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   544篇
  免费   35篇
  国内免费   5篇
耳鼻咽喉   16篇
儿科学   13篇
妇产科学   18篇
基础医学   67篇
口腔科学   17篇
临床医学   53篇
内科学   125篇
皮肤病学   6篇
神经病学   19篇
特种医学   8篇
外科学   84篇
综合类   25篇
一般理论   1篇
预防医学   67篇
眼科学   11篇
药学   37篇
肿瘤学   17篇
  2023年   9篇
  2022年   24篇
  2021年   39篇
  2020年   13篇
  2019年   23篇
  2018年   17篇
  2017年   11篇
  2016年   12篇
  2015年   11篇
  2014年   18篇
  2013年   14篇
  2012年   30篇
  2011年   29篇
  2010年   26篇
  2009年   12篇
  2008年   32篇
  2007年   46篇
  2006年   29篇
  2005年   20篇
  2004年   20篇
  2003年   12篇
  2002年   13篇
  2001年   10篇
  2000年   11篇
  1999年   6篇
  1998年   5篇
  1997年   2篇
  1996年   4篇
  1995年   2篇
  1994年   5篇
  1993年   2篇
  1992年   8篇
  1991年   4篇
  1990年   5篇
  1989年   3篇
  1988年   3篇
  1986年   3篇
  1983年   3篇
  1979年   3篇
  1978年   4篇
  1976年   3篇
  1975年   6篇
  1974年   7篇
  1973年   4篇
  1972年   2篇
  1971年   3篇
  1970年   2篇
  1969年   3篇
  1966年   5篇
  1965年   2篇
排序方式: 共有584条查询结果,搜索用时 46 毫秒
21.
Acute lymphoblastic leukemia is one of the rare malignancies in adult. We report a 29‐year‐old man presented with progressive limping followed a chronic back pain. Imaging showed reduced vertebral body height and diffuse lytic skeletal infiltration. Bone marrow aspiration confirmed B‐acute lymphoblastic leukemia/lymphoma, and the patient was treated with chemotherapy.  相似文献   
22.
Objectives:To validate an Arabic version of the LittlEARS® Early Speech Production Questionnaire (LEESPQ), which assesses the early development of speech and language in infants between 0 and 18 months, in Arabic-speaking children with normal hearing in Saudi Arabia.Methods:This is a cross-sectional study conducted in the city of Riyadh, Saudi Arabia between September and December 2020. Parents completed the LEESPQ regarding their child’s speech production development. To assess the ability of normal hearing children aged 0-18 months in developing speech and language production, a norm curve has been generated based on the standardized values that were calculated from the Arabic normal-hearing data set.Results:A total of 198 questionnaires were analyzed. The total score on the LEESPQ correlated with age, gender, and bilingualism. A norm curve for early speech production in children with normal hearing was created.Conclusion:The Arabic version of LEESPQ appears to be a valid questionnaire that can be used in the assessment of early language and speech development of Arabic-speaking children with normal hearing in the age range of 0-18 months. The Arabic version of the LEESPQ might also be a useful tool to detect developmental delays and hearing disorders in young children.  相似文献   
23.
24.
Polymer dielectrics with ultra-high charge–discharge rates are significant for advanced electrical and electronic systems. Despite the fact that polymers possess high breakdown strength, the low dielectric constant (k) of polymers gives rise to low energy densities. Incorporating metal into polyimides (PI) at the polyamic acid (PAA) precursor stage of the synthetic process is a cheap and versatile way to improve the dielectric constant of the hybrid system while maintaining a high breakdown strength. Here, we explore inclusion of different percentages of Sn as a coordinated complex in a polyimide matrix to achieve metal homogeneity within the dielectric film to boost dielectric constant. Sn–O bonds with high atomic polarizability are intended to enhance the ionic polarization without sacrificing bandgap, a measurable property of the material to assess intrinsic breakdown strength. Enhancements of k from ca. 3.7 to 5.7 were achieved in going from the pure PI film to films containing 10 mol% tin.

Polyimide with high dielectric constant and breakdown strength is synthesized via tin complexation of the polyamide acid precursor. Sn–O bonds with high atomic polarizability are intended to enhance the ionic polarization without sacrificing bandgap.  相似文献   
25.

Purpose  

This study analyzed associations between war-related internal displacement, housing quality and the prevalence of chronic illness in Nabaa, a low-income neighborhood on the outskirts of Beirut, Lebanon.  相似文献   
26.
Objective. To translate quantitative ultrasound (QUS) from the laboratory into the clinic, it is necessary to demonstrate that the measurements are platform independent. Because the backscatter coefficient (BSC) is the fundamental estimate from which additional QUS estimates are calculated, agreement between BSC results using different systems must be demonstrated. This study was an intercomparison of BSCs from in vivo spontaneous rat mammary tumors acquired by different groups using 3 clinical array systems and a single‐element laboratory scanner system. Methods. Radio frequency data spanning the 1‐ to 14‐MHz frequency range were acquired in 3 dimensions from all animals using each system. Each group processed their radio frequency data independently, and the resulting BSCs were compared. The rat tumors were diagnosed as either carcinoma or fibroadenoma. Results. Carcinoma BSC results exhibited small variations between the multiple slices acquired with each transducer, with similar slopes of BSC versus frequency for all systems. Somewhat larger variations were observed in fibroadenomas, although BSC variations between slices of the same tumor were of comparable magnitude to variations between transducers and systems. The root mean squared (RMS) errors between different transducers and imaging platforms were highly variable. The lowest RMS errors were observed for the fibroadenomas between 4 and 5 MHz, with an average RMS error of 4 × 10?5 cm?1Sr?1 and an average BSC value of 7.1 × 10?4 cm?1Sr?1, or approximately 5% error. The highest errors were observed for the carcinoma between 7 and 8 MHz, with an RMS error of 1.1 × 10?1 cm?1Sr?1 and an average BSC value of 3.5 × 10?2 cm?1Sr?1, or approximately 300% error. Conclusions. This technical advance shows the potential for QUS technology to function with different imaging platforms.  相似文献   
27.
PURPOSE: This article presents an overview of etiologies associated with tooth wear. MATERIALS AND METHODS: Specific types of wear based on clinical findings and patient history are described. RESULTS: The occurrence and pattern of tooth wear are related to cultural, dietary, occupational, and geographic factors. Examples of tooth wear related to these factors with regional specificity are presented. CONCLUSION: The dental practitioner should recognize the characteristic signs of tooth wear, as they may be the first to discuss the problem with the patient. Management should be based on accurate diagnosis.  相似文献   
28.
Yassin KM 《Public health》2000,114(4):269-272
Because of a growing cultural and religious sensitivity and controversy over reproductive health issues, particularly abortion, this area remains relatively unexplored in Egypt. This study was conducted using a participatory approach to determine the morbidity and determinants of abortion in rural Upper Egypt. In all, 1025 women from six villages in Upper Egypt were included in the study. Information regarding the incidence of abortion, patterns of health care utilization and risk factors was obtained using a structured interview format. The local dialect was used in formulating questions and they were revised and amended by a panel of local leaders, interviewers and representatives of the study population. Interviewers were local educated (secondary or university level) female volunteers. Information about exposure to 17 risk factors was also collected and statistical analysis was done by estimating the odds ratio and applying a test of statistical significance. Then, a multivariate logistic regression model was applied to control for possible interactions and confounding effects. The results were that 40.6% (n=416) had aborted at least once; of them 24.6% (n=252) had aborted more than once and were designated as recurrent aborters. The lifetime prevalence of recurrent abortion was estimated to be 25% and nearly 21% of pregnancies were aborted. The incidence of abortion was estimated to be 265 per 1000 live birth. Only 21.9% (n=91) of women received medical care for the last abortion. The vast majority of women (92%, n=299) who did not seek medical help received help from traditional and domestic sources. These sources are midwife (59.9%, n=179), relative or neighbour (29.8%, n=89), and traditional practitioner (10.4%, n=31). The multivariate analysis revealed that the incidence of abortion is significantly associated with gravidity, consanguinity, and mother occupation, while recurrent abortion is associated with gravidity, consanguinity and woman's age at marriage. In conclusion, the morbidity of abortion is a serious public health problem in Egypt. Because the incidence rate is very high and because safe abortion is limited in Egypt, maternal mortality due to abortion is expected to be underestimated. Promotion of family planning is expected to have a significant impact on the incidence of abortion in Upper Egypt.  相似文献   
29.
30.
BACKGROUND: Left main coronary artery disease (LMCD) is considered a relative contraindication to off-pump coronary artery bypass (OPCAB) grafting. This study evaluates the safety and feasibility of OPCAB in these patients compared to an on-pump group (cardiopulmonary bypass, CPB) with LMCD. METHODS: Between January 2000 and July 2002, 95 patients with left main coronary artery stenosis >50% underwent coronary revascularization. Seventy-three unselected patients underwent OPCAB and 22 underwent revascularization using CPB. The techniques used for OPCAB included the use of deep traction sutures in the posterior pericardium and stabilizers to expose the distal coronary targets. Intraluminal coronary shunts were routinely used during construction of the anastomoses. Variables were analyzed using a Student's paired t-test with statistical significance defined as p < 0.05. RESULTS: The mean age in the OPCAB group was 59.9 years and the CPB group 61.8 years (p = 0.54). There were 56 males (77%) in the OPCAB and 18 (82%) in the CPB groups. Mean preoperative left ventricular ejection fraction (LVEF) was 40.3% in OPCAB and 47.3% in CPB (p = 0.015). Average number of grafts was 3.1 in OPCAB and 4.1 in CPB (p = 0.0038). There were no conversions to CPB in those patients initially chosen to undergo OPCAB. There were no early deaths in OPCAB. There was one death in CPB. Mean hospital length of stay was 6.9 days for OPCAB and 9.1 for CPB (p = 0.0159). CONCLUSIONS: Patients with LMCD can undergo OPCAB grafting safely and effectively despite reduced LVEF. LMCD should no longer be seen as a contraindication to perform OPCAB grafting.  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