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   356581篇
  免费   23393篇
  国内免费   7850篇
耳鼻咽喉   4139篇
儿科学   9632篇
妇产科学   6736篇
基础医学   29192篇
口腔科学   9957篇
临床医学   39070篇
内科学   42849篇
皮肤病学   4594篇
神经病学   19518篇
特种医学   9584篇
外国民族医学   31篇
外科学   44208篇
综合类   52673篇
现状与发展   13篇
一般理论   29篇
预防医学   34794篇
眼科学   5258篇
药学   30500篇
  392篇
中国医学   31090篇
肿瘤学   13565篇
  2023年   5747篇
  2022年   9502篇
  2021年   14230篇
  2020年   13219篇
  2019年   18849篇
  2018年   16622篇
  2017年   13452篇
  2016年   10814篇
  2015年   10121篇
  2014年   21125篇
  2013年   22578篇
  2012年   19046篇
  2011年   20654篇
  2010年   16625篇
  2009年   15283篇
  2008年   14853篇
  2007年   15318篇
  2006年   13438篇
  2005年   11596篇
  2004年   9574篇
  2003年   8316篇
  2002年   6540篇
  2001年   5877篇
  2000年   4851篇
  1999年   4245篇
  1998年   3438篇
  1997年   3287篇
  1996年   2794篇
  1995年   2693篇
  1994年   2562篇
  1993年   2067篇
  1992年   2088篇
  1991年   1784篇
  1990年   1579篇
  1989年   1417篇
  1988年   1348篇
  1987年   1167篇
  1985年   3812篇
  1984年   4831篇
  1983年   3378篇
  1982年   3838篇
  1981年   3574篇
  1980年   3171篇
  1979年   2922篇
  1978年   2550篇
  1977年   1919篇
  1976年   2165篇
  1975年   1641篇
  1974年   1432篇
  1973年   1280篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
目的 建立蒙药绿松石的质量标准。方法 收集不同产地绿松石,共10批。观察绿松石样品和粉末的性状并进行理化鉴别;按2020年版《中国药典》(四部)通则方法测定绿松石样品中水分、浸出物含量;采用原子吸收光谱法测定绿松石样品铜元素含量。结果 绿松石为不规则、周围带有黑石的块状物,表面蓝绿色,体重,质硬脆,难砸碎,断面呈贝壳状,蜡样光泽,粉末呈灰绿色,无臭,味淡;理化鉴别结果显示,呈铜盐反应;10批次样品中水分含量为0.41%-3.94%(SD=1.37%),浸出物含量为0.21%-0.81%(SD=0.21%),铜元素含量为3.03%-4.63%(SD=0.63%)。结论 初步拟定绿松石中水分含量不得超多5.0%、浸出物含量不得低于0.10%,铜元素含量应为2.60%-4.84%,制定的标准可用于蒙药材绿松石的质量控制。  相似文献   
3.
4.
5.
6.
IntroductionDetailed data on clinical characteristics in children with the omicron strain of SARS-COV-2 are limited.MethodsWe conducted a retrospective observational study of children with COVID-19 at the National Center for Child Health and Development to evaluate the clinical manifestations during and before the emergence of the omicron variant. Only symptomatic patients without underlying diseases were included. Participants were divided into two temporal groups: the “omicron era” (1/2022–2/2022) and the “pre-omicron era,” where the delta variant predominated (7/2021–11/2021). The patients were subclassified into an older vaccine-eligible group (aged 12–17 years), a younger vaccine-eligible group (aged 5–11 years), and a vaccine-ineligible group (aged 0–4 years).ResultsWe compared 113 patients in the omicron era with 106 in the pre-omicron era. Most patients in both eras had non-severe disease, and no patients required mechanical ventilation or died. Among patients aged 0–4 years, sore throat and hoarseness were more common during the omicron era than the pre-omicron era (11.1% vs. 0.0% and 11.1% vs. 1.5%, respectively). Croup syndrome was diagnosed in all patients with hoarseness. Among patients aged 5–11 years, vomiting was more frequent during the omicron era (47.2%) than during the pre-omicron era (21.7%). Cough and rhinorrhea were less common during the omicron era in patients aged 0–4 and 5–11 years, respectively, than during the pre-omicron era.ConclusionsIn children with COVID-19, clinical manifestations differed between the omicron and pre-omicron eras. In the Omicron era, croup syndrome was more frequent in vaccine-ineligible children.  相似文献   
7.
8.
BackgroundThe goal of this study was to characterize contemporary performance benchmarks and risk factors associated with negative appendectomy (NA) in children with suspected appendicitis.MethodsA multicenter retrospective cohort analysis of children undergoing appendectomy for suspected appendicitis was performed using data from the 2016–2021 NSQIP-Pediatric Appendectomy Targeted Public Use Files. Multivariable regression was used to evaluate the influence of year, age, sex, and WBC count on NA rate, and to generate rate estimates for NA based on different combinations of demographic characteristics and WBC profiles.Results100,322 patients were included from 140 hospitals. The overall NA rate was 2.4%, and rates decreased significantly during the study period (2016: 3.1% vs. 2021: 2.3%, p < 0.001). In adjusted analyses, the highest risk for NA was associated with a normal WBC (<9000/mm3; OR 5.31 [95% CI: 4.87–5.80]), followed by female sex (OR 1.55 [95% CI: 1.42–1.68]) and age <5 years (OR 1.64 [95% CI 1.39, 1.94]). Model-estimated risk for NA varied significantly across demographic and WBC strata, with a 14.4-fold range in rates between subgroups with the lowest and highest predicted risk (males 13–17 years with elevated WBC [1.1%] vs. females 3–4 years with normal WBC [15.8%]).ConclusionsContemporary NA rates have decreased over time, however NA risk remains high in children without a leukocytosis, particularly for girls and children <5 years of age. These data provide contemporary performance benchmarks for NA in children with suspected appendicitis and identify high-risk populations where further efforts to mitigate NA risk should be targeted.Level of EvidenceIII.  相似文献   
9.
10.
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