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   635篇
  免费   31篇
  国内免费   13篇
耳鼻咽喉   2篇
儿科学   32篇
妇产科学   8篇
基础医学   123篇
口腔科学   10篇
临床医学   43篇
内科学   78篇
皮肤病学   24篇
神经病学   13篇
特种医学   148篇
外科学   79篇
综合类   20篇
预防医学   27篇
眼科学   6篇
药学   35篇
肿瘤学   31篇
  2022年   4篇
  2021年   7篇
  2019年   3篇
  2018年   6篇
  2016年   8篇
  2015年   19篇
  2014年   9篇
  2013年   12篇
  2012年   7篇
  2011年   18篇
  2010年   27篇
  2009年   31篇
  2008年   19篇
  2007年   25篇
  2006年   22篇
  2005年   22篇
  2004年   22篇
  2003年   14篇
  2002年   13篇
  2001年   24篇
  2000年   11篇
  1999年   5篇
  1998年   20篇
  1997年   37篇
  1996年   23篇
  1995年   22篇
  1994年   17篇
  1993年   7篇
  1992年   10篇
  1991年   4篇
  1990年   13篇
  1989年   18篇
  1988年   13篇
  1987年   19篇
  1986年   14篇
  1985年   20篇
  1984年   9篇
  1983年   14篇
  1982年   8篇
  1981年   9篇
  1980年   12篇
  1979年   3篇
  1978年   6篇
  1977年   7篇
  1976年   8篇
  1975年   8篇
  1974年   6篇
  1973年   3篇
  1971年   5篇
  1965年   2篇
排序方式: 共有679条查询结果,搜索用时 9 毫秒
31.
In conditions of exotoxicosis arising after the effect of 2,4-dichlorphenoxyacetic acid cytoplasmic cells of littoral cells of marginal and medullary sinuses undergo alike changes and their cell organelles (rough endoplasmic reticulum, Golgi complex, micropinocytotic vesicles and mitochondria) mass is reduced. These changes are more pronounced in littoral cells of marginal sinus when the dos under the effect of 4 permissible doses of the poison. Intensity of intracellular structures reaction to the toxicant action depends on the cell localization on the lymph passage insid within the lymph node (marginal or medullar sinuses). Dystrophic changes in sinus lining cells so as the speed and character of regenerative processes depend on the dose and time of action of the agent.  相似文献   
32.
A history of pet contact and/or apparent clinical sensitivity was obtained in 65 (55%) of 118 unselected asthmatic children. These 65 children were skin tested and their sera examined for specific IgE using the radioallergosorbent test. Those children who had apparent clinical sensitivities had larger skin test reactions and were more likely to have positive specific IgE results than those without apparent sensitivities. Positive skin tests were very common (80%), but the larger the skin test reaction (weal diameter greater than 4 mm diameter) the more likely was there to be a positive history or a positive specific IgE result. Hence a large skin test reaction can provide a helpful pointer to animal allergy of clinical importance. Commercially available animal extracts have limitations for diagnostic tests. A questionnaire survey of 150 day schools emphasized the potential opportunities for contact with animal allergens at school.  相似文献   
33.
34.
The present study was undertaken to assess the temporal association between the profiles of serum concentrations of oestradiol-17beta, progesterone, chorionic gonadotrophin (CG) and relaxin in pregnancies established naturally, and after embryo transfer, as well as in failed pregnancies in rhesus monkeys. In naturally mated cycles (group 1) a conception rate of 75% was obtained. In group 1, the mean day of CG detection in serum was 11.5 +/- 1.9 day post-ovulation, and for relaxin, 9.0 +/- 2.5 day post-ovulation. In group 2, embryo transfer to synchronous, non-mated surrogate recipients was performed; seven embryo transfer cycles yielded three pregnancies which were allowed to continue to term and normal infants were delivered. In embryo transfer cycles the mean day of CG detection was 14.8 +/- 1.8 day post- ovulation, and for relaxin, 11.4 +/- 2.6 day post-ovulation. A delay of about 3 days was observed in the appearance in circulation of CG (P < 0.05) and also of relaxin (P < 0.05) between natural mated and embryo transfer conception cycles. Significant differences (P < 0.05 for progesterone and P < 0.03 for oestradiol) were obtained for the areas under the curves for progesterone and oestradiol between days 12 and 16 in conception cycles compared with failed pregnancies. These data provide the first observation of the normal hormonal signals associated with maternal recognition of transferred embryos during the peri- implantation period, and suggest that the use of such an experimental primate embryo transfer model may help to elucidate components of maternal and embryonic signal-response mechanisms during embryo implantation.   相似文献   
35.
36.
Background  Bacterial overgrowth may cause cobalamin deficiency through competition for dietary cobalamin in the small intestine. The objective of this study was to prospectively determine the prevalence of small bowel bacterial overgrowth in patients with documented cobalamin deficiency in a tertiary referral centre.
Methods  Patients identified with cobalamin deficiency underwent diagnostic investigations including: Endoscopy (with gastric antrum, gastric body and duodenal biopsies and duodenal aspirate), 14C-D-Xylose breath test, intrinsic factor antibody, anti-endomysial antibody and red cell folate level. 'Definite' small bowel bacterial overgrowth was defined as either a positive 14C-D-Xylose breath test or > 100 000 CFU/mL of culture of duodenal aspirate. 'Suspected' small bowel bacterial overgrowth was defined as an elevated red cell folate in the absence of supplemental folate therapy.
Results  Over a 2-year period, 62 patients with cobalamin deficiency were identified, of whom, 26 (42%) had 'definite' small bowel bacterial overgrowth, whilst a further nine (15%) had 'suspected' small bowel bacterial overgrowth. Nineteen (31%) had pernicious anaemia, and no cause for cobalamin deficiency could be found in eight (13%) patients. The diagnosis found in the remaining patients included coeliac disease (4), Crohn's Disease (1), gastric resection (2), vegan (2), homozygotes of the MTHFR gene (C677T) mutation (2), and one had enteropathy associated with common variable immunodeficiency (CVID). 'Definite' small bowel bacterial overgrowth was found to coexist with nine of the 19 cases of pernicious anaemia, two coeliac subjects, one CVID enteropathy and one patient with the MTHFR gene mutation.
Conclusion  Small bowel bacterial overgrowth is commonly associated with cobalamin deficiency.  相似文献   
37.
A rapid microagglutination test has been developed which can be performed in 30 minutes. Ninety-seven percent of 96 patients diagnosed as having Legionella pneumophila (serogroup 1) infection by indirect immunofluorescence were also detected by the rapid microagglutination test.  相似文献   
38.
39.
In a case-control study to understand the risk factors for development of life-threatening dehydration, a total of 379 children comprising 243 cases (moderate or severe dehydration) and 136 controls (non or mild dehydration) up to 2 years of age suffering from acute watery diarrhoea were studied. By univariate analysis, the presence of vibrios in stool, withdrawal of breast feeding during diarrhoea, not giving fluids, including oral rehydration solution (ORS), during diarrhoea, frequent purging (> 8/ day), vomiting (> 2/day) and undernutrition were identified as risk factors. However, by multivariate analysis after controlling for confounders, withdrawal of breast feeding during diarrhoea (odds ratio (OR) = 6.8, p < 0.00001) and not giving ORS during diarrhoea (OR = 2.1, p < 0.006) were identified as significant risk factors. The confounding variables which also contributed significantly to increasing the risk were age (≤ 12 months; OR = 2.7, p = 0.001), frequent purging (> 8/day; OR = 4.1, p < 0.00001), vomiting (> 2/day; OR = 2.4, p = 0.001) and severe undernutrition (%median <60 weight-for-age of Indian Academy of Paediatrics classification; OR = 3.1, p = 0.001). We feel that these findings will be useful for Global and National Diarrhoeal Diseases Control Programmes for formulating intervention strategies for preventing death due to diarrhoeal dehydration.  相似文献   
40.
Wild Norway rats were selected over 20 generations for reduced aggressiveness towards man. Selection for this characteristic was accompanied by many physiological changes. Although neophobia was significantly inhibited, and irritable aggression reduced by selection, no changes were revealed in mouse-killing behavior or in intermale aggression. The mean level of 5-hydroxyindole acetic acid in the hypothalamus as well as serotonin (5-HT) content in the hypothalamus, the midbrain and the cortices was higher in the 'domesticated' than in aggressive rats. Mean hypothalamic norepinephrine (NE) level also tended to be higher in the 'domesticated' animals. The resting corticosterone level and the response of the hypothalamic-pituitary-adrenocortical axis to an emotional stressor or intracerebroventricularly administered 5-HT or NE were decreased in domesticated rats compared to their aggressive counterparts. It is suggested that the diminution of the hypothalamic-pituitary-adrenocortical function as a result of selection for domesticated types of behavior depends, at least partly, on changes in brain monoaminergic systems.  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