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991.
运用自动电位滴定技术分别研究了在纳米α-Fe2O3,γ-Al2O3单一体系及其混合体系中矿物表面的酸碱性质。依据表面配位理论恒电容模式,计算了相应的表面酸碱配位常数。实验和计算结果表明,按照等表面积原则混合α-Fe2O3、γ-Al2O3纳米粒子得到混合体系,其表面化学反应并非是单一体系的简单叠加,而是存在着不同矿物表面间复杂的交互作用。其表面酸碱性质和吸附重金属离子的行为可以用单表面模型拟合,混合体系表面反应平衡模式和相应的酸碱反应平衡常数分别为:≡XOH+H+≡XOH2+lgK1=4.04≡XOH≡XO-+H+lgK2=-9.20根据重金属离子Cu2+、Pb2+、Zn2+在α-Fe2O3/γ-Al2O3混合体系表面的吸附行为,计算得出Cu2+、Pb2+、Zn2+在混合体系固体表面的配位反应平衡常数如下:≡XOH+M2+≡XOM++H+lgK=-2.50、-2.25、-3.75(M=Cu、Pb、Zn) 相似文献
992.
Oxidative coupling of methane in a dual-bed reactor comprising of particle/cordierite monolithic catalysts 下载免费PDF全文
A dual-bed reactor was constructed comprising of a 5%Na2WO4-2%Mn/SiO2 particle catalyst and a 4%Ce-5%Na2WO4-2%Mn/SiO2/cordierite monolithic catalyst. The reaction performance of the oxidative coupling of methane (OCM) over the dual-bed reactor system was evaluated. The effects of the bed height and operation mode, as well as the reaction parameters such as reaction temperature, CH4/O2 ratio and flowrate of feed gas, on the catalytic performance were investigated. The results indicated that the suggested dual-bed reactor exhibited a good performance for the OCM reaction when the feed gases firstly passed through the particle catalyst bed and then to the monolithic catalyst bed. A CH4 conversion of 38.2% and a C2H4 selectivity of 43.3% could be obtained using the dual-bed reactor with a particle catalyst bed height of 10 mm and a monolithic catalyst bed height of 50 mm. Both the CH4 conversion and C2H4 selectivity have increased by 2.5% and 12.8%, respectively, as compared with the 5%Na2WO4-2%Mn/SiO2 particle catalyst in a conventional single-bed reactor and by 12.9% and 23.0%, respectively, as compared with the 4%Ce-5%Na2WO4-2%Mn/SiO2/cordierite monolithic catalyst in a single-bed reactor. The catalytic performance of the OCM in the dual-bed reactor system has been improved remarkably. 相似文献
993.
994.
995.
Shen L Fu J Fu K Picart C Ji J 《Langmuir : the ACS journal of surfaces and colloids》2010,26(22):16634-16637
A humido-responsive free-standing film has been created using layer-by-layer assembly technique. Polyethylenimine (PEI) at high pH was assembled with poly(acrylic acid) (PAA) at low pH on a Teflon substrate to yield a micro-nanostructured surface that can be made superhydrophobic after being coated with a low surface energy compound. The resulting asymmetric free-standing film with one surface being superhydrophobic while the other is hydrophilic after detachment from the substrate can undergo reversible bending/unbending shape transitions when the environmental humidity is changed. The bending/unbending movement of the free-standing film can be ascribed to the different responses of these two surfaces to humidity. 相似文献
996.
Nan Hu Wen‐Xi Ji Yin‐Yin Tong Zi‐Chen Li Er‐Qiang Chen 《Journal of polymer science. Part A, Polymer chemistry》2010,48(20):4621-4626
The reversible addition‐fragmentation chain transfer (RAFT) polymerization of N‐vinylcarbazole (NVK) mediated by macromolecular xanthates was used to prepare three types of block copolymers containing poly(N‐vinylcarbazole) (PVK). Using a poly(ethylene glycol) monomethyl ether based xanthate ( PEG‐X ), the RAFT polymerization of NVK proceeded in a controlled way to afford a series of PEG‐b‐PVK with different PVK chain lengths. Successive RAFT polymerization of NVK and vinyl acetate (VAc) with a small molecule xanthate ( X1 ) as the chain transfer agent was tested to prepare PVK‐b‐PVAc. Though both monomers can be homopolymerized in a controlled manner with this xanthate, only by polymerizing NVK first could give well‐defined block copolymers. The xanthate groups in the end of PVK could be removed by radical‐induced reduction using tributylstannane, and PVK‐b‐PVA was obtained by further hydrolysis of PVK‐b‐PVAc under basic conditions. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献
997.
Xinsheng Xu Lixia Jia Lei Shi Xuehan Ji Zhifeng Cui 《Research on Chemical Intermediates》2010,36(3):269-275
Chemically induced dynamic electron polarization (CIDEP) is one of the important research fields of dynamic spin chemistry.
In the present work, with ethylene glycol, 1,2-propanol and their mixtures with different ratios in volume as solvents and
duroquinone as photosensitive molecule, the influence of solvent viscosity on the CIDEP of photolyzed duroquinone radicals
has been studied experimentally. In each solvent, duroquinone neutral radicals are observed. Duroquinone neutral radicals
are generated through hydrogen transfer reaction from hydrogen-donor solvent molecules to excited duroquinone triplet. The
CIDEP mechanism is mainly triplet mechanism. The CIDEP intensity of duroquinone neutral radicals decreases with the increase
in the solvent viscosity, and the variation was rapid in low-viscosity range and slow in high-viscosity range. 相似文献
998.
Ji-min Yang Jun Ji 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(7):1169-1173
The solubility of ternary system of lithium, magnesium and chloride and refractive indexes have been determined at 60 and
75°C, respectively. Using the experimental results, the phase diagrams of the ternary system were plotted. The single-salt
Pitzer parameters of LiCl and MgCl2 β(0), β(1) and C
ϕ were calculated by using the equations reported by Li Y-H and de Lima at different temperatures, respectively. On the basis
of Pitzer ion-interaction model and solubility product equation for mixed electrolytes, the mixing parameters θLi, Mg, ΨLi, Mg, Cl and equilibrium constant K
sp were evaluated in this system, which were not reported in literature. A complete phase diagram of the ternary system was
predicted at 60 and 75°C. The prediction of solubilities in ternary system was then demonstrated. The calculated solubilities
agreed well with the experimental values. 相似文献
999.
Vapor generation-inductively coupled plasma-optical emission spectrometry was used for the determination of sulfide in water samples preserved by the addition of a zinc acetate and sodium hydroxide solution. Hydrogen sulfide and acid-volatile sulfides were transformed, by acidification, to a gaseous phase in a vapor generator and subsequently detected by inductively coupled plasma optical emission spectrometry. Compounds interfering with iodometric titration and spectrophotometric determination were examined as potential chemical interferents. The proposed method provides results comparable to iodometric titration in the tested concentration range 0.06-22.0 mg L−1. Limit of detection for the determination of hydrogen sulfide by this method is 0.03 mg L−1. 相似文献
1000.
Xiaowen Ji 《Talanta》2010,82(4):1170-231
A novel strategy for the preparation of in-column adenosine deaminase (ADA) microreactor and rapid screening of enzyme inhibitors in natural extracts was demonstrated. In this approach, ADA was encapsulated in anionic polyelectrolyte alginate that was immobilized on the surface of fused-silica capillary via ionic binding technique with cationic polyelectrolyte polyethylenimine (PEI). On-line enzyme inhibition study was performed by capillary electrophoresis (CE). The substrate and product were baselined separated within 75 s. The enzyme activity was determined by the quantification of peak area of the product. Enzyme inhibition can be read out directly from the reduced peak area of the product in comparison with a reference electropherogram obtained in the absence of any inhibitor. The inhibition percentage was used to evaluate relative activity of ADA microreactor. A known ADA inhibitor, erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA) was employed as a model compound for the validation of the inhibitor screening method, and the screening of ADA inhibitor in 19 traditional Chinese herbal medicines was performed. 相似文献