全文获取类型
收费全文 | 19320篇 |
免费 | 3358篇 |
国内免费 | 3519篇 |
专业分类
化学 | 15884篇 |
晶体学 | 337篇 |
力学 | 836篇 |
综合类 | 275篇 |
数学 | 1928篇 |
物理学 | 6937篇 |
出版年
2024年 | 30篇 |
2023年 | 378篇 |
2022年 | 557篇 |
2021年 | 747篇 |
2020年 | 860篇 |
2019年 | 870篇 |
2018年 | 761篇 |
2017年 | 813篇 |
2016年 | 1038篇 |
2015年 | 1129篇 |
2014年 | 1372篇 |
2013年 | 1691篇 |
2012年 | 2001篇 |
2011年 | 2057篇 |
2010年 | 1559篇 |
2009年 | 1428篇 |
2008年 | 1499篇 |
2007年 | 1343篇 |
2006年 | 1192篇 |
2005年 | 883篇 |
2004年 | 628篇 |
2003年 | 501篇 |
2002年 | 549篇 |
2001年 | 486篇 |
2000年 | 338篇 |
1999年 | 322篇 |
1998年 | 186篇 |
1997年 | 154篇 |
1996年 | 107篇 |
1995年 | 117篇 |
1994年 | 83篇 |
1993年 | 98篇 |
1992年 | 67篇 |
1991年 | 47篇 |
1990年 | 40篇 |
1989年 | 46篇 |
1988年 | 27篇 |
1987年 | 33篇 |
1986年 | 25篇 |
1985年 | 21篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 9篇 |
1977年 | 6篇 |
1975年 | 9篇 |
1974年 | 9篇 |
1972年 | 11篇 |
1971年 | 7篇 |
1970年 | 5篇 |
1969年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 48 毫秒
1.
A numerical model was developed and validated to investigate the fluid–structure interactions between fully developed pipe flow and core–shell-structured microcapsule in a microchannel. Different flow rates and microcapsule shell thicknesses were considered. A sixth-order rotational symmetric distribution of von Mises stress over the microcapsule shell can be observed on the microcapsule with a thinner shell configuration, especially at higher flow rate conditions. It is also observed that when being carried along in a fully developed pipe flow, the microcapsule with a thinner shell tends to accumulate stress at a higher rate compared to that with a thicker shell. In general, for the same microcapsule configuration, higher flow velocity would induce a higher stress level over the microcapsule shell. The deformation gradient was used to capture the microcapsule's deformation in the present study. The effect of Young's modulus on the microcapsule shell on the microcapsule deformation was investigated as well. Our findings will shed light on the understanding of the stability of core–shell-structured microcapsule when subjected to flow-induced shear stress in a microfluidic system, enabling a more exquisite control over the breakup dynamics of drug-loaded microcapsule for biomedical applications. 相似文献
2.
设X是维数大于2的Banach空间,映射δ:B(X)→B(X)是2-局部Lie三重导子,则对所有A∈B(X)有δ(A)=[A,T]+φ(A),这里T∈B(X),φ是从B(X)到FI的齐次映射且满足对所有A,B∈B(X)有φ(A+B)=φ(A),其中B是交换子的和. 相似文献
3.
International Journal of Theoretical Physics - The Majorana representation, which provides an intuitive way to represent the quantum state by stars on the Bloch sphere, has drawn considerable... 相似文献
4.
水热合成法制备了不同磁性纳米洋葱碳(MCNOs)负载量(0%、1%、3%、5%)的MCNOs/CdS光催化剂。并通过X射线衍射分析(XRD)、扫描电子显微镜(SEM)、傅里叶红外光谱(FT-IR)、X射线光电子能谱(XPS)、紫外可见光光谱(UV-Vis)、磁滞回线测定仪(VSM)对其进行表征,探究了MCNOs负载比例对催化剂在可见光下降解RhB性能及机理的影响。结果表明,MCNOs能有效提高CdS的光催化效果,复合3%MCNOs后降解率为96%,与纯CdS相比降解率提高了30%,磁性分析表明,其具有良好的顺磁性并能实现催化剂的有效回收。MCNOs/CdS在可见光下催化降解RhB的一级反应动力学直线有较好的拟合度,表明制备的催化剂有较好的催化活性。 相似文献
5.
利用沙漠沙独特的化学组成特性和矿物特性,将沙漠沙荒料作为硅源,工业Al(OH)3作为铝源制备莫来石晶须.改变硅源/铝源配比和合成温度,结合XRD、SEM、TEM研究莫来石生长环境和自由生长形态的变化.研究结果表明:当沙漠沙与Al(OH)3的质量比为35/65时,在1200℃的低温下就能获得平均值>60的高长径比莫来石晶须;随着煅烧温度的升高,莫来石晶须长径比不断增大,当温度升至1300℃,平均长径比>94.随着合成温度的升高,莫来石的形成经过了一次莫来石和二次莫来石化两个阶段;若配方中Al2 O3处于过饱和状态,样品中刚玉相会随着煅烧温度的升高出现先增多后降低的变化现象. 相似文献
6.
Nanocomposite hydrogel consisting of Na‐montmorillonite with enhanced mechanical properties 下载免费PDF全文
Ting Li Shuangfei Xiang Piming Ma Huiyu Bai Weifu Dong Mingqing Chen 《Journal of Polymer Science.Polymer Physics》2015,53(14):1020-1026
A new kind of nanocomposite (NC) hydrogel with Na‐montmorillonite (MMT) is presented in this article. The NC hydrogels were synthesized by free radical copolymerization of acrylamide and (3‐acrylamidopropyl) trimethylammonium chloride (ATC) in the presence of MMT and N,N′‐methylene‐bis‐acrylamide used as chemical cross‐linker. Due to the cation‐exchange reaction between MMT and ATC (cationic monomer) during the synthesis of NC hydrogels, MMT platelets were considered chemical “plane” cross‐linkers, different from “point” cross‐linkers. With increasing amount of MMT, the crosslinking degree enhanced, causing a decrease of the swelling degree at equilibrium. Investigations of mechanical properties indicated that NC hydrogels exhibited enhanced strength and toughness, which resulted from chemical interaction between exfoliated MMT platelets and polymer chains in hydrogels. Dynamic shear measurements showed that both storage modulus and loss modulus increased with increasing MMT content. The idea described here provided a new route to prepare hydrogels with high mechanical properties by using alternative natural Na‐MMT. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1020–1026 相似文献
7.
Analysis and pharmacokinetic study of polyphyllin H in beagle dog plasma after oral administration of Rhizoma Paridis Extracts by LC‐MS/MS 下载免费PDF全文
8.
Jing Zhihong Ling Baoping Yu Yang Qi Wei Zhang Shufang 《Journal of Sol-Gel Science and Technology》2015,73(1):112-117
Journal of Sol-Gel Science and Technology - A novel gas sensing material, La–Y co-doped TiO2 nanoparticles, was synthesized by sol–gel method and applied to detect organic pollutants... 相似文献
9.
JPC – Journal of Planar Chromatography – Modern TLC - A new high-performance thin-layer chromatographic (HPTLC) method has been developed for the simultaneous estimation of... 相似文献
10.