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   1561篇
  免费   119篇
  国内免费   10篇
耳鼻咽喉   3篇
儿科学   45篇
妇产科学   49篇
基础医学   214篇
口腔科学   40篇
临床医学   146篇
内科学   358篇
皮肤病学   26篇
神经病学   145篇
特种医学   25篇
外科学   186篇
综合类   9篇
预防医学   194篇
眼科学   13篇
药学   122篇
中国医学   19篇
肿瘤学   96篇
  2023年   12篇
  2022年   27篇
  2021年   55篇
  2020年   33篇
  2019年   59篇
  2018年   63篇
  2017年   41篇
  2016年   42篇
  2015年   44篇
  2014年   76篇
  2013年   90篇
  2012年   99篇
  2011年   104篇
  2010年   73篇
  2009年   55篇
  2008年   81篇
  2007年   74篇
  2006年   84篇
  2005年   82篇
  2004年   74篇
  2003年   55篇
  2002年   66篇
  2001年   29篇
  2000年   33篇
  1999年   36篇
  1998年   11篇
  1997年   13篇
  1996年   11篇
  1994年   9篇
  1992年   10篇
  1991年   9篇
  1990年   8篇
  1989年   12篇
  1988年   7篇
  1987年   7篇
  1986年   8篇
  1985年   7篇
  1984年   4篇
  1983年   6篇
  1979年   6篇
  1976年   6篇
  1975年   4篇
  1974年   4篇
  1973年   6篇
  1972年   6篇
  1970年   8篇
  1969年   7篇
  1968年   5篇
  1967年   6篇
  1966年   6篇
排序方式: 共有1690条查询结果,搜索用时 15 毫秒
141.
The current pandemic SARS-CoV-2 has required an unusual allocation of resources that can negatively impact chronically ill patients and high-complexity procedures. Across the European Reference Network on Pediatric Transplantation (ERN TransplantChild), we conducted a survey to investigate the impact of the COVID-19 outbreak on pediatric transplant activity and healthcare practices in both solid organ transplantation (SOT) and hematopoietic stem cell transplantation (HSCT). The replies of 30 professionals from 18 centers in Europe were collected. Twelve of 18 centers (67%) showed a reduction in their usual transplant activity. Additionally, outpatient visits have been modified and restricted to selected ones, and the use of telemedicine tools has increased. Additionally, a total of 14 COVID-19 pediatric transplanted patients were identified at the time of the survey, including eight transplant recipients and six candidates for transplantation. Only two moderate-severe cases were reported, both in HSCT setting. These survey results demonstrate the limitations in healthcare resources for pediatric transplantation patients during early stages of this pandemic. COVID-19 disease is a major worldwide challenge for the field of pediatric transplantation, where there will be a need for systematic data collection, encouraging regular discussions to address the long-term consequences for pediatric transplantation candidates, recipients, and their families.  相似文献   
142.
Recurrent aphthous stomatitis.   总被引:3,自引:0,他引:3  
Etiology and Epidemiology: The Greek term aphthai was initially used in relation to disorders of the mouth and is credited to Hippocrates (460-370 BC). Today, recurrent aphthous ulceration, or recurrent aphthous stomatitis (RAS), is recognized as the most common oral mucosal disease known to human beings. Considerable research attention has been devoted to elucidating the causes of RAS; local and systemic conditions, and genetic, immunologic, and infectious microbial factors all have been identified as potential etiopathogenic agents (Table 1). However, to date, no principal etiology has been discovered. Epidemiologic studies indicate that the prevalence of RAS is between 2% and 50% in the general population; most estimates fall between 5% and 25%. In selected groups, such as medical and dental students, it has been observed with a frequency as high as 50% to 60%. The peak age of onset for RAS is between 10 and 19 years. After childhood and adolescence, it may continue throughout the entire human lifespan without geographic or age-, sex-, or race-related preference.  相似文献   
143.
BACKGROUND: Using a single cutpoint for the free-to-total (F/T) prostate specific antigen (PSA) ratio loses important diagnostic information. We evaluated the performance of multiple F/T PSA cutpoints in detecting prostate cancer in men with nonspecific PSA values. METHODS: We extracted sensitivity and specificity data from 12 studies reporting on >or=30 cancer patients with PSA values between 2.0 and 10.0 ng/mL. We calculated stratum-specific likelihood ratios (LR) and areas under the receiver operating characteristic (ROC) curves. RESULTS: Multiple cutpoints for the F/T PSA ratio significantly increased the area under the ROC (0.70) compared with the single investigator-selected cutpoint (0.62), P < 0.004. The LR for the most positive cutpoint stratum (2.62) was significantly higher than the LR for a positive test from the single cutpoint (1.36), P < 0.004. CONCLUSIONS: Using multiple cutpoints increased the discriminating power of the F/T PSA ratio and led to greater probability revisions in the most positive test-result strata.  相似文献   
144.
145.
146.
147.
BACKGROUND: Several different types of needles for transbronchial needle aspiration (TBNA) exist in the market. Recently, the eXcelon transbronchial needle (Boston Scientific, Boston, Mass., USA) was commercialized, and to our knowledge, no comparative studies with other types of needles have been performed up to date. OBJECTIVES: The aim of the present study was to determine the diagnostic yield and safety of the 21-gauge eXcelon transbronchial needle in the diagnosis of mediastinal lesions and to compare it with a 22-gauge Wang cytology needle (Bard-Wang, Billerica, Mass., USA). METHODS: A case-control prospective study was conducted. The study group included 42 TBNA of mediastinal nodes performed in 35 patients with the eXcelon 21-gauge needle from January to June 2005. A control group included 110 TBNA carried out in 99 patients that underwent mediastinal lymph node sampling using a MW-122 needle from June 2002 to December 2004. RESULTS: There was no statistical differentiation in the characteristics of the disease, mediastinal lymph nodes or number of passes between cases and controls. Adequate samples were obtained in 30 (71.4%) cases and 81 (73.6%) controls (p = 0.8). Technical complications occurred in 7 (16.6%) cases and 14 (12.7%) controls (p = 0.7). The only clinical complication was bleeding presented in 2 (4.8%) cases and 3 (2.7%) controls (p = 0.3). CONCLUSION: The eXcelon 21-gauge transbronchial needle is as effective and safe as the MW-122 needle in the diagnosis of mediastinal lymph node enlargement.  相似文献   
148.
The presence and phenotype of apoptotic lymphocytes was studied in spleen cell suspensions taken from CB6F1 mice infected with Plasmodium chabaudi chabaudi AS. High levels of apoptotic cells were found, associated with high parasitaemias and splenomegaly. This was also accompanied by expansion and disarray of spleen white pulp. Apoptosis levels lowered when parasitaemia was cleared, but were still higher than in normal mice. At this time, the spleen was diminishing in size and the white pulp was contracting and rearranging. When parasitaemia was patent, the cells most affected by apoptosis were CD4+ T cells followed by CD8+ T cells, and to a lesser extent B220+ B cells. When parasitaemia was cleared, CD8+ T cells and B220+ B cells returned to basal levels of apoptosis, while CD4+ T cells still had higher apoptosis levels than normal mice. A similar pattern of lymphocyte subpopulation apoptosis was found in infected BALB/c mice, despite the fact that, for this mouse model, it has been reported that B cells are the cells that are most affected by apoptosis. We consider that the high levels of apoptosis in CD4+ T cells when parasitaemias are still high are not easily explained by a normal mechanism of down regulation of the immune response.  相似文献   
149.
150.
BACKGROUND & AIMS: Many patients with chronic hepatitis C virus (HCV) have persistently normal serum alanine transaminase (ALT) levels. We compared characteristics of chronic hepatitis C patients with patients with normal and elevated ALT levels using data from 3 randomized phase III trials of peginterferon alfa-2a (40 kDa). METHODS: The characteristics of 480 patients with normal ALT values (on >or=3 occasions without any increases in ALT level over a 6- to 18-month period) and 1993 patients with elevated ALT levels were compared. Sixty-eight of the 480 patients with normal ALT levels were randomized to no treatment and monitored for 72 weeks. RESULTS: More patients with normal ALT levels than patients with elevated ALT levels were women (59% vs 32%; P<.01). The serum HCV RNA titer was significantly lower in patients with normal ALT levels (P<.01 vs in patients with elevated ALT levels). Patients with normal ALT levels had significantly lower inflammation and fibrosis scores on liver biopsy examination than patients with elevated ALT levels, but almost two-thirds had portal fibrosis and 10% had bridging fibrosis. No correlation between baseline ALT activity, HCV RNA level, and liver histology was observed in patients with normal ALT levels. During the 72-week follow-up period, ALT activity elevated above the upper limit of normal in 53% of the untreated patients with normal levels of ALT. None became HCV RNA undetectable. CONCLUSIONS: Chronic hepatitis C patients with normal ALT levels should be evaluated in a similar manner as patients with elevated ALT levels because they are at risk for developing significant liver disease. The decision to treat with peginterferon alfa and ribavirin should be based on multiple factors, rather than on ALT levels alone.  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