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   1340375篇
  免费   94510篇
  国内免费   2928篇
耳鼻咽喉   19873篇
儿科学   40277篇
妇产科学   38738篇
基础医学   187713篇
口腔科学   39899篇
临床医学   112894篇
内科学   263504篇
皮肤病学   30266篇
神经病学   106975篇
特种医学   53797篇
外国民族医学   435篇
外科学   208971篇
综合类   31056篇
现状与发展   6篇
一般理论   436篇
预防医学   92115篇
眼科学   31447篇
药学   100409篇
  4篇
中国医学   2995篇
肿瘤学   76003篇
  2018年   11832篇
  2015年   11960篇
  2014年   16801篇
  2013年   25401篇
  2012年   33233篇
  2011年   35086篇
  2010年   20847篇
  2009年   20345篇
  2008年   33768篇
  2007年   36925篇
  2006年   37465篇
  2005年   36246篇
  2004年   35303篇
  2003年   34288篇
  2002年   33815篇
  2001年   63741篇
  2000年   65446篇
  1999年   55491篇
  1998年   14698篇
  1997年   13494篇
  1996年   12979篇
  1995年   12250篇
  1994年   11507篇
  1992年   42882篇
  1991年   41372篇
  1990年   40635篇
  1989年   39645篇
  1988年   37041篇
  1987年   36488篇
  1986年   34951篇
  1985年   33157篇
  1984年   24864篇
  1983年   21083篇
  1982年   12682篇
  1981年   11583篇
  1980年   10784篇
  1979年   23960篇
  1978年   17086篇
  1977年   14852篇
  1976年   13406篇
  1975年   15286篇
  1974年   18099篇
  1973年   17579篇
  1972年   16827篇
  1971年   15731篇
  1970年   14931篇
  1969年   14360篇
  1968年   13475篇
  1967年   12024篇
  1966年   11273篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
952.
953.
In recent years, epidemiologic and clinical studies, public and regulatory policy activity, and media coverage have focused on issues related to trans fats. To help increase awareness and understanding of trans fats and other fats, the American Heart Association (AHA) launched the “Face the Fats” national consumer education campaign in April 2007. The AHA commissioned a quantitative tracking survey between 2006 and 2007 to measure changes in consumer awareness, knowledge, and behaviors related fats and oils and their perceived impact on heart disease. The survey was conducted by Cogent Research. Data were collected during March 2006 and May 2007. At both time points, the survey included a representative sample of the American population age 18 to 65 years (n=1,000). The sampling plan for the survey was designed based on the 2000 and 2003 US Census. The margin of error was ±3.10 percentage points. Awareness of trans fats increased during the 1-year study period. In 2007, 92% of respondents were aware of trans fats, an increase from 84% in 2006 (P<0.05). The 2007 level was similar to the awareness of saturated fats (93%). Perceptions that certain fats and oils heighten the risk of heart disease increased for trans fats (73% in 2007 vs 63% in 2006; P<0.05), saturated fats (77% in 2007 vs 73% in 2006; P<0.05), and partially hydrogenated oils (56% in 2007 vs 49% in 2006; P<0.05). Knowledge about food sources of different fats remained low. On an unaided basis, 21% could name three food sources of trans fats in 2007, up from 17% in 2006 (P<0.05). Knowledge of food sources of saturated fat remained unchanged at 30% in 2007. Significantly more respondents in 2007 reported behavioral changes related to trans fat information, such as buying food products because they show “zero trans fat” on labels or packages (37% in 2007 vs. 32% in 2006; P<0.05). Between 2006 and 2007, consumer awareness about trans fats increased and attained awareness levels similar to saturated fats. The increased awareness is associated with improved self-reported behaviors in grocery shopping. Nonetheless, overall knowledge, especially regarding food sources of saturated and trans fats, remains relatively low, underscoring the need for heightened consumer education activities. The positive change in consumer awareness about trans fats is likely attributable to the wide range of messages available to them, including the AHA “Face the Fats” national consumer education campaign.  相似文献   
954.
955.
956.
957.
958.
959.
960.
The Blalock-Taussig operation is of benefit to any patient who suffers from lack of adequate pulmonary blood flow, provided the structure of the heart is such that it is able to adjust to the altered circulation.Experience has shown that a patient with a tetralogy of Fallot can adjust to the altered circulation. The other types of malformation which have been improved by operation are those with a cardiac contour similar to that of a tetralogy of Fallot with left axis deviation, those with partial rotation of the heart on its axis, possibly those with “pure” pulmonary stenosis and an auricular septal defect, and a few with unusual arrhythmias. In atypical cases an effort is made to determine whether the condition is such that the patient can be helped by increasing the circulation to the lungs.The six criteria essential for successful operation are (1) the primary difficulty must be lack of adequate pulmonary blood flow; (2) there must be a pulmonary artery to which to anastomose the systemic artery; (3) a systemic artery must be available for the anastomosis; (4) the difference in pressure between the systemic and pulmonic circulations must be sufficiently great for blood to flow from the aorta to the lungs; (5) the structure of the lungs must be such that the patient can tolerate the collapse of one lung and the temporary occlusion of one pulmonary artery; and (6) the structure of the heart must be such that it can adjust to the altered circulation. The methods for the determination of each of these factors are discussed.In an analysis of the structure of the heart it is emphasized that (1) venous blood must be directed to the systemic circulation, (2) the increased volume of oxygenated blood which is returned from the lungs must be able to reach the aorta; (3) the structure of the heart must be such as to permit the continuous circulation of the blood at an accelerated rate; (4) the structure of the heart must also be such that the operation does not cause progressive cardiac enlargement. Each of these factors is analyzed.The effect of the altered circulation on the size of the heart is discussed in the light of the long-time results of the operation. Less than 5 per cent of the patients have shown progressive cardiac enlargement or died of cardiac failure. Thirty per cent have shown no increase in heart size. Thirty per cent have shown increase in heart size during the first three weeks after operation and then have adjusted to the load, and 30 per cent have shown cardiac enlargement between the time of discharge and the six-month checkup and thereafter have shown no further increase in heart size.In general, the results from the use of the subclavian artery, as estimated by the oxygen saturation of the arterial blood, the red blood cell count, and the hemoglobin level, have been as beneficial as when the innominate artery has been used for the anastomosis and, moreover, this former group of patients has shown less increase in the size of the heart.A child with a tetralogy of allot has a 90 per cent chance of being greatly improved by the operation and an equally good chance of maintaining that improvement.  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