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   254145篇
  免费   22439篇
  国内免费   14379篇
耳鼻咽喉   2300篇
儿科学   3123篇
妇产科学   5030篇
基础医学   29365篇
口腔科学   4380篇
临床医学   32797篇
内科学   41181篇
皮肤病学   2975篇
神经病学   14066篇
特种医学   8816篇
外国民族医学   105篇
外科学   27789篇
综合类   36259篇
现状与发展   56篇
一般理论   45篇
预防医学   15942篇
眼科学   6925篇
药学   25457篇
  271篇
中国医学   11936篇
肿瘤学   22145篇
  2024年   3095篇
  2023年   4877篇
  2022年   9544篇
  2021年   12277篇
  2020年   9470篇
  2019年   7949篇
  2018年   8358篇
  2017年   7435篇
  2016年   7000篇
  2015年   10557篇
  2014年   13295篇
  2013年   12404篇
  2012年   18150篇
  2011年   19773篇
  2010年   12122篇
  2009年   9703篇
  2008年   13141篇
  2007年   13162篇
  2006年   12695篇
  2005年   12689篇
  2004年   8767篇
  2003年   7809篇
  2002年   6773篇
  2001年   6102篇
  2000年   6198篇
  1999年   6508篇
  1998年   3710篇
  1997年   3726篇
  1996年   2846篇
  1995年   2611篇
  1994年   2258篇
  1993年   1509篇
  1992年   2297篇
  1991年   2007篇
  1990年   1672篇
  1989年   1460篇
  1988年   1265篇
  1987年   1181篇
  1986年   943篇
  1985年   748篇
  1984年   491篇
  1983年   381篇
  1982年   226篇
  1981年   201篇
  1980年   191篇
  1979年   244篇
  1978年   141篇
  1977年   112篇
  1976年   97篇
  1974年   116篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
PM10 exposure has been found to have significant effects on a variety of physical conditions. However, whether it acts on psychopathology remains unclear. This study used 8-year data to examine the relationship between PM10 concentration and daily clinic visits of anxiety disorders. All residents of Yunlin County, Taiwan, which is a high river-dust exposure area, were selected as subjects. Data from the Taiwan National Health Insurance Research Database (NHIRD), 2002–2009, were analyzed. Individuals with any ICD code of 300.0 and 300.2 were categorized as with anxiety disorders. PM10 data were based on the Lunbei station (located at Yunlin County) of EPA, Taiwan. Time-series analysis showed that, during the observed 8 years, the number of daily clinic visits for anxiety disorders increased with PM10 levels, and the relationship remained significant after unemployment rate, and the Weighted Price Index of Taiwan Stock Exchange in the same period were controlled for. In particular, we found that there is a linear dose-response effect between daily clinic visits and PM10 levels when PM10 <?300 μg/m3; whereas a dramatically elevated daily clinic visits of anxiety disorders was found when PM10 >?300 μg/m3. Findings from this study highlight that high level of PM10 exposure derived from severe weather or environment condition may affect the occurrence of anxiety disorders. In addition, there seems to have a threshold of PM10 in elevating the risk of anxiety disorders.  相似文献   
42.
43.
We have developed a new set of lyophilized kits, composed of 3 different kits, for the instant preparation of no‐carrier‐added 131I‐MIBG in the clinic. We here discussed the formulation of the kits, optimization of radiolabelling, quality control of radiolabeled 131I‐MIBG, and studies of animal biodistribution. The no‐carrier‐added (nca) 131I‐MIBG injection could be prepared within 30 minutes in the clinic with the help of the lyophilized kits. The radiochemical purity and specific activity (SA) could achieve above 98% and 6700 MBq/mg, respectively.  相似文献   
44.
Abstract

Glycosylation is an effective approach to improve the druggability of natural products by increasing their water solubility. In this work, we report the glycosylation of oleanane-type triterpenoids by a recombinant microbial glycosyltransferase YjiC1. A preliminary screening test indicated YjiC1 exhibited robust capabilities for O-glycosylation of triterpenoids, based on LC/MS analysis. Among the products, two new compounds (2a and 3a), together with a known one (1a), were isolated and characterized. These products exhibited improved water solubility, and 3a showed moderate anti-HIV activities at 100 μM. This reaction provides a facile and efficient approach to synthesize the glucosides of triterpenoids.  相似文献   
45.
Abstract

Glucuronidation is an important and popular metabolic reaction in vivo of drugs. The further evaluation of biological activity and toxicity of glucuronides is necessary in the course of the drug research and development. However, the synthesis of glucuronides is limited by the lack of efficient approach. Herein, we have developed a new glucuronide synthesis method using plant uridine diphosphate-dependent glucuronosyltransferases (UGTs), UGT88D4, UGT88D7, and EpGT8, enabling the convenient preparation for corresponding O-glucuronide metabolites (1a, 2a, 3a, and 3b) in milligram scale of two neurological active agents, IMM-H004 (1) and FLZ (2). Their structures were characterized by spectroscopic data analyses.  相似文献   
46.
Two new saponins, notoginsenosides Ng1 (1) and Ng2 (2), together with seven known compounds (3–9), were isolated from the leaves of Panax notoginseng. Their structures were elucidated by UV, IR, HRESIMS, and NMR experiments. Compounds 6 and 7 showed moderate cytotoxic activities against HCT-116, with IC50 values of 4.98 and 0.64 μmol/L, respectively.  相似文献   
47.
A new homoisoflavanone, (3R)-5-hydroxy-7-methoxyl-3-(2′-hydroxy-4′- methoxybenzyl)-chroman-4-one (1), together with six known analogs, were isolated from the rhizomes of Polygonatum sibiricum. Their structures were elucidated on the basis of extensive spectroscopic analysis. All compounds were tested for their estrogenic activity using the MCF-7 estrogenresponsive human breast cancer cell lines. At a dose of 0.1 μmol/L, compounds 17 exhibited significant proliferative effects on MCF-7 cells compared with E2. The molecular docking study results indicated that the activity of compounds 3, 5, 6, and 7 may be the binding with ERR.  相似文献   
48.
Yang  Luo-Ping  Gu  Xiao-Long  Chen  Jin-Xiang  Yang  Jie  Tan  Sui-Yi  Duan  Wen-Jun 《Journal of natural medicines》2018,72(3):808-815
Journal of Natural Medicines - Two new dyhydrophaseic acid glucoside isomers, (1′S, 3′R, 5′S, 8′R, 2Z, 4E)-dihydrophaseic acid-3′-O-β-d-glucopyranoside (2) and...  相似文献   
49.
Two new secoiridoid glucosides, ilexpublignoside (1), pubzenoside (2), and a new lignan, ilexlignan B (3), along with seven known compounds (4–10) were isolated from the roots of Ilex pubescens for the first time. Their chemical structures were elucidated on the basis of extensive spectroscopic methods, including IR, UV, HR-ESI–MS, CD, NMR experiments, as well as comparison with the reported data.  相似文献   
50.
目的 掌握广西辖区内糖厂密封放射源的使用分布情况,评价密封放射源对周围环境、职业人员、公众成员产生的辐射影响,为今后糖厂放射源的使用管理提供科学依据。方法 按监测规范合理布点,利用γ辐射剂量率仪对广西区内所有使用密封放射源的糖厂开展辐射环境现场测量,根据监测结果进行估算,并结合个人剂量监测结果进行分析。结果 密封放射源使用场所周围辐射剂量率高于环境本底水平,职业人员、公众成员会受到一定的辐射剂量。结论 职业人员及公众成员年有效剂量结果符合相关要求。  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