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   606905篇
  免费   34911篇
  国内免费   3238篇
耳鼻咽喉   8159篇
儿科学   15294篇
妇产科学   14709篇
基础医学   85727篇
口腔科学   17021篇
临床医学   48232篇
内科学   128417篇
皮肤病学   14607篇
神经病学   47444篇
特种医学   20981篇
外国民族医学   182篇
外科学   88695篇
综合类   10936篇
现状与发展   1篇
一般理论   126篇
预防医学   38278篇
眼科学   13903篇
药学   47025篇
  1篇
中国医学   2875篇
肿瘤学   42441篇
  2021年   5970篇
  2020年   3644篇
  2019年   6506篇
  2018年   11747篇
  2017年   8194篇
  2016年   8274篇
  2015年   9354篇
  2014年   11253篇
  2013年   16365篇
  2012年   25710篇
  2011年   25848篇
  2010年   13967篇
  2009年   11654篇
  2008年   22903篇
  2007年   24729篇
  2006年   23466篇
  2005年   22391篇
  2004年   21089篇
  2003年   19736篇
  2002年   18784篇
  2001年   33967篇
  2000年   34604篇
  1999年   28842篇
  1998年   6070篇
  1997年   5020篇
  1996年   4585篇
  1995年   4142篇
  1994年   3703篇
  1993年   3370篇
  1992年   19040篇
  1991年   17542篇
  1990年   16734篇
  1989年   16338篇
  1988年   14844篇
  1987年   14154篇
  1986年   13112篇
  1985年   12129篇
  1984年   8213篇
  1983年   6738篇
  1982年   3371篇
  1979年   6634篇
  1978年   4174篇
  1977年   3733篇
  1975年   3426篇
  1974年   4013篇
  1973年   3839篇
  1972年   3735篇
  1971年   3658篇
  1970年   3340篇
  1969年   3422篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Background : Methimazole, an anti-thyroid drug, was recently found to be useful in the treatment of systemic lupus erythematosus and other autoimmune diseases. Moreover, decreased thyroid hormone production is associated with a variety of immunological manifestations, such as reduced activation of CD4+ cells, increased CD8+ cell activity and reduced soluble IL-2 receptors. In the present study we examined the effects of methimazole and propylthiouracil on a rat model of experimental colitis.
Methods : Colitis was induced by intracolonic administration of 30 mg trinitrobenzene sulphonic acid (TNB). Two weeks prior to induction of colitis, rats were treated by either methimaziole (0.04%) or propylthiouracil (0.01%) in drinking water after a week of free access to water. Rats were sacrificed 48 h or 7 days after induction of colitis. The colon was isolated, rinsed with ice-cold water and weighed. Damage was assessed both macroscopically and microscopically and myeloperoxidase (MPO) activity determined.
Results : All treated rats were hypothyroid as manifested by a significant elevation of thyroid stimulating hormone (TSH), by comparison with the control groups (mean -1.82±0.40 versus 0.11±0.02 mmol/L, respectively). The inflammatory response elicited by TNB resulted in severe mucosal damage 48 h after damage induction, which persisted for 7 days. Pre-treatment with either methimazole 0.04% or propylthiouracil 0.01% significantly decreased mucosal damage macroscopically (lesion area, lesion score and segmental weight) microscopically and also significantly decreased MPO level at both time points ( P <0.01).
Conclusions : Methimazole and propylthiouracil significantly reduce mucosal damage and colonic weight in a rat model of colitis. The mode by which they do so remains to be studied.  相似文献   
72.
The aim of this study was to investigate retrospectively the efficacy of expandable metallic stents (EMSs) for severe respiratory distress in patients with central airway obstruction. Twenty patients with central airway obstructions were treated with an EMS. An intraluminal stricture was present in 15 and an extraluminal stricture in 5 patients. Of the 15 patients with intraluminal stenosis, 11 exhibited symptomatic improvement. All 11 patients had tumor infiltration occupying less than 50% of the endoluminal diameter. The other four patients with intraluminal stenosis had tumor infiltration occupying > 50% of the endoluminal diameter and demonstrated no improvement. All five patients with extraluminal stenosis were improved. EMS is useful for an extraluminal stricture in the central airway and the effect of EMS for intraluminal stenosis is related to the degree of infiltration and of tumor progression itself.   相似文献   
73.
74.
Mutations P225L and P225R were identified in codon 225 of the gene for ornithine transcarbamylase (OTC) in two patients with the neonatal form of OTC deficiency. The mutations occur at a CpG dinucleotide and eliminate a unique MspI restriction site in exon 7 of the OTC gene. They do not alter existing splice sites or create new sites, as judged from the nucleotide sequence. Both mutations are associated with undetectable levels of OTC antigen in liver homogenates, and with either complete lack of OTC activity (P225R mutation) or very small residual activity (0.15% of normal in the P225L mutation). The residual activity observed with P225L exhibits normal pH dependence, little or no increases in the Km values for ornithine and carbamoyl phosphate and normal stability at either 37°C or, in the presence of 0.66 mol/L urea, at 0°C. The latter conditions were used to examine whether the P225L mutation favours dissociation of the active OTC trimer. Given the normal stability and lack of tendency to dissociation of the mutant enzyme, it appears likely that the dramatic reduction in the level of OTC protein is due to inefficient conversion of the mutant OTC precursor polypeptide (pOTC) into the correctly localized, appropriately folded, mature enzyme trimer, suggesting degradation of pOTC in transit to the mitochondria.  相似文献   
75.
Congenital intermaxillary fusion is a rare anomaly. Combination of the anomaly with any type of facial cleft is extremely rare. Death in a majority of these patients as a result of feeding and aspiration problems in early life may have caused the reports to be limited. In this article a 5-year-old patient, probably the first in the literature having Tessier type VI-VII facial cleft combination associated with bimaxillary fusion and anophthalmia on the right side, is presented. The patient has survived on fluid meal through a very small opening for 5 years. The features of the case are presented, and the time and method of the management of such a rare anomaly are discussed with a review of the literature.  相似文献   
76.
77.
78.
The results of the in vitro fertilisation programme at Tygerberg Hospital for the period April 1983 to January 1988 are presented. Of the 1117 laparoscopies performed, 825 patients reached the transfer stage. A live-birth rate of 9.3% was achieved. The pregnancy rate after transfer of 4 embryos was 25.9% compared with 15.4% after 2 embryos and 10.8% after 3 embryos (P = less than 0.0001). The multiple pregnancy rate was 2.8% in the group receiving 2 embryos and 11.7% and 10.4% in those receiving 3 and 4 embryos, respectively. Of the 77 successful pregnancies (90 babies), 1 baby died at 34 weeks' gestation as the result of abruptio placentae due to preeclampsia and 1 cot death occurred. The only congenital abnormality encountered was a cleft palate.  相似文献   
79.
80.
Physical therapy without anesthesia or plaster casts was used to treat 338 cases of clubfoot (CF). Our technique is based on progressive sequential manipulations at birth. We first reduce the varus and later the equinus component of the CF. The gentle stretches used in this technique are complemented by active physiotherapy stimulating the muscles, and then a simple splint is suited to the foot to fix its degree of realignment. When used alone, this technique achieves 77% good and fair results. In resistant cases, complementary surgery was used. We obtained 96% good and fair results.  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