全文获取类型
收费全文 | 32166篇 |
免费 | 5679篇 |
国内免费 | 5603篇 |
专业分类
化学 | 25556篇 |
晶体学 | 481篇 |
力学 | 1407篇 |
综合类 | 456篇 |
数学 | 3396篇 |
物理学 | 12152篇 |
出版年
2024年 | 103篇 |
2023年 | 620篇 |
2022年 | 1155篇 |
2021年 | 1170篇 |
2020年 | 1341篇 |
2019年 | 1367篇 |
2018年 | 1175篇 |
2017年 | 1202篇 |
2016年 | 1708篇 |
2015年 | 1811篇 |
2014年 | 2069篇 |
2013年 | 2650篇 |
2012年 | 3081篇 |
2011年 | 3193篇 |
2010年 | 2298篇 |
2009年 | 2223篇 |
2008年 | 2388篇 |
2007年 | 2130篇 |
2006年 | 2000篇 |
2005年 | 1642篇 |
2004年 | 1230篇 |
2003年 | 1024篇 |
2002年 | 1093篇 |
2001年 | 909篇 |
2000年 | 728篇 |
1999年 | 622篇 |
1998年 | 383篇 |
1997年 | 343篇 |
1996年 | 309篇 |
1995年 | 262篇 |
1994年 | 220篇 |
1993年 | 206篇 |
1992年 | 146篇 |
1991年 | 126篇 |
1990年 | 93篇 |
1989年 | 86篇 |
1988年 | 56篇 |
1987年 | 62篇 |
1986年 | 55篇 |
1985年 | 41篇 |
1984年 | 24篇 |
1983年 | 17篇 |
1982年 | 16篇 |
1981年 | 14篇 |
1980年 | 10篇 |
1979年 | 8篇 |
1977年 | 4篇 |
1975年 | 5篇 |
1973年 | 4篇 |
1957年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
为提高煤与瓦斯突出矿井瓦斯抽放效果,建立了3个一级指标、14个二级指标的突出矿井瓦斯抽放限制影响因素评价指标体系,利用AHP和熵权法分别确定指标因子主、客观权重.通过实地调研分析和反馈验证了AHP-熵权法的可行性和正确性,利用加权平均法确定评价模型的综合权重.研究表明:封孔方式、钻孔半径、抽放时间、煤体裂隙发育程度和抽放负压是目前影响煤矿瓦斯抽放效果的主控因素. 相似文献
3.
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
4.
The Ramanujan Journal - We calculate the dimensions of the spaces of invariant vectors under the Klingen congruence subgroup of level $${\mathfrak {p}}^2$$ for all irreducible, admissible... 相似文献
5.
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
![点击此处可从《Biomedical chromatography : BMC》网站下载免费的PDF全文](/ch/ext_images/free.gif)
6.
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
7.
Nonlinear Dynamics - With an increasing number of people sharing feelings and opinions online, the online platforms have become one of the most important channels for public opinion dissemination.... 相似文献
8.
Yi Han Zibo Xue Dr. Guangwu Li Dr. Yanwei Gu Dr. Yong Ni Dr. Shaoqiang Dong Prof. Chunyan Chi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(23):9111-9116
Incorporation of a non-hexagonal ring into a nanographene framework can lead to new electronic properties. During the attempted synthesis of naphthalene-bridged double [6]helicene and heptagon-containing nanographene by the Scholl reaction, an unexpected azulene-embedded nanographene and its triflyloxylated product were obtained, as confirmed by X-ray crystallographic analysis and 2D NMR spectroscopy. A 5/7/7/5 ring-fused substructure containing two formal azulene units is formed, but only one of them shows an azulene-like electronic structure. The formation of this unique structure is explained by arenium ion mediated 1,2-phenyl migration and a naphthalene to azulene rearrangement reaction according to an in-silico study. This report represents the first experimental example of the thermodynamically unfavorable naphthalene to azulene rearrangement and may lead to new azulene-based molecular materials. 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.