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   1382篇
  免费   91篇
  国内免费   19篇
耳鼻咽喉   30篇
儿科学   23篇
妇产科学   67篇
基础医学   176篇
口腔科学   47篇
临床医学   168篇
内科学   355篇
皮肤病学   46篇
神经病学   100篇
特种医学   30篇
外科学   140篇
综合类   3篇
预防医学   63篇
眼科学   27篇
药学   94篇
肿瘤学   123篇
  2023年   14篇
  2022年   30篇
  2021年   53篇
  2020年   35篇
  2019年   43篇
  2018年   52篇
  2017年   49篇
  2016年   40篇
  2015年   43篇
  2014年   74篇
  2013年   78篇
  2012年   99篇
  2011年   93篇
  2010年   45篇
  2009年   46篇
  2008年   88篇
  2007年   79篇
  2006年   72篇
  2005年   64篇
  2004年   61篇
  2003年   62篇
  2002年   49篇
  2001年   18篇
  2000年   21篇
  1999年   27篇
  1998年   16篇
  1997年   11篇
  1996年   19篇
  1995年   7篇
  1994年   5篇
  1993年   7篇
  1992年   14篇
  1991年   8篇
  1990年   11篇
  1989年   4篇
  1988年   8篇
  1987年   6篇
  1986年   5篇
  1985年   9篇
  1984年   3篇
  1983年   3篇
  1981年   3篇
  1976年   1篇
  1975年   3篇
  1972年   4篇
  1971年   2篇
  1970年   2篇
  1969年   2篇
  1968年   1篇
  1966年   1篇
排序方式: 共有1492条查询结果,搜索用时 156 毫秒
11.
Gaucher disease, the deficiency of the lysosomal enzyme glucocerebrosidase (EC 3.2.1.45), is frequently encountered in the Ashkenazi Jewish population. Carrier screening for Gaucher disease by enzyme analysis performed during a routine pregnancy indicated that both Ashkenazi parents were carriers. Screening for four common Gaucher mutations was subsequently performed on fetal and parental DNA. None of the common Ashkenazi mutations were identified. However, when exons 9–11 were amplified and digested withNciI to detect the L444P mutation, it appeared that the mother and the fetus had an unusual allele and that the expected paternal allele was not present. When the fetal amniocytes were found to have less than 2% of the normal glucocerebrosidase activity and a fetal sonogram revealed hydrops fetalis, the pregnancy was terminated. The diagnosis of severe type 2 Gaucher disease was confirmed at autopsy. Ultrastructural studies of epidermis from the fetus revealed the characteristic disruption of lamellar bilayers, diagnostic for type 2 Gaucher disease. In subsequent studies of the fetal DNA, long-template polymerase chain reaction amplification revealed one appropriately sized band (6.5 kb) and one smaller (5.2 kb) band. Sequencing of the 5.2-kb fragment identified a novel fusion allele resulting from recombination between the glucocerebrosidase gene and its pseudogene beginning in intron 3. This fusion allele was inherited from the father. The result was confirmed by Southern blot analysis using the enzymeSstII. Sequencing of the 6.5-kb fragment identified a previously described, although rare, T-to-G splice junction mutation in intron 10 of the maternal allele, which introduced anNciI site. The couple had a subsequent pregnancy which was also found to be affected. This case study identifies a novel recombinant allele and an unusual splice junction mutation, and demonstrates that even in the Ashkenazi population, screening for common mutations may not accurately identify the most severe forms of the disease.  相似文献   
12.
13.
Tissue inhibitor of metalloproteinases 1 (TIMP-1) inhibits several proteinases including a disintegrin and metalloproteinase 10 (ADAM10), a major alpha-secretase that cleaves the beta-amyloid precursor protein within its amyloidogenic Abeta domain. The gene encoding TIMP-1 (TIMP 1) maps to the short arm of the X chromosome, in a region previously suggested as conferring genetic susceptibility for Alzheimer's disease (AD). To determine whether genetic variability of TIMP 1 contributes to the pathogenesis of AD, we analysed one single nucleotide polymorphism within TIMP 1 and one single nucleotide polymorphism in the 5'-untranslated region of TIMP 1 in patients with AD and control subjects from two independent and ethnically different populations. We did not observe any association between TIMP 1 genotypes and the diagnosis of AD in men or women. We also measured TIMP-1 protein levels in the cerebrospinal fluid of patients with AD, healthy control subjects, and patients with other neurological disorders. TIMP-1 levels were similar in all groups. In addition, no significant differences were observed after stratification for TIMP 1 genotypes. Our data show that neither genetic variability nor protein levels of TIMP-1 are associated with AD.  相似文献   
14.
Microsatellite instability and p53 expression in gallbladder carcinomas.   总被引:1,自引:0,他引:1  
We studied the MSI (microsatellite instability) status and p53 expression in a series of 71 gallbladder cancers (GCs) of different histologic type. All neoplasms were examined combining a microsatellite analysis at mononucleotide locus BAT-26 and an immunohistochemical study for hMSH2, hMLH1, and p53 proteins and markers of gastric and intestinal differentiation. All the 71 GCs were MSS (microsatellite stable). The p53 protein was found in 100% of undifferentiated GCs, 67% of conventional gallbladder adenocarcinomas, 50% of mucinous adenocarcinomas, and 20% GCs with squamous differentiation. All 71 MSS tumors showed presence of immunohistochemical expression of both hMLH1 and hMSH2 gene products. We concluded that microsatellite instability does not play a role in the developing of GC while p53 seems to be the most important alteration found in a large proportion of these cancers, with the only exception of mucinous and squamous gallbladder carcinomas.  相似文献   
15.
A fatal pneumonia due to Legionella pneumophila was diagnosed in a young calf reared in a dairy herd located in northern Italy. Clinical symptoms consisted of watery diarrhea, hyperthermia, anorexia, and severe dyspnea. The pathological and histological findings were very similar to those observed in human legionellosis. Legionella pneumophila serogroup 1 (SG1) and SG10 were isolated from the calf’s lung, and L. pneumophila SG1 was isolated from the calf’s liver. L. pneumophila SG1 was also demonstrated in the lung tissue by immunofluorescence and immunohistochemical examinations. Nine of 10 L. pneumophila SG1 isolates belonged to the Olda subtype, and 1 belonged to the Camperdown subtype. A very low prevalence of antibodies to Legionella was detected in cows and calves reared in the same herd. Cultures of aqueous sediment of an old electric water heater which supplied hot water for the feeding of the calves yielded L. pneumophila SG1. Four of the colonies tested belonged to the Olda subtype. Ten clinical and four environmental isolates were examined for the presence of plasmids. Nine of them were also examined by pulsed-field gel electrophoresis assay, and the same patterns were found for L. pneumophila SG1 Olda strains isolated from the calf and from the electric heater. This is the first report of a documented case of a naturally occurring Legionella pneumonia in an animal. Cattle probably act as accidental hosts for legionellae, much the same as humans.  相似文献   
16.
The aim of this study was to locate in male pigs the sensory and autonomic ganglia innervating the retractor penis muscle (RPM), which was taken as an experimental model of the genital smooth musculature. The retrograde neuronal tracers horseradish peroxidase (HRP), Fast Blue (FB), and diamidino yellow (DY) were injected into the bulbopenile portion of the left RPM. The tracers highlighted a different affinity for the neuronal structures, although labelled cells supplying the RPM were generally found in bilateral dorsal root ganglia (DRGs, S1-S3), in bilateral paravertebral ganglia (PaGs, L2-S3), and in the left and right caudal mesenteric ganglia (CMGs). The mean number of labelled FB cells was 795 (range, 645-952) in DRGs, 16046.25 (range, 10226-18742) in PaGs, and 635.25 (range, 333-786) in CMGs. The mean diameter of pseudounipolar DRG cells was 60-75 microm, while the multipolar neurons of PaGs and CMGs had dimensions varying between 20-50 microm and 20-30 microm, respectively.  相似文献   
17.
Objectives To evaluate uterine artery resistance during multiovulation induction in relation to the implantation rate in patients attendingin vitro fertilization (IVF) cycles.Patients Multiovulation induction for IVF was monitored by daily determination of the pulsatility index (PI) of the uterine arteries, obtained by a transvaginal probe (6.5 MHz) implemented with color-flow imaging. Doppler data were obtained from 5 days before hCG administration to the day of follicular aspiration. One IVF cycle was monitored in 70 patients. In 17 patients, 41 IVF cycles were monitored until a successful attempt occurred.Results In the 70 patients studied during one IVF attempt, the PI of the uterine arteries significantly varied (P < 0.001) in the different phases of the cycle. In the 24 patients who conceived, a significantly lower PI (P < 0.03) was found throughout the cycle. This result was mainly due to a highly significant difference of PI values observed the day after hCG administration (P < 0.005). In the 17 patients who conceived after 1 to 4 negativein vitro fertilizations, no significant difference in PI was observed in the uterine artery resistance in cycles in which implantation was or was not successful.Conclusions Uterine artery resistance varies significantly during phases of the induction therapy. Uterine artery resistance is lower throughout the course of multiovulation induction in patients with higher pregnancy rates. The PI on the day after hCG administration was the best index of pregnancy rate. Low uterine artery resistance was present even in negative attempts in patients who eventually achieved a successful implantation. PI values 3 can be considered a favorable prognostic factor for future IVF cycles.Presented at the 49th Annual Meeting of the American Fertility Society, Montreal, 1993 and the 50th Annual Meeting of the American Fertility Society, November 5–10, 1994, San Antonio, Texas.  相似文献   
18.
19.
BACKGROUND: In an attempt to find new parameters able to evaluate the actual iron availability by bone marrow cells, zinc protoporphyrin (ZnPP), a metabolic intermediate generated in the red blood cell by the incorporation of zinc instead of iron, has been proposed. ZnPP is a good marker of iron-deficiency anemia in non-uremic people, as red blood cell ZnPP concentration rises specifically (except for lead intoxication) in this condition. Existing data on ZnPP as a marker of iron deficiency in uremic patients comes mainly from cross sectional studies on chronic hemodialysis and has produced conflicting results. SUBJECTS AND METHODS: Therefore, we prospectively studied 42 HID patients, 28-88 years old, 13-346 months of dialysis age, beginning from a period of maximal iron deficiency, due to the lack of parenteral iron compounds (T0) up to the end of more than one year of follow-up with continuous parenteral iron supplementation (T4). ZnPP, hemoglobin, transferrin saturation and ferritin were serially determined before and after six weeks (T1), four months (T2), seven months (T3) and 14 months (T4) of parenteral iron supplementation at a maintenance dose of 0.5-1 mg/kg/week. RESULTS: In comparison with baseline values (95+/-37 micromol/mol heme) there were no significant changes in ZnPP levels at T1 and T2 despite a continuous increase in both transferrin saturation and ferritin values, while ZnPP significantly decreased at T4 (63+/-37 micromol/mol heme, p<0.001). There was no correlation between ZnPP and both transferrin saturation and ferritin at any time during the study, the same was true for ZnPP and zinc and lead serum concentration, fibrinogen and reactive C protein levels at T1 and T4, respectively. At T4, only 2/10 patients who still showed ZnPP levels >80 micromol/mol heme had absolute or functional iron deficiency, when the percentage of hypochromic red cells were measured. CONCLUSION: We conclude that ZnPP untimely parallels a change in iron balance in only a proportion of uremic people, in as much as confounding factors, such as chronic inflammation and uremia in itself may obscure its relationship with iron status. Therefore, ZnPP cannot be assumed to be a first-line diagnostic marker of iron balance in uremic patients.  相似文献   
20.
Question I often prescribe domperidone to women as a galactagogue starting at a dose of 30 mg and increasing the dose as needed. In March of this year, Health Canada released an advisory warning of domperidone use and abnormal heart rhythms and sudden cardiac death. Should I cap doses at 30 mg or stop prescribing domperidone all together to these women?Answer The Health Canada warning is based on 2 studies. The results of the studies are not directly applicable to breastfeeding and should not change the way you normally manage otherwise healthy breastfeeding women.  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