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   17669篇
  免费   1004篇
  国内免费   436篇
耳鼻咽喉   177篇
儿科学   332篇
妇产科学   363篇
基础医学   2281篇
口腔科学   480篇
临床医学   2533篇
内科学   1929篇
皮肤病学   243篇
神经病学   429篇
特种医学   642篇
外国民族医学   1篇
外科学   3272篇
综合类   1837篇
现状与发展   1篇
预防医学   1859篇
眼科学   265篇
药学   1638篇
  6篇
中国医学   377篇
肿瘤学   444篇
  2024年   22篇
  2023年   230篇
  2022年   393篇
  2021年   564篇
  2020年   561篇
  2019年   539篇
  2018年   587篇
  2017年   472篇
  2016年   583篇
  2015年   537篇
  2014年   1077篇
  2013年   1052篇
  2012年   1012篇
  2011年   1090篇
  2010年   881篇
  2009年   861篇
  2008年   872篇
  2007年   864篇
  2006年   760篇
  2005年   655篇
  2004年   598篇
  2003年   513篇
  2002年   420篇
  2001年   424篇
  2000年   313篇
  1999年   301篇
  1998年   264篇
  1997年   252篇
  1996年   247篇
  1995年   187篇
  1994年   202篇
  1993年   162篇
  1992年   167篇
  1991年   180篇
  1990年   139篇
  1989年   122篇
  1988年   147篇
  1987年   96篇
  1986年   111篇
  1985年   119篇
  1984年   99篇
  1983年   81篇
  1982年   87篇
  1981年   74篇
  1980年   86篇
  1979年   28篇
  1978年   18篇
  1977年   15篇
  1976年   10篇
  1975年   12篇
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
11.
IntroductionScales for predicting venous thromboembolism (VTE) recurrence are useful for deciding the duration of the anticoagulant treatment. Although there are several scales, the most appropriate for our setting has not been identified. For this reason, we aimed to validate the DASH prediction score and the Vienna nomogram at 12 months.MethodsThis was a retrospective study of unselected consecutive VTE patients seen between 2006 and 2014. We compared the ability of the DASH score and the Vienna nomogram to predict recurrences of VTE. The validation was performed by stratifying patients as low-risk or high-risk, according to each scale (discrimination) and comparing the observed recurrence with the expected rate (calibration).ResultsOf 353 patients evaluated, 195 were analyzed, with an average age of 53.5 ± 19 years. There were 21 recurrences in 1 year (10.8%, 95% CI: 6.8%-16%). According to the DASH score, 42% were classified as low risk, and the rate of VTE recurrence in this group was 4.9% (95% CI: 1.3%-12%) vs. the high-risk group that was 15% (95% CI: 9%-23%) (p <.05). According to the Vienna nomogram, 30% were classified as low risk, and the rate of VTE recurrence in the low risk group vs. the high risk group was 4.2% (95% CI:0.5%-14%) vs. 16.2% (95% CI: 9.9%-24.4%) (p <.05).ConclusionsOur study validates the DASH score and the Vienna nomogram in our population. The DASH prediction score may be the most advisable, both because of its simplicity and its ability to identify more low-risk patients than the Vienna nomogram (42% vs. 30%).  相似文献   
12.
IntroductionThis study aims to construct learning curves related to the realization of standardized postprocessing by radiographer students and to discuss their exploitation and interest.Materials and MethodsThis study was carried out in 21 French students in their 3rd year of training. Two postprocessing protocols in CT (#1 traumatic shoulder; #2 petrous bone) were repeated 15 times by each student. Each achievement was timed to obtain overall learning curves. The realization accuracy was also assessed for each student at each repetition.ResultsThe learning rates for the two protocols are 63% and 56%, respectively. The number of repetitions to reach the reference time for each protocol is 11 and 12, respectively. In both protocols, the standard deviations are significantly reduced and stabilized during repetitions. The mean accuracy progresses more quickly in protocol #1.DiscussionThe measured learning rates reflect a rapid learning process for each protocol. The analysis of the standard deviations shows that students have reached a homogeneous level. The average times and accuracies measured during the last repetitions show that the group has reached a high level of performance. Building learning curves helps students measure their progress and motivates them.ConclusionObtaining learning curves allows trainers/supervisors to qualify the learning difficulty of a task while motivating students/radiographers. The use of learning curves is inline with the competency-based training paradigm.  相似文献   
13.
14.
ABSTRACT

Although exclusive breastfeeding has been linked to lower rates of postnatal HIV transmission compared to nonexclusive breastfeeding, mechanisms underlying this are unclear. Across a longitudinally sampled cohort of South African infants, we showed that exclusively breastfed (EBF) infants had altered gut bacterial communities when compared to nonexclusively breastfed (NEBF) infants, as well as reduced peripheral CD4 + T cell activation and lowered chemokine and chemokine receptor expression in the oral mucosa. We further demonstrated that the relative abundance of key taxa was correlated with peripheral CD4 + T cell activation. Here, we supplement those findings by using compositional data analyses to identify shifts in the abundance of several Bifidobacteria strains relative to select strains of Escherichia, Bacteroides, and others that are associated with the transition to NEBF. We illustrate that the abundance ratio of these taxa is tightly correlated with feeding modality and is a strong predictor of peripheral T cell activation. More broadly, we discuss our study in the context of novel developments and explore future directions for the field.  相似文献   
15.
The presented case reports on successful treatment with everolimus in a neonate with left ventricular giant rhabdomyoma. The authors used a different dosage regime compared to literature and documented rapid tumor regression by 3D echocardiography.  相似文献   
16.
目的探讨帕金森病(PD)的CT表现及微电极导向脑内核团毁损术后CT影像特点。资料与方法(1)对240例PD患者术前CT影像进行回顾性分析。(2)30例PD患者在术后3~12个月(平均6·5个月)CT扫描,观测脑内核团毁损灶33个(其中3例患者为双侧手术):右苍白球腹后内侧核(Gpi)毁损灶14个、左Gpi核毁损灶6个,右丘脑腹外侧核(Vim)毁损灶2个、左Vim核毁损灶11个,对毁损灶最大层面积、术侧CT值(任意值)、健侧对应点CT值(标准值)测量,并算出毁损灶与健侧CT值的差值。结果(1)PD的CT表现主要为中央型弥漫性脑萎缩,以脑室系统扩大为主,轻度脑萎缩46.67%(112/240),中度脑萎缩40%(96/240),重度脑萎缩3.33%(8/240),正常10%(24/240)。(2)33个毁损靶灶之圆形占27·27%(9/33);类圆形占60·61%(20/33);片状不规则形占12·12%(4/33)。毁损灶的面积Gpi核平均(28·01±2.15)mm2,Vim核平均为(14.03±1.24)mm2,两者对比有显著性差异(P<0.01);毁损灶Gpi核CT值较健侧平均下降(11.80±0.87)HU,Vim核CT值较健侧平均下降(10.80±1.28)HU,两者亦有差异性(P<0·05)。结论PD患者术前CT扫描对掌握手术适应证较重要,重度脑萎缩患者提示不宜做外科手术治疗。术后CT扫描观察毁损灶之形态、面积、密度变化等影像学改变,有利于对手术疗效、并发症等评估提供一定证据。  相似文献   
17.
目的探讨重组腺病毒介导的β-半乳糖苷酶(LacZ)基因在大鼠肺脏的转基因表达。方法Wistar大鼠70只,随机分为Ad-Null组和Ad-LacZ组(n=35),分别应用1.67×10~9pfu/ml复制缺陷型重组腺病毒AdCMV和AdCMVLacZ各600μl,经气管导管滴入;各组于滴人病毒后2、5、7、14、21、28和35 d行肺组织X-gal染色。另取大鼠20只,随机分为C组、L组、M组和H组(n=5),分别应用病毒保存液和低滴度(1.67×10~8pfu/ml)、中滴度(1.67×10~9pfu/ml)、高滴度(5×10~9pfu/ml)的AdCMVLacZ各600μl,滴入病毒后7 d行肺组织X-gal染色和HE染色。结果滴入病毒后2 d,Ad-LacZ组肺组织内即有转基因表达,滴人后7 d达高峰,并维持至35 d;转基因表达位于气管、支气管上皮细胞和肺泡细胞。H组、M组转基因阳性细胞率明显高于L组和C组(P<0.01)。HE染色显示,H组中3只大鼠肺组织有轻度炎性浸润。所有动物均未见远隔器官转基因表达。结论气管内滴人重组腺病毒可呈剂量依赖性介导LacZ基因在大鼠肺内表达,但过高剂量可诱发机体炎性反应。  相似文献   
18.
19.
Clinical decisions are often made with incomplete information, yet patient care decisions are made every day. Patients vary clinically, uncertainty exists in diagnostic and prognostic information, and many preventive and treatment alternatives have not been formally assessed for their effectiveness. Because scientific information will never answer all clinical questions, clinical decisions are partially based on probabilistic information.
This paper describes how to apply clinical decision making to diagnosing and managing dental caries and periodontal diseases. By using explicit information to quantify probabilities and outcomes, clinical decision making analyzes decisions made under uncertain conditions and the uncertain impact of clinical information.
Clinical decision making incorporates concepts for preventing, diagnosing and treating dental caries and periodontal diseases: risk assessment, evidence-based dentistry, and multiple oral health outcomes. This information can serve as a tool for clinicians to augment clinical judgment and expertise.  相似文献   
20.
Background The Retinal Thickness Analyser (RTA) is intended to detect glaucomatous changes as well as macular pathologies at the posterior pole. We determined the diagnostic accuracy for eyes with manifest glaucoma or macular diseases.Methods We examined 71 eyes with long-term, established eye conditions. Included were 28 eyes with glaucoma, 21 with different macular diseases and 22 normal eyes. All examinations were evaluated in a blind-test by RTA experts without any clinical information on the patients. After comparison of the RTA interpretation with the clinical diagnosis, we determined sensitivity, specificity, positive and negative predictive values.Results Of 71 examinations, 15 (21%) were not interpretable. If these results are excluded, the following diagnostic accuracy values were calculated for glaucoma and macular disorders respectively: sensitivity 75 and 59%, specificity 55 and 97%, positive predictive value 48 and 90% and negative predictive value 80 and 84%. These values were not significantly different when both eyes of each patient were included in the final analysis (n=133).Conclusion The diagnostic values of the RTA determined in this case control study were not satisfactory. However, no clinical information was used in the assessment. The extent to which additional clinical information increases the diagnostic value remains to be determined.  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