全文获取类型
收费全文 | 38610篇 |
免费 | 6679篇 |
国内免费 | 4389篇 |
专业分类
化学 | 26500篇 |
晶体学 | 522篇 |
力学 | 2575篇 |
综合类 | 288篇 |
数学 | 4448篇 |
物理学 | 15345篇 |
出版年
2024年 | 148篇 |
2023年 | 794篇 |
2022年 | 1306篇 |
2021年 | 1352篇 |
2020年 | 1529篇 |
2019年 | 1430篇 |
2018年 | 1274篇 |
2017年 | 1197篇 |
2016年 | 1803篇 |
2015年 | 1782篇 |
2014年 | 2170篇 |
2013年 | 2739篇 |
2012年 | 3314篇 |
2011年 | 3444篇 |
2010年 | 2356篇 |
2009年 | 2314篇 |
2008年 | 2538篇 |
2007年 | 2267篇 |
2006年 | 2172篇 |
2005年 | 1686篇 |
2004年 | 1346篇 |
2003年 | 1126篇 |
2002年 | 1043篇 |
2001年 | 835篇 |
2000年 | 873篇 |
1999年 | 826篇 |
1998年 | 743篇 |
1997年 | 690篇 |
1996年 | 700篇 |
1995年 | 620篇 |
1994年 | 542篇 |
1993年 | 430篇 |
1992年 | 425篇 |
1991年 | 330篇 |
1990年 | 304篇 |
1989年 | 240篇 |
1988年 | 205篇 |
1987年 | 175篇 |
1986年 | 153篇 |
1985年 | 152篇 |
1984年 | 104篇 |
1983年 | 71篇 |
1982年 | 60篇 |
1981年 | 36篇 |
1980年 | 16篇 |
1979年 | 11篇 |
1977年 | 2篇 |
1971年 | 1篇 |
1959年 | 1篇 |
1957年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
941.
942.
943.
944.
945.
946.
"一带一路"战略为深化我国与沿线国家的教育交流合作提供了重要契机,也为我国的新工科人才培养体系的理论研究与教育实践开拓了新视野,提出了新挑战。在以新技术、新业态、新模式、新产业为代表的新经济蓬勃发展的大背景下,对工程科技人才提出了更高要求。建设具有新理念、新结构、新体系、新质量、新模式的新工科,迫切需要借助国际化加快工程人才教育体系的改革创新。构建面向"一带一路"的工程教育国际化新体系,面向新工科人才培养,密切结合"一带一路"沿线各国工科人才培养的实际情况,以工程力学、航空航天工程、机械工程等专业的国际化联合培养为抓手,深入研究面向新工科建设的"一带一路"工程教育国际化新体系。 相似文献
947.
Ben Li Yumeng Ji Chenlong Yi Xufeng Wang Chaoyang Liu Chufan Wang Xiaohu Lu Xiaohan Xu Xiaowei Wang 《Molecules (Basel, Switzerland)》2022,27(13)
Atherosclerosis (AS) is one of the leading causes of death among the elderly, and is primarily caused by foam cell generation and macrophage inflammation. Rutin is an anti-inflammatory, anti-oxidant, anti-allergic, and antiviral flavonoid molecule, known to have anti-atherosclerotic and autophagy-inducing properties, but its biological mechanism remains poorly understood. In this study, we uncovered that rutin could suppress the generation of inflammatory factors and reactive oxygen species (ROS) in ox-LDL-induced M2 macrophages and enhance their polarization. Moreover, rutin could decrease foam cell production, as shown by oil red O staining. In addition, rutin could increase the number of autophagosomes and the LC3II/I ratio, while lowering p62 expression. Furthermore, rutin could significantly inhibit the PI3K/ATK signaling pathway. In summary, rutin inhibits ox-LDL-mediated macrophage inflammation and foam cell formation by inducing autophagy and modulating PI3K/ATK signaling, showing potential in treating atherosclerosis. 相似文献
948.
Jie Wang Yuntian Xing Yang Dai Yingnan Li Wenyan Xiang Jianrong Dai Fei Xu 《Molecules (Basel, Switzerland)》2022,27(13)
Pomacea canaliculata, one of the 100 most destructive invasive species in the world, and it is an important intermediate host of Angiostrongylus cantonensis. The molluscicides in current use are an effective method for controlling snails. However, most molluscicides have no slow-release effect and are toxic to nontarget organisms. Thus, these molluscicides cannot be used on a large scale to effectively act on snails. In this study, gelatin, a safe and nontoxic substance, was combined with sustained-release molluscicide and was found to reduce the toxicity of niclosamide to nontarget organisms. We assessed the effects of gelatin and molluscicide in controlling P. canaliculata snails and eggs. The results demonstrated that the niclosamide retention time with 1.0% and 1.5% gelatin sustained-release agents reached 20 days. Additionally, the mortality rate of P. canaliculata and their eggs increased as the concentration of the niclosamide sustained-release agents increased. The adult mortality rate of P. canaliculata reached 50% after the snails were exposed to gelatin with 0.1 mg/L niclosamide for 48 h. The hatching rate of P. canaliculata was only 28.5% of the normal group after the treatment was applied. The sustained-release molluscicide at this concentration was less toxic to zebrafish, which means that this molluscicide can increase the safety of niclosamide to control P. canaliculata in aquatic environments. In this study, we explored the safety of using niclosamide sustained-release agents with gelatin against P. canaliculata. The results suggest that gelatin is an ideal sustained-release agent that can provide a foundation for subsequent improvements in control of P. canaliculata. 相似文献
949.
Chao-jiang Zhang Shuai-ting Yan Hong-guang Xu Xi-ling Xu Wei-iun Zheng 《化学物理学报(中文版)》2021,34(6):769-776
We measured the photoelectron spectra of AlnC4-(n=2-4) clusters by using size-selected anion photoelectron spectroscopy.The structures of AlnC4-/0 (n=2-4) clust... 相似文献
950.
An N-heterocyclic carbene(NHC)-catalyzed enantioselective Mannich reaction of the remote γ-carbon of cyclopropylcarbaldehydes is disclosed for the first time. Diastereo-and enantiomerically enriched multicyclic δ-lactam compound is afforded as the main product from 8 possible stereo-specific isomers through dynamic kinetic asymmetric transformation(DYKAT) processes. Multiple chiral functional molecules can be afforded from the lactam products through simple protocols with retentions of the optical purities. 相似文献