全文获取类型
收费全文 | 311982篇 |
免费 | 2007篇 |
国内免费 | 772篇 |
专业分类
化学 | 133219篇 |
晶体学 | 3913篇 |
力学 | 18611篇 |
综合类 | 7篇 |
数学 | 66249篇 |
物理学 | 92762篇 |
出版年
2019年 | 1242篇 |
2018年 | 18380篇 |
2017年 | 18971篇 |
2016年 | 11270篇 |
2015年 | 3174篇 |
2014年 | 2886篇 |
2013年 | 6901篇 |
2012年 | 12086篇 |
2011年 | 26309篇 |
2010年 | 15674篇 |
2009年 | 16152篇 |
2008年 | 21252篇 |
2007年 | 26305篇 |
2006年 | 5967篇 |
2005年 | 13053篇 |
2004年 | 9180篇 |
2003年 | 8974篇 |
2002年 | 6208篇 |
2001年 | 4744篇 |
2000年 | 3913篇 |
1999年 | 2785篇 |
1998年 | 2483篇 |
1997年 | 2363篇 |
1996年 | 2326篇 |
1995年 | 2127篇 |
1994年 | 2063篇 |
1993年 | 1916篇 |
1992年 | 2132篇 |
1991年 | 2262篇 |
1990年 | 2051篇 |
1989年 | 2063篇 |
1988年 | 2012篇 |
1987年 | 1911篇 |
1986年 | 1833篇 |
1985年 | 2360篇 |
1984年 | 2493篇 |
1983年 | 2067篇 |
1982年 | 2231篇 |
1981年 | 2108篇 |
1980年 | 2047篇 |
1979年 | 2188篇 |
1978年 | 2353篇 |
1977年 | 2138篇 |
1976年 | 2209篇 |
1975年 | 2101篇 |
1974年 | 2139篇 |
1973年 | 2184篇 |
1972年 | 1412篇 |
1971年 | 1250篇 |
1968年 | 1189篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
141.
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
142.
143.
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
144.
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
145.
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
146.
147.
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
148.
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
149.
We study a site analogue of directed percolation. Random trajectories are generated and their critical behavior is studied. The critical behavior corresponds to that of simple percolation in some of the parameter space, but elsewhere the exponents reveal new universality classes. As a byproduct, we use the model to make an improved estimate of the percolation hull exponents and to calculate the site percolation probability for the square lattice. 相似文献
150.
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