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81.
UV.-irradiation (λ ≥ 327 nm) of the α,β-unsaturated γ,δ-epoxy ketone 2 in pentane gives the isomers oxidoketone 3 and diketone 4, in high yield. On treatment with BF3O(C2H5)2, 2 undergoes rearrangement to the diketone 4 and the isomeric lactone 8 and yields also the dimer 9. 相似文献
82.
Grancher D Jaussaud P Durix A Berthod A Fenet B Moulard Y Bonnaire Y Bony S 《Journal of chromatography. A》2004,1059(1-2):73-81
This paper describes a new method of purification of the Lolitrem B, a tremorgenic mycotoxin produced in planta by the endophytic fungus Neotyphodium lolii. The method is based on the large-scale isolation of the toxin by countercurrent chromatography (CCC). The lolitrem B content in endophyted ryegrass seed, 11 microg/g or 11 ppm, is extracted by stirring finely ground seeds with ethanol for 3 h at room temperature. The concentrated crude extract contains about 0.6 mg/g or 600 ppm of lolitrem B. It is then submitted to CCC purification with a biphasic four-solvent liquid system. A 160-fold enrichment was obtained in one step producing a raffinate containing 10% or 100 mg/g of the toxin. Further purifications were then performed by thin layer and low pressure liquid chromatography. Twenty-eight micrograms of lolitrem B with a 96% purity grade were obtained from 8 kg of seeds (yield 32%). 相似文献
83.
Spontaneous Nef reaction of primary and secondary 3-aryl-2-(diethoxyphosphoryl)-4-nitroalkanoic acids has been observed for the first time. The reaction provides a general and effective, highly diastereoselective synthesis of 3-(diethoxyphosphoryl)-1-hydroxysuccinimides and 2-(diethoxyphosphoryl)-4-oxoalkanoic acids. 相似文献
84.
I. V. Ajinenko Y. A. Belokopitov A. A. Borovikov P. V. Chliapnikov Z. C. Garutchava L. N. Gerdyukov S. A. Gumenuk V. V. Kniazev A. I. Kurnosenko L. V. Orekhova L. P. Petrovikh V. N. Riadovikov A. G. Tomaradse V. A. Uvarov A. P. Vorobjev N. S. Amaglobely Ch. S. Chochiachvili M. Barth E. A. De Wolf M. Van Immerseel F. Verbeure CERN - USSR Collaboration 《Zeitschrift fur Physik C Particles and Fields》1984,25(2):103-114
We present final results on inclusive production ofK *+(890),K *+(1430) andK *?(890) in \(\bar K^ + p\) interactions at 32 GeV/c, based on a statistics of ~27 events/μb. Total cross sections,p T -andx-dependence of inclusive distributions are compared with experiments at other energies and with the Lund fragmentation model. Spin density matrix elements of theK *+(890) are also discussed. The results suggest that “recombination” of both initial state valence quarks \(\bar s\) andu of theK + intoK *+(890), responsible in the Lund model for ~45% of theK *+(890) cross section, is strongly suppressed. 相似文献
85.
I. V. Ajinenko P. V. Chliapnikov V. P. Falaleev Z. C. Garutchava L. N. Gerdyukov V. V. Kniazev A. I. Kurnosenko T. G. Makharadze V. N. Riadovikov A. M. Rybin A. G. Tomaradze O. G. Tchikilev V. F. Tchunikhin V. A. Uvarov A. P. Vorobjev N. S. Amaglobely Ch. S. Chochiachvili M. D. Tabidze M. Barth E. A. De Wolf M. Van Immerseel F. Verbeure CERN-USSR Collaboration 《Zeitschrift fur Physik C Particles and Fields》1984,23(4):307-331
The production properties ofK s 0 , \(\bar \Lambda\) andK + p interactions at 32 GeV/c are investigated using the final statistics of the experiment. We present total and semi-inclusive cross sections and aver-age multiplicities. Estimates are given of the diffractive dissociation contributions to total and differential cross sections. Thex-,p T ?, and transverse mass dependence of inclusive and semi-inclusive distributions is discussed as well as properties of “prompt”K s 0 's. The ratio of “prompt”K 890 + (K 890 0 ) to “prompt”K 0 cross sections is measured to be 1.03±0.12 (0.98±0.17). From a comparison of \(\bar \Lambda\) production inK ± p interactions at 32 GeV/c, we estimate a strange sea-quark suppression of 0.26 ±0.02. The double differential cross sections ofK s 0 's is studied as a function of Feynman-x andp T 2 , and a Triple-Regge fit performed. The data are compared in detail to versions of the Lund-model for low-p T hadronic collisions. 相似文献
86.
Mikosch J Kreckel H Wester R Plasil R Glosík J Gerlich D Schwalm D Wolf A 《The Journal of chemical physics》2004,121(22):11030-11037
Infrared absorption spectroscopy of few hundred H+(3) ions trapped in a 22-pole ion trap is presented using chemical probing as a sensitive detection technique down to the single ion level. By exciting selected overtone transitions of the (v(1)=0,v(2) (l)=3(1))<--(0,0(0)) vibrational band using an external cavity diode laser an accurate diagnostics measurement of the effective translational and rotational temperatures of the trapped ions was performed. The absolute accuracy of the measured transition frequencies was improved by a factor of four compared to previous plasma spectroscopy measurements using velocity modulation [Ventrudo et al., J. Chem. Phys. 100, 6263 (1994)]. The observed buffer gas cooling conditions in the ion trap indicate how to cool trapped H+(3) ions into the lowest ortho and para rotational states. Future experiments will utilize such an internally cold ion ensemble for state-selected dissociative recombination experiments at the heavy ion storage ring Test Storage Ring (TSR). 相似文献
87.
This paper reports the results of the interlaboratory peer validation study of AOAC Peer-Verified Method (PVM) 1:2,000 for the determination of niacin in infant formula by solid-phase extraction/liquid chromatography. We have used a Data Quality Objectives (DQO) approach to address not only method variability and robustness but also accuracy of data through the use of an appropriate reference material in conjunction with the interlaboratory validation study. Our DQO included the following: (1) statistical agreement of analytical results and quantitative recovery between 2 collaborating laboratories; (2) the repeatability relative standard deviation (RSDr) values and the HORRAT (Horwitz ratio) obtained (1.07), which satisfied the criteria of the Horwitz "limits of acceptability" at the analyte level present; (3) validation of lack of interference; and (4) accuracy agreement within assigned values for a certified reference material. National Institute of Standards and Technology Standard Reference Material (NIST SRM) 1846 Infant Formula, with a certified value of 63.3 +/- 7.6 microg/g for niacin content, was used as a test material for collaborative study and accuracy assessment. Niacin values obtained by the originating laboratory were 59.7 +/- 4.0 microg/g (95% confidence interval [CI] = 1.4 microg/g with a relative standard deviation [RSD] of 6.7%) and by the peer laboratory were 56.6 +/- 6.6 microg/g (95% CI = 4.1 microg/g, with an RSD of 11.7%). Statistical evaluation using the means equivalence test showed that nicotinic acid values obtained by the peer laboratory were equivalent to those values obtained by the originating laboratory. Linear calibration curves and quantitative recovery were obtained. Integration of the PVM process with a readily available certified reference material gives the user confidence in the accuracy of the data generated by the method through traceability to the reference material used. 相似文献
88.
The Chemical Transport of VO2 with Cl2 and HCl + Cl2 and the Influence of the O2-Coexistence Equilibrium Pressure on the Transport Behaviour The transport behaviour of VO2 with Cl2, HCl, and Cl2 was calculated and compared with the experimental results. VO2 with the upper phase boundary transports with HCl and HCl + Cl2 from the colder to the hotter zone, VO2 of the lower phase boundary does not transport with HCl. The composition of the deposited VO2 is near the upper boundary oxygen richer than in the start space. VO2 does not transport with Cl2. 相似文献
89.
Thermodynamics of the System Si? Cl? H By static and dynamic methods the equilibria 4SiHCl3,g = 3SiHCl4,g + Si,s + 2H2,g (1) between 800 and 1140 K and SiCl4,g + H2,g = SiHCl3,g + HCl,g (2) between 1170 and 1450 K were investigated. The expression for the temperature dependence of the equilibria were found to be lg Kp [Torr] = (5.688–1520/T) ± 0.32 (1) and lg Kp = (1.38/3250/T) ± 0.16 (2). The values measured for reaction pressures and equilibrium constants lead to the conclusion, that the difference of enthalpies of formation of SiCl4 and SiHCl3 found in literature is nessecarily to be corrected by 5–6 kcal/mole. With ΔH(SiCl4,g) = ?157.1 kcal/mole the equilibrium measurements lead to the enthalpy of formation for SiHCl3,g of ΔH(SiHCl3,g) = ?118.2 kcal/mole. 相似文献
90.
Werner H Schwab P Bleuel E Mahr N Windmüller B Wolf J 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(24):4461-4470
A series of carbenerhodium(I) complexes of the general composition [(eta5-C5H5)Rh(=CRR')(L)] (2a-2i) with R = R'= aryl and L = SbiPr3 or PR3 has been prepared from the square-planar precursors trans-[RhCl(=CRR')(L)2] and NaC5H5 in excellent yields. Reaction of the triisopropylsibane derivative 2a. which contains a rather labile Rh-Sb bond, with CO, PMe3, and CNR (R = Me, CH2Ph, tBu) leads to the displacement of the SbiPr3 ligand and affords the substitution products [(eta5-C5H5)Rh(=CPh2)(L)] (3-7). In contrast, treatment of the triisopropylphosphane compound 2c with CO and CNtBu leads to the cleavage of the Rh=CPh2 bond and gives besides [(eta5-C5H5)Rh(PiPr3)(L)] (10, 12) by metal-assisted C-C coupling diphenylketene Ph2C=C=O (11) or the corresponding imine Ph2C=C=NtBu (13). While the reaction of 2a, c with C2H4 yields [(eta5-C5H5)Rh(C2H4)(L)] (14, 15) and the trisubstituted olefin Ph2C=CHCH3 (16), treatment of 2a, c with RN3 leads to the cleavage of both the Rh-EiPr3 and Rh=CPh2 bonds and gives the chelate complexes [(eta5-C5H5)Rh(kappa2-RNNNNR)] (19, 20). The substitution products 3 (L=CO) and 4 (L= PMe3) react with an equimolar amount of sulfur or selenium by addition of the chalcogen to the Rh=CPh2 bond to generate the complexes [(eta5-C5H5)Rh(kappa2-ECPh2)(L)] (21-24) with thio- or selenobenzophenone as ligand. Similarly, treatment of 3 with CuCl affords the unusual 1:2 adduct [(eta5-C5H5)(CO)Rh(mu-CPh2)(CuCl)2] (25), which reacts with NaC5H5 to form [(eta5-C5H5)(CO)Rh(muCPh2)Cu(eta5-C5H5)] (26). The molecular structures of 3 and 22 have been determined by X-ray crystallography. 相似文献