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71.
72.
Photoinduced electron transfer of the model system composed of vitamin E and duroquinone has been investigated using time-dependent density functional theory. Calculations for the excited states tell that the photoexcitation of the model system can directly yield the charge transfer states in which the vitamin E moiety is positively charged but the duroquinone moiety is negatively charged. Our theoretical investigations indicate that the second charge transfer state of the model system can also be produced through the decay of higher locally excited state S(4). Since S(4) state in the model system corresponds to S(1) state of the isolated duroquinone used as a model for peroxyl radical, and S(2) state has the character of electron transfer from the tertiary amine group of the vitamin E moiety to the duroquinone moiety, the decay from S(4) to S(2) corresponds to the dynamic process following the photoexcitation of the duroquinone moiety of the model system, i.e., the initial stage of antioxidant reaction of vitamin E. Calculations of the kinetic parameters for the electron transfer have been carried out in the framework of the Marcus-Jortner-Levich formalism. Our calculations confirm that the electron transfer from S(4) to S(2) possesses the character of the inverted regime and the barrier is negligibly small. 相似文献
73.
通过X射线衍射分析和超导量子干涉磁强计(SQUID)磁性测量,研究了Co替代Fe含量对居里温度在室温以上的磁制冷材料La(Fe1-xCox)11.7Al1.3(x=0.072,0.081)磁结构和磁性能的影响。La(Fe1-xCox)11.7Al1.3材料的居里温度随Co的含量增加而增加,La(Fe0.919Co0.081)11.7Al1.3的居里温度为311 K。当外场变化为1.9 T时磁熵变达到3.6 J·kg^-1·K^-1,RCP值为168.6 J·kg^-1,虽然它的磁熵变小于具有巨磁熵变的磁制冷材料,但是它在磁场为1.9 T时的制冷能力与这些材料相当。 相似文献
74.
Tian Yu-Peng Duan Chun-Ying Lu Zhong-Lin You Xiao-Zeng Thomas C.W. Mak 《Polyhedron》1996,15(24):4415-4420
The crystal structure of the 1,10-phenanthroline bis(S-methyl-β-N-(4-methyloxyphenyl)methylendithiocarbazide)nickel(II) adduct, (Ni(SN)2phen) [SN = S-methyl-β-N-(4-methyloxyphenyl)methylendithiocarbazide, PHEN = phenanthroline], has been determined by single crystal X-ray diffraction. The nickel atom is in an octahedral environment, surrounded by two chelating SN ligands and one chelating phen molecule. The nitrogen atoms from phen are in the cis configuration. The other chelating diamines adducts of the parent complex (Ni(SN)2) were also studied, where the chelating diamnies are 5-nitro-1,10-phenanthroline(NO2phen), 2,2′-bipyridine (bipy), 4,4′-methyl-2,2′-bipyridine (Mebipy). The equilibria were determined by UV-vis spectrometry in dichloromethane. The coordination ability of the added ligands were influenced by substitute groupings and steric factors. From the structure and addition equilibrium studies, the possible addition mechanisms are also discussed. 相似文献
75.
在恒定丙三醇质量分数x=0.1的条件下,测定了无液接电池(A)和电池(B)的电动势根据电池(A)电动势确定了丙三醇和水混合溶剂中的Ag-AgCl电极的标准电极电势,讨论了HCl的迁移性质;由电池(B)测得的电动势计算了HCl在该体系中的活度系数γA,计算的结果表明,对于所讨论的体系,在溶液中总离子强度保持恒定,HCl的活度系数服从Harned规则.在溶液组成恒定时,IgγA是温度倒数1/T的线性函数,讨论了混合物中HCl的相对偏摩尔焓及介质效应. 相似文献
76.
Tao-Min Huang Chun-Hui Deng Ying-Jia Yu Xiao-Wei Zheng Geng-Li Duan 《Chromatographia》2006,63(11-12):551-556
An accurate, simple and sensitive method based on reversed-phase high-performance liquid chromatography with UV detection has been developed for determination of tiopronin (TP) in human plasma. TP in plasma was reacted with p-bromophenacyl bromide (p-BPB) to give the TP-p-BPB adduct and this derivative was then extracted from the plasma on a silica gel cartridge. Potential interfering compounds were removed by washing with water, and the TP-p-BPB adduct was then eluted with acetonitrile. The organic phase obtained was evaporated to complete dryness under a stream of nitrogen. The residue was dissolved in acetonitrile and this solution was injected on to a reversed-phase ODS HPLC column. The mobile phase was usually the ternary mixture acetonitrile–water–trifluoroacetic acid, 40:59.88:0.12 (v/v). The retention times of TP-p-BPB and the internal standard adduct were 14.4 and 17.9 min, respectively. No interfering peaks were encountered in several blank plasma samples examined. The limit of detection for TP was 12 ng mL?1. Extraction recovery exceeded 70%. The calibration plot for the TP derivative was linear in the range 40?4000 ng mL?1, regression coefficient 0.9989, and the coefficient of the variation of the points of the calibration plot was below 10%. The method was validated appropriately and successfully applied to the determination of TP in human plasma. 相似文献
77.
Amperometric glucose biosensor based on electrodeposition of platinum nanoparticles onto covalently immobilized carbon nanotube electrode 总被引:6,自引:0,他引:6
A new amperometric biosensor for glucose was developed based on adsorption of glucose oxidase (GOx) at the gold and platinum nanoparticles-modified carbon nanotube (CNT) electrode. CNTs were covalently immobilized on gold electrode via carbodiimide chemistry by forming amide linkages between carboxylic acid groups on the CNTs and amine residues of cysteamine self-assembled monolayer (SAM). The fabricated GOx/Aunano/Ptnano/CNT electrode was covered with a thin layer of Nafion to avoid the loss of GOx in determination and to improve the anti-interferent ability. The immobilization of CNTs on the gold electrode was characterized by quartz crystal microbalance technique. The morphologies of the CNT/gold and Ptnano/CNT/gold electrodes have been investigated by scanning electron microscopy (SEM), and the electrochemical performance of the gold, CNT/gold, Ptnano/gold and Ptnano/CNT/gold electrodes has also been studied by amperometric method. In addition, effects of electrodeposition time of Pt nanoparticles, pH value, applied potential and electroactive interferents on the amperometric response of the sensor were discussed.
The enzyme electrode exhibited excellent electrocatalytic activity and rapid response for glucose in the absence of a mediator. The linear range was from 0.5 to 17.5 mM with correction coefficient of 0.996. The biosensor had good reproducibility and stability for the determination of glucose. 相似文献
78.
Effects of Calcination Temperature on the Acidity and Catalytic Performances of HZSM-5 Zeolite Catalysts for the Catalytic Cracking of n-Butane 下载免费PDF全文
The acidic modulations of a series of HZSM-5 catalysts were successfully made by calcination at different treatment temperatures, i.e. 500, 600, 650, 700 and 800 ℃, respectively. The results indicated that the total acid amounts, their density and the amount of B-type acid of HZSM-5 catalysts rapidly decreased, while the amounts of L-type acid had almost no change and thus the ratio of L/B was obviously enhanced with the increase of calcination temperature (excluding 800 ℃). The catalytic performances of modified HZSM-5 catalysts for the cracking of n-butane were also investigated. The main properties of these catalysts were characterized by means of XRD, N2 adsorption at low temperature, NH3-TPD, FTIR of pyridine adsorption and BET surface area measurements. The results showed that HZSM-5 zeolite pretreated at 800 ℃ had very low catalytic activity for n-butane cracking. In the calcination temperature range of 500-700 ℃, the total selectivity to olefins, propylene and butene were increased with the increase of calcination temperature, while, the selectivity for arene decreased with the calcination temperature.The HZSM-5 zeolite calcined at 700 ℃ produced light olefins with high yield, at the reaction temperature of 650 ℃ the yields of total olefins and ethylene were 52.8% and 29.4%, respectively. Besides, the more important role is that high calcination temperature treatment improved the duration stability of HZSM-5zeolites. The effect of calcination temperature on the physico-chemical properties and catalytic performance of HZSM-5 for cracking of n-butane was explored. It was found that the calcination temperature had large effects on the surface area, crystallinity and acid properties of HZSM-5 catalyst, which further affected the catalytic performance for n-butane cracking. 相似文献
79.
Yuan Zhihao Wang Yuhong Sun Yongchang Wang Jing Bie Lijian Duan Yueqing 《中国科学B辑(英文版)》2006,49(1):67-74
A nanocomposite photocatalyst composed of AlFeO3 and TiO2 is prepared, and characterized through X-ray diffraction. Application of the nanocomposite for the photodegradations of eosin
dye and methyl orange gives an improved photoactivity compared with TiO2-only nanomaterials. The optimal concentration of AlFeO3 in the composite is about 1.0 wt% under UV excitation, and 9.0 wt% under sunlight excitation for the improved photoactivity.
Furthermore, this nanocomposite is more active for eosin photodegradation if natural sunlight rather than UV is used. This
may be due to the reason that adding AlFeO3 nanoparticles into TiO2 matrix can promote the separation of photogener-ated charge carriers, and extend the photoresponse of TiO2 toward visible region, which results in an increase in the solar energy utilization efficiency. 相似文献
80.
Hu Chuanjiang Duan Chunying Meng Qingjin Liu Yongjiang Lu Changsheng Reng Xiaoming Chen Yijun Cao Mi 《Transition Metal Chemistry》2000,25(2):141-144
The mixed-valence molybdovanadate compound Na2(NH4)4[VIVVV
8Mo)O28] · 10H2O [Vanadata(6-)tetradeca--oxotetra-3-oxodi-6-oxoheptaoxo(oxomolybdate) nonatetrammonium disodium, decahydrate] has been synthesized from sodium molybdate(VI) dihydrate and sodium metavanadate dihydrate in aqueous solution by adding NH2OH · HCl. The molecular structure has been determined by X-ray diffraction and is based on the isopolydecavanadate structure. The molybdate atom is crystallographically disordered over 6MO6 octahedral sites. The e.s.r. spectrum clearly indicates that one vanadium atom has the oxidation number +4. 相似文献