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961.
H. Frunder D. Illig H. Finsterhölzl H.W. Schrōtter B. Lavorel G. Roussel J.C. Hilico J.P. Champion G. Pierre G. Poussigue E. Pascaud 《Chemical physics letters》1983,100(1):110-114
The CARS spectrum of the v1 band of 12CH4 at a pressure of 14 mbar was recorded using cw excitation in the cavity of a ring argon ion laser. The analysis of the intensity profile of the obarred spectrum led to the detection of inconsistencies with the hitherto proposed calculated positions of transitions with J = 7 to J = 10 and to a relocation of the corresponding lines. 相似文献
962.
H. G. Gassen und W. Leifer 《Fresenius' Journal of Analytical Chemistry》1970,252(4-5):337-343
Zusammenfassung Die Anwendung eines Analysators in der Nucleinsäurechemie wird beschrieben. Die Substanzen werden ohne Gradienten an einer Kationenaustauschersäule getrennt und im Durchfluß spektralphotometrisch bei 2 Wellenlängen identifiziert und quantitativ bestimmt. Die Erfassungsgrenze liegt bei 50 pMol Nucleosid. Die Methodik wird anhand der Analyse von chemisch modifizierten Oligo- und Polynucleotiden diskutiert.
Wir danken Herrn Lüllemann für die Konstruktion der mechanischen Teile und Frau Roswitha Nolte für die Durchführung der Analysen und die ausgezeichnete Betreuung des Gerätes.
Die Arbeit wurde von der Deutschen Forschungsgemeinschaft unterstützt. 相似文献
On an analyser in nucleic acid chemistry
The use of an analyser in nucleic chemistry is discussed. The substances are separated on a cation-exchange column with a single solvent. They are identified and measured quantitatively at two wavelengths by means of a continuous ultraviolet absorbance monitoring device. The minimum amount to be determined is 50 pMoles nucleoside. The method is demonstrated with the analysis of chemically modified oligo- and polynucleotides.
Wir danken Herrn Lüllemann für die Konstruktion der mechanischen Teile und Frau Roswitha Nolte für die Durchführung der Analysen und die ausgezeichnete Betreuung des Gerätes.
Die Arbeit wurde von der Deutschen Forschungsgemeinschaft unterstützt. 相似文献
963.
Summary A set of algorithms designed to enhance the display of protein binding cavities is presented. These algorithms, collectively entitled CAVITY SEARCH, allow the user to isolate and fully define the extent of a particular cavity. Solid modeling techniques are employed to produce a detailed cast of the active site region, which can then be color-coded to show electrostatic and steric interactions between the protein cavity and a bound ligand. 相似文献
964.
Single vibronic lifetimes of two-photon excited states are measured in the low pressure limit for naphthalene. The two-photon spectrum, besides yielding new states in S1, is also free of the interference from the neighborhood of the S2, known from one-photon experiments, and hence unperturbed lifetimes can be measured to higher excess energies. The overall pattern of lifetimes with excess energy including both one-photon and two-photon states shows that the vibronic structure is subordinate to an overall monotonic decrease, much as found earlier for β-naphthylamine. This indicates, at least for naphthalene, that radiationless processes into triplets are dominated by Franck—Condon factors and not by vibronic inductions and promoting modes. 相似文献
965.
A copper microparticle-modified carbon fiber microdisk array electrode was fabricated and employed in capillary electrophoresis for the simultaneous determination of the five aminoglycoside antibiotics (AGs) including netilmicin, tobramycin, lincomycin, kanamycin and amikacin. The array electrode exhibited high catalytic activity for AGs, good reproducibility and stability. Under the optimum separation conditions (separation voltage of 6.2 kV, electrophoretic medium of 125 mM NaOH), the five AGs above were baseline separated within 20 min. At a working electrode potential of 0.7 V (versus saturated calomel electrode), the calibration curves were linear over two orders of magnitude of concentration, and the detection limits (SIN=3) were below 2 microM except for lincomycin (6.7 microM). The developed method was successfully employed for the simultaneous determination of the five AGs studied in pharmaceutical injections. The feasibility of this method for the simultaneous determination of lincomycin, kanamycin and amikacin in urine sample was also demonstrated. 相似文献
966.
Separation of enantiomers: needs, challenges, perspectives 总被引:15,自引:0,他引:15
Chiral drugs, agrochemicals, food additives and fragrances represent classes of compounds with high economic and scientific potential. First the present implications of their chiral nature and necessity of separating enantiomers are summarised in this article. In the following a brief overview of the actual approaches to perform enantioseparations at analytical and preparative scale is given. Challenging aspects of these strategies, such as problems associated with data management, choice of suitable chiral selectors for given enantioseparations and enhanced understanding of the underlying chiral recognition principles, are discussed. Alternatives capable of meeting the requirements of industrial processes, in terms of productivity, cost-effectiveness and environmental issues (e.g., enantioselective membranes) are critically reviewed. The impact of combinatorial methodologies on faster and more effective development and optimisation of novel chiral selectors is outlined. Finally, the merits and limitations of most recent trends in discrimination of enantiomers, including advances in the fields of sensors, microanalysis systems, chiroptical methods and chemical force microscopy are evaluated. 相似文献
967.
968.
The N,N-diisopropylaminomethyl aluminium compound [tBu2AlCH2NiPr2 x LiCl]2(1) and the gallium compounds Li[tBu2Ga(CH2NiPr2)2](2) and [tBu2GaCH2N(H)iPr2]Cl x tBu3Ga (3) were prepared by transmetallation of N,N-diisopropylaminomethyllithium LiCH2NiPr2 with di-tert-butylaluminium or -gallium chloride, and characterised by elemental analyses, multinuclear NMR spectroscopy (1H, 13C, 27Al, 7Li) and IR spectroscopy. The crystal structures have been determined by single crystal X-ray diffraction. Compound aggregates as a centrosymmetric dimer, with two Al-C-N units connected by a frame of two LiCl molecules [Al-Cl 2.367(1), Cl-Li 2.339(4) and 2.374(4), Li-N 1.977(4)A]. Compound 2 is a lithium organogallate with two weak LiN bonds [1.965(7) and 1.937(7)A]. Compound 3 contains two different moieties: tBu3Ga and a [tBu2GaCH2N(H)iPr2]+ cation, which are bridged by a Cl- anion [Ga-Cl 2.445(1) and 2.579(1), HCl 2.362(3)A]. 相似文献
969.
Virve A. Karttunen Mikko Linnolahti Tapani A. Pakkanen Janne Maaranen Päivi Pitkänen 《Theoretical chemistry accounts》2007,118(5-6):899-913
The performance of quantum chemical methods for geometry prediction of hafnocenes was evaluated. HF, B3LYP and MP2 in combination
with nonrelativistic (MHF) and relativistic (MWB and LANL2DZ) basis sets for hafnium together with standard basis sets 3-21G*,
6-31G* and 6-311G** for other elements were applied. Five basic structural parameters of the optimized structures of the hafnocenes
were compared with experimental crystal structures obtained from the Cambridge structural database. Altogether 80 hafnocenes
were included in the analysis. The results show that relativistic corrections are necessary for Hf atom. However, even the
Hartree–Fock (HF) method, when combined with relativistic pseudopotentials, reproduces the experimental crystal structures
with significant accuracy. The good performance of the HF method can be understood to originate from the absence of significant
near-degeneracy correlations for hafnium. On average, the B3LYP and MP2 methods provide structural parameters somewhat closer
to the experimental ones. 相似文献
970.
Catalyst Design for Methacrolein Oxidation to Methacrylic Acid 总被引:5,自引:0,他引:5
Heteropoly compounds (HPCs) with the general formula CsMHPVMo11O40are prepared and tested as catalysts. The influence of elements entering the formula on the catalyst properties is studied: Cs defines the acidity and specific area, V controls the selectivity, and the transition metal M defines the mobility of oxygen in the bulk and the catalyst activity. The mechanism of methacrolein oxidation over HPCs is investigated. Using the response method and mass spectrometry of the reaction mixture, it is shown that only the catalyst oxygen atoms take part in the formation of methacrylic acid and that the transport of active oxygen to adsorbed methacrolein plays a key role in the oxidation process. A correlation between the HPC activity and the redox ability of the metal cation M
n+ M
n+ i
(i= 1 or 2) is found. New catalysts for methacrolein oxidation to methacrylic acid are developed on the basis of this correlation. These are the salts of PVMo-poly acid with Cs, Cu, and the transition metal M as cations. These catalysts are more active (a conversion of up to 91%) and selective (up to 98%) compared to conventional catalysts for methacrolein oxidation to methacrylic acid. 相似文献