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   3554034篇
  免费   299851篇
  国内免费   15210篇
耳鼻咽喉   49995篇
儿科学   108598篇
妇产科学   92620篇
基础医学   548284篇
口腔科学   99442篇
临床医学   328054篇
内科学   632688篇
皮肤病学   97270篇
神经病学   304652篇
特种医学   141131篇
外国民族医学   453篇
外科学   559566篇
综合类   107204篇
现状与发展   98篇
一般理论   2262篇
预防医学   289541篇
眼科学   82162篇
药学   243398篇
  23篇
中国医学   10356篇
肿瘤学   171298篇
  2021年   56062篇
  2020年   37955篇
  2019年   58824篇
  2018年   74961篇
  2017年   58544篇
  2016年   64554篇
  2015年   78631篇
  2014年   115477篇
  2013年   181003篇
  2012年   92471篇
  2011年   91613篇
  2010年   120493篇
  2009年   127391篇
  2008年   79585篇
  2007年   82281篇
  2006年   93998篇
  2005年   88376篇
  2004年   90136篇
  2003年   81242篇
  2002年   71479篇
  2001年   110788篇
  2000年   103371篇
  1999年   102563篇
  1998年   67045篇
  1997年   64649篇
  1996年   61870篇
  1995年   57137篇
  1994年   51007篇
  1993年   47552篇
  1992年   72160篇
  1991年   68525篇
  1990年   65409篇
  1989年   64725篇
  1988年   60531篇
  1987年   59125篇
  1986年   56608篇
  1985年   56156篇
  1984年   50604篇
  1983年   45872篇
  1982年   42406篇
  1981年   39846篇
  1980年   37680篇
  1979年   42969篇
  1978年   37388篇
  1977年   34314篇
  1976年   31067篇
  1975年   30710篇
  1974年   32426篇
  1973年   31094篇
  1972年   29531篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Acetaldehyde, the first metabolite of ethanol, reacts with haemoglobinin vitro to produce acetaldehyde—haemoglobin adducts.Some clinical studies on the minor haemoglobins have suggestedthat these adducts may be formed in people abusing alcohol.Under hydrolysis of haemoglobin, with oxalic acid at 100°Cin sealed vials, some acetaldehyde was released and then specificallydetermined by HPLC. The kinetics of hydrolysis were studiedusing haemoglobin previously labelled with 14[C] acetaldehyde.The maximum liberation of 14[C] acetaldehyde was obtained after3 hr 30 min hydrolysis and this time factor was then utilizedin the analysis of alcoholic and control haemoglobin. Thus,we have confirmed the formation of acetaldehyde haemoglobinadducts in vivo. It must be noted that the released acetaldehydecorresponds only to an index of the stable adducts. The levelswere higher in alcoholics than in controls (1.417±0.171and 1.295±0.139 nmol/mg Hb, respectively, P<0.001).In conclusion, this marker is not a convenient tool for themonitoring of alcohol exposure levels because of the low differencesbetween alcoholic and control haemoglobins.  相似文献   
992.
To determine the potential effect of screening on referral patterns, an adult population sample (4,404 men, 5,164 women, 20-69 years of age) was systematically recruited and screened for hypercholesterolemia and then analyzed by different cholesterol referral recommendations. Using levels suggested by the Lipid Research Clinics Coronary Primary Prevention Trial (greater than or equal to 265 mg/dL), 7.3% of men and 5.8% of women would be referred for follow-up. With the suggested recommendations of the National Cholesterol Education Program (NCEP), (greater than or equal to 200 mg/dL), 49.2% of men and 40.2% of women would be referred. The use of age-related definitions of the NIH Consensus Conference on Lipid Lowering results in 28.0% referrals in men and 21.8% in women. From this population, hypercholesterolemia subjects (greater than or equal to 265 mg/dL at screening; n = 624) were invited for a second cholesterol determination (58% returned), which found 36% below the 265 mg/dL level. Population screening for cholesterol is likely to produce large numbers of patients for follow-up, with the actual numbers strongly dependent on cutoff levels and age-sex distributions. Referral and follow-up of these patients may place a significant load on an unprepared health care community.  相似文献   
993.
Routine clinical chemical variables and parameters of the vitamin, iron and zinc status were measured in 20 female patients with anorexia nervosa (AN) and in 10 lean and 10 normal weight, healthy, female control subjects. Patients with AN had higher activities of L-gamma-glutamyl transferase (gamma-GT) and glutamate pyruvate transaminase (SGPT) and a higher concentration of prealbumin in serum and lower leucocyte and lymphocyte counts in blood. For the other routine clinical chemical parameters no significant differences between the groups were observed. AN patients had higher serum vitamin B12 and retinol levels. No significant differences were found for the status parameters of thiamin, vitamin B6, vitamin C, folate, vitamin E and vitamin D. Contradictory results were obtained for the riboflavin status: AN patients had a lower level of flavin adenine dinucleotide (FAD) in blood and a lower stimulation ratio of the glutathione reductase activity in erythrocytes (alpha-EGR). Patients with AN had higher serum ferritin concentration and lower total iron binding capacity (TIBC). However, haemoglobin (Hb), haematocrit (Ht) and iron saturation were not significantly different. No significant difference was found in the concentration of zinc in plasma. In spite of the poor intake of nutrients and energy, the results obtained did not indicate an inadequate status of vitamins, iron and zinc in patients with AN.  相似文献   
994.
995.
996.
Several million American children are currently unsupervised during the hours between school and parents' leaving for and/or return from the workplace. Many families would prefer other arrangements, but cost or availability factors present insurmountable barriers. Although growing, the public response continues to fall far short of the need; in the meantime, private entrepreneurs are moving to fill the gaps in available services. But if these programs for school-aged children are to serve functions other than the aggrandizement of their sponsors, they must be focused on the real needs that exist among real American children. Among the real children in need of care are those who are impoverished, unsupervised, unfit physically, unprepared for the demands of school and workplace, hurried into premature adulthood, and/or disconnected from the social worlds around them. Professional child and youth care workers with experience in day care and residential settings have the preparation needed to take leadership roles in creating developmentally appropriate, effective programs to meet the emerging demands for school-age child care and to weave them into a fabric of youth-centered community services.  相似文献   
997.
998.
Post-traumatic retinal detachment occurs frequently as a late consequence of progressive vitreous changes, especially following penetrating injuries. Occasionally, it develops soon after the trauma, without preceding proliferative vitreoretinopathy, is based on posterior vitreous detachment and morphologically resembles an idiopathic retinal detachment. It is possible that the posterior vitreous detachment in these cases is encouraged by the presence of intravitreal hemorrhage.  相似文献   
999.
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