全文获取类型
收费全文 | 14227篇 |
免费 | 2244篇 |
国内免费 | 2856篇 |
专业分类
化学 | 12096篇 |
晶体学 | 259篇 |
力学 | 533篇 |
综合类 | 210篇 |
数学 | 1406篇 |
物理学 | 4823篇 |
出版年
2024年 | 15篇 |
2023年 | 235篇 |
2022年 | 338篇 |
2021年 | 483篇 |
2020年 | 556篇 |
2019年 | 590篇 |
2018年 | 475篇 |
2017年 | 508篇 |
2016年 | 666篇 |
2015年 | 743篇 |
2014年 | 911篇 |
2013年 | 1221篇 |
2012年 | 1311篇 |
2011年 | 1405篇 |
2010年 | 1080篇 |
2009年 | 982篇 |
2008年 | 1134篇 |
2007年 | 1045篇 |
2006年 | 913篇 |
2005年 | 744篇 |
2004年 | 627篇 |
2003年 | 512篇 |
2002年 | 489篇 |
2001年 | 436篇 |
2000年 | 345篇 |
1999年 | 285篇 |
1998年 | 209篇 |
1997年 | 154篇 |
1996年 | 142篇 |
1995年 | 126篇 |
1994年 | 117篇 |
1993年 | 93篇 |
1992年 | 71篇 |
1991年 | 65篇 |
1990年 | 69篇 |
1989年 | 33篇 |
1988年 | 39篇 |
1987年 | 22篇 |
1986年 | 26篇 |
1985年 | 23篇 |
1984年 | 19篇 |
1983年 | 16篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1976年 | 5篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 633 毫秒
991.
992.
TSIM Karl Wah-keung 《高等学校化学研究》2010,(2)
Flavonoids exhibit a wide range of biological activities including anti-inflammatory activity,while some 1,3-benzoxazine derivatives show anti-inflammatory activity.In order to explore the novel anti-inflammatory agents,based on the principles of bioisosterism and hybridization,ten novel chromeno[8,7-e][1,3]oxazin-4-ones were synthesized and characterized with IR,1H NMR,MS and elemental analyses.The anti-inflammatory activities of the target compounds were evaluated via the croton oil-induced ear oedema tes... 相似文献
993.
994.
Shiyi Yu Liao Kai Liu Shuangshuang Ma Ying Chi Yaping Guo Danyang Hu Ruoxi Liu Pengfei Zhu Yun 《Moscow University Chemistry Bulletin》2021,76(5):343-351
Moscow University Chemistry Bulletin - The genus Achillea L. (Family: Asteraceae) is a kind of perennial plant, mostly distributed in north western region of China, especially in Tianshan Mountains... 相似文献
995.
Daozhong Hu Lai Chen Jun Tian Yuefeng Su Ning Li Gang Chen Yulu Hu Yueshan Dou Shi Chen Feng Wu 《中国化学》2021,39(1):165-173
Lithium plating on graphite anode is triggered by harsh conditions of fast charge and low temperature, which significantly accelerates SOH (state of health) degradation and may cause safety issues of lithium ion batteries (LIBs). This paper has reviewed recent research progress of lithium plating on graphite anode. Firstly, we summarize the forming mechanisms of Li plating with corresponding influence factors, the detecting methods and hazard of Li plating. Then, approaches to suppress Li plating are discussed, including anode surface modification, electrolyte composition optimization and development of optimal charge strategies. Finally, we conclude and propose the remaining challenges and prospects in terms of mechanism research, detecting approaches, and suppressing methods of Li plating. This review highlights the development of Li plating research and plays a guiding rule of further study on Li plating in LIBs. 相似文献
996.
Haishun Liu Chaochao DunLinming Dou Weiming Yang 《Journal of magnetism and magnetic materials》2011,323(12):1667-1670
The output voltage is an important parameter to determine the stress state in magnetic stress measurement, the relationship between the output voltage and the difference in the principal stresses was investigated by a comprehensive application of magnetic circuit theory, magnetization theory, stress analysis as well as the law of electromagnetic induction, and a corresponding quantitative equation was derived. It is drawn that the output voltage is proportional to the difference in the principal stresses, and related to the angle between the principal stress and the direction of the sensor. This investigation provides a theoretical basis for the principle stresses measurement by output voltage. 相似文献
997.
998.
Consistency of regularized spectral clustering 总被引:1,自引:0,他引:1
Clustering is a widely used technique in machine learning, however, relatively little research in consistency of clustering algorithms has been done so far. In this paper we investigate the consistency of the regularized spectral clustering algorithm, which has been proposed recently. It provides a natural out-of-sample extension for spectral clustering. The presence of the regularization term makes our situation different from that in previous work. Our approach is mainly an elaborate analysis of a functional named the clustering objective. Moreover, we establish a convergence rate. The rate depends on the approximation property and the capacity of the reproducing kernel Hilbert space measured by covering numbers. Some new methods are exploited for the analysis since the underlying setting is much more complicated than usual. Some new methods are exploited for the analysis since the underlying setting is much more complicated than usual. 相似文献
999.
1000.
Reagen Ying‐Tai Su Li‐Ko Chiu Shan‐Wei Weng Ying‐Shiun Chou Raymond Chien‐Chao Tsiang 《Journal of Polymer Science.Polymer Physics》2012,50(4):280-288
White polymeric light‐emitting diode (WPLED) based on a single polymer, poly(3‐hexylthiophene‐alt‐9,9‐dioctylfluorene) (PTAF), has been successfully demonstrated. This conjugated alternating copolymer, PTAF, comprises 50 mol % of 3‐hexylthiophene which is an orange‐red color chromophore and 50 mol % 9,9‐dioctylfluorene which is a bluish‐green color chromophore. It was synthesized by Suzuki cross‐coupling reaction and has a molecular weight of 15,021 and polydispersity of 1.36. Nanocomposite consisting PTAF and graphene nanosheets enhances the optoelectronic properties and the device fabricated with a configuration of ITO/PEDOT:PSS/(PTAF + 1% graphene)/Ca/Al shows two‐color white electroluminescence with CIE 1931 coordinates of (0.28, 0.34). The white luminescence from a single polymer affords the WPLED device a simple structure and low fabrication cost. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011 相似文献