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   1803篇
  免费   247篇
  国内免费   21篇
耳鼻咽喉   9篇
儿科学   58篇
妇产科学   31篇
基础医学   93篇
口腔科学   73篇
临床医学   271篇
内科学   466篇
皮肤病学   38篇
神经病学   86篇
特种医学   301篇
外科学   141篇
综合类   24篇
预防医学   287篇
眼科学   11篇
药学   47篇
肿瘤学   135篇
  2023年   48篇
  2022年   13篇
  2021年   11篇
  2020年   40篇
  2019年   18篇
  2018年   54篇
  2017年   33篇
  2016年   44篇
  2015年   54篇
  2014年   96篇
  2013年   120篇
  2012年   36篇
  2011年   52篇
  2010年   65篇
  2009年   84篇
  2008年   51篇
  2007年   78篇
  2006年   51篇
  2005年   41篇
  2004年   42篇
  2003年   17篇
  2002年   16篇
  2001年   29篇
  2000年   31篇
  1999年   31篇
  1998年   67篇
  1997年   90篇
  1996年   80篇
  1995年   58篇
  1994年   63篇
  1993年   53篇
  1992年   27篇
  1991年   29篇
  1990年   46篇
  1989年   53篇
  1988年   40篇
  1987年   39篇
  1986年   40篇
  1985年   41篇
  1984年   19篇
  1983年   17篇
  1982年   27篇
  1981年   32篇
  1980年   20篇
  1979年   11篇
  1978年   12篇
  1977年   18篇
  1976年   18篇
  1975年   10篇
  1969年   2篇
排序方式: 共有2071条查询结果,搜索用时 15 毫秒
51.
Coronavirus disease 2019 (COVID-19) continues to impact older adults disproportionately with respect to serious consequences ranging from severe illness and hospitalization to increased mortality risk. Concurrently, concerns about potential shortages of healthcare professionals and health supplies to address these issues have focused attention on how these resources are ultimately allocated and used. Some strategies, for example, misguidedly use age as an arbitrary criterion that disfavors older adults in resource allocation decisions. This is a companion article to the American Geriatrics Society (AGS) position statement, “Resource Allocation Strategies and Age-Related Considerations in the COVID-19 Era and Beyond.” It is intended to inform stakeholders including hospitals, health systems, and policymakers about ethical considerations that should be considered when developing strategies for allocation of scarce resources during an emergency involving older adults. This review presents the legal and ethical background for the position statement and discusses these issues that informed the development of the AGS positions: (1) age as a determining factor, (2) age as a tiebreaker, (3) criteria with a differential impact on older adults, (4) individual choices and advance directives, (5) racial/ethnic disparities and resource allocation, and (6) scoring systems and their impact on older adults. It also considers the role of advance directives as expressions of individual preferences in pandemics. J Am Geriatr Soc 68:1143–1149, 2020.  相似文献   
52.

Objectives

Frailty is a clinical syndrome characterized by decreased physiologic reserve that diminishes the ability to respond to stressors such as acute illness. Veterans Health Administration (VA) emergency departments (ED) are the primary venue of care for Veterans with acute illness and represent key sites for frailty recognition. As questionnaire-based frailty instruments can be cumbersome to implement in the ED, we examined two administratively derived frailty scores for use among VA ED patients.

Methods

This national retrospective cohort study included all VA ED visits (2017–2020). We evaluated two administratively derived scores: the Care Assessment Needs (CAN) score and the VA Frailty Index (VA-FI). We categorized all ED visits across four frailty groups and examined associations with outcomes of 30-day and 90-day hospitalization and 30-day, 90-day, and 1-year mortality. We used logistic regression to assess the model performance of the CAN score and the VA-FI.

Results

The cohort included 9,213,571 ED visits. With the CAN score, 28.7% of the cohort were classified as severely frail; by VA-FI, 13.2% were severely frail. All outcome rates increased with progressive frailty (p-values for all comparisons < 0.001). For example, for 1-year mortality based on the CAN score frailty was determined as: robust, 1.4%; prefrail, 3.4%; moderately frail, 7.0%; and severely frail, 20.2%. Similarly, for 90-day hospitalization based on VA-FI, frailty was determined as prefrail, 8.3%; mildly frail, 15.3%; moderately frail, 29.5%; and severely frail, 55.4%. The c-statistics for CAN score models were higher than for VA-FI models across all outcomes (e.g., 1-year mortality, 0.721 vs. 0.659).

Conclusions

Frailty was common among VA ED patients. Increased frailty, whether measured by CAN score or VA-FI, was strongly associated with hospitalization and mortality and both can be used in the ED to identify Veterans at high risk for adverse outcomes. Having an effective automatic score in VA EDs to identify frail Veterans may allow for better targeting of scarce resources.  相似文献   
53.
54.
The role of dopaminergic terminals in the medial preoptic area (MPO) in the regulation of male rat copulatory behavior was investigated. A 6-hydroxydopamine (6-OHDA) injection into the MPO of animals pretreated with desipramine resulted in a small (23%) depletion of DA, and no impairment of copulatory activity. Further depletion of catecholamines with alpha-methyl p-tyrosine (AMPT) produced several deficits in the copulatory behavior of 6-OHDA-treated males, at a dose of AMPT that did not adversely affect copulation prior to 6-OHDA administration. The dose-related effects of intracranial apomorphine (APO) injections were also altered by 6-OHDA injections into the MPO. The inhibition previously found with 0.2 microgram of APO into the lateral ventricle of normal males was abolished by 6-OHDA treatment. A facilitation of copulatory behavior was observed following the injection of 0.2 microgram of APO into the MPO of 6-OHDA-treated animals, whereas this treatment did not affect the copulatory behavior of intact animals. Finally, inhibitory effects observed following an injection of 0.1 microgram of APO into the MPO of normal males were blocked by 6-OHDA administration. The relative roles of presynaptic autoreceptors and postsynaptic DA receptors in the MPO in mediating the dose-related effects of APO on copulatory behavior are discussed.  相似文献   
55.
56.
57.
OBJECTIVE: To identify predictors and outcomes associated with frequent emergency department (ED) users. METHODS: Cross-sectional intake surveys, medical chart reviews, and telephone follow-up interviews of patients presenting with selected chief complaints were performed at five urban EDs during a one-month study period in 1995. Frequent use was defined by four or more self-reported, prior ED visits. Multivariate logistic regression identified predictors of frequent ED visitors from five domains (demographics, health status, health access, health care preference, and severity of acute illness). Associations between high use and selected outcomes were assessed with logistic regression models. RESULTS: All study components were completed by 2,333 of 3,455 eligible patients (67.5%). Demographics predicting frequent use included being a single parent, single or divorced marital status, high school education or less, and income of less than $10,000 (1995). Health status predictors included hospitalization in the preceding three months, high ratings of psychological distress, and asthma. Health access predictors included identifying an ED or a hospital clinic as the primary care site, having a primary care physician (PCP), and visiting a PCP in the past month. Choosing the ED for free care was the only health preference predictive of heavy use. Illness severity measures were higher in frequent visitors, although these were not independently predictive in the multivariate model. Outcomes correlated with heavy use include increased hospital admissions, higher rates of ED return visits, and lower patient satisfaction, but not willingness to return to the ED or follow-up with a doctor. CONCLUSIONS: Frequent ED visits are associated with socioeconomic distress, chronic illness, and high use of other health resources. Efforts to reduce ED visits require addressing the unique needs of these patients in the emergency and primary care settings.  相似文献   
58.
59.
60.
INTRODUCTION: This study examined the reproductive function and prevalence of polycystic ovary syndrome (PCOS) in women with bipolar disorder taking antimanic medications. METHOD: Women aged 18-45 treated for bipolar disorder and not taking steroid contraceptives were recruited to complete questionnaires about their menstrual cycle and to provide blood samples for measurement of a range of reproductive endocrine and metabolic hormone levels. Eighty women participated in completing the questionnaires and 72 of them provided blood samples. RESULTS: Fifty-two of the 80 women (65%) reported current menstrual abnormalities, 40 of which (50%) reported one or more menstrual abnormalities that preceded the diagnosis of bipolar disorder. Fifteen women (38%) reported developing menstrual abnormalities since treatment for bipolar disorder, 14 of which developed abnormalities since treatment with valproate (p = 0.04). Of the 15 patients reporting menstrual abnormalities since starting medication, 12 (80%) reported changes in menstrual flow (heavy or prolonged bleeding) and five (33%) reported changes in cycle frequency. No significant differences were observed between women receiving or not receiving valproate in mean levels of free or total serum testosterone levels. This was true for the total sample and for the sub-group without preexisting menstrual problems. However, within the valproate group, duration of use was significantly correlated with free testosterone levels (r = 0.33, p = 0.02). Three of the 50 women (6%) taking VPA, and 0% of the 22 taking other antimanic medications, met criteria for PCOS (p = 0.20). Other reproductive and metabolic values outside the normal range across treatment groups included elevated 17 alpha-OH progesterone levels, luteinizing hormone: follicle-stimulating hormone ratios, homeostatic model assessment (HOMA) values, and low estrogen and dehydroepiandrosterone sulfate (DHEAS) levels. Preexisting menstrual abnormalities predicted higher levels of 17 alpha-OH progesterone, free testosterone, and estrone as well as development of new menstrual abnormalities. Body mass index (BMI) was significantly positively correlated with free testosterone levels and insulin resistance (HOMA) across all subjects, regardless of medication used. CONCLUSIONS: Rates of menstrual disturbances are high in women with bipolar disorder and, in many cases, precede the diagnosis and treatment for the disorder. Treatment with valproate additionally contributes significantly to the development of menstrual abnormalities and an increase in testosterone levels over time. A number of bipolar women, regardless of type of medication treatment received, have reproductive and metabolic hormonal abnormalities, yet the etiology of such abnormalities requires further study. Women with preexisting menstrual abnormalities may represent a group at risk for development of reproductive dysfunction while being treated for bipolar disorder.  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