全文获取类型
收费全文 | 3323篇 |
免费 | 551篇 |
国内免费 | 350篇 |
专业分类
化学 | 2508篇 |
晶体学 | 41篇 |
力学 | 131篇 |
综合类 | 3篇 |
数学 | 339篇 |
物理学 | 1202篇 |
出版年
2024年 | 2篇 |
2023年 | 66篇 |
2022年 | 95篇 |
2021年 | 138篇 |
2020年 | 141篇 |
2019年 | 124篇 |
2018年 | 112篇 |
2017年 | 103篇 |
2016年 | 158篇 |
2015年 | 167篇 |
2014年 | 188篇 |
2013年 | 274篇 |
2012年 | 345篇 |
2011年 | 335篇 |
2010年 | 195篇 |
2009年 | 234篇 |
2008年 | 191篇 |
2007年 | 203篇 |
2006年 | 184篇 |
2005年 | 126篇 |
2004年 | 122篇 |
2003年 | 84篇 |
2002年 | 75篇 |
2001年 | 47篇 |
2000年 | 57篇 |
1999年 | 67篇 |
1998年 | 46篇 |
1997年 | 37篇 |
1996年 | 58篇 |
1995年 | 24篇 |
1994年 | 28篇 |
1993年 | 29篇 |
1992年 | 25篇 |
1991年 | 18篇 |
1990年 | 21篇 |
1989年 | 22篇 |
1988年 | 13篇 |
1987年 | 19篇 |
1986年 | 8篇 |
1985年 | 7篇 |
1984年 | 13篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1957年 | 2篇 |
排序方式: 共有4224条查询结果,搜索用时 31 毫秒
971.
972.
Ionics - Manganese phosphate (Mn3(PO4)2·3H2O) nanosheets are successfully fabricated via a facile chemical precipitation method. The Mn3(PO4)2·3H2O nanosheets synthesized at... 相似文献
973.
Kai Yao Yiwang Chen Lie Chen Huanling Kong Weihua Zhou Fan Li Xiaohui He Yen Wei 《Journal of polymer science. Part A, Polymer chemistry》2010,48(2):434-442
Novel liquid‐crystalline alternating conjugated copolymers [ P(P(6)CN‐alt‐Cz) and P(P(6)CN‐alt‐MeP) ] with phenylene and carbazolylene or phenylene with methyl substitution onto the main chain have been synthesized through palladium‐catalyzed Suzuki coupling reactions. The influence of the incorporation of carbazolylene and the substituted phenylene into the main chain on the thermal, mesomorphic, and luminescent properties has been investigated by Fourier transform infrared spectroscopy, thermogravimetry, differential scanning calorimetry, polarized optical microscopy, ultraviolet–visible spectroscopy, photoluminescence (PL), and cyclic voltammetry. These polymers show highly thermal stability, losing little of their weights when heated to 360 °C. The conjugated copolymers exhibit liquid crystallinity at elevated temperature. The existence of the chromophoric terphenyl core endows the copolymers with high PL and the polymer P(P(6)CN‐alt‐Cz containing carbazolylene unit can emit more pure blue light. All the copolymer films with low band gaps about 2.3–2.4 eV undergo reversible oxidation and reduction processes, significantly lower than the band gap of poly(p‐phenylene). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 434–442, 2010 相似文献
974.
Based on the analysis and the discussion of the influence of thermal ionization energy and various scatterings on magnetoresistance(MR) of p-type diamond films, a revised model of valence band split-off over temperature is put forward, and a corresponding calculation formula is given for the MR of p-type diamond films (Corbino discs). It is shown that the theoretical calculation that the MR of diamond films changes with temperature is consistent with the experiment. The influence of Fermi energy level on MR of diamond films is discussed. Additionally, the thermal effect mechanism of MR in p-type diamond films is also explored. 相似文献
975.
Yu Kong Ming‐Ming Yan Wei Liu Cai‐Yun Chen Bao‐Shan Zhao Yuan‐Gang Zu Yu‐Jie Fu Meng Luo Michael Wink 《Journal of separation science》2010,33(15):2278-2286
The enrichment and separation of astragalosides I–IV (AGs I–IV) were studied on eight macroporous resins in the present study. SA‐3 resin offered the best adsorption and desorption capacities for AGs I–IV than other resins. The models of adsorption kinetics were investigated in order to elucidate the mechanism of adsorption. The pseudo‐second‐order model was the better choice than the pseudo‐first‐order model to describe the adsorption behavior of AGs I–IV onto SA‐3 resin. The equilibrium experimental data were well fitted to Langmuir and Freundlich isotherms. SA‐3 resin adsorption chromatography tests were carried out to optimize the separation process of AGs I–IV from Radix Astragali extracts. With the optimum parameters for adsorption and desorption, the contents of AGs I–IV were 8.78‐, 11.60‐, 10.52‐ and 11.28‐fold increased with the recovery yields being 65.88, 90.92, 84.25 and 94.17%, respectively. The preparative enrichment and separation of AGs I–IV from Radix Astragali extracts can be easily and effectively achieved by SA‐3 resin adsorption chromatography. The developed methodology can also be referenced for the separation of other active constituents from herbal materials and manufacture of Radix Astragali products. 相似文献
976.
977.
F. Gao D. D. Huang J. P. Li Y. X. Lin M. Y. Kong J. M. Li Y. P. Zeng L. Y. Lin 《Journal of Crystal Growth》2000,220(4):457-460
Three n–p–n Si/SiGe/Si heterostructures with different layer thickness and doping concentration have been grown by a home-made gas source molecular-beam epitaxy (GSMBE) system using phosphine (PH3) and diborane (B2H6) as n-and p-type in situ doping sources, respectively. Heterojunction bipolar transistors (HBTs) have been fabricated using these structures and a current gain of 40 at 300 K and 62 at 77 K have been obtained. The influence of thickness and doping concentration of the deposited layers on the current gain of the HBTs is discussed. 相似文献
978.
979.
Annals of Operations Research - We study a problem of integrating the supply chain of roundwood with the supply chain of forest biomass. The developed optimization model is a multiperiod,... 相似文献
980.
Chen Shifeng Wei Xuebin Liu Jinhui Sun Zhanxue Chen Gongxin Yang Mei Liu Yuanyuan Wang Duo Ma Chengcui Kong Dexuan 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(6):2583-2596
Journal of Radioanalytical and Nuclear Chemistry - Mineralogical study showed that the Yuejin uranium ore is from a low grade, high carbonate and high pyrite sandstone type uranium deposit. Uranium... 相似文献