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   515046篇
  免费   33404篇
  国内免费   615篇
耳鼻咽喉   6905篇
儿科学   16852篇
妇产科学   13529篇
基础医学   85151篇
口腔科学   14504篇
临床医学   44394篇
内科学   93821篇
皮肤病学   12191篇
神经病学   36333篇
特种医学   18490篇
外国民族医学   63篇
外科学   77250篇
综合类   8481篇
一般理论   118篇
预防医学   39003篇
眼科学   12161篇
药学   40599篇
中国医学   1008篇
肿瘤学   28212篇
  2018年   4947篇
  2015年   4524篇
  2014年   6085篇
  2013年   9572篇
  2012年   12908篇
  2011年   14318篇
  2010年   8330篇
  2009年   7801篇
  2008年   13732篇
  2007年   14732篇
  2006年   14984篇
  2005年   14402篇
  2004年   14083篇
  2003年   13431篇
  2002年   13315篇
  2001年   24110篇
  2000年   25123篇
  1999年   20599篇
  1998年   5436篇
  1997年   4710篇
  1996年   5045篇
  1995年   4632篇
  1994年   4322篇
  1993年   4138篇
  1992年   15754篇
  1991年   16336篇
  1990年   16441篇
  1989年   15821篇
  1988年   14599篇
  1987年   14444篇
  1986年   13630篇
  1985年   12997篇
  1984年   9637篇
  1983年   8263篇
  1982年   4566篇
  1981年   4237篇
  1979年   9437篇
  1978年   6864篇
  1977年   5778篇
  1976年   5608篇
  1975年   6399篇
  1974年   7639篇
  1973年   7139篇
  1972年   6966篇
  1971年   6693篇
  1970年   6178篇
  1969年   5900篇
  1968年   5567篇
  1967年   5014篇
  1966年   4454篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
91.
Oncologic screenings of the populations in the areas with increased incidence of esophageal cancer have revealed Barrett's ulcer in 1 percent of the examinees. Endoscopic and cytologic characteristics of this condition are presented. Precancer changes--severe dysplasia--are most frequent in male Kazakhs (14.1 percent) aged 50 to 59 (14.7 percent). Subjects with Barrett's ulcer developing severe dysplasia, as evidenced by cytograms, should be included in the group of subjects at risk for carcinoma of the lower third of the esophagus and cardia.  相似文献   
92.
93.
94.
Invasive monitoring is an important aspect of the care of the infant or child with multisystem organ dysfunction or severe acute respiratory failure. The indications for these procedures in children vary little from current recommendations for adults. The size, anatomy, physiologic responses, and pathophysiologic processes in children frequently require modifications in the placement and maintenance of these lines, and in the interpretation of the data. The literature suggests that although the absolute numbers may vary, broad therapeutic goals may be identified and treated in pediatric patients as in older patients.  相似文献   
95.
Angiotensin-converting enzyme (ACE) was studied immunohistochemically in conjunctival biopsies from 6 patients with systemic sarcoidosis, 4 patients with posterior non-sarcoid uveitis and in specimens from 4 patients with chalazion of the eyelid. Specimens with sarcoid granulomas showed intense ACE-positive immunoreactivity in epitheloid cells of the granuloma, whereas chalazion granulomas did not contain ACE-immunoreactivity. There was no difference in staining patterns between specimens without granulomas. Thus immunohistochemical staining for ACE may be of help in differentiating conjunctival granulomatous tissue of a chalazion from sarcoid granuloma.  相似文献   
96.
97.
Nerve growth factor (NGF) gene expression in central nervous system (CNS) glia appears to be associated with active glial growth. To study the underlying molecular mechanisms, we examined the effects of a number of growth-related factors on NGF mRNA expression in glial cultures. Our results suggest that glial membrane interaction, as a consequence of growth, actively inhibits NGF gene expression in CNS glia.  相似文献   
98.
Three isoforms of human tau protein were compared for their abilities to induce microtubule assembly. The three isoforms, tau 3 (tau containing three microtubule-binding domains), tau 4 (tau containing four microtubule-binding domains) and tau 4L (tau containing four microtubule binding domains plus a 58-amino-acid insert near the N-terminus) were expressed in E. coli and purified using ammonium sulfate precipitation, ion exchange, and size exclusion chromatography. All three isoforms induced microtubule assembly at micromolar concentrations and showed similar critical concentrations for assembly of 0.4-0.45 microM. However, tau 4 induced microtubule formation at a rate five- to tenfold faster than either tau 3 or tau 4L. The rate of microtubule elongation seen with tau 4 was twofold greater than with tau 3 or tau 4L, suggesting that the faster rate of microtubule assembly seen with tau 4 was due, at least in part, to faster elongation. Tau 4 induced a greater number of microtubules to form at steady state than did tau 3 or tau 4L. The microtubules generated with each tau isoform had similar steady-state length distributions and were equally susceptible to cold-induced disassembly. These results indicate that the additional microtubule-binding domain in tau 4 enhances microtubule assembly, while the 58-amino-acid insert negates the stimulatory effect of the fourth microtubule-binding domain.  相似文献   
99.
100.
Thirty gallium scans, using currently acceptable dosage levels (5-6 mCi) and a conventional rotating gamma camera, were performed on 20 patients with lymphoma or infection. Compared to planar scans, SPECT increased sensitivity and lesion detection from 48% to 89% in lymphoma, and from 50% to 80% in infection. The predictive value of a negative site was 81% in lymphoma and 67% in infection. Gallium utility is markedly increased by SPECT imaging. A normal gallium SPECT scan is highly accurate in ruling out disease.  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