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   3620271篇
  免费   256435篇
  国内免费   9481篇
耳鼻咽喉   48870篇
儿科学   120061篇
妇产科学   99481篇
基础医学   508672篇
口腔科学   102193篇
临床医学   331741篇
内科学   705737篇
皮肤病学   85369篇
神经病学   293030篇
特种医学   137338篇
外国民族医学   941篇
外科学   540542篇
综合类   77870篇
现状与发展   8篇
一般理论   1397篇
预防医学   277337篇
眼科学   83897篇
药学   264256篇
  12篇
中国医学   7991篇
肿瘤学   199444篇
  2019年   28717篇
  2018年   40897篇
  2017年   31168篇
  2016年   35472篇
  2015年   40179篇
  2014年   55630篇
  2013年   83125篇
  2012年   112060篇
  2011年   118638篇
  2010年   71025篇
  2009年   67414篇
  2008年   110455篇
  2007年   117576篇
  2006年   119199篇
  2005年   114349篇
  2004年   110029篇
  2003年   105814篇
  2002年   102209篇
  2001年   175845篇
  2000年   179969篇
  1999年   151360篇
  1998年   43040篇
  1997年   37901篇
  1996年   38032篇
  1995年   36869篇
  1994年   33701篇
  1993年   31585篇
  1992年   117149篇
  1991年   112977篇
  1990年   109365篇
  1989年   105667篇
  1988年   96619篇
  1987年   94636篇
  1986年   88852篇
  1985年   84835篇
  1984年   63240篇
  1983年   53665篇
  1982年   31482篇
  1981年   28067篇
  1979年   55951篇
  1978年   39282篇
  1977年   33429篇
  1976年   31167篇
  1975年   32972篇
  1974年   39346篇
  1973年   37621篇
  1972年   35135篇
  1971年   32595篇
  1970年   30126篇
  1969年   28789篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
AIM: The present meta-analysis aims to compare short-term and long-term outcomes in patients undergoing laparoscopic or open subtotal colectomy for benign and malignant disease. METHODS: A literature search of Medline, Ovid, Embase and Cochrane databases was performed to identify studies published between 1992 and 2005, comparing laparoscopic (LSC) and open (OSC) subtotal colectomy. A random effect meta-analytical technique was used and sensitivity analysis performed on studies published since the beginning of 2000, higher quality papers, those reporting on more than 40 patients, and those studies reporting on adult cases or acute colitis. RESULTS: A total of eight studies satisfied the criteria for inclusion. These included outcomes on 336 patients, 143 (42.6%) of whom had undergone laparoscopic resection, with an overall conversion rate to open surgery of 5% (range 0-11.8%). Operative time was significantly longer in the laparoscopic group by 86.2 min (P < 0.001) and throughout subgroup analysis, although it was only in patients with acute colitis that this finding was without significant heterogeneity. Operative blood loss was less in the laparoscopic group by 57.5 millilitres in high quality and studies published since 2000, and 65.3 millilitres in those reporting on more than 40 patients. There was no significant difference in early or long-term complications between the groups. A statistically significant reduction in length of postoperative stay was observed in the laparoscopic groups by 2.9 days (P < 0.001). CONCLUSION: Laparoscopic subtotal colectomy was associated with longer operating times but a reduced length of stay compared to open surgery. Although short-term outcomes were equivalent in both groups, the suggested benefits in terms of reduced long-term obstructive complications were not supported by this meta-analysis.  相似文献   
992.
BACKGROUND: Studies of the association between indoor allergen exposure and the development of allergic diseases have often measured allergen exposure at one point in time. OBJECTIVE: We investigated the variability of house dust mite (Der p 1, Der f 1) and cat (Fel d 1) allergen in Dutch homes over a period of 8 years. METHODS: Data were obtained in the Dutch PIAMA birth cohort study. Dust from the child's mattress, the parents' mattress and the living room floor was collected at four points in time, when the child was 3 months, 4, 6 and 8 years old. Dust samples were analysed for Der p 1, Der f 1 and Fel d 1 by sandwich enzyme immuno assay. RESULTS: Mite allergen concentrations for the child's mattress, the parents' mattress and the living room floor were moderately correlated between time-points. Agreement was better for cat allergen. For Der p 1 and Der f 1 on the child's mattress, the within-home variance was close to or smaller than the between-home variance in most cases. For Fel d 1, the within-home variance was almost always smaller than the between-home variance. Results were similar for allergen levels expressed per gram of dust and allergen levels expressed per square metre of the sampled surface. Variance ratios were smaller when samples were taken at shorter time intervals than at longer time intervals. CONCLUSION: Over a period of 4 years, mite and cat allergens measured in house dust are sufficiently stable to use single measurements with confidence in epidemiological studies. The within-home variance was larger when samples were taken 8 years apart so that over such long periods, repetition of sampling is recommended.  相似文献   
993.
BACKGROUND: Stress can aggravate the allergic inflammation, but determinants of disturbed immune regulation are largely unknown. OBJECTIVE: To determine systemic immunological, local inflammatory and functional airway responses to stress in healthy and atopic individuals. METHODS: Forty-one undergraduate students, 22 with allergy of whom 16 had asthma, and 19 healthy controls, were studied in a low-stress period and in association with a large exam. Subjects completed questionnaires on stress and health behaviours, underwent lung function tests, bronchial methacholine challenge, measurements of exhaled nitric oxide and urine cortisol. Blood cells were phenotyped, and cytokines from mononuclear blood cells were analysed. RESULTS: Perceived stress and anxiety increased in both groups during the exam period while cortisol increased only in the atopy group. Cytokine production decreased broadly in response to stress in both groups, which was paralleled by an increase in the proportion of regulatory T cells (CD4(+)CD45RO(+)CD25(bright)). Interestingly, atopic individuals, but not controls, reacted with a decreased T-helper type 1/T-helper type 2 (Th1/Th2) ratio and a decrease in natural killer (NK) cell numbers in response to stress. In control subjects only, exhaled nitric oxide decreased and forced expiratory volume in one second increased during stress. CONCLUSION: Atopic and non-atopic subjects shared some immune changes in response to stress, such as a dramatic decline in cytokines and an increase in the number of regulatory T cells in peripheral blood. However, other stress-induced immune changes were unique to atopic individuals, such as a skewed Th1/Th2 ratio and reduced NK cell numbers, indicating that some pathogenic mechanisms in atopics may be more strongly affected by stress than others.  相似文献   
994.
995.
The term synovial sarcoma was first proposed for the histologically well defined entity by Knox in 1936. The name was proposed due to the fact that at least the cases reported in the early part showed some resemblance of the tumour to normal synovial tissue histologically. Thereafter, tumours have been diagnosed from areas without synovial tissue. The diagnosis of monophasic tumours can be difficult and immunostains appear to be a good diagnostic tool in those cases. The occurrence in the mandible is extremely rare. This is a case of synovial sarcoma arising in the condyle involving most of the ramus. The tumour was diagnosed as synovial sarcoma with predominant spindle cell component by correlation of histopathology with immunostains (cytokeratin, epithelial membrane antigen, actin and desmin). The patient has been treated with surgery and radiotherapy.  相似文献   
996.
997.
998.
999.
1000.
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