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   1208篇
  免费   76篇
  国内免费   7篇
耳鼻咽喉   10篇
儿科学   72篇
妇产科学   11篇
基础医学   148篇
口腔科学   111篇
临床医学   74篇
内科学   189篇
皮肤病学   12篇
神经病学   68篇
特种医学   18篇
外科学   186篇
综合类   26篇
预防医学   68篇
眼科学   55篇
药学   153篇
中国医学   9篇
肿瘤学   81篇
  2023年   7篇
  2022年   13篇
  2021年   40篇
  2020年   20篇
  2019年   35篇
  2018年   38篇
  2017年   26篇
  2016年   39篇
  2015年   32篇
  2014年   62篇
  2013年   81篇
  2012年   99篇
  2011年   84篇
  2010年   52篇
  2009年   45篇
  2008年   59篇
  2007年   72篇
  2006年   51篇
  2005年   50篇
  2004年   59篇
  2003年   59篇
  2002年   37篇
  2001年   13篇
  2000年   13篇
  1999年   12篇
  1998年   14篇
  1996年   7篇
  1995年   5篇
  1994年   5篇
  1992年   7篇
  1991年   5篇
  1990年   9篇
  1989年   5篇
  1988年   7篇
  1987年   5篇
  1986年   6篇
  1985年   5篇
  1983年   4篇
  1982年   3篇
  1979年   3篇
  1977年   3篇
  1974年   5篇
  1973年   8篇
  1972年   19篇
  1971年   15篇
  1970年   7篇
  1969年   9篇
  1968年   11篇
  1967年   5篇
  1966年   10篇
排序方式: 共有1291条查询结果,搜索用时 31 毫秒
1.
Microbial co-infections are another primary concern in patients with coronavirus disease 2019 (COVID-19), yet it is an untouched area among researchers. Preliminary data and systematic reviews only show the type of pathogens responsible for that, but its pathophysiology is still unknown. Studies show that these microbial co-infections are hospital-acquired/nosocomial infections, and patients admitted to intensive care units with invasive mechanical ventilation are highly susceptible to it. Patients with COVID-19 had elevated inflammatory cytokines and a weakened cell-mediated immune response, with lower CD4+ T and CD8+ T cell counts, indicating vulnerability to various co-infections. Despite this, there are only a few studies that recommend the management of co-infections.  相似文献   
2.
3.
4.
Previous studies following single dose administration have suggested that the pharmacokinetics of various nifedipine formulations could be influenced by the timing of associated food consumption. In order more closely to reflect the clinical situation we have carried out a study at steady state using a 'biphasic' formulation comprising 'rapid' and 'retarded' drug release components. Fifteen normal subjects took 20 mg 'biphasic' nifedipine 12 hourly for 10 days. Studies were carried out on days 4, 7 and 10. On these days the nifedipine was taken 2 h or 1 h before or immediately following a light breakfast. A light breakfast influenced neither the rate nor the extent of nifedipine absorption nor the rate or extent of major metabolite appearance. We conclude that at steady state the timing of a light meal is unlikely to alter in any clinically important manner the pharmacokinetics of nifedipine released from 'biphasic' tablets.  相似文献   
5.
6.
Patient response to interactive videodisc preparation for third molar extraction surgery was examined as a function of self-reported information-seeking style. Amount learned was compared among patients informed via an interactive videodisc, noninteractive videotape of the same material, or surgeon only. Anxiety levels and satisfaction with preparation were compared between the videodisc and videotape groups. At consultation, patients (n = 35) were randomly assigned to either the disc- or the tape-viewing group. First, subjects completed a demographic survey, state anxiety scale, quiz on knowledge about third molars and surgery risks and complications, and information-seeking scales. Immediately after viewing the video, subjects completed another anxiety scale and a multiple-choice quiz covering the material presented. Subsequently, another 25 patients undergoing the routine (surgeon-only) consultation procedure were given the same multiple-choice quiz following consultation. Quiz scores differed significantly among the groups; mean percent correct for the tape-viewing subjects was 85; for disc-viewing subjects 72.6; for surgeon-only subjects, 40. Self-rated information seeking was unrelated to amount of video viewed by disc subjects (on average, 64% of the videodisc was viewed), and disc subjects who rated themselves higher in information-seeking achieved the lowest postpreparation quiz scores. Subjects in the disc group were significantly more satisfied with the amount of preparation than the tape group. Although disc group subjects were significantly less knowledgeable following consultation than were tape group subjects, interactive videodisc preparation for third molar extraction appears to have some advantages over more traditional approaches. Further research is needed to determine whether this approach to preparing patients is suitable for widespread clinical use.  相似文献   
7.
BACKGROUND: Linkage studies by us and others have confirmed that chromosome 1q23.3 is a susceptibility locus for schizophrenia. Based on this information, several research groups have published evidence that markers within both the RGS4 and CAPON genes, which are 700 kb apart, independently showed allelic association with schizophrenia. Tests of allelic association with both of these genes in our case control sample were negative. Therefore, we carried out further fine mapping between the RGS4 and CAPON genes. METHODS: Twenty-nine SNP and microsatellite markers in the 1q23.3 region were genotyped in the United Kingdom based sample of 450 cases and 450 supernormal control subjects. RESULTS: We detected positive allelic association after the eighth marker was genotyped and found that three microsatellite markers (p = .011, p = .014, p = .049) and two SNPs (p = .004, p = .043) localized in the 700 kb region between the RGS4 and CAPON genes, within the UHMK1 gene, were associated with schizophrenia. Tests of significance for marker rs10494370 remained significant following Bonferroni correction (alpha = .006) for multiple tests. Tests of haplotypic association were also significant for UHMK1 (p = .009) using empirical permutation tests, which make it unnecessary to further correct for both multiple alleles and multiple markers. CONCLUSIONS: These results provide preliminary evidence that the UHMK1 gene increases susceptibility to schizophrenia. Further confirmation in adequately powered samples is needed. UHMK1 is a serine threonine kinase nuclear protein and is highly expressed in regions of the brain implicated in schizophrenia.  相似文献   
8.
In acute quadriplegia we have noted that about one in five patients develops unexplained production of markedly excessive and tenacious bronchial mucus. Spontaneous recovery from mucus hypersecretion usually occurs within weeks to months. Mucus samples collected from 12 patients have been found to be abnormal. Macromolecular contents of single aspirates yielded as much as 500 mg. Analytical ultracentrifuge analysis showed the mucus to contain considerable epithelial glycoprotein (GP) of typical buoyant density; its amino acid and carbohydrate compositions were characteristic of the GP from hypersecretory bronchial mucus such as in chronic bronchitis and cystic fibrosis. In five patients studied after recovery from hypersecretion, there tended to be relatively less GP. The mucus samples contained a high density glycoconjugate (GC): this had sugars of GP but also reacted positively with a monoclonal antibody to keratan sulfate. Its amino acid composition was different from that of GP: threonine was lower and glycine was higher than in GP. In mucus from one patient who died, chondroitin sulfate ABC and hyaluronic acid were identified as well. This suggests proteoglycans are involved in the pathophysiology of mucus hypersecretion. The sudden onset and spontaneous recovery of hypersecretion suggests that it is not due to gland hypertrophy. We speculate that in acute quadriplegia it is due to disturbed neuronal control of bronchial mucus gland secretion, perhaps related to initial disappearance and later reappearance of peripheral sympathetic nervous system tone.  相似文献   
9.
Guar gum-based three-layer matrix tablets of a highly water-soluble drug, trimetazidine dihydrochloride, were evaluated for their in vivo release in healthy volunteers in comparison with commercially available conventional immediate release tablets. Six healthy volunteers participated in the study and a two-way crossover design was followed. The plasma concentration of trimetazidine dihydrochloride was estimated by reverse-phase HPLC. The pharmacokinetic parameters were calculated from the plasma concentration of trimetazidine dihydrochloride versus time data. The delayed T(max), decreased C(max) and K(a), unaltered bioavailability, and prolonged t(1/2) and MRT indicated a slow and prolonged release of trimetazidine dihydrochloride from guar gum three-layer matrix tablets in comparison with the immediate release tablet dosage form. The guar gum three-layer matrix tablets of trimetazidine dihydrochloride may be useful in providing constant drug delivery with minimum fluctuations.  相似文献   
10.
We have characterized homologous DNA recombination activity in nuclear protein extracts prepared from quiescent and regenerating rat livers. Activity measured in regenerating liver extracts was elevated approximately 35-fold above control, and its appearance closely mirrored the first wave of DNA synthesis, peaking 24 hours after a regenerative stimulus, and returning fairly rapidly to basal levels. We also identified a strand-transferase protein of approximately 100 kDa whose presence in these extracts correlates with homologous recombination activity. Recent evidence suggests that mammalian somatic cells possess a recombinational DNA repair mechanism analogous to that described in the yeastSaccharomyces cerevisiae. Our results indicate that this recombinational repair process may be regulated in vivo by, or play a role in, progression through the cell division cycle.  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