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   2837篇
  免费   67篇
  国内免费   61篇
化学   676篇
晶体学   3篇
力学   7篇
综合类   11篇
数学   20篇
物理学   67篇
综合类   2181篇
  2023年   22篇
  2022年   107篇
  2021年   43篇
  2020年   86篇
  2019年   80篇
  2018年   67篇
  2017年   109篇
  2016年   50篇
  2015年   40篇
  2014年   142篇
  2013年   99篇
  2012年   157篇
  2011年   182篇
  2010年   150篇
  2009年   172篇
  2008年   186篇
  2007年   245篇
  2006年   198篇
  2005年   167篇
  2004年   158篇
  2003年   137篇
  2002年   114篇
  2001年   82篇
  2000年   60篇
  1999年   26篇
  1998年   20篇
  1997年   16篇
  1996年   15篇
  1995年   8篇
  1994年   10篇
  1993年   3篇
  1992年   3篇
  1991年   4篇
  1990年   1篇
  1989年   1篇
  1988年   3篇
  1985年   1篇
  1979年   1篇
排序方式: 共有2965条查询结果,搜索用时 15 毫秒
41.
四君子汤和四物汤微量元素含量研究   总被引:1,自引:0,他引:1  
通过了解中药“四君子汤”和“四物汤”中微量元素含量的异同,研讨了微量元素和中医“气血”理论之间的关系。实验表明,“四君子汤”和“四物汤”在微量元素的含量方面,有一定的类同和差异。该现象同中医的“气血”理论有非常相像的地方。同时发现中药中的微量元素在煎煮过程中,并不是同想象的一样匀速进入药液,而是不同的元素在不同的时间段不同的批次进入药液,这也提示中药煎法理论有一定依据。由于目前做的实验还少,本实验留下很多问题和疑点,值得进一步做有关的实验和研究。  相似文献   
42.
Ethnopharmacological relevanceMetabolic syndrome is closely related to the intestinal microbiota and disturbances in the host metabolome. Hyperuricemia (HUA), a manifestation of metabolic syndrome, can induce various cardiovascular diseases and gout, seriously affecting a patient’s quality of life. Astragalus membranaceus has a long history as a commonly used traditional Chinese medicine to treat kidney disease in China and East Asia.Materials and methodsWe compared the therapeutic effect of benzbromarone and two different doses Astragalus membranaceus ultrafine powder (AMUP) in rats with HUA. Ultra-performance liquid chromatography-mass spectrometer was used to analyze the AMUP metabolism in the plasma, urine, and feces. Further, 16S ribosome RNA sequencing and feces metabolomic were performed to capture the variation of the gut microbiota and metabolites changes before and after drug administration.ResultsAMUP had a notable impact on reducing blood uric acid levels while protecting the liver and kidney. Drug metabolism analysis demonstrated that effective constituent flavonoids are distributed in the blood, whereas saponins remain in the intestine. Gut microbiota analysis showed that low-dose AMUP ameliorated HUA-induced gut dysbiosis by reducing the abundance of harmful bacteria and increasing that of some beneficial bacteria with anti-inflammatory properties, such as Clostridia, Lachnospiraceae, and Muribaculaceae. In addition, HUA-induced changes in metabolite contents in bile acid and adrenal hormone biosynthesis pathways were restored after treatment with AMUP.ConclusionLow-dose AMUP exerts remarkable therapeutic effects on HUA by regulating the gut microbiome and mediating gut metabolism pathways associated with uric acid excretion.  相似文献   
43.
张玉奎 《色谱》2004,22(4):301-305
The separation and identification of complex samples is an urgent task that analytical chemistry has to face. Chromatography, as an important analysis technique, has been widely applied to many fields, such as life science, environment, medicine, food and petrochemical engineering.Recently, with the progress of science and tech-  相似文献   
44.
化学模式识别技术评价中药厚朴质量的研究   总被引:1,自引:0,他引:1  
本文对不同产地和市售的二十四种厚朴药材及饮片的萃取液进行了高效液相色谱、气相色谱及紫外光谱分析;对所得数据用主成分分析进行分类,概括出不同样品化学成分的异同,认为大叶木兰可做为厚朴的代用品,而在陕西安康购得的样品不应做厚朴使用,后者经生药学鉴定为厚朴伪品凹叶木兰。化学模式识别技术可为寻找药材的代用品、评价中药质量及鉴定伪劣药材提供依据。  相似文献   
45.
Two natural products databases, the marine natural products database (MNPD) and the traditional Chinese medicines database (TCMD), were used to find novel structures of potent SARS-CoV protease inhibitors through virtual screening. Before the procedure, the databases were filtered by Lipinski's ROF and Xu's extension rules. The results were analyzed by statistic methods to eliminate the bias in target-based database screening toward higher molecular weight compounds for enhancing the hit rate. Eighteen lead compounds were recommended by the screening procedure. They were useful for experimental scientists in prioritizing drug candidates and studying the interaction mechanism. The binding mechanism was also analyzed between the best screening compound and the SARS protein.  相似文献   
46.
In this study, a fingerprint-activity relationship modeling between chemical fingerprints and antirheumatic activity was established, and multivariate statistical analysis was used to evaluate the quality of Taxilli Herba (TH) from different hosts. Characteristic fingerprints of 20 batches of TH samples were generated by high-performance liquid chromatography coupled with triple quadrupole-time of flight tandem mass spectrometry (HPLC-Triple TOF-MS/MS), and the similarity analysis was calculated based on thirteen common characteristic peaks by hierarchical clustering analysis (HCA). Subsequently, nine efficacy markers were discovered by combining fingerprints and antirheumatic activity through grey correlation analysis (GCA) and bivariate correlation analysis (BCA). Meanwhile, the content of 5 constituents in 9 markers was determined by high-performance liquid chromatography coupled with triple quadrupole-linear ion trap tandem mass spectrometry (HPLC-QTRAP-MS/MS). The comprehensive quality of TH was assessed using multivariate statistical analysis, including principal components analysis (PCA) and technique for order preference by similarity to ideal solution (TOPSIS). The results showed that a high dose of TH extract could markedly ameliorate arthritis damage compared to other doses, with flavonoids playing an important role in the antirheumatic activity. The comprehensive quality of samples from Morus alba L. (SS) was superior to those from Liquidambar formosana Hance (FXS). The present study will demonstrate the markers associated with efficacy, and provide an applicable strategy for more comprehensive quality control and evaluation of TH.  相似文献   
47.
论述了数字图书馆的含义,对数字图书馆与传统图书馆的关系进行了分析,并探讨了怎样构建数字图书馆。  相似文献   
48.
民族地区政府应充分利用政府行为推动民族传统文化知识产权保护立法,实现传统文化的法制化保护.应采取行政措施抢救,传承,开发,创新,发展民族传统文化,同时,民族地区政府作为民族传统文化权利主体的法定代表,应对他人的侵权行为行使救济权,维护民族传统文化权利主体利益.  相似文献   
49.
传统美德是中华民族优良道德品质、优良民族精神、崇高民族气节、高尚民族情感、良好民族礼仪的总和,也是我们民族精神的精髓。在改革开放、建立社会主义市场经济、建设有中国特色的社会主义的新形势下,如何继承和发扬中华民族传统美德,改进和加强学校的德育工作,培养德才兼备的跨世纪新人,是中学历史教学面临的挑战。  相似文献   
50.
工程机械零件的可靠性优化设计   总被引:2,自引:0,他引:2  
通过对机械产品可靠性的评价,分析了传统设计方法与可靠性设计方法在设计思想、设计原理上的区别.运用可靠性理论与最优化设计技术,提出了机械零部件的可靠性优化设计方法.在满足可靠度约束及结构几何约束的条件下,以体积最小作为优化目标函数进行可靠性优化设计,得到了比常规设计更为合理的设计结果.  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