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   5610篇
  免费   301篇
  国内免费   58篇
耳鼻咽喉   54篇
儿科学   169篇
妇产科学   67篇
基础医学   679篇
口腔科学   156篇
临床医学   403篇
内科学   1657篇
皮肤病学   88篇
神经病学   406篇
特种医学   265篇
外科学   914篇
综合类   33篇
一般理论   1篇
预防医学   176篇
眼科学   77篇
药学   308篇
中国医学   8篇
肿瘤学   508篇
  2023年   47篇
  2022年   99篇
  2021年   193篇
  2020年   95篇
  2019年   132篇
  2018年   137篇
  2017年   110篇
  2016年   130篇
  2015年   152篇
  2014年   161篇
  2013年   211篇
  2012年   322篇
  2011年   328篇
  2010年   177篇
  2009年   187篇
  2008年   294篇
  2007年   321篇
  2006年   264篇
  2005年   266篇
  2004年   226篇
  2003年   207篇
  2002年   226篇
  2001年   124篇
  2000年   128篇
  1999年   121篇
  1998年   81篇
  1997年   37篇
  1996年   49篇
  1995年   41篇
  1994年   31篇
  1993年   35篇
  1992年   87篇
  1991年   82篇
  1990年   83篇
  1989年   70篇
  1988年   65篇
  1987年   72篇
  1986年   71篇
  1985年   64篇
  1984年   50篇
  1983年   36篇
  1982年   19篇
  1979年   49篇
  1977年   28篇
  1975年   26篇
  1974年   27篇
  1973年   20篇
  1972年   23篇
  1971年   21篇
  1969年   18篇
排序方式: 共有5969条查询结果,搜索用时 15 毫秒
71.
72.
We treated 18 patients with chronic hepatitis C by recombinant interferon-α (6 MIU for 24 weeks). In seven patients, serum aminotransferase levels declined to normal (responders). To evaluate the effect of interferon on matrix metalloproteinases (MMPs) and their inhibitors, namely tissue inhibitors of metalloproteinases (TIMPs), the serum levels of these enzymes were determined by enzyme immunoassay (EIA) using a specific monoclonal antibody. In responders, there was a tendency, but not a significant one, towards either an increase in serum MMP 1 levels or a decrease in serum TIMP 1 levels. In contrast, in nonresponders, both a significant decrease in MMP 1 and MMP 3 and a significant increase in TIMP 1 were observed. The number of cases of either increase in serum MMP levels or decrease in serum TIMP levels was significantly larger in responders than in nonresponders. Furthermore, the ratio of MMP 1 to TIMP 1 significantly increased in responders, suggesting that the balance between matrix formation and degradation in hepatic fibrosis tended to move toward degradation. These data indicate that interferon may exert a beneficial effect on hepatic fibrosis in parallel with improvement of aminotransferase activity.  相似文献   
73.
OBJECTIVE: To determine an appropriate duration for a short course of oral steroids in cases of asthma exacerbations. SETTING: A 1,000 bed city hospital in Kobe, Japan. PATIENTS: Patients with asthma exacerbations who needed hospital admission. METHODS: Following an initial treatment with a 3-day course of intravenous methylprednisolone, patients were allocated to either a 1-week (1 W) or a 2-week (2 W) course of oral prednisolone (PSL, 0.5 mg/kg). OUTCOME MEASURES: Peak expiratory flow rate (PEF) and rate of unscheduled hospital visits and readmission. RESULTS: Twenty patients were enrolled (10 in 1 W, 10 in 2 W). Mean PEF just before starting oral PSL in 1 W and 2 W were 51 and 58% of each patient's best value. PEF was significantly improved and to a similar degree over the course of time in both 1 W and 2 W. The frequency of unexpected hospital visits during a 3-month period after discharge was similar (2 in 1 W and 2 in 2 W). No readmission occurred during the same period. CONCLUSIONS: Because both the 1-week and the 2-week course of oral PSL were equally effective in the treatment of asthma exacerbations, 1 week may be appropriate as the maximum duration of a short rescue course of oral steroids.  相似文献   
74.
75.
Annals of Nuclear Medicine - Albumin–globulin ratio (AGR), which is calculated by dividing serum albumin by serum globulin, is considered as a cancer-related inflammation biomarker. Although...  相似文献   
76.
77.
78.
BACKGROUND AND PURPOSE:Inflammation and degeneration of the intracranial saccular aneurysm wall play a major role in aneurysm formation, development and subsequent rupture. The aim of this study was to characterize the walls of unruptured intracranial aneurysms by using a hybrid of opposite-contrast MRA at 3T.MATERIALS AND METHODS:Fourteen consecutive patients with 17 unruptured intracranial aneurysms who initially underwent clipping surgery were prospectively evaluated. All aneurysms were scanned preoperatively by using a hybrid of opposite-contrast MRA in 3T high-resolution MR imaging. We classified intraoperative findings of atherosclerotic plaques in the aneurysms into 3 grades: grade A (major plaques), grade B (minor plaques), and grade C (no plaques). The contrast ratio of the high-intensity area was also measured relative to the background low-intensity area inside the carotid artery.RESULTS:Findings from preoperative plaque imaging of the aneurysm corresponded to the intraoperative findings in 15 of 16 aneurysms (excluding 1 that was impossible to visualize in its entirety due to anatomic reasons). Overall sensitivity and specificity of the hybrid of opposite-contrast MRA were 88.9% and 100%, respectively. During the operation, 4 aneurysms were classified as grade A; 5, as grade B; and 7, as grade C. The means of the contrast ratio for grades A, B, and C were 0.72 ± 0.03, 0.34 ± 0.30, and −0.02 ± 0.09, respectively.CONCLUSIONS:The hybrid of opposite-contrast MRA can detect visible atherosclerotic plaques in the unruptured aneurysm wall, and the contrast ratio in intracranial aneurysms correlated with their presence and extent. A study including a larger series is needed to validate the diagnostic potential of this imaging technique.

Intracranial aneurysms are common vascular lesions, often consisting of a saccular dilation of a cerebral artery vessel. The prevalence of intracranial aneurysms in the general population is estimated between 2.5% and 5%.1,2 Aneurysmal rupture occurs with a 1% risk per year, depending on the size, location, and morphometry of the aneurysm, and leads to subarachnoid hemorrhage with associated high morbidity and mortality rates.1,2 Intracranial aneurysms with an estimated high risk of rupture undergo management via a surgical or endovascular approach, depending on the specific risks of treatment.3,4 Therefore, it is important to accurately assess the risk of aneurysmal rupture.The pathogenesis of intracranial aneurysms and their natural history are not well-understood. Histopathologic studies have shown that the infiltration of inflammatory cells and the degeneration of the aneurysm wall with atherosclerosis correlates with the formation, development, and rupture risk of cerebral aneurysms.59 However, characterization of the aneurysm wall is limited by imaging data quality and the need to harvest surgical specimens.In this regard, the characteristics of high-field-strength MR imaging, which has a favorable SNR and changes in relaxation time and susceptibility, can depict the intracranial vessel walls and their pathologies, including small vessels with atherosclerosis.10,11The hybrid of opposite-contrast MR angiography (HOP-MRA) used in this study is a modern technique that combines the advantages of 3D TOF MRA and flow-sensitive black-blood (FSBB) MRA.12 The clinical efficacy of this technique was established to improve the visualization of peripheral vessels.13,14 Theoretically, tissue with shorter T1 and T2* introduces high signal in FSBB of HOP-MRA, which demonstrates atherosclerotic plaques, including fat, as high-signal-intensity areas and demonstrates the blood space as low-signal-intensity areas in intracranial aneurysms.12 The strength of this technique is the dual-echo 3D gradient-echo sequence, which enables a shorter imaging time and minimization of misregistration. The present study investigated the utility of HOP-MRA at 3T for the characterization of visible atherosclerotic plaques in intracranial aneurysms by using subtraction between TOF and FSBB imaging.  相似文献   
79.
80.
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