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   8314篇
  免费   455篇
  国内免费   256篇
化学   5971篇
晶体学   73篇
力学   222篇
综合类   39篇
数学   913篇
物理学   1807篇
  2023年   65篇
  2022年   112篇
  2021年   266篇
  2020年   226篇
  2019年   258篇
  2018年   200篇
  2017年   166篇
  2016年   334篇
  2015年   297篇
  2014年   373篇
  2013年   531篇
  2012年   554篇
  2011年   612篇
  2010年   394篇
  2009年   446篇
  2008年   529篇
  2007年   462篇
  2006年   393篇
  2005年   345篇
  2004年   332篇
  2003年   267篇
  2002年   285篇
  2001年   251篇
  2000年   186篇
  1999年   139篇
  1998年   76篇
  1997年   72篇
  1996年   67篇
  1995年   66篇
  1994年   67篇
  1993年   65篇
  1992年   58篇
  1991年   36篇
  1990年   44篇
  1989年   26篇
  1988年   34篇
  1987年   25篇
  1986年   19篇
  1985年   34篇
  1984年   26篇
  1983年   28篇
  1982年   23篇
  1981年   31篇
  1980年   20篇
  1979年   19篇
  1978年   28篇
  1977年   19篇
  1976年   19篇
  1975年   19篇
  1974年   14篇
排序方式: 共有9025条查询结果,搜索用时 109 毫秒
1.
2.
3.
Journal of Thermal Analysis and Calorimetry - The aim of this work is to synthesize and characterize a new structured silver–clay dried, calcined or sintered at different temperatures...  相似文献   
4.
5.
Oral microbes have the capacity to spread throughout the gastrointestinal system and are strongly associated with multiple diseases. Given that tonsils are located between the oral cavity and the laryngopharynx at the gateway of the alimentary and respiratory tracts, tonsillar tissue may also be affected by microbiota from both the oral cavity (saliva) and the alimentary tract. Here, we analyzed the distribution and association of the microbial communities in the saliva and tonsils of Korean children subjected to tonsillectomy because of tonsil hyperplasia (n = 29). The microbiome profiles of saliva and tonsils were established via 16S rRNA gene sequencing. Based on the alpha diversity indices, the microbial communities of the two groups showed high similarities. According to Spearman’s ranking correlation analysis, the distribution of Treponema, the causative bacterium of periodontitis, in saliva and tonsils was found to have a significant positive correlation. Two representative microbes, Prevotella in saliva and Alloprevotella in tonsils, were negatively correlated, while Treponema 2 showed a strong positive correlation between saliva and tonsils. Taken together, strong similarities in the microbial communities of the tonsils and saliva are evident in terms of diversity and composition. The saliva microbiome is expected to significantly affect the tonsil microbiome. Furthermore, we suggest that our study creates an opportunity for tonsillar microbiome research to facilitate the development of novel microbiome-based therapeutic strategies.Subject terms: Comparative genomics, Metagenomics  相似文献   
6.
Central European Journal of Operations Research - Societal awareness and legislation changes concerning sustainability have affected how organizations generate value for stakeholders, as well as...  相似文献   
7.
Meccanica - Fiber reinforced materials are used in assorted engineering application and for this reason, new additive manufacturing technologies have been developed for this type of materials. With...  相似文献   
8.
Journal of Solid State Electrochemistry - In this study, galvanostatic electrolysis, through the use of the platinum supported on Ti (Ti/Pt) and Ti/TiO2-nanotubes/PbO2 anodes, was conducted in an...  相似文献   
9.
Zhang  Jia-Rui  Zhang  Jia-Qi  Zheng  Zhao-Lin  Lin  Da  Shen  Yu-Jia 《Nonlinear dynamics》2022,108(2):1005-1026
Nonlinear Dynamics - Parametrically excited oscillators are used in several domains, in particular to improve the dynamical behaviour of systems like in the case of the parametric amplification or...  相似文献   
10.
An innovative volatolomic approach employs the detection of biomarkers present in cerumen (earwax) to identify cattle intoxication by Stryphnodendron rotundifolium Mart., Fabaceae (popularly known as barbatimão). S. rotundifolium is a poisonous plant with the toxic compound undefined and widely distributed throughout the Brazilian territory. Cerumen samples from cattle of two local Brazilian breeds (‘Curraleiro Pé-Duro’ and ‘Pantaneiro’) were collected during an experimental intoxication protocol and analyzed using headspace (HS)/GC–MS followed by multivariate analysis (genetic algorithm for a partial least squares, cluster analysis, and classification and regression trees). A total of 106 volatile organic metabolites were identified in the cerumen samples of bovines. The intoxication by S. rotundifolium influenced the cerumen volatolomic profile of the bovines throughout the intoxication protocol. In this way, it was possible to detect biomarkers for cattle intoxication. Among the biomarkers, 2-octyldecanol and 9-tetradecen-1-ol were able to discriminate all samples between intoxicated and nonintoxicated bovines. The cattle intoxication diagnosis by S. rotundifolium was accomplished by applying the cerumen analysis using HS/GC–MS, in an easy, accurate, and noninvasive way. Thus, the proposed bioanalytical chromatography protocol is a useful tool in veterinary applications to determine this kind of intoxication.  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