全文获取类型
收费全文 | 3036篇 |
免费 | 82篇 |
国内免费 | 10篇 |
专业分类
化学 | 2286篇 |
晶体学 | 34篇 |
力学 | 34篇 |
数学 | 143篇 |
物理学 | 631篇 |
出版年
2022年 | 13篇 |
2021年 | 17篇 |
2020年 | 37篇 |
2019年 | 48篇 |
2018年 | 37篇 |
2017年 | 18篇 |
2016年 | 57篇 |
2015年 | 46篇 |
2014年 | 66篇 |
2013年 | 146篇 |
2012年 | 144篇 |
2011年 | 171篇 |
2010年 | 102篇 |
2009年 | 87篇 |
2008年 | 151篇 |
2007年 | 147篇 |
2006年 | 143篇 |
2005年 | 144篇 |
2004年 | 121篇 |
2003年 | 132篇 |
2002年 | 121篇 |
2001年 | 84篇 |
2000年 | 85篇 |
1999年 | 52篇 |
1998年 | 33篇 |
1997年 | 36篇 |
1996年 | 39篇 |
1995年 | 27篇 |
1994年 | 32篇 |
1993年 | 41篇 |
1992年 | 37篇 |
1991年 | 46篇 |
1990年 | 48篇 |
1989年 | 32篇 |
1988年 | 43篇 |
1987年 | 43篇 |
1986年 | 35篇 |
1985年 | 60篇 |
1984年 | 43篇 |
1983年 | 22篇 |
1982年 | 34篇 |
1981年 | 35篇 |
1980年 | 22篇 |
1979年 | 34篇 |
1978年 | 33篇 |
1977年 | 41篇 |
1976年 | 31篇 |
1975年 | 22篇 |
1974年 | 17篇 |
1973年 | 21篇 |
排序方式: 共有3128条查询结果,搜索用时 765 毫秒
211.
Pulsed laser deposition of iron atoms on graphite substrates was performed to produce iron carbide films. Mössbauer spectra of the sample revealed that iron carbide was produced on the substrate surface and that an α-Fe layer was produced above the iron carbide layer. When the substrate temperature was maintained at 300 K, the iron carbide layer had a hyperfine magnetic distribution because it contained high density of defects. Laser deposition of Fe at 570 K produced cementite Fe3C with fewer defects due to enhancement of thermal reactions or annealing of the films. The orientation of hyperfine field of the Fe3C film was parallel to the substrate surface. 相似文献
212.
Senoy Thomas D. Sakthikumar Yasuhiko Yoshida M. R. Anantharaman 《Journal of nanoparticle research》2008,10(1):203-206
Sol–gel glasses with Fe3O4 nanoparticles having particle sizes laying in the range 10–20 nm were encapsulated in the porous network of silica resulting
in nanocomposites having both optical and magnetic properties. Spectroscopic and photoluminescence studies indicated that
Fe3O4 nanocrystals are embedded in the silica matrix with no strong Si–O–Fe bonding. The composites exhibited a blue luminescence.
The optical absorption edge of the composites red shifted with increasing concentration of Fe3O4 in the silica matrix. There is no obvious shift in the position of the luminescence peak with the concentration of Fe3O4 except that the intensity of the peak is decreased. The unique combinations of magnetic and optical properties are appealing
for magneto–optical applications. 相似文献
213.
214.
Watanabe S Sonobe M Arai M Tazume Y Matsuo T Nakamura T Yoshida K 《Chemical communications (Cambridge, England)》2002,(23):2866-2867
A gold nanoparticle surface-modified with amide ligands shows enhanced optical sensing of anions: the detection limit is increased by about three orders of magnitude higher than that originally expected from the anion binding ability of neutral amide ligands. 相似文献
215.
[structure: see text] 8,11-Dideoxytetrodotoxin, an unnatural tetrodotoxin analogue, was synthesized in a highly stereoselective manner from a common intermediate in our synthetic studies on tetrodotoxin. The synthesis features neighboring group participation of trichloroacetamide for stereoselective hydroxylation, protection of ortho ester, and guanidine installation with Boc-protected isothiourea. 相似文献
216.
Yoshida R Sakai T Ito S Yamaguchi T 《Journal of the American Chemical Society》2002,124(27):8095-8098
Self-oscillation of polymer chains in an aqueous solution has been achieved. The ruthenium catalyst for the Belousov-Zhabotinsky reaction was polymerized by using N-isopropylacrylamide and dissolved into the solution containing the BZ substrates. Periodical soluble-insoluble changes of the polymer chain were spontaneously induced by the BZ reaction. The conformational oscillations of the polymer were measured as the optical transmittance changes of the solution. This is the first report that rhythmical and reversible soluble-insoluble changes of polymer chains are realized under constant and homogeneous conditions. The transducing system from chemical energy of the BZ reaction to optical information has been constructed. 相似文献
217.
Polymer-mediated extraction based on thermoresponsive precipitation of poly(N-isopropylacrylamide) [PNIPAAm] was applied to the concentration of amphiphilic compounds, nonylphenyl polyethoxylates (NPnEOs), in water. Among these nonionic surfactants, NPnEOs possessing the number, n, of ethoxy unit less than 5 were quantitatively recovered in polymer precipitates when a 0.100-g portion of PNIPAAm was used for a 10 ml sample solution. Torelance limit (30 ppm) against a typical industrial anionic surfactant, sodium dodecylsulfate, strongly suggests the potential to use the present method for practical purposes. After preconcentration, trace nonylphenol and mono-ethoxylated nonylphenol (ppb-level) in a river water sample were successfully determined by high-performance liquid chromatography with ultra-violet photometric detection. 相似文献
218.
Takahashi Y Tomura M Yoshida Ki Murata S Tomioka H 《Angewandte Chemie (International ed. in English)》2000,39(19):3478-3480
219.
220.
Iyoda M Kondo T Nakao K Hara K Kuwatani Y Yoshida M Matsuyama H 《Organic letters》2000,2(14):2081-2083
1,8-[1,8-Naphthalenediylbis(4',4-biphenyldiyl)]naphthalene, a very stable strained cyclophane, has been synthesized in moderate yield using the copper-catalyzed coupling of 1, 8-bis(4-(tributylstannyl)phenyl)naphthalene. The X-ray analysis of the titled compound discloses bent p,p'-biphenylylene chains with splayed naphthalene rings, and the p,p'-biphenylylene chains located face-to-face indicate a fairly strong pi-pi interaction. 相似文献