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971.
Protein structure and dynamics can be characterized on the atomistic level with both nuclear magnetic resonance (NMR) experiments and molecular dynamics (MD) simulations. Here, we quantify the ability of the recently presented CHARMM36 (C36) force field (FF) to reproduce various NMR observables using MD simulations. The studied NMR properties include backbone scalar couplings across hydrogen bonds, residual dipolar couplings (RDCs) and relaxation order parameter, as well as scalar couplings, RDCs, and order parameters for side‐chain amino‐ and methyl‐containing groups. It is shown that the C36 FF leads to better correlation with experimental data compared to the CHARMM22/CMAP FF and suggest using C36 in protein simulations. Although both CHARMM FFs contains the same nonbond parameters, our results show how the changes in the internal parameters associated with the peptide backbone via CMAP and the χ1 and χ2 dihedral parameters leads to improved treatment of the analyzed nonbond interactions. This highlights the importance of proper treatment of the internal covalent components in modeling nonbond interactions with molecular mechanics FFs. © 2013 Wiley Periodicals, Inc. 相似文献
972.
Based on the theory and application developments of polymer flooding on enhancing oil recovery, an improved mathematical model has been developed to simulate the mechanism of viscous-elastic polymer flooding. IMPES method has been presented to solve the polymer flooding model considering the viscosifying effect of elasticity, the effect of decreasing residual oil and the degradation of polymer molecules. The validation of the model is approved by an experiment. A simulation example was carried out using the developed numerical simulator. The enhanced oil recovery mechanism was discussed for viscous-elastic polymer flooding, and corresponding influencing factors were also studied. 相似文献
973.
Dong‐Jun Yu Jun Hu Yan Huang Hong‐Bin Shen Yong Qi Zhen‐Min Tang Jing‐Yu Yang 《Journal of computational chemistry》2013,34(11):974-985
Understanding the interactions between proteins and ligands is critical for protein function annotations and drug discovery. We report a new sequence‐based template‐free predictor (TargetATPsite) to identify the Adenosine‐5′‐triphosphate (ATP) binding sites with machine‐learning approaches. Two steps are implemented in TargetATPsite: binding residues and pockets predictions, respectively. To predict the binding residues, a novel image sparse representation technique is proposed to encode residue evolution information treated as the input features. An ensemble classifier constructed based on support vector machines (SVM) from multiple random under‐samplings is used as the prediction model, which is effective for dealing with imbalance phenomenon between the positive and negative training samples. Compared with the existing ATP‐specific sequence‐based predictors, TargetATPsite is featured by the second step of possessing the capability of further identifying the binding pockets from the predicted binding residues through a spatial clustering algorithm. Experimental results on three benchmark datasets demonstrate the efficacy of TargetATPsite. © 2013 Wiley Periodicals, Inc. 相似文献
974.
Chi Fang Ting Xiong Jie Hou Jing Wei Gu Mei Hu Sheng 《Journal of Dispersion Science and Technology》2013,34(4):604-610
Amidoxime (AO)/amine co-functionalized polypropylene fiber adsorbents were prepared. The all-polymeric structures were characterized by using Fourier transform infrared spectroscopy (FTIR), optical microscope, contact angle meter and electron spin resonance (ESR) analysis methods, confirming the grafting, modification, and amidoximation stages gravimetrically, spectroscopically, and visually. The properties for the removal of uranyl(VI) from aqueous solutions were investigated. For amidoxime (AO) fiber, high adsorption rate was observed within the first 30 minutes and the plateau value of 40.6% uranium loading (0.0812 mg/g) was reached at around 30 minutes. The adsorption equilibrium for AO/amine fiber was attained within 20 minutes, resulting in the adsorption of 92.6% uranium loading (0.185 mg/g). The percentage of adsorption increases with increasing pH value (2–6), reaches a maximum at pH 6.0 and then remains almost constant for AO/amine fiber, whereas reduces slightly for AO fiber. 相似文献
975.
Song Wang Liqiang Tan Jinlong Jiang Jing Chen Liangdong Feng 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(2):1305-1312
In this research TiO2 sample was synthesized by a simple sol–gel method and was characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) techniques. The XRD result indicated that the obtained product was anatase titanium dioxide with high purity, the TEM image clearly showed that the particle sizes of TiO2 nanoparticles were in the range of 30–70 nm, and the measured BET surface area of the heated TiO2 nanoparticles was 147.14 m2/g. In this work, the prepared TiO2 sample was used as a new adsorbent for the adsorption of radionuclide Co(II) ions from aqueous solutions, and the influence of pH, contact time, ionic strength and temperature in the presence or absence of humic acid/fulvic acid (HA/FA) were also investigated. The experimental results indicated that the adsorption of Co(II) ions onto TiO2 was strongly pH-dependent. Based on the surface complexation, the presence of HSs enhanced the adsorption of Co(II) ions and the influence of Co(II) adsorption onto FA–TiO2 hybrids was much stronger than that of HA–TiO2 at pH values of 2.0–9.0. Adsorption of Co(II) ions onto TiO2 powder was strongly dependent on ionic strength. The adsorption process mainly occured in the first contact time of 2 h and could be fitted by a pseudo-second-order rate model. The calculated thermodynamic data indicated that the adsorption of Co(II) ions onto TiO2 was a spontaneous process and favorable at high temperatures. 相似文献
976.
Zhiyun Chen Zilin Yang Xianlong Du Jihua Zhao 《Journal of Dispersion Science and Technology》2013,34(12):1756-1761
The kinetics for the reaction between potassium ferricyanide (K3Fe(CN)6) and cobalt chloride (CoCl2) in aqueous solution and water/bis(2-ethylhexyl) sodium sulfosuccianate (AOT)/isooctane microemulsions were studied by three-wavelength spectrophotometry at 298.2 K. The second-order rate constants (k2) were calculated from the time dependence of the concentration of reactant K3Fe(CN)6. The result showed that the reaction rates in water/AOT/isooctane microemulsions were slower than that in the aqueous solution, and k2 decreased with molar ratio (ω) of water to AOT in microemulsions, which was interpreted by the transition state theory and confirmed that the reaction took place at the interfaces of the microemulsion water pools. 相似文献
977.
Jing Zhang Weisheng Yu Rong Zhang Haiyang Yang 《Journal of Dispersion Science and Technology》2013,34(9):1290-1296
We have studied the interactions between anionic carboxymethyl guar (CMG) and oppositely charged surfactant: dodecyltrimethylammonium bromide (DTAB), tetradecyltrimethylammonium bromide (TTAB), cetyltrimethylammonium bromide (CTAB), and gemini surfactants (16-4-16), using rheological measurements. In the present study, two competing forces, electrostatic interaction and hydrophobic interaction, have been identified as important factors. Various types of structure formed on the anionic CMG chains are qualitatively discussed in comparison. For example, C12TAB and gemini surfactant tend to form polymer-bound aggregates, whereas the C16TAB tend to form the polymer-associated architecture. Furthermore, possible mechanisms based on the experimental results to elucidate these interesting phenomena have been proposed and discussed. 相似文献
978.
Jingtao Dai Ying Wang Yukou Du Guoqing Di 《Journal of Dispersion Science and Technology》2013,34(2):205-208
Bimagnetic Pt3Co/Fe3O4 nanocomposite is synthesized in aqueous solution. The nanoparticles are characterized with TEM, FTIR, and magnetic measurements. The as‐synthesized nanocomposite exhibits ferromagnetic properties at room temperature due to the exchange coupling between Pt3Co and Fe3O4. Magnetic properties of Pt3Co/Fe3O4 nanoparticle can be tuned by varying of the molar ratio of iron to platinum. Pt3Co/Fe3O4 nanoparticles exhibit higher saturation magnetization when the molar ratio of iron to platinum is 1. 相似文献
979.
Tianqing Liu Yinyin Gan Lilia Song Jing Qiu Liuhua Chen 《Journal of Dispersion Science and Technology》2013,34(10):1370-1375
Vesicles have been prepared at a constant molar ratio of L-glutamic acid/1-aminodecane/ibuprofen/H2O. The fusion dynamics of the vesicles have been directly observed and followed by using optical microscopy and freeze fracture replication-electron microscopy technologies. With time increasing up to 25 minutes, the vesicles slowly fuse to form large stable vesicles. A membrane phase transition temperature is detected at 97°C. 相似文献
980.
Jinchuan Xie Jiachun Lu Xiaohua Zhou Xuhui Wang Mei Li Lili Du Yueheng Liu Guoqing Zhou 《Journal of Radioanalytical and Nuclear Chemistry》2013,296(3):1169-1177
Sorption (distribution) coefficients of plutonium were most often derived by static batch experiments. However, it is not clear how unsaturated flow conditions including moisture content and pore water velocity change the sorption coefficients. Transport experiments of plutonium through the unsaturated sediments packed into the columns were then performed in order to determine the sorption coefficients (column-K ds). Static batch experiments were also conducted to obtain batch-K ds and then compare the differences between batch-K ds and column-K ds. The results show that unsaturated flow conditions had no significant effect on column-K ds, and the average column-K d value was 1.74 ± 0.02 m3/kg. By comparison, batch-K d values spanned several orders of magnitude, regardless of the specified liquid–solid conditions. Moreover, the batch-K d (22.7 m3/kg) at the standard L/S (4 mL/g) recommended by ASTM D 4319 was over an order of magnitude larger than the average column-K d. 相似文献