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   27520篇
  免费   2935篇
  国内免费   2144篇
耳鼻咽喉   277篇
儿科学   291篇
妇产科学   237篇
基础医学   2823篇
口腔科学   392篇
临床医学   3482篇
内科学   3533篇
皮肤病学   291篇
神经病学   1603篇
特种医学   1088篇
外国民族医学   7篇
外科学   2834篇
综合类   5885篇
现状与发展   8篇
一般理论   1篇
预防医学   2227篇
眼科学   603篇
药学   3127篇
  21篇
中国医学   1780篇
肿瘤学   2089篇
  2025年   7篇
  2024年   475篇
  2023年   594篇
  2022年   1266篇
  2021年   1449篇
  2020年   1157篇
  2019年   943篇
  2018年   940篇
  2017年   910篇
  2016年   807篇
  2015年   1214篇
  2014年   1615篇
  2013年   1557篇
  2012年   2133篇
  2011年   2316篇
  2010年   1744篇
  2009年   1397篇
  2008年   1569篇
  2007年   1577篇
  2006年   1521篇
  2005年   1283篇
  2004年   994篇
  2003年   1114篇
  2002年   892篇
  2001年   688篇
  2000年   617篇
  1999年   446篇
  1998年   285篇
  1997年   229篇
  1996年   158篇
  1995年   139篇
  1994年   124篇
  1993年   75篇
  1992年   57篇
  1991年   67篇
  1990年   53篇
  1989年   50篇
  1988年   41篇
  1987年   25篇
  1986年   27篇
  1985年   18篇
  1984年   17篇
  1983年   3篇
  1982年   1篇
  1981年   4篇
  1980年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
[目的]了解中国2010年上海世博会(简称“上海世博会”)园区内伤害流行病学特征。[方法]利用“中国2010年上海世界博览会园区内就诊异常情况监测和报告系统”(后称“就诊监测报告系统”),观察上海世博会园区内伤害病例,对其伤害原因、伤害性质等流行病学特征进行调查分析。[结果]从2010年5月1日至10月31日,伤害监测系统共收集12505例伤害病例。5月份游客伤害发生率最高(月均3.01/万),在世博局采取健康宣教以及改善园区内设施等一系列干预措施后,游客伤害发生率逐步下降,从5月初的4.50/万降低到最后一周的0.80/万。伤害分别是≥65岁和0~14岁游客的第1和第3位就诊原因。游客的主要伤害原因是跌倒和坠落。但是园区内最主要的伤害性质是挫伤和擦伤。[结论]上海世博会园区内伤害发生特征表明,在大型活动中,及时进行健康干预能有效地降低伤害的发生。  相似文献   
92.
BackgroundRadical nephroureterectomy (RNU) is the principal method for treatment of high-risk upper urinary tract urothelial carcinoma (UTUC). The transperitoneal approach is associated with poor disease progression, but the distal ureter-bladder cuff (DUBC) resection through retroperitoneal laparoscopic approach is difficult. This study proposed a modulated RNU technique, namely, total retroperitoneal laparoscopic radical nephroureterectomy (tRLRNU), with its advantages of DUBC resection and requiring fewer trocars etc. The efficiency, safety, and short-term impacts were retrospectively compared with total transperitoneal laparoscopic radical nephroureterectomy (tTLRNU).MethodsTotal of 12 patients who received tRLRNU and 28 patients who received tTLRNU were enrolled. The choice of surgical approach was random and their data were retrospectively analyzed. During tRLRNU, the laparoscope was versed towards the caudal direction and a retroperitoneal laparoscopic ureterectomy was performed. The bladder cuff was entirely transected and the bladder incision was sutured. The tRLRNU cases were compared with the tTLRNU cases in terms of general clinical data, pathologic parameters, peri-operative parameters, adjuvant therapy, and short-term outcomes. The independent samples t-tests, chi-square tests, and Fischer exact tests were used to analyze the differences.ResultsThere were no significant differences in the basic patient characteristics between the 2 groups. The data were comparable. There were significantly fewer trocars utilized in tRLRNU group compared to tTLRNU group (P=0.0008). tRLRNU group experienced less blood loss (98.33±61.32 versus 170.71±121.32 mL; P=0.017), smaller drainage volume (182.08±163.60 versus 1,924.82±3,370.02 mL; P=0.011), and shorter extubation time (5.67±1.07 versus 8.57±6.96 days; P=0.040) compared to tRLRNU group. There were no statistically differences in the other peri-operative parameters, including whole operation time, transfusion, visceral and vascular injuries, open conversion, post-operative bleeding, recovery time of intestinal function, and discharge time. The patient outcomes in tTLRNU group at 6 months were significantly worse than that of tRLRNU group by comparing progression-free survival, progression survival and mortality (P=0.039).ConclusionsThe tRLRNU was potentially safer, minimally invasive, and more effective compared to the tTLRNU. Due to the small sample size, short follow-up time and no randomization of the study, future comparative studies are warranted to further analyze long-term outcomes of tRLRNU.  相似文献   
93.
94.
Polyurethane cement (PUC) is now commonly used in the reinforcement of old bridges, which exhibit various issues such as poor toughness, temperature-sensitive mechanical properties, and brittle failure. These problems can lead to the failure of the reinforcement effect of the PUC on old bridges in certain operating environments, leading to the collapse of such reinforced bridges. In order to alleviate these shortcomings, in this study, the toughness of PUC is improved by adding polyvinyl alcohol (PVA) fiber, carbon fiber, and steel fiber. In addition, we study the change law of the flexural strength of PUC between −40 °C and +40 °C. The control parameters evaluated are fiber type, fiber volume ratio, and temperature. A series of flexural tests and scanning electron microscope (SEM) test results show that the flexural strength first increases and then decreases with the increase in the volume-doping ratio of the three fibers. The optimum volume-mixing ratios of polyvinyl alcohol (PVA) fiber, carbon fiber, and steel fiber are 0.3%, 0.04% and 1%, respectively. Excessive addition of fiber will affect the operability and will adversely affect the mechanical properties. The flexural strength of both fiber-reinforced and control samples decreases with increasing temperature. Using the flexural test results, a two-factor (fiber content, temperature) BP neural network flexural strength prediction model is established. It is verified that the model is effective and accurate, and the experimental value and the predicted value are in good agreement.  相似文献   
95.
Dolostone is widely distributed and commonly used as concrete aggregates. A large number of studies have shown that there are significant differences in the expansibility of different dolostones, and the key factors determining the expansibility of alkali carbonate rocks have not been clarified. In this paper, rocks were selected from five different geological ages: Jixianian, Cambrian, Ordovician, Devonian, and Triassic ages. The ordering degree and the content of MgCO3 of dolomites in rocks of different geological ages were determined by X-ray diffraction (XRD). The degree of dedolomitization reaction in rocks cured in 80 °C, 1 mol/L NaOH solution was determined by quantitative X-ray diffraction (QXRD). The morphology of dolomites in rocks was determined by a polarizing microscope. The products of the dedolomitization reaction were determined by field emission electron microscopy (FESEM-EDS). According to the test results, the following conclusions are drawn. There is a good positive correlation between ordering degree and the molar fraction of MgCO3 of dolomites. When the MgCO3 mole fraction of dolomites varies from 47.17% to 49.60%, the higher the MgCO3 mole fraction, the greater the ordering degree of dolomite. By analyzing the degree of the dedolomitization reaction of different dolostone powders cured at 80 °C in 1 mol/L NaOH solution, it is found that the older the geological age of dolostone, the slower the dedolomitization reaction rate and the lower the degree of dedolomitization reaction. The lower the ordering degree of dolomite crystal in the same geological age, the faster the rate of dedolomitization reaction and the higher the degree of dedolomitization reaction.  相似文献   
96.
97.
Objective: To determine the most influential data features and to develop machine learning approaches that best predict hospital readmissions among patients with diabetes.Methods: In this retrospective cohort study, we surveyed patient statistics and performed feature analysis to identify the most influential data features associated with readmissions. Classification of all-cause, 30-day readmission outcomes were modeled using logistic regression, artificial neural network, and Easy Ensemble. F1 statistic, sensitivity, and positive predictive value were used to evaluate the model performance. Results: We identified 14 most influential data features(4 numeric features and 10 categorical features) and evaluated 3 machine learning models with numerous sampling methods(oversampling, undersampling, and hybrid techniques). The deep learning model offered no improvement over traditional models(logistic regression and Easy Ensemble) for predicting readmission, whereas the other two algorithms led to much smaller differences between the training and testing datasets.Conclusions: Machine learning approaches to record electronic health data offer a promising method for improving readmission prediction in patients with diabetes. But more work is needed to construct datasets with more clinical variables beyond the standard risk factors and to fine-tune and optimize machine learning models.  相似文献   
98.
目的 了解宫颈癌患者信息选择的需求状况及影响因素.方法 采用一般资料问卷、卡氏功能量表和癌症患者信息选择问卷对78例宫颈癌患者进行调查分析.结果 癌症患者信息选择问卷的总分、诊断、治疗、预后和其他维度均分分别为39.04±7.42、6.19±1.28、10.69±2.63、10.08±2.07和12.01±2.43."我很想知道"信息内容排名前3位为条目4、8、13、12(8和13并列),"我不想知道"信息内容排名前3位为条目14、16、10.卡氏评分在80分及以上(可进行正常活动)组的总分、诊断、治疗、预后和其它因子均分均低于卡氏评分在70分及以下(生活受到不同程度的影响)组(t值分别为3.431、2.125、2.047、3.571、2.319,均P<0.05).年轻妇女、文化程度较高及脑力工作的癌症患者信息选择问卷某些分值较高,希望获知的信息需求较多.结论 癌症患者信息选择问卷及各维度得分与年龄、受教育程度、职业和健康状态有关,医生在为癌症患者提供治疗时,应注意其需要的疾病相关医学信息和健康需求.  相似文献   
99.
BackgroundDacomitinib is a first-line treatment for patients with non-small cell lung cancer (NSCLC) harboring common epidermal growth factor receptor (EGFR) mutations; however, clinical evidence of its activity on NSCLC with complex EGFR mutations is limited.MethodsPatients harboring complex (common mutations co-existing with uncommon mutations), or common (comparison cohort) EGFR mutations, who were treated with dacomitinib, were retrospectively evaluated in the Chinese National Cancer Center and the China PLA hospital between August 2019 and August 2021.ResultsIn total, 72 patients with NSCLC harboring complex (C+U group, n=18) or common (C group, n=54) EGFR mutations and being treated with dacomitinib were enrolled. In the C+U group, 16 cases (88.9%) harbored L858R mutations co-existing with uncommon mutations located from exon 18 to exon 25 of EGFR (mostly E709X), and two cases harbored exon 19 deletion co-existing with G724S or K754E. Among the 15 evaluable patients, the objective response rate (ORR) was 40% (6/15), and the disease control rate (DCR) was 73.3% (11/15). The median progression-free survival (PFS) was 7.5 months [95% confidence interval (CI), 4.4–10.6 months]. Except for the application line of dacomitinib (P=0.039), no significant statistical differences were found in other characteristics and adverse events between the two groups. The Kaplan-Meier method revealed no significant differences in PFS (P=0.889) and overall survival (OS) (P=0.703). However, the stratified analysis found worse PFS in the C+U group than that observed in the C group when receiving 1st and ≥3rd line dacomitinib treatment, while its OS was worse than that of group C when receiving ≥3rd line treatment. Furthermore, in a multivariate analysis, complex mutation status was an independent prognostic factor for OS (P=0.038) in the entire cohort.ConclusionsThis study indicated a worse response and prognosis of patients with NSCLC harboring complex EGFR mutations than those harboring common EGFR mutations when treated with dacomitinib. Further studies and data are needed to confirm this conclusion.  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