全文获取类型
收费全文 | 16411篇 |
免费 | 2916篇 |
国内免费 | 5446篇 |
专业分类
化学 | 12585篇 |
晶体学 | 578篇 |
力学 | 1213篇 |
综合类 | 699篇 |
数学 | 2226篇 |
物理学 | 7472篇 |
出版年
2024年 | 55篇 |
2023年 | 184篇 |
2022年 | 588篇 |
2021年 | 585篇 |
2020年 | 588篇 |
2019年 | 549篇 |
2018年 | 494篇 |
2017年 | 734篇 |
2016年 | 568篇 |
2015年 | 751篇 |
2014年 | 971篇 |
2013年 | 1268篇 |
2012年 | 1285篇 |
2011年 | 1343篇 |
2010年 | 1242篇 |
2009年 | 1322篇 |
2008年 | 1535篇 |
2007年 | 1382篇 |
2006年 | 1278篇 |
2005年 | 1190篇 |
2004年 | 1003篇 |
2003年 | 704篇 |
2002年 | 742篇 |
2001年 | 641篇 |
2000年 | 752篇 |
1999年 | 552篇 |
1998年 | 299篇 |
1997年 | 231篇 |
1996年 | 215篇 |
1995年 | 190篇 |
1994年 | 186篇 |
1993年 | 188篇 |
1992年 | 171篇 |
1991年 | 111篇 |
1990年 | 120篇 |
1989年 | 138篇 |
1988年 | 105篇 |
1987年 | 84篇 |
1986年 | 64篇 |
1985年 | 49篇 |
1984年 | 65篇 |
1983年 | 44篇 |
1982年 | 38篇 |
1981年 | 35篇 |
1980年 | 28篇 |
1979年 | 19篇 |
1978年 | 7篇 |
1974年 | 7篇 |
1965年 | 20篇 |
1964年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
Microgels are extremely interfacially active and are widely used to stabilize emulsions. However, they are commonly used to stabilize oil-in-water emulsions due to their intrinsic hydrophilicity and initially dispersed in water. In addition, there have been no attempts to control microgel structural layers that are formed at the interface and as a result it limits applications of microgel in advanced materials. Here, we show that by introducing octanol into poly(N-isopropylacrylamide-co-methacrylic acid) (PNIPAM-co-MAA) microgels, octanol-swollen microgels can rapidly diffuse from the initially dispersed oil phase onto the water droplet surface. This facilitates the formation of microgel-laden interfacial layers with strong elastic responses and also generates stable inverse water-in-oil Pickering emulsions. These emulsions can be used as templates to produce microgel colloidosomes, herein termed ‘microgelsomes’, with shells that can be fine-tuned from a particle monolayer to a well-defined bilayer. The microgelsomes can then be used to encapsulate and/or anchor nanoparticles, proteins, vitamin C, bio-based nanocrystals or enzymes. Moreover, the programmed release of these substances can be achieved by using ethanol as a trigger to mediate shell permeability. Thus, these reconfigurable microgelsomes with a microgel-bilayer shell can respond to external stimuli and demonstrate tailored properties, which offers novel insights into microgels and promise wider application of Pickering emulsions stabilized by soft colloids.Inverse W/O Pickering emulsions and reconfigurable microgelsomes with a well-defined bilayer structure are prepared from octanol-swollen PNIPAM-co-MAA microgels and the combination of binary microgels, which promise wider application of soft colloids. 相似文献
62.
LI Rui ZHANG Duan-Ming HUANG Ming-Tao SU Xiang-Ying CHEN Zhi-Yuan ZHU Hong-Ying ZHANG Lin 《理论物理通讯》2007,48(8):343-347
We propose a two-dimensional model of polydisperse granular mixtures with a power-law size distribution in the presence of stochastic driving. A fractal dimension D is introduced as a measurement of the inhomogeneity of the size distribution of particles. We define the global and partial granular temperatures of the multi-component mixture. By direct simulation Monte Carlo, we investigate how the inhomogeneity of the size distribution influences the dynamic properties of the mixture, focusing on the granular temperature, dissipated energy, velocity distribution, spatial clusterization, and collision time. We get the following results: a single granular temperature does not characterize a multi-component mixture and each species attains its own "granular temperature"; The velocity deviation from Gaussian distribution becomes more and more pronounced and the partial density of the assembly is more inhomogeneous with the increasing value of the fractal dimension D; The global granular temperature decreases and average dissipated energy per particle increases as the value of D augments. 相似文献
63.
Huaquan Guan Wenbin Luo Beihua Bao Yudan Cao Fangfang Cheng Sheng Yu Qiaoling Fan Li Zhang Qinan Wu Mingqiu Shan 《Molecules (Basel, Switzerland)》2022,27(10)
Polyphenolic acids are the widely occurring natural products in almost each herbal plant, among which rosmarinic acid (RA, C18H16O8) is well-known, and is present in over 160 species belonging to many families, especially the Lamiaceae. Aside from this herbal ingredient, dozens of its natural derivatives have also been isolated and characterized from many natural plants. In recent years, with the increasing focus on the natural products as alternative treatments, a large number of pharmacological studies have been carried out to demonstrate the various biological activities of RA such as anti-inflammation, anti-oxidation, anti-diabetes, anti-virus, anti-tumor, neuroprotection, hepatoprotection, etc. In addition, investigations concerning its biosynthesis, extraction, analysis, clinical applications, and pharmacokinetics have also been performed. Although many achievements have been made in various research aspects, there still exist some problems or issues to be answered, especially its toxicity and bioavailability. Thus, we hope that in the case of natural products, the present review can not only provide a comprehensive understanding on RA covering its miscellaneous research fields, but also highlight some of the present issues and future perspectives worth investigating later, in order to help us utilize this polyphenolic acid more efficiently, widely, and safely. 相似文献
64.
65.
等离子体流动控制激励器由于其响应速度快、激励频带宽、能量损耗低、可靠性强的优势,在航空航天领域的主动流动控制等方面得到了广泛应用.文章提出了一种新型的等离子体气动激励器——三电极共面介质阻挡放电激励器,研究了该激励器电极结构对放电特性和诱导气流速度的影响,并与传统共面介质阻挡放电和沿面介质阻挡放电激励器进行了比较.结果表明:(1)随着激励电压的提高,高压电极和地电极之间先出现了丝状放电并逐渐延伸到第三电极;(2)随着第三电极与高压电极之间的距离增大,诱导气流速率从2.4 m/s下降到0 m/s,而第三电极宽度的变动对诱导气流速度影响可忽略不计;(3)相同外部条件下,该激励器诱导的气流速度小于沿面介质阻挡放电激励器,但高于共面介质阻挡放电激励器. 相似文献
66.
67.
68.
69.
利用光纤中的量子几何相位(又称Berry相位),制作了单模光纤的线偏振光偏振面旋转器,并对器件进行了测量.实验数据表明,这种光纤偏振旋转器对光偏振面的旋转基本符合理论预计.对偏差进行处理后得到修正的定标公式,可更精确地反映出此光纤偏振旋转器的特性. 相似文献
70.
薄膜生长速率对有机光伏器件性能的影响 总被引:2,自引:2,他引:0
采用真空热蒸发镀膜的方法制备了酞菁铜(CuPc)和富勒烯(C60)构成的平面异质结结构光伏器件,并初步研究了CuPc薄膜生长速率对器件光伏性能的影响,我们发现以较大薄膜生长速率制备的器件表现出较大的短路电流和能量转换效率。X射线衍射和原子力显微镜观察的结果表明生长速率较大的CuPc薄膜结晶相含量较少,薄膜结构较均匀、致密、平整,这可能使得CuPc薄膜激子扩散和载流子迁移特性得到提高,也可能改善其与C60受主薄膜和ITO阳极的接触,并有利于载流子的分离和收集,从而表现出较好的光伏特性。 相似文献