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   14751篇
  免费   1857篇
  国内免费   159篇
耳鼻咽喉   46篇
儿科学   578篇
妇产科学   844篇
基础医学   623篇
口腔科学   74篇
临床医学   1162篇
内科学   4717篇
皮肤病学   59篇
神经病学   730篇
特种医学   97篇
外国民族医学   1篇
外科学   2239篇
综合类   803篇
一般理论   1篇
预防医学   2803篇
眼科学   27篇
药学   466篇
中国医学   30篇
肿瘤学   1467篇
  2024年   23篇
  2023年   430篇
  2022年   546篇
  2021年   1073篇
  2020年   821篇
  2019年   862篇
  2018年   800篇
  2017年   676篇
  2016年   700篇
  2015年   666篇
  2014年   972篇
  2013年   1254篇
  2012年   631篇
  2011年   713篇
  2010年   524篇
  2009年   593篇
  2008年   629篇
  2007年   606篇
  2006年   577篇
  2005年   444篇
  2004年   423篇
  2003年   342篇
  2002年   287篇
  2001年   247篇
  2000年   182篇
  1999年   165篇
  1998年   165篇
  1997年   156篇
  1996年   142篇
  1995年   125篇
  1994年   117篇
  1993年   112篇
  1992年   99篇
  1991年   77篇
  1990年   72篇
  1989年   60篇
  1988年   72篇
  1987年   55篇
  1986年   71篇
  1985年   64篇
  1984年   50篇
  1983年   32篇
  1982年   27篇
  1981年   17篇
  1980年   9篇
  1979年   18篇
  1978年   10篇
  1976年   7篇
  1974年   5篇
  1971年   4篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
A low intake of selenium is associated with increased cardiovascular mortality. This could be reduced by supplementation with selenium and coenzyme Q10. D-dimer, a fragment of fibrin mirroring fibrinolysis, is a biomarker of thromboembolism, increased inflammation, endothelial dysfunction and is associated with cardiovascular mortality in ischemic heart disease. The objective was to examine the impact of selenium and coenzyme Q10 on the level of D-dimer, and its relationship to cardiovascular mortality. D-dimer was measured in 213 individuals at the start and after 48 months of a randomised double-blind placebo-controlled trial with selenium yeast (200 µg/day) and coenzyme Q10 (200 mg/day) (n = 106) or placebo (n = 107). The follow-up time was 4.9 years. All included individuals were low in selenium (mean 67 μg/L, SD 16.8). The differences in D-dimer concentration were evaluated by the use of T-tests, repeated measures of variance and ANCOVA analyses. At the end, a significantly lower D-dimer concentration was observed in the active treatment group in comparison with those on placebo (p = 0.006). Although D-dimer values at baseline were weakly associated with high-sensitive CRP, while being more strongly associated with soluble tumour necrosis factor receptor 1 and sP-selectin, controlling for these in the analysis there was an independent effect on D-dimer. In participants with a D-dimer level above median at baseline, the supplementation resulted in significantly lower cardiovascular mortality compared to those on placebo (p = 0.014). All results were validated with a persisting significant difference between the two groups. Therefore, supplementation with selenium and coenzyme Q10 in a group of elderly low in selenium and coenzyme Q10 prevented an increase in D-dimer and reduced the risk of cardiovascular mortality in comparison with the placebo group. The obtained results also illustrate important associations between inflammation, endothelial function and cardiovascular risk.  相似文献   
92.
Good nutritional support is crucial for the immune system to fight against coronavirus disease 2019 (COVID-19). However, in the context of a pandemic with a highly transmissible coronavirus, implementation of nutrition practice may be difficult. A multicenter electronic survey involving 62 dieticians was conducted, in order to understand barriers associated with dieticians’ adherence to nutrition guidelines for hospitalized COVID-19 patients in Indonesia. 69% of dieticians felt under stress when performing nutrition care, and 90% took supplements to boost their own immunity against the coronavirus. The concerns related to clinical practice included a lack of clear guidelines (74%), a lack of access to medical records (55%), inadequate experience or knowledge (48%), and a lack of self-efficacy/confidence (29%) in performing nutritional care. Half (52%) of the dieticians had performed nutrition education/counseling, 47% had monitored a patient’s body weight, and 76% had monitored a patient’s dietary intake. An adjusted linear regression showed that guideline adherence independently predicted the dieticians’ nutrition care behaviors of nutrition counselling (ß: 0.24 (0.002, 0.08); p = 0.04), and monitoring of body weight (ß: 0.43 (0.04, 0.11); p = 0.001) and dietary intake (ß: 0.47(0.03, 0.10); p = 0.001) of COVID-19 patients. Overall, adherence to COVID-19 nutrition guidelines is associated with better nutritional management behaviors in hospitalized COVID-19 patients.  相似文献   
93.
目的通过石灰水对埃及伊蚊生活史幼期不同阶段生长发育影响的实验室研究,评价生石灰对防治埃及伊蚊的干预效果,为生石灰用于埃及伊蚊的防治提供实验数据。方法将一定数量的埃及伊蚊依据不同发育阶段(卵、Ⅰ~Ⅳ龄期蚊幼、蛹)分别饲养于石灰水中,观察蚊幼活动情况,记录不同时期相应孵化时间、孵化率和死亡率,同时将实验室过夜自来水(实验室脱氯水)饲养蚊虫作对照,分析比较不同饲养环境、不同发育阶段埃及伊蚊发育的变化差异。结果对照组埃及伊蚊卵的平均孵化时间为1.75 d,而试验组(1.3 g/L石灰水饲养)埃及伊蚊卵的平均孵化时间为3.84 d,是对照组的2.19倍,孵化时间的差异具有统计学意义(t=36.02,P<0.05)。试验组埃及伊蚊卵孵化率为59.3%,对照组为89.3%,两组之间孵化率的差异具有统计学意义(χ^(2)=35.38,P<0.05)。Ⅰ~Ⅳ龄试验组蚊幼死亡率分别为44.0%、92.0%、97.3%、98.7%,显著高于对照组蚊幼死亡率,两组之间死亡率的差异具有统计学意义(χ^(2)值为65.79~276.53,P<0.05)。试验组蛹的死亡率为98.7%,显著高于对照组的死亡率,两组之间死亡率的差异具有统计学意义(χ^(2)=280.35,P<0.05)。对照组埃及伊蚊卵、蚊幼和蛹的死亡率分别为10.7%、2.3%和2.0%,三组之间死亡率的差异具有统计学意义(χ^(2)=25.09,P<0.05)。对照组埃及伊蚊卵的死亡率明显高于蚊幼和蛹。试验组埃及伊蚊卵、蚊幼和蛹的死亡率分别为40.7%、83.0%和98.7%,三组之间死亡率差异具有统计学意义(χ^(2)=170.88,P<0.05)。结论石灰水对埃及伊蚊不同发育阶段均具有明显抑制作用,对蛹的杀灭作用最大,其次是蚊幼和卵。随着埃及伊蚊幼虫年龄的增长,石灰水对其抑制效果逐渐增强。但生石灰对埃及伊蚊成蚊的防治效果有待进一步的现场验证。  相似文献   
94.
BackgroundHyderabad, Pakistan, was the first city to witness an outbreak of extensively drug resistant (XDR) typhoid fever. The outbreak strain is resistant to ampicillin, chloramphenicol, trimethoprim-sulfamethoxazole, fluoroquinolones, and third-generation cephalosporin, thus greatly limiting treatment options. However, despite over 5000 documented cases, information on mortality and morbidity has been limited.ObjectiveTo address the existing knowledge gap, this study aimed to assess the morbidity and mortality associated with XDR and non-XDR Salmonella serovar Typhi infections in Pakistan.MethodsWe reviewed the medical records of culture-confirmed typhoid cases in 5 hospitals in Hyderabad from October 1, 2016, to September 30, 2018. We recorded data on age, gender, onset of fever, physical examination, serological and microbiological test results, treatment before and during hospitalization, duration of hospitalization, complications, and deaths.ResultsA total of 1452 culture-confirmed typhoid cases, including 947 (66%) XDR typhoid cases and 505 (34%) non-XDR typhoid cases, were identified. Overall, ≥1 complications were reported in 360 (38%) patients with XDR typhoid and 89 (18%) patients with non-XDR typhoid (P<.001). Ileal perforation was the most commonly reported complication in both patients with XDR typhoid (n=210, 23%) and patients with non-XDR typhoid (n=71, 14%) (P<.001). Overall, mortality was documented among 17 (1.8%) patients with XDR S Typhi infections and 3 (0.6%) patients with non-XDR S Typhi infections (P=.06).ConclusionsAs this first XDR typhoid outbreak continues to spread, the increased duration of illness before hospitalization and increased rate of complications have important implications for clinical care and medical costs and heighten the importance of prevention and control measures.  相似文献   
95.
ObjectiveTo describe nursing home residents’ (NHRs) functional trajectories and mortality after a transfer to the emergency department (ED).DesignCase-control observational multicenter study.Setting and ParticipantsIn total, 1037 NHRs presenting to 17 EDs in France over 4 nonconsecutive weeks in 2016.MethodsFinite mixture models were fitted to longitudinal data on activities of daily living (ADL) scores before transfer (time 1), during hospitalization (time 2), and within 1 week after discharge (time 3) to identify groups of NHRs following similar functional evolution. Factors associated with mortality were investigated by Cox regressions.ResultsTrajectory modeling identified 4 distinct trajectories of ADL. The first showed a high and stable (across time 1, time 2, and time 3) functional capacity around 5.2/6 ADL points, with breathlessness as the main condition leading to transfer. The second displayed an initial 37.8% decrease in baseline ADL performance (between time 1 and time 2), followed by a 12.5% recovery of baseline ADL performance (time 2?time 3), with fractures as the main condition. The third displayed a similar initial decrease, followed by a 6.7% recovery. The fourth displayed an initial 70.1% decrease, followed by an 8.5% recover, with more complex geriatric polypathology situations. Functional decline was more likely after being transferred for a cerebrovascular condition or for a fracture, after being discharged from ED to a surgery department, and with a heavier burden of distressing symptoms during transfer. Mortality after ED transfer was more likely in older NHRs, those in a more severe condition, those who were hospitalized more frequently in the past month, and those transferred for cerebrovascular conditions or breathlessness.Conclusions and ImplicationsIdentified trajectories and factors associated with functional decline and mortality should help clinicians decide whether to transfer NHRs to ED. NHRs with high functional ability seem to benefit from ED transfers whereas on-site alternatives should be sought for those with poor functional ability.  相似文献   
96.
ObjectivesTo evaluate a machine learning model designed to predict mortality for Medicare beneficiaries aged >65 years treated for hip fracture in Inpatient Rehabilitation Facilities (IRFs).DesignRetrospective design/cohort analysis of Centers for Medicare & Medicaid Services Inpatient Rehabilitation Facility–Patient Assessment Instrument data.Setting and ParticipantsA total of 17,140 persons admitted to Medicare-certified IRFs in 2015 following hospitalization for hip fracture.MeasuresPatient characteristics include sociodemographic (age, gender, race, and social support) and clinical factors (functional status at admission, chronic conditions) and IRF length of stay. Outcomes were 30-day and 1-year all-cause mortality. We trained and evaluated 2 classification models, logistic regression and a multilayer perceptron (MLP), to predict the probability of 30-day and 1-year mortality and evaluated the calibration, discrimination, and precision of the models.ResultsFor 30-day mortality, MLP performed well [acc = 0.74, area under the receiver operating characteristic curve (AUROC) = 0.76, avg prec = 0.10, slope = 1.14] as did logistic regression (acc = 0.78, AUROC = 0.76, avg prec = 0.09, slope = 1.20). For 1-year mortality, the performances were similar for both MLP (acc = 0.68, AUROC = 0.75, avg prec = 0.32, slope = 0.96) and logistic regression (acc = 0.68, AUROC = 0.75, avg prec = 0.32, slope = 0.95).Conclusion and ImplicationsA scoring system based on logistic regression may be more feasible to run in current electronic medical records. But MLP models may reduce cognitive burden and increase ability to calibrate to local data, yielding clinical specificity in mortality prediction so that palliative care resources may be allocated more effectively.  相似文献   
97.
ObjectivesTo evaluate the effect of Hospital Admission Risk Program (HARP) on unplanned hospitalization, bed days, and mortality of enrolled individuals and to evaluate the cost-effectiveness of HARP.DesignA retrospective longitudinal analysis of hospital administrative data.InterventionIndividuals at risk of hospitalization were provided with multidisciplinary, community-based care support managed by care coordinators including integrated care planning, education, monitoring, service linkages, and general practitioner liaison over 6-9 months.Setting and ParticipantsIndividuals who were enrolled into 1 of 8 HARP chronic disease management programs between July 1, 2017, and June 30, 2018, at the Royal Melbourne Hospital, Australia.MethodsHospital admissions between 18 months before and 18 months after HARP enrollment were analyzed. Total hospital costs were compared between 18 months before and 12 months after HARP enrollment.ResultsA total of 1553 individuals with a median age of 71 years (interquartile range 60-81), 63.4% males, were admitted to HARP. Both unplanned hospitalizations and bed days were reduced during the HARP intervention compared to within 3 months before enrollment in each of the HARP management programs. After the HARP intervention, cardiac coach, cardiac heart failure, chronic respiratory, diabetes comanagement, and medication management programs had higher hospitalizations and bed days than individuals’ baseline of at least 3 months before HARP enrollment. Individuals in cardiac heart failure and chronic respiratory management programs had a higher mortality rate than other HARP chronic disease management programs. Individuals in cardiac coach, diabetes comanagement, and medication management programs had lower hospital costs during the HARP intervention compared to within 3 months before HARP enrollment.Conclusions and ImplicationsHARP reduced unplanned hospitalization and bed days but did not return individuals’ hospital use to baseline before the intervention. The variations in mortality between HARP chronic disease management programs implies that condition-specific goals between programs is preferable.  相似文献   
98.
目的通过对北京市5年先天性脑积水(CH)监测资料分析,了解北京市胎儿及婴儿的CH发生率、诊断及转归。 方法选择2015年1月至2019年12月,北京市出生缺陷监测系统内监测对象(胎龄为13周至生后1岁)中,407例CH患儿(胎儿或婴儿)为研究对象。对其出生缺陷诊断资料进行分析。采用χ2检验,对孤立性与非孤立性CH活产儿婴儿期存活率进行统计学比较。本研究遵循的程序符合2013年新修订的《世界医学协会赫尔辛基宣言》要求。 结果本研究时间(5年)内,北京市胎儿及1岁内婴儿的CH发生率为3.60×10-4(407/1 129 861)。这407例CH患儿中,82例(20.15%)合并颅外畸形,20例(4.91%)合并染色体异常;CH胎儿的产前诊断率为92.38%(376/407),超声检出CH胎儿时,其胎龄为24周(23~35周),其中胎龄≥28周者占26.06%(98/376)。376例产前被诊断的CH胎儿中,44例采取产前胎儿超声联合MRI检查,而且通过胎儿MRI检查对4例胎儿的颅内畸形具体类型进行了补充诊断。本研究未发现CH患儿的孕母合并宫内感染;103例CH活产儿中,73例孤立性CH患儿的婴儿期(1岁内)存活率为72.6%(53/73),高于30例非孤立性CH患儿的婴儿期存活率(60.0%,18/30),二者比较,差异无统计学意义(P>0.05)。 结论北京市在预防出生缺陷发生的三级防控体系中,对CH胎儿与婴儿的一级、二级防控已取得效果。对孕妇全孕期多次动态胎儿超声检查,必要时联合胎儿MRI检查,对非孤立性CH胎儿同时采取细胞遗传学和分子遗传学检测,可进一步提高CH患儿的防控效果。  相似文献   
99.
目的分析2015年四川省上消化道恶性肿瘤(胃癌和食管癌)发病、死亡和潜在减寿情况。方法收集四川省24个肿瘤登记处上报的2015年恶性肿瘤发病、死亡及人口资料。提取ICD-10编码C15-C16选择食管癌、胃癌的发病和死亡数据,用SAS 9.3软件分别计算性别、年龄别发病和死亡的粗率、标化率、构成比、累积率(0~74岁)、潜在减寿年数(potential years of life lost,PYLL)、潜在减寿率(potential years of life lost rate,PYLLR)和平均减寿年(average years of life lost,AYLL)。标准人口采用2000年全国普查人口年龄构成和Segi’s世界人口年龄构成。结果2015年四川省肿瘤登记地区食管癌和胃癌发病率分别为29.29/10万和28.60/10万,分别居发病第3位和第4位;胃癌和食管癌死亡率分别为23.90/10万和22.20/10万,分别居死亡第3位和第4位;根据上消化道恶性肿瘤发病率和死亡率的年龄性别分布,男女性45岁后发病率和50岁后死亡率均显著升高;无论城乡,男性食管癌和胃癌各项发病和死亡指标均高于女性。农村地区人群食管癌和胃癌疾病负担高于城市。食管癌潜在减寿年数为23399人年,平均减寿年数为15.41年,减寿率为1.92‰;胃癌潜在减寿年数为25390人年,平均减寿年数为16.74年,减寿率为2.09‰。结论四川省食管癌和胃癌发病与死亡水平相对较高,男性为食管癌和胃癌的高发人群,45岁以上的中老人群是上消化道恶性肿瘤高风险人群,农村地区人群的上消化道肿瘤疾病负担高于城市。  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