全文获取类型
收费全文 | 619篇 |
免费 | 19篇 |
国内免费 | 2篇 |
专业分类
化学 | 525篇 |
晶体学 | 4篇 |
力学 | 4篇 |
数学 | 23篇 |
物理学 | 84篇 |
出版年
2022年 | 3篇 |
2021年 | 11篇 |
2020年 | 15篇 |
2019年 | 16篇 |
2018年 | 4篇 |
2017年 | 4篇 |
2016年 | 10篇 |
2015年 | 8篇 |
2014年 | 16篇 |
2013年 | 18篇 |
2012年 | 44篇 |
2011年 | 38篇 |
2010年 | 15篇 |
2009年 | 17篇 |
2008年 | 32篇 |
2007年 | 44篇 |
2006年 | 51篇 |
2005年 | 47篇 |
2004年 | 34篇 |
2003年 | 24篇 |
2002年 | 39篇 |
2001年 | 11篇 |
2000年 | 10篇 |
1999年 | 9篇 |
1998年 | 7篇 |
1997年 | 12篇 |
1996年 | 7篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 11篇 |
1990年 | 3篇 |
1989年 | 9篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 8篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1943年 | 2篇 |
1929年 | 2篇 |
排序方式: 共有640条查询结果,搜索用时 15 毫秒
61.
Yousuke Konno Hiroto Kudo Atsushi Kameyama Tadatomi Nishikubo 《Journal of polymer science. Part A, Polymer chemistry》2004,42(10):2543-2550
Fluorine‐containing polyethers with pendant hydroxyl groups were synthesized by the polyaddition of fluorine‐containing bis(epoxide)s with certain fluorine‐containing diols with quaternary onium salts as catalysts. When the polyaddition was performed with 2,2′,6,6′‐tetrafluoro‐4,4′‐biphenol diglycidiyl ether and 2,2′,6,6′‐tetrafluoro‐4,4′‐biphenol, the corresponding polyether with pendant hydroxyl groups was successfully obtained in good yield. The polyaddition of certain fluorine‐containing bis(epoxide)s with diols also proceeded in bulk to provide the corresponding fluorine‐containing polyethers with high molecular weights. These polyethers were highly transparent at 157 nm for 0.1 μm thickness, with their transmittance of 14–75% at 157 nm. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2543–2550, 2004 相似文献
62.
63.
64.
Ryo Nozawa Keitaro Yamamoto Prof. Dr. Ji‐Young Shin Prof. Dr. Satoru Hiroto Prof. Dr. Hiroshi Shinokubo 《Angewandte Chemie (International ed. in English)》2015,54(29):8454-8457
Treatment of antiaromatic nickel(II) norcorrole with potassium cyanide provided nickel(II) 3‐cyanonorcorrole with perfect regioselectivity without the help of a catalyst. The reaction of the nickel(II) norcorrole with phenol or thiophenol in the presence of a base also yielded substitution products. The antiaromatic 16π conjugation system in the norcorrole core was preserved in the functionalized products. Introduction of phenylthio groups significantly decreased the HOMO–LUMO gap and enhanced the near IR absorption property. 相似文献
65.
Kausar A Nagano H Kuwahara Y Ogata T Kurihara S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(2):508-515
In this paper the photocontrolled manipulation of solid materials on the surface of a liquid crystalline thin film is described. Three different types of films namely cholesteric liquid crystal (ChLC), compensated nematic liquid crystal (NLC) and nematic LC were used. The rotational and translational manipulation of the microscale solid object was induced by irradiation of light and mode of manipulation (either translational or rotational) was changed by changing the isomer of the azobenzene compound used to make the film. Rotational motion of the object was observed on the ChLC and compensated NLC films containing chirally pure azobenzene compound. The direction of rotational motion was controlled either by changing the optical isomer of the chiral azobenzene or by changing the irradiating light (from ultraviolet to visible). When racemic mixture of the chiral azobenzene compound was used, a translational motion of the object was observed. Even though the direction of the translational motion can be controlled by controlling irradiation position, more facile and precise manipulation of the objects was possible by spatially controlled irradiation of Ar(+) laser and diode UV laser. 相似文献
66.
Treatment of perylene bisimides (PBIs) with bis(pinacolato)diboron in the presence of an iridium catalyst provides tetraborylated PBIs at 2,5,8,11-positions in good yields with perfect regioselectivity. The planar structure of the perylene core has been confirmed by X-ray diffraction analysis. Oxidation of tetraborylated PBI with hydroxylamine hydrochloride affords tetrahydroxy PBI in excellent yield, which exhibits a substantially blue-shifted absorption spectrum due to an intramolecular hydrogenbonding interaction between carbonyl and hydroxy groups. 相似文献
67.
The direct arylation on the thienyl groups of a diarylethene with various aryl iodides efficiently provided arylated dithienylethenes under palladium catalysis. Unsymmetrically substituted dithienylethenes were also synthesized by this protocol. This procedure allows a rapid access to a variety of aryl-substituted dithienylethenes from a single substrate of a simple dithienylethene. 相似文献
68.
Ito K Tamashima H Iwasawa N Kusama H 《Journal of the American Chemical Society》2011,133(11):3716-3719
Intermolecular carbon-carbon bond formation between acylsilanes and organoboronic esters was achieved by photoirradiation under almost neutral, transition metal-free conditions. In this reaction, siloxycarbenes generated by photoisomerization of acylsilanes reacted with boronic esters to give the formal B-C bond insertion intermediates, which underwent unique rearrangement to afford the cyclic α-alkoxyboronic esters. Acidic treatment of the resulting crude products under air furnished the cross-coupled ketones in good yields. 相似文献
69.
Suzuki IH Kono Y Ikeda A Ouchi T Ueda K Takahashi O Higuchi I Tamenori Y Nagaoka S 《The Journal of chemical physics》2011,134(8):084312
Spectator resonant KL(23)L(23) Auger electron spectra have been measured in the Si 1s photoexcitation region of Si(CH(3))(4) using monochromatized undulator radiation combined with a hemispherical electron spectrometer. The broad peak with high intensity in a total ion yield spectrum, coming mainly from excitation of a 1s electron into the 6t(2) vacant orbital, induces a spectator Auger decay in which the excited electron remains in its excited orbital. The component on the higher energy side of this peak through 1s excitation into a Rydberg orbital produces resonant Auger decays in which the excited Rydberg electron moves into a slightly higher Rydberg orbital, or is partly shaken up to a significantly higher Rydberg orbital. These findings of Si(CH(3))(4) indicate a clear contrast to those for SiF(4), in which the 1s excitation into a Rydberg orbital induces a shake-down phenomenon as well as a shake-up one. The results of these molecules exhibit a clear splitting effect among excited orbitals which are smeared out by overlapping due to lifetime widths and due to densely populated levels in the 1s electron excitation spectrum. This is consistent with the calculation on photoexcitation within the framework of density functional theory. 相似文献
70.
Yoshida H Ito Y Yoshikawa Y Ohshita J Takaki K 《Chemical communications (Cambridge, England)》2011,47(30):8664-8666
Trifluoromethyl ketones were found to be coupled with arynes in three modes depending upon their substitution patterns, namely C-C bond cleavage, [2+2] cycloaddition and O-arylation. 相似文献