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   21491篇
  免费   1609篇
  国内免费   56篇
耳鼻咽喉   277篇
儿科学   722篇
妇产科学   469篇
基础医学   3094篇
口腔科学   319篇
临床医学   2061篇
内科学   4073篇
皮肤病学   338篇
神经病学   2112篇
特种医学   711篇
外科学   2987篇
综合类   652篇
现状与发展   1篇
一般理论   30篇
预防医学   1679篇
眼科学   582篇
药学   1427篇
中国医学   55篇
肿瘤学   1567篇
  2023年   113篇
  2022年   271篇
  2021年   459篇
  2020年   264篇
  2019年   428篇
  2018年   510篇
  2017年   318篇
  2016年   413篇
  2015年   466篇
  2014年   604篇
  2013年   928篇
  2012年   1305篇
  2011年   1240篇
  2010年   756篇
  2009年   703篇
  2008年   1154篇
  2007年   1157篇
  2006年   1065篇
  2005年   1138篇
  2004年   1145篇
  2003年   1054篇
  2002年   945篇
  2001年   413篇
  2000年   392篇
  1999年   388篇
  1998年   235篇
  1997年   183篇
  1996年   180篇
  1995年   180篇
  1994年   142篇
  1993年   162篇
  1992年   272篇
  1991年   235篇
  1990年   248篇
  1989年   246篇
  1988年   226篇
  1987年   204篇
  1986年   219篇
  1985年   245篇
  1984年   182篇
  1983年   147篇
  1982年   155篇
  1981年   158篇
  1980年   136篇
  1979年   124篇
  1977年   102篇
  1976年   121篇
  1975年   106篇
  1974年   135篇
  1973年   103篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
63.
Crohn''s disease is well known for its multiple intestinal complications. The chronic nature and fibrous inflammation which invariably accompanies this disease explains the relative rarity of free intestinal perforation. The true incidence of free bowel perforation is difficult to assess but 1-2% is the anticipated occurrence during the course of illness. We present a case of Crohn''s disease which presented for the first time with acute colonic perforation, an extremely rare entity, and review the current world literature.  相似文献   
64.
A 69-year-old male with blepharospasm unresponsive to several medications who was successfully treated with quetiapine is described. His symptoms were largely alleviated by low doses, but he experienced sedation, which permitted him to take the medication at bedtime only.  相似文献   
65.
66.
Twenty-nine infants (2-4 months old), with pathological gastroesophageal reflux assessed by 24-h esophageal pH monitoring, were studied. Cisapride or placebo was randomly added to positional treatment, prone-antiTrendelenburg position, which was applied to all infants. The pH monitoring was repeated after 13-16 days of treatment and revealed a significant improvement in both groups for most parameters. But the number of reflux episodes lasting longer than 5 min and the total number of reflux episodes had not decreased significantly in the placebo group. Only in the number of reflux episodes lasting longer than 5 min was improvement during treatment significantly greater in the cisapride group. This suggests cisapride both prevented reflux and improved esophageal clearance. These results suggest that in addition to other therapeutic measurements, such as positional treatment (which was previously demonstrated to be effective in this age group), cisapride might be of benefit in the treatment of gastroesophageal reflux disease.  相似文献   
67.
BACKGROUND: Executive dysfunctions have been studied as a potential endophenotype associated with the genetic basis of autism. Given that recent findings from clinical and molecular genetic studies suggest that autism and obsessive-compulsive disorder (OCD) could share a common pattern of heritability, we assessed executive functions as a possible common cognitive endophenotype in unaffected family members of individuals with either autism or OCD. METHODS: Five tests assessing executive functions (Tower of London, verbal fluency, design fluency, trail making and association fluency) were proposed to 58 unaffected first-degree relatives (parents and siblings) of probands with autism and 64 unaffected first-degree relatives of OCD patients. Results were compared with those of 47 healthy controls matched for age, sex, and level of education. RESULTS: In the Tower of London test, both groups of unaffected relatives showed significantly lower scores and longer response times compared with controls. No differences were observed between autism and OCD relatives and healthy controls in the four other tasks (verbal fluency, design fluency, trail making test and association fluency). CONCLUSIONS: Our findings show the existence of executive dysfunction in the unaffected first-degree relatives of probands with OCD, similar to those observed in the relatives of patients with autism. These results support and extend previous cognitive studies on probands indicating executive dysfunctions in autism and OCD. Planning and working memory processes could thus represent a common cognitive endophenotype in autism and OCD that could help in the identification of genes conferring vulnerability to these disorders.  相似文献   
68.
N-(4-Cyanophenyl)-N'-(2-carboxyethyl)urea (2), an analogue of suosan [1,N-(4-nitrophenyl)-N'-(2-carboxyethyl)urea], is a known high-potency sweetener derived from beta-alanine. Sulfonic and phosphonic acid analogues of 2 were prepared to develop structure-activity relationships through modification of the carboxylic acid region of this family of sweeteners. Neither of the carboxylic acid replacements resulted in sweet analogues. However, we found that N-(4-cyanophenyl)-N'-[(sodiosulfo)methyl]urea (7) is an antagonist of the sweet taste response. The bitter taste response to caffeine, quinine, and naringin was also antagonized. Antagonist 7 was found to inhibit the sweet taste perception of a variety of sweeteners. Antagonist 7 had no effect on the sour or salty taste response.  相似文献   
69.
OBJECTIVE: To determine the impact of nutritional status on peritonitis in patients on continuous ambulatory peritoneal dialysis (CAPD) in a developing country. METHODS: 56 patients with end-stage renal disease on CAPD were randomly selected for this study. These patients were assessed for nutritional status and peritonitis episodes. Nutritional parameters were assessed by anthropometry, diet, body mass index (BMI), Nutritional Risk Index (NRI), serum albumin level, and Subjective Global Assessment (SGA). Based on SGA, patients were categorized into either group 1 (malnutrition, n = 31) or group 2 (normal nutritional status, n = 25). Peritonitis was considered the primary outcome and was compared between the two groups. RESULTS: Demographic profiles, Kt/V, creatinine clearance, and mean follow-up of the two groups were similar. Number of peritonitis episodes was significantly higher in patients with malnutrition (25/31) compared to patients with normal nutritional status (4/25) (p = 0.001). Mean peritonitis rate per patient per year was also significantly higher in patients with malnutrition (0.99 +/- 1.07) compared to patients with normal nutritional status (0.18 +/- 0.42) (p = 0.007). On univariate analysis, malnutrition based on SGA (p = 0.009), NRI (p = 0.02), serum albumin level (p = 0.005), and calorie intake (p = 0.006) was a significant predictor of peritonitis. On multivariate Cox regression analysis, only SGA (p = 0.001, odds ratio 0.08, 95% confidence interval 0.02-0.36) was found to be a significant predictor of peritonitis. On general linear model, the observed power of prediction of peritonitis was 0.96 based on SGA. On Kaplan-Meier survival analysis, peritonitis-free survival in patients with normal nutrition (42 months) was significantly higher compared to patients with malnutrition (21 months) based on SGA (log rank p = 0.003). CONCLUSION: We conclude that peritonitis rate is high in patients with malnutrition and that malnutrition indices, especially SGA, can predict the peritonitis rate in CAPD patients.  相似文献   
70.
The α-inhibin gene has been shown in knockout mouse models to be a suppressor of granulosa tumorigenesis in the mouse. To determine if α-inhibin has the same function in humans, we have assessed the frequency of loss of heterozygosity (LOH) of the α-inhibin gene locus on chromosome 2q in 17 human granulosa cell tumors and 36 epithelial ovarian cancers. LOH was detected in 12 of 36 (33.3%) epithelial tumors but in only 1 of 17 (6%) granulosa cell tumors. These data suggest that in contrast to the suggestions from the mouse model α-inhibin does not function as a granulosa cell tumor suppressor gene in the human. Furthermore, analysis of the TP53 gene in the granulosa cell tumors failed to detect either LOH or point mutations, indicating that they have a developmental pathway distinct from that of epithelial ovarian tumors.  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