全文获取类型
收费全文 | 8554篇 |
免费 | 348篇 |
国内免费 | 86篇 |
专业分类
化学 | 5274篇 |
晶体学 | 83篇 |
力学 | 333篇 |
数学 | 1544篇 |
物理学 | 1754篇 |
出版年
2023年 | 53篇 |
2022年 | 130篇 |
2021年 | 197篇 |
2020年 | 200篇 |
2019年 | 215篇 |
2018年 | 206篇 |
2017年 | 187篇 |
2016年 | 298篇 |
2015年 | 233篇 |
2014年 | 349篇 |
2013年 | 587篇 |
2012年 | 556篇 |
2011年 | 613篇 |
2010年 | 359篇 |
2009年 | 399篇 |
2008年 | 480篇 |
2007年 | 409篇 |
2006年 | 348篇 |
2005年 | 307篇 |
2004年 | 303篇 |
2003年 | 254篇 |
2002年 | 258篇 |
2001年 | 182篇 |
2000年 | 171篇 |
1999年 | 102篇 |
1998年 | 87篇 |
1997年 | 90篇 |
1996年 | 116篇 |
1995年 | 93篇 |
1994年 | 78篇 |
1993年 | 86篇 |
1992年 | 65篇 |
1991年 | 64篇 |
1990年 | 57篇 |
1989年 | 56篇 |
1988年 | 45篇 |
1987年 | 62篇 |
1986年 | 65篇 |
1985年 | 69篇 |
1984年 | 57篇 |
1983年 | 54篇 |
1982年 | 52篇 |
1981年 | 50篇 |
1980年 | 35篇 |
1979年 | 49篇 |
1978年 | 43篇 |
1977年 | 38篇 |
1976年 | 44篇 |
1975年 | 37篇 |
1974年 | 28篇 |
排序方式: 共有8988条查询结果,搜索用时 15 毫秒
61.
Tumor cells transduced with herpes simplex virus thymidine kinase gene have been intensively applied to the field of positron emission tomography via imaging of its substrate. As a pilot synthesis approach, a facile preparation of 5‐[125I] iodoarabinosyl uridine starting from commercially available uridine is reported herein. 相似文献
62.
I. Tsiaoussis N. Frangis C. Manolikas T.A. Nguyen Tan 《Journal of Crystal Growth》2007,300(2):368-373
Pd thin films, grown on Si-rich 6H-SiC(0 0 0 1) substrates, were studied by atomic force microscopy, electron diffraction and high-resolution transmission electron microscopy. It is concluded that the growth is successful only when all the growth process takes place at room temperature. Under these conditions a very good epitaxial growth of Pd is achieved, despite the large misfit (about 8.6%) between Pd and the substrate and the existence of a semi-amorphous layer between the thin film and the substrate. A large number of twins appear in these films. 相似文献
63.
E.Y. Kang Yoon B. Kim K.Y. Kim Y.H. Chung H.K. Baik 《Journal of magnetism and magnetic materials》2006
FeSiBNb amorphous powder cores were prepared with the amorphous powder by gas atomization and subsequent hot pressing of resulting powder after creating oxide layers on the amorphous powder. Fully amorphous FeSiBNb powders with good soft magnetic properties were successfully obtained in the particle size range below 100 μm. FeSiBNb amorphous powder cores exhibit stable permeability up to 10 MHz, showing excellent high-frequency characteristics. 相似文献
64.
Hyeong Taek Ham Yeong Suk Choi Mu Guen Chee In Jae Chung 《Journal of polymer science. Part A, Polymer chemistry》2006,44(1):573-584
This work is to make carbon nanotubes dispersible in both water and organic solvents without oxidation and cutting nanotube threads. Polystyrene‐singlewall carbon nanotube (PS‐SWNT) composites were prepared with three different methods: miniemulsion polymerization, conventional emulsion polymerization, and mixing SWNT with PS latex. The two factors, crosslinking and surface coverage of PS are important factors for the mechanical and electrical properties, including dispersion states of SWNT in various solvents. The PS‐SWNT composite prepared via a conventional emulsion polymerization showed SWNT bundles entirely covered with PS, whereas the PS‐SWNT composite prepared via a miniemulsion polymerization showed SWNT partially covered with crosslinked PS nanoparticles. The method of mixing SWNTs with PS latex did not show the well dispersed state of carbon nanotubes because PS was not crosslinked and was dissolved in a solvent, and nanotubes separated from PS precipitated. So the PS nanoparticle‐SWNT composite had lower electrical resistance, and higher mechanical strength than the other composites made by the latter two methods. As the amount of SWNT increases, the bare surface area of SWNT increases and the electrical conductivity increases in the composite made by the miniemulsion polymerization. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 573–584, 2006 相似文献
65.
Anisha Gokarna Yong Hwan Kim Yong-Hoon Cho Min Su Lee In Cheol Kang Hyun Kyu Park Min Gon Kim Bong Hyun Chung 《Optical Review》2006,13(4):288-291
We demonstrate the fluorescence mapping of protein microarrays by the technique of scanning near-field optical microscopy
(SNOM) and confocal microscopy. Micron sized spots (300 μm) of human Immunoglobulin G (hIgG) protein with and without a Cy3
dye labeling have been fabricated on glass substrates by an immobilization method which makes use of calixcrown derivatives
termed Prolinker. We have also tried to probe into the well-known “doughnut effect” observed in fluorescence images of proteins
using the SNOM technique. The topographic and fluorescence SNOM images revealed that the number of proteins at the boundary
of the spot were more than at the center in the case of the microarray spot which showed brighter luminescence at the edge
than at the center in the confocal image. 相似文献
66.
The maximal hypoellipticity of the operator X
1
2m
, ... X
k
2m
is proved, where Xj are first-order pseudodifferential operators and m is a natural number. It is assumed that the set of these operators and
their first-order commutators is an elliptic system. The results obtained generalize the well-known results of Hormander,
Oleinik, and Radkevich, Kohn, Helffer, and Nourrigat, and Rothshield and Stein. Bibliography: 9 titles.
Translated from Trudy Seminara imeni I. G. Petrovskogo, No. 17, pp. 3–26, 1994. 相似文献
67.
68.
Bonner BE Buchanan JA Clement JM Corcoran MD Krishna NM Kruk JW Miettinen HE Moss RM Mutchler GS Nessi-Tedaldi F Nessi M Phillips GC Roberts JB Stevenson PM Tonse SR Birman A Chung SU Etkin A Fernow RC Kirk H Protopopescu SD Willutzki H Hallman T Madansky L Bar-Yam Z Dowd J Kern W King E Mayes BW Pinsky LS 《Physical review D: Particles and fields》1990,41(1):13-16
69.
Continuous scanning of a 1 GHz pulsed laser line using only one 5-cm grating as an intracavity selective element is obtained from a pulsed dye laser pumped by a Nd: YAG (8 ns-532 nm) laser. Such a single-grating dye laser operates in the same way as a real double-grating grazing incidence laser and provides an appreciable improvement of the resolution (enhancement factor 2), compared with previous grazing incidence ones. The superiority of this laser cavity has been proved for single-longitudinal-mode operation.Laboratoire associé à l'Université de Paris-Sud 相似文献
70.
We introduce a class of optimization problems, calleddynamic location problems, involving the processing of requests that occur sequentially at the nodes of a graphG. This leads to the definition of a new parameter of graphs, called the window indexWX(G), that measures how large a window into the future is needed to solve every instance of the dynamic location problem onG optimally on-line. We completely characterize this parameter:WX(G)k if and only ifG is a weak retract of a product of complete graphs of size at mostk. As a byproduct, we obtain two (polynomially recognizable) structural characterizations of such graphs, extending a result of Bandelt. 相似文献