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   3249085篇
  免费   258605篇
  国内免费   7735篇
耳鼻咽喉   46073篇
儿科学   102715篇
妇产科学   89376篇
基础医学   454412篇
口腔科学   92737篇
临床医学   297727篇
内科学   633855篇
皮肤病学   69199篇
神经病学   272604篇
特种医学   127607篇
外国民族医学   1192篇
外科学   486741篇
综合类   81450篇
现状与发展   7篇
一般理论   1334篇
预防医学   263772篇
眼科学   76832篇
药学   238187篇
  23篇
中国医学   7514篇
肿瘤学   172068篇
  2018年   35231篇
  2017年   27143篇
  2016年   30019篇
  2015年   34138篇
  2014年   48932篇
  2013年   73510篇
  2012年   99208篇
  2011年   104871篇
  2010年   62061篇
  2009年   59201篇
  2008年   98215篇
  2007年   104142篇
  2006年   105188篇
  2005年   102269篇
  2004年   97949篇
  2003年   94215篇
  2002年   92156篇
  2001年   151215篇
  2000年   155829篇
  1999年   131235篇
  1998年   38561篇
  1997年   34970篇
  1996年   34569篇
  1995年   33126篇
  1994年   30838篇
  1993年   28867篇
  1992年   103624篇
  1991年   99608篇
  1990年   95917篇
  1989年   92214篇
  1988年   85531篇
  1987年   84121篇
  1986年   79294篇
  1985年   75765篇
  1984年   57831篇
  1983年   49277篇
  1982年   30195篇
  1981年   26863篇
  1979年   53522篇
  1978年   37769篇
  1977年   31666篇
  1976年   29772篇
  1975年   31014篇
  1974年   38144篇
  1973年   36460篇
  1972年   34202篇
  1971年   31461篇
  1970年   29746篇
  1969年   27681篇
  1968年   25626篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
No excess of DR*3/4 in Ashkenazi Jewish or Hispanic IDDM patients   总被引:1,自引:0,他引:1  
The gene frequencies, haplotype relative risks, and zygotic assortments of HLA-DR in three ethnically defined samples of insulin-dependent diabetes mellitus (IDDM) patients were determined in a prospective family study. Although DR3 and DR4 were positively associated with IDDM in the probands of 123 northern European, 94 Ashkenazi Jewish, and 49 New York Hispanic families, significant excess of DR*3/4 heterozygotes was observed only among the probands from families of northern European ancestry. There was also a significant decrease in the frequency of Bw62,DR4 haplotypes derived by northern European patients from their mothers compared with their fathers. This difference, together with data reported in the literature, suggests that the expressivity of the susceptible genotype(s) in IDDM patients may be modified by protective maternal effects associated with Bw62,DR4 and probably other DR4 haplotypes. Samples of IDDM patients from populations with high frequencies of these modifiers should have different DR-gene frequencies contributed by fathers and mothers, capable of accounting for the observed Hardy-Weinberg disequilibrium. We postulate that, because the mechanism of action of these modifiers is distinct from that of the susceptibility gene, the difference must be considered in devising strategies for elucidation of the mode of inheritance of the disease and for understanding the molecular nature of the susceptibility.  相似文献   
992.
Summary Intracavitary application of ultrasound was first performed for diagnostic purposes in 1967; since that time, it has been more and more widely used. As far as the gastrointestinal tract is concerned, endoscopically controlled ultrasonic probes provide visualization of the various layers of the intestinal wall. It is therefore possible to describe lesions of the esophagus, stomach, and the rectum with regard to their nature and depth of infiltration. Furthermore, periesophageal and perigastric organs can be visualized. It has become evident that endosonography is particularly important for pretherapeutic staging of tumors of the esophagus, stomach, and rectum. Here prospective comparative studies confirm the superiority of this new diagnostic procedure when compared to the methods available to date.  相似文献   
993.
994.
Management of splenic injuries in children has evolved over the past two decades. Splenectomies or splenorrhaphies are now performed infrequently, with the majority of hemodynamically stable children with splenic injuries managed nonoperatively. This article reviews the imaging features of acute splenic injuries in children as well as the appearance of healing splenic injuries. Follow-up evaluation and outcomes in children with splenic injuries also are addressed.  相似文献   
995.
We prospectively enrolled 160 consecutive patients with inversion trauma of the ankle in a diagnostic protocol that included physical examination within 2 days and at 5 days after trauma, arthrography, stress radiography, and ultrasonography. 135 patients had pathological lateral ligament laxity on the later physical examination or lateral ligament rupture diagnosed on arthrography and they were operated on. 122 of these patients had ligament ruptures.

At clinical follow-up after a minimum of half a year, all of the patients who were not operated on had stable joints without signs of previous ligament ruptures.

Delayed physical examination at 5 days after the injury led to the highest overall sensitivity (96%) and specificity (84%) for the detection of a ligament rupture. Additional diagnostic procedures, at a considerable cost, yielded little additional information.  相似文献   
996.
997.
BACKGROUND: Catheter hub contamination is being increasingly recognized as a source of catheter-related sepsis. The authors have investigated the efficacy of a new hub design in preventing endoluminal catheter contamination and catheter-related sepsis arising at the hub. METHODS: Adult surgical and intensive care patients requiring a subclavian catheter for at least 1 week were randomly assigned to receive catheters with standard connectors (control group, n=73) or equipped with a new hub model (new hub group, n=78). Skin, catheter tip, and hub cultures were performed at the time the catheter was withdrawn because therapy was terminated or because of suspicion of sepsis, in which case peripheral blood cultures were taken. RESULTS: Of the 151 patients included, 15 (10%) developed catheter-related sepsis. Catheters were more often withdrawn because suspicion of infection in the control group (42 vs. 19%, p<0.005). Catheter sepsis rate was higher in the control group (16 vs. 4%, p<0.01) because of the low rate of catheter sepsis arising at the hub observed in the new hub group (1 vs. 11%, p<0.01). The prevalence of culture-positive catheter hubs without associated bacteremia (colonization) was higher in the control group (18 vs. 5%, P<0.03). CONCLUSIONS: A new catheter hub has proved to be useful in preventing endoluminal bacterial colonization and catheter-related sepsis in subclavian lines inserted for a mean of 2 weeks.  相似文献   
998.
999.
A hemoglobin-binding protein (HgbA) from Haemophilus ducreyi was identified and purified. The 100-kDa HgbA was detected in all strains of H. ducreyi tested, and a somewhat larger hemoglobin-binding protein was found in one strain of Haemophilus influenzae. HgbA was purified and the amino acid sequence of the N terminus of HgbA revealed no significant homologies with known proteins. Two different antisera to HgbA from H. ducreyi 35000 recognized HgbA proteins from all tested H. ducreyi strains; they did not recognize proteins from the H. influenzae strain. Expression of HgbA was regulated by the level of heme but not by iron present in the medium. Animal species of hemoglobin competed with iodinated human hemoglobin for binding to whole cells of H. ducreyi and supported the growth of H. ducreyi. The lack of immunological cross-reactivity and the differences in hemoglobin specificities between the H. ducreyi and the H. influenzae hemoglobin-binding proteins suggest that they are unrelated.  相似文献   
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