全文获取类型
收费全文 | 25645篇 |
免费 | 3882篇 |
国内免费 | 2622篇 |
专业分类
化学 | 18749篇 |
晶体学 | 307篇 |
力学 | 1557篇 |
综合类 | 184篇 |
数学 | 2844篇 |
物理学 | 8508篇 |
出版年
2024年 | 59篇 |
2023年 | 484篇 |
2022年 | 660篇 |
2021年 | 802篇 |
2020年 | 940篇 |
2019年 | 930篇 |
2018年 | 744篇 |
2017年 | 739篇 |
2016年 | 1136篇 |
2015年 | 1070篇 |
2014年 | 1327篇 |
2013年 | 1745篇 |
2012年 | 2305篇 |
2011年 | 2352篇 |
2010年 | 1525篇 |
2009年 | 1417篇 |
2008年 | 1655篇 |
2007年 | 1528篇 |
2006年 | 1448篇 |
2005年 | 1228篇 |
2004年 | 891篇 |
2003年 | 745篇 |
2002年 | 761篇 |
2001年 | 641篇 |
2000年 | 509篇 |
1999年 | 513篇 |
1998年 | 432篇 |
1997年 | 378篇 |
1996年 | 405篇 |
1995年 | 369篇 |
1994年 | 320篇 |
1993年 | 249篇 |
1992年 | 248篇 |
1991年 | 237篇 |
1990年 | 194篇 |
1989年 | 156篇 |
1988年 | 124篇 |
1987年 | 102篇 |
1986年 | 115篇 |
1985年 | 91篇 |
1984年 | 77篇 |
1983年 | 53篇 |
1982年 | 52篇 |
1981年 | 45篇 |
1980年 | 36篇 |
1978年 | 34篇 |
1977年 | 33篇 |
1976年 | 30篇 |
1974年 | 26篇 |
1973年 | 29篇 |
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
211.
We reported controllable synthesis of ZnS nanocrystal-polymer transparent hybrids by using polymethylmethacrylate (PMMA) as
a polymer matrix. In a typical run, the appropriate amounts of zinc chloride (ZnCl2) and sodium sulfide (Na2S) in the presence of 2-mercaptoethanol (ME) as the organic ligand were well dispersed in H2O/dimethylformamide solution without any aggregation. In addition, the Mn-doped ZnS nanocrystals (NCs) were synthesized with
similar method. Then, ZnS-PMMA hybrids were obtained via free radical polymerization in situ by using ZnS NCs functionalized
with methacryloxypropyltrimethoxysilane (MPS). FT-IR characterization indicates the formation of robust bonding between ZnS
NCs and the organic ligand. The TEM images show that ZnS NCs are well dispersed in PMMA matrix, and particle size of as-prepared
ZnS NCs is about 2.6 nm, in agreement with the computing results of Brus’s model and Debye–Scherrer formula. The photoluminescence
measurements present that ZnS NCs, Mn-doped ZnS NCs, and ZnS/PMMA hybrid show good optical properties. 相似文献
212.
Stephen Z. D. Cheng 《Journal of Thermal Analysis and Calorimetry》1997,50(5-6):907-910
213.
214.
215.
216.
217.
Wen-Yin Chen Bo-Jung Chen Hung-Hsin Shih Chien-Hong Cheng 《Applied Surface Science》2006,252(19):6594-6596
A model organic light-emitting diodes (OLEDs) with structure of tris(8-hydroxyquinoline) aluminum (Alq3)/N,N′-diphenyl-N,N′-bis[1-naphthy-(1,1′-diphenyl)]-4,4′-diamine (NPB)/indium tin oxide (ITO)-coated glass was fabricated for diffusion study by ToF-SIMS. The results demonstrate that ToF-SIMS is capable of delineating the structure of multi-organic layers in OLEDs and providing specific molecular information to aid deciphering the diffusion phenomena. Upon heat treatment, the solidity or hardness of the device was reduced. Complicated chemical reaction might occur at the NPB/ITO interface and results in the formation of a buffer layer, which terminates the upper diffusion of ions from underlying ITO. 相似文献
218.
Songqing Zhao Yuzi Liu Shufang Wang Zhen Liu Ze Zhang Huibin Lu Bolin Cheng 《Applied Surface Science》2006,253(2):726-729
B-doped ZnO thin films have been fabricated on fused quartz substrates using boron-ZnO mosaic target by pulsed-laser deposition technique, and the mechanical properties have been studied by nanoindentation continuous stiffness measurement technique and transmission electron microscope (TEM). Nanoindentation measurement revealed that the hardness of B-doped ZnO films, 9.32 ± 0.90 to 12.10 ± 1.00 GPa, is much greater than that of undoped ZnO films and very close to that of traditional semiconductor Si. The mean transmittance (%) is larger than 81% in the visible range (380-780 nm) for all the films, and the Hall effect measurement showed that the carrier density is around 2 × 1020 cm−3 and the resistivity lower than 3 × 10−3 Ω cm. TEM characteristics show undoped thin films have more amorphous area between grains while the B-doped ZnO films have thin grain boundaries. We suggest that the grain boundaries act as the strain compensation sites and the decrease in thickness of grain boundaries enhances the hardness of the B-doped ZnO films. 相似文献
219.
The purpose of this paper is to report some experimental results with HfSiO films formed on silicon substrates by electron beam evaporation (EB-PVD) and annealed at different temperatures. The images of atomic force microscope (AFM) indicated that HfSiO film annealed at 900 °C was still amorphous, with a surface roughness of 0.173 nm. X-ray photoelectron spectroscopy (XPS) analysis revealed that the chemical composition of the film was (HfO2)3(SiO2) and Hf-Si-O bonds existed in the annealed film. Electrical measurements showed that the equivalent oxide thickness (EOT) was 4 nm, the dielectric constant was around 6, the breakdown voltage was 10 MV/cm, the fixed charge density was −1.2 × 1012 cm−2, and the leakage current was 0.4 μA/cm2 at the gate bias of 2 V for 6 nm HfSiO film. The annealing after deposition effectively reduced trapping density and the leakage current, and eliminated hysteresis in the C-V curves. Annealing also induced SiO2 growth at the interface. 相似文献
220.
Cheng Lu ZHANG Xiao Lei ZHU Ying Ge MA Li Wei ZOU 《中国化学快报》2006,17(2):163-164
12-Hydroxy-13-methylpodocarpa-9, 11, 13-trien-3-one 9 was isolated from the twigs ofCroton salutaris1. Many diterpenes exhibit significant bioactivities, such as antibac-terial and antitumour and 9 has a rare structure. In order to study the relationshipb… 相似文献