全文获取类型
收费全文 | 215637篇 |
免费 | 3630篇 |
国内免费 | 527篇 |
专业分类
化学 | 117296篇 |
晶体学 | 3248篇 |
力学 | 8598篇 |
综合类 | 3篇 |
数学 | 26690篇 |
物理学 | 63959篇 |
出版年
2021年 | 1685篇 |
2020年 | 2020篇 |
2019年 | 2137篇 |
2018年 | 2913篇 |
2017年 | 2820篇 |
2016年 | 4587篇 |
2015年 | 3187篇 |
2014年 | 4429篇 |
2013年 | 10366篇 |
2012年 | 8887篇 |
2011年 | 10110篇 |
2010年 | 6937篇 |
2009年 | 6549篇 |
2008年 | 9255篇 |
2007年 | 9181篇 |
2006年 | 8506篇 |
2005年 | 7856篇 |
2004年 | 7107篇 |
2003年 | 6191篇 |
2002年 | 5858篇 |
2001年 | 5992篇 |
2000年 | 4522篇 |
1999年 | 3435篇 |
1998年 | 2833篇 |
1997年 | 2715篇 |
1996年 | 2661篇 |
1995年 | 2374篇 |
1994年 | 2409篇 |
1993年 | 2315篇 |
1992年 | 2641篇 |
1991年 | 2521篇 |
1990年 | 2464篇 |
1989年 | 2387篇 |
1988年 | 2350篇 |
1987年 | 2347篇 |
1986年 | 2218篇 |
1985年 | 2970篇 |
1984年 | 2998篇 |
1983年 | 2593篇 |
1982年 | 2781篇 |
1981年 | 2589篇 |
1980年 | 2536篇 |
1979年 | 2670篇 |
1978年 | 2683篇 |
1977年 | 2573篇 |
1976年 | 2672篇 |
1975年 | 2568篇 |
1974年 | 2534篇 |
1973年 | 2700篇 |
1972年 | 1717篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
931.
T. Riesterer J. G. Bednorz K. A. Müller B. Reihl 《Applied Physics A: Materials Science & Processing》1987,44(1):81-82
We have measured ultraviolet and inverse-photoemission spectra of the novel superconductor Sr02La1.8CuO4. Our results compare favorably with recent band-structure calculations for La2CuO4.A full account of this work will be published elsewhere [1] 相似文献
932.
Bruno Després 《Comptes Rendus Mathematique》2006,342(1):73-78
We describe a Weak Rankine Hugoniot relation for constrained discontinuous solutions of conservation laws. The constraint is convex in the primitive variable. Various examples show the potential interest of this approach. To cite this article: B. Després, C. R. Acad. Sci. Paris, Ser. I 342 (2006). 相似文献
933.
T. Gühne V. Gottschalch G. Leibiger H. Herrnberger J. Kovác J. Kovác Jr. R. Schmidt-Grund B. Rheinländer D. Pudis 《Laser Physics》2006,16(3):441-446
In this paper, we report on the design and optical properties of laser diodes with an emission wave-length of ~1170 nm based on an (InGa)As/GaAs double quantum well active layer. The back and front facet of the laser diodes were coated with SiOx dielectric films that influence the output optical power by enhancing or lowering the facet reflectivity. The measurements show improvement of the facet-coated laser diode properties in the threshold-current-density reduction along with light output power enhancement. Furthermore, a narrow far field pattern and high side mode suppression have been observed. 相似文献
934.
Jindun Liu A. J. B. Kemperman G. H. Koops M. Wessling 《中国颗粒学报》2006,4(2):98-102
A novel method of fabricating composite mosaic membranes was studied on the basis of interracial polymerization (IP) by coating a thin selective layer onto the surface of a micro-porous hollow-fiber membrane, in which, 2,5-diaminobenzene sulfonic acid was used as one monomer of the IP reaction, and a mixture of trimesoyl chloride (TMCI) and 4-(chloromethyl) benzoyl chloride as the other monomer. Through the IP reaction a thin selective layer with negatively charged groups could be first formed on the polyethersulfone (PES) support membrane. Then trimethylamine solution was introduced to modify the IP layer through a quaternization reaction. Thus the selective layer of this composite membrane contained both negatively charged and positively charged groups to perform the mosaic functionality. Characterization of the composite mosaic membranes was carried out through permeation experiments using different inorganic salts and dyes. The experimental results showed that the membranes could permeate both mono- and bi-valent inorganic salts, but reject larger organic molecules. Such a mosaic membrane is potentially useful for the separation of salts from water-soluble organics, especially in dye and textile industries. 相似文献
935.
L.B.Magalas 《物理学进展》2006,26(3):258-276
本文广泛地收集了有关内耗,力学谱,超声衰减方面的专著及会议文集。反映了20世纪在此领域的英文,俄文出版的书籍。也列出了历次国际会议及前苏联,乌克兰,中国的国内会议。文中包括了点缺陷,电,声子,位错,晶界,电畴等诸方面在内的内耗与力学谱工作。 相似文献
936.
Theoretical investigations and the results of computer modeling of the optical, thermophysical, and thermochemical processes during laser interaction with ocular tissues are reviewed in this paper. Physical-mathematical models and results of numerical simulation of the processes are presented. The computer modeling was applied for investigations of laser heating and coagulation of ocular tissues for treatment of retina diseases and intraocular tumors, cyclophotocoagulation of the ciliary body for treatment of glaucoma, and laser thermal keratoplasty of the cornea. The influence of radiation parameters on the selectivity of laser coagulation of laminated ocular tissues is considered. The results obtained are of essential interest for laser applications in ophthalmology and can be used for investigation of heating and coagulation of tissues in different fields of laser medicine. 相似文献
937.
We study experimentally the frequency dependences of the refractive index n and the absorption coefficient k of distilled,
sea, and river water. The measurements were performed using a quasioptical device with a backward-wave oscillator as the radiation
source and OAP-7 optical-acoustic receivers at a water temperature of 27°C in the cell. The quantities n and k were determined
from the measured transmission and reflection coefficients of the cell with water by means of joint numerical solution of
the equations for these quantities. For distilled water in the frequency range f = 75–120 GHz, we obtained n = 6.142–3.926
· 10–2f[GHz] + 1.307 · 10–4(f[GHz])2 and k = 3.607–2.101 · 10−2 f[GHz] + 5.252 · 10–5(f[GHz])2. On the whole, these data are in good agreement with the measurement results obtained by other authors at several frequencies
of the indicated range and coincide with the calculation data based on the models by Meissner and Wentz and by Liebe et al.
within the limits of the rms determination errors 0.05 and 0.02 for the parameters n and k, respectively. The values of n
and k for different seawater samples and river water containing insoluble admixtures coincide with the values of these quantities
for distilled water within the limits of the experimental measurement errors 3–5% and 1–2%, respectively. The dependences
n(f) and k(f) obtained experimentally for seawater are compared with those calculated on the basis of the developed models.
Measurements of the transmission spectrum of a cell with double distilled water were performed for low power density of radiation
(less than μW/cm2) to reproduce the effect of water resonant transparency reported many times in the literature. Our measurements did not reveal
any resonant features in the spectral behavior of the refractive index n and the absorption coefficient k of water and gave
the same result as for a power density exceeding the threshold of appearance of this effect.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 6, pp. 489–501, June 2006. 相似文献
938.
939.
E. N. Abdullin N. G. Ivanov B. M. Kovalchuk I. N. Konovalov V. F. Losev A. N. Panchenko Yu. N. Panchenko V. S. Skakun V. F. Tarasenko A. G. Yastremsky 《Laser Physics》2006,16(1):104-115
Two-high power excimer laser systems with square (25 × 25 cm) and circular (with a diameter of 40 cm) cross sections of the
output laser beam are described. The first (second) system consists of four (five) excimer lasers. The experimental results
on the generation of the high-quality high-power laser pulses are presented. Laser beams with a pulse duration of 1–250 ns,
a divergence of 0.01 mrad, a spectral line width of 0.01 cm−1, and a pulse energy of up to 330 J are obtained.
Original Text ? Astro, Ltd., 2006. 相似文献
940.
I. B. Samsonov 《Czechoslovak Journal of Physics》2006,56(10-11):1281-1286
We study the quantum properties of two theories with a non-anticommutative chiral singlet deformation ofN=(1, 1) supersymmetry: the Abelian model of a vector gauge multiplet and the model of a gauge multiplet interacting with a neutral hypermultiplet. Both these models are proved to be not only renormalizable but also finite. 相似文献