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1.
Morelos A Albuquerque IF Bondar NF Carrigan RA Chen D Cooper PS Lisheng D Denisov AS Dobrovolsky AV Dubbs T Endler AM Escobar CO Foucher M Golovtsov VL Gottschalk H Gouffon P Grachev VT Khanzadeev AV Kubantsev MA Kuropatkin NP Lach J Lang Pengfei Li Chengze Li Yunshan Luksys M Mahon JR McCliment E Newsom C Pommot Maia MC Samsonov VM Schegelsky VA Shi Huanzhang Smith VJ Tang Fukun Terentyev NK Timm S Tkatch II Uvarov LN Vorobyov AA Yan Jie Zhao Wenheng Shuchen Z Zhong Yuanyuan 《Physical review letters》1993,71(21):3417-3420
2.
Morelos A Albuquerque IF Bondar NF Carrigan RA Chen D Cooper PS Dai Lisheng Denisov AS Dobrovolsky AV Dubbs T Endler AM Escobar CO Foucher M Golovtsov VL Gottschalk H Gouffon P Grachev VT Khanzadeev AV Kubantsev MA Kuropatkin NP Lach J Lang Pengfei Li Chengze Li Yunshan Luksys M Mahon JR McCliment E Newsom C Pommot Maia MC Samsonov VM Schegelsky VA Shi Huanzhang Smith VJ Tang Fukun Terentyev NK Timm S Tkatch II Uvarov LN Vorobyov AA Yan Jie Zhao Wenheng Zheng Shuchen Zhong Yuanyuan 《Physical review letters》1993,71(14):2172-2175
3.
The synthesis of methyl 1,2,9,9a-tetrahydrocyclopropa[c]pyrido[3, 2-e]indol-4-one-7-carboxylate (CPyI) containing a one carbon expansion of the C ring pyrrole found in the duocarmycin SA alkylation subunit and its incorporation into analogues of the natural product are detailed. The unique 8-ketoquinoline structure of CPyI was expected to provide a tunable means to effect activation via selective metal cation complexation. The synthesis of CPyI was based on a modified Skraup quinoline synthesis followed by a 5-exo-trig aryl radical cyclization onto an unactivated alkene with subsequent TEMPO trap or 5-exo-trig aryl radical cyclization onto a vinyl chloride for synthesis of the immediate precursor. Closure of the activated cyclopropane, accomplished by an Ar-3' spirocyclization, provided the CPyI nucleus in 10 steps and excellent overall conversion (29%). The evaluation of the CPyI-based agents revealed an intrinsic stability comparable to that of CC-1065 and duocarmycin A but that it is more reactive than duocarmycin SA and the CBI-based agents (3-4x). A pH-rate profile of the addition of nucleophiles to CPyI demonstrated that an acid-catalyzed reaction is observed below pH 4 and that an uncatalyzed reaction predominates above pH 4. The expected predictable activation of CPyI by metal cations toward nucleophilic addition was found to directly correspond to established stabilities of the metal complexes with the addition product (Cu(2+) > Ni(2+) > Zn(2+) > Mn(2+) > Mg(2+)) and provides the opportunity to selectively activate the agents upon addition of the appropriate Lewis acid. This tunable metal cation activation of CPyI constitutes the first example of a new approach to in situ activation of a DNA binding agent complementary to the well-recognized methods of reductive, oxidative, or photochemical activation. Resolution and synthesis of a full set of natural product analogues and subsequent evaluation of their DNA alkylation properties revealed that the CPyI analogues retain identical DNA alkylation sequence selectivity and near-identical DNA alkylation efficiencies compared to the natural products. Consistent with past studies and even with the deep-seated structural change in the alkylation subunit, the agents were found to exhibit potent cytotoxic activity that directly correlates with their inherent reactivity. 相似文献
4.
Teixeira-Neto É Leite CA Cardoso AH Medeiros da Silva MC Braga M Galembeck F 《Journal of colloid and interface science》2000,231(1):182-189
Poly(styrene-co-acrylamide) (PS-AAM) latex was prepared, fractionated by sedimentation under gravity, and characterized by PCS, infrared spectra, secondary and backscattered electron imaging in the scanning electron microscope, and electron spectroscopy imaging in an analytical transmission electron microscope. Three latex fractions were obtained. The lower fraction was opalescent and its particles were the more uniform, concerning size, chemical composition, and topochemical features. This lower fraction was still further fractionated by zonal centrifugation in a density gradient, yielding two fractions with similar macrocrystal-forming abilities but different sizes and chemical compositions. These results confirm those previously obtained for the PS-HEMA latex. Copyright 2000 Academic Press. 相似文献
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Umme Kalsoom Michael C. Breadmore Rosanne M. Guijt Mary C. Boyce 《Electrophoresis》2014,35(23):3379-3386
Osmoregulants are the substances that help plants to tolerate environmental extremes such as salinity and drought. Proline and betaine are two of the most commonly studied osmoregulants. An indirect UV CE method has been developed for simultaneous determination of these osmoregulants. A variety of reported probes and compounds were examined as potential probes for the indirect detection of proline and betaine. Mobility and UV‐absorption properties highlighted sulfanilamide as a potential probe for indirect analysis of proline and betaine. Using 5 mM sulfanilamide at pH 2.2 with UV detection at 254 nm, proline and betaine were separated in less than 15 min. The LODs for proline and betaine were 11.6 and 28.3 μM, respectively. The developed method was successfully applied to quantification of these two osmoregulants in spinach and beetroot samples. 相似文献
9.
A concise, efficient approach to the total synthesis of ningalin B (1) based on a heterocyclic azadiene Diels-Alder strategy (1,2,4,5-tetrazine-->1,2,-diazine-->pyrrole) ideally suited for construction of the densely functionalized pyrrole core found in the natural product is detailed. Examination of the natural product and a number of synthetic intermediates revealed that while lacking inherent cytotoxic activity, many reverse the multidrug-resistant (MDR) phenotype, resensitizing a human colon cancer cell line (HCT116/VM46) to vinblastine and doxorubicin at lower doses than the prototypical agent verapamil. 相似文献
10.
We report what is believed to be the first observation of a nonlinear mode in a cylindrical nonlinear Fabry-Perot cavity. The field enhancement from cavity buildup, as well as the large chi((3)) optical nonlinearity that is due to resonantly excited (85)Rb vapor, allows the nonlinear mode to form at low incident optical powers of less than 1 mW. The mode is observed to occur for both self-focusing and self-defocusing nonlinearity. 相似文献