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   24069篇
  免费   2444篇
  国内免费   105篇
耳鼻咽喉   196篇
儿科学   912篇
妇产科学   652篇
基础医学   3422篇
口腔科学   371篇
临床医学   3468篇
内科学   5195篇
皮肤病学   575篇
神经病学   2503篇
特种医学   556篇
外国民族医学   4篇
外科学   2344篇
综合类   207篇
一般理论   5篇
预防医学   2419篇
眼科学   296篇
药学   1570篇
中国医学   21篇
肿瘤学   1902篇
  2023年   245篇
  2022年   382篇
  2021年   768篇
  2020年   607篇
  2019年   917篇
  2018年   1009篇
  2017年   789篇
  2016年   837篇
  2015年   887篇
  2014年   1068篇
  2013年   1456篇
  2012年   1851篇
  2011年   1758篇
  2010年   1125篇
  2009年   1002篇
  2008年   1501篇
  2007年   1489篇
  2006年   1376篇
  2005年   1290篇
  2004年   1217篇
  2003年   1082篇
  2002年   1005篇
  2001年   216篇
  2000年   197篇
  1999年   215篇
  1998年   240篇
  1997年   189篇
  1996年   148篇
  1995年   148篇
  1994年   128篇
  1993年   108篇
  1992年   83篇
  1991年   90篇
  1990年   87篇
  1989年   75篇
  1988年   66篇
  1987年   48篇
  1986年   64篇
  1985年   56篇
  1984年   61篇
  1983年   61篇
  1982年   69篇
  1981年   69篇
  1980年   41篇
  1979年   28篇
  1978年   35篇
  1977年   42篇
  1976年   50篇
  1975年   38篇
  1974年   38篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
951.
Background: Water disinfection by-products have been associated with an increased cancer risk. Micronuclei (MN) frequency in lymphocytes is a marker of genomic damage and can predict adult cancer risk.Objective: We evaluated maternal exposure to drinking water brominated trihalomethanes (BTHM) in relation to MN frequency in maternal and cord blood lymphocytes.Methods: MN frequency was examined in 214 mothers and 223 newborns from the Rhea mother–child cohort in Crete, Greece, in 2007–2008. Residential BTHM water concentrations were estimated during pregnancy using tap water analyses and modeling. Questionnaires on water related habits were used to estimate BTHM exposure from all routes. Associations between BTHM and MN frequency were estimated using negative binomial regression.Results: BTHM concentrations in residential tap water during pregnancy ranged from 0.06 to 7.1 μg/L. MN frequency in maternal binucleated lymphocytes was found to increase with BTHM concentrations in residential water for exposure during the first [rate ratio (RR) for 1 μg/L = 1.05; 95% CI: 1.00, 1.11] and second trimesters (RR for 1 μg/L = 1.03; 95% CI: 1.00, 1.06), and through all routes of BTHM exposure during the first trimester (RR for 1 μg/week = 3.14; 95% CI: 1.16, 8.50).Conclusions: These findings suggest that exposure to BTHM may increase the frequency of MN in maternal binucleated lymphocytes.Citation: Stayner LT, Pedersen M, Patelarou E, Decordier I, Vande Loock K, Chatzi L, Espinosa A, Fthenou E, Nieuwenhuijsen MJ, Gracia-Lavedan E, Stephanou EG, Kirsch-Volders M, Kogevinas M. 2014. Exposure to brominated trihalomethanes in water during pregnancy and micronuclei frequency in maternal and cord blood lymphocytes. Environ Health Perspect 122:100–106; http://dx.doi.org/10.1289/ehp.1206434  相似文献   
952.
Background: Understanding the potential links between extreme weather events and human health in India is important in the context of vulnerability and adaptation to climate change. Research exploring such linkages in India is sparse.Objectives: We evaluated the association between extreme precipitation and gastrointestinal (GI) illness-related hospital admissions in Chennai, India, from 2004 to 2007.Methods: Daily hospital admissions were extracted from two government hospitals in Chennai, India, and meteorological data were retrieved from the Chennai International Airport. We evaluated the association between extreme precipitation (≥ 90th percentile) and hospital admissions using generalized additive models. Both single-day and distributed lag models were explored over a 15-day period, controlling for apparent temperature, day of week, and long-term time trends. We used a stratified analysis to explore the association across age and season.Results: Extreme precipitation was consistently associated with GI-related hospital admissions. The cumulative summary of risk ratios estimated for a 15-day period corresponding to an extreme event (relative to no precipitation) was 1.60 (95% CI: 1.29, 1.98) among all ages, 2.72 (95% CI: 1.25, 5.92) among the young (≤ 5 years of age), and 1.62 (95% CI: 0.97, 2.70) among the old (≥ 65 years of age). The association was stronger during the pre-monsoon season (March–May), with a cumulative risk ratio of 6.50 (95% CI: 2.22, 19.04) for all ages combined compared with other seasons.Conclusions: Hospital admissions related to GI illness were positively associated with extreme precipitation in Chennai, India, with positive cumulative risk ratios for a 15-day period following an extreme event in all age groups. Projected changes in precipitation and extreme weather events suggest that climate change will have important implications for human health in India, where health disparities already exist.Citation: Bush KF, O’Neill MS, Li S, Mukherjee B, Hu H, Ghosh S, Balakrishnan K. 2014. Associations between extreme precipitation and gastrointestinal-related hospital admissions in Chennai, India. Environ Health Perspect 122:249–254; http://dx.doi.org/10.1289/ehp.1306807  相似文献   
953.
Background: Adapting to extreme heat is becoming more critical as our climate changes. Previous research reveals that very few communities in the United States have programs to sufficiently prevent health problems during hot weather.Objective: Our goal was to examine county-level local heat preparedness and response in 30 U.S. states following the unusually hot summer of 2011.Methods: Using a multimodal survey approach, we invited local health and emergency response departments from 586 counties to participate in the largest survey to date of heat preparedness and response in the United States. County-level responses were pooled into national and regional-level summaries. Logistic regressions modeled associations between heat planning/response and county characteristics, including population, poverty rates, typical summer weather, and 2011 summer weather.Results: Of 586 counties, 190 (32%) responded to the survey. Only 40% of these counties had existing heat plans. The most common heat responses were communication about heat, outreach, and collaborations with other organizations. Both heat preparedness and heat response were, on average, more extensive in counties with higher populations, lower poverty rates, and lower percentages of older people. Heat response was generally more extensive in counties with heat plans.Conclusions: Most responding counties were underprepared for extreme heat in 2011 and lacked a formal response plan. Because counties with heat plans were more likely to act to prevent adverse heat impacts to residents, local health departments should consider adopting such plans, especially because increased extreme heat is anticipated with further climate change.Citation: White-Newsome JL, Ekwurzel B, Baer-Schultz M, Ebi KL, O’Neill MS, Anderson GB. 2014. Survey of county-level heat preparedness and response to the 2011 summer heat in 30 U.S. States. Environ Health Perspect 122:573–579; http://dx.doi.org/10.1289/ehp.1306693  相似文献   
954.
ObjectiveTo assess the extent of arsenic contamination of groundwater and surface water in Peru and, to evaluate the accuracy of the Arsenic Econo-Quick (EQ) kit for measuring water arsenic concentrations in the field.MethodsWater samples were collected from 151 water sources in 12 districts of Peru, and arsenic concentrations were measured in the laboratory using inductively-coupled plasma mass spectrometry. The EQ field kit was validated by comparing a subset of 139 water samples analysed by laboratory measurements and the EQ kit.FindingsIn 86% (96/111) of the groundwater samples, arsenic exceeded the 10 µg/l arsenic concentration guideline given by the World Health Organization (WHO) for drinking water. In 56% (62/111) of the samples, it exceeded the Bangladeshi threshold of 50 µg/l; the mean concentration being 54.5 µg/l (range: 0.1–93.1). In the Juliaca and Caracoto districts, in 96% (27/28) of groundwater samples arsenic was above the WHO guideline; and in water samples collected from the section of the Rímac river running through Lima, all had arsenic concentrations exceeding the WHO limit. When validated against laboratory values, the EQ kit correctly identified arsenic contamination relative to the guideline in 95% (106/111) of groundwater and in 68% (19/28) of surface water samples.ConclusionIn several districts of Peru, drinking water shows widespread arsenic contamination, exceeding the WHO arsenic guideline. This poses a public health threat requiring further investigation and action. For groundwater samples, the EQ kit performed well relative to the WHO arsenic limit and therefore could provide a vital tool for water arsenic surveillance.  相似文献   
955.
This perspective paper explores the choice of psychotherapy for psilocybin-assisted psychotherapy for treatment-resistant depression. There is evidence to support the use of some psychotherapies in treating ‘treatment-resistant’ depression, and emerging evidence for the efficacy of psilocybin. The next step which is the focus of this paper is to identify psychotherapies that are both effective and congruent with the psilocybin experience. The evidence for the efficacy of the psychotherapies is drawn from a Cochrane review and the analysis of their congruence with the psilocybin experience is drawn from a qualitative meta-synthesis of the experience of psilocybin. The paper will examine whether three one-to-one psychotherapies identified as effective in the treatment of treatment-resistant depression are compatible with the psilocybin experience. Each psychotherapy will be examined in relation to its congruence with the qualitative evidence that suggests the choice of psychotherapy needs to give priority to the subjective experience, facilitate emotional processing, support connectedness with others, acceptance of the self as emotional and support change based on the person's insights into their relationships with others and the world in which they live. We conclude that interpersonal psychotherapy and intensive short-term dynamic psychotherapy align with that experience, although others are currently being trialled.  相似文献   
956.
Fragile X syndrome (FXS), due to mutations of the FMR1 gene, is the most common known inherited cause of developmental disability as well as the most common single‐gene risk factor for autism. Our goal was to examine variation in brain structure in FXS with topological data analysis (TDA), and to assess how such variation is associated with measures of IQ and autism‐related behaviors. To this end, we analyzed imaging and behavioral data from young boys (n = 52; aged 1.57–4.15 years) diagnosed with FXS. Application of topological methods to structural MRI data revealed two large subgroups within the study population. Comparison of these subgroups showed significant between‐subgroup neuroanatomical differences similar to those previously reported to distinguish children with FXS from typically developing controls (e.g., enlarged caudate). In addition to neuroanatomy, the groups showed significant differences in IQ and autism severity scores. These results suggest that despite arising from a single gene mutation, FXS may encompass two biologically, and clinically separable phenotypes. In addition, these findings underscore the potential of TDA as a powerful tool in the search for biological phenotypes of neuropsychiatric disorders. Hum Brain Mapp 35:4904–4915, 2014. © 2014 Wiley Periodicals, Inc.  相似文献   
957.
Theiler’s murine encephalomyelitis virus (TMEV) induces demyelination in susceptible strains of mice (SJL/J) through an immunopathological process that is mediated by CD4+ Th1 T cell. These T cells are chemoattracted to the central nervous system by chemokines. Hence, in this study, we focused on the production of the chemokine “interferon-gamma-inducible protein 10 kDa,” or IP-10/CXCL10, by cultured SJL/J mouse astrocytes infected with the BeAn strain of TMEV and its capacity to attract activated T cells. The analysis of the whole murine genome by DNA hybridization with cRNAs from mock- and TMEV-infected cultures revealed the upregulation of six sequences that potentially encode for CXCL10. This increased CXCL10 expression was validated by PCR and qPCR. The presence of this chemokine was further demonstrated by enzyme-linked immunoassay (ELISA). Significantly, astrocytes from BALB/c mice, a strain resistant to demyelination, did not produce CXCL10. The secreted CXCL10 was biologically active, inducing chemoattraction of activated lymphocytes. The inflammatory cytokines, IL-1α, IFN-γ, and TNF-α, were strong inducers of CXCL10 in astrocytes. Serum from TMEV-infected SJL/J but not BALB/c mice contains CXCL10, the levels of which peak at the onset of the clinical disease. Finally, this in vitro inflammation model was fully inhibited by 17β-estradiol and four selective estrogen receptor modulators, as demonstrated by ELISA and qPCR.  相似文献   
958.
959.
Drug delivery to the brain is influenced by the blood–brain barrier (BBB) and blood–tumor barrier (BTB) to an extent that is still debated in neuro-oncology. In this paper, we studied the delivery across the BTB and the BBB of compounds with different molecular sizes in normal and glioma-bearing rats. Studies were performed at baseline as well as after an osmotic BBB disruption (BBBD) using dynamic contrast-enhanced magnetic resonance imaging and two T1 contrast agents (CAs), Magnevist (743 Da) and Gadomer (17,000 Da). More specifically, we determined the time window for the BBB permeability, the distribution and we calculated the brain exposure to the CAs. A different pattern of accumulation and distribution at baseline as well as after a BBBD procedure was observed for both agents, which is consistent with their different molecular size and weight. Baseline tumor exposure was threefold higher for Magnevist compared with Gadomer, whereas postBBBD tumor exposure was twofold higher for Magnevist. Our study clearly showed that the time window and the extent of delivery across the intact, as well as permeabilized BTB and BBB are influenced by drug size.  相似文献   
960.

Background

Obesity is a growing epidemic in the USA, which leads to comorbidities associated with diseases such as hypertension, diabetes, sleep apnea, cardiovascular disease, osteoarthritis, cancer, gallbladder disease, and dyslipidemia. The purpose of this study is to identify perceptions of weight loss experience between African-American (AA) and Caucasian patients undergoing bariatric surgery.

Methods

A convenience sample of 31 patients participated in this study from May to June 2013. The sample size consisted of 16 AA and 15 Caucasians from two fully accredited and licensed bariatric clinics in metropolitan Detroit.

Results

The sample (N?=?31) consists of eligible AA and Caucasian presurgical bariatric patients on their first preoperative appointment. Snacking and sexual satisfaction showed a significant difference (p?<?0.05), lower amongst Caucasians than amongst the AA. The results revealed that salary within the AA population was significantly lower than that of the Caucasians, especially in the $26.000 to $36,000 category as well as in the over $40,000 category.

Conclusions

The discrepancy widened as the variables of snacks, sexual satisfaction, and salary revealed a significant difference for Caucasians than AA. It is prudent that health-care providers become part of the obesity management solution by examining these variables when planning weight loss interventions.  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