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951.
Govor EV Lysenko AB Quiñonero D Rusanov EB Chernega AN Moellmer J Staudt R Krautscheid H Frontera A Domasevitch KV 《Chemical communications (Cambridge, England)》2011,47(6):1764-1766
Chloride-centered hexanuclear hydroxopyrazolate reveals potential as a receptor of halomethane and halometallate species and as a molecular building block for coordination polymers. 相似文献
952.
A quartz crystal microbalance study of the adsorption of asphaltenes and resins onto a hydrophilic surface 总被引:2,自引:0,他引:2
Ekholm P Blomberg E Claesson P Auflem IH Sjöblom J Kornfeldt A 《Journal of colloid and interface science》2002,247(2):342-350
The adsorption of extracted and purified samples of asphaltenes and resins onto gold surfaces has been studied as a function of bulk concentration using a quartz crystal microbalance with dissipation measurements (QCM-D). With this device, which works equally well in transparent, opaque, and nontransparent samples, the adsorbed amount is measured through a change in resonant frequency of the quartz oscillator. The measured change in dissipation reports on changes in layer viscoelasticity and slip of the solvent at the surface. The results show that the adsorbed amount for resins from heptane corresponds to a rigidly attached monolayer. The adsorbed amount decreases with increasing amount of toluene in the solvent and is virtually zero in pure toluene. Asphaltenes, on the other hand, adsorb in large quantities and the mass and dissipation data demonstrate the presence of aggregates on the surface. The aggregates are firmly attached and cannot be removed by addition of resins. On the other hand, resins and asphaltenes associate in bulk liquid and the adsorption from mixtures containing both resins and asphaltenes is markedly different from that obtained from the pure components. Hence, we conclude that preformed resin aggregates adsorb to the surface. These results are compared and discussed in relation to adsorption from crude oil diluted in heptane/toluene mixtures. 相似文献
953.
Jialei Ye Junxian Yun Dong‐Qiang Lin Linhong Xu Harald Kirsebom Shaochuan Shen Gensheng Yang Kejian Yao Yi‐Xin Guan Shan‐Jing Yao 《Journal of separation science》2013,36(24):3813-3820
A novel super‐macroporous monolithic composite cryogel was prepared by embedding macroporous cellulose beads into poly(hydroxyethyl methacrylate) cryogel. The cellulose beads were fabricated by using a microchannel liquid‐flow focusing and cryopolymerization method, while the composite cryogel was prepared by cryogenic radical polymerization of the hydroxyethyl methacrylate monomer with poly(ethylene glycol) diacrylate as cross‐linker together with the cellulose beads. After graft polymerization with (vinylbenzyl)trimethylammonium chloride, the composite cryogel was applied to separate immunoglobulin‐G and albumin from human serum. Immunoglobulin‐G with a mean purity of 83.2% and albumin with a purity of 98% were obtained, indicating the composite cryogel as a promising chromatographic medium in bioseparation for the isolation of important bioactive proteins like immunoglobulins and albumins. 相似文献
954.
Andrew M. Kelly Verena Kaltenhauser Inge Mühlbacher Karl Rametsteiner Harald Kren Christian Slugovc Franz Stelzer Frank Wiesbrock 《Macromolecular bioscience》2013,13(1):116-125
A set of poly(2‐oxazoline)‐derived (co‐)polymers was prepared by microwave‐assisted polymerizations and acid‐mediated hydrolysis and tested for antimicrobial activity in 50 × 50 × 2 mm PP compound plates containing 5 wt% of the polymers. Antimicrobial activity against gram‐negative E. coli and P. aeruginosa as well as C. albicans depended only on the degree of hydrolysis, while antimicrobial activity against gram‐positive S. aureus was only observed for hydrolyzed poly(2‐nonyl‐2‐oxazoline)s. The surface energies of the compound plates compared to pure PP were hardly altered, and the compounds can be considered as alternatives for PP. The presence of the biocide additives at the surface of the PP compound plates could be shown by combined ATR‐IR, zeta potential, and SEM‐EDX measurements. Antimicrobial activity was maintained during double incubation as well as for lowered amounts of the biocide additive of 1% in PP compound plates.
955.
Bacteriophage T4 lysozyme and chicken egg white lysozyme were covalently bound to cyanogen bromide activated Sepharose and to glutaraldehyde activated polyacrylhydrazido-Sepharose. The latter method seemed less favorable for T4 lysozyme, since the poly-acrylhydrazido-agarose conjugate exhibited low activity compared to the agarose conjugate. Whole bacteria (M.luteus and chloroform-treatedE. coli B cells) and the soluble uncross-linked peptidoglycan polymer fromM. luteus were used as substrates. Both types of conjugates exhibited low specific activity (lytic activity) toward insoluble substrates (cells), but surprisingly high specific activity toward the soluble substrate (hydrolytic activity). Product analysis showed that the enzyme conjugates retained their specificity of action, i.e., the same products were formed, and their rates of production were the same as those observed with the soluble (native) enzyme. The cell wall disaccharide-tetrapeptide GlcNAc-MurNAc-L-ala-D-gIu-(A2pm-D-Ala) (C6) inhibits the hydrolytic activity of both the native and the agarose bound T4 lysozyme. Only a slightly increased thermal stability was observed upon immobilization of T4 lysozyme, whereas the stability of the enzyme during storage and handling was greatly improved. The pH optimum of the lytic activity of Sepharose-T4 lysozyme was shifted about 1 pH unit to the alkaline side, compared to that found for the soluble enzyme, whereas no pH shift was observed for the polyacrylhydrazido-Sepharose conjugate. The optimum of the hydrolytic activity of Sepharose-T4 lysozyme was shifted to the acidic side. The pH optima of the lytic activity of the various lysozymes toward the bacterial cells were all very similar (>7), and differed greatly from the pH optima (<6) observed for their hydrolytic activities toward the negatively charged soluble peptidoglycan polymer. It is proposed that the observed differences in pH optima primarily reflect the basically different properties measured, i.e., the β(1–4) cleaving activity (hydrolytic activity), and dissolution process of the damaged cells (lytic activity). 相似文献
956.
The investigation of multicomponent mixtures by spectrophotometry is described. A desk computer, APPLE II, is used to calculate the number of absorbing species in a series of measured spectra by matrix rank analysis. Representation of the observed spectra as linear combinations of eigenvectors leads to significant reduction of the data set, so that a nonlinear least-squares fit based on the Newton—Gauss—Marquardt algorithm is possible on a small computer. As an example, the complexation of copper(II) with 1,4,7-triazaheptane (dien) was studied by combined spectrophotometric and pH titration. The spectra of 62 mixtures at 26 wavelengths were analysed; the number of absorbing species, their spectra and the underlying equilibrium constants were determined. Representation of kinetic curves as linear combinations of eigenvectors is described. It is shown that instead of finding the minimum of the square sum in a multidimensional rate constant space, these minima can be found in a one-dimensional space. Two examples are given: the first is theoretical whereas the second is based on the kinetics of dissociation of the μ-peroxo complexes formed between cobalt(II), oxygen and 4,7,10-triazatridecanedioic acid in acidic solution. 相似文献
957.
Trapp N Scherer H Hayes SA Berger RJ Kütt A Mitzel NW Saame J Krossing I 《Physical chemistry chemical physics : PCCP》2011,13(13):6184-6191
The syntheses of the perfluorinated alcohols (F(5)C(6))(F(3)C)(2)COH (1) and (F(5)C(6))(C(5)F(10))COH (2) are described. Both compounds were prepared in reasonable yields (1: 65%, 2: 85%) by reacting the corresponding ketone with C(6)F(5)MgBr, followed by acidic work-up. The alcohols were characterized by NMR, vibrational spectroscopy, single-crystal X-ray diffraction, acidity measurements and gas-phase electron diffraction. A combination of appropriate 2D NMR experiments allowed the unambiguous assignment of all signals in the (19)F spin systems, of which that of 2 was especially complex. High acidity of the alcohols is indicated by acidity measurements as well as the calculated gas phase acidities. It is also supported by the crystal structure of 2, which exhibits only a single weak intermolecular hydrogen bridge with an O...O distance of 301 pm. This shows the low donor strength of the oxygen atom in the compound, which is partly compensated through formation of two intramolecular CF...H contacts of 220 and 232 pm length to the proton not involved in the hydrogen bridge. The pK(a) values in acetonitrile are 22.2 for 1 and 22.0 for 2; their calculated gas phase acidities are 1367 and 1343 kJ mol(-1) (MP2/TZVPP level). 相似文献
958.
959.
Samples of a poly(ethylene oxide) trisiloxane surfactant, water, and decane have been investigated using pulsed field gradient
NMR (PGSE NMR) and small-angle neutron scattering (SANS) to determine the solution structure. The surfactant/water weight
ratio has been kept constant at a value of 3/2, with variation of the oil (decane) content. In the neutron scattering measurements
the temperature was varied from 23 °C up to the phase separation limit for these systems. The combined NMR and SANS data show
that on addition of decane, the system exists as a hexagonal phase of cylindrical decane-containing micelles at all temperatures
investigated. The addition of decane changes significantly the values for the structure parameters in the system, inducing
an increase in periodicity of 12–15 ?. By substitution of decane with its deuterated equivalent, decane-d22, it was possible to obtain detailed information on the structural organization of the oil component in this ternary mixture. 相似文献
960.