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31.
Issa RM Fayed TA Awad MK El-Kony SM 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,62(4-5):980-986
The absorption spectra of mono- and bis-azo-derivatives obtained by coupling the diazonium salts of aromatic amines and 2,7-dihydroxynaphthalene have been studied in six organic solvents. The different absorption bands have been assigned and the effect of solvents on the charge transfer band is also discussed. The diagnostic IR spectral bands and 1H NMR signals are assigned and discussed in relation to molecular structure. Also, semi-empirical molecular orbital calculations using the atom superposition and electron delocalization molecular orbital (ASED-MO) theory have been performed to investigate the molecular and electronic structures of these compounds. According to these calculations, an intramolecular hydrogen bonding is essential for stabilization of such molecules. 相似文献
32.
Khan KM Shujaat S Rahat S Hayat S Atta-ur-Rahman Choudhary MI 《Chemical & pharmaceutical bulletin》2002,50(11):1443-1446
Eight new beta-N-substituted acyl hydrazides along with their corresponding acyl derivatives were synthesized and screened for in vitro beta-glucuronidase inhibition and found to be active against the enzyme. All of these compounds were found to be noncompetitive inhibitors except for N'-(2-cyanoethyl)-4-hydroxy benzohydrazide (10), which was found to be an uncompetitive inhibitor. Structure-activity relationship studies indicated that the benzyloxy group present in compounds 12 and 13 is responsible for the beta-glucuronidase inhibition activity. 相似文献
33.
Mohammed Akhter Hossain Keiko Takahashi Hisakazu Mihara Akihiko Ueno 《Journal of inclusion phenomena and macrocyclic chemistry》2002,43(3-4):271-277
-Helix peptides bearing one unit of -cyclodextrin (-CD), one unit of pyrene and one unit of nitrobenzene (NB) in their side chains have been designed and synthesized as novel molecule-responsive devices.In both the CD-peptides,
-PR17 and
-PL17, the NB unit is separated from the CD unit by two turns of the helix. Two reference peptides (PL17, and -P17,) have also been synthesized. The circular dichroism studies in the peptide absorption region (200–250 nm)of
-PR17 and
-PL17 suggestthat the CD-peptides form stable-helixstructures (83–77%), which was destabilized by accommodating guest molecules (e.g., n-pentanol) into the CD cavity. It suggests that formation of intramolecular host–guest(CD–NB) complex stabilized thehelical structure and exogenous guest molecule excluded the appending NB moiety from inside to outside of the CD cavity, thereby causing destabilization of the helical structure and increasing the random coil content. The ICD spectra of the peptides in the pyrene and nitrobenzene absorption region (250–40 nm) suggest that NB forms inclusion complex with CD. The fluorescence studies revealed that the fluorescence of the pyrene unit is quenched by the NB unit in
-PR17 and
-PL17. The fluorescence intensity increases with increasing guest concentration for the CD-peptides.This guest-responsiveenhancement in the fluorescence intensity can be explained in terms of increased distance between the pyrene and NB moieties, which is caused by exclusion of the NB moiety from the CD cavity by guest accommodation. Using the guest-responsive fluorescence quenching properties of the CD-peptides, we have obtained binding constants for various short chain alkanols.
-PL17 has higher binding affinity to the guest molecules than its isomer,
-PR17, indicating that the location of functional groups on the peptide scaffold is important in molecule detection. 相似文献
34.
Hendrik Voigt Aaron Rigoni Evgeniy Boltynjuk Mohammed Reda Chellali Bonnie Tyler Harald Rösner Sergiy Divinski Horst Hahn Gerhard Wilde 《Advanced functional materials》2023,33(44):2302386
Comprehensive analyses of the atomic structure using advanced analytical transmission electron microscopy-based methods combined with atom probe tomography confirm the presence of distinct glass–glass interfaces in a columnar Cu-Zr nanoglass synthesized by magnetron sputtering. These analyses provide first-time in-depth characterization of sputtered film nanoglasses and indicate that glass–glass interfaces indeed present an amorphous phase with reduced mass density as compared to the neighboring amorphous regions. Moreover, dedicated analyses of the diffusion kinetics by time-of-flight secondary ion mass spectroscopy (ToF SIMS) prove significantly enhanced diffusivity, suggesting fast transport along the low density glass–glass interfaces. The present results further indicate that sputter deposition is a feasible technique for reliable production of nanoglasses and that some of the concepts proposed for this new class of glassy materials are applicable. 相似文献
35.
Jie Song Pengyi Zhang Mohammed Alkubati Yubin Bao Ge Yu 《Digital Communications & Networks》2022,8(4):466-475
Due to the complexity of blockchain technology, it usually costs too much effort to build, maintain and monitor a blockchain system that supports a targeted application. To this end, the emerging “Blockchain as a Service” (BaaS) makes the blockchain and distributed ledgers more accessible, particularly for businesses, by reducing costs and overheads. BaaS combines the high computing power of cloud computing, the pervasiveness of IoT and the decentralization of blockchain, allowing people to build their own applications while ensuring the transparency and openness of the system. This paper surveys the research outputs of both academia and industry. First, it introduces the representative architectures of BaaS systems and then summarizes the research contributions of BaaS from the technologies for service provision, roles, container and virtualization, interfaces, customization and evaluation. The typical applications of BaaS in both academic and practical domains are also introduced. At present, the research on the blockchain is abundant, but research on BaaS is still in its infancy. Six challenges of BaaS are concluded in this paper for further study directions. 相似文献
36.
Gamil A. Al-Hazmi Mohammed S. El-Shahawi Ahmed A. El-Asmy 《Transition Metal Chemistry》2005,30(4):464-470
The redox properties of the title mono- and binuclear copper(II) chelates have been investigated by cyclic voltammetry in DMF at a working platinum electrode. The cathodic reduction and anodic oxidation of the investigated chelates produced the corresponding electrochemical CuI and CuIIIspecies stable only in the voltammetric time scale, The effects of substituents on E1/2, redox properties and stability towards oxidation of the complexes were related to the electron-withdrawing or releasing ability of the substituents on the C=N1[H, CH3 or C6H5] and/or N4H [H, C2H5, C6H5 or pClC6H4] groups, The electron attracting substituents stabilize the Cu(II) complexes while electron-donating groups favor oxidation to Cu(III). Changes in the E1/2 for the complexes due to remote substituent effects could be related to changes in basicity of N4H.Thus, variation in N41-J has more influence on E1/2 than changes in C=N1. The correlation between E1/2 of the complexes and pKa of the ligands has been attributed to the spherical potential generated by the electron density of the donor atoms at the antibonding d orbitals. 相似文献
37.
Summary 3,4-Dicyano-5-aminopyrazole, H3,4(CN)25NH2pz (L) reacts either with anhydrous MCl2 or with [M(PPh3)2Cl2] to yield ML4Cl2 complexes (M = Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd or Hg), whose monomeric and covalent natures have been confirmed by their solubility in most non-polar solvents and their low electrical conductivities. The bonding mode of substituted pyrazole is inferred from the position of the (C-N) band in the i.r. spectra. The electronic spectra and the magnetic moments of these compounds were recorded. 相似文献
38.
Boudjahem AG Monteverdi S Mercy M Bettahar MM 《Langmuir : the ACS journal of surfaces and colloids》2004,20(1):208-213
We have studied the effect of silica of quartz-type on the reducibility of nickel acetate in aqueous hydrazine (80 degrees C, pH = 10-12) and metal particle formation. The obtained materials were characterized by X-ray diffraction, transmission electron microscopy, and thermodesorption experiments. With nickel acetate alone, the reduction was partial (45%) and a metal film at the liquid-gas interface or a powdered metal precipitate with an average particle size of 120 nm was obtained. In the presence of silica as the surfactant, the reduction of nickel acetate was total and the nickel phase deposited as a film on the support with an average particle size of 25 nm. Supported nickel acetate was also totally reduced. Crystallites of a mean particle size of about 3 nm were obtained. Decreasing the nickel content or increasing the hydrazine/nickel ratio decreased the metal particle size. Whiskers were formed for low nickel loadings. Hydrogen thermal treatment of the reduced phase showed that the organic acetate fragment, belonging to the precursor salt, still remained strongly attached to the nickel phase. The amount of the retained organic matrix depended on the metal particle size. Surface defects are suggested as active sites, which enhanced nickel ion reduction in the presence of silica as the surfactant or support. Metal-support interactions and the nucleation/ growth rate were the main factors determining the size and morphology of the supported metal particles formed. The organic matrix covered the reduced nickel phase. 相似文献
39.
El-Said Asma I. Zidan Amna S. A. El-Meligy Mahmoud S. Aly Aref A. M. Mohammed Omar F. 《Transition Metal Chemistry》2001,26(1-2):13-19
Complexes of 1,10-o-phenanthroline (o-phen)-NiII and CuII with dithiocarbamates derived from -amino acids (glycine, phenylalanine, alanine, methionine and tryptophan) were synthesized and characterized by chemical analysis, spectral and thermal studies and by biological screening; the complexes are non-electrolytes. The empirical formula are [Ni(o-phen)2(aadtc)] and [Cu2(o-phen)2(phaladtc)(H2O)2Br2] where, aadtc = glycinyl-, phenylalaninyl-, alaninyl-, methioninyl- and tryptophanyldithiocarbamate and phaladtc = phenylalaninyldithiocarbamate. The structure of these complexes is probably octahedral. Molecular association through hydrogen bonding between the —NH and the carboxylate groups is proposed for the NiII complexes. The CuII complex is dimeric with the phenylalaninyldithiocarbamate acting as a bridge. 相似文献
40.
Mohammed Ejaz 《Mikrochimica acta》1976,65(6):643-650
Summary Radiochemical procedures have been worked out to prepare234Th(UX1) with and without carrier from uranium using N-oxide of 4-(5-nonyl)pyridine in sulphuric acid media. This reagent has also been employed in the development of a combined solvent extraction-ion exchange-spectrophotometric method for the determination of thorium in various samples.
Zusammenfassung Radiochemische Methoden zur Herstellung von234Th(UX1) aus Uran mit und ohne Träger und unter Verwendung von 4-(5-Nonyl)pyridin-N-oxid in schwefelsaurer Lösung wurden ausgearbeitet. Dieses Reagens wurde auch für die Ausarbeitung einer Thoriumbestimmung in verschiedenartigen Proben auf der Grundlage von Extraktion, Ionenaustausch und Spektro-photometrie verwendet.相似文献