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   3880701篇
  免费   308619篇
  国内免费   14634篇
耳鼻咽喉   54356篇
儿科学   124590篇
妇产科学   101893篇
基础医学   602978篇
口腔科学   106164篇
临床医学   346716篇
内科学   693520篇
皮肤病学   99765篇
神经病学   321898篇
特种医学   152560篇
外国民族医学   452篇
外科学   601348篇
综合类   113252篇
现状与发展   23篇
一般理论   2299篇
预防医学   321321篇
眼科学   90207篇
药学   270907篇
  24篇
中国医学   11494篇
肿瘤学   188187篇
  2021年   55704篇
  2020年   35570篇
  2019年   58645篇
  2018年   72828篇
  2017年   55545篇
  2016年   61250篇
  2015年   75244篇
  2014年   109638篇
  2013年   175045篇
  2012年   102503篇
  2011年   104759篇
  2010年   120535篇
  2009年   123661篇
  2008年   92318篇
  2007年   97453篇
  2006年   107514篇
  2005年   102740篇
  2004年   104402篇
  2003年   95325篇
  2002年   85482篇
  2001年   130333篇
  2000年   123868篇
  1999年   118516篇
  1998年   68170篇
  1997年   64928篇
  1996年   62913篇
  1995年   58238篇
  1994年   52557篇
  1993年   48748篇
  1992年   85525篇
  1991年   82695篇
  1990年   79745篇
  1989年   78766篇
  1988年   73461篇
  1987年   71310篇
  1986年   68008篇
  1985年   67277篇
  1984年   58112篇
  1983年   52524篇
  1982年   44866篇
  1981年   41958篇
  1980年   39569篇
  1979年   49841篇
  1978年   41608篇
  1977年   37659篇
  1976年   34862篇
  1975年   35025篇
  1974年   37337篇
  1973年   35825篇
  1972年   33673篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Multicentricity of hepatocellular carcinoma (HCC) is considered, especially in patients with liver cirrhosis. This paper describes an operative case of a male patient with probable multicentric development of HCC in precirrhotic fibrosis. The main tumors inside the capsule were completely necrotic due to transarterial embolization (TAE). Histologic examination disclosed discrete tiny nodules of HCC that were not detected grossly. They showed highly differentiated trabecular arrangements: Edmondson I. A scirrhous type was noted in the center of the tumors. At the borders of the tumors the carcinoma cells exhibited replacing growth patterns and it was thought that they developed multicentrically. Partial resection must be performed as extensively as possible in a case such as the present one.  相似文献   
992.
993.
Professional exposure to vegetable dusts affect the respiratory function of the exposed subjects. A previous survey conducted in an industrial flour-mill demonstrated a higher frequency of respiratory symptoms in workers compared to a control group. Ten subjects employed in a work site particularly exposed to dust were studied. Each subject answered a questionnaire and performed on Mondays and Fridays, at the begenning and end of his work shift, a flow volume curve and an isocapnic hyperventilation test. The aerobiology of the professional environment was also measured. We noted: 1) in the flow volume curves: a drop in the FEV1 during the Monday morning shift, a significant difference between the FEV1 (p<0.05) and the MMEFR 25–75 (p<0.05) measured at 6 am on Monday and Friday, and between the MMEFR 25–75 values obtained at 12 noon on Monday and Friday (p<0.05). 2) after isocapnic hyperventilation, a significant drop in the MMEFR 25–75 at 6 am on Monday (p<0.01) and in the FEV1 and MMEFR 25–75 at 12 noon on Mondays (p<0.05), a significant drop in the FEV1 at 1 pm on Monday (p<0.01).  相似文献   
994.
995.
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   
996.
997.
998.
999.
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   
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