全文获取类型
收费全文 | 358199篇 |
免费 | 2494篇 |
国内免费 | 862篇 |
专业分类
化学 | 187794篇 |
晶体学 | 5184篇 |
力学 | 16604篇 |
综合类 | 13篇 |
数学 | 42248篇 |
物理学 | 109712篇 |
出版年
2020年 | 3339篇 |
2019年 | 3960篇 |
2018年 | 5591篇 |
2017年 | 5644篇 |
2016年 | 7300篇 |
2015年 | 3779篇 |
2014年 | 6484篇 |
2013年 | 14722篇 |
2012年 | 11145篇 |
2011年 | 13392篇 |
2010年 | 10282篇 |
2009年 | 10307篇 |
2008年 | 13041篇 |
2007年 | 13006篇 |
2006年 | 12002篇 |
2005年 | 10789篇 |
2004年 | 9941篇 |
2003年 | 8997篇 |
2002年 | 9072篇 |
2001年 | 9876篇 |
2000年 | 7634篇 |
1999年 | 5792篇 |
1998年 | 5133篇 |
1997年 | 5035篇 |
1996年 | 4666篇 |
1995年 | 4032篇 |
1994年 | 4070篇 |
1993年 | 4144篇 |
1992年 | 4315篇 |
1991年 | 4623篇 |
1990年 | 4444篇 |
1989年 | 4496篇 |
1988年 | 4326篇 |
1987年 | 4332篇 |
1986年 | 4126篇 |
1985年 | 5305篇 |
1984年 | 5424篇 |
1983年 | 4513篇 |
1982年 | 4841篇 |
1981年 | 4624篇 |
1980年 | 4264篇 |
1979年 | 4709篇 |
1978年 | 5007篇 |
1977年 | 5079篇 |
1976年 | 5132篇 |
1975年 | 4855篇 |
1974年 | 4780篇 |
1973年 | 5050篇 |
1972年 | 3746篇 |
1971年 | 3328篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
The properties of a polymer-concrete composed of polyester matrix and locally available rock aggregate are investigated. The formula of the concrete is found by an experimental-calculation approach in such a way as to attain a closer packing of the aggregate particles on the one hand, and to ensure the needed processing characteristics (placeability) of the mix on the other. It is shown experimentally that the material obtained has a rather high compression strength. Under prolonged compression loads, the polymer-concrete exhibits a noticeable creep behavior with a linear relation between the creep strains and stresses. After the action of half the ultimate load over 3000 h, the total strains exceed the instantaneous ones by 2.0 to 2.2 times. The accumulation of irreversible strains is also observed; however, their contribution to the total strain is small. It is found that the stress-strain relation can be represented by the equation of linear hereditary creep theory.Institute of Polymer Mechanics, University of Latvia, Riga, LV-1006, Latvia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 2, pp. 147–162, March–April, 1999. 相似文献
92.
The applicability of differential electrolytic potentiometry as a detection system in flow injection analysis is investigated. A computer-controlled injector which delivers precise volumes of sample solutions in a reproducible manner was developed. Conditions such as current density employed, the concentrations of the solutions used and the flow rate were optimized. Chloride in water was determined by means of this system. The relation between chloride concentration and the measured signal was found to be Nernstian for solutions of concentrations above 6 μg ml−1 chloride. For solutions below this concentration, the relation is linear. 相似文献
93.
V. A. Nebol'sin B. M. Darinskii E. E. Popova A. A. Shchetinin 《Russian Physics Journal》1995,38(10):1023-1026
An estimate of the factors which influence the rate of growth of filamentary silicon crystals in a standard chloride system using a quartz reactor with hot walls is given. It is shown that a diffusion form of crystallization is observed under the conditions investigated.Voronezh State Technical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 22–26, October, 1995. 相似文献
94.
V. I. Storozhev 《Journal of Mathematical Sciences》1995,77(6):3514-3518
On the basis of the method of successive approximations in formal series we construct systems of particular solutions of the
equations of planar and flexural harmonic vibrations of thin rectilinear anisotropic plates with a plane of symmetry of elastic
properties parallel to the faces. The solutions constructed are classified as special sk-functions of generalized complex
variables.
Translated fromTeoreticheskaya i Prikladnaya Mekhanika No. 24, 1993, pp. 54–61. 相似文献
95.
A. E. Dorokhov 《Czechoslovak Journal of Physics》2002,52(3):C79-C90
Nonperturbative nolocal structure of QCD vacuum is well described by instanton model. Specific helicity and flavor structure of zero modes of quarks, in instanton field allows simultaneously to explain some important features of low-and high-energy hadron phenomemology. The basic characteristics of hadron spectrum, partonic sum rules, heavyquark potential etc within the instanton liquid model are briefly discussed. 相似文献
96.
The microhardness and content of carbon in electroplated gold coatings were studied as influenced by the operation time of citrate and citrate-phosphate gold-plating electrolytes. Such physicomechanical properties as porosity, microhardness, internal stress, plasticity, and microstructure of electroless-plated and electroplated nickel coatings were studied and analyzed. 相似文献
97.
V. Palyok I.A. Szabó D.L. Beke A. Kikineshi 《Applied Physics A: Materials Science & Processing》2002,74(5):683-687
Surface relief formation at holographic recording on amorphous selenium films was demonstrated and investigated. The presence
of this optical phase modulation component is essential for ensuring significant, stable and erasable optical recording in
a-Se films at 290–320 K temperatures, where conventional photodarkening was known as insignificant and unstable. Photocrystallization
can only be observed in super-exposed a-Se films at the given experimental conditions of hologram recording. Erasing behavior
of surface relief gratings under heat treatment was also investigated in order to reveal further details of the mechanism.
Photoinduced structural transformations within the amorphous phase, connected to local ordering under the condition of light-induced
fluidity, are proposed as an explanation for the relief formation and erasing. The observed reversible optical recording process
may be useful for the various optoelectronic applications of photoconductive a-Se layers.
Received: 12 June 2000 / Accepted: 6 June 2001 / Published online: 30 August 2001 相似文献
98.
The simple relation between representations of the covering groups of SL2 and GL2 makes it possible to fuse and extend the recent metaplectic results of Shimura, Waldspurger, Flicker, and ourselves. By giving a new (purely local andL-function theoretic) treatment of the Waldspurger-Shintani correspondence, we also simplify some of Waldspurger’s original results. 相似文献
99.
100.