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   2394篇
  免费   227篇
  国内免费   24篇
耳鼻咽喉   7篇
儿科学   95篇
妇产科学   32篇
基础医学   268篇
口腔科学   71篇
临床医学   204篇
内科学   433篇
皮肤病学   312篇
神经病学   105篇
特种医学   293篇
外科学   285篇
综合类   40篇
预防医学   149篇
眼科学   119篇
药学   87篇
  1篇
中国医学   8篇
肿瘤学   136篇
  2023年   15篇
  2022年   20篇
  2021年   58篇
  2020年   59篇
  2019年   56篇
  2018年   64篇
  2017年   55篇
  2016年   80篇
  2015年   61篇
  2014年   71篇
  2013年   110篇
  2012年   99篇
  2011年   123篇
  2010年   101篇
  2009年   91篇
  2008年   81篇
  2007年   94篇
  2006年   82篇
  2005年   70篇
  2004年   71篇
  2003年   82篇
  2002年   68篇
  2001年   60篇
  2000年   42篇
  1999年   45篇
  1998年   93篇
  1997年   83篇
  1996年   64篇
  1995年   63篇
  1994年   46篇
  1993年   48篇
  1992年   16篇
  1991年   31篇
  1990年   20篇
  1989年   49篇
  1988年   42篇
  1987年   35篇
  1986年   27篇
  1985年   28篇
  1984年   18篇
  1983年   18篇
  1982年   15篇
  1981年   18篇
  1980年   23篇
  1979年   12篇
  1978年   23篇
  1977年   17篇
  1976年   12篇
  1975年   10篇
  1971年   12篇
排序方式: 共有2645条查询结果,搜索用时 296 毫秒
51.
BACKGROUND: Dietary carbohydrates vary in their ability to raise blood glucose and insulin levels, which, in turn, influence levels of sex hormones and insulin-like growth factors. We analyzed the effect of type and amount of carbohydrates on ovarian cancer risk, using the glycemic index (GI) and the glycemic load (GL) measurement in a large case-control study conducted in Italy. MATERIALS AND METHODS: Cases included 1031 women with incident, histologically confirmed epithelial ovarian cancer, from four Italian regions. Controls included 2411 women admitted to the same hospital networks for acute, non-neoplastic conditions. Average daily GI and GL were calculated from a validated food frequency questionnaire. Odds ratios (OR) and the corresponding 95% confidence intervals (CI) were computed using multiple logistic regression. RESULTS: Ovarian cancer was directly associated with dietary GI (OR for highest versus lowest quartile = 1.7, 95% CI 1.3-2.1) and GL (OR = 1.7, 95% CI 1.3-2.1). The associations were observed in pre- and postmenopausal women, and they remained consistent across strata of major covariates identified. CONCLUSIONS: This study supports the hypothesis of a direct association between GI and GL and ovarian cancer risk and, consequently, of a possible role of hyperinsulinemia/insulin resistance in ovarian cancer development.  相似文献   
52.
53.
Objectives: To describe the physical growth patterns of infants born to narcotic dependent mothers (INDM) over a 12 months period and, if possible, to relate the growth to drug taking patterns during pregnancy.
Methodology: The growth of a cohort of 43 INDM was measured during the first 12 months of life. Weight and length measurements were compared with percentile charts and converted to Z scores. Questionnaire data about drug taking practices, demographic variables and the neonatal period (including withdrawal scores) were obtained.
Results: Twenty-four (55.8%) of INDM had evidence of neonatal drug withdrawal requiring treatment with phenobarbitone. At birth, Z scores for weight and length indicated relative intrauterine growth retardation. By 12 months, there had been some catch up growth, but Z scores for weight and length were still below zero. Persistent weight retardation at 12 months was correlated with methadone dosage during pregnancy, but not the need for phenobarbitone therapy.
Conclusions: The growth patterns of INDM in the first 12 months of life indicated that at birth there was evidence of intrauterine growth retardation, but by 12 months the growth was little different from the rest of the community. There appears to be some influence of narcotic agents taken while pregnant on subsequent growth of INDM.  相似文献   
54.
55.
Aflatoxin B1 (AFB1), a mutagen and hepatocarcinogen in rats and humans, is a contaminant of the human food supply, particularly in parts of Africa and Asia. AFB1-induced changes in gene expression may play a part in the development of the toxic, immunosuppressive and carcinogenic properties of this fungal metabolite. An understanding of the-role of AFB1 in modulating gene regulation should provide insight regarding mechanisms of AFB1-induced carcinogenesis. We used three PCR- based subtractive techniques to identify AFB1-responsive genes in cultured primary rat hepatocyte RNA: differential display PCR (DD-PCR), representational difference analysis (RDA) and suppression subtractive hybridization (SSH). Each of the three techniques identified AFB1- responsive genes, although no individual cDNA was isolated by more than one technique. Nine cDNAs isolated using DD-PCR, RDA or SSH were found to represent eight genes that are differentially expressed as a result of AFB1 exposure. Genes whose mRNA levels were increased in cultured primary rat hepatocytes after AFB1 treatment were corticosteroid binding globulin (CBG), cytochrome P450 4F1 (CYP4F1), alpha-2 microglobulin, C4b-binding protein (C4BP), serum amyloid A-2 and glutathione S-transferase Yb2 (GST). Transferrin and a small CYP3A-like cDNA had reduced mRNA levels after AFB1 exposure. Full-length CYP3A mRNA levels were increased. When liver RNA from AFB1-treated male F344 rats was evaluated for transferrin, CBG, GST, CYP3A and CYP4F1 expression, a decrease in transferrin mRNA and an increase in CBG, GST, CYP3A and CYP4F1 mRNA levels was also seen. Analysis of the potential function of these genes in maintaining cellular homeostasis suggests that their differential expression could contribute to the toxicity associated with AFB1 exposure.   相似文献   
56.
57.
58.
Neuroglobin (NGB) is considered as an endogenous neuroprotective molecule against stroke, since the protein alleviates the adverse effects of hypoxic and ischemic insults. We previously demonstrated the functional link between NGB and mitochondria since it is required for respiratory chain function. Thus, here, we evaluated the relevance of this effect in the Harlequin (Hq) mouse strain, which exhibits retinal ganglion cell (RGC) loss and optic atrophy due to a respiratory chain complex I (CI) defect. A twofold decrease of NGB amounts was observed in Hq retinas. We constructed a recombinant adeno-associated virus which combines to the mouse NGB open reading frame, its 5′ and 3′UTR, for guarantying mRNA stability and translation capacity. The vector was administrated intravitreally to Hq mice and NGB expression was stable for up to 7 months without negative effect on retinal architecture or function. On the contrary, RGCs and their axons were substantially preserved from degeneration; consequently, CI activity in optic nerves was protected conferring improvements in vision. Hence, we established that NGB prevents respiratory chain impairment, therefore, protecting visual function otherwise compromised by mitochondrial energetic failure.  相似文献   
59.
One morning in November a physician and his partner showed anticholinergic symptoms of varying intensity shortly after enjoying a cup of coffee at breakfast time. The coffee had been prepared in the fully automatic coffee machine of the physician. In the toxicological investigations atropine and scopolamine could be detected in the sample of water from the reservoir tank and in the urine of the victims. It was suspected that the ex-partner of the male victim had wanted to poison them with extracts of Angel’s Trumpet. Within the framework of the police investigations experiments were carried out to examine how much atropine and scopolamine could be extracted from the flowers of Angel’s Trumpet and the concentration of these substances in coffee after the brewing procedure of the fully automatic coffee machine. The investigations showed that the brewing procedure led to a reduction of the concentrations but not to a complete loss of the poisonous substances.  相似文献   
60.
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