全文获取类型
收费全文 | 37090篇 |
免费 | 5642篇 |
国内免费 | 3649篇 |
专业分类
化学 | 25733篇 |
晶体学 | 358篇 |
力学 | 2227篇 |
综合类 | 241篇 |
数学 | 4280篇 |
物理学 | 13542篇 |
出版年
2024年 | 111篇 |
2023年 | 759篇 |
2022年 | 1224篇 |
2021年 | 1362篇 |
2020年 | 1443篇 |
2019年 | 1329篇 |
2018年 | 1150篇 |
2017年 | 1067篇 |
2016年 | 1610篇 |
2015年 | 1633篇 |
2014年 | 2004篇 |
2013年 | 2578篇 |
2012年 | 3253篇 |
2011年 | 3212篇 |
2010年 | 2180篇 |
2009年 | 2050篇 |
2008年 | 2203篇 |
2007年 | 1960篇 |
2006年 | 1842篇 |
2005年 | 1539篇 |
2004年 | 1301篇 |
2003年 | 984篇 |
2002年 | 894篇 |
2001年 | 738篇 |
2000年 | 691篇 |
1999年 | 829篇 |
1998年 | 693篇 |
1997年 | 635篇 |
1996年 | 705篇 |
1995年 | 601篇 |
1994年 | 550篇 |
1993年 | 470篇 |
1992年 | 449篇 |
1991年 | 364篇 |
1990年 | 324篇 |
1989年 | 236篇 |
1988年 | 216篇 |
1987年 | 198篇 |
1986年 | 141篇 |
1985年 | 156篇 |
1984年 | 135篇 |
1983年 | 116篇 |
1982年 | 80篇 |
1981年 | 59篇 |
1980年 | 49篇 |
1979年 | 33篇 |
1978年 | 26篇 |
1976年 | 27篇 |
1975年 | 31篇 |
1974年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
Liang Wanjun Liu Zhengqing Li Dan Wu Xiaoping Liu Shaopu He Youqiu 《Mikrochimica acta》2015,182(1-2):297-306
Microchimica Acta - We describe a novel fluorescent bioprobe for the sensitive and selective detection of double-stranded DNA (dsDNA). It consists of quantum dots (Q-dots) whose fluorescence is... 相似文献
994.
995.
This study investigated the possibility of substituting petroleum-based polymers with biopolymers for films and paper coatings. Arabinoxylan (AX) was extracted from distillers’ grains, a low-value corn ethanol byproduct, and modified through crosslinking with glutaraldehyde (GA) which was made into films and paper coatings. The effects of degree of substitution (DS) on film and coating properties of GA cross-linked AX, referred to as GAX, were investigated. The GAX films had markedly higher tensile strength, approximately 3 times higher than the unmodified AX films at low DS, with higher DS causing a negative effect on the film tensile strength. Compared to unmodified AX coating, paper coated with GAX also had significantly higher tensile index, presumably due to high adhesion between the coating and paper interface. When used as a coating binder with calcium carbonate pigments, GAX showed comparable performance to polyvinyl alcohol, a common industrial binder, demonstrating the potential to be substituted for the petroleum-based paper coating binder. 相似文献
996.
997.
998.
A four-dimensional hyperchaotic system with five parameters is proposed. Its dynamical properties such as dissipativity, equilibrium points, Lyapunov exponent, Lyapunov dimension, bifurcation diagrams and Poincare maps are analyzed theoretically and numerically. Theoretical analyses and simulation tests indicate that the new system's dynamics behavior can be periodic attractor, chaotic attractor and hyperchaotic attractor as the parameter varies. Finally, the circuit of this new hyperchaotic system is designed and realized by Multisim software. The simulation results confirm that the chaotic system is different from the existing chaotic systems and is a novel hyperchaotic system. The system is recommendable for many engineering applications such as information processing, cryptology, secure communications, etc. 相似文献
999.
1000.
Multifunctional mesoporous silica nanoparticles in poly(ethylene‐co‐vinyl acetate) for transparent heat retention films 下载免费PDF全文
Md Abdul Mumin Kazi Farida Akhter Sara Dresser Sasha T. van Dinther Wei Wu Paul A. Charpentier 《Journal of Polymer Science.Polymer Physics》2015,53(12):851-859
Transparent inorganic‐polymer nanocomposite films are of tremendous current interest inemerging solar coverings including photovoltaic encapsulants and commercial greenhouse plastics, but suffer from significant radiative heat loss. This work provides a new and simple approach for controlling this heat loss by using mesoporous silica/quantum dot nanoparticles in poly(ethylene‐co‐vinyl acetate) (EVA) films. Mesoporous silica shells were grown on CdS‐ZnS quantum dot (QDs) cores using a reverse microemulsion technique, controlling the shell thickness. These mesoporous silica nanoparticles (MSNs) were then melt‐mixed with EVA pellets using a mini twin‐screw extruder and pressed into thin films of concentration variable controlled thickness. The results demonstrate that the experimental MSNs showed improved infrared and thermal wavebands retention in the EVA transparent films compared to commercial silica additives, even at lower concentrations. It was also found MSNs enhanced the quantum yield and photostability of the QDs, providing high visible light transmission and blocking of UV transmission of interest for next generation solar coatings. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 851–859 相似文献