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991.
992.
Concentration of tracer at a producing well is a function of time and of the flow field that transports the tracer from one well to another. Small localized changes in the permeability and porosity fields result in small changes in the observed concentration history. Calculation of the effect of changes in the petrophysical parameter fields on observed concentration is an integral part of most approaches to solving the inverse problem, i.e. calculation of permeability and porosity fields that are consistent with observed tracer concentrations. This paper does not address the inverse problem directly, only the forward problem, but the results are presented as semi-analytic formulas which are intended to provide physical insight into the limitations of the inverse procedure. In particular, for a simple example of dipole flow between two wells in a nearly homogeneous infinite 2D porous medium, the width of the region of significant influence is shown to scale as d where is the dispersivity and d is half the interwell distance. Also, for fixed injection and production rates the influence on concentration of variation in porosity and in log-permeability are shown to be similar in magnitude. 相似文献
993.
Helmig D Revermann T Pollmann J Kaltschmidt O Jiménez Hernádez A Bocquet F David D 《Journal of chromatography. A》2003,1002(1-2):193-211
Sesquiterpenes (C15H24, SQT) are semi-volatile organic compounds emitted from vegetation and are of interest for air quality considerations because of their suspected contribution to the formation of secondary aerosol. This article investigates the application of a capillary diffusion method for the generation of standard atmospheres of 16 SQT and four other related semi-volatile compounds. This instrument subsequently has been used in the testing of analytical materials, protocols and calibration of air sampling methods. SQT DB-1 retention indices, vapor pressures at 25 and 75 degrees C, and diffusion coefficients were determined. A quantitative, on-line GC method yielded improved results (median relative standard deviation of 5.0-6.1%) for the diffusion rate determination in comparison to a gravimetric approach (median relative standard deviation 18%). The GC method also allowed identifying errors in the gravimetric method stemming from residual solvent evaporation, impurities, and chemical analyte losses. Stainless steel, glass, nickel and PTFE tubing that were tested for transfer lines and a sampling loop had to be kept at temperatures in excess of approximately 110 degrees C in order to prevent significant analytical errors from the stickiness of SQT to these materials. In addition to SQT analysis, results from this research provide general guidelines for gas-phase analysis of related compounds in the C14-C16 volatility range. 相似文献
994.
[reaction: see text] Conjugated oligomers with an alternating phenylene-pyrimidine structure have been synthesized by the successive Suzuki coupling reaction starting from 2-bromo-5-iodopyrimidine. The photoluminescence properties and quasi-reversible redox behavior of these oligomers make them applicable as an active material for a light-emitting device. Blue light-emitting electroluminescent devices with an external quantum efficiency up to 1.8% have been fabricated. 相似文献
995.
Silanolysis of B(O(t)Bu)(3) with 2 and 3 equiv of HOSi(O(t)Bu)(3) led to the formation of (t)BuOB[OSi(O(t)Bu)(3)](2) (1) and B[OSi(O(t)Bu)(3)](3) (2), respectively. Compounds 1 and 2 are efficient single-source molecular precursors to B/Si/O materials via thermolytic routes in nonpolar media, as demonstrated by the generation of BO(1.5).2SiO(2) (BOSi2(xg)) and BO(1.5).3SiO(2) (BOSi3(xg)) xerogels, respectively. Use of a block copolymer template provided B/Si/O materials (BOSi2(epe) and BOSi3(epe)) with a broad distribution of mesopores (by N(2) porosimetry) and smaller, more uniform particle sizes (by TEM) as compared to the nontemplated materials. Hydrolyses of 1 and 2 with excess H(2)O resulted in formation of the expected amounts of (t)BuOH and HOSi(O(t)Bu)(3); however, reaction of 1 with 1 equiv of H(2)O led to isolation of the new boronous acid HOB[OSi(O(t)Bu)(3)](2) (3). This ligand precursor is well suited for the synthesis of new metal (siloxy)boryloxide complexes via proton-transfer reactions involving the BOH group. The reaction of 3 with Cp(2)ZrMe(2) resulted in formation of Cp(2)Zr(Me)OB[OSi(O(t)Bu)(3)](2) (4) in high yield. This rare example of a transition metal boryloxide complex crystallizes in the triclinic space group Ponemacr; and exhibits a crystal structure with an unprecedented number of independent molecules in its asymmetric unit (i.e., Z' = 18 and Z = 36). This unusual crystal structure presented an opportunity to perform statistical analyses of the metric parameters for the 18 crystallographically independent molecules. Complex 4 readily converts to Cp(2)Zr[OSi(O(t)Bu)(3)](2) (5) upon thermolysis or upon dissolution in Et(2)O at room temperature. 相似文献
996.
The isochore concept in the human genome sequence was challenged in an analysis by the International Human Genome Sequencing Consortium (IHGSC). We argue here that a statement in the IHGSC's analysis concerning the existence of isochores is misleading, because the homogeneity was not examined at a large enough length scale and consequently an inappropriate statistical test was applied. A test of the existence of isochores should be equivalent to a test of homogeneity or equality of windowed GC%. The statistical test applied in the IHGSC's analysis, the binomial test, is a test of whether individual bases are independent and identically-distributed (iid). For testing the existence of isochores, or homogeneity in windowed GC%, we propose to use another statistical test: the analysis of variance (ANOVA). It can be shown that DNA sequences that are rejected by the binomial test may not be rejected by the ANOVA test. 相似文献
997.
The alpha-thiocarbocation generated from the Pummerer reaction of an o-benzoyl-substituted sulfoxide is intercepted by the adjacent keto group to produce an alpha-thio isobenzofuran as a transient intermediate which undergoes a subsequent Diels-Alder cycloaddition with added dienophiles. Acid-catalyzed ring-opening of the cycloadduct followed by aromatization gave an arylnaphthalene derivative. With acetylenic dienophiles, the tandem cyclization-cycloaddition sequence provided tetralones which result from a pinacol-type rearrangement of the primary cycloadducts. The versatility of the approach is highlighted through the synthesis of taiwanin C and E and justicidin E. The alpha-thiocarbocation generated from the Pummerer reaction of benzo[1,3]dioxol-5-yl-[6-[(ethylsulfinyl)methyl]benzo[1,3]dioxol-5-yl)methanone is intercepted by the adjacent keto group to produce an alpha-thioisobenzofuran as a transient intermediate which undergoes a subsequent Diels-Alder cycloaddition with dimethyl maleate. The initially formed Diels-Alder cycloadduct was readily converted to 5-benzo[1,3]dioxol-5-yl-8-(ethylthio)naphtho[2,3-d][1,3]dioxole-6,7-dicarboxylic acid dimethyl ester by loss of water on treatment with p-toluenesulfonic acid. Desulfurization of the thionaphthalene with Ra/Ni followed by hydrolysis of the less hindered methyl ester afforded 5-benzo[1,3]dioxol-5-ylnaphtho[2,3-d][1,3]dioxole-6,7-dicarboxylic acid 6-methyl ester which was further transformed into taiwanin C and justicidin E in good yield. Oxidation of the initial Diels-Alder cycloadduct with NaIO(4) in the presence of RuCl(3) followed by extrusion of ethyl sulfinate gave a naphthol derivative which can be converted into taiwanin E. 相似文献
998.
Bitterer F Herd O Hessler A Kühnel M Rettig K Stelzer O Sheldrick WS Nagel S Rösch N 《Inorganic chemistry》1996,35(14):4103-4113
Chiral water-soluble secondary phosphines (2-6) were obtained by nucleophilic phosphination of FC(6)H(4)-4-SO(3)K (1a), FC(6)H(3)-2,4-(SO(3)K)(2) (1b), and FC(6)H(4)-2-SO(3)K (1c) with RPH(2) (R = Ph, 2,4,6-Me(3)C(6)H(2), 2,4,6-iPr(3)C(6)H(2)) in the superbasic medium DMSO/KOH by employing steric control of substitution at phosphorus by bulky substituents R and sulfonic groups in the ortho position of the aromatic ring systems in 1b or 1c. The secondary phosphines may be deprotonated in DMSO/KOH to give phosphido anions which on reaction with alkyl halides (PhCH(2)Cl, Br(CH(2))(3)Br, and C(12)H(25)Br) yield mono- or bidentate tertiary phosphines (7-10). Ligands of this type are alternatively accessible by nucleophilic arylation of secondary phosphines, e.g. Ph(Me)PH or Ph(H)P(CH(2))(3)P(H)Ph with 1a or 1b, respectively. The crystal structure of the starting material 1b.H(2)O (space group P2(1)/m) has been determined. In the solid state of 1b.H(2)O the individual molecules are interconnected by ionic interactions between the potassium cations and the SO(3)(-) anions. The C-F bond (C(1)-F 1.347(4) ?) is shorter than that in C(6)H(5)F (1.356(4) ?). The unit cell of 7a.0.5H(2)O (space group P&onemacr;), the first structurally characterized chiral phosphine with a sulfonated phenyl substituent, contains the two enantiomers. Due to the asymmetrical substitution at phosphorus the PC(3) skeletons are significantly distorted (P(1)-C(1,11,31) 1.864(10), 1.825(8), 1.841(7) ?). The electronic structure of sulfonated fluorobenzenes FC(6)H(5)(-)(n)()(SO(3)M)(n)() (M = K, NH(4), n = 1-3) is discussed on the basis of quantum chemical calculations. In particular, the reactivity difference toward nucleophilic phosphination within the series is rationalized in terms of steric factors and of the -I effect of the sulfonic groups. 相似文献
999.
1000.
We investigate the primary, secondary, and vicinal hydrogen/deuterium (H/D) isotope effects on the geometry of the two intramolecular hydrogen bonds in porphycene. Multidimensional potential energy surfaces describing the anharmonic motion in the vicinity of the trans isomer are calculated for the different symmetric (HH/DD) and asymmetric (HD) isotopomers. From the solution of the nuclear Schr?dinger equation the ground-state wavefunction is obtained, which is further used to determine the quantum corrections to the classical equilibrium geometries of the hydrogen bonds and thus the geometric isotope effects. In particular, it is found that the hydrogen bonds are cooperative, that is, both expand simultaneously even in the case of an asymmetric isotopic substitution. The theoretical predictions compare favorably with NMR chemical-shift data. 相似文献