全文获取类型
收费全文 | 18668篇 |
免费 | 700篇 |
国内免费 | 90篇 |
专业分类
化学 | 12032篇 |
晶体学 | 270篇 |
力学 | 441篇 |
综合类 | 1篇 |
数学 | 3341篇 |
物理学 | 3373篇 |
出版年
2023年 | 116篇 |
2022年 | 207篇 |
2021年 | 321篇 |
2020年 | 346篇 |
2019年 | 427篇 |
2018年 | 361篇 |
2017年 | 392篇 |
2016年 | 794篇 |
2015年 | 599篇 |
2014年 | 709篇 |
2013年 | 1349篇 |
2012年 | 1029篇 |
2011年 | 1125篇 |
2010年 | 795篇 |
2009年 | 708篇 |
2008年 | 1073篇 |
2007年 | 1056篇 |
2006年 | 858篇 |
2005年 | 836篇 |
2004年 | 692篇 |
2003年 | 539篇 |
2002年 | 500篇 |
2001年 | 281篇 |
2000年 | 263篇 |
1999年 | 176篇 |
1998年 | 196篇 |
1997年 | 166篇 |
1996年 | 186篇 |
1995年 | 168篇 |
1994年 | 133篇 |
1993年 | 134篇 |
1992年 | 123篇 |
1991年 | 145篇 |
1990年 | 121篇 |
1989年 | 123篇 |
1988年 | 108篇 |
1987年 | 110篇 |
1986年 | 120篇 |
1985年 | 216篇 |
1984年 | 218篇 |
1983年 | 151篇 |
1982年 | 137篇 |
1981年 | 157篇 |
1980年 | 141篇 |
1979年 | 118篇 |
1978年 | 111篇 |
1977年 | 82篇 |
1976年 | 84篇 |
1975年 | 89篇 |
1974年 | 88篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
Michal Johanis Jan Rychtá r 《Proceedings of the American Mathematical Society》2007,135(5):1511-1514
It is shown that every separable Banach space admits an equivalent norm that is uniformly Gâteaux smooth and yet lacks asymptotic normal structure.
83.
Physical aspects of an operation of the GaAs-based InGaAs/GaAs quantum-well (QW) VCSELs with the intentionally detuned optical
cavities have been considered in the present paper using the comprehensive three-dimensional self-consistent optical–electrical–thermal-gain
simulation. In GaAs-based structures, very good DBR resonator mirrors and a very efficient methods to confine radially both
the current spreading and the electromagnetic field with the aid of oxide apertures may be applied. It has been found using
the above simulation that even currently available immature technology enables manufacturing the above devices emitting radiation
of wavelengths over 1.20 μm. In particular, while the room-temperature 1.30-μm lasing emission is still beyond possibilities
of the InGaAs/GaAs QW VCSELs, these structures may offer analogous 1.25-μm emission, especially for the high-power and/or
high-temperature operation. 相似文献
84.
We study interpolation, generated by an abstract method of means, of bilinear operators between quasi-Banach spaces. It is
shown that under suitable conditions on the type of these spaces and the boundedness of the classical convolution operator
between the corresponding quasi-Banach sequence spaces, bilinear interpolation is possible. Applications to the classical
real method spaces, Calderón-Lozanovsky spaces, and Lorentz-Zygmund spaces are presented.
The author is supported by the National Science Foundation under grant DMS 0099881.
The author is supported by KBN Grant 1 P03A 013 26. 相似文献
85.
6-Thia-l-aza-5λ5-phosphabicyclo[3.2.0]hept-3-enes and Isothiocyanatophosphine-sulfides from (Methylidenamino)phosphines, Carbon Disulfide, and Acetylene- or Ethylene Derivatives (Methylidenamino)phosphines react with carbon disulfide to 1,3,2-thiazaphosphete derivatives 2 . Acetylenedicarboxylates give with 2 6-thia-l-aza-5λ5-phosphabicyclo[3.2.0]hept-3-enes 4a , b , and acrylates yield isothio-cyanatophosphin-sulfides 5a – c . The structures of 4a and 5a are proven by an X-ray diffraction analysis. 相似文献
86.
G. Michałek B.R. Bułka 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(1):121-128
The currents and their fluctuations in two capacitively coupled single electron transistors are determined in the limit of
sequential tunnelling. Our considerations are restricted to the case when the islands (dots) of the transistors are atomic-sized,
which means each of them has only one single electronic level available for the tunnelling processes. The Coulomb interactions
of accumulated charges on the both single electron transistors lead to the effect of the negative differential resistance.
An enhancement of the current shot-noise was also found. Spectral decomposition analysis indicated the two main contributions
to the shot-noise: low- and high-frequency fluctuations. It was found that the low frequency fluctuations (polarization noise)
are responsible for a strong enhancement of the current noise.
Received 9 October 2001 / Received in final form 8 March 2002 Published online 9 July 2002 相似文献
87.
88.
89.
90.
Boena N. Kolarz Maria Wojaczyska Jan Kaczmarczyk Teresa Siemieniewska Kazimierz Tomkw 《Journal of Polymer Science.Polymer Physics》1994,32(12):1977-1990
Sulfonic cation exchangers with two ion exchange group concentrations (0.5 and 2.4 mmol/g, samples A and B, respectively) were obtained by sulfonation of a porous styrene (S) and divinylbenzene (DVB) copolymer with chlorosulfonic acid. Strong thermal decomposition of the sulfonated copolymer A, accompanied by significant changes in its porous structure, starts at ca. 400°C. The char has no sulfonic groups. After heat treatment at 400°C in steam, a sorbent was obtained (yield 65%) that shows higher phenol sorption than the untreated sample when related to the bed volume. The chlorosulfonic derivatives of the initial copolymer were less thermally resistant than the sulfonic ones obtained by hydrolysis. Pyrolysis of the cation exchanger B, in its H+ and Ca2+ forms, was carried out at 900°C (yield of both chars close to 30%). By subsequent steam activation at 800°C to a 50% burn-off of the char, sorbents with well-developed, but distinctly different, porous structures were obtained. The activated char from the sulfonated copolymer in its hydrogen form was highly microporous and indicated an effective surface area of 1180 m2/g. However, because of a low contribution of mesopores, its ability to adsorb phenol from the liquid phase was not very high. The activated char from the calcium-doped copolymer, indicating a smaller surface area (580 m2/g) but characterized by a well-developed mesoporosity, was a better sorbent for phenol. © 1994 John Wiley & Sons, Inc. 相似文献