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991.
992.
Chlorobenzene hydrodechlorination in liquid phase has been studied. Chlorine released during the reaction inhibits conversion in large metallic particles. It was found comparing the behavior of Pd/SiO2, Pd/Al2O3 and Pd/C catalysts that the support plays the role of a chlorine trap. The activity for Pt, Rh and Pd at similar dispersions corresponds to the chlorine adsorption affinity of the metals. 相似文献
993.
运用原位红外反射光谱研究了碱性介质中甘氨酸在Pt电极上的解离吸附和氧化反应行为,并利用纳米Pt膜电极的异常红外效应鉴定反应过程中生成的表面吸附物种.结果表明:甘氨酸在Pt电极上极易发生解离,生成强吸附于电极表面上的氰基负离子,该吸附物种在低于0V电位下能稳定存在,并抑制甘氨酸的进一步反应.当电位高于0.2V时,氰基负离子被氧化为氰酸根离子进入溶液,使甘氨酸发生氧化反应,生成氰酸盐和碳酸盐等产物. 相似文献
994.
A variety of spherical and structured activated charcoal supported Pt/Fe3O4 composites with an average particle size of ~100 nm have been synthesized by a self-assembly method using the difference of reduction potential between Pt (IV) and Fe (Ⅱ) precursors as driving force. The formed Fe3O4 nanoparticles (NPs) effectively prevent the aggregation of Pt nanocrystallites and promote the dispersion of Pt NPs on the surface of catalyst, which will be favorable for the exposure of Pt active sites for high-efficient adsorption and contact of substrate and hydrogen donor. The electron-enrichment state of Pt NPs donated by Fe3O4 nanocrystallites is corroborated by XPS measurement, which is responsible for promoting and activating the terminal C=O bond of adsorbed substrate via a vertical configuration. The experimental results show that the activated charcoal supported Pt/Fe3O4 catalyst exhibits 94.8% selectivity towards cinnamyl alcohol by the transfer hydrogenation of cinnamaldehyde with Pt loading of 2.46% under the optimum conditions of 120℃ for 6 h, and 2-propanol as a hydrogen donor. Additionally, the present study demonstrates that a high-efficient and recyclable catalyst can be rapidly separated from the mixture due to its natural magnetism upon the application of magnetic field. 相似文献
995.
996.
离子凝聚法制备负载流感疫苗的壳聚糖微球 总被引:2,自引:1,他引:1
采用三聚磷酸钠(TPP)作为离子交联剂, 应用离子凝聚法制备负载流感疫苗的壳聚糖微球. 筛选出壳聚糖起始质量分数为1%. TPP的浓度对壳聚糖微球的制备影响较大, 采用低浓度的TPP(200 μg/mL)制备的微球放置过夜均出现沉淀现象, 高浓度的TPP(800 μg/mL)在制备过程中出现絮状沉淀. 固化比影响微球的释放行为, 固化比为1∶1的微球爆炸式释放率达到90%, 固化比为1∶3的微球6 h后逐步释放, 12 h后释放率达到95%. 固化比为1∶5的微球6 h后没有明显的释放行为. 壳聚糖溶液的pH对微球的制备和释放没有显著的影响. 通过对负载流感疫苗的壳聚糖微球的制备条件和释放行为的研究结果表明, pH=5.6的壳聚糖溶液, 固化比为1∶3, TPP的质量浓度为400 μg/mL是较理想的流感疫苗壳聚糖微球的制备条件. 相似文献
997.
0.5%Pt-K/y-Al2O3 catalysts for the synthesis of 0-phenylphenol(OPP) from 0-cyclohexenyl-cyciohexanone (dimer) dehydrogenation were prepared by means of a two subsequent impregnation method.The effects of catalyst preparation parameters,such as K promoters,calcination,and reduction conditions,were investigated.The results showed that the addition of K2SO4 to Pt/y-Al2O3 catalyst notably promoted the selectivity of OPP,and its optimum content was found to be 6% in mass fraction.The higher activity was obtained when Pt/y-Al2O3 catalyst was calcined in nitrogen atmosphere at 400-500℃ and then reduced at the same temperature for 3 h in hydrogen atmosphere.The conversion of the dimer and the selectivity of OPP were always above 99% and 90%,respectively,over 0.5%Pt-6% K2SO4/γ-Al2O3 catalyst during the pilot scale test of 8000 h. 相似文献
998.
999.
Recent theoretical and experimental results pertinent to protein adsorption kinetics obtained for well-defined systems using direct experimental techniques are discussed. Attention is focused on albumins and fibrinogen, whose structure and physicochemical characteristic are well-known. It is confirmed that the experimental data obtained by AFM imaging, QCM, OWLS, XPS and electrokinetic techniques (streaming potential) are prone to a quantitative interpretation in terms of the coarse-grained and molecular dynamics modeling. This allows to derive reliable data concerning the mass transfer rates, hydration functions, maximum coverages and adsorption/desorption kinetic constants. These results confirm that the protein adsorption mechanism is governed by electrostatic interactions among heterogeneously distributed charges. The protein substrate interactions promote the molecule transfer through the surface layer, control the free energy and in consequence the residence time of the molecule on substrate surfaces. On the other hand, the interactions among adsorbed molecules control the maximum coverage and the formation of bilayer structures. As a result of this complex electrostatics, one often observes in protein adsorption studies the formation of irreversibly bound fraction of molecules that contact the substrate and a reversibly adsorbed fraction otherwise. This leads to the appearance of anomalous isotherms, characterized by considerable adsorption for negligible bulk protein concentration, which deviate from the Langmuir model. 相似文献
1000.
Xuelei Jia Dr. Honghui Lei Feipeng Han Tao Zhang Ying Chen Dr. Zhengshuang Xu Dr. Pratanphorn Nakliang Prof. Dr. Sun Choi Dr. Yian Guo Prof. Dr. Tao Ye 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(31):12932-12936
A concise and asymmetric total synthesis of five kopsane alkaloids that share a unique heptacyclic caged ring system was accomplished. The key transformation in the sequence involved a remarkable PtCl2-catalyzed intramolecular [3+2] cycloaddition, which allowed for the rapid assembly of pentacyclic carbon skeletons bearing 2,3-quaternary functionalized indoline. Expeditious construction of diverse indoline scaffolds with excellent control of diastereoselectivity demonstrated the broad scope and versatility of this key transformation. 相似文献