全文获取类型
收费全文 | 530951篇 |
免费 | 29580篇 |
国内免费 | 18331篇 |
专业分类
化学 | 293997篇 |
晶体学 | 7405篇 |
力学 | 24246篇 |
综合类 | 38篇 |
数学 | 65574篇 |
物理学 | 187602篇 |
出版年
2021年 | 4614篇 |
2020年 | 5422篇 |
2019年 | 6201篇 |
2018年 | 7587篇 |
2017年 | 8103篇 |
2016年 | 11745篇 |
2015年 | 8503篇 |
2014年 | 11388篇 |
2013年 | 25648篇 |
2012年 | 20957篇 |
2011年 | 25875篇 |
2010年 | 21905篇 |
2009年 | 21692篇 |
2008年 | 22062篇 |
2007年 | 21413篇 |
2006年 | 19812篇 |
2005年 | 18323篇 |
2004年 | 18127篇 |
2003年 | 15497篇 |
2002年 | 15136篇 |
2001年 | 16721篇 |
2000年 | 12656篇 |
1999年 | 10465篇 |
1998年 | 8781篇 |
1997年 | 8366篇 |
1996年 | 8569篇 |
1995年 | 8144篇 |
1994年 | 8272篇 |
1993年 | 8136篇 |
1992年 | 8338篇 |
1991年 | 7973篇 |
1990年 | 7434篇 |
1989年 | 7365篇 |
1988年 | 7352篇 |
1987年 | 6630篇 |
1986年 | 6400篇 |
1985年 | 7708篇 |
1984年 | 7937篇 |
1983年 | 5998篇 |
1982年 | 6492篇 |
1981年 | 6384篇 |
1980年 | 5961篇 |
1979年 | 6174篇 |
1978年 | 6264篇 |
1977年 | 6228篇 |
1976年 | 6458篇 |
1975年 | 5438篇 |
1974年 | 5395篇 |
1973年 | 5512篇 |
1972年 | 4029篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Sherif Yehia C. Mitros Sanjeev Kumar S. Jha Glenn M. Julian R. A. Dunlap 《Hyperfine Interactions》1987,34(1-4):415-418
The systematics of hyperfine magnetic fields at sp impurities on the Z-sites in Co based Heusler alloys are investigated. New TDPAC measurements of Cd hyperfine fields are reported. 相似文献
992.
Mass transport due to electromigration can be estimated if the diffusion coefficientD and the electromigration effective charge numberZ* are known. Neutron activated tracer scanning method determine the radioactivity at different positions. An automatic scanning
system for determining the radioactive concentration profiles developed using a microprocessor is described in this paper.
Using the radioactive concentration profiles the electromigration shift is determined. From this shift the electromigration
effective charge numberZ* is calculated. The system developed was tested for tin thin films. 相似文献
993.
994.
A. M. Kharitonov 《Thermophysics and Aeromechanics》2007,14(1):3-11
Sergey Alekseevich Khristianovich is one of the famous Russian mechanical engineers of the 20th century together with N.E.
Zhukovsky, S.A. Chaplygin, N.E. Kochin, and others. He made an immense contribution to some aspects of mechanics, such as
aerogasdynamics, rock mechanics, theory of plasticity, filtration theory, and environmental power engineering. All this was
preceded by a long, hard, and fruitful life full of outstanding events. 相似文献
995.
Historians have always seen jabr (restoration) and muqābala (confrontation) as technical terms for specific operations in Arabic algebra. This assumption clashes with the fact that the words were used in a variety of contexts. By examining the different uses of jabr, muqābala, ikmāl (completion), and radd (returning) in the worked-out problems of several medieval mathematics texts, we show that they are really nontechnical words used to name the immediate goals of particular steps. We also find that the phrase al-jabr wa'l-muqābala was first used within the solutions of problems to mean al-jabr and/or al-muqābala, and from there it became the name of the art of algebra. 相似文献
996.
The phase boundary theory and the contact rule of phase regions are compared, and some weaknesses of the latter are manifested.
The comparison between the Gupta’s method and the boundary theory method for constructing multicomponent isobaric sections
is also presented. 相似文献
997.
E. Granot S. Sternklar D. Schermann Y. Ben-Aderet M.H. Itzhaq 《Applied physics. B, Lasers and optics》2006,82(3):359-362
We use the spectral ballistic imaging technique to measure the impulse response of a Fabry–Pérot etalon with less than 0.2 ps
temporal resolution. The results show excellent agreement with the theoretical predictions and negligible noise. Comparison
to the Kramers–Kronig method along with its limitations is also presented.
PACS 42.65.Re; 07.60.Ly; 42.30.Kq 相似文献
998.
M. A. Posypkin I. Kh. Sigal 《Computational Mathematics and Mathematical Physics》2006,46(12):2187-2202
The efficiency of parallel implementations of the branch-and-bound method in discrete optimization problems is considered. A theoretical analysis and comparison of two parallel implementations of this method is performed. A mathematical model of the computation process is constructed and used to obtain estimates of the maximum possible speedup. Examples of problems in which none of these two parallel implementations can speed up the computations are considered. 相似文献
999.
In this study a novel technique for 2D spray temperature measurement is presented. For this purpose the thermographic phosphor (TP) Mg4GeO5.5F:Mn was dispersed in n-dodecane and atomised using a conventional semi solid-cone nozzle. The thermographic phosphor was excited electronically by a frequency tripled Nd:YAG laser (355 nm). An ICCD-camera in combination with an image doubler detected the subsequently emitted phosphorescence at both peak emission wavelengths located at 633 nm and 659 nm, respectively. Utilising suitable calibration measurements, the local spray temperature was determined by evaluating the intensity ratio of both emission wavelengths. To the knowledge of the authors this is the first approach of spray temperature measurement exploiting the temperature dependent intensity ratio of thermographic phosphors. PACS 07.20.Dt; 32.50.+d 相似文献
1000.
M. Gai 《Physics of Atomic Nuclei》2006,69(11):1805-1811
The Standard Solar Model (BP04) predicts a total 8B neutrino flux that is 17.2% larger than that measured in the salt phase of the SNO detector (and if it is significant, it
will indicate oscillation to sterile neutrinos). Hence, it is important to examine in detail the uncertainties (and values)
of inputs to the BP04. Currently, the largest fractional uncertainty is due to the new evaluation of the surface composition
of the Sun. We examine the nuclear input on the formation of solar 8B [S
17(0)] and demonstrate that it is still quite uncertain due to the ill-known slope of the measured astrophysical cross section
factor and thus illdefined extrapolation to zero energy. This yields an additional reasonable uncertainty due to extrapolation
of
−3.0
+0.0
eV b (
−14%
+0%
). Since a large discrepancy exists between measured as well as predicted slopes, the value of S
17(0) is dependent on the choice of data and theory used to extrapolate S
17(0). This situation must be alleviated by new measurement(s). The “world average” is driven by the Seattle result owing to
the very small quoted uncertainty, which we, however, demonstrate to be an overestimated accuracy. We propose more realistic
error bars for the Seattle results based on the published Seattle data.
The text was submitted by the author in English. 相似文献