全文获取类型
收费全文 | 251353篇 |
免费 | 1587篇 |
国内免费 | 402篇 |
专业分类
化学 | 115081篇 |
晶体学 | 3202篇 |
力学 | 13582篇 |
综合类 | 7篇 |
数学 | 39723篇 |
物理学 | 81747篇 |
出版年
2019年 | 1176篇 |
2018年 | 10432篇 |
2017年 | 11290篇 |
2016年 | 6597篇 |
2015年 | 2425篇 |
2014年 | 2546篇 |
2013年 | 6449篇 |
2012年 | 9321篇 |
2011年 | 18806篇 |
2010年 | 11521篇 |
2009年 | 11643篇 |
2008年 | 16458篇 |
2007年 | 20084篇 |
2006年 | 5609篇 |
2005年 | 11990篇 |
2004年 | 7912篇 |
2003年 | 7318篇 |
2002年 | 5320篇 |
2001年 | 4488篇 |
2000年 | 3629篇 |
1999年 | 2613篇 |
1998年 | 2286篇 |
1997年 | 2203篇 |
1996年 | 2157篇 |
1995年 | 2003篇 |
1994年 | 1975篇 |
1993年 | 1805篇 |
1992年 | 2066篇 |
1991年 | 2155篇 |
1990年 | 1944篇 |
1989年 | 1962篇 |
1988年 | 1916篇 |
1987年 | 1812篇 |
1986年 | 1738篇 |
1985年 | 2248篇 |
1984年 | 2405篇 |
1983年 | 1961篇 |
1982年 | 2140篇 |
1981年 | 2029篇 |
1980年 | 1948篇 |
1979年 | 2116篇 |
1978年 | 2294篇 |
1977年 | 2081篇 |
1976年 | 2160篇 |
1975年 | 2057篇 |
1974年 | 2107篇 |
1973年 | 2139篇 |
1972年 | 1379篇 |
1971年 | 1222篇 |
1968年 | 1177篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
121.
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
122.
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
123.
Electroactive conducting polymers for corrosion control 总被引:1,自引:0,他引:1
Dennis E. Tallman Geoff Spinks Anton Dominis Gordon G. Wallace 《Journal of Solid State Electrochemistry》2002,6(2):73-84
There is an intensive effort underway to develop new corrosion control coatings for structural metals. In part, this effort
has been motivated by the desire to replace chromium(VI)-containing coatings currently used for corrosion control of iron
and aluminum alloys. Cr(VI) has been shown to be hazardous to the environmental and to human health, and its use in many countries
will be sharply curtailed in the coming years. Electroactive conducting polymers (ECPs) represent a class of interesting materials
currently being explored for use in corrosion control coating systems, possibly as a replacement for Cr(VI)-based coatings.
The electroactivity and the electronic conductivity (or semiconductivity) of ECPs set them apart from traditional organic
coatings. As with chromate, interesting and potentially beneficial interactions of ECPs with active metal alloys such as steel
and aluminum are anticipated, with concomitant alteration of their corrosion behavior. A review of this active research area
will be presented in two parts. Here in Part 1, a general introduction to the topic of corrosion control by ECPs will be presented,
including an overview of corrosion and its control by traditional methods, an introduction to ECPs and their properties, and
a discussion of the processing issues surrounding the use of ECPs as coatings. Part 1 also includes a review of the literature
on the use of ECPs as coatings (or components of coatings) on non-ferrous active metals, principally aluminum and aluminum
alloys, although some work on zinc, copper, silver, titanium and silicon will also be described. In Part 2 of this review
(to be published in the next issue of this journal), the rather extensive literature on the use of ECPs for the corrosion
control of ferrous alloys (steels) will be reviewed.
Electronic Publication 相似文献
124.
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
125.
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
126.
127.
V. Yu. Baranovskii L. L. Yasina M. V. Motyakin I. I. Aliev S. Shenkov M. Dimitrov N. Lambov A. M. Wasserman 《Polymer Science Series A》2006,48(12):1304-1309
Partially water-swellable polymer networks were synthesized on the basis of poly(acrylic acid) and various macrodiisocyanates. Hydrophilic and hydrophobic local regions were revealed in swollen networks (hydrogels) by means of the spin probe technique. The local mobility in hydrophobic regions depends on the macrodiisocyanate structure; however, it is substantially lower than that in hydrophilic regions for all gels. It was assumed that the presence of hydrophobic and hydrophilic regions and the difference in their local dynamics must have a substantial effect on the pharmacokinetics of release of drugs immobilized in these hydrogels. 相似文献
128.
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
129.
This study addresses the problem of the automatic flow regime identification in two-phase flows in pipes. A novel wavelet transform-based approach is proposed and validated using time series of differential pressure fluctuations. The experimental data on the differential pressure measured in a vertically installed Venturi meter for air-water flow were analyzed and found to be appropriate for flow regime identification. The wavelet spectrum of the measured signal is shown to characterize the flow patterns completely, and the vector of the wavelet variances is proposed as the characteristic vector for use in an on-line flow regime identification system. 相似文献
130.
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