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   1527215篇
  免费   96665篇
  国内免费   1818篇
耳鼻咽喉   20962篇
儿科学   48703篇
妇产科学   39558篇
基础医学   232680篇
口腔科学   40478篇
临床医学   137077篇
内科学   284427篇
皮肤病学   34378篇
神经病学   110447篇
特种医学   60007篇
外国民族医学   254篇
外科学   230615篇
综合类   28043篇
现状与发展   3篇
一般理论   361篇
预防医学   108171篇
眼科学   34955篇
药学   121324篇
  8篇
中国医学   3700篇
肿瘤学   89547篇
  2018年   16150篇
  2017年   12409篇
  2016年   14181篇
  2015年   15757篇
  2014年   21344篇
  2013年   31233篇
  2012年   44012篇
  2011年   47191篇
  2010年   27530篇
  2009年   25461篇
  2008年   43441篇
  2007年   47098篇
  2006年   47194篇
  2005年   44986篇
  2004年   43339篇
  2003年   41677篇
  2002年   40216篇
  2001年   78239篇
  2000年   80161篇
  1999年   66487篇
  1998年   16881篇
  1997年   14675篇
  1996年   14690篇
  1995年   13761篇
  1994年   12421篇
  1993年   11924篇
  1992年   49836篇
  1991年   49480篇
  1990年   49102篇
  1989年   47496篇
  1988年   43037篇
  1987年   42086篇
  1986年   39393篇
  1985年   37290篇
  1984年   27191篇
  1983年   23053篇
  1982年   12405篇
  1979年   24817篇
  1978年   16950篇
  1977年   14714篇
  1976年   13617篇
  1975年   15884篇
  1974年   18213篇
  1973年   17626篇
  1972年   16637篇
  1971年   15754篇
  1970年   14570篇
  1969年   13897篇
  1968年   12581篇
  1967年   11289篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
Effect of intracoronary infusion of diltiazem (1 microgram/min) on regional myocardial blood flow (RMBF) was studied using 15-microns radioactive microspheres in 11 excised cross-circulated canine left ventricles. With total coronary blood flow (CBF) and heart rate (HR) held constant, regional ischemia was induced by ligating the left anterior descending coronary artery (LAD). Diltiazem at the dose used had no effects on ventricular Emax before and after LAD ligation. RMBF expressed by the counts divided by the counts averaged in all segments in each layer significantly (p less than 0.05) increased under diltiazem only in the low-flow region that had less than 50% RMBF before diltiazem; from 21% (+/- 12%) to 35% (+/- 18%) in the epicardial, from 22% (+/- 12%) to 32% (+/- 18%) in the midwall, and from 24% (+/- 10%) to 31% (+/- 12%) in the endocardial layers. We conclude that the beneficial effect of diltiazem on the ischemic heart involves a direct action on the coronary vascular system and does not necessarily depend on the concomitant changes in hemodynamics.  相似文献   
962.
Clinical pharmacokinetics-pharmacodynamics of anticancer drugs   总被引:3,自引:0,他引:3  
  相似文献   
963.
A new macrolide antibiotic, clarithromycin (TE-031, A-56268), was studied for its clinical efficacy in the field of pediatrics. Patients treated were infants and children ranging from 2 months to 11 years old suffering from acute bronchitis in 5 cases, acute tonsillitis in 2 cases, Mycoplasma pneumonia in 2 cases, pertussis in 6 cases, scarlatina in 1 case and acute enteritis in 2 cases, a total of 18 cases. TE-031 was administered 19.7-43.5 mg/kg in daily doses and lengths of treatment ranged from 4 to 19 days. As regards to its clinical efficacy, good or excellent results were obtained in all cases: excellent in 11 cases and good in 7 cases. No clinical side effects nor abnormal laboratory test values obviously attributable to TE-031 were observed.  相似文献   
964.
Hemodynamic changes after isolated impairment of right ventricular function (produced by increasing afterload by temporary banding of the pulmonary artery) were studied in 22 ventilated pigs during increased levels of positive end-expiratory pressure (4, 8, 12, and 16 cm H2O). In the open chest group, application of positive end-expiratory pressure produced only a slight decrease of cardiac index. After right ventricular damage a decrease of cardiac index of more than 25% occurred only when higher levels of positive end-expiratory pressure were applied. In contrast to the open chest group, the closed chest group showed more distinct cardiovascular responses after positive end-expiratory pressure. In the damaged right ventricle with a positive end-expiratory pressure of 16 cm H2O, right ventricular end-diastolic pressure increased more than 100%. With positive end-expiratory pressure, cardiac index decreased 34% before and 47% after right ventricular damage. We conclude that positive end-expiratory pressure induces a more pronounced decrease in cardiac index if right ventricular function is impaired. During open chest conditions with lower levels of positive end-expiratory pressure, these changes are only small, however, and probably irrelevant. During closed chest conditions, the hemodynamic changes are much more pronounced. High right ventricular end-diastolic pressures resulting from impaired right ventricular contractility as well as from high levels of positive end-expiratory pressure may have an impact on biventricular function and right ventricular coronary driving pressure.  相似文献   
965.
966.
We describe an improved synthesis and properties of fluphenazine-mustard, a potent phenothiazine having an alkylating chlorethylamine chain in its structure. The drug possesses anticalmodulin activity equivalent to the parent compound, but unlike fluphenazine dihydrochloride, the mustard derivative irreversibly antagonizes the ability of calmodulin to activate cyclic nucleotide phosphodiesterase. This property is partially calcium-dependent and can be overcome by coincubation with excess fluphenazine dihydrochloride. The compound irreversibly inactivated calmodulin when incubated with intact cells and caused single-stranded breakage of DNA. Fluphenazine-mustard possesses potent antiproliferative and cytotoxic properties against malignant cell lines that are likely to be mediated through both of these actions.  相似文献   
967.
Exercise and work potential of a patient with coexistent myophosphorylase and myoadenylate deaminase (AMPDA) deficiency was compared with that of three patients with myophosphorylase deficiency alone. The patient with the combined defect failed to produce an abnormal rise in serum ammonia or hypoxanthine as seen in the other patients after forearm exercise. Maximum oxygen consumption and work rates during cycle ergometer testing were similar in all patients, but well below controls. The occurrence of two defects involving short-term energy metabolism in muscle presents an opportunity to define further the metabolic role of AMPDA.  相似文献   
968.
The paper describes the examinations of 353 patients with various cardiovascular pathologies and changes in the end-portion of the ECG ventricular complex. For that purpose potassium chloride, obsidan, orthostatic and hyperventilation tests were used. The examinations demonstrated that the ECG changes were of functional nature in 178 patients, of organic nature in 155 patients and of mixed nature in 20 patients which was important for reliable diagnostic and expertise conclusions.  相似文献   
969.
Congenital esophageal cysts in adults   总被引:1,自引:0,他引:1  
Sixteen adult patients with congenital esophageal cysts were operated on between 1957 and 1979. Preoperatively, 7 patients (44%) were asymptomatic and the cyst was found incidentally on a routine chest roentgenogram. Esophageal symptoms were present in only 3 patients (19%), whereas most symptomatic patients had precordial sensations or arrhythmias. A correct preoperative diagnosis was made in only 1 patient. After enucleation of the cyst, preoperative symptoms were alleviated in all patients and short-term results were excellent. However, long-term follow-up 13.2 +/- 5.6 (+/- standard deviation) years later revealed moderate reflux in 9 (64%) of the surviving 14 patients. During esophagoscopy, macroscopic esophagitis was found in 12 (92%) of 13 patients. On histological examination of specimens obtained by forceps biopsy, esophagitis was present in 10 (77%) of 13 patients and included Barrett esophagus in 2. We conclude that, despite excellent early results, long-term follow-up of patients who undergo operation for congenital esophageal cysts is indicated because of the increased incidence of reflux esophagitis.  相似文献   
970.
The work gives substantiation of using complete intestinal lavage for certain indications in the complex treatment of incompetent colonic anastomoses. The method was efficiently used in 6 patients.  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