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61.
The results of kinetic, deuterium-labeling, and low-temperature NMR studies have established a mechanism for the palladium-catalyzed cyclization/hydrosilylation of dimethyl diallylmalonate (1) with triethylsilane involving rapid, irreversible conversion of the palladium silyl complex [(phen)Pd(SiEt(3))(NCAr)](+) [BAr(4)](-) [Ar = 3,5-C(6)H(3)(CF(3))(2)] (4b) and 1 to the palladium 5-hexenyl chelate complex [(phen)Pd[eta(1),eta(2)-CH(CH(2)SiEt(3))CH(2)C(CO(2)Me)(2)CH(2)CH=CH(2)]](+) [BAr(4)](-) (5), followed by intramolecular carbometalation of 5 to form the palladium cyclopentylmethyl complex trans-[(phen)Pd[CH2CHCH2C(CO2Me)2CH2CHCH2SiEt3](NCAr)]+ [BAr4]- (6), and associative silylation of 6 to release 3 and regenerate 4b. 相似文献
62.
Andrew D. Ross Diptarka Hait Valeriu Scutelnic Eric A. Haugen Enrico Ridente Mikias B. Balkew Daniel M. Neumark Martin Head-Gordon Stephen R. Leone 《Chemical science》2022,13(32):9310
X-ray Transient Absorption Spectroscopy (XTAS) and theoretical calculations are used to study CCl4+ prepared by 800 nm strong-field ionization. XTAS simultaneously probes atoms at the carbon K-edge (280–300 eV) and chlorine L-edge (195–220 eV). Comparison of experiment to X-ray spectra computed by orbital-optimized density functional theory (OO-DFT) indicates that after ionization, CCl4+ undergoes symmetry breaking driven by Jahn–Teller distortion away from the initial tetrahedral structure (Td) in 6 ± 2 fs. The resultant symmetry-broken covalently bonded form subsequently separates to a noncovalently bound complex between CCl3+ and Cl over 90 ± 10 fs, which is again predicted by theory. Finally, after more than 800 fs, L-edge signals for atomic Cl are observed, indicating dissociation to free CCl3+ and Cl. The results for Jahn–Teller distortion to the symmetry-broken form of CCl4+ and formation of the Cl–CCl+3 complex characterize previously unobserved new species along the route to dissociation.Dynamics of CCl4+ prepared by 800 nm strong-field ionization, as studied with X-ray transient absorption spectroscopy (XTAS) and quantum chemical calculations. 相似文献
63.
Steven Elder John Graham Roberson James Warren Robert Lawson Daniel Young Sean Stokes Matthew K. Ross 《Molecules (Basel, Switzerland)》2022,27(12)
In this study, kartogenin was incorporated into an electrospun blend of polycaprolactone and poly(lactic-co-glycolic acid) (1:1) to determine the feasibility of this system for sustained drug delivery. Kartogenin is a small-molecule drug that could enhance the outcome of microfracture, a cartilage restoration procedure, by selectively stimulating chondrogenic differentiation of endogenous bone marrow mesenchymal stem cells. Experimental results showed that kartogenin did not affect the electrospinnability of the polymer blend, and it had negligible effects on fiber morphology and scaffold mechanical properties. The loading efficiency of kartogenin into electrospun membranes was nearly 100%, and no evidence of chemical reaction between kartogenin and the polymers was detected by Fourier transform infrared spectroscopy. Analysis of the released drug using high-performance liquid chromatography–photodiode array detection indicated an abundance of kartogenin and only a small amount of its major hydrolysis product. Kartogenin displayed a typical biphasic release profile, with approximately 30% being released within 24 h followed by a much slower, constant rate of release up to 28 days. Although additional development is needed to tune the release kinetics and address issues common to electrospun scaffolds (e.g., high fiber density), the results of this study demonstrated that a scaffold electrospun from biodegradable synthetic polymers is a suitable kartogenin delivery vehicle. 相似文献
64.
Ross F. Koby Alicia M. Doerr Nicholas R. Rightmire Nathan D. Schley Dr. William W. Brennessel Prof. Brian K. Long Prof. Timothy P. Hanusa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(31):8195-8202
Without solvents present, the often far-from-equilibrium environment in a mechanochemically driven synthesis can generate high-energy, non-stoichiometric products not observed from the same ratio of reagents used in solution. Ball milling 2 equiv. K[A’] (A’=[1,3-(SiMe3)2C3H3]−) with CaI2 yields a non-stoichiometric calciate, K[CaA’3], which initially forms a structure ( 1 ) likely containing a mixture of pi- and sigma-bound allyl ligands. Dissolved in arenes, the compound rearranges over the course of several days to a structure ( 2 ) with only η3-bound allyl ligands, and that can be crystallized as a coordination polymer. If dissolved in alkanes, however, the rearrangement of 1 to 2 occurs within minutes. The structures of 1 and 2 have been modeled with DFT calculations, and 2 initiates the anionic polymerization of methyl methacrylate and isoprene; for the latter, under the mildest conditions yet reported for a heavy Group 2 species (one-atm pressure and room temperature). 相似文献
65.
66.
R. Meurice J. Cartiaux W. H. Ross K. C. Beeson L. M. White A. R. Merz K. Scharrer H. Schorstein R. Brill M. Popp H. Westerhoff H. Terlet A. Briau F. Kaminski F. Erdheim K. D. Jacob L. F. Rader Jr. T. H. Tremearne J. Contzen W. Sauerlandt Commission technique permanente de la Répression des Fraudes 《Analytical and bioanalytical chemistry》1941,122(5-6):230-237
67.
F. Nydahl W. D. Troadwell W. H. Ross A. R. Merz K. D. Jacob und P. Krumholz 《Fresenius' Journal of Analytical Chemistry》1943,126(9):342-347
Ohne Zusammenfassung 相似文献
68.
Mun BS Watanabe M Rossi M Stamenkovic V Markovic NM Ross PN 《The Journal of chemical physics》2005,123(20):204717
The surface valence-band densities of states (DOS) of Pt(3)M (M=Ti,V,Cr,Fe,Co,Ni) polycrystalline alloys were investigated with ultraviolet photoemission spectroscopy. Upon annealing the ion-sputter-cleaned alloys at high temperatures, the observed valence-band DOS spectra clearly show the modified electronic structures on the surfaces suggesting the surface segregation of Pt as predicted in thermodynamic models. The measured d-band centers and widths for the annealed alloy surfaces show qualitatively the same trend as predicted by density-functional-theory calculations based on the model of a Pt "skin" on the topmost surface layer and a subsurface layer enriched in the 3d transition metal. 相似文献
69.
70.