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   8859篇
  免费   658篇
  国内免费   35篇
耳鼻咽喉   78篇
儿科学   265篇
妇产科学   80篇
基础医学   1194篇
口腔科学   202篇
临床医学   1003篇
内科学   2064篇
皮肤病学   79篇
神经病学   652篇
特种医学   316篇
外科学   1337篇
综合类   116篇
一般理论   7篇
预防医学   712篇
眼科学   171篇
药学   747篇
中国医学   3篇
肿瘤学   526篇
  2023年   54篇
  2022年   85篇
  2021年   253篇
  2020年   126篇
  2019年   224篇
  2018年   279篇
  2017年   179篇
  2016年   203篇
  2015年   200篇
  2014年   339篇
  2013年   421篇
  2012年   634篇
  2011年   708篇
  2010年   389篇
  2009年   356篇
  2008年   588篇
  2007年   561篇
  2006年   552篇
  2005年   586篇
  2004年   520篇
  2003年   490篇
  2002年   441篇
  2001年   109篇
  2000年   95篇
  1999年   91篇
  1998年   102篇
  1997年   77篇
  1996年   59篇
  1995年   53篇
  1994年   43篇
  1993年   39篇
  1992年   48篇
  1991年   44篇
  1990年   47篇
  1989年   40篇
  1988年   28篇
  1987年   36篇
  1986年   32篇
  1985年   39篇
  1984年   43篇
  1983年   37篇
  1982年   33篇
  1981年   34篇
  1980年   29篇
  1979年   16篇
  1978年   20篇
  1977年   21篇
  1976年   18篇
  1975年   17篇
  1972年   14篇
排序方式: 共有9552条查询结果,搜索用时 15 毫秒
991.
In December 2009, two unusual cases of anthrax were diagnosed in heroin users in Scotland. A subsequent anthrax outbreak in heroin users emerged throughout Scotland and expanded into England and Germany, sparking concern of nefarious introduction of anthrax spores into the heroin supply. To better understand the outbreak origin, we used established genetic signatures that provided insights about strain origin. Next, we sequenced the whole genome of a representative Bacillus anthracis strain from a heroin user (Ba4599), developed Ba4599-specific single-nucleotide polymorphism assays, and genotyped all available material from other heroin users with anthrax. Of 34 case-patients with B. anthracis-positive PCR results, all shared the Ba4599 single-nucleotide polymorphism genotype. Phylogeographic analysis demonstrated that Ba4599 was closely related to strains from Turkey and not to previously identified isolates from Scotland or Afghanistan, the presumed origin of the heroin. Our results suggest accidental contamination along the drug trafficking route through a cutting agent or animal hides used to smuggle heroin into Europe.  相似文献   
992.
Investigations of young workers, including limited surveys in supervised school settings, suggested their elevated injury risk. This study identified factors contributing to cuts-lacerations among adolescents in New Jersey secondary school career, technical, and vocational education programs. Of 1,772 injuries reported between December 1, 1998, and September 1, 2010, 777 (44%) were cuts-lacerations; analyses focused on 224 reports (n = 182 post-exclusions) submitted after fall 2005 in three career groups-Food, Hospitality & Tourism (FH&T) (n = 71), Manufacturing & Construction (M&C) (n = 84), and Automotive & Transportation (A&T) (n = 27). Most students were "struck by" tools or hard surfaces (n = 93, 51%); 63 cuts were from knives in FH&T. In M&C, most cuts-lacerations were caused by hand-held tools (n = 18) and being "struck against/by" or "caught between hard surfaces" (n = 19). Males reported more cuts-lacerations (n = 145), most commonly among 11th graders (n = 54) and ages 16 to 17 years (n = 79). Fingers (n = 117) were most often injured, usually by cutting tools (n = 83). Training, supervision, and appropriate equipment, and further assessments of "struck by" and "pinch point" hazards, are needed.  相似文献   
993.
994.
995.

Research Objective

To evaluate one of the first implemented provisions of the Patient Protection and Affordable Care Act (ACA), which permits young adults up to age 26 to enroll as dependents on a parent''s private health plan. Nearly one-in-three young adults lacked coverage before the ACA.

Study Design, Methods, and Data

Data from the Current Population Survey 2005–2011 are used to estimate linear probability models within a difference-in-differences framework to estimate how the ACA affected coverage of eligible young adults compared to slightly older adults. Multivariate models control for individual characteristics, economic trends, and prior state-dependent coverage laws.

Principal Findings

This ACA provision led to a rapid and substantial increase in the share of young adults with dependent coverage and a reduction in their uninsured rate in the early months of implementation. Models accounting for prior state dependent expansions suggest greater policy impact in 2010 among young adults who were also eligible under a state law.

Conclusions and Implications

ACA-dependent coverage expansion represents a rare public policy success in the effort to cover the uninsured. Still, this policy may have later unintended consequences for premiums for alternative forms of coverage and employer-offered rates for young adult workers.  相似文献   
996.
Medical Education 2012: 46 : 317–325 Objectives This study aimed to examine concepts of altruism and empathy among medical students and professionals in conjunction with health care initiatives designed to support the maintenance of these qualities. Methods We searched for the terms ‘altruism’, ‘altruistic’, ‘helping’, ‘prosocial behaviour’ and ‘empathy’ in the English‐language literature published from 1980 to the present within the Ovid MEDLINE, PsycInfo and PubMed databases. We used conceptual analysis to examine the relationships among altruism, empathy and related prosocial concepts in health care in order to understand how such factors may relate to emotional and career burnout, cynicism, decreased helping and decreased patient‐centredness in care. Results Altruistic ideals and qualities of empathy appear to decrease among some medical students as they progress through their education. During this process, students face increasingly heavy workloads, deal with strenuous demands and become more acquainted with non‐humanistic informal practices inherent in the culture of medicine. In combination, these factors increase the likelihood that emotional suppression, detachment from patients, burnout and other negative consequences may result, perhaps as a means of self‐preservation. Alternatively, by making a mindful and intentional choice to endeavour for self‐care and a healthy work–life balance, medical students can uphold humanistic and prosocial attitudes and behaviours. Conclusions Promoting altruism in the context of a compensated health care career is contradictory and misguided. Instead, an approach to clinical care that is prosocial and empathic is recommended. Training in mindfulness, self‐reflection and emotion skills may help medical students and professionals to recognise, regulate and behaviourally demonstrate empathy within clinical and professional encounters. However, health care initiatives to increase empathy and other humanistic qualities will be limited unless more practical and feasible emotion skills training is offered to and accepted by medical students. Success will be further moderated by the culture of medicine’s full acceptance of empathy and humanism into its customs, beliefs, values, interactions and daily practices.  相似文献   
997.
998.
Ho CS  Munster D  Pyke CM  Hart DN  López JA 《Blood》2002,99(8):2897-2904
Studies on purified blood dendritic cells (DCs) are hampered by poor viability in tissue culture. We, therefore, attempted to study some of the interactions/relationships between DCs and other blood cells by culturing unseparated peripheral blood mononuclear cell (PBMC) preparations in vitro. Flow cytometric techniques were used to undertake a phenotypic and functional analysis of DCs within the cultured PBMC population. We discovered that both the CD11c(+) and CD11c(-) CD123(hi) DC subsets maintained their viability throughout the 3-day culture period, without the addition of exogenous cytokines. This viability was accompanied by progressive up-regulation of the surface costimulatory (CD40, CD80, CD86) and activation (CMRF-44, CMRF-56, CD83) molecules. The survival and apparent production of DCs in PBMC culture (without exogenous cytokines) and that of sorted DCs (with cytokines) were evaluated and compared by using TruCOUNT analysis. Absolute DC counts increased (for CD123(hi) and CD11c(+) subsets) after overnight culture of PBMCs. Single-cell lineage depletion experiments demonstrated the rapid and spontaneous emergence of "new" in vitro generated DCs from CD14(+)/CD16(+) PBMC radioresistant precursors, additional to the preexisting ex vivo DC population. Unlike monocyte-derived DCs, blood DCs increased dextran uptake with culture and activation. Finally, DCs obtained after culture of PBMCs for 3 days were as effective as freshly isolated DCs in stimulating an allogeneic mixed leukocyte reaction.  相似文献   
999.
Objective—To study the mechanisms underlying the dominant `a' wave seen in patients with primary pulmonary hypertension.

Design—Retrospective and prospective examination of the jugular venous pulse recording, flow in the superior vena cava, and Doppler echocardiographic studies.

Setting—A tertiary referral centre for both cardiac and pulmonary disease, with facilities for invasive and noninvasive investigation, and assessment for heart and heart-lung transplantation.

Patients—12 patients with primary pulmonary hypertension, most being considered for heart-lung transplantation.

Results—Two distinct patterns of venous pulse and superior vena caval flow were identified: a dominant `a' wave with no `v' wave, an absent or poorly developed `y' descent, and exclusively systolic downward flow in the superior vena cava (group 1, n = 8), and a dominant `v' wave, deep `y' descent and exclusively diastolic downward flow in the superior vena cava (group 2, n = 4). A comparison between the two groups showed age (mean (SD)) 42 (18) ν 36 (7) years, RR interval 700 (65) ν 740 (240) ms, left ventricular end diastolic dimension 3·6 (0·8) ν 3·2 (1·0) cm and end systolic dimension 2·1 (0·5) ν 2·3 (0·3) cm, right ventricular end diastolic dimension 2·6 (0·5) ν 2·8 (0·6) cm, and pressure drop between right ventricle and right atrium 60 (8) ν 70 (34) mm Hg to be similar. Duration of tricuspid regurgitation 520 (30) ν 420 (130) ms and the time interval of pulmonary closure to the end of the tricuspid regurgitant signal 140 (30) ν 110 (40) ms were longer in group 1 compared with group 2, whereas right ventricular filling time was much shorter 180 (70) ν 350 (130) ms. In seven patients from group 1, a single peak of forward tricuspid flow was present, but this pattern was seen in only one patient from group 2.

Conclusions—In patients with primary pulmonary hypertension, the apparent `a' wave seen in the venous pulse is, in fact, a summation wave. It is probably the result of large pressure changes that must underlie rapid acceleration and deceleration of blood across the tricuspid valve when the right ventricular filling time is short.

  相似文献   
1000.
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