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991.
Sung Woo Moon Gun-Dae Lee Seong Soo Park Seong-Soo Hong 《Reaction Kinetics and Catalysis Letters》2004,82(2):303-310
Catalytic combustion of chlorobenzene over supported vanadium oxides has been investigated. TiO2 was prepared by the sol-gel method from titanium isopropoxide. The supported vanadium oxide catalysts have been prepared
by precipitation-deposition and impregnation method and characterized by XRD, FT-Raman and TPR. In the VOx/TiO2catalysts prepared using the impregnation method, when vanadium loading reaches 3 wt.%, the activity shows a maximum. However,
in the VOx/TiO2catalysts prepared by precipitation-deposition, when vanadium loading reaches 7 wt.%, the activity shows a maximum. This result
suggests that the precipitation-deposition can yield a higher metal loading on the support and a high dispersion compared
to the impregnation method.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
992.
Luis A.?León Rafael?Notario Jairo?QuijanoEmail author Ederley?Vélez Claudia?Sánchez J. Camilo?Quijano Nouria?Al-Awadi 《Theoretical chemistry accounts》2003,110(6):387-394
Theoretical studies on the thermolysis in the gas phase of 4-arylideneimino-1,2,4-triazol-3(2H)-ones and 4-arylideneimino-1,2,4-triazol-3(2H)-thiones were carried out using density functional theory methods, at the B3LYP/6-31G(d) and B3LYP/6-311+G(2d,p) levels of theory. The proposed reaction mechanism occurs in one step, leading to the formation of 3-hydroxy-(2H)-1,2,4-triazole or 3-mercapto-(2H)-1,2,4-triazole and a 4-substituted benzonitrile, via a six-membered cyclic transition state. The progress of the reactions was followed by means of the Wiberg bond indices. The results indicate that the transition states have character intermediate between reactants and products, and the calculated synchronicities show that the reactions are slightly asynchronous, in the case of triazolones, and show a higher asynchronicity in the case of triazolthiones. The bond-breaking processes are slightly more advanced than the bond-forming ones, indicating a small bond deficiency in the transition states. Kinetic and activation parameters for the reactions studied have been calculated and compared with available experimental data.From the Proceedings of the 28th Congreso deQuímicos Teóricos de Expresión Latina (QUITEL 2002) 相似文献
993.
994.
Alireza Haghiri Ilkhechi 《Journal of organometallic chemistry》2005,690(8):1971-1977
Reaction of the ferrocenyl(dimethylamino)boranes FcB(Me)NMe2, Fc2BNMe2, and 1,1′-fc[B(Me)NMe2]2 with 1:1 mixtures of pyrazole and potassium pyrazolide in refluxing THF gave the potassium salts of the ferrocene-based bis(pyrazol-1-yl)borate ligands FcB(Me)pz2K, Fc2Bpz2K, and 1,1′-fc[B(Me)pz2]2K2 in good yield (Fc: ferrocenyl, fc: ferrocenylene, pz: pyrazolyl). In the solid state, FcB(Me)pz2K and Fc2Bpz2K form centrosymmetric dimers with short K?Cp contacts suggesting an η5 coordination mode of the potassium ion. The crystal lattice of the ditopic ligand 1,1′-fc[B(Me)pz2]2K2 consists of coordination polymer strands featuring essentially the same structural motif that has been observed for the monotopic derivatives. All three scorpionate ligands are thus promising building blocks for the preparation of ferrocene-containing multiple-decker sandwich complexes. 相似文献
995.
STUDY ON 1-HEXENE POLYMERIZATION BASED ON ZIEGLER-NATTA CATALYSTS WITH DOPED SUPPORT 总被引:1,自引:0,他引:1
XueJiang Zhi-qiangFan 《高分子科学》2004,(4):305-308
A series of Ti/Mg supported catalysts are prepared by using ball-milled mixtures of MgCl2-ethanol adducts and NaCl as supports, and 1-hexene polymerizations catalyzed by the novel catalysts are studied. It is found that the molecular weight distribution of poly(1-hexene) becomes apparently narrower when catalysts with doped supports are used, indicating that changing the structure of the support is an effective way to regulate the active center distribution of heterogeneous Ziegler-Natta catalyst. 相似文献
996.
During the heating of YBCO a peritectic reaction takes place at 1020C, which can be described by: 2YBa2Cu3O7–xY2BaCuO5+L+(1-2x)/2O2 (1) whereL = 3BaCuO2 +2CuO is a fluid with limited amount of yttrium.It has been reported, that many parameters can influence the reaction. From one side not only the starting size of grains but also the heating rate have an influence on the resulting Y2BaCuO5-phase. From the other side, there is a change of the peritectical temperature caused by changing of the partial pressure of O2 and the presence of parasitic phase.From general kinetic consideration one can draw the conclusion, that different mechanisms (nucleation, phase-boundary reaction and diffusion) can control the reaction.Using DTA/TG measurements, the peritectic reaction has been examined. Classical kinetic methods (Kissinger and Friedman) has been used. The Friedman method has given the dependence of the activation energy from reaction degree. This suggests many steps reactions. The dependence of the DTA-peaks from the heat rate suggest a parallel steps of reaction. This assumption can be motivated by evaluation of free O2, one solid and liquid phase formation. Amount of this phases depends on the heating rate. Additionally X-ray and microscopic methods has been used. In this way was shown, that the perovskit structure is stable up to peritectical temperature and than is dramatically destroyed. From microscopic observations has been got information about shape and size of solid phase and it's creation as a function of temperature, time and starting grain size.
Die Arbeit wurde BMBF gefördert und durch Land NRW unterschtützt. 相似文献
997.
998.
999.
Ni^2—交换蒙脱石中的镍物种及焙烧温度影响研究 总被引:2,自引:0,他引:2
对一组自制Ni^2+交换蒙脱石样品中镍物种的存在在形及焙烧温度影响进行了TPR和XRD考察结果表明,样品中镍负载量等于或小于Ni^2+的交换量时,镍主要以难还原听可交换性阳离子Ni(OH)^q+x和易还原的自由态镍Ni(OH)2或NiO两种形式存在。 相似文献
1000.
Masahiko Miyauchi Yoshinori Kawaguchi Akira Harada 《Journal of inclusion phenomena and macrocyclic chemistry》2004,50(1-2):57-62
-Cyclodextrin having cinnamamide at 6- or 3-positions (6-CiNH--CD, 3-CiNH--CD) and -cyclodextrin with cinnamamide on 6-position (6-CiNH--CD) have been prepared. Supramolecular structures were formed in the solid state or aqueous solutions and characterized by measurements of NMR and vapor pressure osmometry (VPO). The results indicate that 6-CiNH--CD formed insoluble supramolecular polymers in the solid state, while 6-CiNH--CD and 3-CiNH--CD formed supramolecular complexes in aqueous solutions. 6-CiNH--CD was found to form a dimer in an aqueous solution. 3-CiNH--CD formed intermolecular complexes to give supramolecular polymers. The differences of the position of guest part on cyclodextrins caused to give a variety of supramolecular structures in aqueous solutions. 相似文献