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941.
Alternative unidirectional methods for synthesizing methyl (methyl α-D-galactopyranosid)uronate and its mono-O-methyl ethers by the oxidation (with CrO3-H2SO4-acetone) of the corresponding methyl O-benzyl-O-methyl-α-D-galactopyranosides having unsubstituted 6-OH groups to the corresponding methyl O-benzyl-O-methyl-α-D-galactouronic acids followed by esterification with CH2N2 and the catalytic hydrogenolysis of the benzyl groups are proposed. 相似文献
942.
V.G. Kessler A.N. Panov N.Ya. Turova A.Yu. Borissevitch 《Journal of Sol-Gel Science and Technology》1997,8(1-3):1049-1051
The hydrolysis of solutions, containing either LiMo2O4(OPr
i
)5(
i
PrOH) and “La(OPr
i
)3” or LiOPr
i
and La2Mo4O8(OPr
i
)14 in 1∶1 ratio, in toluene or
i
PrOH, by water solutions in isopropanol, leads to formation of monolythic gels. The latter can be converted by drying and
heat treatment at 600°C into a fine powder of pure α-LiLaMo2O8 phase, which is transformed into β-LiLaMo2O8 powder by annealing at 800°C. The sintering of the pellets pressed under 4 bar pressure of α-LiLaMo2O8 powder at 800°C for 2 h converts them into pieces of β-LiLaMo2O8 transparent ceramics, thus providing a route to LiLnMo2O8 laser waveguide materials. 相似文献
943.
Use of synchronous first-derivative fluorimetry for determination of gentamycin is described. Gentamycin reacts with acetylacetone and formaldehyde in pH 5.6 HOAc/NaOAc buffer solution to form N-gentamyl-2,6-dimethyl-3,5-diacethyl-1,4-dihydropyridine[I] which is a fluorescent substance. Spectra of [I] and the reagent blank can be separated with synchronous derivative fluorimetry, and gentamycin can be determined directly. The synchronous spectral peaks of [I] and the reagent blank are at 434 and 411 nm, respectively. The first-derivative peak of [I] is at 425 nm. Effects of pH, foreign ions, buffer system, and heating time on the determination of gentamycin have been examined. The linear regression equation of the calibration graph is C=0.0513H-0.0416, with a correlation coefficient of linear regression of 0.9978. C means total potency of gentamycin: U ml(-1); H means peak height in the linear regression equation calibration graph. The linear range for the determination of gentamycin is from 0.00 to 3.00 U ml(-1). Recovery is from 95.06 to 112.0%, R.S.D. of 3.8%. The results determined by the fluorimetric method agreed roughly with those by the microbiological method. The method is simple and has low detection limit. 相似文献
944.
Song -Cheng Sun David E. Reed John K. Cullison Lyman H. Rickard Fred M. Hawkridge 《Mikrochimica acta》1988,96(1-6):97-104
The heterogeneous electron transfer reactions of cytochromec occurring at platinum, gold and mercury electrodes are shown to be quasi-reversible. In each case the electrodes have not been modified and the cytochromec samples are native. This work extends previous work and demonstrates that biological molecule electron transfer reactions can be studied at clean metal surfaces to gain fundamental knowledge of the mechanisms of these reactions. 相似文献
945.
946.
Popova L. A. Yurashevich N. Ya. Knizhnikov V. A. 《Russian Journal of Organic Chemistry》2004,40(3):311-315
Leucine methyl and ethyl esters reacted with 3-bromobenzaldehyde and 4-chlorobenzaldehyde in anhydrous methanol in the presence of magnesium sulfate to afford the coresponding Schiff bases of the general formula (CH3)2CHCH2CH(COOR1)N=CHR2 [R1 = CH3, C2H5, R2= 3-BrC6H4, 4-ClC6H4]. Their reduction with sodium tetrahydridoborate yielded N-benzyl derivatives (CH3)2CHCH2CH(COOR1)NHCH2R2, which were converted into N-acyl-N-benzyl derivatives (CH3)2CHCH2CH(COOR1)N(COR3)CH2R2[R3= CH3, C6H5]. 相似文献
947.
Ya‐Ping Du Ya‐Wen Zhang Prof. Dr. Zheng‐Guang Yan Dr. Ling‐Dong Sun Prof. Dr. Song Gao Prof. Dr. Chun‐Hua Yan Prof. Dr. 《化学:亚洲杂志》2007,2(8):965-974
We report the synthesis of single‐crystalline and near‐monodispersed NaMF3 (M=Mn, Co, Ni, Mg), LiMAlF6 (M=Ca, Sr), and NaMgF3:Yb,Er nanocrystals (quasisquare nanoplates, nanorods, and nanopolygons) by the cothermolysis of multiple trifluoroacetates in hot combined organic solvents (oleic acid, oleylamine, and 1‐octadecene). The nanocrystals were characterized by XRD, TEM, superconductive quantum interference device (SQUID), and upconversion luminescence spectroscopy. By regulating the polarity of the dispersant, the NaMF3 (M=Mn, Co, Ni) nanoplates were partially aligned to form nanoarrays on copper TEM grids. The sizes of the NaMF3 nanocrystals were easily tuned by the use of proper synthetic conditions such as reaction temperature and time and solvent composition. On the basis of a series of experiments in which the reaction conditions were varied, together with GC–MS and FTIR analysis, the reaction pathways for the formation of these nanocrystals from trifluoroacetate precursors were proposed. The magnetic measurements showed that the differently sized NaMnF3 square plates displayed interesting weak ferromagnetic behavior on the nanometer scale. The strong red upconversion luminescence emitted from the NaMgF3:Yb,Er nanorods under 980‐nm near‐IR laser excitation suggests that NaMgF3 may be a good candidate host material for red upconversion luminescence. 相似文献
948.
Juan Jos Berzas Nevado Rosa Carmen Rodríguez Martín-Doimeadis Francisco Javier Guzmn Bernardo Nuria Rodríguez Farias 《Microchemical Journal》2007,86(2):183-188
An analytical methodology was proposed and validated to be applied to the determination of p,p′-DDT and its metabolites p,p′-DDE and p,p′-DDD in fish oil. The analytical procedure presented in this paper involves a single-step clean up process prior to the analysis. A solution of 1,2,3,4-tetrachloronaphtalene was used as internal standard.The analytical technique used was gas chromatography coupled to an electron capture detector. Details on the validation process are provided.The limits of detection ranged from 2.6 to 4.7 pg μL− 1. The BCR 598 standard reference material (cod liver oil) was used to evaluate the performance of the methodology with satisfactory recoveries for all the compounds.The analytes were determined in three different fish oil pills sold in Spain as a supplementary vitamin support. The sum of p,p′-DDT and metabolites was from 13.2 to 51.3 ng g− 1, the dominant compound being p,p′-DDE. 相似文献
949.
Origins of enantioselectivity in reductions of ketones on cinchona alkaloid modified platinum 总被引:2,自引:0,他引:2
A model to explain the stereoselectivities of reductions of activated ketones on cinchona alkaloid modified platinum is proposed and is supported by calculations by density functional and force field methods. The model involves nucleophilic catalysis by the cinchona alkaloid. The zwitterionic adduct between a cinchona alkaloid and ketone is adsorbed on Pt through the quinoline ring and two heteroatoms and is subsequently reduced with inversion. The model rationalizes the observed stereoselectivities for hydrogenation of carbonyl compounds. 相似文献
950.
Witzmann FA Bauer MD Fieno AM Grant RA Keough TW Kornguth SE Lacey MP Siegel FL Sun Y Wright LS Young RS Witten ML 《Electrophoresis》1999,20(18):3659-3669
We analyzed protein expression in the cytosolic fraction prepared from whole lung tissue in male Swiss-Webster mice exposed 1 h/day for seven days to aerosolized JP-8 jet fuel at concentrations of 1000 and 2500 mg/m3, simulating military occupational exposure. Lung cytosol samples were solubilized and separated via large scale, high resolution two-dimensional electrophoresis (2-DE) and gel patterns scanned, digitized and processed for statistical analysis. Significant quantitative and qualitative changes in tissue cytosol proteins resulted from jet fuel exposure. Several of the altered proteins were identified by peptide mass fingerprinting, confirmed by sequence tag analysis, and related to impaired protein synthetic machinery, toxic/metabolic stress and detoxification systems, ultrastructural damage, and functional responses to CO2 handling, acid-base homeostasis and fluid secretion. These results demonstrate a significant but comparatively moderate JP-8 effect on protein expression and corroborate previous morphological and biochemical evidence. Further molecular marker development and mechanistic inferences from these observations await proteomic analysis of whole tissue homogenates and other cell compartment, i.e., mitochondria, microsomes, and nuclei of lung and other targets. 相似文献