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71.
William R. Roush Michael A. Marletta Sandra Russo-Rodriguez Joanne Recchia 《Tetrahedron letters》1985,26(43):5231-5234
The preparation and structure determination of the title compound is described. 相似文献
72.
A study of the adsorptive stripping voltammetry of cadmium and zinc is reported in which ligands containing sulphur donor atoms were examined. This type of ligand showed good adsorptive behaviour and strong metal complexation. It was found that the ligand 2,5-dimer-capto-1,3,4-thiadiazole (DMTD) was very suitable for the determination of cadmium and zinc using this technique.The method was applied to the direct determination of these metals in biological samples using benzyl trimethylammonium methoxide as digesting solvent for the samples. 相似文献
73.
74.
Singh SB Zink DL Doss GA Polishook JD Ruby C Register E Kelly TM Bonfiglio C Williamson JM Kelly R 《Organic letters》2004,6(3):337-340
[structure: see text] Screening of natural products extracts led to the discovery of citrafungins A and B, two new fungal metabolites of the alkylcitrate family that are inhibitors of GGTase I of various pathogenic fungal species with IC(50) values of 2.5-15 microM. These compounds exhibited antifungal activities with MIC values of 0.40-55 microM. The isolation, structure elucidation, relative and absolute stereochemistry, and biological activities of citrafungins are described. 相似文献
75.
Carroll AR Arumugan G Quinn RJ Redburn J Guymer G Grimshaw P 《The Journal of organic chemistry》2005,70(5):1889-1892
Two novel indolizidine alkaloids, grandisine A (1) and B (2), and the known alkaloid (-) isoelaeocarpiline (3) were isolated from the leaves of Elaeocarpus grandis and their structures determined by 1D and 2D NMR spectroscopy. The compounds showed affinity for the human delta-opioid receptor. Grandisine A contains a unique tetracyclic skeleton, while grandisine B possesses the unique combination of isoquinuclidinone and indolizidine groups in one molecule. 相似文献
76.
Joanne Davies 《Analytica chimica acta》2003,479(2):215-223
In thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) a nickel atomization tube is placed in the acetylene/air flame on a holder built onto a standard AAS burner head. The liquid to be analyzed is transported by a low or high-pressure pump through a very hot, simple, inexpensive ceramic capillary tip acting as a flame-heated thermospray into the flame furnace. This results in complete sample introduction and increases the residence time of the sample in the absorption volume. This leads for 17 elements to a 3-110-fold improvement in the power of detection compared to conventional flame AAS. The absolute detection limits (3s values, N=25) lie between 0.2 μg l−1 (Zn) and 310 μg l−1 (Se) according to the element. The R.S.D. (N=15) is 1.4-5.5% according to the element and applied concentration. TS-FF-AAS can easily be incorporated on any standard flame AAS instrument and can be automated with a standard autosampler. 相似文献
77.
1,3-Dimethyl-1,2-dihydro-2-imino-4(3H)pyrimidinone (1,3-dimethylisocytosine) was prepared by methylation of 2-amino-3-methyl-4(3H)pyrimidinone and was degraded in alkaline solution to a mixture of 3-methyl-2-methylamino-4(3H)pyrimidinone, 1,3-dimethyl-2,4-(1H,3H)pyrimid-indione, 2-methylamino-l-methyl-4(1H)pyrimidinone, 1-methyl-2,4-(1H,3H)pyrimidindione and 3-methyl-2,4-(1H,3H)pyrimidindione. Thiation of the title compound gave both 1,2-dihydro-1,3-dimethyl-2-thio-4(3H)pyrimidinone and 1,3-dimethyl-2,4-(1H,3H)pyrimidinedithione. The title compound is a tautomerically fixed pyrimidine and its uv spectra were compared with related compounds, notably 3-methyl-2-dimethylarnino-4(3H)pyrimidinone which is also tautomerically fixed. 相似文献
78.
Katherine M. Phillips Wayne R. Wolf Kristine Y. Patterson Katherine E. Sharpless Karen R. Amanna Joanne M. Holden 《Accreditation and quality assurance》2007,12(3-4):126-133
Certified reference materials (CRMs) play a critical role in validating the accuracy of nutrient data for food samples. A
number of available food CRMs of differing matrix composition have assigned concentrations for various nutrients, along with
associated uncertainty intervals (UIs) for those values. These CRMs have been used extensively in the United States Department
of Agriculture’s (USDA) ongoing National Food and Nutrient Analysis Program (NFNAP) to monitor the accuracy of assays of key
foods and nutrients consumed in the United States. A total of 690 assigned values for individual nutrients, including proximates,
vitamins, macroelements, microelements, fatty acids, amino acids, and selected phytochemicals (e.g., carotenoids), were compiled
from the certificates of analysis for 63 CRMs, and the specified UI in each case was expressed as a percentage of the assigned
certified or reference concentration. Across all nutrients, 63.5% of the UIs were less than 10% of the assigned value, 25.5%
were 10–20%, and 11% were greater than 20% of the assigned value. The UIs for proximates, minerals, and trace elements were
most consistently less than 10% of the assigned value. The relative uncertainties were significantly higher for vitamins,
suggesting greater challenges in measuring and certifying these components. These high UIs (greater than 10% assigned value)
in the best available reference materials are likely to be indicative of the precision and accuracy that can be obtained by
current measurement systems for these components. These data suggest that care must be taken in choosing CRMs to monitor food
composition analysis, including evaluating what levels of uncertainty are required in assigned values and which analytical
measurement systems for food components need closer examination and improvement.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Presented at ‘BERM-10’, April 2006, Charleston, SC, USA. 相似文献
79.
Paci P Zvinevich Y Tanimura S Wyslouzil BE Zahniser M Shorter J Nelson D McManus B 《The Journal of chemical physics》2004,121(20):9964-9970
We used a tunable diode laser absorption spectrometer to follow the condensation of D(2)O in a supersonic Laval nozzle. We measured both the concentration of the condensible vapor and the spectroscopic temperature as a function of position and compared the results to those inferred from static pressure measurements. Upstream and in the early stages of condensation, the quantitative agreement between the different experimental techniques is good. Far downstream, the spectroscopic results predict a lower gas phase concentration, a higher condensate mass fraction, and a higher temperature than the pressure measurements. The difference between the two measurement techniques is consistent with a slight compression of the boundary layers along the nozzle walls during condensation. 相似文献
80.
Peter W. Moore Julia K. Schuster Russell J. Hewitt M. Rhia L. Stone Paul H. Teesdale-Spittle Joanne E. Harvey 《Tetrahedron》2014
The ring opening of 1,2-(gem-dibromo)cyclopropyl carbohydrates by two different modes leads to either 2-C-(bromomethylene)pyranosides (using base) or 2-bromooxepines (using silver salts), as shown previously by us for a d-glucal-derived cyclopropane. The base-promoted ring opening is extended to encompass additional alcohol, thiol and amine nucleophiles, and diastereoisomeric cyclopropane precursors. Cross-coupling of the 2-C-(bromomethylene)pyranosides leads to extended 2-C-branched pyranosides. Silver-promoted ring expansion of the cyclopropyl carbohydrates in the presence of various alcohols is described. Cross-coupling of the resulting benzyl 2-bromooxepines affords 2-C-substituted oxepines. 相似文献