全文获取类型
收费全文 | 6384篇 |
免费 | 1150篇 |
国内免费 | 427篇 |
专业分类
化学 | 3644篇 |
晶体学 | 278篇 |
力学 | 154篇 |
综合类 | 31篇 |
数学 | 40篇 |
物理学 | 3814篇 |
出版年
2024年 | 4篇 |
2023年 | 20篇 |
2022年 | 48篇 |
2021年 | 73篇 |
2020年 | 134篇 |
2019年 | 110篇 |
2018年 | 117篇 |
2017年 | 171篇 |
2016年 | 269篇 |
2015年 | 241篇 |
2014年 | 280篇 |
2013年 | 508篇 |
2012年 | 350篇 |
2011年 | 547篇 |
2010年 | 462篇 |
2009年 | 513篇 |
2008年 | 491篇 |
2007年 | 519篇 |
2006年 | 545篇 |
2005年 | 393篇 |
2004年 | 323篇 |
2003年 | 324篇 |
2002年 | 306篇 |
2001年 | 187篇 |
2000年 | 169篇 |
1999年 | 151篇 |
1998年 | 121篇 |
1997年 | 113篇 |
1996年 | 67篇 |
1995年 | 81篇 |
1994年 | 87篇 |
1993年 | 41篇 |
1992年 | 54篇 |
1991年 | 23篇 |
1990年 | 15篇 |
1989年 | 14篇 |
1988年 | 26篇 |
1987年 | 14篇 |
1986年 | 6篇 |
1985年 | 7篇 |
1984年 | 8篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1973年 | 3篇 |
排序方式: 共有7961条查询结果,搜索用时 687 毫秒
131.
Sandip Halder Theodor Schneller Rainer Waser Florian Thomas 《Journal of Sol-Gel Science and Technology》2007,41(3):203-207
Nickel thin films have been sputtered on standard Si/SiO2 substrates with TiO2 as an adhesive layer. The thermal stability of these substrates was analyzed. SEM images show an increase in grain size with
annealing temperature. They were found to be stable till 800°C, beyond which the nickel layer disintegrated. These substrates
were used for deposition of BaTiO3 and (Ba,Sr)TiO3 dielectric thin films under a reducing atmosphere. The dielectric thin films were processed with various pyrolysis and annealing
temperatures in order to optimize the dielectric properties. Increased pyrolysis temperatures showed an increase in the grain
size. Results on these nickelised substrates were finally compared with dielectric films deposited on platinized silicon substrates
under identical conditions but crystallized in an oxygen atmosphere. 相似文献
132.
Sumio Sakka 《Journal of Sol-Gel Science and Technology》1994,2(1-3):451-455
The present state of our knowledge on sol-gel coating films has been reviewed. A qualitative discussion is made on the limit of the film thickness which can be achieved in the sol-gel method and the factors affecting the film thickness. Considering that properties of the film are intimately related to the microstructure, types of microstructures accomplished by the sol-gel coating are introduced with examples. 相似文献
133.
纤维素/甲壳素共混膜的结构表征与抗凝血性能 总被引:20,自引:0,他引:20
以 6wt %NaOH 4wt%尿素为纤维素的新溶剂 ,采用溶液共混法制备出纤维素 甲壳素共混膜 ,为甲壳素在碱性溶液中制膜提供了新的方法 .红外光谱、X 射线衍射、扫描电镜和力学性能、抗凝血性能测试结果表明 ,共混膜中甲壳素含量低于 4 0wt%时 ,纤维素与甲壳素分子间具有良好的相容性 ;在纤维素中引入适量甲壳素可提高共混膜的抗张强度 ,共混膜的干、湿态抗张强度在甲壳素含量 10wt%时最大 ,其值分别为 89 1MPa和 4 3 7MPa ,比纯态纤维素膜的干、湿态抗张强度分别提高了 6 7%和 11 5 % ;甲壳素的引入可明显降低血小板在共混膜表面的粘附、凝聚与变性 ,增大共混膜的抗凝血参数 ,甲壳素含量达到 5 0wt%时 ,该共混膜具有良好的抗凝血性能 相似文献
134.
135.
Electropolymerized thin films of Co(III/II)- and Zn(II)-4,9,16,23-tetraaminophthalocyanine, immersed in solutions of relatively high pH, have been studied electro- and spectroelectrochemically. Cyclic voltammetry and chronocoulometry were used to characterize films deposited on glassy carbon electrodes. Spectroelectrochemistry and ellipsometry measurements were performed on indium tin oxide (ITO) surfaces coated with the zinc and cobalt complexes and correlated to the electrochemical information collected using glassy carbon electrodes. Studies at high pH are motivated by the efficient increase in luminol chemiluminescence at high OH− concentration, and by potential application in luminescence sensors. Although the films are not removed, some structural changes occur when they are exposed to solutions of high pH. In addition, an estimation of the number of monolayers has also been calculated. The atomic diameters of cobalt and zinc are very close in value, but the estimated number of monolayers, based on cyclic voltammetric data, for a given number of electropolymerization cycles is approximately four-fold higher in the zinc-based film. This would correspond to three-fold thicker films when zinc is the central metal ion. Ellipsometry measurements have been correlated with cyclic voltammetric data to confirm that film thickness varies among the different complexes, even though the conditions of electropolymerization are the same. 相似文献
136.
Composite materials were processed by casting a mixture of aqueous suspensions of latex and microfibrils. These microfibrils, or whiskers, are extracted from a sea animal and are monocrystals of cellulose, with an aspect ratio around 100 and an average diameter of 20 nm. It has been found that the mechanical properties (shear modulus) are increased by more than two orders of magnitude in the rubbery state of the polymeric matrix, when the whisker content was 6% (w/w). This very large effect is discussed on the basis of different types of mechanical models and it is concluded that these whiskers form a rigid network, probably linked by hydrogen bonds. The formation of this network is assumed to be governed by a percolation mechanism. 相似文献
137.
《Electroanalysis》2004,16(9):741-747
This work reports a technique for the rapid electrochemical detection of propranolol and metoprolol in pharmaceutical preparations using stabilized lipid films. Microporous filters composed of glass fibers (nominal pore sizes 0.7 and 1.0 μm) were used as supports for the formation and stabilization of these devices. The lipid film is formed on the filter by polymerization prior to its use. This stabilized after storage in air. Lipid films composed of phosphatidylcholine were used for the detection of propranolol and metoprolol in pharmaceutical preparations. The stabilized lipid membranes provided artificial ion gating events in the form of transient signals within about 60 and 34 s after exposure of the membranes to propranolol and metoprolol, respectively. The magnitude of the transient current signal was related to the concentration of propranolol and metoprolol in bulk solution in the micromolar range. The mechanism of signal generation was investigated by differential scanning calorimetric studies. These studies revealed that the adsorption of the drug is through the hydrophobic aryl terminal of the compound, whereas the hydrophilic groups were directed towards the electrolyte solution. This adsorption caused a rapid alteration of the electrochemical double layer of the lipid film (i.e., capacitance changes) that resulted in the transient ion current signal. The present technique was used for the rapid detection of propranolol and metoprolol in pharmaceutical preparations and can function for repetitive uses after storage in air. Future research is targeted to the determination of these chemicals in human biofluids such as urine of athletes. 相似文献
138.
In this work, Ba(NO3)2 crystals with single crystal face were induced by using the the method of bio-mimetic mineralization and double LB films of behenic acid (BA) as the template. The crystals were characterized by Scanning Electron Microscope (SEM) and X-Ray Diffraction (XRD). The crystals were observed in regular square shape with uniform size about 5~8 μm by SEM, and they were found by XRD to grow along the (111) plane. From these experiments, we can conclude that the good selection of the (111) crystal face of Ba(NO3)2 is due to the electrostatic interactions , the match between this crystal face and the definite lattice structure of the LB films. 相似文献
139.
1991年Decher等将带相反电荷的聚电解质 ,于水溶液中交替沉积在片基上 ,制备了多层超薄膜[1] ,这种制膜方法现称为静电自组装 .它操作简单 ,无需专用设备 ;一般在水体系进行 ,对环境友好 ;静电力比范德华力强 ,使它比LB膜稳定 ,所以近年来有很大发展[2 ] .现在自组装成膜驱动力已从静电力扩展到氢键力、电荷转移相互作用、疏水相互作用等 ,用于组装的组分也从聚电解质扩展到多官能团小分子、胶体粒子、无机纳米颗粒 ,DNA、蛋白质等生物大分子等[3~ 11] .虽然自组装膜比LB膜稳定 ,但它也不耐极性溶剂、电解质水溶液等侵蚀 .如… 相似文献
140.
Kiyoshi Ozawa Yoshio Sakka Muneyuki Amano 《Journal of Sol-Gel Science and Technology》2000,19(1-3):595-598
Cubic antimonic acid (Sb2O5·nH2O) films were successfully prepared on stainless steel and Si(100) substrates by electrophoretic deposition (EPD) using two types of sols. The sols were prepared by reacting an H2O2 aqueous solution with Sb(O-i-C3H7)3 or metallic Sb powder. The resulting films were found to consist of fine particles of cubic Sb2O5·nH2O single crystals with uniform particle sizes of 30 nm and 150 nm. The weight of the Sb2O5·nH2O deposit on the anode Si(100) substrate by EPD increased linearly with the current density in the range of 0–0.67 mA cm–2, when the sol pH was over 7. The proton conductivity of the polycrystalline Sb2O5·nH2O discs, formed from the two types of sols, was evaluated by an ac impedance method at room temperature under controlled levels of relative humidity. 相似文献