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   892331篇
  免费   62431篇
  国内免费   2274篇
耳鼻咽喉   12451篇
儿科学   28546篇
妇产科学   26045篇
基础医学   125369篇
口腔科学   24638篇
临床医学   73887篇
内科学   180957篇
皮肤病学   18957篇
神经病学   70792篇
特种医学   36374篇
外国民族医学   336篇
外科学   141623篇
综合类   18973篇
一般理论   246篇
预防医学   63855篇
眼科学   20042篇
药学   63536篇
中国医学   1747篇
肿瘤学   48662篇
  2018年   8898篇
  2017年   7073篇
  2016年   7590篇
  2015年   8600篇
  2014年   12319篇
  2013年   19158篇
  2012年   25632篇
  2011年   27226篇
  2010年   16533篇
  2009年   15748篇
  2008年   26106篇
  2007年   27715篇
  2006年   27885篇
  2005年   27418篇
  2004年   26264篇
  2003年   25413篇
  2002年   24980篇
  2001年   41298篇
  2000年   42436篇
  1999年   36023篇
  1998年   9347篇
  1997年   8479篇
  1996年   8422篇
  1995年   8391篇
  1994年   8041篇
  1993年   7547篇
  1992年   28155篇
  1991年   26975篇
  1990年   26384篇
  1989年   25330篇
  1988年   23532篇
  1987年   23157篇
  1986年   22237篇
  1985年   21142篇
  1984年   15781篇
  1983年   13445篇
  1982年   8049篇
  1979年   14566篇
  1978年   10177篇
  1977年   8598篇
  1976年   8108篇
  1975年   8915篇
  1974年   10663篇
  1973年   10157篇
  1972年   9650篇
  1971年   8897篇
  1970年   8567篇
  1969年   8005篇
  1968年   7666篇
  1967年   7075篇
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
1.
Tympanic membranes (TM) that have healed spontaneously after perforation present abnormalities in their structural and mechanical properties; i.e., they are thickened and abnormally dense. These changes result in a deterioration of middle ear (ME) sound transmission, which is clinically presented as a conductive hearing loss (CHL). To fully understand the ME sound transmission under TM pathological conditions, we created a gerbil model with a controlled 50% pars tensa perforation, which was left to heal spontaneously for up to 4 weeks (TM perforations had fully sealed after 2 weeks). After the recovery period, the ME sound transmission, both in the forward and reverse directions, was directly measured with two-tone stimulation. Measurements were performed at the input, the ossicular chain, and output of the ME system, i.e., at the TM, umbo, and scala vestibuli (SV) next to the stapes. We found that variations in ME transmission in forward and reverse directions were not symmetric. In the forward direction, the ME pressure gain decreased in a frequency-dependent manner, with smaller loss (within 10 dB) at low frequencies and more dramatic loss at high frequency regions. The loss pattern was mainly from the less efficient acoustical to mechanical coupling between the TM and umbo, with little changes along the ossicular chain. In the reverse direction, the variations in these ears are relatively smaller. Our results provide detailed functional observations that explain CHL seen in clinical patients with abnormal TM, e.g., caused by otitis media, that have healed spontaneously after perforation or post-tympanoplasty, especially at high frequencies. In addition, our data demonstrate that changes in distortion product otoacoustic emissions (DPOAEs) result from altered ME transmission in both the forward and reverse direction by a reduction of the effective stimulus levels and less efficient transfer of DPs from the ME into the ear canal. This confirms that DPOAEs can be used to assess both the health of the cochlea and the middle ear.  相似文献   
2.
3.
IntroductionAlthough hyperferritinemia may reflect the inflammatory status of patients with non-alcoholic fatty liver disease (NAFLD), approximately 33% of hyperferritinemia cases reflect real hepatic iron overload.AimTo evaluate a non-invasive method for assessing mild iron overload in patients with NAFLD using 3T magnetic resonance imaging (MRI) relaxometry, serum hepcidin, and the expression of ferritin subunits.MethodsThis cross-sectional study assessed patients with biopsy-proven NAFLD. MRI relaxometry was performed using a 3T scanner in all patients, and the results were compared with iron content determined by liver biopsy. Ferritin, hepcidin, and ferritin subunits were assessed and classified according to ferritin levels and to siderosis identified by liver biopsy.ResultsA total of 67 patients with NAFLD were included in the study. MRI revealed mild iron overload in all patients (sensitivity, 73.5%; specificity, 70%). For mild (grade 1) siderosis, the transverse relaxation rate (R2*) threshold was 58.9 s?1 and the mean value was 72.5 s?1 (SD, 33.9), while for grades 2/3 it was 88.2 s?1 (SD, 31.9) (p < 0.001). The hepcidin threshold for siderosis was > 30.2 ng/mL (sensitivity, 87%; specificity, 82%). Ferritin H and ferritin L subunits were expressed similarly in patients with NAFLD, regardless of siderosis. There were no significant differences in laboratory test results between the groups, including glucose parameters and liver function tests.ConclusionsMRI relaxometry and serum hepcidin accurately assessed mild iron overload in patients with dysmetabolic iron overload syndrome.  相似文献   
4.
Graefe's Archive for Clinical and Experimental Ophthalmology - Ferromagnetic foreign bodies (FFB) present during magnetic resonance imaging (MRI) explorations can lead to tissue injury due to...  相似文献   
5.
Cancer Causes & Control - Circulating estrogens are an established risk factor for postmenopausal breast cancer (BCa). We describe the distribution of urinary estrogens, their metabolites, and...  相似文献   
6.
7.
Immunologic Research - Hyper immunoglobulin M (HIGM) syndrome is a rare disorder of the immune system with impaired antibody functions. The clinical picture of the patients varies according to the...  相似文献   
8.
9.
Assy  Z.  Bikker  F. J.  Picauly  O.  Brand  H. S. 《Clinical oral investigations》2022,26(2):1465-1475
Clinical Oral Investigations - Sjögren’s syndrome patients use different dry-mouth interventions for the relieve of their oral dryness. Recently, it was shown that patients with...  相似文献   
10.
AIDS and Behavior - Social biases may influence providers’ judgments related to pre-exposure prophylaxis (PrEP) and patients’ consequent PrEP access. US primary and HIV care providers...  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