全文获取类型
收费全文 | 461篇 |
免费 | 18篇 |
国内免费 | 2篇 |
专业分类
化学 | 308篇 |
晶体学 | 5篇 |
力学 | 9篇 |
数学 | 54篇 |
物理学 | 105篇 |
出版年
2023年 | 6篇 |
2022年 | 3篇 |
2021年 | 7篇 |
2020年 | 9篇 |
2019年 | 14篇 |
2018年 | 16篇 |
2017年 | 4篇 |
2016年 | 22篇 |
2015年 | 7篇 |
2014年 | 19篇 |
2013年 | 27篇 |
2012年 | 31篇 |
2011年 | 43篇 |
2010年 | 23篇 |
2009年 | 25篇 |
2008年 | 40篇 |
2007年 | 22篇 |
2006年 | 22篇 |
2005年 | 21篇 |
2004年 | 25篇 |
2003年 | 12篇 |
2002年 | 16篇 |
2001年 | 6篇 |
2000年 | 7篇 |
1999年 | 1篇 |
1998年 | 4篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 4篇 |
1992年 | 7篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1969年 | 3篇 |
1966年 | 1篇 |
排序方式: 共有481条查询结果,搜索用时 187 毫秒
21.
Neboja . Panteli Bojan Boi Bojana B. Zmejkovski Neboja R. Banjac Biljana Doj
inovi Ludger A. Wessjohann Goran N. Kaluerovi 《Molecules (Basel, Switzerland)》2021,26(11)
The synthesis of novel triphenyltin(IV) compounds, Ph3SnLn (n = 1–3), with oxaprozin (3-(4,5-diphenyloxazol-2-yl)propanoic acid), HL1, and the new propanoic acid derivatives 3-(4,5-bis(4-methoxylphenyl)oxazol-2-yl)propanoic acid, HL2, and 3-(2,5-dioxo-4,4-diphenylimidazolidin-1-yl)propanoic acid, HL3, has been performed. The ligands represent commercial drugs or their derivatives and the tin complexes have been characterized by standard analytical methods. The in vitro antiproliferative activity of both ligands and organotin(IV) compounds has been evaluated on the following tumour cell lines: human prostate cancer (PC-3), human colorectal adenocarcinoma (HT-29), breast cancer (MCF-7), and hepatocellular cancer (HepG2), as well as on normal mouse embryonic fibroblast cells (NIH3T3) with the aid of MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-12 diphenyltetrazolium bromide) and CV (crystal violet) assays. Contrary to the inactive ligand precursors, all organotin(IV) carboxylates showed very good activity with IC50 values ranging from 0.100 to 0.758 µM. According to the CV assay (IC50 = 0.218 ± 0.025 µM), complex Ph3SnL1 demonstrated the highest cytotoxicity against the caspase 3 deficient MCF-7 cell line. Inductively coupled plasma mass spectrometry (ICP-MS) analysis indicated a two-fold lower concentration of tin in MCF-7 cells in comparison to platinum. To investigate the mechanism of action of the compound Ph3SnL1 on MCF-7 cells, morphological, autophagy and cell cycle analysis, as well as the activation of caspase and ROS/RNS and NO production, has been performed. Results suggest that Ph3SnL1 induces caspase-independent apoptosis in MCF-7 cells. 相似文献
22.
23.
Miroslav M. Ristić Muna M. Aoneas Mirjana M. Vojnović Goran B. Poparić 《Plasma Chemistry and Plasma Processing》2017,37(5):1431-1443
Excitation of electronic states of the N2 molecule by electron impact is recognized as an essential process in nitrogen plasmas that strongly impacts their chemical reactivity and other properties. Many surface and coating technologies are based on radio-frequency plasma discharges in nitrogen. In this paper the electron impact excitation rate coefficients for singlet and triplet electronic states of the N2 molecule have been calculated in non-equilibrium conditions in the presence of a radio-frequency electric field. A Monte Carlo simulation has been performed in order to determine non-equilibrium electron energy distribution functions within one period of the electric field. By using these distribution functions, the excitation rate coefficients have been obtained in the frequency range from 13.56 up to 500 MHz, at reduced electric field values from 200 to 700 Td. 相似文献
24.
Electronic absorption spectroscopy was employed to study the aerial oxidation of catechol (1,2-benzenediol) in alkaline aqueous solution containing an excess of Mg(II) ions. Graphical analysis by the matrix method of UV spectra recorded at regular time intervals gave a good fit for two absorbing species in solution. Based on this result and our earlier ESR spectroscopic investigations we concluded that two main absorbing species in this system are Mg(II)-spin stabilized o-benzosemiquinone anion radical and C-C dimer formed by the nucleophilic attack of catecholate anion on o-benzoquinone. Although the formation of 1,2,4-benzenetriol during the catechol oxidation has been detected in some ESR studies its presence was not indicated by this analysis probably because of the low and/or stable steady state concentration throughout the experiment. 相似文献
25.
26.
27.
Angelovski G Costisella B Kolarić B Engelhard M Eilbracht P 《The Journal of organic chemistry》2004,69(16):5290-5294
Azamacrocyclic fluorophores containing piperazine units were synthesized using sequential rhodium-catalyzed regioselective hydroformylation-reductive amination. A piperazine unit is introduced into the macrocycles to act simultaneously as electron donor and binding site. The macrocycles chelate divalent cations, either Zn2+ or Co2+, which considerably enhanced fluorescence. Complexation with Zn2+ was additionally confirmed by NMR. 相似文献
28.
We study the second and third generation masses in the context of the minimal renormalizable SO(10) theory. We show that if the seesaw takes the noncanonical (type II) form, large atmospheric neutrino mixing angle requires b-tau unification. 相似文献
29.
Dukeson DR Ungar G Balagurusamy VS Percec V Johansson GA Glodde M 《Journal of the American Chemical Society》2003,125(51):15974-15980
A second generation monodendron with dodecyl end-groups based on the AB(3) monomer 3,4,5-trihydroxy benzoate has previously been shown to form a thermotropic cubic phase with Pmthremacr;n symmetry (Balagurusamy et al., J. Am. Chem. Soc. 1997, 119, 1539). A structure consisting of spherical "micelles" was proposed originally, but an alternative choice of structure factor phases, giving a structure of interlocked squashed columns, could not be ruled out by diffraction data on the original material alone. We have therefore synthesized two selectively fluorinated equivalent compounds, the carboxylic acid and its Rb salt, to be able to apply a variant of the isomorphous replacement crystallographic technique. On the basis of the electron density maps of the new labeled compounds, reconstructed using small-angle X-ray diffraction intensities, the interlocking columns model is unequivocally rejected and the spheres model is upheld. Furthermore, the location of the metal cation in the center of the "micelles" is directly confirmed. Micellar diameter was shown to decrease on fluorination of the dodecyl chain ends, and increase significantly on introduction of Rb. This is interpreted in terms of changes in the number of wedge-shaped dendrons fitting into a spherical micelle due to their changing taper angle. It was found that the Rb-rich regions at the centers of six out of eight "micelles" in the unit cell are elongated in the direction of their closest packing. This adds support to the suggestion of a partial "column-like" character of stacked rows of such micelles, consistent with the position of the Pmthremacr;n phase next to the columnar phase in the phase sequence of most taper-shape compounds. The results illustrate the potential of isomorphous replacement, used a great deal in protein crystallography, in structure investigation of liquid crystals and supramolecular soft matter. 相似文献
30.
Brendan D. Mckay Norman D. Megill Mladen Pavičic 《International Journal of Theoretical Physics》2000,39(10):2381-2406
We give a new algorithm for generating Greechie diagrams with arbitrary chosennumber of atoms or blocks (with 2, 3, 4, . . . atoms) and provide a computerprogram for generating the diagrams. The results show that the previous algorithmdoes not produce every diagram and that it is atleast 105 times slower. We alsoprovide an algorithm and programs for checking Greechie diagram passage byequations defining varieties of orthomodular lattices and give examples fromHilbert lattices. We also discuss some additional characteristics of Greechiediagrams. 相似文献