全文获取类型
收费全文 | 1803篇 |
免费 | 46篇 |
国内免费 | 7篇 |
专业分类
化学 | 1426篇 |
晶体学 | 29篇 |
力学 | 20篇 |
数学 | 122篇 |
物理学 | 259篇 |
出版年
2022年 | 8篇 |
2021年 | 18篇 |
2019年 | 21篇 |
2018年 | 13篇 |
2016年 | 22篇 |
2015年 | 20篇 |
2014年 | 30篇 |
2013年 | 67篇 |
2012年 | 76篇 |
2011年 | 87篇 |
2010年 | 57篇 |
2009年 | 37篇 |
2008年 | 78篇 |
2007年 | 95篇 |
2006年 | 102篇 |
2005年 | 113篇 |
2004年 | 84篇 |
2003年 | 60篇 |
2002年 | 89篇 |
2001年 | 14篇 |
2000年 | 25篇 |
1999年 | 28篇 |
1998年 | 28篇 |
1997年 | 20篇 |
1996年 | 28篇 |
1995年 | 25篇 |
1994年 | 16篇 |
1993年 | 26篇 |
1992年 | 17篇 |
1991年 | 14篇 |
1990年 | 12篇 |
1989年 | 15篇 |
1988年 | 19篇 |
1987年 | 21篇 |
1986年 | 18篇 |
1985年 | 38篇 |
1984年 | 40篇 |
1983年 | 27篇 |
1982年 | 32篇 |
1981年 | 30篇 |
1980年 | 23篇 |
1979年 | 28篇 |
1978年 | 31篇 |
1977年 | 26篇 |
1976年 | 36篇 |
1975年 | 27篇 |
1974年 | 25篇 |
1973年 | 26篇 |
1972年 | 11篇 |
1971年 | 9篇 |
排序方式: 共有1856条查询结果,搜索用时 31 毫秒
101.
Helical Carbon and Graphite Films Prepared from Helical Poly(3,4‐ethylenedioxythiophene) Films Synthesized by Electrochemical Polymerization in Chiral Nematic Liquid Crystals 下载免费PDF全文
Dr. Satoshi Matsushita Bairu Yan Shinsuke Yamamoto Dr. Yong Soo Jeong Prof. Kazuo Akagi 《Angewandte Chemie (International ed. in English)》2014,53(6):1659-1663
Helical carbon and graphite films from helical poly(3,4‐ethylenedioxythiophene) (H‐PEDOT) films synthesized through electrochemical polymerization in a chiral nematic liquid‐crystal (N*‐LC) field are prepared. The microscope investigations showed that the H‐PEDOT film synthesized in the N*‐LC has large domains of one‐handed spiral morphology consisting of fibril bundles. The H‐PEDOT films exhibited distinct Cotton effects in circular dichroism spectra. The highly twisted N*‐LC with a helical pitch of smaller than 1 μm produced the H‐PEDOT film with a highly ordered morphology. The spiral morphologies with left‐ and right‐handed screws were observed for the carbon films prepared from the H‐PEDOT films at 800 °C and were well correlated with the textures and helical pitches of the N*‐LCs. The spiral morphologies of the precursors were also retained even in the graphite films prepared from the helical carbon films at 2600 °C. 相似文献
102.
Osamu Takimura Hiroyuki Fuse Katsuzi Murakami Kazuo Kamimura Yukiho Yamaoka 《应用有机金属化学》1996,10(9):753-756
Uptake and reduction of arsenate [AS(V)] by Dunaliella sp. cells were determined to investigate the metabolic processes of arsenic in the alga. Cellular uptake of arsenic by Dunaliella sp. cells was markedly affected by the form of arsenic in the medium. The content of arsenic taken up by Dunaliella sp. cells increased rapidly with time on addition of As(V) to the medium. However, in the case of addition of arsenite [As(III)], the gradient of arsenic uptake by Dunaliella sp. cells was low, and arsenic content was small. In the water-soluble fraction of arsenic taken up by Dunaliella sp. cells with exposure to As(V), arsenic was in the forms of organic arsenic, As(V) and As(III). The content of As(V) in the water-soluble fraction increased with exposure time. The content of As(III) also increased with time, but remained constant after 5 h of exposure. On the other hand, organic arsenic content was small and did not increase with time. It was found that Dunaliella sp. takes up As(V) and readily reduces it to As(III) 相似文献
103.
Preparation of monodispersed polymer-modified colloidal silica particles of less than 50 nm diameter
The preparation of monodisperse, ultrafine polymermodified colloidal silica, 11 or 42 nm in diameter, were studied. The reaction of the colloidal silica with polymeric silane coupler in 1,2-dimethoxyethane and removal of the unreacted polymer with granular silica gel (10–20 mesh) in acetone gave a suspension of monodisperse composite particles. 相似文献
104.
105.
Shigeyoshí Nishino Yasuhiro Nagato Yoshihiro Hasegawa Hisanao Yamamoto Kazuo Kamaike Yoshiharu Ishido 《Heteroatom Chemistry》1991,2(1):187-196
Reagent systems of sodium– and tetrabutylammonium nitrite–acetic anhydride were proved to be extremely efficient for the deanilidation of nucleoside 3′-phosphoranilidates, whose reactions were rapid with the former and instant with the latter. It was further found that the reagent system is applicable to oligonucleotide synthesis provided that the exocyclic amino groups of 2′-deoxyadenosine, 2′-deoxyguanosine, and 2′-deoxycytidine were protected by succinylation. 相似文献
106.
Kazuo Araki Takashi Kato Uday Kumar Jean M. J. Frchet 《Macromolecular rapid communications》1995,16(10):733-739
The dielectric properties of a hydrogen-bonded side-chain liquid-crystalline polysiloxane have been examined over wide ranges of frequency and temperature. This polymer has a side-chain mesogenic moiety consisting of a benzoic acid and a stilbazole. The observed dielectric loss curves contain a component from dipole reorientation of the hydrogen-bonded mesogenic group. It has been found to be possible that, using electrical and thermal treatments, such a polymer built through hydrogen bonding can align homeotropically. 相似文献
107.
108.
Prof. Dr. Masahiro Sadakane Sachie Moroi Yoshifumi Iimuro Dr. Natalya Izarova Prof. Dr. Ulrich Kortz Prof. Dr. Shinjiro Hayakawa Kazuo Kato Dr. Shuhei Ogo Dr. Yusuke Ide Prof. Dr. Wataru Ueda Prof. Dr. Tsuneji Sano 《化学:亚洲杂志》2012,7(6):1331-1339
Ruthenium(III)‐substituted α‐Keggin‐type silicotungstates with pyridine‐based ligands, [SiW11O39RuIII(Py)]5?, (Py: pyridine ( 1 ), 4‐pyridine‐carboxylic acid ( 2 ), 4,4′‐bipyridine ( 3 ), 4‐pyridine‐acetamide ( 4 ), and 4‐pyridine‐methanol ( 5 )) were prepared by reacting [SiW11O39RuIII(H2O)]5? with the pyridine derivatives in water at 80 °C and then isolated as their hydrated cesium salts. These compounds were characterized using cyclic voltammetry (CV), UV/Vis, IR, and 1H NMR spectroscopy, elemental analysis, titration, and X‐ray absorption near‐edge structure (XANES) analysis (Ru K‐edge and L3‐edge). Single‐crystal X‐ray analysis of compounds 2 , 3 , and 4 revealed that RuIII was incorporated in the α‐Keggin framework and was coordinated by pyridine derivatives through a Ru? N bond. In the solid state, compounds 2 and 3 formed a dimer through π? π interaction of the pyridine moieties, whereas they existed as monomers in solution. CV indicated that the incorporated RuIII–Py was reversibly oxidized into the RuIV–Py derivative and reduced into the RuII–Py derivative. 相似文献
109.
Speciation of arsenic in body fluids 总被引:1,自引:0,他引:1
Inorganic arsenic is metabolized by consecutive reduction and methylation reactions to dimethylated arsenic (DMA), and then excreted into the urine mostly in the form of DMA. Therefore, arsenic metabolites in the body fluids and organs/tissues are present in the form of inorganic (arsenite and arsenate) and methylated arsenics (MMA and DMA). Although pentavalent arsenics can be present mostly in the form of free ions, trivalent ones may be present more in the forms conjugated with thiol groups of glutathione (GSH) or proteins. Arsenic in the body fluids (plasma, bile and urine) is present in the soluble forms and can be speciated on ion exchange columns by HPLC with on-line detection by an inductively coupled argon plasma-mass spectrometer (ICP-MS). Free forms of arsenite, arsenate, and monomethylarsonous, monomethylarsonic, dimethylarsinous and dimethylarsinic acids in the body fluids have been demonstrated to be speciated simultaneously within 10 min or so on both anion and cation exchange columns together with arsenobetaine (AsB) and arsenocholine (AsC). Trivalent arsenics conjugated with GSH were eluted in intact forms on an anion exchange column but were liberated into free forms on a cation exchange column. Thus, free and GSH-conjugated arsenic metabolites in the bile and urine have been speciated simultaneously on ion exchange columns by HPLC-ICP-MS. 相似文献
110.
0Introduction Anelectronicpackageisgenerallyconstructedwithanactivesiliconchip,mountisland,gold wires,leadframesandsoldersasshowninFig.1(a).Toprotectfromtheenvironment,thesilicon chipisusuallyencapsulatedinresin.SincethesematerialshavedifferentCTE(coeffic… 相似文献