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   1265832篇
  免费   94996篇
  国内免费   1585篇
耳鼻咽喉   16330篇
儿科学   41092篇
妇产科学   35032篇
基础医学   189760篇
口腔科学   34772篇
临床医学   117953篇
内科学   248229篇
皮肤病学   27384篇
神经病学   101993篇
特种医学   46792篇
外国民族医学   267篇
外科学   178871篇
综合类   25762篇
现状与发展   3篇
一般理论   568篇
预防医学   104790篇
眼科学   28091篇
药学   92654篇
  7篇
中国医学   2023篇
肿瘤学   70040篇
  2018年   13564篇
  2017年   10419篇
  2016年   11350篇
  2015年   13111篇
  2014年   18056篇
  2013年   27569篇
  2012年   37669篇
  2011年   40087篇
  2010年   23131篇
  2009年   22306篇
  2008年   37853篇
  2007年   40484篇
  2006年   40053篇
  2005年   39191篇
  2004年   37641篇
  2003年   36072篇
  2002年   34960篇
  2001年   56086篇
  2000年   57102篇
  1999年   48150篇
  1998年   13410篇
  1997年   12240篇
  1996年   12661篇
  1995年   11931篇
  1994年   11114篇
  1993年   10414篇
  1992年   38242篇
  1991年   37710篇
  1990年   36472篇
  1989年   35293篇
  1988年   32727篇
  1987年   32063篇
  1986年   30557篇
  1985年   28811篇
  1984年   21958篇
  1983年   19209篇
  1982年   11382篇
  1981年   10342篇
  1979年   20963篇
  1978年   15401篇
  1977年   12797篇
  1976年   11861篇
  1975年   12821篇
  1974年   15599篇
  1973年   15374篇
  1972年   14523篇
  1971年   13567篇
  1970年   12792篇
  1969年   12071篇
  1968年   11235篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The importance of portal insulin delivery in the regulation of postprandial carbohydrate metabolism is uncertain. To address this question, three groups of dogs were studied: one group in which pancreatic venous drainage was transected and reanastomosed (portal insulin delivery), one in which the pancreatic drainage was transected and anastomosed to the inferior vena cava (peripheral insulin delivery), and one that received only a sham operation. Plasma insulin was greater (P less than 0.05) during peripheral insulin delivery than in either the portal or sham groups, respectively, before and after meal ingestion. On the other hand, C-peptide concentrations did not differ between groups, resulting in a higher (P less than 0.001) insulin to C-peptide ratio in the peripheral group. This indicated that the hyperinsulinemia in the peripheral group was due to decreased insulin clearance rather than increased insulin secretion. Isotopically determined splanchnic uptake of ingested glucose, postprandial suppression of hepatic glucose release, incorporation of CO2 into glucose (a qualitative measure of gluconeogenesis), and total-body glucose uptake were virtually identical in all groups. Similarly, plasma lipid, beta-hydroxybutyrate, and lactate concentrations did not differ between groups. Our data indicate that, despite differences in systemic insulin concentration, portal and peripheral insulin delivery comparably regulate hepatic and extrahepatic carbohydrate metabolism after meal ingestion.  相似文献   
992.
The limited contact dynamic compression plate (LC-DCP)   总被引:5,自引:0,他引:5  
Summary To realize the new concept of biological internal fixation the limited contact dynamic compression plate was developed. It minimizes vascular damage to the plated bone segment. It should lead to a more versatile and efficient application of internal fixation using plates.  相似文献   
993.
Desferrioxamine (DFO) metabolism and its pharmacokinetics were studied in a swine model using high-performance liquid chromatography. DFO and three iron-binding metabolites occurred in plasma. Interindividual differences in pharmacokinetics and metabolism were observed. Urine analysis in 4 pigs showed three iron-binding metabolites. The mean percent dose excreted in urine in the form of the parent drug was 45 +/- 10% and 10 +/- 2% (means +/- SD) in the form of metabolites. Of the total amount of the parent drug infused, 3 h after initiation, 87% was in the form of DFO, whereas 13% was present as the DFO-iron III complex which represented 45 mg of urinary iron elimination. The described DFO infusion protocol provides for sufficient DFO to chelate significant amounts of ferric iron in excess of normal levels, thus allowing experimental studies of iron chelation in a variety of disease states.  相似文献   
994.
Between January and June 1988, a survey of 7516 people in aged care facilities in the Auckland region (99.4% response rate) was undertaken to ascertain the extent and provision of care for elderly people requiring ongoing care in order to make comparisons with other centres in New Zealand. Information was gathered about their ability to perform various activities of daily living by staff members who completed a structured precoded and pretested questionnaire for each resident or patient. Overall levels of dependency were also assessed as part of the questionnaire: 13% were assessed as requiring long stay hospital care, 48% had moderate or appreciable dependency, and the remainder had some dependency (23%) or none at all (16%). Almost one quarter (23%) of the 5213 residents in old people's homes were rated as apparently independent. Of people in religious and welfare residential homes, 38% were rated as independent whereas in commercial rest homes 12% of people were classified in this way. This high level of apparent independence in religious and welfare homes is the main aspect in which the Auckland long term care scene is distinct from other regions in the country.  相似文献   
995.
Epitope libraries provide a method to identify peptide ligands for antibodies, receptors or other binding proteins. As such, they provide a powerful tool to rapidly identify lead ligands in the drug discovery process. In an attempt to correlate structural information with the results from peptide screening, we have used NMR spectroscopy of peptide/antibody complexes to demonstrate that core residues identified through a two-stage selection process undergo a larger structural change upon binding antibody than do positions in the peptide amenable to a variety of side chains. The model system used was the M2 monoclonal antibody/Flag? octapeptide epitope system. We have analyzed two peptides: Ac-Asp-Tyr-Lys-Leu-Gly-Asp-Asp-Leu-NH2 (peptide l), which contains several non-core positions randomized, and Ac-Asp-Tyr-Lys-Asp-Asp-Asp-Asp-Leu-NH2 (peptide 2), which closely corresponds to the original Flag? sequence. Enrichment of the peptides with 15N facilitated the investigation by permitting spectral editing of the peptide resonances in the presence of antibody. For peptide 1 the absolute shifts for the free vs. Fab-bound peptide were found to be largest for the amide groups of Asp-1 and Asp-6, in agreement with classification of these residues as critical by the phage display library selection process. For peptide 2 the largest absolute shifts were observed for Asp-1 and Asp-4, with the other aspartic acid residues also showing significant but smaller changes. © Munksgaard 1995.  相似文献   
996.
Background : Malnutrition is very frequent in childhood cancer. Its main cause is inadequate intake for energy demands owing to lack of appetite. Megestrol acetate is a synthetic progestin that has been used for reversing anorexia in adult cancer.
Objectives : To assess megestrol acetate efficacy and side-effects in treating anorexia in childhood cancer.
Methods : Thirty-five children with solid tumours were receiving antitumour therapy. Nutritional assessment was by anthropometry. Megestrol acetate efficacy was assessed by evaluating grade of appetite, energy intake and well-being. Side-effects were evaluated by means of clinical history, physical examination, lipid profile, coagulation tests and cortisol rhythm.
Results : When compared to baseline all the anthropometric measurements increased ( P <0.05) from the first month of megestrol acetate therapy, as well as appetite and energy intake. No significant side-effects were found.
Conclusion : Megestrol acetate therapy is a powerful appetite stimulant which led to weight gain, composed of both fat mass and fat-free mass. Megestrol acetate is well tolerated, with few and mild side-effects. If megestrol acetate therapy is started at the onset of anorexia, the use of more expensive, invasive and complicated techniques of nutritional support may be avoided.  相似文献   
997.
Extracellular single-unit recordings were made in somatosensory cortical barrels of fentanyl-sedated rats. Whiskers were deflected singly or in paired combinations. lontophoretically-applied (−)-baclofen disproportionately reduced weak responses, and phaclofen disproportionately increased them, resulting in more tightly focused or more broadly focused receptive fields, respectively. Both drugs had only minor effects on surround inhibition. In light of previous findings, we conclude that GABAA and GABAB mechanisms both act to enhance spatial contrast, but that the former plays a much greater role in enhancing temporal resolution.  相似文献   
998.
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