全文获取类型
收费全文 | 1837篇 |
免费 | 32篇 |
国内免费 | 22篇 |
专业分类
化学 | 1492篇 |
晶体学 | 14篇 |
力学 | 16篇 |
数学 | 80篇 |
物理学 | 289篇 |
出版年
2022年 | 9篇 |
2021年 | 22篇 |
2020年 | 20篇 |
2019年 | 15篇 |
2018年 | 17篇 |
2017年 | 11篇 |
2016年 | 21篇 |
2015年 | 15篇 |
2014年 | 30篇 |
2013年 | 60篇 |
2012年 | 95篇 |
2011年 | 97篇 |
2010年 | 62篇 |
2009年 | 73篇 |
2008年 | 108篇 |
2007年 | 109篇 |
2006年 | 117篇 |
2005年 | 132篇 |
2004年 | 116篇 |
2003年 | 101篇 |
2002年 | 90篇 |
2001年 | 29篇 |
2000年 | 17篇 |
1999年 | 31篇 |
1998年 | 31篇 |
1997年 | 21篇 |
1996年 | 35篇 |
1995年 | 20篇 |
1994年 | 11篇 |
1993年 | 11篇 |
1992年 | 16篇 |
1991年 | 16篇 |
1990年 | 6篇 |
1989年 | 16篇 |
1988年 | 15篇 |
1987年 | 14篇 |
1986年 | 7篇 |
1985年 | 21篇 |
1984年 | 25篇 |
1983年 | 9篇 |
1982年 | 25篇 |
1981年 | 25篇 |
1980年 | 14篇 |
1979年 | 22篇 |
1978年 | 18篇 |
1977年 | 23篇 |
1976年 | 15篇 |
1975年 | 14篇 |
1974年 | 14篇 |
1973年 | 14篇 |
排序方式: 共有1891条查询结果,搜索用时 109 毫秒
271.
272.
The effect of oxidant species forming an alcohol molecule for hot-filament chemical vapor deposition (HFCVD) on single-walled carbon nanotubes (SWCNTs) growth has been investigated. To use a graphite rod as a filament for HFCVD to decompose alcohol sources, contamination-free sample surface can be obtained and SWCNTs are successively and densely grown at a lower temperature than those by conventional thermal CVD. It is found that the higher the molecule number of alcohol among CH3OH, C2H5OH, and 2-C3H7OH is, the lower the initial growth rate of SWCNTs is. As for CH3OH, diameter distribution of SWCNTs is dynamically changed with the growth time passed, and a negative growth rate is observed at the later stage of growth. The growth kinetics depending on the alcohol sources is discussed on the basis of a capability of the oxidant species to burn away SWCNTs and deactivation of Co catalysts used for the growth. 相似文献
273.
Masahiro Yamazaki Osamu Nakatsuka Akira Sakai Shigeaki Zaima 《Applied Surface Science》2008,254(19):6048-6051
We have investigated the initial growth of Sn and Ge1−xSnx layers on Ge(0 0 1) surface by using scanning tunneling microscopy. After the growth of a 0.035 ML-thick Sn layer at room temperature, Sn clusters lining vertically to a dimer row was observed. In the case of the 0.035-0.018 ML-thick Sn growth at 250 °C, the characteristic surface reconstruction with the step-edge undulation like a comb was observed. In the growth of a Ge0.994Sn0.006 layer at 250 °C, the multilayer polynuclear growth with a lot of two-dimensional small domain was observed. These surface reconstructions should be accounted for by the large compressive stress induced in the surface layer due to the incorporation of Sn atoms. 相似文献
274.
Jun-ichi Nishizawa Tetsuo Sasaki Ken Suto Masahiko Ito Takashi Yoshida Tadao Tanabe 《International Journal of Infrared and Millimeter Waves》2008,29(3):291-297
We developed high-resolution GaP THz signal generator using Cr:Forsterite lasers with gratings as both a pump and a signal
beam for difference-frequency generation. A line width of less than 500 MHz and a wide tunable frequency range (0.6–6.2 THz)
provide sufficient resolution for measuring materials with sharp absorption bands using the generator as the light source
for a THz spectrometer. This is suitable for materials such as gases or solid samples at low temperatures. We demonstrated
the detection of defects in organic materials, as they appear as slight deviations in the absorption frequency in the THz
region. 相似文献
275.
Anna V. Klassen Makoto Matsukura Osamu Nakamura Vladimir V. Kochurikhin Mikhail A. Ivanov Galina Yu. Orlova Akio Miyamoto Yasunori Furukawa 《Journal of Crystal Growth》2008,310(11):2895-2898
The applicability of the edge-defined film-fed growth (EFG) technique for YbxY(1−x)VO4 (x=0.05, 0.1 and 1) was approved by successful growth of crystals up to 80 mm in length as the thin plates. Low-angle grain boundaries and the crystal coloration as main defects were found. Optimal seed orientation was suggested on the strength of vanadate crystal plate morphology. Optical properties, chemical composition and the crystalline quality were investigated. 相似文献
276.
Feng Cheng Shuqi Wu Wenwei Zheng Shengqun Su Takumi Nakanishi Wenhuang Xu Pritam Sadhukhan Hibiki Sejima Shimon Ikenaga Kaoru Yamamoto Kaige Gao Shinji Kanegawa Prof. Osamu Sato 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(59):e202202161
The crystallization of a complex having electron transfer properties in a polar space group can induce the polarization switching of a crystal in a specific direction, which is attractive for the development of sensors, memory devices, and capacitors. Unfortunately, the probability of crystallization in a polar space group is usually low. Noticing that enantiopure compounds crystallize in Sohncke space groups, this paper reports a strategy for the molecular design of non-ferroelectric polarization switching crystals based on the use of intramolecular electron transfer and chirality. In addition, this paper describes the synthesis of a mononuclear valence tautomeric (VT) cobalt complex bearing an enantiopure ligand. The introduction of enantiomer enables the crystallization of the complex in the polar space group (P21). The polarization of the crystals along the b-axis direction is not canceled out and the VT transition is accompanied by a change in the macroscopic polarization of the polar crystal. Polarization switching via electron transfer is realized at around room temperature. 相似文献
277.
Kanna Adachi Tomoshi Yamada Hayate Ishizuka Mana Oki Shunsuke Tsunogae Noriko Shimada Osamu Chiba Tatsuya Orihara Prof. Dr. Masafumi Hidaka Prof. Dr. Takatsugu Hirokawa Dr. Minami Odagi Prof. Dr. Keiichi Konoki Prof. Dr. Mari Yotsu-Yamashita Prof. Dr. Kazuo Nagasawa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(9):2025-2033
A novel series of C12-keto-type saxitoxin (STX) derivatives bearing an unusual nonhydrated form of the ketone at C12 has been synthesized, and their NaV-inhibitory activity has been evaluated in a cell-based assay as well as whole-cell patch-clamp recording. Among these compounds, 11-benzylidene STX ( 3 a ) showed potent inhibitory activity against neuroblastoma Neuro 2A in both cell-based and electrophysiological analyses, with EC50 and IC50 values of 8.5 and 30.7 nm , respectively. Interestingly, the compound showed potent inhibitory activity against tetrodotoxin-resistant subtype of NaV1.5, with an IC50 value of 94.1 nm . Derivatives 3 a – d and 3 f showed low recovery rates from NaV1.2 subtype (ca 45–79 %) compared to natural dcSTX ( 2 ), strongly suggesting an irreversible mode of interaction. We propose an interaction model for the C12-keto derivatives with NaV in which the enone moiety in the STX derivatives 3 works as Michael acceptor for the carboxylate of Asp1717. 相似文献
278.
Dr. Hiromichi Nakahara Dr. Marie Pierre Krafft Prof. Osamu Shibata 《Chemphyschem》2020,21(17):1966-1970
We found that monolayers of dipalmitoylphosphatidylcholine (DPPC) and semi-fluorinated tetrablock di(F10H16) self-assemble to form a new type of large, complex flower-like patterns on the surface of water and on solid substrates. The hierarchical organization of these unusual self-assemblies was investigated using compression and surface potential isotherms, in situ fluorescence and Brewster angle microscopies, and atomic force microscopy after transfer. 相似文献
279.
280.
Donglin Fu Xuemin Rao Jinyi Xu Genzoh Tanabe Osamu Muraoka Xiaoming Wu Weijia Xie 《Tetrahedron letters》2018,59(30):2876-2879
The first total syntheses of naturally occurring cyclodepsipeptides Hikiamides A–C are described. The key linear pentapeptide precursors, prepared efficiently via Fmoc-solid-phase synthesis, were cyclized in dilute solution to provide the target Hikiamides A–C. The structures of the synthetic Hikiamides A–C were characterized by NMR and HRMS spectroscopy which were in agreement with those of natural products. 相似文献