全文获取类型
收费全文 | 2038篇 |
免费 | 102篇 |
国内免费 | 34篇 |
专业分类
化学 | 1664篇 |
晶体学 | 13篇 |
力学 | 22篇 |
数学 | 98篇 |
物理学 | 377篇 |
出版年
2023年 | 20篇 |
2022年 | 9篇 |
2021年 | 22篇 |
2020年 | 38篇 |
2019年 | 52篇 |
2018年 | 42篇 |
2017年 | 18篇 |
2016年 | 35篇 |
2015年 | 64篇 |
2014年 | 59篇 |
2013年 | 96篇 |
2012年 | 125篇 |
2011年 | 121篇 |
2010年 | 86篇 |
2009年 | 73篇 |
2008年 | 163篇 |
2007年 | 129篇 |
2006年 | 149篇 |
2005年 | 147篇 |
2004年 | 140篇 |
2003年 | 107篇 |
2002年 | 108篇 |
2001年 | 36篇 |
2000年 | 36篇 |
1999年 | 16篇 |
1998年 | 16篇 |
1997年 | 16篇 |
1996年 | 16篇 |
1995年 | 11篇 |
1994年 | 10篇 |
1993年 | 17篇 |
1992年 | 16篇 |
1991年 | 6篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 11篇 |
1987年 | 9篇 |
1986年 | 7篇 |
1985年 | 19篇 |
1984年 | 15篇 |
1983年 | 4篇 |
1982年 | 12篇 |
1981年 | 13篇 |
1980年 | 16篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1975年 | 5篇 |
1972年 | 4篇 |
排序方式: 共有2174条查询结果,搜索用时 15 毫秒
101.
Hiroyuki?OhshimaEmail author Hiroko?Sato Hiroki?Matsubara Atsushi?Hyono Masayoshi?Okubo 《Colloid and polymer science》2004,282(10):1174-1178
A theory of adsorption kinetics with time delay [Ohshima et al. (1992) Colloid Polym. Sci. 270:707] is developed and applied to the surface tension of a polymer solution. It is found that the general appearance of the overshoot and oscillation in the time course of the surface tension of aqueous gelatin solution observed by Sato and Ueberreiter [(1979) Makromol. Chem. 180:829, 1107; (1979) Polym. Prepr. Am. Chem. Soc. Div. Polym. Chem. 20:907) can be explained by the present theory. 相似文献
102.
[reaction: see text] Allylzirconium reagents are effective for radical allylation of alpha-halo carbonyl compounds. The key steps would be homolytic cleavage of the zirconium-carbon bond and halogen abstraction by the resulting Cp(2)ZrCl(III). Zirconocene-olefin complex can be also utilized for the allylation of alpha-halo compounds. 相似文献
103.
Ikeda Y Nakamura T Yorimitsu H Oshima K 《Journal of the American Chemical Society》2002,124(23):6514-6515
A cobalt complex, CoCl2[1,6-bis(diphenylphosphino)hexane], catalyzes an alkylation reaction of styrenes in the presence of Me3SiCH2MgCl in ether to yield beta-alkylstyrenes. A variety of alkyl halides including alkyl chlorides can be employed as an alkyl source. A radical mechanism is strongly suggested for this alkylation reaction. 相似文献
104.
Jumina Ratnaningsih Eko Sarjono Brajna Paramitha Ika Hendaryani Dwi Siswanta Sri Juari Santosa Chairil Anwar Hardjono Sastrohamidjojo Keisuke Ohto Tatsuya Oshima 《中国化学会会志》2007,54(5):1167-1178
A study on the adsorption characteristics of Pb(II) and Cr(III) cations onto C‐4‐methoxyphenylcalix‐[4]resorcinarene (CMPCR) in batch and fixed bed column systems has been conducted. CMPCR was produced by one step synthesis from resorcinol, 4‐methoxybenzaldehyde, and HCl. The synthesis was carried out at 78 °C for 24 hours and afforded the adsorbent in 85.7% as a 3:2 mixture of C4ν:C2ν isomer. Most parameters in batch and fixed bed column systems confirm that CMPCR is a good adsorbent for Pb(II) and Cr(III), though Pb(II) adsorption was more favorable than that of Cr(III). The adsorption kinetic of Pb(II) and Cr(III) adsorptions in batch and fixed bed column systems followed a pseudo 2n order kinetics model. The rate constant of Pb(II) was higher than that of Cr(III) in the batch system, but this result was contrary to the result obtained in a fixed bed column system. Desorption studies to recover the adsorbed Pb(II) and Cr(III) were performed sequentially with distilled water and HCl, and the results showed that the adsorption was dominated by chemisorption. 相似文献
105.
A series of samples with the composition Ca(1)(-)(x)Na(2)(x)Al(2)B(2)O(7) (0 < x < or = 1) was investigated and a hexagonal structure with unusually large range of homogeneity (at least from x = 0.01 to 0.95) was revealed. The hexagonal phase consists of [Al(2)B(2)O(7)](infinity)(2)(-) lamellae stacked along the c axis, as in CaAl(2)B(2)O(7) and Na(2)Al(2)B(2)O(7). Nevertheless, the configuration and stacking sequence of the [Al(2)B(2)O(7)](infinity)(2)(-) lamellae are different in these three structures. In the hexagonal structure of Ca(1)(-)(x)()Na(2)(x)()Al(2)B(2)O(7), Ca and half Na cations (Na1) statistically occupy the same crystallographic site which is located between the [Al(2)B(2)O(7)](infinity)(2)(-) lamellae, the other half Na cations (Na2) distribute in the planes bisecting the [Al(2)B(2)O(7)](infinity)(2)(-) lamellae. Depending on the composition, the site occupation factor of Na2 site can vary in the same range as x, leading to a tunable density of Na(+) vacancies in the structure. The AlO(4) tetrahedra and BO(3) triangles in the structure tilt in appropriate ways to improve the bond valence sum of Na2 cations which are not sufficiently bonded to the anions. 相似文献
106.
A novel method for determination of inorganic oxyanions by electrospray ionization mass spectrometry using dehydration reactions 下载免费PDF全文
Hirochika Kojima Shota Kurihara Yoshito Watanabe Koki Iwamaru Kiichi Sato Kin‐ichi Tsunoda Hiroki Hotta 《Journal of mass spectrometry : JMS》2016,51(2):123-131
Novel methods for the determination of inorganic oxyanions by electrospray (ES) ionization mass spectrometry have been developed using dehydration reactions between oxyanions and carboxylic acids at the ES interface. Twelve oxyanions (VO3?, CrO42?, MoO42?, WO42?, BO33?, SiO32?, SiO44?, AsO44?, AsO2?, SeO42?, SeO32? and NO2?), out of 16 tested, reacted with at least one of four aminopolycarboxylic acids, i.e. iminodiacetic acid (IDA), nitrilotriacetic acid (NTA), trans‐1,2‐diaminocyclohexane‐N,N,N′,N′‐tetraacetic acid and triethylenetetramine‐N,N,N′,N″,N′″,N′″‐hexaacetic acid, at the ES interface to produce the dehydration products that gave intense mass ion responses, sufficient for trace analysis. As examples, trace determinations of CrVI and silica in water samples were achieved after online ion exchange chromatography, where the dehydration product of CrO42? and NTA (m/z 290) and that of SiO44? and IDA (m/z 192) were measured. The limits of detection of the respective methods were 17 nM (0.83 ng Cr/ml) for CrVI and 0.17 μM (4.8 ng Si/mL) for SiO44?. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
107.
Shigekazu Ito Hiroki Sugiyama Masaaki Yoshifuji 《Phosphorus, sulfur, and silicon and the related elements》2013,188(4-5):785-788
1-(2,4,6-Tri-tert-butylphenyl)-2-phosphaethyne (1) was allowed to react with 0.5 equiv of an alkyllithium and subsequently with an alcohol to afford a bulky 1,3-diphosphacyclobutene, and its structure and coordination properties on transition metals were investigated. On the other hand, 1 was allowed to react with an alkyllithium and iodomethane to form a stable biradical, 1,3-diphosphacyclobutane-2,4-diyl. 相似文献
108.
109.
Cross‐Coupling of Organolithium with Ethers or Aryl Ammonium Salts by C−O or C−N Bond Cleavage 下载免费PDF全文
Ze‐Kun Yang Dong‐Yu Wang Hiroki Minami Hiroyuki Ogawa Takashi Ozaki Dr. Tatsuo Saito Dr. Kazunori Miyamoto Dr. Chao Wang Prof. Dr. Masanobu Uchiyama 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(44):15693-15699
Various aryl‐, alkenyl‐, and/or alkyllithium species reacted smoothly with aryl and/or benzyl ethers with cleavage of the inert C?O bond to afford cross‐coupled products, catalyzed by commercially available [Ni(cod)2] (cod=1,5‐cyclooctadiene) catalysts with N‐heterocyclic carbene (NHC) ligands. Furthermore, the coupling reaction between the aryllithium compounds and aryl ammonium salts proceeded under mild conditions with C?N bond cleavage in the presence of a [Pd(PPh3)2Cl2] catalyst. These methods enable selective sequential functionalizations of arenes having both C?N and C?O bonds in one pot. 相似文献
110.