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   2338987篇
  免费   183590篇
  国内免费   7304篇
耳鼻咽喉   30240篇
儿科学   76302篇
妇产科学   64593篇
基础医学   333946篇
口腔科学   64983篇
临床医学   215799篇
内科学   466836篇
皮肤病学   53702篇
神经病学   190972篇
特种医学   91276篇
外国民族医学   522篇
外科学   348785篇
综合类   52619篇
现状与发展   5篇
一般理论   930篇
预防医学   192302篇
眼科学   51477篇
药学   167751篇
  9篇
中国医学   3916篇
肿瘤学   122916篇
  2018年   24021篇
  2016年   21667篇
  2015年   24478篇
  2014年   34090篇
  2013年   51780篇
  2012年   66271篇
  2011年   71142篇
  2010年   43012篇
  2009年   41714篇
  2008年   67005篇
  2007年   71612篇
  2006年   72156篇
  2005年   70243篇
  2004年   67209篇
  2003年   64994篇
  2002年   62454篇
  2001年   106406篇
  2000年   109031篇
  1999年   91701篇
  1998年   27252篇
  1997年   24561篇
  1996年   25563篇
  1995年   25152篇
  1994年   23393篇
  1993年   21992篇
  1992年   75226篇
  1991年   73586篇
  1990年   71190篇
  1989年   68253篇
  1988年   63317篇
  1987年   62291篇
  1986年   58918篇
  1985年   56572篇
  1984年   43061篇
  1983年   36992篇
  1982年   22746篇
  1981年   20570篇
  1980年   19374篇
  1979年   40061篇
  1978年   29269篇
  1977年   24652篇
  1976年   22667篇
  1975年   24151篇
  1974年   28900篇
  1973年   28053篇
  1972年   26154篇
  1971年   24301篇
  1970年   22570篇
  1969年   21249篇
  1968年   19856篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
An unusual, elongated, refractile cell morphology was observed in keratinocytes cultured from three patients with non-lethalis forms of junctional epidermolysis bullosa (JEB). To determine whether these changes might be related to altered cell adhesion, keratinocyte strains established from one patient were examined for adhesive, structural, and functional characteristics. JEB keratinocytes expressed keratin tonofilaments, as determined by staining with AE1 monoclonal antibodies and direct observation of tonofilaments by electron microscopy. JEB keratinocytes showed diminished cell-substratum adhesions, judged by interference reflection microscopy. Areas of diminished cell-substratum adhesion corresponded to F-actin-rich cell adhesions (focal adhesions) and not to cellular areas that abundantly express hemidesmosomal antigens. Analysis of cell-substratum adhesion by electron microscopy revealed extensive areas of cell-substratum separation in JEB keratinocytes that were not present in normal keratinocytes maintained in serum-free medium. Normal keratinocytes displayed numerous regions of focal contact between the ventral plasma membrane and the culture substratum, but these structures were not seen in JEB keratinocytes. Bundled actin filaments (stress fibers) were greatly diminished in expected regions of cell-substratum adhesion in JEB keratinocytes and, instead, displayed disorganized individual filaments. The growth rate of JEB keratinocytes was quite slow in culture, with a population doubling time of 2.7 d versus 1.5 d for normal keratinocytes under identical conditions. JEB keratinocytes also displayed a reduced ability to aggregate into colonies upon exposure to medium with increased extracellular calcium. JEB keratinocytes thus display adhesive, structural, and functional abnormalities that suggest this cell type may be central to the pathogenesis of junctional epidermolysis bullosa. Study of affected keratinocytes could be important to characterize associated molecular pathologies.  相似文献   
992.
993.
994.
The relations between manganese and atherosclerosis were examined on rabbits with experimental atherosclerosis, on patients with atherosclerosis and on workers exposed to manganese. Here a favourable influence of manganese was shown which effected a decrease of the cholesterol content of serum, liver and aorta and inhibited the entry of lipids into the aorta. The influence of the manganese on various enzymes as well as a manganese-copper interaction are discussed as possible causes.  相似文献   
995.
996.
In defining the linear extent of a malignant tumor in a long bone, radiographs, computerized tomography, and scintigraphy are routinely employed, especially when non-ablative surgery is being considered. The drawbacks of these modalities in defining the true intracompartmental extent of disease within a bone can largely be overcome with the use of magnetic resonance imaging. We did a prospective analysis of magnetic resonance imaging in sixteen consecutive patients with a primary malignant tumor of a long bone, and it showed that this modality has clinical promise of being more precise than the other modalities in defining the true proximal and distal extent of a tumor in a long bone. Coronal images permit easier planning of surgical techniques for salvage of a limb using an allograft than do a multiplicity of transverse images.  相似文献   
997.
998.
Basal isolated canine paw blood flow was equally distributed between arteriovenous anastomosis (AVA) and capillary circulations. Norepinephrine decreased AVA flow by 92% and capillary flow by 41%. Dopamine significantly reduced AVA flow by 94% compared to baseline with a 37% reduction in capillary flow. However, with alpha-adrenergic blockade dopamine decreased AVA flow 66% while capillary flow increased 42%. Isoproterenol increased capillary flow almost twofold and appeared to decrease AVA flow, although the latter was statistically insignificant. Differential effects of adrenergic and dopaminergic agonists on canine paw AVA and capillary blood flow suggest the existence of independent regulation of these components of the microcirculation.  相似文献   
999.
A case of cryptococcal meningoencephalitis, as presented by a hypertensive hydrocephalus, is described. To our knowledge, this is the 24th case described in Italy since 1953. The diagnosis was made with ventricular fluid examination: the patient was successfully treated with amphotericin B and 5-fluorocytosine, thus avoiding the risks of surgical treatment of hydrocephalus. Early diagnosis and proper therapy are necessary in order to decrease the high lethality of cryptococcosis.  相似文献   
1000.
The results of membranectomy and deep myectomy in the left ventricular outflow tract were compared to those of membranectomy and myotomy in 42 patients who underwent surgical repair of discrete and tunnel subaortic stenosis. Fifteen consecutive patients (Group A) underwent membranectomy and myotomy, and 27 consecutive patients (Group B) underwent membranectomy and myectomy. Two patients of Group A and nine of Group B had tunnel subaortic stenosis. The preoperative mean (+/- standard deviation) peak systolic gradients across the left ventricular outflow tract in patients with discrete subaortic stenosis types I and II were 64 +/- 29 mm Hg in Group A and 52 +/- 3 mm Hg in Group B (p = not significant). In the patients with tunnel subaortic stenosis the preoperative mean gradients were 97 +/- 74 mm Hg in Group A and 73 +/- 26 mm Hg in Group B (p = not significant). In patients with discrete subaortic stenosis types I and II, postoperative catheterization at a mean follow-up of 21 months revealed residual mean gradients of 29 +/- 24 mm Hg in Group A and 10 +/- 13 mm Hg in Group B (p less than 0.01). In the patients with tunnel subaortic stenosis, the postoperative mean gradients were 25 +/- 7 and 30 +/- 30 mm Hg in Groups A and B, respectively (p = not significant). We conclude that in the surgical management of discrete subaortic stenosis types I and II, deep myectomy (in addition to membranectomy) produces better relief of the left ventricular outflow obstruction than do membranectomy and myotomy. In patients with tunnel subaortic stenosis myectomy is less effective than in the non-tunnel type but still produces acceptable results and may delay radical procedures to a later age.  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