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   2856篇
  免费   283篇
  国内免费   46篇
耳鼻咽喉   49篇
儿科学   140篇
妇产科学   72篇
基础医学   424篇
口腔科学   50篇
临床医学   380篇
内科学   580篇
皮肤病学   88篇
神经病学   132篇
特种医学   276篇
外科学   315篇
综合类   77篇
一般理论   3篇
预防医学   270篇
眼科学   32篇
药学   199篇
中国医学   2篇
肿瘤学   96篇
  2021年   29篇
  2020年   31篇
  2019年   51篇
  2018年   52篇
  2017年   45篇
  2016年   44篇
  2015年   48篇
  2014年   64篇
  2013年   107篇
  2012年   123篇
  2011年   105篇
  2010年   95篇
  2009年   76篇
  2008年   91篇
  2007年   116篇
  2006年   103篇
  2005年   118篇
  2004年   80篇
  2003年   73篇
  2002年   72篇
  2001年   67篇
  2000年   75篇
  1999年   83篇
  1998年   71篇
  1997年   66篇
  1996年   57篇
  1995年   48篇
  1994年   57篇
  1993年   54篇
  1992年   62篇
  1991年   51篇
  1990年   62篇
  1989年   69篇
  1988年   88篇
  1987年   68篇
  1986年   57篇
  1985年   79篇
  1984年   37篇
  1983年   34篇
  1982年   32篇
  1981年   34篇
  1980年   27篇
  1979年   48篇
  1978年   27篇
  1977年   22篇
  1976年   34篇
  1975年   26篇
  1974年   28篇
  1973年   31篇
  1970年   20篇
排序方式: 共有3185条查询结果,搜索用时 16 毫秒
11.
Personalized feedback and a financial incentive, developed from an intrinsic/extrinsic motivation framework, were evaluated as adjuncts to self-help materials for smoking cessation. Ss (N = 1,217) were randomized to 4 treatment groups and were followed up at 3 and 12 months. Consistent with hypotheses derived from the motivation framework, the financial incentive increased the use of self-help materials, did not increase cessation rates among program users, and was associated with higher relapse rates among those who did manage to quit. The personalized feedback increased both smoking cessation and use of the materials 3 months after distribution of the materials. Continuous abstinence (abstinence at 3 and 12 months) in the group that received the personalized feedback alone was twice the rate of the other groups.  相似文献   
12.
13.
AIM OF THE STUDY: The umbilical polyp is a rare congenital lesion resulting from the persistence of omphalomesenteric duct (OMD) enteric mucosa at the umbilicus. Exploration of the abdomen to exclude the presence of associated OMD remnants is controversial. The aim of this study was to evaluate the need for peritoneal cavity exploration in children with umbilical polyp. METHODS: All umbilical lesions (n = 53) excised between 1995 and 2005 in a single institution were reviewed to identify patients with umbilical polyp (n = 13). This is characterised histologically by the presence of gastrointestinal mucosa. A follow-up study of patients with umbilical polyp was performed. Data are reported as median (range). RESULTS AND CONCLUSIONS: All 13 patients underwent excision of an umbilical polyp at a median age of 15.1 months (3.1 - 80.5). All presented with a discharging polyp (associated with bleeding in 9) which did not respond to topical silver nitrate. Median diameter of the lesions was 0.5 cm (0.2 - 1). Histology revealed the presence of small bowel mucosa in 11 (associated with pancreatic tissue in 1 and gastric mucosa in 1) and large bowel mucosa in 2. All patients underwent inspection and probing of the base of the polyp after its excision. In 6 patients an associated OMD anomaly was suspected and exploration of the peritoneal cavity was performed (mini-laparotomy in 5 and laparoscopy in 1). No OMD anomaly was found. The 7 children who did not undergo exploration of the abdominal cavity remain asymptomatic after 5.8 years (0.9 - 13.7) follow-up. An umbilical polyp can be present in the absence of other OMD anomalies. Exploration of the peritoneal cavity in children with an umbilical polyp does not seem to be necessary.  相似文献   
14.
Carcinoma of the hepaticopancreatic ampullar region: role of US   总被引:3,自引:0,他引:3  
Hepaticopancreatic ampullar tumors are so called because they are located at the confluence of the bile duct, pancreatic duct, and duodenum. Jaundice is an early sign of the disease and often leads to early diagnosis and favorable prognosis compared with other tumors that occur in this area. Of eight patients who underwent ultrasound (US) in the past 5 years, six (75%) were found to have tumor. The sizes of the tumors ranged from 1.6 to 2 cm. An intraluminal, polypoid mass in the distal part of the common bile duct was seen in four patients. In the other two patients, a sharply delineated mass gave rise to abrupt termination of the distal duct. Improved US resolution, more experience with this modality, and accurate diagnosis of these tumors with US will contribute to improved detection and prompt treatment.  相似文献   
15.
16.
17.
18.
19.
Dolichospondylic dysplasia (DD) is a rare skeletal dysplasia primarily characterized by tall vertebral bodies and disproportionate short stature. Radiographic manifestations include tall vertebral bodies and gracile bones of the hands. Patients usually have eye and ear findings in addition to borderline mental retardation; however, tall vertebral bodies and slender tubular bones are also seen in the 3-M syndrome. Patients with the 3-M syndrome have a characteristic face with a triangular shape, frontal bossing, a flattened malar region, full eyebrows, a short nose with a bulbous tip, upturned nares, and full lips. We present two unrelated patients who share a distinct phenotype and have tall vertebral bodies, overtubulation of long bones, and short tubular bones of the hands and feet. We discuss the overlapping and distinguishing features between DD and the 3-M syndrome. Patient 1 was a 13-year-old female, and patient 2 was an unrelated adult female. These patients had normocephaly and short stature. They shared a common phenotype consisting of mild malar hypoplasia, a narrowed nasal body with a fleshy tip, full lips, and normal intelligence. In addition, they showed mild hand and foot abnormalities. These two patients lack many of the typical clinical features of both DD and the 3-M syndrome. They share a common phenotype and likely represent a distinct disorder. The spectrum of disorders with tall vertebral bodies as a key feature may include different entities that may be further defined with the characterization of the molecular defect(s).  相似文献   
20.
Human mini-chromosomes in mouse embryonal stem cells   总被引:3,自引:2,他引:3  
We have introduced human mini-chromosomes of 4 Mb and approximately 15 Mb in size into mouse embryonal stem cells. Although these human mini- chromosomes are stable in hamster and chicken cells, they re-arrange or segregate aberrantly in the embryonal stem cells and are rapidly lost in the absence of selection. However, one of the mini-chromosomes re- arranged, acquired mouse centromeric sequences and was then stably maintained for at least 60 population doublings in culture. This mini- chromosome, which is 4 Mb in size, is a candidate for a mouse germ line chromosome vector.   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