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991.
Six kinds of benzo-15-crown-5 (L) adducts having the stoichiometric formula M(Pic)2 · L · xH2O (M=Mn, Cu, x=2; M=Co, Ni, Zn, Cd, x=4; Pic means picrate anion) have been synthesized and characterized by EA, IR, UV and molar conductance. The X-ray crystal structural analysis of the benzo-15-crown-5 adduct with hydrated copper(II) picrate revealed that the benzo-15-crown-5 molecule virtually acts as a second-sphere ligand, which associates with the copper(II) ion by hydrogen bonding of the coordinating water molecule. By the comparison of the IR, UV spectra and molar conductance of the new adducts prepared, it can be deduced that the other adducts exhibit the similar coordination environment to that of the copper adduct. 相似文献
992.
A series of [tetra-α-(2,2,4-tirmethyl-3-pentoxy) phthalocyaninato] metal complexes(M=Co, Ni, Cu, Zn)were prepared by cyclotetramerization of 3-(2,2,4-tirmethyl-3-pentoxy)phthalonitrile with corresponding anhydrous metal salts, using 1.8-diazabicyclo[5.4.0] undec-7-ene (DBU) as the catalyst. HPLC analysis shows that one isomer predominates in the product of nickel complex, while at least two main constitutional isomers exist in the product of other metal complexes. The complexes (in the form of mixture of constitutional isomers) were characterized by elemental analyses, MS, IR and UV-Vis spectroscopy. 相似文献
993.
Yi-min HuJie Zhou Xiang-tian LongJian-lin Han Chen-jian ZhuYi Pan 《Tetrahedron letters》2003,44(27):5009-5010
Reaction of benzyl halides with N-allyl-N-(2-butenyl)-p-toluenesulfonamide 1 in the presence of a palladium catalyst afforded dihydropyrroles 3 in moderate to excellent yields. It is proposed that the cyclic products were formed via a palladium-catalyzed cascade cyclization-coupling process. 相似文献
994.
A dual-ESI-sprayer system was constructed and applied to achieve high accuracy of peptide mass measurement for protein identification by means of peptide mapping. Sample was introduced in one sprayer, and reference in the other, thus making internal calibration possible greatly enhancing the mass accuracy. Several samples were utilized to evaluate the reliability of this dual-ESI-sprayer system. The range of mass errors was 0.16-5.37 ppm. The peptide masses of tryptic digests of myoglobin (horse) were measured by the HPLC/dual-ESI-MS system, with mass deviations ranging from 0.01-7.67 ppm, and about 75% mass deviations below 5 ppm with 40% below 1[?]ppm. These peptide masses were utilized to perform database searching for protein identification, and compared to results obtained by external calibration. This comparison showed that the internal calibration provides a more reliable method of protein identification, with a much smaller number of required peptides for matching, and with less CPU time consumed for database searching. 相似文献
995.
Summary A sensitive LC method for the detection of amino acids and oligopeptides with pre-column fluorescence derivatization has been
developed. Glycine, glycylglycine, triglycine, glutathione, glutamic acid, and cysteine were separated on a reversed-phase
C18 column with methanol-water-triethylamine eluent, derivatization and chromatographic conditions were optimized. The six derivatives
were eluted in 20 min with good reproducibility. The relative standard derviations (n=6) at an analytical concentration of
2×10−6 M are <5%. Detection limits (signal-to-noise ratio=3) for the six derivatives are 23–68 fmol. 相似文献
996.
997.
Pan J Song Q Shi H King M Junga H Zhou S Naidong W 《Rapid communications in mass spectrometry : RCM》2004,18(21):2549-2557
A highly sensitive bioanalytical method based on a simple liquid/liquid extraction and hydrophilic interaction liquid chromatography with tandem mass spectrometry (HILIC/MS/MS) analysis has been developed, validated and transferred for the determination of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), a tobacco-specific nitrosamine metabolite. Deuterated NNAL (NNAL-d(4)) was synthesized and used as the internal standard. This method can be used for the analysis of free and total NNAL (free NNAL plus NNAL-gluc) in K(3)-EDTA human plasma. Free NNAL and NNAL-d(4) are extracted from human plasma by liquid/liquid extraction. To analyze for total NNAL and the internal standard, a separate aliquot of the K(3)-EDTA human plasma is treated with beta-glucuronidase to deconjugate the NNAL-gluc; the total NNAL and internal standard are then extracted using liquid/liquid extraction. After drying down under nitrogen, the residue is reconstituted with acetonitrile and analyzed using positive ion electrospray and HILIC/MS/MS at a flow rate of 1.0 mL/min. The chromatographic run time is 1.0 min per injection, with retention time for both NNAL and NNAL-d(4) of 0.75 min with a capacity factor (k') of 2. The standard curve range for this assay is from 5.00-1000 pg/mL for both free and total NNAL, using a total plasma sample volume of 1.0 mL. The interday precision and accuracy of the quality control (QC) samples demonstrated <7.6% relative standard deviation (RSD) and <3.3% relative error (RE) for free NNAL. For total NNAL, the interday precision and accuracy of the QC samples demonstrated <11.7% RSD and <2.8% RE. Optimization of enzyme hydrolysis of NNAL-gluc is discussed in detail. The overall recoveries for free and total NNAL and IS were 68.2 and 71.5% (free) and 70.7 and 65.5% (total). No adverse matrix effects were noticed for this assay. 相似文献
998.
Layered compounds have been synthesized and structurally characterized for the n=5 and 6 members of the perovskite-related family La4Srn−4TinO3n+2 by combining X-ray diffraction and transmission electron microscopy. Their structure can be regarded as comprising [(La,Sr)5Ti5O17] and [(La,Sr)6Ti6O20] perovskite blocks joined by crystallographic shears along the a-axis, with consecutive blocks shifted by 1/2 [100]p. The n=5 member is similar to the previously reported n=5 member of other AnBnO3n+2-related series. The n=6 member, which has only been briefly reported in other systems previously, is also a well-behaved member of this AnBnO3n+2 series. 相似文献
999.
The relative stabilities of thiourea in water are investigated computationally by considering thiourea–water complexes containing up to 1–6 water molecules (CS(NH2)2(H2O)n=1–6) using density functional theory and MP2 ab initio molecular orbital theory. The results show that the thiourea complex is stable and has an unusually high affinity for incoming water molecules. The clusters are progressively stabilized by the addition of water molecules, as indicated by the increasing of the binding energy. The binding energy of the cluster to each H2O molecule is about 33 kJ mol−1 for n=1–5.The C–S bond, N–C bond distance, Mulliken populations and binding energy keep approximately constant as the clusters increase in size with an increasing number of H2O molecules. As the solvation progresses, the C–S distance increases monotonically while the Mulliken populations on the C–S bond reduces monotonically with the addition of each H2O molecule, indicating that the C–S bond of the thiourea unit in the clusters is de-stabilized with an increasing number of H2O molecules. Charge transfers for the clusters are mainly found at N, S atoms of the thiourea. 相似文献
1000.
A method is presented that allows novel measurement of the effect of microstructure on the oxygen permeability of highly condensed, polycrystalline phospholipid monolayers. Oxygen permeability of the polycrystalline shell coating a stationary microbubble is measured directly using an apposing microelectrode in the induced transfer mode and modeling oxygen flux through the shell and intervening aqueous medium. Varying cooling rate through the phospholipid main phase transition permits control of shell microstructure by manipulation of crystalline domain size and shape. Domain boundary density, defined as the ratio of the mean domain perimeter to the mean domain area, of the microbubble shell is determined by fluorescence microscopy. Oxygen permeability was shown to increase linearly with domain boundary density at a constant phospholipid acyl chain length and, accordingly, was shown to decrease exponentially with increasing chain length at a constant domain boundary density. Modification of the energy barrier theory to account for microstructural effects, in terms of the domain boundary density, provides a general equation to model passive transport through polycrystalline monolayer films. Results from this method show promise in determining the gas transport kinetics of medical microbubbles and the gas exchange characteristics of biological monolayers. 相似文献