全文获取类型
收费全文 | 395篇 |
免费 | 16篇 |
国内免费 | 7篇 |
专业分类
化学 | 220篇 |
晶体学 | 1篇 |
力学 | 8篇 |
数学 | 93篇 |
物理学 | 96篇 |
出版年
2022年 | 2篇 |
2021年 | 4篇 |
2020年 | 3篇 |
2019年 | 3篇 |
2018年 | 8篇 |
2017年 | 6篇 |
2016年 | 6篇 |
2015年 | 9篇 |
2014年 | 10篇 |
2013年 | 29篇 |
2012年 | 20篇 |
2011年 | 18篇 |
2010年 | 12篇 |
2009年 | 15篇 |
2008年 | 26篇 |
2007年 | 22篇 |
2006年 | 25篇 |
2005年 | 23篇 |
2004年 | 15篇 |
2003年 | 19篇 |
2002年 | 12篇 |
2001年 | 4篇 |
2000年 | 5篇 |
1999年 | 7篇 |
1998年 | 5篇 |
1997年 | 6篇 |
1996年 | 15篇 |
1995年 | 7篇 |
1994年 | 12篇 |
1993年 | 9篇 |
1992年 | 7篇 |
1991年 | 9篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1979年 | 2篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1948年 | 3篇 |
1934年 | 2篇 |
1929年 | 1篇 |
1926年 | 2篇 |
排序方式: 共有418条查询结果,搜索用时 15 毫秒
71.
72.
Various ketones, esters, amides, and thioesters add in high yield to dimethyl acetals in the presence of silyl trifluoromethanesulfonates and an amine base. Acetals derived from aryl, unsaturated, and aliphatic aldehydes are all effective substrates. The reaction proceeds in a single reaction flask, with no purification of the intermediate enol silane necessary. 相似文献
73.
74.
75.
MARIAN ELBANOWSKI MARIA PAETZ JANUSZ SIAWINSKI LESZEK CIELA 《Photochemistry and photobiology》1988,47(3):463-466
Abstract— Chemiluminescence of the Eu(II)/Eu(III)-adenine nucleotide-H2 O2 system and fluorescence of the Eu(III)-adenosine triphosphate system have been investigated. The spectral distribution of the chemiluminescence emission has shown an occurrence of three main bands (Λ=470–480,590–620 and ca. 700 nm). The energy transfer process from the adenosine triphosphate molecules to the Eu(III) ions has been observed in the fluorescence spectrum. The examined chemiluminescence and fluorescence spectra show that these both kinds of emission originate from the 5 D *** τ7 F*** ( n =1–4) transitions in the Eu(III) ions. 相似文献
76.
Malyarenko DI Cooke WE Tracy ER Trosset MW Semmes OJ Sasinowski M Manos DM 《Rapid communications in mass spectrometry : RCM》2006,20(11):1661-1669
By applying time-domain filters to time-of-flight (TOF) mass spectrometry signals, we have simultaneously smoothed and narrowed spectra resulting in improved resolution and increased signal-to-noise ratios. This filtering procedure has an advantage over detailed curve fitting of spectra in the case of large dense spectra, when neither the location nor the number of mass peaks is known a priori. This time series method is directly applicable in the time lag optimization range, where point density per peak is constant. We present a systematic methodology to optimize the filters according to any desired figure of merit, illustrating the procedure by optimizing the signal-to-noise per unit bandwidth of matrix-assisted laser desorption/ionization (MALDI) data. We also introduce a nonlinear filter that reduces the spurious structure that often accompanies deconvolution filters. The net result of the application of these filters is that we can identify new structures in dense MALDI-TOF data, clearly showing small adducts to heavy biomolecules. 相似文献
77.
Liu X Bordunov A Tracy M Slingsby R Avdalovic N Pohl C 《Journal of chromatography. A》2006,1119(1-2):120-127
This paper describes a new polar-embedded stationary phase that contains an internal sulfonamide functional group coupled with an ether linkage. The synthesis involves functionalization of spherical silica particles with ligands prepared in a multi-step synthesis. The resulting material contains 16.5% carbon, corresponding to a ligand coverage of 2.4mumol/m(2). Chromatographic evaluations indicates that the new stationary phase exhibits lower polarity than any other polar-embedded packings investigated, with additional features such as low silanol activity, excellent compatibility with 100% aqueous mobile phases, higher shape selectivity for polycyclic aromatic hydrocarbons, and strong affinity to nitro-containing compounds. 相似文献
78.
For temperatures below the critical temperature, the magnetic susceptibility for the two-dimensional isotropic Ising model can be expressed in terms of an infinite series of multiple integrals. With respect to a parameter related to temperature and the interaction constant, the integrals may be extended to functions analytic outside the unit circle. In a groundbreaking paper, Nickel (J Phys A 32:3889–3906, 1999) identified a class of singularities of these integrals on the unit circle. In this note we show that there are no other singularities on the unit circle. 相似文献
79.
Chalmers S Caldwell ST Quin C Prime TA James AM Cairns AG Murphy MP McCarron JG Hartley RC 《Journal of the American Chemical Society》2012,134(2):758-761
Depolarization of an individual mitochondrion or small clusters of mitochondria within cells has been achieved using a photoactivatable probe. The probe is targeted to the matrix of the mitochondrion by an alkyltriphenylphosphonium lipophilic cation and releases the protonophore 2,4-dinitrophenol locally in predetermined regions in response to directed irradiation with UV light via a local photolysis system. This also provides a proof of principle for the general temporally and spatially controlled release of bioactive molecules, pharmacophores, or toxins to mitochondria with tissue, cell, or mitochondrion specificity. 相似文献
80.
Tracy D. NixonMichael K. Whittlesey Jonathan M.J. Williams 《Tetrahedron letters》2011,52(49):6652-6654
Dimethylamine-borane adduct has been used as the hydrogen source for the reduction of carbonyl compounds, imines, oximes, nitriles, nitroarenes and alkenes using [Ru(p-cymene)Cl2]2 as the catalyst. 相似文献