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排序方式: 共有893条查询结果,搜索用时 31 毫秒
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J. A. Ramos M. Larrañaga I. Mondragon W. Salgueiro A. Somoza S. Goyanes G. H. Rubiolo 《先进技术聚合物》2009,20(1):35-38
A set of diglycidylether of bisphenol‐A (DGEBA)/4,4′‐diaminodiphenylmethane (DDM) epoxy matrix modified with poly(ethylene oxide) (PEO), pre‐cured at two different temperatures, was examined by positron annihilation lifetime spectroscopy (PALS). The aim was to investigate the correlation between local free volume and mechanical properties. A negative deviation from the linear additivity rule of the local free volume is observed at both cure schedules. Using together the local free volume and mechanical results allows to conclude that the cure temperature makes small contribution to the flexural strength and modulus of blends but is responsible for the composition‐dependent rise of the fracture toughness. It is proposed that this behavior is a consequence of the nearest‐neighbor intrachain contacts or self‐association of the epoxy‐OH groups during cure leading to a non‐uniform space distribution of the DGEBA–PEO contacts, which causes the deflection of the crack path. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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84.
N-Propargylic beta-enaminones have been used as common intermediates for the synthesis of polysubstituted pyrroles and pyridines. Best results have been obtained using DMSO as solvent. In the presence of Cs(2)CO(3) N-propargylic beta-enaminones are cyclized to pyrroles in good to high yields, whereas omitting bases and using CuBr leads to the selective formation of pyridines. 相似文献
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Giancarlo Masci Marco Diociaiuti Vittorio Crescenzi 《Journal of polymer science. Part A, Polymer chemistry》2008,46(14):4830-4842
Thermosensitive anionic block copolymers of sodium 2‐acrylamido‐2‐methylpropanesulfonate (AMPS) and N‐isopropylacrylamide (NIPAAM) with different block lengths were prepared by atom transfer radical polymerization (ATRP). Controlled polymerization was achieved by using ethyl 2‐chloropropionate (ECP) as initiator and CuCl/CuCl2/tris(2‐dimethylaminoethyl)amine (Me6TREN) catalytic system in DMF:water 50:50 (v/v) mixtures at 20 °C. Blocks lengths ranging from 36 to 98 repeating units were obtained. The association properties in aqueous solutions at different NaCl ionic strengths were studied as a function of temperature and polymer concentration by dynamic light scattering, fluorescence spectroscopy, and energy‐filtered transmission electron microscopy. The block copolymers with a higher pNIPAAM/pAMPS ratio formed spherical core‐shell type micelles independently of the ionic strength. The block copolymers with lower pNIPAAM/pAMPS ratio formed core‐shell type micelles at high ionic strength. Larger particles were observed at low ionic strength, which could be due to the formation of vesicles or compound micelles/micellar clusters. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4830–4842, 2008 相似文献
87.
Giancarlo Verardo Irene Duse Alessandro Callea 《Rapid communications in mass spectrometry : RCM》2009,23(11):1607-1618
Underivatized oligosaccharides were analyzed by electrospray ionization (ESI) using a linear ion trap mass spectrometer in the negative ion mode with post‐column addition of an aqueous solution of formic acid. Under these conditions all oligosaccharides showed the presence of the corresponding formate adduct [M + HCOO]? with high intensity and easy subsequent low‐energy collision‐induced dissociation (CID) fragmentation using successive MSn experiments. A careful examination of the mass spectra obtained from these MSn experiments pointed out some significant differences useful to identify and quantify the single components in mixtures of coeluted disaccharides. This new sensitive and rapid method was successfully applied to the quantification of oligosaccharides in some juices minimizing sample handling. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
88.
Bunyamin Karagoz Giancarlo Galli Hakan Durmaz Gurkan Hizal Umit Tunca Niyazi Bicak 《Colloid and polymer science》2010,288(5):535-542
A novel strategy was developed for tailoring of SiO2 and TiO2 nanoparticle surfaces with poly(ε-caprolactone) (PCL). Thus, a self-curable polyester, poly(2-hydroxypropylene maleate) was
adsorbed on the nanoparticle surfaces and heated to 180 °C to give a cross-linked polyester layer with residual hydroxyalkyl
groups on their surfaces. Surface-initiated polymerization of ε-caprolactone from hydroxyalkyl groups on the surfaces yielded
core-shell nanoparticles with cross-linked core and PCL shells (22.2–71.4%). The organic shell layers around the nanoparticle
cores were evidenced by transmission electron microscopy, dynamic light scattering, and thermogravimetric analyses techniques.
The core-shell nanoparticles were then employed in preparing the stable and the homogenous dispersions with poly(methyl methacrylate-stat-butyl acrylate) solutions. An application of the solutions onto glass substrates yielded uniform and nearly transparent free
standing films (40–60 μm) with good homogeneity as inferred from scanning electron microscopy pictures. 相似文献
89.
Seydou Yao Giancarlo DellaVentura Cyril Petibois 《Analytical and bioanalytical chemistry》2010,397(6):2079-2089
Asbestos is a fiber causing lung diseases such as asbestosis and mesothelioma. Although the process involving these diseases
remains to be elucidated for developing drugs and treatments, direct consequences of fiber exposure in humans have been clearly
demonstrated. These diseases are first characterized by histological heterogeneity and combine chronic inflammation with fibrosis
and cellular alterations. As a consequence, asbestosis is usually diagnosed at advanced stages of the disease and treatments
are usually inefficient to cure the patients. Here, we review the links established between asbestos fiber chemistry and morphology
with the occurrence of associated lung diseases. Cytological and histological aspects of diseases are described with respect
to current analytical capabilities, notably for microscopy techniques. 相似文献
90.