全文获取类型
收费全文 | 118708篇 |
免费 | 14632篇 |
国内免费 | 11684篇 |
专业分类
化学 | 42208篇 |
晶体学 | 1404篇 |
力学 | 14041篇 |
综合类 | 1927篇 |
数学 | 38724篇 |
物理学 | 46720篇 |
出版年
2024年 | 122篇 |
2023年 | 1069篇 |
2022年 | 1880篇 |
2021年 | 3064篇 |
2020年 | 3138篇 |
2019年 | 2967篇 |
2018年 | 2765篇 |
2017年 | 3587篇 |
2016年 | 4219篇 |
2015年 | 3551篇 |
2014年 | 5709篇 |
2013年 | 8527篇 |
2012年 | 6738篇 |
2011年 | 7741篇 |
2010年 | 6757篇 |
2009年 | 7971篇 |
2008年 | 7993篇 |
2007年 | 8111篇 |
2006年 | 7238篇 |
2005年 | 5949篇 |
2004年 | 5309篇 |
2003年 | 4820篇 |
2002年 | 4275篇 |
2001年 | 3765篇 |
2000年 | 3178篇 |
1999年 | 2663篇 |
1998年 | 2549篇 |
1997年 | 2161篇 |
1996年 | 1936篇 |
1995年 | 1677篇 |
1994年 | 1590篇 |
1993年 | 1390篇 |
1992年 | 1327篇 |
1991年 | 981篇 |
1990年 | 836篇 |
1989年 | 687篇 |
1988年 | 656篇 |
1987年 | 526篇 |
1986年 | 449篇 |
1985年 | 590篇 |
1984年 | 481篇 |
1983年 | 264篇 |
1982年 | 471篇 |
1981年 | 619篇 |
1980年 | 518篇 |
1979年 | 554篇 |
1978年 | 450篇 |
1977年 | 352篇 |
1976年 | 288篇 |
1973年 | 197篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
51.
Haruki Inoue Dr. Shin-ichi Naya Atsunobu Akita Dr. Hisashi Sugime Prof. Dr. Hiroaki Tada 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(46):e202201653
Gold nanoparticles with different mean sizes were formed on antimony-doped tin oxide nanocrystals by the temperature-varied deposition-precipitation method (Au/ATO NCs). Au/ATO NCs possess strong absorption in the near-infrared region due to Drude excitation in addition to the localized surface plasmon resonance (LSPR) of AuNPs around 530 nm. Au/ATO NCs show thermally activated catalytic activity for the oxidation of cinnamyl alcohol to cinnamaldehyde by hydrogen peroxide. The catalytic activity increases with a decrease in the mean Au particle size (dAu) at 5.3 nm≤dAu≤8.2 nm. Light irradiation (λex >660 nm, ∼0.5 sun) of Au/ATO NCs increases the rate of reaction by more than twice with ∼95 % selectivity. Kinetic analyses indicated that the striking enhancement of the reaction stems from the rise in the temperature near the catalyst surface of ∼30 K due to the photothermal effect of the ATO NCs. 相似文献
52.
53.
以轻烧白云石粉、氯化铵和二氧化碳为原料,在未使用晶型控制剂的情况下,通过蒸氨-沉钙过程制备出了似立方体状碳酸钙。研究了反应温度、溶液中钙离子浓度、通气速率、搅拌速度以及陈化时间对碳酸钙中方解石相含量以及晶体形貌的影响,并探索了沉钙反应的晶型控制机理。结果表明,在反应温度40 ℃、钙离子浓度0.05 mol/L、通碳速率100 mL/min、搅拌速度400 r/min和陈化时间2 h的条件下,制备出形貌规整、粒径分布均匀的似立方体状碳酸钙,平均粒径为5~10 μm。该研究为提升白云石的使用价值、生产高附加价值的碳酸钙产品,以及提高白云石资源的利用率提供理论基础。 相似文献
55.
本研究采用水热法,以柠檬酸为螯合剂,通过控制n(Sn4+)/n(Sn2+)的数值,合成了由具有丰富氧空位的SnO2纳米晶体组装成的微球。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、傅里叶红外光谱(FT-IR)、X射线光电子能谱(XPS)及UV-Vis漫反射光谱对SnO2纳米微球进行表征分析,结果表明:在酸性水热条件和柠檬酸的螯合作用下,二氧化锡纳米晶体聚集形成微球;在Sn4+/Sn2+摩尔比例为3:7时,其微球尺寸最小,整体分散性较好;同时适量二价锡离子的掺杂使得该样品氧空位浓度达到最佳,氧空位的存在将使得样品光吸收范围拓展至可见光,因而该样品显示出较强的可见光催化效率,在8 min内完全降解甲基橙。 相似文献
56.
Effect of external electric field on the terahertz transmission characteristics of electrolyte solutions 下载免费PDF全文
Jia-Hui Wang 《中国物理 B》2021,30(11):110204-110204
We fabricated a microfluidic chip with simple structure and good sealing performance, and studied the influence of the electric field on THz absorption intensity of liquid samples treated at different times by using THz time domain spectroscopy system. The tested liquids were deionised water and CuSO4, CuCl2, NaHCO3, Na2CO3 and NaCl solutions. The transmission intensity of the THz wave increases as the standing time of the electrolyte solution in the electric field increases. The applied electric field alters the dipole moment of water molecules in the electrolyte solution, which affects the vibration and rotation of the whole water molecules, breaks the hydrogen bonds in the water, increases the number of single water molecules and leads to the enhancement of the THz transmission spectrum. 相似文献
57.
58.
Piezoelectric materials have received much attention due to their great potential in environmental remediation by utilizing vibrational energy. In this paper, a novel piezoelectric catalyst, CoOx nanoparticles anchored BiFeO3 nanodisk composite, was intentionally synthesized via a photodeposition method and applied in piezocatalytic degradation of rhodamine B (RhB) under ultrasonic vibration. The as-synthesized CoOx/BiFeO3 composite presents high piezocatalytic efficiency and stability. The RhB degradation rate is determined to be 1.29 h−1, which is 2.38 folds higher than that of pure BiFeO3. Via optimizing the reaction conditions, the piezocatalytic degradation rate of the CoOx/BiFeO3 can be further increased to 3.20 h−1. A thorough characterization was implemented to investigate the structure, piezoelectric property, and charge separation efficiency of the CoOx/BiFeO3 to reveal the nature behind the high piezocatalytic activity. It is found that the CoOx nanoparticles are tightly adhered and uniformly dispersed on the surface of the BiFeO3 nanodisks. Strong interaction between CoOx and BiFeO3 triggers the formation of a heterojunction structure, which further induces the migration of the piezoinduced holes on the BiFeO3 to CoOx nanoparticles. The recombination of electron-hole pairs is retarded, thereby increasing the piezocatalytic performance greatly. This work may offer a new paradigm for the design of high-efficiency piezoelectric catalysts. 相似文献
59.
60.