首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   23228篇
  免费   4029篇
  国内免费   3327篇
化学   16773篇
晶体学   323篇
力学   1694篇
综合类   241篇
数学   2838篇
物理学   8715篇
  2024年   45篇
  2023年   417篇
  2022年   534篇
  2021年   666篇
  2020年   853篇
  2019年   865篇
  2018年   728篇
  2017年   735篇
  2016年   1054篇
  2015年   1097篇
  2014年   1338篇
  2013年   1685篇
  2012年   2072篇
  2011年   2145篇
  2010年   1583篇
  2009年   1419篇
  2008年   1610篇
  2007年   1462篇
  2006年   1467篇
  2005年   1233篇
  2004年   936篇
  2003年   833篇
  2002年   805篇
  2001年   685篇
  2000年   514篇
  1999年   480篇
  1998年   366篇
  1997年   340篇
  1996年   380篇
  1995年   279篇
  1994年   252篇
  1993年   197篇
  1992年   206篇
  1991年   206篇
  1990年   155篇
  1989年   151篇
  1988年   95篇
  1987年   83篇
  1986年   97篇
  1985年   73篇
  1984年   56篇
  1983年   46篇
  1982年   34篇
  1981年   32篇
  1980年   30篇
  1978年   24篇
  1977年   26篇
  1976年   23篇
  1974年   20篇
  1973年   26篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Li  Zhisheng  Jiang  Haokai  Cheng  Yanying  Gao  Yunji  Chen  Longfei  Zhang  Yuchun  Li  Tao  Xing  Shaoshuai 《Journal of Thermal Analysis and Calorimetry》2022,147(21):12139-12154
Journal of Thermal Analysis and Calorimetry - Few investigations have focused on the influence of longitudinal fire source location on the temperature profile of smoke induced by fire in a tunnel...  相似文献   
992.
Polystyrene-bound diethanolamine based ionic liquids (PS-DHEEAB and PS-THEAB) were synthesized and applied for the chemical fixation of CO2 into cyclic carbonates without any additional co-catalyst and solvent. The effect of the catalysts with different number of hydroxyl group in the cation of the IL on the reaction was systematically investigated. Highest activity and selectivity were achieved in the presence of polystyrene supported diethanolamine ethyl bromide (PS-DHEEAB) in comparison with other catalysts employed. The catalyst was tough in stability and also found to be extended to a variety of terminal epoxides and aziridines. The relationship between high catalytic reactivity and the –OH functional groups was proposed.  相似文献   
993.
994.
This paper summarizes the main achievements about the structure–activity relationships of anthocyanidin glycosylation. Anthocyanidin glycosylation is the essential step of anthocyanin biosynthesis and also the prerequisite of the further modifications of anthocyanins, which is jointly characterized by the glycosylation site, the type and number of the glycosyl as well as the glycosidic bond type. It generally enhances the stability, results in the hypsochromic effect and blueing, decreases the bioavailability and anticancer activity, and decreases, increases, or does not change the antioxidant activity of the anthocyanidins or anthocyanins, which is synergetically determined by the glycosylation site and the type and number of the glycosyl. Thereinto, in nature, the blue hues caused by the glycosylation may also be reinforced by the formation of the anthocyanic vacuolar inclusions. This review could provide a reference for the research of the structure-optimizing and function-exploiting of anthocyanins.  相似文献   
995.
In this paper, we mainly study three types of gauge transformation operators for the q-mKP hierarchy. The successive applications of these gauge transformation operators are derived. And the corresponding communities between them are also investigated.  相似文献   
996.
997.
998.
Vertically aligned γ-AlOOH nanosheets (NSs) have been successfully fabricated on flexible Al foils via a solvothermal route without morphology-directing agents. Three different reaction temperature (25, 80, and 120 ?C) and time (30 min, 45 min, and 24 h) are discussed for the growth period, which efficiently tune the density and size of the γ-AlOOH NSs. Meanwhile, the growth speed of the nanosheets confirms that dominant growth stage is seen in the initial 45 min. Furthermore, the interlayer of the γ-AlOOH NSs displays an average height of 140 nm and superhydrophilicity. By dynamic adsorption, the assynthesized γ-AlOOH NSs exhibit an outstanding NH3 adsorption capacity of up to 146 mg/g and stably excellent regeneration for 5 cycles. The mechanism of NH3 adsorption on the in-plane of the γ-AlOOH NSs is explained by the Lewis acid/base theory. The H-bond interactions among the NH3 molecules and the edge groups (-OH) further improve the capture ability of the nanosheets.  相似文献   
999.
1000.
Lu  Yuchan  He  Qiao  Peng  Qiao  Chen  Wenhai  Cheng  Qunpeng  Song  Guangsen  Fan  Guozhi 《Cellulose (London, England)》2021,28(13):8343-8354
Cellulose - The coproduction of 5-hydroxymethylfurfural (5-HMF) and furfural (FUR) via the direct hydrolysis of holocellulose analogue composed of cellulose and hemicellulose was investigated. The...  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号