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221.
On the Reaction Mechanism of the Complete Intermolecular O2 Transfer between Mononuclear Nickel and Manganese Complexes with Macrocyclic Ligands 下载免费PDF全文
Dr. Jhon Zapata‐Rivera Prof. Rosa Caballol Dr. Carmen J. Calzado Dr. Dimitrios G. Liakos Prof. Frank Neese 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(41):13296-13304
The recently described intermolecular O2 transfer between the side‐on Ni‐O2 complex [(12‐TMC)Ni‐O2]+ and the manganese complex [(14‐TMC)Mn]2+, where 12‐TMC and 14‐TMC are 12‐ and 14‐membered macrocyclic ligands, 12‐TMC=1,4,7,10‐tetramethyl‐1,4,7,10‐tetraazacyclododecane and 14‐TMC=1,4,8,11‐tetramethyl‐1,4,8,11‐tetraazacyclotetradecane, is studied by means of DFT methods. B3LYP calculations including long‐range corrections and solvent effects are performed to elucidate the mechanism. The potential energy surfaces (PESs) compatible with different electronic states of the reactants have been analyzed. The calculations confirm a two‐step reaction, with a first rate‐determining bimolecular step and predict the exothermic character of the global process. The relative stability of the products and the reverse barrier are in line with the fact that no reverse reaction is experimentally observed. An intermediate with a μ‐η1:η1‐O2 coordination and two transition states are identified on the triplet PES, slightly below the corresponding stationary points of the quintet PES, suggesting an intersystem crossing before the first transition state. The calculated activation parameters and the relative energies of the two transition sates and the products are in very good agreement with the experimental data. The calculations suggest that a superoxide anion is transferred during the reaction. 相似文献
222.
W. Russ Algar 《Analytica chimica acta》2010,673(1):1-25
A comprehensive review of the development of assays, bioprobes, and biosensors using quantum dots (QDs) as integrated components is presented. In contrast to a QD that is selectively introduced as a label, an integrated QD is one that is present in a system throughout a bioanalysis, and simultaneously has a role in transduction and as a scaffold for biorecognition. Through a diverse array of coatings and bioconjugation strategies, it is possible to use QDs as a scaffold for biorecognition events. The modulation of QD luminescence provides the opportunity for the transduction of these events via fluorescence resonance energy transfer (FRET), bioluminescence resonance energy transfer (BRET), charge transfer quenching, and electrochemiluminescence (ECL). An overview of the basic concepts and principles underlying the use of QDs with each of these transduction methods is provided, along with many examples of their application in biological sensing. The latter include: the detection of small molecules using enzyme-linked methods, or using aptamers as affinity probes; the detection of proteins via immunoassays or aptamers; nucleic acid hybridization assays; and assays for protease or nuclease activity. Strategies for multiplexed detection are highlighted among these examples. Although the majority of developments to date have been in vitro, QD-based methods for ex vivo biological sensing are emerging. Some special attention is given to the development of solid-phase assays, which offer certain advantages over their solution-phase counterparts. 相似文献
223.
The environment of Eu3+ in zinc-thallium-tellurite glass of the molar composition 60TeO2-30TlO0.5-9.9ZnO-0.1Eu2O3 was investigated by laser-induced fluorescence line narrowing (FLN) techniques using Eu3+ as a local site probe. From the site selective luminescence spectra of Eu3+ at 7 K, the energies of the Stark components of the 7F1 and 7F2 states were recorded and then the crystal field parameters Bnm were calculated assuming a C2v site symmetry. The ratios B22/B20 and B44/B40 for each excitation energy within 7F0-5D0 transition were obtained and compared with the values calculated for Eu3+ in other types of glasses. 相似文献
224.
J. M. C. Marques A. A. C. C. Pais P. E. Abreu 《Journal of computational chemistry》2010,31(7):1495-1503
Factors relevant for controlling the structures determined in the local optimization of argon clusters are investigated. In particular, the role of volume and shape for the box where initial structures are generated is assessed. A thorough characterization of the optimization is also presented, based on a nearest‐neighbor analysis, in clusters ranging from 30 to 55 atoms. This includes the assessment of the degree of preservation of aspects of the initial randomly generated structure in the final optimized counterpart, and the correlation between optimized energy and the number of nearest neighbors and average departure from the diatomic reference distance. The usefulness of this analysis to explore the energy landscape of atomic clusters is also highlighted. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010 相似文献
225.
以柠檬酸为配合剂,用溶胶-凝胶法制备了一组不同组成的Co-Al复合氧化物(CoAl_2O_4、CoCo0.5Al1.5O4、CoCoAlO_4、CoCo_(1.5)Al_(0.5)O_4、Co_3O_4),用于催化分解N_2O.用N_2物理吸附、X射线衍射(XRD)、扫描电镜(SEM)、H2程序升温还原(H2-TPR)、X射线光电子能谱(XPS)等技术对催化剂进行了结构表征,考察了复合氧化物组成、母液pH值、配合剂用量等制备参数对催化剂活性的影响.结果表明:用Al取代Co_3O_4中部分Co制备Co-Al复合氧化物,提高了催化剂的比表面积和催化活性,其中组成为CoCo_(1.5)Al_(0.5)O_4、母液pH=2、柠檬酸/金属离子(摩尔比)为1的催化剂活性较高.在CoCo_(1.5)Al_(0.5)O_4表面浸渍K2CO3溶液制得K改性催化剂,弱化了钴-氧化学键,提高了催化活性.其中0.02K/CoCo1.5Al0.5O4催化剂在有氧有水气氛400℃连续反应50h,N_2O转化率达97.1%. 相似文献
226.
Valence state parameters of all transition metal atoms in metalloproteins—development of ABEEMσπ fluctuating charge force field 下载免费PDF全文
Zhong‐Zhi Yang Jian‐Jiang Wang Dong‐Xia Zhao 《Journal of computational chemistry》2014,35(23):1690-1706
To promote accuracy of the atom‐bond electronegativity equalization method (ABEEMσπ) fluctuating charge polarizable force fields, and extend it to include all transition metal atoms, a new parameter, the reference charge is set up in the expression of the total energy potential function. We select over 700 model molecules most of which model metalloprotein molecules that come from Protein Data Bank. We set reference charges for different apparent valence states of transition metals and calibrate the parameters of reference charges, valence state electronegativities, and valence state hardnesses for ABEEMσπ through linear regression and least square method. These parameters can be used to calculate charge distributions of metalloproteins containing transition metal atoms (Sc‐Zn, Y‐Cd, and Lu‐Hg). Compared the results of ABEEMσπ charge distributions with those obtained by ab initio method, the quite good linear correlations of the two kinds of charge distributions are shown. The reason why the STO‐3G basis set in Mulliken population analysis for the parameter calibration is specially explained in detail. Furthermore, ABEEMσπ method can also quickly and quite accurately calculate dipole moments of molecules. Molecular dynamics optimizations of five metalloproteins as the examples show that their structures obtained by ABEEMσπ fluctuating charge polarizable force field are very close to the structures optimized by the ab initio MP2/6–311G method. This means that the ABEEMσπ/MM can now be applied to molecular dynamics simulations of systems that contain metalloproteins with good accuracy. © 2014 Wiley Periodicals, Inc. 相似文献
227.
An automatic system based on multisyringe flow injection analysis (MSFIA) and lab-on-valve (LOV) flow techniques for separation and pre-concentration of 226Ra from drinking and natural water samples has been developed. The analytical protocol combines two different procedures: the Ra adsorption on MnO2 and the BaSO4 co-precipitation, achieving more selectivity especially in water samples with low radium levels. 相似文献
228.
Syed Mustafa Muhammad Waseem Abdul Naeem Khizar Hussain Shah Tauqeer Ahmad Muhammad Safdar 《中国化学》2010,28(11):2204-2208
The current study focuses on the synthesis and sorption properties of two mixed oxides of iron and silicon prepared by physical mixing (M1) and sequential precipitation methods (M2). Both the mixed oxides were synthesized from equimolar ratios of Fe(OH)3 and SiO2 and characterized for surface area, EDX, XRD and PZC. The surface area, micropore volume and average pore width of the oxide M1 were higher as compared to the oxide M2. However, potentiometric titrations revealed that mixed oxide synthesized by this method had a very high capacity towards Cd2+ ions as compared to the mixed oxide M1. Sorption of Cd2+ ions at pH 5 on mixed oxide, M2 was found to increase with temperature in the range 288 to 318 K. Langmuir equation was found applicable to the sorption data with R2>0.99. Entropy (ΔS?), enthalpy (ΔH?) and free energy changes (ΔG?) were calculated which revealed the process to be endothermic and spontaneous in nature. 相似文献
229.
Abdoul-Fatah Kanta Ghislain Montavon Marie-Pierre Planche Christian Coddet 《Plasma Chemistry and Plasma Processing》2008,28(2):249-262
Modeling the behavior of air plasma spray (APS) process, one of the challenges nowadays is to identify the parameter interdependencies,
correlations and individual effects on coating properties, characteristics and influences on the in-service properties. APS
modeling requires a global approach which considers the relationships between coating characteristics/ in-service properties
and process parameters. Such an approach permits to reduce the development costs. This is why a robust methodology is needed
to study these interrelated effects. Artificial intelligence based on fuzzy logic and artificial neural network concepts offers
the possibility to develop a global approach to predict the coating characteristics so as to reach the required operating
parameters. The model considered coating properties (porosity) and established the relationships with power process parameters
(arc current intensity, total plasma gas flow rate, hydrogen content) on the basis of artificial intelligence rules. Consequently,
the role and the effects of each power process parameter were discriminated. The specific case of the deposition of alumina–titania
(Al2O3–TiO2, 13% by weight) by APS was considered. 相似文献
230.
The lipophilicity of the series of alpha-(4-phenylpiperazin-1-yl)-gamma-phthalimido-butyramides (1-8) has been investigated. Several methods, like reversed-phase thin-layer chromatography and high-performance liquid chromatography using reversed-phase RP18 and IAM.DD2 columns, were applied to determine RMO, log k0 and log k(0IAM) factors. The RP-TLC investigations were performed in mixtures of acetone-water and acetonitrile-water. For RP-HPLC method mixtures of acetonitrile, water and 0.01% TFA were used as the mobile phases while for IAM.DD2 investigations mixtures of acetonitrile and water were applied. The partition coefficients of compounds (1-8) were also calculated with the Pallas and CAChe programs. All the obtained data, both from experimental methods and computational calculations, were compared and a suitable conclusion was reached. 相似文献