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41.
Oxidation of 1 with perbenzoic acid (p-toluene-sulphonic acid monohydrate as catalyst) provided novel oxetalactones 4 and 5 along with compounds 2 and 3. Treatment of 2 with perbenzoic acid yielded 4. A probable pathway for the formation of 4 from 1 involving the intermediacy of 2 has been suggested. 相似文献
42.
Summary Exact robustness studies against non-normality have been carried out for test of independence based on the four multivariate
criteria: Hotelling's trace,U
(p)
, Pillai's trace,V
(p)
, Wilks' criterion,W
(p)
, and Roy's largest root,L
(p)
. The density functions ofU
(p)
,W
(p)
andL
(p)
have been obtained in the canonical correlation case and further the moments ofU
(p)
and m.g.f. ofV
(p)
have been derived. All of the study is based on Pillai's distribution of the characteristic roots under violations. Numerical
results for the power function have been tabulated for the two-roots case. Slight non-normality does not affect the independence
test seriously.V
(2) is found to be most robust against nonnormality.
Yu-Sheng Hsu is now with Georgia State University, Atlanta. 相似文献
43.
44.
P. K. C. Pillai Brijesh K. Gupta Malti Goel 《Journal of Polymer Science.Polymer Physics》1981,19(9):1461-1470
The thermally stimulated current (TSC) technique has been used to study solvent-cast blends of a cellulose derivative with a vinyl polymer. TSC peaks are observed at 56, 80, and 120°C. Their origin is investigated because the TSC spectra of the blends differ from the spectra of the individual components. Data on blends with components in the weight ratios 25:75, 50:50, and 75:25 indicate that the 50:50 blend shows the greatest polarization. The enhancement of depolarization currents observed on blending is explained on the basis of a Maxwell–Wagner–Sillars polarization due to increased heterogeneity in the structure. Effects of forming conditions (time, temperature, field) on polarization have been investigated. Activation energies and relaxation times are calculated; there is good agreement between the values obtained from the initial-rise and the full-curve methods. 相似文献
45.
This review surveys the evolution of gas chromatographyic procedures for the quantification of barbiturates as either the free acids or their derivatives obtained by direct and on-column reactions. Among the aspects discussed, some emphasis is placed on recognized and other sources of interference encountered during analyses. 相似文献
46.
47.
[reaction: see text] The pyridine-mediated reaction of dimethyl acetylenedicarboxylate and cyclobutene-1,2-diones affords selective access to either hexasubstituted benzene derivatives or cyclopentenedione derivatives depending on the concentration of pyridine. 相似文献
48.
[reaction: see text] Pyridine catalyzes the reaction of 1,2-diaryl diones with dimethyl butynedioate to afford diaroyl maleates. This unprecedented rearrangement involves a unique benzoyl migration and proceeds with complete stereoselectivity. 相似文献
49.
Mesoporous iron phosphate is found to be a highly active and recyclable heterogeneous catalyst for the selective synthesis of nopol by Prins condensation of beta-pinene and paraformaldehyde in acetonitrile at 80 degrees C. 相似文献
50.
Menon S Vaidya H Pillai S Vidya R Mitscher LA 《Combinatorial chemistry & high throughput screening》2003,6(5):471-480
A solution phase strategy for the multiple parallel synthesis of a demonstration library of indazoles is described by which regio-selectivity problems inherent to previous syntheses of this nucleus are largely overcome. Synthesis of selected components proceeded satisfactorily indicating that a fully realized library of indazole analogs could readily be produced using this methodology. Simple modifications of the basic nucleophilic aromatic substitution route unambiguously produce a range of N-1 substitutions (alkyl, aryl and aralkyl) in 50-75% yields. Next a range of substituents was introduced at the C-3 position in 50-80% yields by O-alkylation. Careful choice of reagents and reaction conditions were required to prevent by-product formation due to competing alkylation at N-2 (trace to 15% yields). When present, these contaminants were readily removed by chromofiltration. A third diversity site was sketched in at C-5 in 75-90% yield by reductive alkylation or acylation. Screening of some of the demonstration library members in vitro revealed highly active antioxidants suggesting that producing a full library would be worthwhile. 相似文献