全文获取类型
收费全文 | 267878篇 |
免费 | 3305篇 |
国内免费 | 1706篇 |
专业分类
化学 | 124942篇 |
晶体学 | 3760篇 |
力学 | 14530篇 |
综合类 | 115篇 |
数学 | 41560篇 |
物理学 | 87982篇 |
出版年
2021年 | 1396篇 |
2020年 | 1534篇 |
2019年 | 1692篇 |
2018年 | 10776篇 |
2017年 | 11615篇 |
2016年 | 7121篇 |
2015年 | 3021篇 |
2014年 | 3309篇 |
2013年 | 7477篇 |
2012年 | 10564篇 |
2011年 | 20029篇 |
2010年 | 12540篇 |
2009年 | 12632篇 |
2008年 | 17501篇 |
2007年 | 20947篇 |
2006年 | 6550篇 |
2005年 | 12654篇 |
2004年 | 8552篇 |
2003年 | 7788篇 |
2002年 | 5755篇 |
2001年 | 5046篇 |
2000年 | 4066篇 |
1999年 | 2955篇 |
1998年 | 2547篇 |
1997年 | 2428篇 |
1996年 | 2399篇 |
1995年 | 2210篇 |
1994年 | 2153篇 |
1993年 | 1938篇 |
1992年 | 2206篇 |
1991年 | 2316篇 |
1990年 | 2103篇 |
1989年 | 2088篇 |
1988年 | 2020篇 |
1987年 | 1894篇 |
1986年 | 1818篇 |
1985年 | 2346篇 |
1984年 | 2470篇 |
1983年 | 2020篇 |
1982年 | 2197篇 |
1981年 | 2087篇 |
1980年 | 2003篇 |
1979年 | 2155篇 |
1978年 | 2337篇 |
1977年 | 2116篇 |
1976年 | 2198篇 |
1975年 | 2091篇 |
1974年 | 2135篇 |
1973年 | 2166篇 |
1972年 | 1396篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
Zarubitskii O. G. Budnik V. G. Omel'chuk A. A. Melekhin V. T. Opanasyuk V. P. Zakharchenko N. F. 《Russian Journal of Applied Chemistry》2002,75(4):558-561
Electrochemical separation of lead-silver alloys into the constituents by thin-layer electrolysis in molten electrolytes, with bismuth as metal separator, is studied. It is proposed to determine the extent of component recovery by potentiometry. 相似文献
72.
In this paper, a two-dimensional finite volume unstructured mesh method (FVUM) based on a triangular background interpolation mesh is developed for analysing the evolution of the saltwater intrusion into single and multiple coastal aquifer systems. The model formulation consists of a ground-water flow equation and a salt transport equation. These coupled and non-linear partial differential equations are transformed by FVUM into a system of differential/algebraic equations, which is solved using backward differentiation formulas of order one through five. Simulation results are compared with previously published solutions where good agreement is observed. 相似文献
73.
Formalization for problems of multicriteria decision making under uncertainty is constructed in terms of guaranteed and weak
estimates. A relevant definition of the vector maximinimax value is given. Parameterization and approximation of maximum,
minimax, and maximinimax values based on the inverse logical convolution are suggested. An application for multicommodity
networks is considered.
Received: December 13, 2000 / Accepted: August 21, 2001?Published online May 8, 2002 相似文献
74.
A.-S. F. Obada M. Darwish H. H. Salah 《International Journal of Theoretical Physics》2002,41(9):1755-1768
In this paper a new state called odd-excited binomial state (OEBS) is introduced. It interpolates between the odd number state and the odd-excited coherent state. We discuss some statistical properties, such as the Glauber second-order correlation function and squeezing phenomenon (normal and amplitude-squared squeezing) for this state. The quasiprobability distribution functions (Husimi Q-function and Wigner W-function) are also examined. 相似文献
75.
The quantitative rainbow schlieren deflectometry (RSD) technique was applied to measure temperature and oxygen concentration in an axisymmetric hydrogen gas-jet diffusion flame burning in quiescent air at fuel jet exit Reynolds number of 70. Schlieren measurements were compared with conventional measurements using a thermocouple and a gas-sampling probe. Good agreement between the two measurement techniques was achieved on the fuel-lean side of the flame. 相似文献
76.
A. R. Volkov B. V. Shul'gin T. I. Polupanova V. N. Lebedev A. A. Nagornyi V. L. Petrov Yu. F. Kargin 《Journal of Applied Spectroscopy》1991,54(6):585-590
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 6, pp. 970–975, June, 1991. 相似文献
77.
In a twisted nematic liquid crystal cell we report and study the self-transparency effect induced by the creation of an isotropic droplet. A simple theoretical model is presented and good agreement with experimental data is found. In a two beams configuration transistor-like behavior is observed and theoretically discussed. 相似文献
78.
A firm's logistics cost, including shipping and inventory-carrying, is a substantial percentage of its sales. Nevertheless, typical inventory-control methods ignore or insufficiently represent the shipping cost. This paper describes a recursive algorithm that determines the reorder cycle-time that minimizes total logistics cost. It allows for a realistic accounting of shipping cost, which is modelled here as a function of shipping distance and weight. The algorithm uses a relaxation procedure to identify a suitable initial approximation to the optimal order cycle-time and then, through a series of recursive steps, moves to the optimal result. We demonstrate the algorithm with a single item, with a group of items that share a common order cycle, and with multi-items when item demands are random variables. Experience with this algorithm indicates that it converges to the optimal result in a very few steps. 相似文献
79.
T. Kumita Y. Kamiya M. Babzien I. Ben-Zvi K. Kusche I. V. Pavlishin I. V. Pogorelsky D. P. Siddons V. Yakimenko T. Hirose T. Omori J. Urakawa K. Yokoya D. Cline F. Zhou 《Laser Physics》2006,16(2):267-271
Thomson scattering of high-power laser and electron beams is a good test of electrodynamics in the high-field region. We demonstrated production of high-intensity X-rays in the head-on collision of a CO2 laser and 60-MeV electron beams at Brookhaven National Laboratory, Accelerator Test Facility. The energy of an X-ray photon was limited at 6.5 keV in the linear (lowest order) Thomson scattering, but the nonlinear (higher order) process produces higher energy X-rays. We measured the angular distribution of the high-energy X-rays and confirmed that it agrees with theoretical predictions. 相似文献
80.
M.F. Al-Kuhaili 《Journal of luminescence》2006,117(2):209-216
Thin films of sodium salicylate were deposited by spin coating from a solution prepared by dissolving sodium salicylate in methanol. The films were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, UV-visible spectroscopy and spectrofluorometry. The films were crystalline with a strong blue fluorescence peak at an emission wavelength of 419.3 nm. The influence of solution concentration, spin speed and annealing temperature on the fluorescence intensity was studied. Optimum results were obtained with a solution whose concentration was 2.5 M. It was found that lower spin speed resulted in higher fluorescence intensity. Moreover, the fluorescence intensity decreased as the annealing temperature was increased. The durability of the films over a period of 30 days was also investigated, and films annealed at higher temperatures were found to be less degraded with time. 相似文献