全文获取类型
收费全文 | 783篇 |
免费 | 16篇 |
国内免费 | 2篇 |
专业分类
化学 | 630篇 |
晶体学 | 14篇 |
力学 | 11篇 |
数学 | 50篇 |
物理学 | 96篇 |
出版年
2021年 | 7篇 |
2020年 | 10篇 |
2019年 | 10篇 |
2018年 | 5篇 |
2017年 | 5篇 |
2016年 | 9篇 |
2015年 | 10篇 |
2014年 | 18篇 |
2013年 | 37篇 |
2012年 | 35篇 |
2011年 | 47篇 |
2010年 | 24篇 |
2009年 | 23篇 |
2008年 | 36篇 |
2007年 | 36篇 |
2006年 | 44篇 |
2005年 | 38篇 |
2004年 | 40篇 |
2003年 | 38篇 |
2002年 | 44篇 |
2001年 | 14篇 |
2000年 | 17篇 |
1999年 | 14篇 |
1998年 | 6篇 |
1997年 | 11篇 |
1996年 | 12篇 |
1995年 | 5篇 |
1994年 | 13篇 |
1993年 | 10篇 |
1992年 | 4篇 |
1991年 | 7篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1987年 | 12篇 |
1986年 | 9篇 |
1985年 | 18篇 |
1984年 | 16篇 |
1983年 | 4篇 |
1982年 | 16篇 |
1981年 | 10篇 |
1980年 | 14篇 |
1979年 | 12篇 |
1978年 | 9篇 |
1977年 | 4篇 |
1976年 | 7篇 |
1975年 | 4篇 |
1973年 | 5篇 |
1971年 | 3篇 |
1968年 | 3篇 |
1967年 | 2篇 |
排序方式: 共有801条查询结果,搜索用时 31 毫秒
51.
Kuriyama M Soeta T Hao X Chen Q Tomioka K 《Journal of the American Chemical Society》2004,126(26):8128-8129
A catalytic asymmetric arylation of sterically tuned imines with arylboroxines was developed by using N-Boc-l-valine-connected amidomonophosphane rhodium(I) catalyst in n-PrOH. The TMS group used for the steric tuning of imines is convertible to other functionalities that are applicable as a key foothold for the carbon-carbon bond-forming coupling reactions. 相似文献
52.
Fujimoto H Nakamura E Okuyama E Ishibashi M 《Chemical & pharmaceutical bulletin》2004,52(8):1005-1008
In a screening study on immunomodulatory fungal metabolites, three known anthraquinones, carviolin (roseo-purpurin) (1), 1-O-methylemodin (2), omega-hydroxyemodin (citreorosein) (4), and a new anthraquinone, omega-acetylcarviolin (3), together with a known steroid, ergosta-4,6,8(14),22-tetraen-3-one (5) and a new steroid, 25-hydroxyergosta-4,6,8(14),22-tetraen-3-one (6) were isolated from an Ascomycete, Zopfiella longicaudata, and found to have moderate immunosuppressive activities. The structure-activity relationships of these metabolites are discussed. 相似文献
53.
Ikeda S Sanuki R Miyachi H Miyashita H Taniguchi M Odashima K 《Journal of the American Chemical Society》2004,126(33):10331-10338
A Ni(0)/ZnCl(2) system effectively promotes the coupling of enones and alkene-tethered alkynes. In the reaction with 1,6-enynes, the oxidative cyclization of Ni(0) species on enones across the alkyne part followed by ZnCl(2)-promoted cleavage generates alkenylnickel intermediates. Subsequent migratory insertion of the tethered alkene occurs with 5-exo-cyclization. When the resulting sigma-alkylnickel intermediates have beta-hydrogen atoms, the reaction terminates by beta-hydrogen elimination to provide cyclopentane derivatives. On the other hand, a sigma-alkylnickel intermediate that does not have beta-hydrogen atoms undergoes the insertion of a second alkene unit to cause a domino effect via a three-fold C-C bond formation process with and without the cleavage of one C-C bond. 相似文献
54.
A. Saito K. Takahashi Y. Takagi K. Hanai Y. Tanaka M. Akai-kasaya S. Shin T. Ishikawa M. Aono 《Surface science》2007,601(22):5294-5299
To solve difficulties of instability and inaccuracy in synchrotron radiation based scanning tunneling microscopy, a method to reduce noise was investigated. New insulator-coat tips were developed to shut out electrons coming from a wide area that damage the spatial resolution. By changing the exposed conductive area at the end of the insulator-coat tips, the effect of noise reduction was estimated. The tip with an exposure area of 50 nm in diameter was found to reduce noise effectively. Also a key discriminating condition was found to obtain the local signal, which is based on the modulation of the X-ray-induced tip current caused by excitation of the specific element. 相似文献
55.
In this paper we prove that the language of all primitive (strongly primitive) words over a nontrivial alphabet can be generated by certain types of Marcus contextual grammars. 相似文献
56.
57.
58.
The quantitative evaluation on measurement of liver volume and the hepatic accumulation rate of the radioactive agent were studied with respect to body constitution, background activity and splenic consumption rate, using single photon emission computed tomography (SPECT). The optical cut-off level for liver volume determination was proved to be reasonable as 35%. The background less than 5% had no influence to their clinical estimation with the error of less than 1.6%. The estimation of liver volume was mostly influenced by the splenic activity. When the splenic activity was increased two times of the hepatic activity, the liver volume was determined as 4.2% larger. Calculated counts by SPECT was well correlated with the hepatic activity. This study proved that SPECT was useful for the quantitative evaluation of the liver volume and the hepatic accumulation rate. 相似文献
59.
60.
Hiromasa Aono Dingy Wen Li Zang Damian Houde R. Blake Pepinsky David R.H. Evans 《Journal of chromatography. A》2010,1217(32):5225-5232
Protein trisulfide linkages are generated by the post-translational insertion of a sulfur atom into a disulfide bond. Molecular heterogeneity was detected in a recombinant IgG1 monoclonal antibody (mAb) and attributed to the presence of a protein trisulfide moiety. The predominant site of trisulfide modification was the bond between the heavy and light chains. The trisulfide was eliminated during purification of the IgG1 mAb via a cysteine wash step incorporated into Protein A affinity column chromatography. Analysis of the cysteine-treated mAb by electrophoresis and peptide mapping indicated that the trisulfide linkages were efficiently converted to intact disulfide bonds (13% trisulfide decreased consistently to 1% or less) without disulfide scrambling or an increase in free sulfhydryls. The on-column trisulfide conversion caused no change in protein folding detectable by hydrogen/deuterium exchange or differential scanning calorimetry. Consistent with this, binding of the mAb to its antigen in vitro was insensitive to the presence of the trisulfide modification and to its removal by the on-column cysteine treatment. Similar, high efficiency trisulfide conversion was achieved for a second IgG1 mAb using the column wash strategy (at least 7% trisulfide decreased to 1% or less). Therefore, trisulfide/disulfide heterogeneity can be eliminated from IgG1 molecules via a convenient and inexpensive procedure compatible with routine Protein A affinity capture. 相似文献