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   799篇
  免费   65篇
耳鼻咽喉   2篇
儿科学   15篇
妇产科学   48篇
基础医学   118篇
口腔科学   5篇
临床医学   108篇
内科学   153篇
皮肤病学   15篇
神经病学   90篇
特种医学   23篇
外科学   60篇
综合类   7篇
预防医学   84篇
眼科学   9篇
药学   57篇
中国医学   1篇
肿瘤学   69篇
  2024年   2篇
  2023年   11篇
  2022年   34篇
  2021年   30篇
  2020年   24篇
  2019年   24篇
  2018年   25篇
  2017年   23篇
  2016年   24篇
  2015年   18篇
  2014年   40篇
  2013年   53篇
  2012年   55篇
  2011年   70篇
  2010年   38篇
  2009年   38篇
  2008年   38篇
  2007年   50篇
  2006年   51篇
  2005年   39篇
  2004年   47篇
  2003年   38篇
  2002年   39篇
  2001年   2篇
  2000年   4篇
  1999年   6篇
  1998年   3篇
  1997年   10篇
  1996年   3篇
  1995年   1篇
  1994年   1篇
  1993年   2篇
  1992年   1篇
  1991年   2篇
  1990年   5篇
  1989年   3篇
  1988年   1篇
  1982年   1篇
  1979年   1篇
  1976年   5篇
  1975年   1篇
  1973年   1篇
排序方式: 共有864条查询结果,搜索用时 14 毫秒
91.
Mucopolysaccharidoses (MPS) form a group of inherited metabolic disorders characterized by intralysosomal storage of glycosaminoglycans. This study aimed to investigate the path followed by Brazilian patients from birth to diagnosis. An interview was conducted with patient's parents or guardians with subsequent review of patient's medical records. One hundred thirteen patients with MPS were included (MPS I: 18, MPS II: 43, MPS IIIA: 2, MPS IIIB: 3, MPS IIIC: 1, MPS IVA: 15, MPS IVB: 1, MPS VI: 29, MPS VII: 1) from 97 families. Median age at the onset of signs/symptoms was 18 months (MPS I: 18, MPS II: 24, MPS IVA: 8, MPS VI: 8). Skeletal abnormalities (for MPS IVA and MPS VI), joint contractures (for MPS II), and typical facial features (for MPS I) were the most frequently reported first signs/symptoms. Several health professionals were involved in patient's care as of the onset of symptoms until biochemical diagnosis was established. Median age at diagnosis was 76 months (MPS I: 75, MPS II: 95, MPS IVA: 75, MPS VI: 52). Considering the group as a whole, there was a 4.8-year delay between the onset of signs/symptoms and the establishment of the diagnosis. Considering that specific therapies are available for some of these disorders and that early treatment is likely to change more favorably the natural history of the disease, efforts should be made to minimize this delay. We believe that this situation can be improved by measures that both increase awareness of health professionals about MPS and improve access to diagnostic tests.  相似文献   
92.
93.

Objective

The present study used an empirically based method to characterize substance use in a sample of Argentinean adolescents and analyzed the association between age at drinking onset and substance use behaviors. Differences in alcohol expectancies and personality traits as a function of different patterns of substance use were also explored.

Method

Data were obtained from 583 adolescents aged 13–18 years (M = 15.01 years; SD = 1.5 years; 59.5% female) from the city of Cordoba, Argentina. Alcohol, tobacco, and drug use and age at first alcohol use were measured. Personality traits, including extroversion, conscientiousness, impulsivity, and aggression, and positive and negative alcohol expectancies were assessed. Latent Class Analysis was applied to examine the structure of five co-occurring substance use behaviors: frequency of alcohol use, quantity of alcohol use, prevalence of drunkenness episodes, tobacco use, and drug use.

Results

Latent Class Analysis revealed five distinct patterns of substance use. The classes differed in substance use behaviors, personality traits, and alcohol expectancies. Adolescents with early drinking onset were more likely to show heavier alcohol use, more drunkenness episodes, and more drug use than adolescents with late drinking onset.

Conclusions

Latent Class Analysis allowed the detection of groups of adolescents with distinct patterns of substance use. These groups exhibited significantly different personality and alcohol expectancy profiles, likely representing subgroups who are at greater risk for developing alcohol-related problems.  相似文献   
94.

Background

Illicit substances increase risk of morbidity and mortality and have significant consequences for society. Personality traits are associated with drug use; we test whether these associations vary by socioeconomic status.

Method

Participants (N = 412) from the Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS) study completed the Revised NEO Personality Inventory and self-reported use of opiates and cocaine. 50% of participants were living below 125% of the federal poverty line. Mean-level personality differences across never, former, and current opiate/cocaine users were compared. Logistic regressions compared never versus current users and interactions between personality traits and poverty status tested whether these associations varied by socioeconomic status.

Results

High Neuroticism and low Agreeableness increased risk of drug use. The association between low Conscientiousness and drug use was moderated by poverty, such that low Conscientiousness was a stronger risk factor for illicit substance use among those with relatively higher SES. For every standard deviation decrease in Conscientiousness, there was a greater than 2-fold increase in risk of illicit substance use (OR = 2.15, 95% CI = 1.45–3.17). Conscientiousness was unrelated to drug use among participants living below 125% of the federal poverty line.

Conclusions

Under favorable economic conditions, the tendency to be organized, disciplined, and deliberate is protective against drug use. These tendencies, however, matter less when financial resources are scarce. In contrast, those prone to emotional distress and antagonism are at greater risk for current drug use, regardless of their economic situation.  相似文献   
95.
Organogenesis and somatic embryogenesis were achieved in cotyledon cultures of Frangula alnus Mill. (alder buckthorn) and Rhamnus catharticus L. (common buckthorn), and in zygotic embryo cultures of F. alnus. Histological examination of cotyledonary segment cultures revealed that adventitious buds and somatic embryos arose indirectly through an intervening callus phase. In comparison to zygotic embryos, embriogenic callus of Frangula alnus contained significantly more anthraquinones in the form of free aglycones and different participation of chrysophanol and physcion within synthesized complex of metabolites. Also, in comparison to shoots, root cultures and in particular undifferentiated callus of Frangula alnus, embryogenic callus contained more chysophanol and aloe emodin and less physcion derivatives. Production of physcion derivatives was significantly increased in embryogenic calluses of R. catharticus compared to zygotic embryos. On the other hand, the emodin content was lower than in zygotic embryos. In comparison to shoot, root cultures and in particular undifferentiated callus of common buckthorn, embryogenic callus contained significantly more derivatives of physcion and emodin. The content of chrysophanol and its derivatives was decreased proportionally.  相似文献   
96.
Pili of gram-positive bacteria are key virulence factors and their subunits are considered excellent vaccine candidates. Streptococcus suis is an emerging zoonotic agent that can cause epidemics of life-threatening infections in humans, but the functional role or immunoprotective potential of its pilus components have not been studied yet. Using a selective proteomics approach, we have identified a surface protein of serotype 2 S. suis showing features of an ancillary pilus subunit, as evidenced by bioinformatics analysis, immunoblot and immunoelectron microscopy. Immunization with recombinant fragments of this protein, designated herein as PAPI-2b, markedly protected mice from systemic S. suis infection.  相似文献   
97.

Objective

To examine changes in personality in individuals with mild cognitive impairment (MCI) or dementia as observed by family members using both new data and a meta-analysis with the published literature.

Design

Current and retrospective personality assessments of individuals with dementia by family informants. PubMed was searched for studies with a similar design and a forward citation tracking was conducted using Google Scholar in June 2018. Results from a new sample and from published studies were combined in a random effect meta-analysis.

Setting and participants

Family members of older adults with MCI or dementia.

Measures

The 5 major dimensions (neuroticism, extraversion, openness, agreeableness, and conscientiousness) and facets of personality were assessed with NEO Personality Inventory questionnaires.

Results

The new sample (n = 50) and meta-analysis (18 samples; n = 542) found consistent shifts in personality from the premorbid to current state in patients with cognitive impairment. The largest changes (>1 standard deviation) were declines in conscientiousness (particularly for the facets of self-discipline and competence) and extraversion (decreased energy and assertiveness), as well as increases in neuroticism (increased vulnerability to stress). The new sample suggested that personality changes were larger in individuals taking cognition-enhancing medications (cholinesterase inhibitors or memantine). More recent studies and those that examined individuals with MCI found smaller effects.

Conclusions and implications

Consistent with the clinical criteria for the diagnosis of dementia, the new study and meta-analysis found replicable evidence for large changes in personality among individuals with dementia. Future research should examine whether there are different patterns of personality changes across etiologies of dementia to inform differential diagnosis and treatments. Prospective, repeated assessments of personality using both self- and informant-reports are essential to clarify the temporal evolution of personality change across the preclinical, prodromal, and clinical phases of dementia.  相似文献   
98.
  相似文献   
99.
Lazaro A 《PharmacoEconomics》2002,20(14):943-961
Despite the theoretical arguments presented in the literature regarding discounting over the last 25 years, no satisfactory reply has yet been offered to the question of whether health consequences have to be discounted at the same rate as monetary consequences in the economic evaluation of health programmes or interventions designed to improve health. Against this background, the main objective of this paper was to review and systemise these theoretical arguments, with the aim of determining whether any of the positions identified can be accepted without reservation. Having determined that this is not possible, we investigated the rationality of discounting in the literature and, on this basis, propose a potential way to resolve the problem. Thus, we argue that the relationship between the discount of monetary and health consequences has to be determined in an indirect manner, by reference to the relationship maintained by the individual time preference rates for health and money in the context of private and social choice. Although this proposal moves the debate into the empirical field, its advantages must be weighed against the difficulties associated with the estimation of the time preferences.  相似文献   
100.
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