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   5041篇
  免费   414篇
  国内免费   110篇
耳鼻咽喉   43篇
儿科学   49篇
妇产科学   75篇
基础医学   655篇
口腔科学   161篇
临床医学   575篇
内科学   1089篇
皮肤病学   43篇
神经病学   215篇
特种医学   209篇
外国民族医学   1篇
外科学   687篇
综合类   703篇
现状与发展   2篇
预防医学   263篇
眼科学   83篇
药学   428篇
  5篇
中国医学   109篇
肿瘤学   170篇
  2024年   12篇
  2023年   112篇
  2022年   251篇
  2021年   306篇
  2020年   253篇
  2019年   192篇
  2018年   171篇
  2017年   178篇
  2016年   178篇
  2015年   221篇
  2014年   306篇
  2013年   411篇
  2012年   216篇
  2011年   265篇
  2010年   244篇
  2009年   213篇
  2008年   201篇
  2007年   217篇
  2006年   168篇
  2005年   145篇
  2004年   134篇
  2003年   134篇
  2002年   116篇
  2001年   91篇
  2000年   92篇
  1999年   68篇
  1998年   60篇
  1997年   77篇
  1996年   55篇
  1995年   47篇
  1994年   46篇
  1993年   40篇
  1992年   29篇
  1991年   28篇
  1990年   30篇
  1989年   21篇
  1988年   27篇
  1987年   27篇
  1986年   16篇
  1985年   23篇
  1984年   35篇
  1983年   20篇
  1982年   28篇
  1981年   17篇
  1980年   12篇
  1979年   9篇
  1978年   6篇
  1977年   7篇
  1974年   4篇
  1973年   3篇
排序方式: 共有5565条查询结果,搜索用时 15 毫秒
1.
In this paper, we introduce a new type of troubled-cell indicator to improve hybrid weighted essentially non-oscillatory (WENO) schemes for solving the hyperbolic conservation laws. The hybrid WENO schemes selectively adopt the high-order linear upwind scheme or the WENO scheme to avoid the local characteristic decompositions and calculations of the nonlinear weights in smooth regions. Therefore, they can reduce computational cost while maintaining non-oscillatory properties in non-smooth regions. Reliable troubled-cell indicators are essential for efficient hybrid WENO methods. Most of troubled-cell indicators require proper parameters to detect discontinuities precisely, but it is very difficult to determine the parameters automatically. We develop a new troubled-cell indicator derived from the mean value theorem that does not require any variable parameters. Additionally, we investigate the characteristics of indicator variable; one of the conserved properties or the entropy is considered as indicator variable. Detailed numerical tests for 1D and 2D Euler equations are conducted to demonstrate the performance of the proposed indicator. The results with the proposed troubled-cell indicator are in good agreement with pure WENO schemes. Also the new indicator has advantages in the computational cost compared with the other indicators.  相似文献   
2.
Malaria, one of the most striking, re-emerging infectious diseases caused by the genus Plasmodium, places a huge burden on global healthcare systems. A major challenge in the control and eradication of malaria is the continuous emergence of increasingly widespread drug-resistant malaria, creating an urgent need to develop novel antimalarial agents. Chalcone derivatives are ubiquitous in nature and have become indispensable units in medicinal chemistry applications due to their diverse biological profiles. Many chalcone derivatives demonstrate potential in vitro and in vivo antimalarial activity, so chalcone could be a useful template for the development of novel antimalarial agents. This review covers the recent development of chalcone hybrids as antimalarial agents. The critical aspects of the design and structure–activity relationship of these compounds are also discussed.  相似文献   
3.
4.
报告1例严重胸腹部闭合性联合伤所致的急性呼吸心跳骤停得到成功救治的病例。闭合性胸腹联合伤后,因病情可能发展,应随时注意复查胸片、血气等;若基层医院条件不够,应及时转往上级医院,以免延误患者的治疗。  相似文献   
5.
采用快速粘度分析仪(RVA)研究了食盐对18种普通玉米杂交种淀粉糊化性质的影响。结果表明:食盐显著降低了所有普通玉米杂交种淀粉的峰值、破损值和回生值;提高了谷值、终粘度、出峰时间和成糊温度。但对不同的普通玉米杂交种淀粉的糊化性质的影响程度有显著差别。随着食盐溶液质量分数的增加,普通玉米杂交种淀粉的谷值、终粘度、出峰时间和成糊温度也逐渐增加,破损值和回生值则显著降低,峰值受食盐溶液质量分数的影响很小。  相似文献   
6.
Abstract: The use of neuromuscular electrical stimulation (NMES) for rehabilitation of gait in spinal patients is widely known. The best results can be obtained with the use of biomechanical sensors and a closed loop NMES system. One of the biggest problems faced in the design of control systems for closed-loop operation, in gait rehabilitation, is the variation of the mechanical conditions during the phases of gait. This work presents a new approach to ease the design of rule-based closed loop systems for operation in conditions such as gait rehabilitation.  相似文献   
7.
BACKGROUND: Bowel-associated dermatosis-arthritis syndrome denotes the occurrence of diarrhoea with arthritis and skin lesions related to bowel disease with or without bowel bypass. In this condition, the histological finding of cutaneous aseptic neutrophilic cell infiltrate is non-specific and common to a wide spectrum of neutrophilic dermatoses, including pyoderma gangrenosum. OBSERVATION: We describe a 78-year-old woman with fever, abdominal discomfort and arthralgias, who developed grouped pustular lesions on her shins with histologically spongiform pustule formation. Aetiological assessment disclosed diverticular disease with sigmoid stenosis. CONCLUSION: Although clinical and histological features in our case fit the diagnosis of bowel-associated dermatosis-arthritis syndrome, they may also correspond to a pustular variant of pyoderma gangrenosum. Our observation raises the question of the nosological classification of bowel-associated dermatosis-arthritis syndrome within the spectrum of neutrophilic diseases.  相似文献   
8.
左双腔支气管导管管端位置与吸气峰压变化的关系   总被引:13,自引:3,他引:10  
目的 观测无隆突钩双腔支气管导管(DLT)管端位置与吸气峰压(Ppeak)以及肺顺应性环形状改变的关系,探讨用Ppeak和顺应性环的变化评估DLT管端位置的可行性。方法 拟行右侧剖胸手术的成年患者32例,静脉诱导后插入左Mallinckrodt DLT,吸入氧化亚氮和地氟醚维持麻醉。按纤维支气管镜(FOB)确认DLT管端位置和通气方式将观测过程分为四个阶段:第一阶段(S1),管端位置正确的双肺通气;第二阶段(S2),管端位置正确的左侧单肺通气;第三阶段(S3),管端插入左下支气管(置管过深)的左侧单肺通气;第四阶段(S。),管端处在左支气管开口(置管偏浅)的左侧单肺通气。每阶段均机械通气15min。结果 回归方程预计插管深度与FOB检查符合者占71.9%。S2时Ppeak值比S1时增加50.8%,肺顺应性(Cdyn)值减少36.2%;S3时Ppeak值比S1时增加87.4%,Cdyn值减少56.8%。PV环曲线斜率向右明显移位,环体显著延长。结论 用无隆突钩DLT行肺隔离,在无FOB定位的条件时,联合应用听诊法、回归方程预计插管深度、动态监测气道峰压和P-V环的变化综合评估,可提高DLT管端的正确到位率。单肺通气的气道峰压超过双肺通气时的1.65倍,且气道峰压超过25cm H2O.应高度怀疑DLT管端发生过深移位。  相似文献   
9.
Treatment of complete acromioclavicular joint disruption remains controversial and ranges from rehabilitation to extensive surgical reconstruction. However, high-grade injuries (type IV, V, and VI) are typically treated surgically. Most reconstruction techniques addressing these injuries selectively focus on coracoclavicular ligament augmentation because it has been shown to be the primary stabilizer of the acromioclavicular joint. The conventional coracoclavicular polydioxanone (PDS) loop, which is widely performed, has been detected to have some pivotal disadvantages, including anterior subluxation of the clavicle, extensive preparation of the coracoid, and bony avulsion of the clavicle as a result of rotational clavicle movement. Therefore we present an augmentation technique that reduces these complications by replicating the orientation of the native coracoclavicular ligament complex and providing a minimally invasive subcoracoid and clavicular fixation of a double PDS loop by use of 2 flip buttons, typically used for extracortical anterior cruciate ligament graft fixation. The key step of the procedure includes the anatomic, secure, and stable placement of the double PDS cerclage under the coracoid base transferring a flip button through a coracoid bone tunnel. Our clinical experience shows that the presented technique is easy to perform and has a comparable invasiveness to recently presented arthroscopic techniques.  相似文献   
10.
Introduction: One of the causes of pain during insertion of the colonoscope is stretching of the mesenterium by loop formation. The degree of pain differs according to the type of loop formation. Our aims were to study the accuracy of the colonoscopist’s assessment of the presence and type of loop formation and to study the degree of pain in relation to the type of loop by administering the visual analog scale (VAS). Methods: Two hundred and fifty‐seven consecutive patients were enrolled. All procedures were performed by two experienced colonoscopists who were blind to magnetic endoscope imaging view. After the colonoscopy, the colonoscopist was asked to assess the presence and type of loop formation. The degree of pain was assessed using the VAS. Results: The accuracy of estimating N loop, alpha loop, absence of loop formation and U loop was each over 70%. The accuracy of estimating gamma and splenic loop was significantly lower than the accuracy of estimating U loop. Colonoscopy was significantly more painful in women than in men. The degree of pain was significantly higher upon formation of reverse alpha loop and gamma and splenic loop than upon formation of N loop and U loop. Conclusions: Upon formation of reverse alpha loop or gamma and splenic loop, patients experienced more pain and it was difficult for the endoscopists to assess these loops. As women had severe pain compared with men, the use of a pediatric colonoscope or higher dosage of sedation in women should be considered.  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