全文获取类型
收费全文 | 6728篇 |
免费 | 1623篇 |
国内免费 | 1621篇 |
专业分类
化学 | 4249篇 |
晶体学 | 399篇 |
力学 | 648篇 |
综合类 | 71篇 |
数学 | 95篇 |
物理学 | 4510篇 |
出版年
2024年 | 5篇 |
2023年 | 48篇 |
2022年 | 154篇 |
2021年 | 169篇 |
2020年 | 148篇 |
2019年 | 135篇 |
2018年 | 161篇 |
2017年 | 230篇 |
2016年 | 296篇 |
2015年 | 252篇 |
2014年 | 332篇 |
2013年 | 532篇 |
2012年 | 501篇 |
2011年 | 592篇 |
2010年 | 522篇 |
2009年 | 600篇 |
2008年 | 538篇 |
2007年 | 591篇 |
2006年 | 607篇 |
2005年 | 486篇 |
2004年 | 454篇 |
2003年 | 330篇 |
2002年 | 311篇 |
2001年 | 269篇 |
2000年 | 260篇 |
1999年 | 219篇 |
1998年 | 196篇 |
1997年 | 188篇 |
1996年 | 164篇 |
1995年 | 152篇 |
1994年 | 116篇 |
1993年 | 81篇 |
1992年 | 88篇 |
1991年 | 68篇 |
1990年 | 54篇 |
1989年 | 28篇 |
1988年 | 28篇 |
1987年 | 21篇 |
1986年 | 8篇 |
1985年 | 9篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 3篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有9972条查询结果,搜索用时 15 毫秒
141.
Marina Lulla Jelena Asari Jaan Aarik Kaupo Kukli Raul Rammula Unto Tapper Eero Kauppinen Väino Sammelselg 《Mikrochimica acta》2006,155(1-2):195-198
Quantitative electron probe microanalysis of highly insulating materials is a complicated problem, partially solved by coating
samples with grounded thin conductive layers or using novel scanning electron microscopy (SEM) techniques, such as low-voltage
and/or variable pressure SEM. In this work, some problems of quantitative X-ray microanalysis of thin HfO2 films, in particular the possibility to determine mass thickness correlated to the density of the layer material, are discussed.
For comparison, Al2O3, Ta2O5 and TiO2 films grown onto both semiconductive Si and insulating quartz substrates were also analysed. All the films studied were synthesized
by atomic layer deposition method. 相似文献
142.
Ginting Suka IrwanShin-ichi Kuroda Hitoshi Kubota Takashi Kondo 《European Polymer Journal》2002,38(6):1145-1150
The effect of monomer concentration on photografting of methacrylic acid (MAA) onto linear low-density polyethylene (PE) film (thickness=30 μm) was investigated at 60 °C in water solvent together with the location of MAA-grafted chains. Xanthone was used as a photoinitiator which was coated on the film sample earlier. The higher percentage of grafting and graft efficiency were afforded for the system with the higher monomer concentration. The resultant MAA-grafted films were subjected to measurements of pH-responsive character and ability to adsorb cupric ion in order to understand the characteristics of function introduced. The grafted samples exhibited the pH-responsive character, where they shrank and swelled in acidic and alkaline media, respectively. The pH-responsive character of the grafted films was higher for the samples prepared in the system with a higher monomer concentration. Moreover, the grafted samples exhibited the ability to adsorb cupric ion, and the ability was reduced when the sample was prepared in the system with a higher monomer concentration. The different extents of the pH-responsive character and ability to adsorb cupric ion of the resulting grafted PE films were discussed in terms of location of grafted chains in the film substrate, which was determined by a scanning electron microscope and an attenuated total reflection infrared spectroscopy. 相似文献
143.
Saw-Peng Yew 《Polymer Degradation and Stability》2006,91(8):1800-1807
This study aims to evaluate the photocatalytic activity and biodegradation of polyhydroxybutyrate (PHB) films containing titanium dioxide (TiO2). Nanosized TiO2 photocatalysts were immobilized onto PHB film to overcome the difficulty of the recovery process. PHB is a suitable base material as it is naturally biodegradable and is produced from renewable resources. The photocatalytic degradation of organic compounds, photocatalytic sterilization activity and biodegradation rate in garden soil of PHB-TiO2 composite films were investigated. After an hour under solar illumination, 96% of methylene blue solution was decolorized. The antibacterial activity against Escherichia coli (E. coli) using PHB-TiO2 composite film exhibited enhanced photocatalytic sterilization activity over time. As for the ability to biodegrade, PHB-TiO2 composite films placed on soil surface with no direct solar illumination showed slower degradation rate compared to those receiving direct solar illumination. Interestingly, the latter composite films showed faster degradation rates compared to pure PHB films indicating that the degradation is mainly due to photocatalytic activity. PHB-TiO2 composite films buried in soil generally showed slower degradation rates compared to pure PHB films and were dependent on the soil microbial activity. 相似文献
144.
Kojima Kunihiko Miyazaki Mitsuharu Mizukami Fujio Maeda Kazuyuki 《Journal of Sol-Gel Science and Technology》1997,8(1-3):77-81
The structure of iron oxide was controlled by regulating the hydrolytic polymerization of aquo iron complexes with organic
polydentate ligands such as diols. Iron oxides were prepared by calcining the precursor polymers obtained from iron nitrate
nonahydrate and diols. When the diols were 1,2-pentanediol, 1,2-hexanediol and 1,2-octanediol, α-Fe2O3 with corundum structure appeared exclusively or as the main crystalline phase, in spite of the amount of diol used and the
calcination temperature. In the case of 1,2-decanediol and 1,2-dodecanediol, when five moles of the diols were used to one
mole of iron nitrate and the calcination temperatures were below 400°C, ψ-Fe2O3 with spinel structure appeared as the main phase and, when less than five moles of the diols were used, α-Fe2O3 appeared exclusively or as the main phase, irrespective of the calcination temperature. This tendency was also observed in
thin films. Thus, a transparent magnetic film composed of γ-Fe2O3 could be prepared by applying a benzene solution of the iron polymer, obtained with 5 equivalents of 1,2-decanediol, on quartz
and calcining the gel film at 350°C. 相似文献
145.
Complex films of crosslinked poly(methylsiloxane-co-ethylene oxide) and lithium perchlorate were prepared. These solid state polymeric electrolytes show a markedly higher ionic conductivity, and excellent flexibility. The ionic conductivity of the network films closed to 10~(-5) Scm~(-1) at room temperature. The effects of Li~+ content, species and contents of crosslinking agents, molecular weight of poly(ethylene oxide) and temperature on the ionic conductivity of the network films were also investigated. 相似文献
146.
A thin film of manganese hexacyanoferrate (MnHCF) was electrochemically formed on a glassy carbon (GC) electrode to prepare a chemically modified electrode (CME). The mechanism of film formation of MnHCF and its growth process were investigated in detail by cyclic voltammetry. The results show that the stoichiometric composition of MnHCF is Mn^ⅢFe^Ⅲ(CN)6, an analogue of prussian yellow. There exist three clear-cut stages in the whole modification process and the last stage is indispensable to the fabrication of homogenized, stable MnHCF film and must last for an appropriate time. The surface morphology of MnHCF/GC electrode was characterized by scanning electron microscopy (SEM), which further verified the effective deposition of MnHCF film on GC. The kinetic constants of MnHCF/GC electrode process were also evaluated. The resulting MnHCF film modified electrode presented good stability and high electrocatalytic activity toward the oxidation of H2O2, indicating that MnHCF film possesses function of catalase and can be expected for analytical purposes. 相似文献
147.
超高感彩卷乳剂微晶体电镜研究 总被引:1,自引:0,他引:1
应用物理和化学相结合的方法,将超高感彩卷分层剥离,离心沉降,水洗除胶,电镜观测各层乳剂的微晶体结构。揭示了超高感彩卷各乳剂层的结构情况,披露了超高感彩剂制造技术。 相似文献
148.
Regenerated cellulose films with water-resistance were obtained by an improved method ofpreparing cellulose cuoxam solution from pulps of agricultural wastes (linters, wheat straw, reedand Bamao). Experimental results showed that the mechanical properties of both the dry. and wetfilms were excellent. Data from IR, SEM and tensile strength measurements implied that thesignificant improvement of water-resistance of the films was due to the cohesion between the thinTung oil covers with hydrophobicity and the regenerated cellulose films. The films werecompletely biodegraded after being buried in soil for 100 days. The transmittance of the filmsderived from linter and reed in visible band range were 80-90%. 相似文献
149.
Metal (M) oxide (M: Ir, Os, Pd, Pt, Rh, Ru) together with MaO2 and MnO2 alone, were coated on SnO2 films and the anode behavior was examined in 1.0 N H2SO4, 1.0 N NaOH and 1.0, N NaCl aqueous solutions at 25°. The results are compared with those of DSA and of metallic Pt. 相似文献
150.
The nano-ZnFe2O4/TiO2 films possess the functions of desulfurization and degradation for organic pollutants. The sols of ZnFe2O4/TiO2 were prepared by sol-gel method and coated on glass and porous ceramic by vertical coating and dipping-lift processes, respectively, and the samples were obtained after drying and sintering. The composition, appearance, absorption spectrum of the films, and the influence of the film on porous ceramic performances were analyzed using SEM, AFM, UV-Vis spectrometer, and mercury porosimeter, respectively, to determine the operation parameters of the multifunction porous ceramic elements for gas-purification. 相似文献