全文获取类型
收费全文 | 880篇 |
免费 | 71篇 |
国内免费 | 108篇 |
专业分类
化学 | 518篇 |
晶体学 | 8篇 |
力学 | 104篇 |
数学 | 72篇 |
物理学 | 357篇 |
出版年
2023年 | 60篇 |
2022年 | 27篇 |
2021年 | 37篇 |
2020年 | 56篇 |
2019年 | 40篇 |
2018年 | 25篇 |
2017年 | 52篇 |
2016年 | 36篇 |
2015年 | 53篇 |
2014年 | 60篇 |
2013年 | 53篇 |
2012年 | 74篇 |
2011年 | 43篇 |
2010年 | 36篇 |
2009年 | 50篇 |
2008年 | 25篇 |
2007年 | 47篇 |
2006年 | 42篇 |
2005年 | 25篇 |
2004年 | 14篇 |
2003年 | 23篇 |
2002年 | 18篇 |
2001年 | 26篇 |
2000年 | 15篇 |
1999年 | 17篇 |
1998年 | 19篇 |
1997年 | 13篇 |
1996年 | 6篇 |
1995年 | 8篇 |
1994年 | 7篇 |
1993年 | 11篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1982年 | 2篇 |
1976年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有1059条查询结果,搜索用时 31 毫秒
61.
MgO/Al_2O_3吸附剂对CO_2动态吸附性能的研究 总被引:3,自引:1,他引:2
以γ-Al2O3为载体,采用等体积浸渍法制取MgO/Al2O3吸附剂,利用BET、XRD等表征手段对吸附剂进行表征;并通过固定床测量穿透曲线的方法研究其对CO2动态吸附性能的影响,考察了MgO负载量、吸附温度、气体流量等因素对吸附剂吸附CO2性能的影响,同时还通过多次吸脱附实验考察MgO/Al2O3吸附剂的稳定性和再生能力。结果表明,MgO负载量为10%的吸附剂,吸附温度在50℃左右,流量为45 mL/min动态吸附量最大;经数次循环后材料的结构性质和吸附性能未见明显变化,可再生性能比较优异,是一种潜在的可工业化应用的CO2吸附剂。 相似文献
62.
High solid content latex: Preparation methods and application 总被引:2,自引:0,他引:2
One of the major challenges in emulsion polymerization over the past two decades was how to increase the solid content of latex products. In contrast to the conventional latex, high solid content (HSC) latex has a large volume fraction of dispersed phase, even larger than 70% in weight. Conventional emulsion polymerization, miniemulsion polymerization, self-emulsification polymerization and concentrated emulsion polymerization were all used to prepare HSC latexes, and many good results have been reported in recent years. Meanwhile, many applications of HSC latexes have also been developed. The present review summarized the progresses in the past few years mainly on the preparation methods and application of HSC latexes. Finally, some research directions as well as prospects were also proposed. 相似文献
63.
Matrix solid-phase dispersion (MSPD) with alumina N as adsorbent has been used for extraction of para red, Sudan 1, Sudan 2, Sudan 3, and Sudan 4 dyes from egg yolk. The extracts were analyzed by ultra-performance liquid chromatography–tandem mass spectrometry (UPLC–MS–MS). Mean recovery for the five dyes ranged from 63.2 to 98.6%, with CV 0.55–10.00%. One sample was confirmed to contain 0.3 mg kg?1 Sudan 4. 相似文献
64.
65.
Yi Liu Tao Zou Fen Wang Chang-Hui Li Lin Zheng Young Sun 《Physica B: Condensed Matter》2011,406(6-7):1263-1266
We report on exotic dielectric properties of composite materials consisting of traditional ferroelectric BaTiO3 and electronic ferroelectric LuFe2O4. The composites were synthesized by a simple ceramic processing method with properties that can be tailored by adjusting LuFe2O4 concentration. A percolative effect was observed at the volume fraction of ~0.26, which led to an abrupt increase in the dielectric permittivity. For composites with high LuFe2O4 fractions, a giant dielectric tunability was observed over a broad temperature interval, which is in strong contrast to traditional ferroelectrics. 相似文献
66.
A wave-coupling theory of linear electro-optic (EO) effect for ultrashort laser pulses has been developed. As one of its applications,
the linear EO effect of ultrashort Gaussian pulses propagating in LiNbO3 crystal is demonstrated, with the intensity lower than the damage threshold. It is found that the EO effect is sensitive
to both the azimuth angle and the polar angle of wave vector of light. And the larger the applied electric field, the shorter
the crystal used for optimization of EO coupling is. The numerical results show that, with the duration of input pulse changing
from 150 fs to 5 fs, the durations of output pulses are broadened due to the group-velocity dispersion, as well as the first-
and second-order refractive dispersion. In addition, when input pulse duration is larger than 20 fs, in contrast with zero
chirp, the output durations can be slightly compressed if a positive chirp input pulse is used. The validities of slowly varying
amplitude approximation and continuous wave approximation are also discussed. The influence of self-phase modulation and cross-phase
modulation on the EO effect is also discussed briefly. 相似文献
67.
近红外光谱法预测粗皮桉木材气干密度的影响因素分析 总被引:1,自引:0,他引:1
采用近红外光谱分析技术,对粗皮桉木材气干密度校正模型的影响因素进行比较研究.使用直接测量法测量了粗皮桉木材的气干密度,并用近红外光谱仪采集试样的近红外漫反射光谱,对不同切面、厚度、含水率和粗糙度的粗皮桉木材试样的原始光谱进行二阶导数预处理并选择一定光谱段建立回归模型.以50~140个试样作为校正集建立木材气干密度的偏最... 相似文献
68.
对我国华南地区六种棕榈藤的纤维和导管形态特征进行了观测,研究了应用近红外光谱分析技术预测棕榈藤纤维长度和导管长度的可行性.结果表明:六种棕榈藤的纤维平均长度在1229~1917μm,导管的平均长度在1035~2129μm;发现株榈藤纤维长度和导管长度模型的建立采用偏最小二乘法和完全交互验证法,在350~2454 nm谱... 相似文献
69.
选取具不同生长应力水平的人工林尾巨桉(Eucalyptus uroph ylla×E.grandis)正常木为研究对象,借助场发射环境扫描电子显微镜系统,结合以溴元素做标记的X射线能谱分析技术,分析了尾巨桉细胞壁微区木质素沉积与生长应力的关系.研究结果表明,木纤维细胞壁各微区间木质素含量的大小关系与生长应力高低无关,其... 相似文献
70.
Guangmei Xia Linghao He Qiaoling Zhao Weihong Chen Rui Song Zhi Ma 《Colloid and polymer science》2012,290(18):1943-1947
Hydrogen bonds exist in many polymer systems and play a large role in the physical and chemical properties. In this study, nylon-6, which consists of repeated amide groups and contains large number of hydrogen bonds, is chosen as an example. Meanwhile, the oxidized unzipped MWCNTs (μCNTs) with oxygenated species such as carboxyl and hydroxyl groups are used as mediator to regulate the crystallization process of nylon-6 thin films. In-site experimental techniques, including Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy, and polarized optical microscopy were utilized to get more direct insights on the crystallization mechanism of nylon-6 and μCNTs systems. 相似文献