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   669020篇
  免费   34654篇
  国内免费   640篇
耳鼻咽喉   8910篇
儿科学   21602篇
妇产科学   15680篇
基础医学   113217篇
口腔科学   16886篇
临床医学   60260篇
内科学   120970篇
皮肤病学   15864篇
神经病学   48220篇
特种医学   26136篇
外国民族医学   53篇
外科学   99228篇
综合类   8256篇
现状与发展   2篇
一般理论   151篇
预防医学   46051篇
眼科学   14902篇
药学   50821篇
  1篇
中国医学   1336篇
肿瘤学   35768篇
  2021年   5574篇
  2019年   5620篇
  2018年   8926篇
  2017年   6845篇
  2016年   8319篇
  2015年   8408篇
  2014年   10531篇
  2013年   16283篇
  2012年   22995篇
  2011年   25618篇
  2010年   14639篇
  2009年   12071篇
  2008年   23892篇
  2007年   25955篇
  2006年   25106篇
  2005年   24253篇
  2004年   23432篇
  2003年   22837篇
  2002年   22191篇
  2001年   27343篇
  2000年   29216篇
  1999年   22382篇
  1998年   6664篇
  1997年   5510篇
  1996年   5315篇
  1995年   4888篇
  1992年   15097篇
  1991年   16395篇
  1990年   16509篇
  1989年   16208篇
  1988年   14778篇
  1987年   14747篇
  1986年   13621篇
  1985年   13351篇
  1984年   10020篇
  1983年   8532篇
  1982年   4745篇
  1979年   9398篇
  1978年   6820篇
  1977年   5608篇
  1976年   5892篇
  1975年   7004篇
  1974年   7791篇
  1973年   7486篇
  1972年   6854篇
  1971年   6609篇
  1970年   6145篇
  1969年   5692篇
  1968年   5393篇
  1967年   4866篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
Objectives: The steeling effect suggests that early-life adversity can have a beneficial impact later in life. However, little is known about its underlying mechanisms and long-term outcomes . The study aimed to examine the role of early-life adversity (ELA) on successful aging, and whether this relationship can be explained by mental and physical health.

Method: Socio-demographics, early-life adversity (ELA), individual quality of life (iQoL), and mental and physical health of 270 individuals (Mage = 66.82 years, 71.5% female) were assessed. Polynomial regressions and mediation analyses were conducted.

Results: Significant inverse U-shaped associations were found between ELA and iQoL (β = ?.59, p = .005) and between ELA and mental health (β = ?.64, p = .002), but not between ELA and physical health. Furthermore, mental health significantly mediated the relationship between ELA and iQoL (b = ?.84, BCa CI [?1.66, ?.27]).

Conclusion: Highest level of individual quality of life (i.e. successful aging) was related to a moderate amount of ELA. Additionally, mental health significantly mediated this relationship. These findings suggest that some amount of ELA could be beneficial for successful aging. Resource-focused interventions are needed to improve health and promote successful aging for an underdetected, at-risk subgroup with low early-life adversity.  相似文献   

6.

Objective

Low psoas muscle area is shown to be an indicator for worse postoperative outcome in patients undergoing vascular surgical. Additionally, it has been associated with longer durations of hospital stay in patients with cancer who undergo surgery and subsequently greater health care costs in Europe and the United States. We sought to evaluate this effect on hospital expenditure for patients undergoing vascular repair in a health care system with universal access.

Methods

Skeletal muscle mass was assessed on preoperative abdominal computed tomography scans of patients undergoing open aortic aneurysm repair in a retrospective fashion. The skeletal muscle index (SMI) was used to define low muscle mass. Health care costs were obtained for all patients and the relationship between a low SMI and higher costs was explored using linear regression and cross-sectional analysis.

Results

We included 156 patients (81.5% male) with a median age of 72 years undergoing elective surgery for infrarenal abdominal aortic aneurysm in this analysis. The median SMI for patients with low skeletal muscle mass was 53.21 cm2/kg and for patients without, 70.07 cm2/kg. Hospital duration of stay was 2 days longer in patients with low skeletal muscle mass as compared with patients with normal (14 days vs 11 days; P = .001), as was duration of intensive care stay (3 days vs 1 day; P = .01). The median overall hospital costs were €10,460 higher for patients with a low SMI as compared with patients with a normal physical constitution (€53,739 [interquartile range, €45,007-€62,471] vs €43,279 [interquartile range, €39,509-€47,049]; P = .001). After confounder adjustment, a low SMI was associated with a 14.68% cost increase in overall hospital costs, for a cost increase of €6521.

Conclusions

Low skeletal muscle mass is independently associated with higher hospital as well as intensive care costs in patients undergoing elective aortic aneurysm repair. Strategies to reduce this risk factor are warranted for these patients.  相似文献   
7.
BackgroundA venous leg ulcer is a chronic leg wound caused by poor venous blood circulation in the lower limbs. It is a recurring condition causing pain, malodour, reduced mobility, and depression. Randomised controlled trials evaluating treatments for venous leg ulcers provide important evidence to inform clinical decision-making. However, for findings to be useful, outcomes need to be clinically meaningful, consistently reported across trials, and fully reported. Research has identified the large number of outcomes reported in venous leg ulcer trials, impacting both synthesis of results, and clinical decision-making. To address this, a core outcome set will be developed. A core outcome set is an agreed standardised set of outcomes which should be, as a minimum, measured and reported in all trials which evaluate treatment effectiveness for a given indication. A core outcome set has the potential to reduce research waste, improve the utility of RCTs, reduce reporting bias, facilitate treatment comparisons across different sources of evidence and expedite the production of systematic reviews, meta-analyses and evidence-based clinical guidelines.AimThe aim of this project is to develop a core outcome set for research evaluating the effectiveness of interventions for treating venous leg ulceration.MethodsThrough a scoping review of the literature on venous leg ulceration, we will firstly identify a list of candidate outcome domains (broad categories in relation to what is being measured) from randomised controlled trials and qualitative research, and outcomes (specific methods in relation to what is being measured). In two further stages, we will use the resulting lists of outcome domains and outcomes to design two online surveys. A range of stakeholders will be invited to participate in the surveys and they will be asked to indicate which outcome domains and outcomes are most important and should be considered as core in future research reports.  相似文献   
8.
BACKGROUND AND PURPOSE:In the chronic phase after traumatic brain injury, DTI findings reflect WM integrity. DTI interpretation in the subacute phase is less straightforward. Microbleed evaluation with SWI is straightforward in both phases. We evaluated whether the microbleed concentration in the subacute phase is associated with the integrity of normal-appearing WM in the chronic phase.MATERIALS AND METHODS:Sixty of 211 consecutive patients 18 years of age or older admitted to our emergency department ≤24 hours after moderate to severe traumatic brain injury matched the selection criteria. Standardized 3T SWI, DTI, and T1WI were obtained 3 and 26 weeks after traumatic brain injury in 31 patients and 24 healthy volunteers. At baseline, microbleed concentrations were calculated. At follow-up, mean diffusivity (MD) was calculated in the normal-appearing WM in reference to the healthy volunteers (MDz). Through linear regression, we evaluated the relation between microbleed concentration and MDz in predefined structures.RESULTS:In the cerebral hemispheres, MDz at follow-up was independently associated with the microbleed concentration at baseline (left: B = 38.4 [95% CI 7.5–69.3], P = .017; right: B = 26.3 [95% CI 5.7–47.0], P = .014). No such relation was demonstrated in the central brain. MDz in the corpus callosum was independently associated with the microbleed concentration in the structures connected by WM tracts running through the corpus callosum (B = 20.0 [95% CI 24.8–75.2], P < .000). MDz in the central brain was independently associated with the microbleed concentration in the cerebral hemispheres (B = 25.7 [95% CI 3.9–47.5], P = .023).CONCLUSIONS:SWI-assessed microbleeds in the subacute phase are associated with DTI-based WM integrity in the chronic phase. These associations are found both within regions and between functionally connected regions.

The yearly incidence of traumatic brain injury (TBI) is around 300 per 100,000 persons.1,2 Almost three-quarters of patients with moderate to severe TBI have traumatic axonal injury (TAI).3 TAI is a major predictor of functional outcome,4,5 but it is mostly invisible on CT and conventional MR imaging.6,7DTI provides direct information on WM integrity and axonal injury.5,8 However, DTI abnormalities are neither specific for TAI nor stable over time. Possibly because of the release of mass effect and edema and resorption of blood products, the effects of concomitant (non-TAI) injury on DTI are larger in the subacute than in the chronic phase (>3 months).4,9,10 Therefore, DTI findings are expected to reflect TAI more specifically in the chronic than in the subacute phase (1 week–3 months).4 Even in regions without concomitant injury, the effects of TAI on DTI are dynamic, possibly caused by degeneration and neuroplastic changes.6,11,12 These ongoing pathophysiological processes possibly contribute to the emerging evidence that DTI findings in the chronic phase are most closely associated with the eventual functional outcome.12,13Although DTI provides valuable information, its acquisition, postprocessing, and interpretation in individual patients are demanding. SWI, with which microbleeds can be assessed with high sensitivity, is easier to interpret and implement in clinical practice. In contrast to DTI, SWI-detected traumatic microbleeds are more stable1 except in the hyperacute14,15 and the late chronic phases.16 Traumatic cerebral microbleeds are commonly interpreted as signs of TAI. However, the relation is not straightforward. On the one hand, nontraumatic microbleeds may be pre-existing. On the other hand, even if traumatic in origin, microbleeds represent traumatic vascular rather than axonal injury.17 Indeed, TAI is not invariably hemorrhagic.18 Additionally, microbleeds may secondarily develop after trauma through mechanisms unrelated to axonal injury, such as secondary ischemia.18DTI is not only affected by pathophysiological changes but also by susceptibility.19 The important susceptibility-effect generated by microbleeds renders the interpretation of DTI findings at the location of microbleeds complex. In the chronic phase, mean diffusivity (MD) is the most robust marker of WM integrity.4,6 For these reasons, we evaluated MD in the normal-appearing WM.Much TAI research focuses on the corpus callosum because it is commonly involved in TAI5,18,20 and it can reliably be evaluated with DTI,5,21 and TAI in the corpus callosum is related to clinical prognosis.6,20 The corpus callosum consists of densely packed WM tracts that structurally and functionally connect left- and right-sided brain structures.22 The integrity of the corpus callosum is associated with the integrity of the brain structures it connects.23 Therefore, microbleeds in brain structures that are connected through the corpus callosum may affect callosal DTI findings. Analogous to this, microbleeds in the cerebral hemispheres, which exert their function through WM tracts traveling through the deep brain structures and brain stem,24,25 may affect DTI findings in the WM of the latter.Our purpose was to evaluate whether the microbleed concentration in the subacute phase is associated with the integrity of normal-appearing WM in the chronic phase. We investigated this relation within the cerebral hemispheres and the central brain and between regions that are functionally connected by WM tracts.  相似文献   
9.
10.

Aims

Variations of the anatomy of donor hepatic arteries increase the number of arterial anastomoses during liver transplantation and, possibly, the incidence of hepatic artery thrombosis (HAT). In this study, we describe the arterial anatomic variations in liver grafts procured and transplanted by a single center in Greece, the techniques of arterial anastomosis, and their effect on the incidence of early HAT.

Materials and Methods

From January 2013 to December 2017, the arterial anatomy of 116 grafts procured for liver transplantation were recorded, as well as the technique of arterial anastomosis and the incidence of early hepatic artery thrombosis (HAT <30 days).

Results

A single hepatic artery was recorded in 72.41% of the procured grafts, an aberrant left hepatic artery (accessory or replaced) in 18 grafts (15.52%), and an aberrant right hepatic artery (accessory or replaced) in 17 grafts (14.66%), while other variations were observed in less than 1% of the procured livers. Of the 116 primary liver transplantations, 6 patients (5.17%) developed early HAT <30 days. Two of these patients (1.72%) had 1 anastomosis of the hepatic artery and 4 (3.45%) had 2 anastomoses due to anatomic variations.

Conclusions

Anatomic variations of the hepatic artery in liver grafts is a common finding and increase the incidence of early HAT but not to a degree to make these grafts unusable.  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