全文获取类型
收费全文 | 267篇 |
免费 | 1篇 |
专业分类
化学 | 132篇 |
晶体学 | 2篇 |
力学 | 19篇 |
数学 | 21篇 |
物理学 | 94篇 |
出版年
2023年 | 2篇 |
2021年 | 3篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 7篇 |
2013年 | 5篇 |
2012年 | 8篇 |
2011年 | 16篇 |
2010年 | 17篇 |
2009年 | 7篇 |
2008年 | 12篇 |
2007年 | 17篇 |
2006年 | 16篇 |
2005年 | 21篇 |
2004年 | 7篇 |
2003年 | 16篇 |
2002年 | 9篇 |
2001年 | 7篇 |
2000年 | 6篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1986年 | 1篇 |
1985年 | 7篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1969年 | 3篇 |
1968年 | 2篇 |
排序方式: 共有268条查询结果,搜索用时 154 毫秒
31.
A new chemical vapor deposition (CVD) method, called ionization CVD, was developed, to produce non-agglomerated nanoparticles in which reactant gases are charged. A sonic-jet corona discharger was used as an ionizer in the developed nanoparticle generator. For a tetraethylorthosilicate (TEOS)/O2 chemical system, SiO2 nanoparticles were prepared. All particles formed by the ionization CVD were charged unipolarly. SEM micrographs of particles showed that the repulsive Coulombic force between charged particles reduces their coagulation rate and produces non-agglomerated nanoparticles that have a relatively high number concentration and small size. An external field was used to collect the charged particles onto Si wafers. These collected samples indicated that the deposition of charged particles could be controlled by the external electric field. Particle concentration measurement with a condensation nucleus counter at various TEOS concentrations suggested the particle formation mechanism in the ionization CVD was an ion-induced nucleation. 相似文献
32.
Nobuki Kashihara Heru Setyawan Manabu Shimada Yutaka Hayashi Chan Soo Kim Kikuo Okuyama Sugeng Winardi 《Journal of nanoparticle research》2006,8(3-4):395-403
Sine-wave modulated rf plasma has been used to control particle generation and growth in a plasma-enhanced chemical vapor deposition of silicon dioxide thin films using TEOS/O2. The density and the size of particles generated in the plasma are greatly reduced when the plasma is modulated with sine-wave modulation at low modulation frequency (<1000 Hz). In addition, particle contamination on the films is significantly reduced also for nanoparticles, and the film growth rates at the range of modulation frequencies where particle generation are greatly reduced do not decrease appreciably. Compared to its counterpart pulse-wave modulation plasma, the sine-wave modulation plasma has demonstrated a better performance in terms of reduction of particle generation and film contamination, and of film growth rate. Thus, the sine-wave modulation plasma has shown as a promising method to be applied in the production of thin film with a high deposition rate and a low particle contamination. 相似文献
33.
Field desorption mass spectra of underivatized oligoglycosides of spirostanol and its congeners and of hederagenin revealed the molecular weight and structural information. The basic predominance of the formation of stable ions of highly polar natural products (with 5–17 free OH functions) is clearly demonstrated. After the extraction and purification procedure from plant material the samples contained inorganic salts in concentrations between 0.01 and 0.1%. These salt impurities, mostly alkali halides, strongly promoted the attachment of alkali cations to the intact molecules and their fragments. The ions produced gave analytical information not only for the confirmation of the molecular weight but also for the identity of the aglycone and, to some extent, for the sequence of the sugars in the oligoglycosides. All spectra were recorded on photoplates at a resolution of better than 15000 and enabled the evaluation of the elemental composition of the ions generated. The drawbacks and merits of integrating ion recording using the photoplate for FD investigations of highly polar substances are discussed. 相似文献
34.
35.
2-Mercaptobenzothiazole (MBT) loaded on glass beads with the aid of collodion was prepared and used for selective preconcentration of μg l?1 levels of copper(II) and lead from aqueous solutions. Copper and lead were quantitatively retained on the loaded beads from solutions of pH 5.0–6.0 and >5.0, respectively, while cadmium(II) and zinc(II) were retained at ? pH 6.0 and 7.0, respectively. The retention capacity of the loaded beads was ca. 108 μg Cu g?1 (1.7 μmol g?1) at pH 5.5 for beads of 0.3–0.4 mm diameter. The mole ratios of MBT to copper(II) and lead(II) were ca. 10 and 45, respectively, regardless of the amount of MBT loaded on the beads. Copper was completely retained on the column at a high flow rate (21.7 ml min? cm?2) and lead(II) at up to 12.7 ml min? cm?2. Cadmium(II) and zinc(II) were not retained quantitatively even at low flow rates (< 1.2 ml min?1 cm?2). Thus, selective preconcentration of copper and lead was achieved by passing the sample through the column at high flow rate at pH 6.5. The copper and lead retained on the column were complete eluted together with the collodion with 5 ml of MIBK by batch-mode elution, and determined directly by one-drop atomic absorption spectrometry. Copper(II) and lead(II) in several kinds of water were determined. 相似文献
36.
37.
Kikuo Oikawa 《应用有机金属化学》1988,2(4):391-393
This paper reviews the use of arsenic compounds in semiconductor manufacture and emphasizes the role of alkylated arsenic compounds. 相似文献
38.
Synthetic routes for the branching pentasaccharides 4 and 5 of glycoproteins are described in a regio- and stereo- controlled way. 相似文献
39.
Nickel(II) complexes of N3O2 donor macrocycles incorporating 17- to 19-membered macrocyclic rings have been prepared. Physical measurements ind 相似文献
40.
The resistivity of doped semiconductor Si: P in the intermidiate concentration range was measured in low temperature region down to 10 mK. In the lowest temperatures Mott's formula for the variable range hopping is shown to be not applicable and T-n-like temperature dependence of resistivity is confirmed. The Importance of the level correlation in the random system is discussed. 相似文献