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   2580篇
  免费   163篇
  国内免费   59篇
耳鼻咽喉   23篇
儿科学   94篇
妇产科学   74篇
基础医学   298篇
口腔科学   30篇
临床医学   430篇
内科学   504篇
皮肤病学   23篇
神经病学   182篇
特种医学   359篇
外科学   229篇
综合类   38篇
一般理论   5篇
预防医学   239篇
眼科学   16篇
药学   135篇
中国医学   6篇
肿瘤学   117篇
  2022年   14篇
  2021年   34篇
  2020年   22篇
  2019年   22篇
  2018年   54篇
  2017年   33篇
  2016年   46篇
  2015年   55篇
  2014年   55篇
  2013年   83篇
  2012年   92篇
  2011年   90篇
  2010年   68篇
  2009年   74篇
  2008年   90篇
  2007年   156篇
  2006年   79篇
  2005年   128篇
  2004年   100篇
  2003年   75篇
  2002年   85篇
  2001年   74篇
  2000年   76篇
  1999年   64篇
  1998年   71篇
  1997年   52篇
  1996年   74篇
  1995年   53篇
  1994年   50篇
  1993年   65篇
  1992年   34篇
  1991年   44篇
  1990年   48篇
  1989年   50篇
  1988年   59篇
  1987年   65篇
  1986年   48篇
  1985年   58篇
  1984年   30篇
  1983年   24篇
  1982年   21篇
  1981年   32篇
  1980年   28篇
  1979年   16篇
  1978年   20篇
  1977年   29篇
  1976年   17篇
  1975年   17篇
  1971年   13篇
  1970年   13篇
排序方式: 共有2802条查询结果,搜索用时 31 毫秒
71.
Neuroprotective strategies that limit secondary tissue loss and/or improve functional outcomes have been identified in multiple animal models of ischemic, hemorrhagic, traumatic and nontraumatic cerebral lesions. However, use of these potential interventions in human randomized controlled studies has generally given disappointing results. In this paper, we summarize the current status in terms of neuroprotective strategies, both in the immediate and later stages of acute brain injury in adults. We also review potential new strategies and highlight areas for future research.  相似文献   
72.
This article describes six instruments developed for programs of research testing nursing interventions for individuals with dementia in Special Care Units and their family and staff caregivers. The Functional Abilities Checklist measures the functional abilities of residents with dementia. The Family Perceptions of Care Tool assesses family member satisfaction with care of the institutionalized relative with dementia. The Family Perceptions of Caregiving Role instrument evaluates stress experienced by family members of individuals with dementia related to their caregiving roles in long-term care settings. The Caregiver Stress Inventory and Staff Perceptions of Caregiving Role tools measure staff stress related to caring for residents with dementia. Finally, the Attitudes About Families Checklist assesses general staff attitudes about families of residents with dementia. Each instrument and its psychometric properties are described. The advantages of these instruments for research and clinical use with individuals with dementia are discussed.  相似文献   
73.
With the purpose of studying the role of proteinases in the development of ARDS, plasma levels of immunoreactive trypsin (IRT) and amylase were measured in 43 intensive care patients at risk of developing ARDS (22 polytrauma, seven abdominal surgery, four burns, two DIC and eight pancreatitis). Twenty four of these 43 patients developed ARDS and 31 presented abnormal IRT values (above 70 g/L). Twenty-one of these 31 patients had ARDS; a significant correlation thus appeared between ARDS and abnormal IRT values. In nine patients, IRT values were higher than 800 g/L and remained high for 3 to 4 days. A statistically significant correlation also appeared between abnormal IRT and septic phenomena: 20 patients with high IRT values presented septic problems. When IRT values were high, amylase values were often also abnormal: 12 of 23 patients with high IRT had abnormal amylase levels (the eight patients with documented pancreatitis were excluded); no other clinical signs or symptoms of pancreatitis were present in these patients. IRT could be one of the mediators of ARDS in septic patients. It is not clear that the pancreas is the origin of IRT in all cases.  相似文献   
74.
肠息肉发生的细胞和分子生物学研究进展   总被引:1,自引:0,他引:1  
肠息肉是一类从黏膜表面突出到肠腔内的隆起状病变的临床诊断.在最近的研究中陆续证实,其发生和发展的原因和机制,是由于Bmprla,APC,SMAD4,PTEN,STK11等基强突变而使各种细胞信号分子通过影响BMP信号通路,PTEN信号通路及Wnt信号通路所组成的生长信号调控网络,造成β-catenin在肠干细胞中的过度积聚,使得肠干细胞功能紊乱,导致其自我更新、克隆增殖、分化和凋亡失去平衡的结果.  相似文献   
75.
Objective: The present study examined whether early signs of maternal sensitivity can be detected during pregnancy by focusing on the maternal–fetal relationship and postnatal maternal sensitivity. Background: Earlier research has identified maternal sensitive behaviour as an important factor for the quality of the mother–infant relationship and the child’s emotional and cognitive development later in life. Research on this topic has predominantly focused on the postnatal period and little is known about early predictors (i.e. during pregnancy) of maternal sensitivity. Methods: Participants were 273 women and their (unborn) infants. Mothers’ attitudes, thoughts and feelings towards the fetus were assessed by the Maternal Antenatal Attachment Scale at 26 weeks of gestation. At the infant’s age of 6 months, maternal sensitivity was assessed in three different situations (i.e. face-to-face play, caregiving and free play) using the NICHD global rating scales. Results: Mothers with a higher quality of the maternal–fetal relationship displayed more maternal sensitivity towards their 6-month-old infant in caregiving and free play situations, even when controlling for covariates such as parity, ethnicity, maternal education, maternal age and the postnatal mother–infant relationship. No associations were found in the face-to-face situation. Conclusion: This study shows that mothers who reported a higher quality of the maternal–fetal relationship were more sensitive while interacting with their infants during caregiving and free play, but not during face-to-face play.  相似文献   
76.
OBJECTIVE: To determine how often requests are made for euthanasia and physician-assisted suicide (EAS) in the absence of severe disease and how such requests are dealt with in medical practice in The Netherlands. METHOD: Retrospective interview study. Participants: 125 general practitioners (GPs), 77 nursing home physicians (NHPs), and 208 clinical specialists. RESULTS: In The Netherlands, each year approximately 400 people request EAS, because they are 'weary of life'. Thirty per cent of all physicians have at some time received an explicit request for EAS in the absence of severe disease; 3% of all physicians had granted a request for EAS in such a case. Most requests for EAS to GPs in the absence of severe disease (n = 29) were made by single people aged 80 years and over. While their problems were most frequently of a social nature, 79% had one or more non-severe illnesses. Most GPs refused the request; half of them proposed an alternative treatment, which the patient often refused. Nineteen people who did not receive any treatment persisted in their wish to die; the request for EAS from 5 out of 10 patients who received one or more types of treatment was withdrawn or became less explicit. CONCLUSIONS: Most physicians in The Netherlands refuse requests for EAS in the absence of severe disease. Most patients persist in their request. In an ageing population more research is needed to provide physicians with practical interventions to prevent suicide and to make life bearable and satisfactory for elderly people who wish to die.  相似文献   
77.
78.
Exposure to ambient particulate matter (PM) has been linked to several adverse health effects. Since vehicular traffic is a PM source of growing importance, we sampled total suspended particulate (TSP), PM(10), and PM(2.5) at six urban locations with pronounced differences in traffic intensity. The mutagenicity, DNA-adduct formation, and induction of oxidative DNA damage by the samples were studied as genotoxicological parameters, in relation to polycyclic aromatic hydrocarbon (PAH) levels, elemental composition, and radical-generating capacity (RGC) as chemical characteristics. We found pronounced differences in the genotoxicity and chemical characteristics of PM from the various locations, although we could not establish a correlation between traffic intensity and any of these characteristics for any of the PM size fractions. Therefore, the differences between locations may be due to local sources of PM, other than traffic. The concentration of total (carcinogenic) PAHs correlated positively with RGC, direct and S9-mediated mutagenicity, as well as the induction of DNA adducts and oxidative DNA damage. The interaction between total PAHs and transition metals correlated positively with DNA-adduct formation, particularly from the PM(2.5) fraction. RGC was not associated with one specific PM size fraction, but mutagenicity and DNA reactivity after metabolic activation were relatively high in PM(10) and PM(2.5), when compared with TSP. We conclude that the toxicological characteristics of urban PM samples show pronounced differences, even when PM concentrations at the sample sites are comparable. This implies that emission reduction strategies that take chemical and toxicological characteristics of PM into account may be useful for reducing the health risks associated with PM exposure.  相似文献   
79.
In the developing amniote limb, anteroposterior (A/P) patterning is controlled through secretion of the Sonic Hedgehog (SHH) protein by cells in the zone of polarizing activity (ZPA) located in the posterior mesoderm. In the chicken mutant oligozeugodactyly (ozd), Shh is expressed normally in the entire embryo with the exception that it is undetectable in the developing limbs; this results in the loss of specific bones in wings and legs. The ozd phenotype is similar to that of humans affected with acheiropodia (ACHR), and the ACHR mutation has been mapped to a deletion of exon 4 and portions of introns 3 and 4 in the LMBR1 gene. We have cloned the chick ortholog of LMBR1, Lmbr1, and report that, in chick, Lmbr1 is expressed within the ZPA. Although the ozd phenotype is similar to ACHR, the open reading frame of Lmbr1 is normal in ozd. Sequence analysis of Lmbr1 intron 3 demonstrated that this particular genomic region segregates with the ozd phenotype. In addition, overexpression of Lmbr1 throughout the developing limb mesoderm resulted in morphologically normal limbs. Collectively, these data suggest that the Lmbr1 coding sequence is not required for normal chick limb development. We propose that the ozd mutation is linked to the genomic region containing Shh and Lmbr1.  相似文献   
80.
Hirschsprung disease (HSCR), a congenital disorder characterized by intestinal obstruction due to absence of enteric ganglia along variable lengths of the intestinal tract, occurs both in familial and sporadic cases. RET mutations have been found in approximately 50% of the families, but explains only a minority of sporadic cases. This study aims at investigating a possible role of RET in sporadic HSCR patients. Haplotypes of 13 DNA markers, within and flanking RET, have been determined for 117 sporadic HSCR patients and their parents. Strong association was observed for six markers in the 5' region of RET. The largest distortions in allele transmission were found at the same markers. One single haplotype composed of these six markers was present in 55.6% of patients versus 16.2% of controls. Odds ratios (ORs) revealed a highly increased risk of homozygotes for this haplotype to develop HSCR (OR>20). These results allowed us to conclude that RET plays a crucial role in HSCR even when no RET mutations are found. An unknown functional disease variant(s) with a dosage-dependent effect in HSCR is likely located between the promoter region and exon 2 of RET.  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