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201.
M. J. Marks J. K. Sekinger 《Journal of polymer science. Part A, Polymer chemistry》1994,32(10):1885-1891
The types and concentrations of end groups present in bisphenol A-tetrabromobisphenol A copolycarbonates (BA-TBBA coPCs) have major effects on the copolymer solution washability and thermal stability. Six types of coPC end groups are possible: two by monophenol capping of each comonomer, two phenolics (BA-OH and TBBA-OH), and two carbamates (one from each comonomer). BA-TBBA coPCs were prepared by typical solution and interfacial methods and their phenolic and carbamate end group concentrations were correlated with their solution washability and thermal discoloration. Both phenolic and carbamate end groups proved deleterious to these two copolymer properties. An improved interfacial process that employs 4-N,N-dimethylaminopyridine as the coupling catalyst provides coPCs having low concentrations of phenolic and carbamate end groups and that, therefore, wash without emulsification and are thermally stable. © 1994 John Wiley & Sons, Inc. 相似文献
202.
The polymerization of 1,3-butadiene (BD) was carried out in the presence of a catalyst composed of neodymium 2-ethylhexanoate, triisobutyl aluminum, diisobutyl aluminum hydride (DIBAH), ethylaluminum sesquichloride and acetylacetone. The molecular weight of the BR could be controlled with DIBAH. The reactive polymer was then chemically modified with styreneoxide (STO). The STO content of BR increased with the decrease in the molecular weight of the BR. This polymer was modified by the STO at the chain terminal end. The physical properties of the vulcanizates with the modified BR were measured. The abrasion resistance and the tensile strength were found to be improved. 相似文献
203.
204.
周树昂 《应用数学和力学(英文版)》1990,11(3):215-237
The overall mechanical and electrical behaviors of elastic dielectric composites are investigated with the aid of the concept of material multipoles. In particular, by introducing a statistical continuum material multipole theory, the effects of the electric-elastic interaction and the microstructure (size, shape, orientation,...) of inhomogeneous particles on the overall behaviors of the composites can be obtained. A basic solution for an ellipsoidal elastic inhomogeneity with electric polarization in an infinite elastic dielectric medium is first given, which shows that classical Eshelby ’s elastic solution is modified by the presence of electric-elastic interaction. The overall macroscopic constitutive relations and their overall macroscopic material parameters accounting for electroelastic interaction effect are then derived for the elastic dielectric composites. Some quantitative calculations on the problems with statistical anisotropy, the shape effect and the electric-elastic interaction are finally given for dilute composites. 相似文献
205.
双材料反平面问题界面端奇异应力场分析 总被引:4,自引:0,他引:4
利用位移函数的级数展开,对任意角度的反平面问题界面端的应力场进行了分析研究,得到了全场解。研究一阶场后发现,奇异规律与一般平面问题界面端有显著区别,在界面端关于界面对称的情况下,平角界面端(θ1 = θ2 = θ = 90°) 应力场没有奇异性,其它形状的界面端随着角度θ 从90°到180°,奇异指数也从0到0.5。当界面端是非对称时,平角界面端(θ1 θ2 = 180°)、直角界面端(θ1 = 90°,θ2 = 180°)以及其它形状界面端的奇异指数是一个与两相材料常数比Γ有关的常数。以上两种情况下的应力强度因子完全类似单相材料中裂纹尖端附近应力强度因子,故可根据定义得到 相似文献
206.
分析了光纤端面倾斜对光能量耦合的影响和光纤接收角的变化。结果表明,光纤端面倾斜对光能量的耦合具有较大的影响,同时使光纤的接收角也产生较大的偏移。把这些结果与标定的具体情况相结合,提出了在高温计标定中应采取的措施,以提高系统的测量精度。 相似文献
207.
208.
Study on EDFA Gain Tilt and Nonlinear Distortion in an AM-VSB CATV Optical Fiber Transmission System 总被引:3,自引:0,他引:3
1IntroduCtionAMVSB(~litUdemodulationwithvestigialsideband)CATVoPticalfibertrandriSSdrisystemiswidelyaPpliedduetocomplete1ycomatibilitywtthekistingCATVtechntheyandoccuPationaverynarrowband.Theopticalpowerbudgetofthesystemistoollttle(about5~8dBm)toreallzealDngdistancetransndssion,andoPticalmodulationdegreeisalsorestrainedinanarrowrangeinordertOguaranteethenonlinearrequlrementssinceitissensitivetOthenonlineardistortion.EDFAisintroducedintothesystemtoimProvetheopticalpoWrbudget.Indongs… 相似文献
209.
Yoshiaki Terada Shokyoku Kanaoka Toshinobu Higashimura 《Journal of polymer science. Part A, Polymer chemistry》2000,38(1):229-236
Cationic polymerization of n‐butyl propenyl ether (BuPE; CH3CH CHOBu, cis/trans = 64/36) was examined with the HCl–IBVE (isobutyl vinyl ether) adduct/ZnCl2 initiating system at −15 ∼ −78 °C in nonpolar (hexane, toluene) and polar (dichloromethane) solvents, specifically focusing on the feasibility of its living polymerization. In contrast to alkyl vinyl ethers, the living nature of the growing species in the BuPE polymerization was sensitive to polymerization temperature and solvent. For example, living cationic polymerization of IBVE can be achieved even at 0 °C with HCl–IBVE/ZnCl2, whereas for BuPE whose β‐methyl group may cause steric hindrance ideal living polymerization occurred only at −78 °C. Another interesting feature of this polymerization is that the polymerization rate in hexane is as large as in dichloromethane, much larger than in toluene. A new method in determining the ratio of the living growing ends to the deactivated ones was developed with a devised monomer‐addition experiments, in which IBVE that can be polymerized in a living fashion below 0 °C was added to the almost completely polymerized solution of BuPE. The amount of the deactivated chain ends became small in hexane even at −40 °C in contrast to other solvents. Thus hexane turned out an excellent solvent for living cationic polymerization of BuPE. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 229–236, 2000 相似文献
210.
Zexing Cao Miquel Sol Hui Xian Miquel Duran Qianer Zhang 《International journal of quantum chemistry》2001,81(2):162-168
Hybrid density functional theory calculations on the structures, vibrational frequencies, electron binding and dissociation energies, and bonding properties of CuO$_{3}^{-}$ and CuO3 species have been carried out. Stable isomers containing an O3 subunit and composed of O2 bound to CuO have been located on the potential energy hypersurfaces of CuO$_{3}^{-}$ and CuO3. The isomers formed by O2 bonded to CuO in side‐on and end‐on coordination are more stable than those containing an O3 subunit. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 81: 162–168, 2001 相似文献