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   1283400篇
  免费   98610篇
  国内免费   2002篇
耳鼻咽喉   18478篇
儿科学   44540篇
妇产科学   35114篇
基础医学   182781篇
口腔科学   33674篇
临床医学   111911篇
内科学   259295篇
皮肤病学   28060篇
神经病学   100768篇
特种医学   51325篇
外国民族医学   660篇
外科学   197204篇
综合类   27141篇
现状与发展   1篇
一般理论   379篇
预防医学   96244篇
眼科学   28030篇
药学   95083篇
  2篇
中国医学   2437篇
肿瘤学   70885篇
  2018年   13234篇
  2017年   10042篇
  2016年   10982篇
  2015年   12462篇
  2014年   17284篇
  2013年   26406篇
  2012年   36363篇
  2011年   38381篇
  2010年   22963篇
  2009年   21953篇
  2008年   36885篇
  2007年   39557篇
  2006年   39811篇
  2005年   38769篇
  2004年   37923篇
  2003年   36729篇
  2002年   36026篇
  2001年   64076篇
  2000年   66582篇
  1999年   56507篇
  1998年   15187篇
  1997年   13808篇
  1996年   14231篇
  1995年   13482篇
  1994年   12797篇
  1993年   11830篇
  1992年   44599篇
  1991年   43527篇
  1990年   42269篇
  1989年   40161篇
  1988年   36942篇
  1987年   36282篇
  1986年   33655篇
  1985年   32319篇
  1984年   24171篇
  1983年   20303篇
  1982年   11741篇
  1981年   10721篇
  1980年   9543篇
  1979年   21368篇
  1978年   14846篇
  1977年   12550篇
  1976年   11726篇
  1975年   12652篇
  1974年   14685篇
  1973年   14146篇
  1972年   12968篇
  1971年   11751篇
  1970年   11066篇
  1969年   10043篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
A total of 186 blood samples from 24 HIV-1 seropositive hemophiliac patients, monitored every four months for 29 months, were investigated for the presence of viral antigen in plasma. In addition, peripheral blood mononuclear cells (PBMC) were cultured for HIV-1, using normal PBMC as a target for replication. Antigenemia was detected in 51 % of the patients and from PBMC in 87.5 % of the patients. The incidence of HIV isolation in asymptomatic patients (42.8 %) was similar to that found in symptomatic patients (51.4 %). Patients with opportunistic infections had a higher incidence of lymphocytic viremia (p<0.05). Plasma viremia was closely associated (p<0.05) with low CD4+ counts and infection progression. The persistence of antigenemia was also a marker of a poor clinical course. In treated patients, plasma viremia was the marker that better correlated with the clinical course, and it did not appear during the first nine months of therapy. Zidovudine doses of >500 mg/day significantly lowered the appearance of antigenemia and lymphocytic viremia (p<0.05).  相似文献   
994.
995.
When administered systemically, glucose attenuates deficits in memory produced by several classes of drugs, including cholinergic antagonists and opiate agonists. Glucose also enhances memory in aged rats, mice, and humans. In addition, glucose ameliorates age-related reductions in paradoxical sleep. Because deficits in paradoxical sleep are most marked in those individual aged rats that also have deficits in memory, treatments which improve one of these functions may similarly improve the other. The present experiments show that glucose attenuates deficits in paradoxical sleep and memory after atropine administration, with similar dose-response curves for both actions. In the first experiment, rats received saline, atropine (1 mg/kg), glucose (100 mg/kg) or combinations of atropine + glucose (10, 100, 250, and 500 mg/kg) 30 min before assessment on a spontaneous alternation task. In the second experiment, 3-h EEGs were assessed for spontaneous daytime sleep in rats administered saline, atropine (1 mg/kg), glucose (100 mg/kg) or combinations of atropine + glucose (10, 100 and 250 mg/kg). In both experiments, glucose significantly attenuated deficits at an optimal dose of 100 mg/kg. A third experiment assessed blood glucose levels after injections of atropine + glucose (100 mg/kg) and determined that blood glucose levels were similar to those produced by other treatments which enhance memory. These results are consistent with the view that paradoxical sleep and at least one test of memory are similarly influenced by atropine and glucose.  相似文献   
996.
We report the clinical, SPET, immunohistochemical and DNA features of an early-onset familial Alzheimer's disease (FAD) in an Argentine pedigree of South American indian ethnic background. Pedigree spans 5 generations comprising more than 110 biological relatives. Clinical data supported the diagnosis of early onset FAD (mean age at onset 38.9 years) in 10 family members, including 3 with pathological confirmation (mean age at death 48.5). The pattern of transmission suggested autosomal dominant inheritance. Prominent features were mood changes, early language impairment, myoclonus, seizures and cerebellar signs. SPET displayed bilateral frontal, temporo-parietal and cerebellar hypoperfusion in early stages and in an asymptomatic member at risk, suggesting that SPET may have predictive value in this family. Immunohistochemistry showed β amyloid deposits within neuritic plaques and vessel walls and no anti-PrP immunoreactivity. DNA analysis showed no abnormalities in the β amyloid precursor protein gene. The identification of additional genetic defects in well characterized independent FAD pedigrees will contribute to the understanding of the pathogenesis of Alzheimer's disease.  相似文献   
997.
A 30-year-old presented In 1984 with a clinically nonfunctional tumour which subsequently developed Into a metastatic corticotrophlnoma from which he died despite surgery In 1984,1986 and 1991 and external radiotherapy In 1986. Molecular genetic analysis of tumour and metastatic tissue revealed loss of heterozygosity at loci on the autosomes 1p, 3p, 10q26,11q13 and 22q12. Tissue taken at surgery In 1986 also revealed positive cytoplasmic Immunostalning for p53 protein. No such staining was evident in tissue taken at first surgery in 1984. Further analysis of Invasive pituitary adenomas may reveal loci associated with such behaviour, enabling better prediction of subsequent clinical outcome than is possible using standard histological techniques, and delivery of early, aggressive treatment to those tumours which show molecular markers associated with a poor prognosis.  相似文献   
998.
999.
1000.
Summary Rats were treated with desipramine 5mg/kg, nomifensine 10mg/kg, zimelidine 25 mg/kg or with 0.9% sodium chloride once a day during the second and third weeks after birth, and brain stem, caudate/putamen and cortical monoamines, and caudate/putamen dopamine D1 (3[H]SCH 23390) and D2 (3[H]spiroperidol) receptor binding were measured when rats were at two months of age. In the brain stem, the concentration of 3-methoxy-4-hydroxy-phenyl glycol was increased in nomifensine rats and the ratio of 5-hydroxyindoleacetic acid to 5-hydroxytryptamine was increased in zimelidine rats. In the caudate/putamen, the concentrations of 3,4-dihydroxyphenylacetic acid and homovanillic acid and the ratio of homovanillic acid to dopamine were increased in desipramine rats; neither3[H]SCH 23390 nor3[H]spiroperidol binding were affected by any of the three monoamine uptake inhibiting antidepressants studied. In the cortex, the ratio of 5-hydroxyindoleacetic acid to 5-hydroxytryptamine was increased in desipramine and zimelidine rats. The findings suggest that desipramine but not nomifensine increases the metabolism of dopamine in the caudate/ putamen and nomifensine but not desipramine increases the metabolism of norepinephrine in the brain stem, and furthermore that the metabolism of serotonin is affected by desipramine as well as by zimelidine. It is possible that also treatment of women with these drugs during late pregnancy causes long-lasting changes in the brain of human fetus.  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