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   1344940篇
  免费   114912篇
  国内免费   6373篇
耳鼻咽喉   16807篇
儿科学   43168篇
妇产科学   37042篇
基础医学   185064篇
口腔科学   36455篇
临床医学   121052篇
内科学   280883篇
皮肤病学   32092篇
神经病学   111015篇
特种医学   55659篇
外国民族医学   274篇
外科学   211300篇
综合类   31546篇
现状与发展   2篇
一般理论   415篇
预防医学   107365篇
眼科学   28160篇
药学   94458篇
  5篇
中国医学   2281篇
肿瘤学   71182篇
  2018年   13439篇
  2017年   10672篇
  2016年   12839篇
  2015年   14361篇
  2014年   20007篇
  2013年   29828篇
  2012年   36921篇
  2011年   39824篇
  2010年   24617篇
  2009年   24041篇
  2008年   37013篇
  2007年   39542篇
  2006年   40706篇
  2005年   39261篇
  2004年   37599篇
  2003年   36583篇
  2002年   34623篇
  2001年   66497篇
  2000年   68544篇
  1999年   56981篇
  1998年   16752篇
  1997年   15030篇
  1996年   16018篇
  1995年   16241篇
  1994年   15110篇
  1993年   14158篇
  1992年   47110篇
  1991年   45757篇
  1990年   43979篇
  1989年   41825篇
  1988年   38768篇
  1987年   38090篇
  1986年   35866篇
  1985年   34644篇
  1984年   26365篇
  1983年   22110篇
  1982年   13848篇
  1981年   12449篇
  1980年   11720篇
  1979年   23547篇
  1978年   17074篇
  1977年   14385篇
  1976年   13183篇
  1975年   13724篇
  1974年   16100篇
  1973年   15398篇
  1972年   14176篇
  1971年   13040篇
  1970年   11884篇
  1969年   11101篇
排序方式: 共有10000条查询结果,搜索用时 359 毫秒
911.
912.
To assess the adequacy of the nutritional care provided, a prospective noninterventional study was carried out on 250 randomly selected patients aged 65 and over who were admitted to a Veterans Administration Hospital. Of this group, 97 patients (39%) were found to be at high risk of having clinically significant protein-energy malnutrition. In 43 cases (17%), an assessment of the patient's nutritional status was not possible because the available data were inadequate. No patient had a diagnosis of malnutrition recorded on the problem list. Only 13 percent of the high-risk patients received some form of nutrition support therapy; 10 (10%) received oral supplements, and four (4%) were started on enteral feedings. Patients who received enteral feedings experienced a high rate of complications resulting from use of the feeding tubes. Over all, none of the high risk study patients received optimal nutrition support therapy. These findings indicate that elderly patients hospitalized in the Veterans Administration hospital in this study are usually not screened appropriately for protein-energy malnutrition, the diagnosis is frequently missed or ignored, and nutrition support therapy is underutilized and often ineffectually managed.  相似文献   
913.
Myelographic study of the spinal cord ascent during fetal development   总被引:2,自引:0,他引:2  
To assess the length of the spinal cord relative to the vertebral column during fetal development, we performed translumbar myelograms on 340 spontaneously aborted fetuses. Of these, 146 were selected for study. There were 76 males and 70 females, with fetal age ranging from 7 to 33 weeks. Significant variation in the level of spinal cord termination was found in fetuses between 12 and 25 weeks gestational age. In fetuses between 25 and 33 weeks gestational age, the cord ended at or above the third lumbar vertebra.  相似文献   
914.
Fine Needle Aspiration Cytology (F.N.A.C.) has been used as a diagnostic tool by the ENT departments in Tayside since the end of 1985. This paper discusses the results of our initial experience with this and outlines some of the diagnostic pitfalls. This is a useful and accurate procedure with many advantages over diagnostic biopsy.  相似文献   
915.
916.
Lung cancer is the leading cause of cancer deaths in both men and women in the United States. Treatment depends on the type and stage of lung cancer. For stage I and II cancer, surgery is usually the treatment of choice. Radiation therapy is used in patients who are considered poor risks for surgical resection. Intraoperative brachytherapy is an effective alternative to external irradiation in this group of patients. From 1958 to 1984, 55 patients with non-small-cell lung cancer were explored at Memorial Sloan Kettering Cancer Center and found to have surgical stage I or II tumors, which were considered to be unresectable mainly because of severe obstructive pulmonary disease precluding adequate resection. All these patients were treated with intraoperative brachytherapy at the time of the thoracotomy. Forty-four percent of these patients received in addition external irradiation, mainly to the mediastinum. The overall 5-year survival calculated by the Kaplan-Meier Method was 32%, and the local disease-free survival was 63%. Cox regression multivariant analysis demonstrated that there is a distinct subgroup with a better prognosis based on tumor site and patient's age--ie, patients who were younger than 58 years of age and had right-side lesions.  相似文献   
917.
Specific pathogen-free rats were exposed to the cigarette smoke (CS) of 25 cigarettes daily for 14 days and concurrently given N-acetylcysteine (Nac) as 1% of their drinking water (average daily dose 973 mg/kg). The thickness of the epithelium was measured at four airway levels and the numbers of mucus-containing secretory cells, stained for neutral or acidic glycoprotein (NGP or AGP respectively), were counted in surface epithelium at eight airway levels. Cigarette smoke increased the thickness of the epithelium at three of the airway levels studied by between 37 and 72%. The number of secretory cells was increased at all airway levels distal to the upper trachea by between 102 and 421%. Secretory cells containing NGP were reduced in number but this was more than offset by a large increase in the number of secretory cells containing AGP at all airway levels. N-acetylcysteine inhibited CS-induced epithelial thickening. Nac also inhibited the CS-induced increase in the number of secretory cells with AGP, but had little effect on the CS-induced reduction in the number of cells with NGP. Thus, prophylactic oral N-acetylcysteine led to an overall inhibition of CS-induced mucous cell hyperplasia and epithelial hypertrophy. The results suggest a novel anti-inflammatory action for a drug with known mucolytic effects.  相似文献   
918.
With some, but not all, types and intensities of exercise, lactate accumulates in the blood and in the muscles engaged in the exercise. A great deal of attention has been directed towards attempting to understand the dynamics of lactate production and removal at the onset of exercise, during exercise, and during the recovery process following exercise. It has been hoped that an unravelling of these events would provide a key to understanding cellular metabolism and its regulation during exercise. The purpose of this introductory paper to a symposium on lactate is to present a brief overview of some of the conditions that influence the rate and magnitude of lactate accumulation during exercise. It is pointed out that many conditions influence the rate and magnitude of the accumulation of lactate in blood and muscles. Included are diet, state of physical fitness, and the type and duration of the exercise. We have cautioned against trying to evaluate the state of oxygen delivery to muscle and the state of tissue oxygenation from the appearance of lactate in blood. We have pointed out the positive aspects of lactate production based on how it augments the cellular supply of ATP, thereby allowing for high intensity exercise, and also the negative aspects that develop as a result the reduction in pH which adversely influences many cellular processes essential for muscular activity.  相似文献   
919.
The rearranged genes encoding immunoglobulin heavy (mu) and light (kappa) chains specific for the hapten 2,4,6-trinitrophenyl (Tnp) were introduced into a B-lymphoma line that bears surface IgG with an unknown specificity and expresses surface Ia molecules. A transformant expressing surface IgM specific for Tnp was obtained. The transformant was found to present Tnp-proteins to antigen (protein)-specific T cells far more efficiently than the parenteral B-lymphoma line. This artificial system, utilizing recombinant DNA technology and gene transfer, provides several approaches for the study of T-cell-B-cell interactions.  相似文献   
920.
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