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991.
A novel heterogeneous strong acid catalyst was synthesized through the copolymerization of p-toluenesulfonic acid and paraformaldehyde and utilized for the synthesis of fructone. The results showed that the catalyst was very efficient for the reaction with the yield over 95%. The advantages of extremely high density of acidity, high thermal and chemical stability, low cost for the simple synthetic procedure, and reusability made the catalyst one of the best choices for the reaction. 相似文献
992.
Metal-organic complex (H3NCH2CH2NH2)3[MoO2(OC6H4O)2] with a lamellar morphology has been syn- thesized. Its crystal structure was confirmed by single-crystal X-ray diffraction. The morphology of the crystal was observed by scanning electron microscopy (SEM). The metal-organic nanoparticles have been prepared by using an ultrasonic method. The morphology of the as-prepared nanoparticles was observed by transmission electron microscopy (TEM). The possible formation mechanism has also been proposed. 相似文献
993.
Compared with the traditional thin film techniques, the matrix-assisted pulsed laser evaporation (MAPLE) technique has many advantages in the deposition of polymer and organic thin films. It has a wide range of applications in many fields, such as non-linear optics, luminescent devices, electronics, various sensors. We have successfully deposited polyimide thin films by using the MAPLE technique. These films were characterized with XPS. The XPS spectra showed that the single-photon effect is ob-vious at low laser fluence and the chemical bonds will be broken, resulting in decomposition of the films. Contrarily, the single-photon effect will decrease and the multi-photon effect and the photothermal effect will increase at high laser fluence, resulting in the protection of the structure of the polyimide thin films and the obvious decrease in decomposition. High laser fluence is more suitable for the deposition of polymer and organic thin films than low laser fluence. 相似文献
994.
The effect of substrate concentration on biohydrogen production by using kinetic models 总被引:5,自引:0,他引:5
The effect of substrate concentration ranging from 0 to 300 g/L on fermentative hydrogen production by mixed cultures was investigated in batch tests using glucose as substrate. The experimental results showed that, at 35℃ and initial pH 7.0, during the fermentative hydrogen production, the hydrogen production potential and hydrogen production rate increased with increasing substrate concentration from 0 to 25 g/L. The maximal hydrogen production potential of 426.8 mL and maximal hydrogen pro-duction rate of 15.1 mL/h were obtained at the substrate concentration of 25 g/L. The maximal hydrogen yield and the maximal substrate degradation efficiency were respectively 384.3 mL/g glucose and 97.6%, at the substrate concentration of 2 g/L. The modified Logistic model could be used to describe the progress of cumulative hydrogen production in this study successfully. The Han-Levenspiel model could be used to describe the effect of substrate concentration on fermentative hydrogen production rate. 相似文献
995.
The importance of anharmonic effect in dissociation of molecular systems especially clusters has been noted. In this paper, we shall study the effect of coupled anharmonic oscillator of the standard bilinear form (SBF) Morse oscillator (MO) potential on unimolecular reaction. We shall use the systematic theoretical approach, YL method, proposed by Yao and Lin (YAO L, et. al. J Phys Chem A, 2007, 111(29): 6722-6729), which can evaluate anharmonic effects on the rate constants based on the transition state theory. In treating the anharmonic effect with the Morse oscillator potential on unimolecular reactions under collision-free conditions by using the RRKM (Rice-Ramsperger-Kassel-Marcus) theory, the in-verse Laplace transformation of the partition functions was used to obtain the total amount of state and density of state by using the first-order and the second-order approximations of the saddle-point method. To demonstrate the anharmonic effect of the SBF Morse model, we choose some model systems and a real reaction as examples. 相似文献
996.
A novel amperometric sensor for uric acid based on ordered mesoporous carbon modified pyrolytic graphite electrode was developed.
Uric acid oxidation was easily catalyzed by this electrode in a phosphate buffer solution at pH 7.0, with an anodic potential
decrease about 140 mV compared to bare pyrolytic graphite electrode. The uric acid level was determined by the amperometric
method, at a constant potential of 0.31 mV, the catalytic current of uric acid vs. its concentration showed a good linearity
in the range of 1.0 × 10−6−1.0 × 10−4 mol L−1, with a correlation coefficient of 0.999. The detection limit was 4.0 × 10−7 mol L−1. The proposed method could be effectively used for uric acid amperometric sensing in human urine. 相似文献
997.
Iisa Outola Kenneth Inn Robert Ford Steve Markham Petri Outola 《Journal of Radioanalytical and Nuclear Chemistry》2009,282(2):321-327
The environmental mobility/availability behavior of radionuclides in soils and sediments depends on their speciation. Experiments
have been carried out to develop a simple but robust radionuclide sequential extraction method for identification of radionuclide
partitioning in sediments and soils. The sequential extraction protocol was optimized for temperature, concentration of reagents
and reaction time. Optimum extraction conditions were chosen based on the release of 239,240Pu, 238U and stable elements. Results from the experiments with lake sediment (SRM 4354) are compared to the previous trials where
the sequential extraction protocol was optimized with the ocean sediment (SRM 4357). Based on these two trials the NIST standard
sequential extraction protocol is established for defined extraction settings for temperature, reagent concentration and time. 相似文献
998.
Song-hua Ye Sheng Chen Fan Zhang Wei Wang Qin Tian Jin-zhi Liu Fang Chen Jin-ku Bao 《Applied biochemistry and biotechnology》2009,158(3):615-630
Plant lectins have been reported as transgenic resistance factors against a variety of insect pests. Herein, homologous analysis
demonstrated that Zephyranthes grandiflora agglutinin (ZGA) exhibited high similarity with other monocot mannose-binding lectins (MBLs). Phylogenetic analysis revealed
that it had taxonomical relationships with insecticidal MBLs. Subsequently, a plasmid expression vector pBI121 containing
zga gene (pBIZGA) was constructed using the zga sequence, under the control of CaMV35S promoter and nos terminator. pBIZGA was then integrated into the genome of Nicotiana tabacum L. Polymerase chain reaction and Southern blot analysis demonstrated that this zga gene was integrated into the plant genome. Western blotting and agglutinating activity analysis also showed that transgenic
tobacco plants expressed different levels of ZGA. Carbohydrate inhibition analysis indicated that recombinant ZGA and the
native shared the same carbohydrate-binding specificity. Moreover, genetic analysis confirmed Mendelian segregation (3:1)
of the transgenic in T1 progenies. In planta bioassays on T0 plants and their progenies indicated that expressed ZGA had an
effect on reducing the survivability and fecundity of tobacco aphids (Myzus nicotianae). These findings demonstrate that the novel zga gene of ZGA can be expressed in crop plants susceptible to various sap-sucking insects. 相似文献
999.
Christof Schmitz Ahmed Mourran Helmut Keul Martin Möller Martina Keerl Walter Richtering 《Colloid and polymer science》2009,287(10):1183-1193
The effect of microstructure on the aggregation behaviour of symmetrical di- and triblock copolymers P(BMA)-b-P(MAA) and P(BMA)-b-P(BMA-co-MAA)-b-P(MAA) with a molecular weight of 40,000 g/mol was studied. The critical micelle concentration, hydrodynamic radius and morphology
of the micelles were determined by fluorescence spectroscopy, dynamic light scattering and scanning force microscopy (SFM).
Whereas no effect of the microstructure on the critical micelle concentration could be detected, the hydrodynamic radius decreased
from di- to triblock copolymer from 53 to 36 nm. The decrease of about 32% corresponds to the length of the random middle
block within the triblock copolymer so that the reduction in hydrodynamic radius was caused by a complete orientation of the
random middle block at the core corona interface. Finally, the SFM investigation showed that dehydration of micelles on a
substrate is accompanied by formation of a physisorbed monolayer with a thickness of 2 nm on which the micelles are deposited. 相似文献
1000.
Masakuni Tako Takeshi Teruya Yukihiro Tamaki Teruko Konishi 《Colloid and polymer science》2009,287(12):1445-1454
The 1H-nuclear magnetic resonance spectrum showed that the l-rhamnosyl residues of native gellan gum were coinvolved in both a small number of 4C1-pyranose conformations and a large number of 1C4-pyranose conformations, whereas for deacylated polymer, almost of the residues were involved in 4C1-pyranose conformation. The flow curves of native gellan gum showed plastic behavior above 0.2%. The elastic modulus stayed
at a constant value with increase in temperature up to 40 °C, then decreased rapidly. The elastic modulus increased with addition
of CaCl2 (6.8 mM) and stayed constant value with increase in temperature up to 65 °C, then decreased rapidly. The stronger elastic
modulus was observed in deacylated gellan gum with addition of CaCl2. The elastic modulus of native gellan gum showed larger value than that in aqueous solution in the presence of urea (4.0 M).
Intra- and intermolecular associations of native gellan gum molecules in the presence of Ca+2 were proposed. 相似文献