全文获取类型
收费全文 | 314篇 |
免费 | 5篇 |
国内免费 | 1篇 |
专业分类
化学 | 154篇 |
力学 | 8篇 |
数学 | 43篇 |
物理学 | 115篇 |
出版年
2022年 | 4篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2016年 | 3篇 |
2014年 | 2篇 |
2013年 | 9篇 |
2012年 | 14篇 |
2011年 | 16篇 |
2010年 | 6篇 |
2009年 | 5篇 |
2008年 | 7篇 |
2007年 | 15篇 |
2006年 | 8篇 |
2005年 | 11篇 |
2004年 | 7篇 |
2003年 | 6篇 |
2002年 | 10篇 |
2001年 | 5篇 |
2000年 | 17篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 16篇 |
1992年 | 13篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 2篇 |
1980年 | 9篇 |
1979年 | 6篇 |
1978年 | 8篇 |
1977年 | 2篇 |
1976年 | 12篇 |
1975年 | 6篇 |
1974年 | 5篇 |
1973年 | 8篇 |
1972年 | 3篇 |
1971年 | 2篇 |
1965年 | 3篇 |
1936年 | 1篇 |
排序方式: 共有320条查询结果,搜索用时 15 毫秒
311.
312.
C.W. Bjork P.J. Riley B.E. Bonner J.E. Simmons K.D. Williamson M.L. Evans G. Glass J.C. Hiebert M. Jain R.A. Kenefick L.C. Northcliffe C.G. Cassapakis H.C. Bryant B.D. Dieterle C.P. Leavitt D.M. Wolfe D.W. Werren 《Physics letters. [Part B]》1976,63(1):31-34
The p—d spectra show sharp high-energy peaks (≈ 15 MeV FWHM) with integrated yields of 30 and 31 mb/sr, respectively and with lower-energy bumps associated with pion production. The p—p spectra reflect the influence of the Δ(1232) resonance. 相似文献
313.
Crepin C Broquier M Dubost H Galaup JP Le Gouet JL Ortega JM 《Physical review letters》2000,85(5):964-967
Infrared picosecond accumulated photon echo experiments have been performed for the first time, using the Orsay Free Electron Laser, on the v = 0-->v = 1 transition of CO in solid nitrogen. The vibrational dephasing time is found to be exceptionally long ( T2>/=120 ns) at low temperature. The analysis of the observed spectral diffusion leads one to assume different energy transfer mechanisms depending on the CO concentration. 相似文献
314.
315.
[reaction: see text]Phenylacetic acid dianions react via what appears to be an S(RN)1 process with aryl halides under photostimulation to afford aryl substitution products 5 and 6. When the counterion is K+, only 4-biphenylacetic acids 5 are obtained. Both alpha- and para-coupling occurs with Na+ to give a mixture of 5 and 6, while exclusive formation of diphenylacetic acids 6 is observed with the dilithio salt of 1. 相似文献
316.
A new and compact fluorescence biosensor is constructed. The distinguished feature of this setup is the use of an ellipsoidal reflector as an optical collector of the fluorescence light. A traditional collecting lens with numerical aperture of 0.5 can only collect a few percent of the available signal, while the incorporation of the ellipsoidal reflector enables the apparatus to provide a signal increase of at least 66 times. A very good linear relationship between the concentration of fluorescent dye and the fluorescence intensity is achieved with correlation coefficient R=0.99979. The 3σ detection limit is 5 nM for microliter volume sample. Meanwhile, it is found that laser light scattering by dirts and scratches on the sample cell's windows and by turbidity in the sample solutions is the dominant limitation to increase the detection sensitivity. Approach to solve this problem is suggested. 相似文献
317.
The synthesis of tropane derivatives via intramolecular Pd-catalyzed alkene difunctionalization reactions is described. Enantiopure N-aryl-γ-aminoalkenes bearing an aryl or alkenyl halide adjacent to the amino group were converted to benzo- or cycloalkenyl-fused tropane products in good yield and with no loss of enantiopurity. 相似文献
318.
The stereoselective synthesis of 2,4- and 2,5-disubstituted 1,3-oxazolidines is accomplished via Pd-catalyzed carboamination of O-vinyl-1,2-amino alcohol derivatives. The transformations generate cis-disubstituted products with good to excellent diastereoselectivity, and enantiomerically enriched substrates are converted without loss of optical purity. In addition to yielding synthetically useful products that are difficult to generate with existing methods, these transformations illustrate that electron-rich enol ethers are viable substrates for alkene carboamination processes. 相似文献
319.
A concise asymmetric synthesis of (+)-aphanorphine has been achieved via a new enantioconvergent strategy. A racemic γ-aminoalkene derivative is transformed into a 1:1 mixture of enantiomerically enriched diastereomers using an asymmetric Pd-catalyzed carboamination. This mixture is then converted to an enantiomerically enriched protected aphanorphine derivative by a Friedel-Crafts reaction, which generates a quaternary all-carbon stereocenter. The natural product is obtained in three additional steps. 相似文献
320.
Anthony J. Rojas Justin M. Wolfe Heemal H. Dhanjee Ivan Buslov Nicholas L. Truex Richard Y. Liu Walter Massefski Bradley L. Pentelute Stephen L. Buchwald 《Chemical science》2022,13(40):11891
The synthesis of palladium oxidative addition complexes derived from unprotected peptides is described. Incorporation of 4-halophenylalanine into a peptide during solid phase peptide synthesis allows for subsequent oxidative addition at this position upon treatment with a palladium precursor and suitable ligand. The resulting palladium–peptide complexes are solid, storable, water-soluble, and easily purified via high-performance liquid chromatography. These complexes react with thiols in aqueous buffer, offering an efficient method for bioconjugation. Using this strategy, peptides can be functionalized with small molecules to prepare modified aryl thioether side-chains at low micromolar concentrations. Additionally, peptide–peptide and peptide–protein ligations are demonstrated under dilute aqueous conditions.Peptides bearing palladium oxidative addition complexes can be synthesized from the parent aryl halide containing substrates and react with thiol functional groups of small molecules, peptides, and proteins at low micromolar concentrations. 相似文献