全文获取类型
收费全文 | 295篇 |
免费 | 3篇 |
国内免费 | 1篇 |
专业分类
化学 | 238篇 |
晶体学 | 1篇 |
力学 | 4篇 |
数学 | 29篇 |
物理学 | 27篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 12篇 |
2020年 | 10篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2016年 | 3篇 |
2015年 | 3篇 |
2014年 | 10篇 |
2013年 | 23篇 |
2012年 | 16篇 |
2011年 | 14篇 |
2010年 | 12篇 |
2009年 | 16篇 |
2008年 | 6篇 |
2007年 | 9篇 |
2006年 | 7篇 |
2005年 | 9篇 |
2004年 | 15篇 |
2003年 | 14篇 |
2002年 | 15篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 10篇 |
1992年 | 1篇 |
1991年 | 5篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 8篇 |
1983年 | 6篇 |
1982年 | 2篇 |
1981年 | 7篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有299条查询结果,搜索用时 688 毫秒
111.
112.
Alain Favre Giuliana Moreno Christian Salet Francloise Vinzens 《Photochemistry and photobiology》1993,58(5):689-694
Monkey kidney cells (CV-1) grown for 4 h in the presence of 0.1 m M 4-thiouridine (s4 Urd) incorporate this photoactivable uridine analog in their RNA. A minor, 5–8%, thiolated RNA fraction can be isolated from bulk RNA by affinity chromatography. This RNA fraction contains 1.5–2.5 s4 Urd residues per 100 nucleotides and exhibits a broad chain length distribution ranging from 700 to 7000 nucleotides. It is essentially of nuclear origin and amounts to 30% of the RNA synthesized during exposure of cells to s4 Urd. Under the same s4 Urd labeling conditions, no thiolated pyrimidine residues have been detected in DNA.
Irradiation with 365 nm light (45 kJ/m2 ) of the cells immediately after s4 Urd exposure triggers long-term inhibition of DNA, RNA and protein synthesis accompanied by a linear decline (50% in 2 days) in the total cell mass of cultured cells. In contrast, exposure to s4 Urd alone results in moderate but reversible inhibitory effects. The available data suggest that s4 Urd-induced photolesions in newly synthesized RNA such as RNA-RNA cross-links as well as RNA-protein bridges are directly involved in impairment of essential cellular functions. 相似文献
Irradiation with 365 nm light (45 kJ/m
113.
Giuliana Borsa Stefania Castelletto Aldo Godone Carlo Novero Maria Luisa Rastello 《Optical Review》1997,4(4):484-489
This work presents a new technique for the measurement of second-order optical nonlinear coefficients from the absolute radiant power of the parametric fluorescence emission. It is based on calibrated detectors regarded as secondary radiometric standards. This technique makes it possible to skip a number of problems usually encountered with standard techniques based on calibrated neutral density filters and reference sources of light at much higher power levels. We infer a value for the d31 nonlinear coefficient of LiIO3 from spectral measurements of the fluorescence power integrated over all solid angles, by denning the wavelength bandwidths with interference filters. Moreover, by performing the measurements on the ultraviolet and visible emission lines of an argon ion laser in the range from 351 to 488 nm, the wavelength dependence of d31 is compared with the expected one obtained by Miller’s dispersion law. 相似文献
114.
115.
116.
Piero Zanello Giuliana OpromollaLuca PardiKeith H. Pannell Hemant K. Sharma 《Journal of organometallic chemistry》1993,450(1-2):193-196
The electrochemical behaviour of the ferrocenylacyl derivatives [FcCOER3] (E = C, Si or Ge; R = Me or Ph) is examined. One-electron oxidations to the substantially stable monocations [FcCOER3]+ occur at potentials significantly higher than that observed with ferrocene, but only minor differences hold within the series, independent of the nature of both E and R. In contrast the EPR spectra of the monocations for E = C show that the unpaired electron resides mainly on the iron, whereas for E = Si or Ge the electron density is essentially localized on the C5H4COER3 fragment. 相似文献
117.
Giuliana Palmieri 《Milan Journal of Mathematics》1995,65(1):335-356
Given a setS and a function σ:S x S→[0, +∞[ such that σ(x, x)=0, we define the generalizedp-energy of a curve γ: [a, b]→S, so that, ifS is a Hilbert space and σ(x, y)=‖x−y‖ we obtain
. Sufficient conditions for the equality of the defined energies are also given. Moreover the case in whichS is a set of measurable parts of ℝn and σr is a family of functions used in order to study the generalized minimizing motions, is discussed.
Conferenza tenuta il 30 ottobre 1995 相似文献
Conferenza tenuta il 30 ottobre 1995 相似文献
118.
Abstarct The Cp)2Ni2Fe(CO)3(µ3-C2H2) and Cp)2Ni2Fe(CO)3(µ3-C2H2) (B) complexes have been synthesized and spectroscopically characterized. An accurate X-ray study and a comparison with related structures shows that the substituents of the alkyne ligands exert considerable effects on the bonding parameters.Crystal data for complex A, monoclinic space group P21/n,a = 8.418(1),b = 15.779(2),c = 14,493(1) Å, = 91.64(1)°,Z = 4, 2753 observed reflections,R = 0.022; crystal data for complex B, monoclinic space group C2/c,a = 16.2189(7),b = 7.445(3),c = 25.745(5) Å, = 103.74(3),Z=8, 1853 observed reflections,R = 0.051. 相似文献
119.
Stoichiometry of superconducting YBa2Cu3Oy. Determination of Cu(III)/Cu(II) ratio and oxygen content
The electrical properties of the high Tc superconductor YBa2Cu3Oy depend on its oxygen content. The oxygen content is indirectly determined by iodimetric measurement of the oxidation state of copper. A combination of two titrations, with and without addition of KI, prior to dissolving the sample permits the determination of the two species Cu(II) and Cu(III). A simplified automatic titration with potentiometric detection of the end-point is described. The method is suitable for rapid and reliable determinations of the Cu(III)/Cu(II) ratio and total copper content and for controlling the stoichiometry of the compound.Samples of the superconductor were analysed and the stoichiometric coefficient y for oxygen was determined with excellent results. Typically, y=6.811 ± 0.0063 (s.d.) (n=5). A comparison of the total copper content (found by direct analytical determination) with the copper concentration calculated from the stoichiometric formula gives an evaluation of possible deterioration of the sample. 相似文献
120.
Oreste Livi Giuliana Biagi Pier Luigi Ferrarini Gianpaolo Primofiore Claudio Mori 《Journal of heterocyclic chemistry》1983,20(6):1729-1733
This paper describes the preparation of three series of 1-phenyl-1,2,3-triazol derivatives with an ester, amide or ether group on the phenyl ring. These derivatives were obtained from 4-hydroxyphenyl- and 4-aminophenyltriazoles, previously synthesized by us, by means of a nucleophilic substitution reaction with acetic anhydride, acyl and alkyl halides. The largest part of compounds were tested in an agricultural chemicals, nutrition and animal health screening programme. 相似文献