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排序方式: 共有207条查询结果,搜索用时 46 毫秒
81.
Alexander F. Shchepetkin James C. McWilliams 《Journal of computational physics》2009,228(24):8985-9000
82.
Tributyltin compounds have been used for many years as wood preservatives. This study has provided, for the first time, an explanation for the previously reported dealkylation and/or volatilization of the tributyltin species in, and from, timber. Thus 119Sn NMR studies have shown that, on impregnation into timber, bis(tributyltin) oxide, (Bu3Sn)2O, is rapidly converted to other tributyltin species, Bu3SnOX, and that these subsequently undergo disproportionation to Bu4Sn and Bu2Sn(OX)2 compounds. We have additionally demonstrated that Bu4Sn, so produced, is not persistent in timber and is lost by volatilization. Since the rate of disproportionation of the Bu3SnOX species should be dependent upon the nature of the X group, it should be possible to affect significantly, if not to stop, this process by the use of alternative tributyltin fungicides, e.g. tributyltin methanesulphonate. However, tributyltin fungicides have been used successfully in wood preservation for at least 25 years. Therefore, it must be concluded that, even after disproportionation in timber, in service, sufficient preservative action is retained to prevent decay of wood under the conditions of natural exposure. 相似文献
83.
在从室温到500℃的温度范围内,用卢瑟福质子背散射技术分别测量了不同能量、不同剂量注入的纳米晶钛膜中氦的浓度分布,不同温度时的保持剂量及其释放浓度.发现氦在这种纳米晶粒膜中其氦-钛原子浓度比达到41%—52%时能在室温到100℃的温度下长期稳定保持,若其原子浓度达52%—74%时也能在室温环境有效保持.文中对这种具有大的界面体积比的膜能有效保持氦这种惰性元素的可能机理从能量观点进行了初步探讨.
关键词:
离子注入
纳米晶粒钛膜
氦
保持剂量 相似文献
84.
不确定型AHP中单一准则下增加一组元素的保序性条件 总被引:1,自引:0,他引:1
本对区间数集定义了两种合理的偏序关系,给出了不确定型AHP中单一准则下增加一组元素弱保序的一个充分条件和强保序的一个充要条件。 相似文献
85.
Marco Antonio P. Queirol Joo Tessarioli Neto Valter Arthur Frederico M. Wiendl Anna Lucia C. H. Villavicencio 《Radiation Physics and Chemistry》2002,63(3-6):341-343
After irradiating with a single dose of 50 Gy, ginger rhizomes were dipped into paraffin for coating, wrapped in a plastic film of low-density polyethylene, on perforated or non-perforated polivinyl chloride film, and compared with non-wrapping and non-irradiation as the controls. After treatments the rhizomes were maintained refrigerated at 13°C and 80% relative humidity. As a main result it could be observed that dipping into paraffin and wrapping with plastics resulted in smaller weight loss of the rhizomes. 相似文献
86.
Restricted systems are introduced and characterized. They are related with usual properties of spline spaces with relevant consequences in geometric modelling. It is a weaker property than local linear independence but it is preserved under a wide range of transformations. 相似文献
87.
88.
低温液晶显示器—加固理论与实践 总被引:1,自引:0,他引:1
该文对液晶显示器(LCD)低温加固的理论进行分析和研究。在此基础上,介绍一种新研制的机载低温液晶显示器。在显示器中设计了一套透明的加热、真空保温、抗眩光及电磁屏蔽装置,低温工作时,只需非常小的加热功率,就能使液晶显示器正常工作,同时可以利用该装置中的氧化铟锡(ITO)导电膜层满足显示器视窗对防眩光及电磁兼容(EMC)特性的要求。这种新型低温加固型LCD集多种特殊功能于一体,具有功耗低、亮度高、可靠性好、抗眩光、EMC性能好及结构便于组装等多项显著优点。 相似文献
89.
Analysis of DNS and LES of Flow in a Low Pressure Turbine Cascade with Incoming Wakes and Comparison with Experiments 总被引:1,自引:0,他引:1
The flow around a low-pressure turbine rotor blade with incoming periodic wakes is computed by means of DNS and LES. The latter
adopts a dynamic sub-grid-scale model. The computed results are compared with time-averaged and instantaneous measured quantities.
The simulation sreveal the presence of elongated flow structures, stemming from the incoming wake vorticity, which interact
with the pressure side boundary layer. As the wake approaches the upstream half of the suction side, its vortical structures
are stretched and align with the main flow, resulting in an impingement at virtually zero angle of attack. Periodically, in
the absence of impinging wakes, the laminar suction side boundary layer separates in the adverse pressure gradient region.
Flow in the laminar separation bubble is found to undergo transition via a Kelvin–Helmholtz instability. Subsequent impingement
of the wake inhibits separation and thus promotes boundary layer reattachment. LES provides a fair reproduction of the DNS
results both in terms of instantaneous, phase-averaged, and time-averaged flow fields with a considerable reduction in computational
effort.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
90.
Jorge Cervantes Guillermo Mendoza-Díaz Dolores Elena Alvarez-Gasca Antonio Martinez-Richa 《Solid state nuclear magnetic resonance》1999,13(4):481-269
We report the application of 29Si and 27Al magic angle spinning nuclear magnetic resonance (MAS NMR) studies on building stones from historical monuments to obtain direct information about the degree of degradation and to observe the changes in the consolidated material after treatment with tetraethoxysilane (TEOS). Using the data obtained from deteriorated materials, a diagnostic laboratory, a suitable treatment and recommendations for building conservation may infer. A case study is presented using stones from Guanajuato City Main Church (Central Mexico). X-ray diffraction patterns to characterize the species present in the stones agree with the solid state NMR results. 相似文献