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61.
1,3-Propanediol (1,3-PD) has numerous applications from polymers to cosmetics, foods, lubricants, and medicines. Recently,
there are strong industrial interests in a new kind of polyester, polytrimethylene terephthalate, with 1,3-PD as a monomer.
This new polyester shows significant promise for use in carpeting and textiles. In this article we introduce a mild aerobic
fermentation process using a strain screened from Klebsiella pneumoniae ATCC 25955, which is insensitive to oxygen, to produce 1,3-PD. We also describe a two-step fermentation process starting
with glucose that was converted into glycerol with a glycerol-producing yeast, followed by K. pneumoniae that converts glycerol into 1,3-PD without intermediate isolation and purification of glycerol. 相似文献
62.
Peng Yang Xuan Wang Bo Li Yixuan Yang Jinfeng Yue Yanrui Suo Huarong Tong Gang He Xiaojie Lu Gong Chen 《Chemical science》2021,12(16):5804
A highly efficient and versatile method for construction of peptide macrocycles via palladium-catalyzed intramolecular S-arylation of alkyl and aryl thiols with aryl iodides under mild conditions is developed. The method exhibits a broad substrate scope for thiols, aryl iodides and amino acid units. Peptide macrocycles of a wide range of size and composition can be readily assembled in high yield from various easily accessible building blocks. This method has been successfully employed to prepare an 8-million-membered tetrameric cyclic peptide DNA-encoded library (DEL). Preliminary screening of the DEL library against protein p300 identified compounds with single digit micromolar inhibition activity.A highly efficient and versatile method for construction of peptide macrocycles via palladium-catalyzed intramolecular S-arylation of alkyl and aryl thiols with aryl iodides under mild conditions is developed. 相似文献
63.
64.
Wei-Cho Huang Cheng S. Gong George T. Tsao 《Applied biochemistry and biotechnology》2003,106(1-3):471-480
Pressure pulsation (PP) was investigated for its effects on oxygen transfer rate (OTR) measured by sulfite oxidation. By manipulating
airflow rate, 0.41–1.2 vvm, and a control valve in a 4-L bioreactor, the frequency of PP was varied at different gas pressures3–15
psig. A mathematical model of OTR was built and compared to experimental data. OTR was also examined at constant gas pressure,
4.5–15.0 psig. The results indicate a good agreement between measurement and model prediction. OTR above 9 psig during PP
showed significant enhancement at 25°C. This proves that PP not only affects the elevation of DO level, but also increases
the interfacial area and mass transfer coefficient. 相似文献
65.
Chen Chee-Shan Chan E. Wang S. L. Gong C. S. Chen L. F. 《Applied biochemistry and biotechnology》1994,(1):531-544
A self-aggregating strain ofSaccharomyces uvarum (U4) was used as a biocatalyst to carry out continuous ethanol fermentation in a tower fermentor equipped with a cell separator.
Cell aggregates (2–3 mm) formed a stable packed bed in the fermentor, and the cell separator retained yeast cells effectively.
Corn steep liquor was used as a nitrogen source for the fermentation of corn syrup and black strap molasses. An ethanol productivity
of 54 g/L/h was reached using corn syrup at a dilution rate of 0.7/h, and sugar concentration in the feed was 15% (w/v). For
molasses fermentation, an ethanol productivity of 22 g/L/h was obtained at a dilution rate of 0.7/h, and sugar concentration
in the feed was 12.5% (w/v). Ethanol yields obtained from tower fermentation are higher than those obtained from flask fermentation
(96% for corn syrup fermentation and 92% for molasses fermentation). No significant loss in fermentation activity was observed
after 3 mo of operation. 相似文献
66.
Five different pure density functional theory (DFT) and hybrid Hartree-Fock/DFT methods have been used to search for the molecular structures, thermochemistry, and electron affinities of the bromine hydrogen fluorides HBrF(n)/HBrF(n)(-) (n = 2, 4). The basis sets used in this work are of double-zeta plus polarization quality in conjunction with s- and p-type diffuse functions, labeled as DZP++. Structures with Br-F and Br-H normal bonds, that is, HBrF(2)/HBrF(2)(-) with C(2v) or C(s) symmetry and HBrF(4)/HBrF(4)(-) with C(4v) or C(s) symmetry, are genuine minima. However, unlike the original BrF(3) and BrF(5) molecules, the global minima for HBrF(n)/HBrF(n)(-) (n = 2, 4) species are predicted to be complexes, some of which contain hydrogen bonds. The demise of the hypervalent structures is due to the availability of favorable dissociation products involving HF, which has a much larger dissociation energy than F(2). Similar reasoning suggests that PF(4)H, SF(3)H, SF(5)H, ClF(2)H, ClF(4)H, AsF(4)H, SeF(3)H, and SeF(5)H will all be hydrogen bond structures incorporating diatomic HF. The most reasonable theoretical values of the adiabatic electron affinities (EA(ad)) are 3.69 (HBrF(2)) and 4.38 eV (HBrF(4)) with the BHLYP method. These electron affinities are comparable to those of the analogous molecules: Br(2)F(n), ClBrF(n), and BrF(n)(+1) systems. The first F-atom dissociation energies for the neutral global minima are 60 (HBrF(2)) and 49 kcal/mol (HBrF(4)) with the B3LYP method. The first H-atom dissociation energies for the same systems are 109 (HBrF(2)) and 116 kcal/mol (HBrF(4)). The large Br-H bond energies are not sufficient to render the hypervalent structures energetically tenable. The dissociation energies for the complexes to their fragments are relatively small. 相似文献
67.
Shao-Chen Yang Qihuang Gong Zongju Xia Y. H. Zou Y. Q. Wu D. Qiang Y. L. Sun Z. N. Gu 《Applied physics. B, Lasers and optics》1992,55(1):51-53
The nonlinear third-order optical susceptibility of C70 in a toluene solution is measured for the first time by the method of degenerate four-wave mixing using 10 ns laser pulses at 1.06 m. The third-order susceptibility X
in
(3)
is 5.6×10–12 esu for a C70 toluene solution at a concentration of 0.476 g/l. The correspondent magnitude of the hyperpolarizability 1111 of the C70 molecule is 1.2×10–30 esu which is in a good agreement with the prediction given by the model of a free electron in a spherical box. 相似文献
68.
69.
The Gemini surfactant 9B-4-9B containing sodium sulfonate as hydrophilic head group was synthesized based on nonylphenol and characterized by FTIR, 1H NMR spectroscopy and the surface tension measurement. The CMC and C20 of the 9B-4-9B were smaller than that of sodium dodecylbenzene sulfonate and sodium dodecylsulfate, respectively, indicating excellent efficiency of micelle formation and reduced surface tension. Conducting polyaniline salts were synthesized by chemical oxidative micellar polymerization of aniline in water firstly using Gemini surfactant 9B-4-9B as the micelle stabilizer and ammonium peroxydisulfate as the oxidant at 0 °C. The stable polyaniline dispersions have been obtained when the molar ratio of the 9B-4-9B to aniline was equal to or above 0.5 used in the polymerization system. The obtained granular polyaniline particles with the size of 1-2 μm were characterized by FTIR, UV-Vis, SEM, WAXD and conductivity measurement. 相似文献
70.
Electrostatic layer-by-layer assembled carbon nanotube multilayer film and its electrocatalytic activity for O2 reduction 总被引:1,自引:0,他引:1
Zhang M Yan Y Gong K Mao L Guo Z Chen Y 《Langmuir : the ACS journal of surfaces and colloids》2004,20(20):8781-8785
Multilayer films of shortened multiwalled carbon nanotubes (MWNTs) are homogeneously and stably assembled on glassy carbon electrodes with the layer-by-layer (LBL) method, based on electrostatic interaction of positively charged poly(diallyldimethylammonium chloride) and negatively charged and shortened MWNTs. The film assembly and electrochemical property as well as the electrocatalytic activity toward O2 reduction of the MWNT multilayer film are studied. Scanning electron microscopy, the quartz crystal microbalance technique, ultraviolet-visible-near-infrared spectroscopy, and cyclic voltammetry are used for characterization of film assembly. Experimental results revealed that film growth is uniform, almost with the same coverage of the MWNTs in each layer, and that the assembled MWNTs are mainly in the form of small bundles or single tubes on the electrodes. Electrochemical studies indicate that the LBL assembled MWNT films possess a remarkable electrocatalytic activity toward O2 reduction in alkaline media. This property, combined with the well-dispersed, porous and conductive features of the MWNT film illustrated with the LBL method, suggests the potential application of the MWNT film for constructing an efficient alkaline air electrode for energy conversions. 相似文献