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   3628447篇
  免费   299315篇
  国内免费   14416篇
耳鼻咽喉   49265篇
儿科学   115209篇
妇产科学   94399篇
基础医学   573162篇
口腔科学   95971篇
临床医学   326770篇
内科学   649031篇
皮肤病学   94756篇
神经病学   313176篇
特种医学   140936篇
外国民族医学   498篇
外科学   554508篇
综合类   109106篇
现状与发展   25篇
一般理论   2457篇
预防医学   304735篇
眼科学   83447篇
药学   248422篇
  22篇
中国医学   10635篇
肿瘤学   175648篇
  2021年   55892篇
  2020年   35577篇
  2019年   58685篇
  2018年   72609篇
  2017年   55501篇
  2016年   61453篇
  2015年   75209篇
  2014年   109640篇
  2013年   175216篇
  2012年   106915篇
  2011年   108552篇
  2010年   120662篇
  2009年   124215篇
  2008年   94983篇
  2007年   99735篇
  2006年   109531篇
  2005年   104953篇
  2004年   106074篇
  2003年   96225篇
  2002年   85411篇
  2001年   118595篇
  2000年   111984篇
  1999年   107929篇
  1998年   67124篇
  1997年   64584篇
  1996年   62341篇
  1995年   57742篇
  1994年   51704篇
  1993年   48227篇
  1992年   74445篇
  1991年   70103篇
  1990年   65818篇
  1989年   64637篇
  1988年   59573篇
  1987年   58282篇
  1986年   54818篇
  1985年   54628篇
  1984年   49697篇
  1983年   45236篇
  1982年   42356篇
  1981年   39707篇
  1980年   37386篇
  1979年   40374篇
  1978年   35691篇
  1977年   32384篇
  1976年   29721篇
  1975年   28033篇
  1974年   29129篇
  1973年   28147篇
  1972年   26320篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
993.
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   
994.
995.
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   
996.
We report a prevalence study of the best visual acuity in the affected eye of 100 selected patients with herpetic keratitis seen during a two-year period. Sixty-two patients retained an acuity of 6/9 or better without requiring penetrating keratoplasty (PK). The prevalence of reduced visual acuity severe enough to warrant PK was 33%. Patients requiring PK for whom full clinical records were available suffered a mean of 6.8 episodes of keratitis. In this group of patients the vision of 18 fell from 6/6 to 6/60 over a mean period of 8.5 years. Once visual acuity was permanently reduced to 6/12, 78% of patients proceeded to lose vision to 6/60. Unilateral visual impairment occurs in at least a third of patients with severe herpetic keratitis. Once vision falls permanently to 6/12, the long-term prognosis for vision appears to be poor.  相似文献   
997.
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   
998.
999.
The response of single detergent treated bovine retinal pigment epithelial cells in culture to ATP was measured with an image analyser. The most pronounced contraction was produced by 1.0 mM ATP with most change taking place in the first 10 min. At 1 h the area had decreased by about 33%, perimeter 22% and maximum length 25%. By way of comparison rabbit skin fibroblasts had a decreased area of approximately 40%, perimeter 25% and maximum length 22%. Bovine aortic smooth muscle cells on the other hand decreased in area by 55%, perimeter 40% and maximum length 36%. It is hoped that this assay may be used to evaluate drugs which could counteract contractile events in proliferative vitreoretinopathy.  相似文献   
1000.
Treatment versus no treatment in chronic open angle glaucoma   总被引:1,自引:0,他引:1  
In a controlled randomized study 15 patients (20 eyes) with chronic open angle glaucoma and visual field defects were followed by greater than 1 year, 12 of them were followed for 3 years. Half of the group were untreated controls, the other half treated with pressure reducing medical therapy. At least 5 consecutive computerized visual fields were recorded (COMPETER) on each eye, and the linear regression coefficient was calculated. With the reservation for uncontrolled compliance no significant difference in the line of favourable effect of pressure reduction could be spotted, in spite of an average pressure reduction in the treated group of 4 mmHg. More important than this result, which is open to criticism for the smallness of the material, uncontrolled compliance etc, is the lesson that a randomized experiment with treated and non-treated glaucoma cases carried out in accordance with the Helsingfors convention is hardly feasible.  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