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   1419396篇
  免费   116227篇
  国内免费   6710篇
耳鼻咽喉   18264篇
儿科学   45474篇
妇产科学   38548篇
基础医学   194110篇
口腔科学   39769篇
临床医学   126403篇
内科学   297805篇
皮肤病学   34326篇
神经病学   116928篇
特种医学   57121篇
外国民族医学   275篇
外科学   219581篇
综合类   32055篇
现状与发展   2篇
一般理论   440篇
预防医学   115376篇
眼科学   29541篇
药学   99434篇
  5篇
中国医学   2737篇
肿瘤学   74139篇
  2019年   11533篇
  2018年   16459篇
  2017年   12468篇
  2016年   14597篇
  2015年   16358篇
  2014年   22943篇
  2013年   33809篇
  2012年   42315篇
  2011年   45391篇
  2010年   27866篇
  2009年   26727篇
  2008年   41066篇
  2007年   43667篇
  2006年   44417篇
  2005年   42939篇
  2004年   40766篇
  2003年   39504篇
  2002年   37149篇
  2001年   67649篇
  2000年   69656篇
  1999年   58033篇
  1998年   17203篇
  1997年   15414篇
  1996年   16301篇
  1995年   16521篇
  1994年   15339篇
  1993年   14331篇
  1992年   47695篇
  1991年   46220篇
  1990年   44417篇
  1989年   42165篇
  1988年   39099篇
  1987年   38395篇
  1986年   36139篇
  1985年   34887篇
  1984年   26528篇
  1983年   22283篇
  1982年   13960篇
  1981年   12580篇
  1980年   11816篇
  1979年   23694篇
  1978年   17190篇
  1977年   14448篇
  1976年   13257篇
  1975年   13800篇
  1974年   16228篇
  1973年   15485篇
  1972年   14257篇
  1971年   13145篇
  1970年   11972篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A case of esthesioneuroblastoma with an unusual clinical and radiographic presentation is reported. The presenting symptoms as well as the computed tomographic examination were compatible with a primary intracranial mass.  相似文献   
992.
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   
993.
The diagnosis of hysteria is often incorrect and must be made with great caution. A retrospective study demonstrates that an erroneous diagnosis of hysteria is most likely to be given to females, the psychiatrically ill, patients who embellish and patients who present plausible psychogenic explanations for their illness. Movement disorders and paralysis are the neurologic disorders most frequently mislabeled as hysteria.  相似文献   
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.
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   
996.
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   
997.
This case report illustrates the magnetic resonance imaging (MRI) appearance of a typically asymptomatic renal oncocytoma as a homogeneous mass of medium signal with a stellate central region of decreased signal, representing the central scar. The MRI was correlated with computed tomography (CT), ultrasound (US), and gross pathologic appearance. The appearance of a central scar is not specific for oncocytoma and does not exclude renal cell carcinoma, as illustrated by a second case.  相似文献   
998.
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   
999.
1000.
Effect on mortality of inhalation injury   总被引:5,自引:0,他引:5  
A retrospective analysis of 1,018 consecutive admissions with cutaneous burn injury over 32 months was carried out. Mortality probabilities as related to age, per cent TBSA burn, and presence of inhalation injury are presented. Incidence of and mortality from inhalation injury both rose with increasing burn area. The incidence of inhalation injury also rose with advancing age; mortality was lowest in the 5- to 14-year old age group and highest in those more than 59 years of 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