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251.
Using Dirichlet form techniques we prove existence of a diffusion process with singular drift on an open domain Ω???? d , d?∈??, d?≥?2, and generalized reflection at the boundary. The boundary is assumed to be C 2-smooth except for a sufficiently small set. We prove an elliptic regularity result which gives L p -strong Feller property for the semigroup and resolvent for p?≥?2 with $p > \frac{d}{2}$ . This result allows us to construct the process pointwisely except for an explicitly known set. For starting points outside this known set the process solves the corresponding martingale problem. The results are applied to prove the existence of the stochastic dynamics of a finite interacting particle system and for the Ginzburg-Landau interface model with a hard wall. 相似文献
252.
The tricyclic isoalloxazine nucleus of the redox cofactors flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) acts as an electron sink in life-sustaining biological electron transfer (eT). The functional diversity of flavin-containing proteins (flavoproteins) transcends that of free flavins. A large body of experimental evidence attributes natural control of flavoprotein-mediated eT to tuning of the thermodynamic driving force by the protein environment. Understanding and engineering such modulation by the protein environment of the flavin redox potential (DeltaE(o)) is valuable in biotechnology and device design. In this study we employed classical molecular dynamics free energy simulations (MDFES), within a thermodynamic integration (TI) formalism, to calculate the change in FMN first reduction potential (DeltaDeltaE(o)(ox/sq)) imparted by 6 flavoprotein active site mutations. The combined performance of the AMBER ff03 (protein) and GAFF (cofactor) force fields was benchmarked against experimental data for mutations close to the isoalloxazine re- and si-faces that perturb the wild-type DeltaE(o)(ox/sq) value in Anabaena flavodoxin. The classical alchemical approach used in this study overestimates the magnitude of DeltaE(o) values, in common with other studies. Nevertheless, chemically accurate DeltaDeltaE(o) values--calculated to within 1 kcal mol(-1) of the experimental value--were obtained for five of the six mutations studied. We have shown that this approach is practical for quantitative in silico screening of the effect of mutations on the first reduction potential where experimental values and structural data are available for the wild-type flavoprotein. This approach promises to be useful as an integral part of future interdisciplinary strategies to engineer desired thermodynamic properties in flavoproteins of biotechnological interest. 相似文献
253.
Benedict O'Donnell Linwei Yu Martin Foldyna Pere Roca i Cabarrocas 《Journal of Non》2012,358(17):2299-2302
Silicon nanowires offer an opportunity to improve light trapping in low-cost silicon photovoltaic cells. We have grown radial junctions of hydrogenated amorphous silicon over p-doped crystalline silicon nanowires in a single pump-down plasma enhanced chemical vapor deposition process on glass substrates. By using Sn catalysts and boosting p-type doping in the nanowires, the open-circuit voltage of the devices increased from 200 to 800 mV. Light trapping was optimized by extending the length of nanowires in these devices from 1 to 3 μm, producing currents in excess of – 13 mA cm? 2 and energy conversion efficiencies of 5.6%. The advantages of using thinner window layers to increase blue spectral response were also assessed. 相似文献
254.
Gunn E Sours R Benedict JB Kaminsky W Kahr B 《Journal of the American Chemical Society》2006,128(44):14234-14235
Rhythmic precipitates of centrosymmetric phthalic acid were analyzed by a square-wave mechanically modulated circular extinction imaging microscope. Spherulites were bisected into square-millimeter sized heterochiral domains that are a consequence of circular intensity differential scattering of left and right circularly polarized light. The dissymmetry and chiral amplification indicated optically was confirmed in the microtexture established by atomic force and scanning electron microscopies. 相似文献
255.
Lugo-Mas P Dey A Xu L Davin SD Benedict J Kaminsky W Hodgson KO Hedman B Solomon EI Kovacs JA 《Journal of the American Chemical Society》2006,128(34):11211-11221
256.
Benedict Gessendorfer Peter Koehler Herbert Wieser 《Analytical and bioanalytical chemistry》2009,395(6):1721-1728
Celiac disease (CD) is a permanent gastrointestinal disorder characterized by the intolerance to a group of proteins called
gluten present in wheat, rye, barley, and possibly oats. The only therapy is a strict lifelong gluten-free diet. The standard
method for gluten determination in foods produced for CD patients is the R5-enzyme-linked immunosorbent assay (ELISA) as proposed
by the recent Codex Alimentarius Draft Revised Standard. This test is based on the determination of prolamins, the alcohol-soluble
proteins of gluten, and is available as a sandwich ELISA for intact proteins and as a competitive ELISA for gluten-derived
peptides. While the suitability of the sandwich ELISA including a wheat prolamin (gliadin) reference for calibration has been
shown by various studies and a ring test, the competitive ELISA still lacks a convenient reference for the quantitation of
gluten peptides in fermented cereal foods (e.g., sourdough products, starch syrup, malt extracts, beer). Therefore, the aim
of the present study was to prepare a suitable reference for the quantitation of partially hydrolyzed gluten in fermented
wheat, rye, and barley products. The prolamin fractions from barley (hordein) and rye (secalin) were isolated from corresponding
flours by means of a modified preparative Osborne fractionation. The prolamin fraction from wheat was obtained as reference
gliadin from the Prolamin Working Group. The prolamin fractions were successively digested by pepsin and trypsin or pepsin
and chymotrypsin procedures, which have been used for CD-specific toxicity tests on cereal storage proteins for many years.
The protein/peptide content (N × 5.7) of the prolamin fractions and digests, which was the basis for the calculation of the
gluten content by means of ELISA, varied between 67.1% and 96.0%. The prolamin fractions and enzymatic digests were then tested
for their response in both sandwich and competitive assays. Intact prolamins responded similarly in both ELISA showing no
important differences between the cereals. In the case of digested proteins, however, the sandwich ELISA was considerably
less sensitive than the competitive ELISA. The former provided approximately 40% and the latter 70% of the signal intensity
obtained with the intact prolamins. Thus, the combination of the competitive ELISA and the enzymatic digests of prolamin fractions
as reference was considered to be an adequate system for the analysis of partially hydrolyzed gluten. The limit of detection
using a peptic-tryptic hordein digest as reference was 2.3 μg prolamin equivalent per milliliter, and the limit of quantitation
was 6.7 μg prolamin equivalent per milliliter. This system was applied for the determination of gluten equivalents in five
commercial beverages based on fermented cereals.
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