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   2614篇
  免费   207篇
  国内免费   4篇
耳鼻咽喉   12篇
儿科学   90篇
妇产科学   67篇
基础医学   480篇
口腔科学   25篇
临床医学   257篇
内科学   467篇
皮肤病学   40篇
神经病学   357篇
特种医学   37篇
外科学   273篇
综合类   20篇
一般理论   8篇
预防医学   387篇
眼科学   25篇
药学   139篇
中国医学   7篇
肿瘤学   134篇
  2024年   10篇
  2023年   55篇
  2022年   71篇
  2021年   171篇
  2020年   85篇
  2019年   144篇
  2018年   139篇
  2017年   103篇
  2016年   104篇
  2015年   80篇
  2014年   117篇
  2013年   155篇
  2012年   202篇
  2011年   182篇
  2010年   86篇
  2009年   109篇
  2008年   133篇
  2007年   158篇
  2006年   122篇
  2005年   115篇
  2004年   106篇
  2003年   85篇
  2002年   59篇
  2001年   19篇
  2000年   18篇
  1999年   23篇
  1998年   17篇
  1997年   9篇
  1996年   9篇
  1995年   3篇
  1994年   3篇
  1993年   3篇
  1992年   5篇
  1991年   9篇
  1990年   10篇
  1989年   11篇
  1988年   6篇
  1987年   8篇
  1986年   9篇
  1985年   10篇
  1984年   8篇
  1981年   4篇
  1980年   5篇
  1979年   5篇
  1978年   6篇
  1977年   3篇
  1975年   3篇
  1974年   6篇
  1973年   3篇
  1967年   2篇
排序方式: 共有2825条查询结果,搜索用时 15 毫秒
11.
We previously showed that granulocyte-macrophage colony-stimulating factor (GM-CSF) breaks tolerance induction. The objective of this study was to determine whether GM-CSF breaks established inhalation tolerance. To induce tolerance, BALB/c mice were exposed to aerosolized ovalbumin (OVA) for 10 consecutive days. A control group was exposed to saline. Subsequently, tolerant and control animals were exposed to OVA in a GM-CSF-enriched airway microenvironment. Tolerant animals, unlike control animals, did not develop airway and peripheral blood eosinophilia, had diminished levels of OVA-specific IgE, and reduced airway hyper-responsiveness. While tolerant animals did not express IL-4, IL-5 and IL-13, levels of the regulatory cytokines IL-10, IFN-gamma and transfoming growth factor (TGF)-beta were similar between tolerant and non-tolerant animals. Lung CD4+ T cells were activated according to CD69, CD25 and T1/ST2 expression, but systemic responses characterized by splenocyte proliferation and Th2 effector function were dramatically reduced. Concurrent expression of GM-CSF and decorin, a natural inhibitor of TGF-beta, reversed eosinophilic unresponsiveness. Our study suggests that the breakdown of tolerance and, by extension, the emergence of eosinophilic inflammation, requires two signals: one that triggers sensitization and one that interferes with negative regulation. Moreover, our study shows that dysregulated expression of an extracellular matrix protein may break established tolerance and lead to eosinophilic airway inflammation.  相似文献   
12.
Megalencephaly (MEG) is a developmental abnormality of brain growth characterized by early onset, often progressive, brain overgrowth. Focal forms of megalencephaly associated with cortical dysplasia, such as hemimegalencephaly and focal cortical dysplasia, are common causes of focal intractable epilepsy in children. The increasing use of high throughput sequencing methods, including high depth sequencing to more accurately detect and quantify mosaic mutations, has allowed us to identify the molecular etiologies of many MEG syndromes, including most notably the PI3K‐AKT‐MTOR related MEG disorders. Thorough molecular and clinical characterization of affected individuals further allow us to derive preliminary genotype–phenotype correlations depending on the gene, mutation, level of mosaicism, and tissue distribution. Our review of published data on these disorders so far shows that mildly activating variants (that are typically constitutional or germline) are associated with diffuse megalencephaly with intellectual disability and/or autism spectrum disorder; moderately activating variants (that are typically high‐level mosaic) are associated with megalencephaly with pigmentary abnormalities of the skin; and strongly activating variants (that are usually very low‐level mosaic) are associated with focal brain malformations including hemimegalencephaly and focal cortical dysplasia. Accurate molecular diagnosis of these disorders is undoubtedly crucial to more optimally treat children with these disorders using PI3K‐AKT–MTOR pathway inhibitors.  相似文献   
13.
The development of emotional behavior is dependent on the early experiences of the infant and the quality of maternal care. In these experiments, the effects of social isolation during the preweaning period on both pup behavior and maternal responsivity were examined. In the first study, the number of ultrasonic vocalizations (USVs) emitted after brief maternal separation was measured in neonatal rats with differing histories of social isolation. The social isolation procedure consisted of 5 days of daily separation from the dam and littermates for either 3 or 6 hr. At both ages tested, socially isolated pups vocalized significantly less than control pups. In the second study, the effects of prior isolation either daily for 5 previous days (Chronic Isolation) or for 4 hr prior to testing (Acute Isolation) were examined in a T-maze choice test. Pup vocalizations in the presence of the dam and dams' maternal behavior were assessed. When the dam was confined to the start box or during the maternal free access period, both Chronic and Acute Isolates vocalized less than pups that had never left the home nest. Dams spent more time with and licked and groomed more frequently and for a longer time both Chronic and Acute Isolates compared to pups that had always been with dams in the home nest. These results suggest that early isolation experience can alter subsequent responses to separation stress in neonatal rats and that maternal behavior is sensitive to the prior experiences of offspring.  相似文献   
14.
CONTEXT—Chromosomal abnormalities that involve the proximal region of chromosome 15q occur relatively frequently in the human population. However, interstitial triplications involving one 15 homologue are very rare with three cases reported to date.
OBJECTIVE—To provide a detailed molecular characterisation of four additional patients with interstitial triplications of chromosome 15q11-q14.
DESIGN—Molecular analyses were performed using DNA markers and probes specific for the 15q11-q14 region.
SETTING—Molecular cytogenetics laboratory at the University of Chicago.
SUBJECTS—Four patients with mild to severe mental retardation and features of Prader-Willi syndrome (PWS) or Angelman syndrome (AS) were referred for molecular cytogenetic analysis following identification of a suspected duplication/triplication of chromosome 15q11-q14 by routine cytogenetic analysis.
MAIN OUTCOME MEASURES—Fluorescence in situ hybridisation (FISH) was performed to determine the type of chromosomal abnormality present, the extent of the abnormal region, and the orientation of the extra chromosomal segments. Molecular polymorphism analysis was performed to determine the parental origin of the abnormality. Methylation and northern blot analyses of the SNRPN gene were performed to determine the effect of extra copies of the SNRPN gene on its methylation pattern and expression.
RESULTS—Fluorescence in situ hybridisation (FISH) using probes within and flanking the Prader-Willi/Angelman syndrome critical region indicated that all patients carried an intrachromosomal triplication of proximal 15q11-q14 in one of the two chromosome 15 homologues (trip(15)). In all patients the orientation of the triplicated segments was normal-inverted-normal, suggesting that a common mechanism of rearrangement may have been involved. Microsatellite analysis showed the parental origin of the trip(15) to be maternal in three cases and paternal in one case. The paternal triplication patient had features similar to PWS, one maternal triplication patient had features similar to AS, and the other two maternal triplication patients had non-specific findings including hypotonia and mental retardation. Methylation analysis at exon 1 of the SNRPN locus showed increased dosage of either the paternal or maternal bands in the paternal or maternal triplication patients, respectively, suggesting that the methylation pattern shows a dose dependent increase that correlates with the parental origin of the triplication. In addition, the expression of SNRPN was analysed by northern blotting and expression levels were consistent with dosage and parental origin of the triplication.
CONCLUSIONS—These four additional cases of trip(15) will provide additional information towards understanding the phenotypic effects of this abnormality and aid in understanding the mechanism of formation of other chromosome 15 rearrangements.


Keywords: chromosome 15 triplication; Prader-Willi syndrome; Angelman syndrome; autism  相似文献   
15.
Recently it has been shown that most cases of the Miller-Dieker syndrome (MDS) are caused by deletion 17p13.3. All familial cases have been associated with a balanced reciprocal translocation in a carrier parent and unbalanced translocations in their affected offspring. We report a new case of familial MDS in whom the mother carries a pericentric inversion of chromosome 17. She has had two children with MDS, one of whom was shown to carry a recombinant 17 consisting of dup(17q) and del(17p). The high frequency of familial MDS and its consistent association with balanced chromosomal rearrangements in one of the parents makes it important to do high-resolution chromosome analysis on all patients with MDS and possibly all patients with lissencephaly. Finding a familial balanced rearrangement makes prenatal diagnosis of this condition feasible.  相似文献   
16.
BackgroundAlthough recent studies have shown an association between obesity and adverse coronavirus disease 2019 (COVID-19) patient outcomes, there is a paucity in large studies focusing on hospitalized patients. We aimed to analyze outcomes associated with obesity in a large cohort of hospitalized COVID-19 patients.MethodsWe performed a retrospective study at a tertiary care health system of adult patients with COVID-19 who were admitted between March 1 and April 30, 2020. Patients were stratified by body mass index (BMI) into obese (BMI ≥ 30 kg/m 2) and non-obese (BMI < 30 kg/m 2) cohorts. Primary outcomes were mortality, intensive care unit (ICU) admission, intubation, and 30-day readmission.ResultsA total of 1983 patients were included of whom 1031 (51.9%) had obesity and 952 (48.9%) did not have obesity. Patients with obesity were younger (P < 0.001), more likely to be female (P < 0.001) and African American (P < 0.001) compared to patients without obesity. Multivariable logistic models adjusting for differences in age, sex, race, medical comorbidities, and treatment modalities revealed no difference in 60-day mortality and 30-day readmission between obese and non-obese groups. In these models, patients with obesity had increased odds of ICU admission (adjusted OR, 1.37; 95% CI, 1.07?1.76; P = 0.012) and intubation (adjusted OR, 1.37; 95% CI, 1.04?1.80; P = 0.026).ConclusionsObesity in patients with COVID-19 is independently associated with increased risk for ICU admission and intubation. Recognizing that obesity impacts morbidity in this manner is crucial for appropriate management of COVID-19 patients.  相似文献   
17.

Health agencies call for the immediate mobilization of existing interventions in response to numerous child and family mental health concerns that have arisen as result of the COVID-19 pandemic. Answering this call, this pilot study describes the rapid, full-scale change from a primarily clinic-based Parent–Child Interaction Therapy (PCIT) model to a virtual service model (i.e., I-PCIT) in an academic and community-based program in Miami, Florida. First, we describe the virtual service training model our program developed and its implementation with 17 therapists (MAge?=?32.35, 88.2% female, 47.1% Hispanic) to enable our clinic to shift from providing virtual services to a small portion of the families served (29.1%) to all of the families served. Second, we examine the effect of I-PCIT on child and caregiver outcomes during the 2-month stay-at-home period between March 16, 2020, and May 16, 2020, in 86 families (MChildAge?=?4.75, 71% Hispanic). Due to the rapid nature of the current study, all active participants were transferred to virtual services, and therefore there was no comparison or control group, and outcomes represent the most recently available scores and not treatment completion. Results reveal that I-PCIT reduced child externalizing and internalizing problems and caregiver stress, and increased parenting skills and child compliance with medium to large effects even in the midst of the COVID-19 pandemic. Finally, the study examined components of our virtual service training model associated with the greatest improvements in child and caregiver outcomes. Preliminary findings revealed that locally and collaboratively developed strategies (e.g., online communities of practice, training videos and guides) had the strongest association with child and caregiver outcomes. Implications for virtual service delivery, implementation, and practice in the midst of the COVID-19 pandemic are discussed.

  相似文献   
18.
19.

Objectives

Implementation intentions are ‘IF-THEN’ plans that encourage goal-intended behaviour. This study was designed to test whether an intervention encouraging the formation of implementation intentions can reduce self-harm in the community.

Design

A randomized controlled design was used.

Methods

At pre-intervention, outcome variables (self-harm in both specified and unspecified critical situations and suicidality) and potential moderators of implementation intentions (goal intention, mental imagery, and exposure to self-harm) were measured using self-report questionnaires. The participants (N = 469, aged 18–66 years, 86.4% female, 6.8% male and 6.7% other) were then randomized to either an experimental (implementation intention) or control task. At three-months post-intervention, self-report questionnaires were used again to measure the outcome variables.

Results

There were no overall differences between the conditions at post-intervention. However, goal intention and mental imagery, but not exposure to self-harm, moderated the effects of condition on self-harm in specified critical situations. At high (mean + 1SD) levels of both goal intention and mental imagery, the experimental condition reported self-harming less frequently in the situations specified in their implementation intentions.

Conclusions

Implementation intentions therefore represent a useful intervention for reducing self-harm in specified critical situations for people in the community who wish to avoid self-harm and those who frequently experience self-harm and suicide related mental imagery.  相似文献   
20.
Using prospective data gathered from a sample of 323 college women over a 10-week academic quarter, the present study examined whether dissociation and posttraumatic symptomatology mediate or moderate sexual revictimization. Results indicated that posttraumatic symptomatology, but not dissociation, moderated the link between previous and subsequent sexual victimization. Neither posttraumatic symptomatology nor dissociation mediated revictimization.  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