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   57452篇
  免费   6665篇
  国内免费   1145篇
耳鼻咽喉   282篇
儿科学   1540篇
妇产科学   1123篇
基础医学   3832篇
口腔科学   1350篇
临床医学   7459篇
内科学   10832篇
皮肤病学   530篇
神经病学   3827篇
特种医学   1914篇
外国民族医学   1篇
外科学   5216篇
综合类   6805篇
现状与发展   8篇
一般理论   10篇
预防医学   9708篇
眼科学   965篇
药学   5073篇
  39篇
中国医学   778篇
肿瘤学   3970篇
  2024年   60篇
  2023年   1269篇
  2022年   1569篇
  2021年   2924篇
  2020年   3047篇
  2019年   2729篇
  2018年   2722篇
  2017年   2673篇
  2016年   2720篇
  2015年   2523篇
  2014年   4555篇
  2013年   5289篇
  2012年   3722篇
  2011年   3864篇
  2010年   2952篇
  2009年   2745篇
  2008年   2766篇
  2007年   2533篇
  2006年   2255篇
  2005年   1909篇
  2004年   1583篇
  2003年   1301篇
  2002年   1126篇
  2001年   978篇
  2000年   776篇
  1999年   647篇
  1998年   545篇
  1997年   458篇
  1996年   375篇
  1995年   368篇
  1994年   295篇
  1993年   282篇
  1992年   235篇
  1991年   191篇
  1990年   144篇
  1989年   149篇
  1988年   133篇
  1987年   110篇
  1986年   85篇
  1985年   124篇
  1984年   108篇
  1983年   57篇
  1982年   79篇
  1981年   64篇
  1980年   56篇
  1979年   39篇
  1978年   26篇
  1977年   27篇
  1976年   26篇
  1975年   13篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.

Objectives

The predictive value of frailty and comorbidity, in addition to more readily available information, is not widely studied. We determined the incremental predictive value of frailty and comorbidity for mortality and institutionalization across both short and long prediction periods in persons with dementia.

Design

Longitudinal clinical cohort study with a follow-up of institutionalization and mortality occurrence across 7 years after baseline.

Setting and Participants

331 newly diagnosed dementia patients, originating from 3 Alzheimer centers (Amsterdam, Maastricht, and Nijmegen) in the Netherlands, contributed to the Clinical Course of Cognition and Comorbidity (4C) Study.

Measures

We measured comorbidity burden using the Cumulative Illness Rating Scale for Geriatrics (CIRS-G) and constructed a Frailty Index (FI) based on 35 items. Time-to-death and time-to-institutionalization from dementia diagnosis onward were verified through linkage to the Dutch population registry.

Results

After 7 years, 131 patients were institutionalized and 160 patients had died. Compared with a previously developed prediction model for survival in dementia, our Cox regression model showed a significant improvement in model concordance (U) after the addition of baseline CIRS-G or FI when examining mortality across 3 years (FI: U = 0.178, P = .005, CIRS-G: U = 0.180, P = .012), but not for mortality across 6 years (FI: U = 0.068, P = .176, CIRS-G: U = 0.084, P = .119). In a competing risk regression model for time-to-institutionalization, baseline CIRS-G and FI did not improve the prediction across any of the periods.

Conclusions

Characteristics such as frailty and comorbidity change over time and therefore their predictive value is likely maximized in the short term. These results call for a shift in our approach to prognostic modeling for chronic diseases, focusing on yearly predictions rather than a single prediction across multiple years. Our findings underline the importance of considering possible fluctuations in predictors over time by performing regular longitudinal assessments in future studies as well as in clinical practice.  相似文献   
62.
This study aimed at deriving occupational thresholds of toxicological concern for inhalation exposure to systemically-acting organic chemicals using predicted internal doses. The latter were also used to evaluate the quantitative relationship between occupational exposure limit and internal dose. Three internal dose measures were identified for investigation: (i) the daily area under the venous blood concentration vs. time curve, (ii) the daily rate of the amount of parent chemical metabolized, and (iii) the maximum venous blood concentration at the end of an 8-hr work shift. A dataset of 276 organic chemicals with 8-hr threshold limit values-time-weighted average was compiled along with their molecular structure and Cramer classes (Class I: low toxicity, Class II: intermediate toxicity, Class III: suggestive of significant toxicity). Using a human physiologically-based pharmacokinetic model, the three identified dose metrics were predicted for an 8-hr occupational inhalation exposure to the threshold limit value for each chemical. Distributional analyses of the predicted dose metrics were performed to identify the percentile values corresponding to the occupational thresholds of toxicological concern. Also, simple linear regression analyses were performed to evaluate the relationship between the 8-hr threshold limit value and each of the predicted dose metrics, respectively. No threshold of toxicological concern could be derived for class II due to few chemicals. Based on the daily rate of the amount of parent chemical metabolized, the proposed internal dose-based occupational thresholds of toxicological concern were 5.61?×?10?2 and 9?×?10?4 mmol/d at the 10th percentile level for classes I and III, respectively, while they were 4.55?×?10?1 and 8.5?×?10?3 mmol/d at the 25th percentile level. Even though high and significant correlations were observed between the 8-hr threshold limit values and the predicted dose metrics, the one with the rate of the amount of chemical metabolized was remarkable regardless of the Cramer class (r2 = 0.81; n = 276). The proposed internal dose-based occupational thresholds of toxicological concern are potentially useful for screening-level assessments as well as prioritization within an integrated occupational risk assessment framework.  相似文献   
63.
目的 明确与恶性胰腺囊性肿瘤(PCN)相关的术前危险因素,建立准确的预测模型,并予以验证。方法 纳入2013年1月至2020年5月复旦大学附属华东医院经术后病理检查证实的114例PCN病例,分为模型组(n=80)和验证组(n=34)。回顾性分析模型组术前的临床资料并探索与恶性PCN相关的影响因素,建立PCN恶性风险预测模型,绘制受试者工作特征(ROC)曲线和校正曲线评价模型,最后基于验证组数据对模型进行临床验证。结果 单因素回归分析提示临床症状、CA19-9水平升高、中性粒细胞淋巴细胞比值(NLR)、淋巴细胞单核细胞比值(LMR)、肿瘤最大直径、胰管扩张和实性成分与恶性PCN显著相关,进一步行多因素回归分析确定了NLR≥2.146、CA19-9水平升高、胰管扩张是恶性PCN的独立预测因素。基于多因素回归分析结果建立恶性PCN预测模型,绘制模型的ROC曲线,计算AUC为0.921(95%CI 0.863~0.979),Youden指数最大时取得最佳临界预测值为0.203,此时相对应的特异度为83.3%,敏感度为92.9%,准确率为85%。同时校正曲线显示模型具有较好的拟合度,最后代入验证组数据显示模型预测准确率为82.4%,特异度81.2%,敏感度100%。结论 CA19-9水平升高、NLR升高以及胰管扩张是恶性PCN的高危因素,基于此建立的恶性胰腺囊性肿瘤的预测模型具有较好的准确率,可为今后的临床诊疗提供辅助参考。  相似文献   
64.
Ductal carcinoma in situ (DCIS) of the breast is a nonobligate precursor of invasive breast cancer, accounting for 20 % of screen-detected breast cancers. Little is known about the natural progression of DCIS because most patients undergo surgery upon diagnosis. Many DCIS patients are likely being overtreated, as it is believed that only around 50 % of DCIS will progress to invasive carcinoma. Robust prognostic markers for progression to invasive carcinoma are lacking. In the past, studies have investigated women who developed a recurrence after breast-conserving surgery (BCS) and compared them with those who did not. However, where there is no recurrence, the patient has probably been adequately treated. The present narrative review advocates a new research strategy, wherein only those patients with a recurrence are studied. Approximately half of the recurrences are invasive cancers, and half are DCIS. So-called “recurrences” are probably most often the result of residual disease. The new approach allows us to ask: why did some residual DCIS evolve to invasive cancers and others not? This novel strategy compares the group of patients that developed in situ recurrence with the group of patients that developed invasive recurrence after BCS. The differences between these groups could then be used to develop a robust risk stratification tool. This tool should estimate the risk of synchronous and metachronous invasive carcinoma when DCIS is diagnosed in a biopsy. Identification of DCIS patients at low risk for developing invasive carcinoma will individualize future therapy and prevent overtreatment.  相似文献   
65.
ABSTRACT

Introduction

Despite an increasingly older pulmonary hypertension (PH) population, data on PH treatments in these patients are limited because there exist no clinical studies dedicated to geriatric groups. Furthermore, elderly patients with comorbidities have been systematically excluded from clinical trials, limiting the evidence base for drugs approved for pulmonary arterial hypertension (PAH).  相似文献   
66.
ObjectivesTo identify factors associated with 30-day all-cause readmission rates in surgical patients discharged to skilled nursing facilities (SNFs), and derive and validate a risk score.DesignRetrospective cohort.Setting and participantsPatients admitted to 1 tertiary hospital's surgical services between January 1, 2011, and December 31, 2014 and subsequently discharged to 110 SNFs within a 25-mile radius of the hospital. The first 2 years were used for the derivation set and the last 2 for validation.MethodsData were collected on 30-day all cause readmissions, patient demographics, procedure and surgical service, comorbidities, laboratory tests, and prior health care utilization. Multivariate regression was used to identify risk factors for readmission.ResultsDuring the study period, 2405 surgical patients were discharged to 110 SNFs, and 519 (21.6%) of these patients experienced readmission within 30 days. In a multivariable regression model, hospital length of stay [odds ratio (OR) per day: 1.03, 95% confidence interval (CI) 1.02-1.04], number of hospitalizations in past year (OR 1.24 per hospitalization, 95% CI 1.18-1.31), nonelective surgery (OR 1.33, 95% CI 1.18-1.65), low-risk service (orthopedic/spine service) (OR 0.32, 95% CI 0.25-0.42), and intermediate-risk service (cardiothoracic surgery/urology/gynecology/ear, nose, throat) (OR 0.69, 95% CI 0.53-0.88) were associated with all-cause readmissions. The model had a C index of 0.71 in the validation set. Using the following risk score [0.8 × (hospital length of stay) + 7 × (number of hospitalizations in past year) +10 for nonelective surgery, +36 for high-risk surgery, and +20 for intermediate-risk surgery], a score of >40 identified patients at high risk of 30-day readmission (35.8% vs 12.6%, P < .001).Conclusions/ImplicationsAmong surgical patients discharged to an SNF, a simple risk score with 4 parameters can accurately predict the risk of 30-day readmission.  相似文献   
67.
《中国现代医生》2020,58(22):74-77
目的 探讨儿童慢性腹泻高营养风险情况及对预后的影响。方法 选择2019年1~12月在我院诊断治疗的慢性腹泻患儿100例为研究对象,进行营养风险筛查,分析高营养风险患儿与非高营养风险患儿临床特征以及预后情况,分析性别、年龄、病因对慢性腹泻患儿高营养风险的影响。结果 (1)100例患儿24例患儿STAMP评分≥4分,为高营养风险组,占24.0%。(2)7~14岁患儿高营养风险发生率显著高于其他年龄段患儿(P0.05);炎症性肠病患儿高营养风险发生率显著其他病因的患儿(P0.05)。(3)炎症性肠病是慢性腹泻患儿发生高营养风险的独立危险因素(P0.05)。(4)高营养风险组白蛋白、前白蛋白水平显著低于非高营养风险组,差异有统计学意义(P0.05)。两组Hb水平比较差异无统计学意义(P0.05)。(5)非高营养风险组痊愈率显著高于高营养风险组,医院感染率显著低于高营养风险组,住院时间显著短于高营养风险组,差异均有统计学意义(P0.05)。结论 儿童慢性腹泻高营养风险发生率相对较高,病因会影响患儿高营养风险的发生,而高营养风险影响患儿的预后,延长住院时间。  相似文献   
68.
目的:观察血府逐瘀汤合温胆汤加减联合西药治疗高血压颈动脉硬化的效果。方法:选取2017年6月至2018年6月聊城市中医院收治的高血压颈动脉硬化患者92例作为研究对象,按照随机数字表法随机分为对照组与观察组,每组46例。对照组患者给予左旋氨氯地平+阿托伐他汀口服,观察组在对照组基础上加用血府逐瘀汤合温胆汤加减口服。观察患者血压、血脂控制情况,测定颈动脉内膜中层厚度(IMT)、斑块面积、血管皮内皮功能、血清蛋白酶分子水平。结果:与对照组比较,观察组治疗后的血压SBP、DBP及血脂TG、TC、LDL-C等指标更低(P<0.05);颈动脉粥样硬化斑块IMT厚度、斑块面积明显缩小(P<0.05),血管内皮功能指标ET-1、AngⅡ、TXB2水平明显降低,NO水平明显升高(P<0.05);血清CatK、MMP-9水平明显降低(P<0.05);观察组不良反应发生率8.70%明显低于对照组不良反应发生率21.74%(P<0.05)。结论:血府逐瘀汤合温胆汤加减联合西药更利于控制高血压颈动脉硬化患者的血压,调节脂质代谢,改善血管内皮功能,降低血清蛋白酶分子的含量,用药安全。  相似文献   
69.
BackgroundImmune checkpoint inhibitors and vascular endothelial growth factor receptor (VEGFR) tyrosine kinase inhibitors are the most commonly used medications in metastatic renal cell carcinoma (mRCC). Recently, large clinical trials have shown favorable outcomes in patients treated with combined immune checkpoint plus VEGFR inhibition compared with VEGFR inhibition alone. However, the benefit among favorable risk (based on International Metastatic Renal Cell Carcinoma Database Consortium score) and elderly (age > 65 years) patients was not clear, leading to a discrepancy between United States Food and Drug Administration and European Association of Urology recommendations.Materials and MethodsWe searched available literature for phase III randomized clinical trials evaluating the efficacy of combining immunotherapy plus VEGF/VEGFR inhibitors versus standard of care in patients with previously untreated mRCC. Combinations that were included in United States Food and Drug Administration recommendations or European Association of Urology guidelines were used for analysis. We performed a meta-analysis with a random effects model to evaluate the efficacy of immunotherapy-VEGFR inhibitor combinations compared with sunitinib in favorable risk and elderly patients.ResultsOur analysis demonstrated that progression-free survival (PFS) was significantly prolonged with combination therapy compared with sunitinib in patients with age > 65 years (hazard ratio, 0.66; 95% confidence interval, 0.52-0.84; P = .001). The PFS in favorable risk disease was improved with combination therapy compared with sunitinib, but the difference was not statistically significant (hazard ratio, 0.68; 95% confidence interval, 0.46-1.01; P = .055).ConclusionOur meta-analysis strengthens the trend of beneficial effect in prolonging PFS in both subgroups compared with each trial alone, indicating that favorable risk and elderly patients with mRCC likely benefit from combining programmed cell death 1 or programmed cell death-ligand 1 and VEGFR inhibition.  相似文献   
70.
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