全文获取类型
收费全文 | 6562篇 |
免费 | 1170篇 |
国内免费 | 425篇 |
专业分类
化学 | 3649篇 |
晶体学 | 280篇 |
力学 | 151篇 |
综合类 | 30篇 |
数学 | 39篇 |
物理学 | 4008篇 |
出版年
2024年 | 4篇 |
2023年 | 23篇 |
2022年 | 44篇 |
2021年 | 81篇 |
2020年 | 139篇 |
2019年 | 113篇 |
2018年 | 120篇 |
2017年 | 174篇 |
2016年 | 270篇 |
2015年 | 243篇 |
2014年 | 281篇 |
2013年 | 530篇 |
2012年 | 362篇 |
2011年 | 560篇 |
2010年 | 481篇 |
2009年 | 526篇 |
2008年 | 503篇 |
2007年 | 524篇 |
2006年 | 571篇 |
2005年 | 416篇 |
2004年 | 339篇 |
2003年 | 330篇 |
2002年 | 303篇 |
2001年 | 190篇 |
2000年 | 171篇 |
1999年 | 151篇 |
1998年 | 122篇 |
1997年 | 113篇 |
1996年 | 67篇 |
1995年 | 81篇 |
1994年 | 86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 | 8篇 |
1984年 | 9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8157条查询结果,搜索用时 46 毫秒
101.
R. Cristescu G. Dorcioman E. Axente A. Moldovan T. Kocourek M. Albulescu D. Mihaiescu D.B. Chrisey 《Applied Surface Science》2006,252(13):4647-4651
We report the first successful deposition of triacetate-pullulan polysaccharide thin films by matrix assisted pulsed laser evaporation. We used a KrF* excimer laser source (λ = 248 nm, τ ≈ 20 ns) operated at a repetition rate of 10 Hz. We demonstrated by FTIR that our thin films are composed of triacetate-pullulan maintaining its chemical structure and functionality. The dependence on incident laser fluence of the induced surface morphology is analysed. 相似文献
102.
有机薄膜电致发光器件失效过程的动态观测及分析 总被引:4,自引:0,他引:4
对有机薄膜电致发光器件失效的全过程进行了显微动态观察,发现器件工作时,有机层/金属界面形成的气泡逐渐变大变多,最终导致器件完全失效,气泡不仅含有水汽,还存在大量有机气体。 相似文献
103.
104.
105.
P.M.?Kosaka Y.?Kawano M.C.?Salvadori D.F.S.?PetriEmail author 《Cellulose (London, England)》2005,12(4):351-359
The adsorption of cellulose acetate (CA), cellulose acetate propionate (CAP) and cellulose acetate butyrate (CAB) from solutions
prepared in acetone onto silicon wafers led to ultrathin films, which were characterized by ellipsometry, atomic force microscopy
(AFM) and contact angle measurements. The polysaccharides films were characterized in the air just after their formation and
after annealing at temperatures higher than their glass transition temperature or melt temperature. The films thickness close
to 2 nm and surface roughness did not vary significantly upon annealing. AFM images revealed the presence of small clumps
dispersed on a homogeneous layer, which covered completely the Si wafers. Such topographic details were also observed after
annealing. However, upon annealing the films surfaces changed from hydrophilic to hydrophobic, evidencing molecular re-orientation
at the solid–air interface. The adhesion of bovine serum albumin (BSA) and lipase onto the cellulose esters films was quantified
in order to evaluate the possibility of applying such films as selective support for biomolecules. 相似文献
106.
半导体TiO2光催化材料对环境中各种污染物的明显去除效果已引起人们的广泛关注犤1~6犦。在普通钠钙玻璃表面涂制高光催化活性的TiO2纳米薄膜,制成环保建筑材料,不仅可以自洁玻璃表面,而且可以用于净化空气、处理废水等。但由于在热处理过程中玻璃基体内的Na+离子扩散到薄膜表面,形成光生电子和空穴的复合中心,使TiO2纳米薄膜的光催化活性大大降低犤7~10犦。为了减少玻璃中Na+离子对TiO2薄膜光催化活性的有害影响,Paz等犤8犦研究了将钠钙玻璃浸入酸溶液中,使玻璃表面的钠离子被酸中的氢离子置换出来;在玻璃表面形成SiO2凝胶层,以便阻… 相似文献
107.
Ronny Kleinhempel Gunar Kaune Matthias Herrmann Hartmut Kupfer Walter Hoyer Frank Richter 《Mikrochimica acta》2006,156(1-2):61-67
Indium tin oxide (ITO) thin films were deposited by mid frequency pulsed dual magnetron sputtering using a metallic alloy
target with 10 wt.% tin in an atmosphere of argon and oxygen. The aim of the work was to study the interdependence of structural,
electrical and optical properties of ITO films deposited in the reactive and transition target mode, respectively. The deposition
rate in the transition mode exceeds the deposition rate in the reactive mode by a factor of six, a maximum value of 100 nm·m min−1 could be achieved. This corresponds to a static deposition rate of 200 nm min−1. The lowest electrical resistivity of 1.1·10−3 Ω cm was measured at samples deposited in the high oxygen flow range in the transition mode. The samples show a good transparency
in the visible range corresponding to extinction coefficients being below 10−2. X-ray diffraction was used to characterise crystalline structure as well as film stress. ITO films prepared in the transition
mode show a slightly preferred orientation in (211) direction, whereas films deposited in the reactive mode are strongly (222)
oriented. Compared to undoped In2O3 all samples have an enlarged lattice. The lattice strain perpendicular to the surface is about 0.8% and 2.0% for films grown
in the transition and the reactive mode, respectively. Deposition in the transition mode introduces a biaxial film stress
in the range of −300 MPa, while stress in reactive mode samples is −1500 MPa. 相似文献
108.
The effect of pressure during thermal plasma chemical vapor deposition of diamond films has been investigated for a pressure range from 100 to 760 Torr. The maximum growth rate in our experiments occurs at 270 Torr for substrate temperatures around 1000°C. The existence of an optimum pressure for diamond deposition may he related to the balance between generation and recombination of atomic hydrogen and carbon-containing active species in front of the substrate. To estimate the concentrations of atomic hydrogen and methyl radicals under thermal plasma conditions, calculations based on thermodynamic equilibrium have been performed. This approximate evaluation provides useful guidelines because rapid diffusion results in a near frozen chemistry within the boundary layer. The effect of substrate pretreatment on diamond deposition depends on the type of substrate used. Two growth modes have been observed-layer growth and island growth of diamond crystals on various substrates. Screw dislocations have been observed in diamond deposition in thermal plasmas, and defects such as secondary nucleations are more concentrated along (III) directions than along (100) directions. 相似文献
109.
The thinning of foam films from aqueous solutions of an ABA triblock copolymer of polyethylene oxide and polypropylene oxide (average molecular weight 14,000 g/mol) is studied experimentally. The dependence of the surface forces on film thickness is obtained by the dynamic method of Scheludko and Exerowa.The total surface force measured in foam films (radius 60–70 m) from 10–5 M (0.014 wt%) polymer solution with 0.1 M NaCl is positive at thicknesses from about 800 down to 460 . The electrostatic repulsion is negligible while the contribution of van der Waals attraction is small (within 15%). Therefore a positive surface force component predominates. Most probably it arises from steric interactions between the hydrophilic polyethylene oxide tails of the polymer. The dynamic method appears to be a suitable technique for exploring the stabilization of foam films from ABA copolymers. 相似文献
110.
Titanium dioxide (TiO2) thin films have been prepared on indium doped tin oxide (ITO) glass by sol-gel dip-coating method. Properties of the films
were determined as a function of heat-treatment by X-ray diffraction, scanning electron microscopy and photoelectrochemical
tests. The films heat-treated at higher temperatures show better crystallinity and photoresponse. The microscopic structure
on the film after heat-treatment is attributed to the incorporation of organic polymer into the precursor solution. The performance
of the electrodes treated at different temperature on photoelectrocatalytic degradation of methyl orange was investigated.
The effect of applied potential and the ability of the electrode to be repeatedly used in photoelectrocatalytic degradation
were also evaluated. 相似文献