全文获取类型
收费全文 | 84572篇 |
免费 | 732篇 |
国内免费 | 489篇 |
专业分类
化学 | 29241篇 |
晶体学 | 825篇 |
力学 | 7065篇 |
数学 | 32633篇 |
物理学 | 16029篇 |
出版年
2023年 | 57篇 |
2022年 | 140篇 |
2021年 | 364篇 |
2020年 | 391篇 |
2019年 | 398篇 |
2018年 | 10670篇 |
2017年 | 10467篇 |
2016年 | 6474篇 |
2015年 | 1188篇 |
2014年 | 776篇 |
2013年 | 1199篇 |
2012年 | 4383篇 |
2011年 | 10974篇 |
2010年 | 5948篇 |
2009年 | 6357篇 |
2008年 | 6893篇 |
2007年 | 9005篇 |
2006年 | 410篇 |
2005年 | 1456篇 |
2004年 | 1630篇 |
2003年 | 2076篇 |
2002年 | 1098篇 |
2001年 | 270篇 |
2000年 | 303篇 |
1999年 | 175篇 |
1998年 | 206篇 |
1997年 | 167篇 |
1996年 | 215篇 |
1995年 | 126篇 |
1994年 | 90篇 |
1993年 | 102篇 |
1992年 | 66篇 |
1991年 | 72篇 |
1990年 | 58篇 |
1989年 | 65篇 |
1988年 | 63篇 |
1987年 | 71篇 |
1986年 | 62篇 |
1985年 | 58篇 |
1984年 | 55篇 |
1982年 | 55篇 |
1981年 | 46篇 |
1980年 | 61篇 |
1979年 | 55篇 |
1978年 | 44篇 |
1914年 | 45篇 |
1913年 | 40篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
31.
He Haidong Yang Haifeng Zhou Longpeng Chen Tianchi 《Journal of Russian Laser Research》2015,36(3):292-299
Ni–Co alloys have a wide range of applications in various fields owning to their excellent physical, chemical, and mechanical properties. In this paper, we prepare Ni–Co alloy coatings on 316L stain steel surfaces by electroplating. We present a novel approach utilizing a nanosecond laser to induce microtextures on Ni–Co alloy coatings. We study experimentally the effects of laser power and scanning rate on the surface morphologies of Ni–Co alloy coatings. The results indicate that the shape and size of induced microtextures can be controlled by the laser power and scanning rate. The size of grains increases with increase in the work current of the laser (WCL) at a certain scanning rate. With the WCL constant, the size of grains decreases with increase in scanning rate while their average height increases. It is a simple and easily-controlled method for the fabrication of microstructures on Ni–Co alloy coatings, which has promising applications in investigations of the properties of microtextured surfaces, such as friction, adhesion, and wetting. 相似文献
32.
Briana L. Simms Nan Ji Indika Chandrasiri Mohammad Farid Zia Chinwe S. Udemgba Ravinder Kaur Jared H. Delcamp Alex Flynt Chalet Tan Davita L. Watkins 《Journal of polymer science. Part A, Polymer chemistry》2021,59(19):2177-2192
Here, we demonstrate the applicability of self-assembling linear-dendritic block copolymers (LDBCs) and their nanoaggregates possessing varied surfaces as therapeutic nanocarriers. These LDBCs are comprised of a hydrophobic, linear polyester chemically coupled to a hydrophilic dendron polyamidoamine (PAMAM)—the latter of which acts as the surface of the self-assembled nanoaggregate in aqueous media. To better understand how surface charge density affects the overall operability of these nanomaterials, we modified the nanoaggregate surface to yield cationic (NH3+), neutral (OH), and anionic (COO−) surfaces. The effect of these modifications on the physicochemical properties (i.e., size, morphology, and surface charge density), colloidal stability, and cellular uptake mechanism of the polymeric nanocarrier were investigated. This comparative study demonstrates the viability of nanoaggregates formed from PDLLA-PAMAM LDBCs to serve as nanocarriers for applications in drug delivery. 相似文献
33.
34.
35.
36.
Zenon Moszner 《Aequationes Mathematicae》2018,92(4):617-625
We give the form of the output function in Ginsburg’s machine in which the input and output dictionaries are abelian groups and the transition function is of a special form. 相似文献
37.
38.
The present study was designed to evaluate the contents of different antioxidants compounds and their antioxidant activities in Jalopeno peppers (Capsicum annuum) cultivars (El Dorido, Grande, Tula, Sayula and El Rey) extracts. Free radical scavenging activity of Grande was recorded as high as 87% followed by El Dorido (83%). Results of reducing power (Fe3+ to Fe2+) showed that Grande (0.85%) and El Dorido (0.81%) fruit extract absorbance value were close to synthetic antioxidant BHT (0. 97%) obtained at100 μg/mL. The results showed that total phenolic content of El Dorido and Grande were significantly higher compared to other Jalapeno pepper. Results indicated strong and positive correlation between antioxidant activity and carotenoids content (r = 0.75), vitamin C (r = 0.78) and total capsaicinoids (r = 0.84), respectively. The results of the antioxidant activity assays showed that the El Dorido and Grande had strongest antioxidant activity compared to other peppers cultivars in this study. 相似文献
39.
40.
Research on Chemical Intermediates - High electrical conductivity and high surface area are two main parameters which influence supercapacitor electrode performance. Graphene has gained prominence... 相似文献