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   2653240篇
  免费   213256篇
  国内免费   7681篇
耳鼻咽喉   35135篇
儿科学   87578篇
妇产科学   73448篇
基础医学   369884篇
口腔科学   75010篇
临床医学   236067篇
内科学   528410篇
皮肤病学   58897篇
神经病学   219069篇
特种医学   107896篇
外国民族医学   721篇
外科学   409329篇
综合类   64115篇
现状与发展   5篇
一般理论   912篇
预防医学   212359篇
眼科学   58283篇
药学   191991篇
  8篇
中国医学   4594篇
肿瘤学   140466篇
  2018年   33924篇
  2017年   26914篇
  2016年   31329篇
  2015年   26328篇
  2014年   36432篇
  2013年   55000篇
  2012年   72687篇
  2011年   82785篇
  2010年   52102篇
  2009年   48595篇
  2008年   79020篇
  2007年   85210篇
  2006年   76853篇
  2005年   76055篇
  2004年   74236篇
  2003年   72671篇
  2002年   69230篇
  2001年   120432篇
  2000年   124296篇
  1999年   104510篇
  1998年   30563篇
  1997年   27684篇
  1996年   28224篇
  1995年   27954篇
  1994年   26295篇
  1993年   24697篇
  1992年   87067篇
  1991年   84869篇
  1990年   82183篇
  1989年   79080篇
  1988年   73554篇
  1987年   72449篇
  1986年   68613篇
  1985年   66334篇
  1984年   50268篇
  1983年   42854篇
  1982年   26134篇
  1981年   23430篇
  1980年   22142篇
  1979年   47001篇
  1978年   33366篇
  1977年   28205篇
  1976年   26287篇
  1975年   27655篇
  1974年   33326篇
  1973年   32021篇
  1972年   29484篇
  1971年   27571篇
  1970年   25327篇
  1969年   23801篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Mycobacteriosis due to Mycobacterium genavense in six pet birds.   总被引:11,自引:7,他引:4       下载免费PDF全文
Six cases of mycobacteriosis due to Mycobacterium genavense in three budgerigars (Melopsittacus undulatus), one orange-winged amazon (Amazona amazonica), one flycatcher (Cyanoptila cyanomelana), and one zebra finch (Taeniopygia guttata) are discussed. Gross lesions associated with the infection included a high degree of muscular wasting (five cases), hepatomegaly (four cases), and thickening of the wall of the small intestine (four cases). Granulomas were found in the lung (one case) and the subcutis (one case). Acid-fast bacilli were detected in the liver of all six birds. Only the use of acidic BACTEC mediums consistently led to growth, whereas the egg-based medium failed. These findings point to a possible role of the environment as a reservoir for M. genavense.  相似文献   
992.
993.
994.
This study surveyed male and female athletes from 22 midwesterncolleges and universities regarding behaviors and attitudesassociated with anorexia nervosa and bulimia nervosa. The responserate was 66% (N= 695) and the findings indicated that the bodyimage of some athletes may be distorted; one-seventh perceivedthemselves as fat even though they were not. Many athletes seemedpreoccupied with food and weight; almost one-third reportedroutinely thinking about food and weight and more than one-thirdreported dramatic annual weight fluctuations (9 lb or greater)related to bingeing and fasting. Athletes also did not feelin control when they ate and their habits related to food consumptionappeared to be extreme; one-tenth reported a lack of controlwhen they ate, more than one-third binged, one-twentieth ateuntil they were physically ill, and a similar proportion preferrednot to eat in the presence of others. In addition, it was foundthat as many men as women athletes reported these perceptionsbut significant sex differences were noted for specific items.It was suggested that behaviors and attitudes be viewed on acontinuum with normals at one end, eating disordered individuals at the other end,and college athletes in between. Health education that focuseson behaviors and attitudes as symptoms of eating disorders wasrecommended for athletes and those working closely with athletes.Future research was suggested to determine reasons for the undesirablebehaviors and attitudes and to study the onset, development,long-term effects and whether these behaviors and attitudeslead to an eating disorder.  相似文献   
995.
Incidence of hypertension in the Framingham Study.   总被引:6,自引:1,他引:5       下载免费PDF全文
Incidence and trends in incidence of definite hypertension were analyzed based on 30 years follow-up of 5,209 subjects in the Framingham Heart Study cohort. Based on pooling of 15 two-year periods, hypertension incidence per biennium increased with age in men from 3.3 per cent at ages 30-39 to 6.2 per cent at ages 70-79, and in women from 1.5 per cent at ages 30-39 to 8.6 per cent at ages 70-79. No consistent trend in incidence rates was evident for either sex from the 1950s through the 1970s. The proportion of hypertensive subjects receiving antihypertensive medication has increased since 1954-58 and exceeded 80 per cent for both men and women ages 60-89 years in 1979-81. Incidence data presented in this report may serve as a baseline for assessing the impact of future public health efforts in the primary prevention of hypertension.  相似文献   
996.
997.
The phytotoxicity of heavy metals and pesticides was studied by using the fluorescence induction from the alga Dunaliella tertiolecta. The complementary area calculated from the variable fluorescence induction was used as a direct parameter to estimate phytotoxicity. The value of this parameter was affected when algae were treated with different concentrations of mercury, copper, atrazine, DCMU, Dutox, and Soilgard. The toxic effect of these pollutants was estimated by monitoring the decrease in the complementary area, which reflects photosystem II photochemistry. Further, the authors have demonstrated the advantage of using the complementary area as a parameter of phytotoxicity over using variable fluorescence yield. The complementary area of algal fluorescence can be used as a simple and sensitive parameter in the estimation of the phytotoxicity of polluted water.  相似文献   
998.
999.
Eight-eight female weanling Sprague-Dawley rats were fed diets containing either 650 or 150 mg magnesium/kg diet and 7.0 or 3.5 mg pyridoxine-HCl/kg diet, in a 2 x 2 factorial arrangement, during growth, gestation, and lactation. The objective of the study was to determine whether concurrent dietary deficiencies of magnesium and pyridoxine were synergistic, additive, or antagonistic with regards to effects on reproductive performance, growth, and development of offspring, and tissue content of magnesium and calcium. Body weight of dams and pups was not different between groups until day 9 of lactation, at which point those animals in either low magnesium group weighed less than the other. Litter size and birth weight were not different. Development, as measured by timing of unfolding of the external ear, opening of both eyes, and clinical emergence of incisors, was delayed in pups from litters in the low magnesium groups. A synergistic effect on delay of onset of ear unfolding by deficiency of both magnesium and pyridoxine was observed. Calcium content of heart and kidney from dams was increased in the low magnesium groups. Renal calcium was not further increased by the level of pyridoxine deficiency in this study. The calcium to magnesium ratio in heart from pups was higher in those from litters in the low magnesium and pyridoxine group than in the others. Results indicate that simultaneous deficiencies of magnesium and pyridoxine may impair function synergistically. Because these two nutrients are often reported to be presented in inadequate amounts in diets of women in their reproductive years, the potential exists for impaired reproductive success.  相似文献   
1000.
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