. A procedure for determining the dynamic adhesive strength in fiber—polymer systems under impact loading (pull-out technique) is developed. The adhesive strength of the interface of polymer—steel wire joints formed by polymers of different chemical nature (epoxy resin, polysulfone, and polypropylene) is examined. It is shown that the dynamic adhesive strength grows as the loading rate increases for all the systems under investigation and that the relationship between the adhesive strength and the loading rate,
, over a wide range of rates can be described by two straight lines corresponding to the quasi-static and impact loading, respectively. When passing from the quasi-static to dynamic loading, the character of scale relations of the adhesive strength does not change.Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 6, pp. 689–700, November–December, 1999. 相似文献
76.
恒定电场边值问题中点源的处理 总被引:1,自引:0,他引:1
讨论了不同情况下恒定电场中点源函数的表达式;用两种方法对点源作不同的处理;通过一个实的求解验证和说明了本文的方法。 相似文献
77.
78.
Welch K Mousavi S Lundberg B Strømme M 《The European physical journal. E, Soft matter》2005,18(1):105-112
A newly developed method for determining the frequency-dependent complex Young's modulus was employed to analyze the mechanical
response of compacted microcrystalline cellulose, sorbitol, ethyl cellulose and starch for frequencies up to 20 kHz. A Debye-like
relaxation was observed in all the studied pharmaceutical excipient materials and a comparison with corresponding dielectric
spectroscopy data was made. The location in frequency of the relaxation peak was shown to correlate to the measured tensile
strength of the tablets, and the relaxation was interpreted as the vibrational response of the interparticle hydrogen and
van der Waals bindings in the tablets. Further, the measured relaxation strength, holding information about the energy loss
involved in the relaxation processes, showed that the weakest material in terms of tensile strength, starch, is the material
among the four tested ones that is able to absorb the most energy within its structure when exposed to external perturbations
inducing vibrations in the studied frequency range. The results indicate that mechanical relaxation analysis performed over
relatively broad frequency ranges should be useful for predicting material properties of importance for the functionality
of a material in applications such as, e.g., drug delivery, drug storage and handling, and also for clarifying the origin of hitherto unexplained molecular processes. 相似文献
79.
F.?RahamanEmail author B.?C.?Bhui M.?Kalam 《International Journal of Theoretical Physics》2005,44(9):1413-1418
We analyze the space-time structure of local gauge string with a phenomenological energy–momentum tensor, as prescribed by
Vilenkin, in an arbitrary number of space-time dimensions with a non-zero cosmological constant Λ. A set of solutions of the
full non-linear Einstein's equations for the interior region of such a string is presented. 相似文献
80.
Jean-Fran?ois?Cordeau Gilbert?LaporteEmail author 《4OR: A Quarterly Journal of Operations Research》2003,1(2):89-101
The Dial-a-Ride Problem (DARP) consists of designing vehicle routes and schedules for n users who specify pick-up and drop-off requests between origins and destinations. The aim is to plan a set of m minimum cost vehicle routes capable of accommodating as many users as possible, under a set of constraints. The most common example arises in door-to-door transportation for elderly or disabled people. The purpose of this article is to review the scientific literature on the DARP. The main features of the problem are described and classified and some modeling issues are discussed. A summary of the most important algorithms is provided.AMS classification:
90B06, 90C27, 90C59 相似文献