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   5970篇
  免费   345篇
  国内免费   26篇
耳鼻咽喉   20篇
儿科学   170篇
妇产科学   143篇
基础医学   792篇
口腔科学   94篇
临床医学   359篇
内科学   1547篇
皮肤病学   191篇
神经病学   345篇
特种医学   218篇
外科学   1209篇
综合类   14篇
预防医学   138篇
眼科学   63篇
药学   261篇
中国医学   1篇
肿瘤学   776篇
  2023年   57篇
  2022年   104篇
  2021年   162篇
  2020年   71篇
  2019年   97篇
  2018年   139篇
  2017年   117篇
  2016年   144篇
  2015年   175篇
  2014年   174篇
  2013年   230篇
  2012年   387篇
  2011年   417篇
  2010年   210篇
  2009年   207篇
  2008年   391篇
  2007年   367篇
  2006年   428篇
  2005年   363篇
  2004年   391篇
  2003年   378篇
  2002年   379篇
  2001年   80篇
  2000年   58篇
  1999年   78篇
  1998年   88篇
  1997年   76篇
  1996年   70篇
  1995年   56篇
  1994年   61篇
  1993年   54篇
  1992年   37篇
  1991年   48篇
  1990年   38篇
  1989年   28篇
  1988年   22篇
  1987年   16篇
  1986年   16篇
  1985年   8篇
  1984年   16篇
  1983年   12篇
  1982年   6篇
  1981年   14篇
  1980年   5篇
  1979年   9篇
  1978年   11篇
  1977年   9篇
  1976年   5篇
  1975年   5篇
  1973年   8篇
排序方式: 共有6341条查询结果,搜索用时 156 毫秒
91.
Purpose: To assess the associations of the natural environment with obesity and physical activity in nonmetropolitan areas of the United States among representative samples by using 2 indices of outdoor activity potential (OAP) at the county level. Methods: We used the data from 457,820 and 473,296 noninstitutionalized adults aged over 18 years for obesity and physical activity, respectively, from the 2000‐2006 Behavioral Risk Factor Surveillance System. The OAP indices were (1) a recreational opportunity index based on 24 variables related to outdoor physical activity, such as the number of facilities available for walking, biking, hiking, and swimming derived from the 1997 National Outdoor Recreation Supply Information System; and (2) a natural amenities index which was based on physical and social environmental characteristics, such as climate, topographic relief, land cover, and tourism. We fitted logistic regression models using generalized estimating equations to control for county level intracorrelation and tested each index separately to assess its relationship with obesity and physical activity. Findings: Recreational opportunities were higher in areas with greater natural amenities. After controlling for individual‐level socioeconomic and demographic characteristics, the prevalence of obesity decreased and propensity for physical activity increased with increasing levels of both recreational opportunities and natural amenities. Conclusions: Multiple indices of OAP based on characteristics of the built, natural and social environments were associated with decreased obesity and increased physical activity in nonmetropolitan areas. Public health interventions should consider the opportunities and limitations offered by the natural environment for promoting physical activity and reducing obesity in rural areas.  相似文献   
92.
Orofacial cold hyperalgesia is known to cause severe persistent pain in the face following trigeminal nerve injury or inflammation, and transient receptor potential (TRP) vanilloid 1 (TRPV1) and TRP ankylin 1 (TRPA1) are thought to be involved in cold hyperalgesia. However, how these two receptors are involved in cold hyperalgesia is not fully understood. To clarify the mechanisms underlying facial cold hyperalgesia, nocifensive behaviors to cold stimulation, the expression of TRPV1 and TRPA1 in trigeminal ganglion (TG) neurons, and TG neuronal excitability to cold stimulation following facial capsaicin injection were examined in rats. The head‐withdrawal reflex threshold (HWRT) to cold stimulation of the lateral facial skin was significantly decreased following facial capsaicin injection. This reduction of HWRT was significantly recovered following local injection of TRPV1 antagonist as well as TRPA1 antagonist. Approximately 30% of TG neurons innervating the lateral facial skin expressed both TRPV1 and TRPA1, and about 64% of TRPA1‐positive neurons also expressed TRPV1. The TG neuronal excitability to noxious cold stimulation was significantly increased following facial capsaicin injection and this increase was recovered by pretreatment with TRPA1 antagonist. These findings suggest that TRPA1 sensitization via TRPV1 signaling in TG neurons is involved in cold hyperalgesia following facial skin capsaicin injection.  相似文献   
93.
94.
95.
96.
We investigated whether it was possible to predict the prognosis of fetuses with cystic hygroma in early pregnancy based on the degree of neck thickening. We retrospectively analyzed 57 singleton pregnancies with fetuses with cystic hygroma who were examined before the 22nd week of pregnancy. The fetuses were categorized according to the outcome, structural abnormalities at birth, and chromosomal abnormalities. Here, we proposed a new sonographic predictor with which we assessed neck thickening by dividing the width of the neck thickening by the biparietal diameter, which is expressed as the cystic hygroma width/biparietal diameter ratio. The median cystic hygroma width/biparietal diameter ratio in the intrauterine fetal death group (0.51) was significantly higher than that in the live birth group (0.27). No significant difference in the median cystic hygroma width/biparietal diameter ratio was found between the structural abnormalities group at birth and the no structural abnormalities group, and no significant difference in the median cystic hygroma width/biparietal diameter ratio was found between the chromosomal abnormality group and the no chromosomal abnormality group. We used receiver operating characteristic analysis to evaluate the cystic hygroma width/biparietal diameter ratio to predict intrauterine fetal death. When the cystic hygroma width/biparietal diameter ratio cut‐off value was 0.5, intrauterine fetal death could be predicted with a sensitivity of 52.9% and a specificity of 100%. It is possible to predict intrauterine fetal death in fetuses with cystic hygroma in early pregnancy if cystic hygroma width/biparietal diameter ratio is measured. However, even if cystic hygroma width/biparietal diameter ratio is measured, predicting the presence or absence of a structural abnormality at birth or a chromosomal abnormality is difficult.  相似文献   
97.
98.
99.
100.
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