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   21233篇
  免费   1375篇
  国内免费   97篇
耳鼻咽喉   223篇
儿科学   556篇
妇产科学   434篇
基础医学   3329篇
口腔科学   532篇
临床医学   2077篇
内科学   4650篇
皮肤病学   531篇
神经病学   2485篇
特种医学   627篇
外科学   1805篇
综合类   109篇
一般理论   13篇
预防医学   1840篇
眼科学   417篇
药学   1336篇
中国医学   78篇
肿瘤学   1663篇
  2024年   36篇
  2023年   207篇
  2022年   410篇
  2021年   693篇
  2020年   465篇
  2019年   655篇
  2018年   697篇
  2017年   532篇
  2016年   631篇
  2015年   742篇
  2014年   881篇
  2013年   1097篇
  2012年   1768篇
  2011年   1884篇
  2010年   1001篇
  2009年   906篇
  2008年   1477篇
  2007年   1477篇
  2006年   1391篇
  2005年   1304篇
  2004年   1206篇
  2003年   1085篇
  2002年   926篇
  2001年   114篇
  2000年   74篇
  1999年   119篇
  1998年   180篇
  1997年   154篇
  1996年   111篇
  1995年   87篇
  1994年   68篇
  1993年   48篇
  1992年   31篇
  1991年   22篇
  1990年   34篇
  1989年   21篇
  1988年   15篇
  1987年   18篇
  1986年   7篇
  1985年   11篇
  1984年   12篇
  1983年   14篇
  1982年   11篇
  1981年   9篇
  1980年   15篇
  1979年   9篇
  1978年   7篇
  1977年   8篇
  1975年   6篇
  1973年   7篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
131.
Results from a genome-wide screen of 10 multiplex families ascertained through probands with nonsyndromic cleft lip with or without cleft palate (CL/P) in Mexico, Argentina, and the United States yielded suggestive evidence of linkage to chromosomes 2, 6, 17 and 18. Fine mapping excluded all regions except chromosome 2. Subsequent analysis was performed on the original 10 families plus an additional 16 families using 31 markers on chromosome 2. This analysis showed intriguing evidence of linkage to 2q (Zlr=2.26, empirical P-value=0.028 in a chromosome-wide analysis). Transmission disequilibrium tests also revealed evidence of linkage and disequilibrium for two markers in this region (D2S168 and D2S1400 with P-values=0.022 and 0.006, respectively). A subset of these 26 families provided additional evidence for a susceptibility gene for CL/P on 2q, suggesting that further studies of genes in this region are warranted.  相似文献   
132.
BACKGROUND: Human metapneumovirus (hMPV) has been described as an etiologic agent of acute respiratory infections (ARI), mainly in pediatric patients. Viral isolation is difficult and has low sensitivity, and consequently RT-PCR assays are currently used for detection. OBJECTIVES: Detect hMPV in ARI in hospitalized children in Southern Brazil; standardize a RT-PCR for routine hMPV diagnosis; validate a positive control for molecular tests; and perform phylogenetics analyses. STUDY DESIGN: Nasopharyngeal aspirates (NPA) from 156 hospitalized children were studied. A conserved region of the nucleoprotein gene was cloned, characterized and used to standardize an RT-PCR assay. Phylogenetic analyses were performed. Clinical data were obtained from medical records. RESULTS: hMPV was detected in 6.4% of the samples. Dyspnea and wheezing were frequently reported symptoms and the most common diagnoses were bronchiolitis, acute respiratory insufficiency or laryngotracheobronchitis. Nucleotide sequence alignment revealed 97.7% identity with genotype A1 of hMPV. The detection limit of hMPV genomes by RT-PCR in clinical samples was 180 copies/microL. CONCLUSION: This is the first report of the detection and genetic characterization of hMPV infections in children with lower ARI in Southern Brazil.  相似文献   
133.
For both practical and methodological reasons, mice have been the most widely employed species for development of transgenic and gene knockin and knockout animals. However, basic behavioral and physiology control and regulatory mechanisms in mice are not well characterized. To broaden our understanding of the processes maintaining body fluid and blood pressure homeostasis in the mouse, the objectives of this study were to evaluate voluntary water, and sodium intakes during the development of renal hypertension and to examine the relationship between hypertension and the quantities of water and salt ingested. In male, C57BL/6J mice, two-kidney, one-clip renal hypertension (2K-1C) was induced, and water and 1.8% NaCl intakes were monitored for 2 weeks. At the end of this period, all animals received arterial catheters for direct recording of blood pressure. The mice that received renal artery clips were sorted into hypertensive (152+/-4 mm Hg) and normotensive (122+/-2 mm Hg) groups and were compared to control (117+/-4 mm Hg) animals that underwent a sham renal clipping procedure. Hypertensive 2K-1C animals had significantly elevated water intake compared to control animals. On most of the postsurgical days, the normotensive 2K-1C animals did not display increased water intake in comparison to the control group. No significant effect was detected for 1.8% saline intake between any of the pairs of groups. In summary, the reduction of blood flow to a single kidney in the 2K-1C model of renal hypertension induces high blood pressure accompanied by sustained hyperdipsia in the mouse.  相似文献   
134.
Summary It was found that naloxone causes a small but significant reduction of motility. The GABAB agonist baclofen and the GABA transaminase inhibitor-acetylenic GABA (GAG) also reduced locomotor activity. When a subeffective dose of baclofen was combined with naloxone 0.8 or 3.2 mg/kg, baclofen significantly inhibited motility beyond the inhibition caused by naloxone + saline. GAG, in a dose of 12.5 mg/kg, was also potentiated by naloxone, 3.2 mg/kg. The locomotion reducing effects of naloxone could be blocked by either picrotoxin or bicuculline. It is concluded that GABAergic mechanisms participate in the inhibition of locomotor activity provoked by naloxone. The possibility that this drug disinhibits GABAergic neurons is discussed.  相似文献   
135.
According to the reformulated learned helplessness model of depression, causal attributions are an important mediator of the effects on mood of positive and negative experiences. Adaptive attributions for negative events are assumed to be external, unstable, and specific. In the present study, subjects exposed to one of two attribution training procedures or a control condition made attributions for hypothetical events under neutral and adaptive instructional sets. Attributions were rated by subjects and coders blind to the purpose of the study. Results indicated that subjects' views of adaptive causal attributions were congruent with predictions from the learned helplessness model. The ratings of the objective coders indicated that subjects' attributions really did change in response to the adaptive instructions in the predicted direction. Implications of these results for the reformulated learned helplessness model and depression therapies that include an attribution retraining component are discussed.The authors would like to thank Dan Russell for his very helpful comments on earlier drafts of this paper.  相似文献   
136.
Journal of Public Health - The purpose of this paper is to investigate the implementation of value-based care principles in the context of frailty in the perioperative process, highlighting the...  相似文献   
137.
Background: A major problem of aging is the disruption of metabolic homeostasis. This is particularly relevant in the brain where it provokes neurodegeneration. Caloric restriction is a physiologic intervention known to delay the deleterious consequences of aging in several species ranging from yeast to mammals. To date, most studies on experimental models have started this dietary intervention from weaning, which is very difficult to be translated to human beings. Here, we study the effects of a more realistic dietary regimen in rats, starting at an advanced age and lasting for six months. Methods: we analyzed in the cortex and hippocampus, the proteins involved in the energetic balance of the cells, cholesterol metabolism, oxidative stress response, inflammation, synaptic impairment, and brain trophism. Results: our results suggest that caloric restriction in late life can revert only some age-related changes studied here.  相似文献   
138.
Frailty is the major expression of accelerated aging and describes a decreased resistance to stressors, and consequently an increased vulnerability to additional diseases in elderly people. The vascular aging related to frail phenotype reflects the high susceptibility for cardiovascular diseases and negative postoperative outcomes after cardiac surgery. Sarcopenia can be considered a biological substrate of physical frailty. Malnutrition and physical inactivity play a key role in the pathogenesis of sarcopenia. We searched on Medline (PubMed) and Scopus for relevant literature published over the last 10 years and analyzed the strong correlation between frailty, sarcopenia and cardiovascular diseases in elderly patient. In our opinion, a right food intake and moderate intensity resistance exercise are mandatory in order to better prepare patients undergoing cardiac operation.  相似文献   
139.
Bisphenol A (BPA) is an organic chemical compound widely used for manufacturing plastics. BPA exposure originates principally from the diet, but it can also originate from dermal contact. In over 90% of individuals, including pregnant women, BPA is detectable in several body fluids. The effects of this exposure on the fetus are under active investigation in several research laboratories. The aim of our work was to study the impact of prenatal exposure to BPA in the liver of rat fetuses from a sex-dependent point of view. We particularly investigated the effects of prenatal BPA exposure on hepatic lipids because of their crucial role, not only for the liver, but also for the whole-body functions. Our results demonstrate that the liver of rat fetuses, in utero exposed to a very low dose of BPA (2.5 µg/kg/day), displays significant modulations with regard to proteins involved in cholesterol and fatty acid biosynthesis and trafficking. Moreover, an impact on inflammatory process has been observed. All these effects are dependent on sex, being observable only in female rat fetuses. In conclusion, this work demonstrates that maternal exposure to BPA compromises hepatic lipid metabolism in female offspring, and it also reveals the perspective impact of BPA on human health at doses currently considered safe.  相似文献   
140.
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