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21.
22.
PVDF/PAN共混超滤膜 总被引:11,自引:0,他引:11
PVDF/PAN共混超滤膜尹秀丽*宋艳秋(天津纺织工学院材料科学系天津300160)关键词聚偏氟乙烯,聚丙烯腈,共混,超滤膜1996-11-20收稿,1997-05-07修回共混是改变高分子材料性能的重要手段,已发现用聚合物共混的方法能制得性能优异的... 相似文献
23.
C. Lartigue A. Guillermo J. P. CohenAddad 《Journal of Polymer Science.Polymer Physics》1997,35(7):1095-1105
Longitudinal relaxation of proton magnetisation was used to characterize the molecular motions of PEO chains in compatible PEO (hydrogenated)/PMMA (deuterated) blends. Both the temperature and the PEO concentration, Φ, were varied. A maximum in the spin–lattice relaxation rate was observed and its properties were analyzed as a function of Φ. For Φ ≤ 0.50, the maximum is observed below the glass transition temperature of the blend; this shows that PEO chains dispersed in a matrix of PMMA remain highly mobile on a local scale even below Tg(Φ). A frequency–temperature correspondence procedure, applied to the measurements performed at two Larmor frequencies, 32 and 60 MHz, leads to a characteristic correlation time for PEO molecular motions. Its temperature dependence obeys a WLF free volume relation above the glass transition of the blends. The PEO free volume fraction and its thermal expansion are strongly reduced by the presence of the PMMA chains. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1095–1105, 1997 相似文献
24.
以熔融缩聚方法全盛了具有苯烷基侧链取代的全芳香液晶聚酯,用TG,DSC,热台偏光显微镜研究了聚酯的热性能,并讨论了取代基对聚酯热性能的影响,所有合成的聚酯均为热致型液晶,且具有较低的相转变温度。特别是当聚对苯二甲酸对苯二酚酯的两个苯环上分别取代了叔丁基和苯烷基,或取代了两个苯烷基侧链后,聚酯的熔融温度下降到225℃以下,并可在室温下溶于普通的有机溶剂中。 相似文献
25.
经多步反应合成3种含8-羟基喹啉侧基聚酯(P7~P9),进一步与无水醋酸锌和六水氯化铝反应,得到6种聚酯锌、铝配合物(P7-Zn~P9-Zn,P7-Al~P9-Al)。 采用元素分析、红外光谱、紫外可见光谱、核磁共振氢谱、凝胶渗透色谱、热重分析仪、差示扫描量热和荧光光谱等技术手段对其结构和性能进行表征。 P7~P9易溶于N,N-二甲基甲酰胺(DMF)、N,N-二甲基乙酰胺(DMAC)、二甲基亚砜(DMSO)和N-甲基吡咯烷酮(NMP),P7-Zn~P9-Zn和P7-Al~P9-Al部分溶于DMF、DMAC、DMSO和NMP。 P7~P9的质均相对分子质量(Mw)为1.79×104、2.14×104和2.52×104 g/mol,相对分子质量分布指数PDI为1.54、1.64和1.72。 P7~P9的5%失重温度分别为291.6、291.3和284.9 ℃,P7-Zn~P9-Zn、P7-Al~P9-Al的5%失重温度分别为348.7、339.2、334.6、316.1、316.7和316.0 ℃。 P7~P9的玻璃化转变温度(Tg)分别为121.8、106.2和86.4 ℃,聚酯锌、铝配合物的Tg均高于180 ℃。 P7~P9的DMF溶液(5×10-5 mol/L)在413~418 nm处发紫色荧光,P7-Zn~P9-Zn、P7-Al~P9-Al的DMF溶液(5×10-5 mol/L)分别在509~513和485~487 nm处发强绿色荧光,固体分别在516~519和492~497 nm处发强绿色荧光。 P7~P9、P7-Zn~P9-Zn和P7-Al~P9-Al的荧光量子产率分别为5.5%~8.4%、21%~28%和23%~29%。 相似文献
26.
Herbert Barthel Michael Dreyer Torsten Gottschalk-Gaudig Victor Litvinov Ekaterina Nikitina 《Macromolecular Symposia》2002,187(1):573-584
Fumed silica, a synthetic silicon dioxide, is a powerful rheological additive for resins and paints to introduce thixotropy or even a yield point. The rheological effectiveness of fumed silica is based on its ability to form percolating networks which immobilize large volumes of liquid. By a combination of advanced rheological experiments, spectroscopical investigations, and quantum chemical calculations it could be demonstrated that the formation and stability of the silica network is strongly influenced by particle-resin interactions. The results can be used to develop comprehensive models, which explain the rheological performance of different grades of fumed silica in different resins. 相似文献
27.
Watanabe T. Zhang G. Z. Yoshida H. Kawai T. 《Journal of Thermal Analysis and Calorimetry》2003,72(1):57-64
The miscibility of crystalline syndiotactic polystyrene (SPS)/non-crystalline atactic polystyrene (APS) blend was estimated
by the crystallization dynamics method, which evaluated the nucleation rate, the crystal growth rate and the surface free
energy parameter. The melting temperature depression suggested that SPS/APS blends were the miscible system but not in molecular
level. The relationship between the blend content and the chemical potential difference evaluated at a constant crystal growth
rate showed a good linear relationship. These facts suggested that SPS/APS blends contained the concentration fluctuation
with the size between few nm to less than 80 nm.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
28.
Hamidreza Enshaei Brenda G. Molina Luis J. del Valle Francesc Estrany Carme Arnan Jordi Puiggalí Núria Saperas Carlos Alemn 《Macromolecular bioscience》2019,19(8)
Ambroxol is a pharmacological chaperone (PC) for Gaucher disease that increases lysosomal activity of misfolded β‐glucocerebrosidase (GCase) while displaying a safe toxicological profile. In this work, different poly(ε‐caprolactone) (PCL)‐based systems are developed to regulate the sustained release of small polar drugs in physiological environments. For this purpose, ambroxol is selected as test case since the encapsulation and release of PCs using polymeric scaffolds have not been explored yet. More specifically, ambroxol is successfully loaded in electrospun PCL microfibers, which are subsequently coated with additional PCL layers using dip‐coating or spin‐coating. The time needed to achieve 80% release of loaded ambroxol increases from ≈15 min for uncoated fibrous scaffolds to 3 days and 1 week for dip‐coated and spin‐coated systems, respectively. Furthermore, it is proven that the released drug maintains its bioactivity, protecting GCase against induced thermal denaturation. 相似文献
29.
Reyhan Ozdogan Ozgun Daglar Hakan Durmaz Mehmet Atilla Tasdelen 《Journal of polymer science. Part A, Polymer chemistry》2019,57(22):2222-2227
In this study, we describe the preparation and characterization of a new class of thermoset hybrid networks containing aliphatic polyester and polyhedral oligomeric silsesquioxanes (POSS). The copper‐free 1,3‐dipolar cycloaddition click reaction of internal alkyne functionalized aliphatic polyester and multifunctional azido POSS with different concentrations led to highly crosslinked thermoset networks. The click reactions performed under ambient conditions (i.e., in tetrahydrofuran at room temperature for 1 day) in the absence of any catalyst. The chemical composition of hybrid networks and homogenous distribution of POSS molecules were confirmed by Fourier transform infrared spectroscopy and scanning electron microscopy with energy dispersive spectroscopy. The swelling ratios of hybrid networks were commonly decreased by increasing POSS‐N3 content and by changing polar solvents to apolar solvents. Thermogravimetric analysis results demonstrated that the thermal stability of hybrid networks increased with higher POSS feeding ratio. Tensile tests were applied to evaluate the mechanical properties of hybrid networks. Compared to neat aliphatic polyester, the mechanical properties of hybrid networks significantly improved. For instance, the tensile strength were enhanced from 5 MPa to 19 MPa by increasing the concentration of azido functionalized POSS from 10 to 40. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2222–2227 相似文献
30.
Hans Eliot Edling Matthew Vincent Herv Marand Samantha J. Talley Kevin Barr Robert B. Moore S. Richard Turner 《Journal of Polymer Science.Polymer Physics》2019,57(15):973-980
Structurally rigid copolyester thermoplastics were synthesized from 1,4‐cyclohexanedimethanol and the diesters dimethyl biphenyl‐4,4′‐dicarboxylate and dimethyl 2,6‐naphthalenedicarboxylate (DMN) via conventional melt transesterification. Conventional differential scanning calorimetry (CDSC) showed all compositions to exhibit multiple endotherms upon heating. Wide‐angle X‐ray diffraction analysis showed copolyester compositions to exhibit the crystalline structure of either the homopolyester Poly(1,4‐cyclohexylenedimethylene 2,6‐naphthalate) (PCN) or the homopolyester Poly(1,4‐cyclohexylenedimethylene 4,4′‐bibenzoate) (PCB), but not both simultaneously. Further thermal analysis using CDSC and fast DSC investigated the origin of the multiple endotherm behavior. While three endotherms are observed for low heating rates, the upper two endotherms appear to merge at heating rates about 1–5 °C s?1 and a single endotherm remains above heating rates about 10–50 °C s?1. While the behavior of the upper two endotherms is undeniably consistent with the mechanism of melting–recrystallization–remelting (MRR), we suggest that the low endotherm is likely associated with the melting of constrained secondary crystals, although MRR effects cannot be ruled out. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 973–980 相似文献