全文获取类型
收费全文 | 528811篇 |
免费 | 4163篇 |
国内免费 | 1281篇 |
专业分类
化学 | 269200篇 |
晶体学 | 7645篇 |
力学 | 25990篇 |
综合类 | 17篇 |
数学 | 67795篇 |
物理学 | 163608篇 |
出版年
2021年 | 5039篇 |
2020年 | 5481篇 |
2019年 | 6222篇 |
2018年 | 8416篇 |
2017年 | 8562篇 |
2016年 | 11632篇 |
2015年 | 6181篇 |
2014年 | 10444篇 |
2013年 | 23493篇 |
2012年 | 18344篇 |
2011年 | 21797篇 |
2010年 | 16429篇 |
2009年 | 16287篇 |
2008年 | 20673篇 |
2007年 | 20518篇 |
2006年 | 18623篇 |
2005年 | 16630篇 |
2004年 | 15483篇 |
2003年 | 13964篇 |
2002年 | 13856篇 |
2001年 | 14734篇 |
2000年 | 11346篇 |
1999年 | 8753篇 |
1998年 | 7604篇 |
1997年 | 7472篇 |
1996年 | 6930篇 |
1995年 | 6258篇 |
1994年 | 6268篇 |
1993年 | 6017篇 |
1992年 | 6376篇 |
1991年 | 6866篇 |
1990年 | 6578篇 |
1989年 | 6487篇 |
1988年 | 6322篇 |
1987年 | 6132篇 |
1986年 | 5874篇 |
1985年 | 7408篇 |
1984年 | 7769篇 |
1983年 | 6532篇 |
1982年 | 6819篇 |
1981年 | 6326篇 |
1980年 | 6007篇 |
1979年 | 6506篇 |
1978年 | 6741篇 |
1977年 | 6629篇 |
1976年 | 6586篇 |
1975年 | 6302篇 |
1974年 | 6129篇 |
1973年 | 6425篇 |
1972年 | 4706篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
A. K. Shahani N. Korve K. P. Jones D. J. Paynton 《The Journal of the Operational Research Society》1994,45(8):916-926
Asthma is one of the major chronic diseases in many countries. At present there is no cure for asthma, but medical advances can help to reduce the chances of attacks of the condition. Efficient care for asthma involves complexity, uncertainty, variability and the use of scarce resources, and these are the same conditions that indicate a possible use for the modelling approach of operational research. This paper is concerned with a pilot model that was developed through joint work by medical professionals and operational researchers. The development of the model is explained and illustrative results indicate the potential value of the modelling approach for the care of asthma in the community. 相似文献
942.
We investigate the possibility of approximating a function on a compact setK of the complex plane in such a way that the rate of approximation is almost optimal onK, and the rate inside the interior ofK is faster than on the whole ofK. We show that ifK has an external angle smaller than π at some point zo∈δK, then geometric convergence insideK is possible only for functions that are analytic at zo. We also consider the possibility of approximation rates of the form exp(?cn β), for approximation insideK, where β is related to the largest external angle ofK. It is also shown that no matter how slowly the sequence {γ n } tends to zero, there is aK and a Lip β, β<1, functionf such that approximation insideK cannot have order {γ n }. 相似文献
943.
P. J. Wagstaffe A. Boenke E. Schnug A. S. Lindsey 《Fresenius' Journal of Analytical Chemistry》1992,344(1-2):1-7
Summary The sulphur content of three rapeseed reference materials has been certified on the basis of measurements made by inductively
coupled plasma-optical emission spectroscopy, isotope-dilution mass spectrometry and ion chromatography. Their suitability
for the calibration of x-ray fluorescence spectrometers used for measuring sulphur in rapeseed samples was established. 相似文献
944.
A. I. Vanin 《Journal of Applied Spectroscopy》1997,64(2):242-245
Light scattering by groups of spherical particles is considered. It is shown that the structure of the groups and their orientational
distribution can be judged from the spectrum and polarization of the scattered light.
Syktyvkar State University, 55, Oktyabr'skii Ave., Syktyvkar, 167001, Russia. Translated from Zhurnal Prikladnoi Spektroskopii,
Vol. 64, No. 2, pp. 228–231, March–April, 1997. 相似文献
945.
946.
947.
M. A. Skvortsov 《JETP Letters》1998,67(2):133-139
Motivated by the recent observation of the metal-insulator transition in Si MOSFETs, a study is made of the quantum interference
correction to the conductivity in the presence of the Bychkov-Rashba spin splitting. For a small splitting, a crossover from
the localizing to antilocalizing regime is obtained. The antilocalization correction vanishes, however, in the limit of a
large separation between the chiral branches. The relevance of the chiral splitting for the 2D electron gas in Si MOSFETs
is discussed.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 2, 118–123 (25 January 1998)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
948.
M.S. Anagnostou I. Panagiotopoulos A. Kostikas D. Niarchos G. Zouganelis 《Journal of magnetism and magnetic materials》1994,130(1-3):57-62
From the analysis of Mössbauer data for Y2Fe17 and Y2Fe17N3−δ at various temperatures the hyperfine fields for 4f, 6g, 12j, 12k iron sites were estimated as a function of temperature. The reduced magnetizations calculated from the values of the hyperfine fields are fitted with a mean field model for four interacting sublattices using a computer program. The estimated exchange interaction from the fitting procedure between the 4f sites is found strongly negative (antiferromagnetic) in Y2Fe17 whereas in Y2Fe17N3−δ it increases and becomes weak negative following a modified Slater-Néel curve. The rest of the exchange interactions are found positive or weak negative depending on the distances between the Fe atoms. 相似文献
949.
950.
The radiative capture of ultracold neutrons traversing thin and thick homogeneous layers of matter is analyzed. The applicability range of the formulas for the probabilities of reflection, transmission, and capture in thick layers (under certain conditions, they admit a simple interpretation—it is often quoted in the literature—that is based on the effective capture cross section, which is in inverse proportion to the velocity of a neutron in matter) is investigated, along with the conditions under which there arises the effective capture cross section. 相似文献