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   5291篇
  免费   511篇
  国内免费   96篇
耳鼻咽喉   42篇
儿科学   107篇
妇产科学   59篇
基础医学   528篇
口腔科学   70篇
临床医学   640篇
内科学   985篇
皮肤病学   101篇
神经病学   336篇
特种医学   583篇
外科学   499篇
综合类   733篇
预防医学   395篇
眼科学   81篇
药学   259篇
  1篇
中国医学   405篇
肿瘤学   74篇
  2024年   5篇
  2023年   59篇
  2022年   96篇
  2021年   222篇
  2020年   178篇
  2019年   178篇
  2018年   187篇
  2017年   172篇
  2016年   183篇
  2015年   182篇
  2014年   341篇
  2013年   353篇
  2012年   282篇
  2011年   317篇
  2010年   258篇
  2009年   251篇
  2008年   279篇
  2007年   308篇
  2006年   261篇
  2005年   205篇
  2004年   162篇
  2003年   137篇
  2002年   120篇
  2001年   114篇
  2000年   68篇
  1999年   55篇
  1998年   82篇
  1997年   86篇
  1996年   88篇
  1995年   71篇
  1994年   79篇
  1993年   59篇
  1992年   63篇
  1991年   48篇
  1990年   45篇
  1989年   35篇
  1988年   47篇
  1987年   20篇
  1986年   29篇
  1985年   25篇
  1984年   25篇
  1983年   16篇
  1982年   14篇
  1981年   24篇
  1980年   12篇
  1979年   9篇
  1978年   10篇
  1977年   6篇
  1976年   6篇
  1971年   4篇
排序方式: 共有5898条查询结果,搜索用时 15 毫秒
11.
目的 了解、观察葡立胶囊与抗骨增生胶囊联用治疗颈椎病对血清SOD含量及疼痛功能评分的影响。方法 对一组神经根型颈椎病患者,用葡立胶囊与抗骨增生胶囊联合应用治疗3个月,测定血清SOD含量及疼痛功能评分变化。结果 颈椎病患者治疗组血清SOD含量与治疗前相比明显升高,疼痛功能评分治疗前相比明显降低。结论 葡立胶囊与抗骨增生胶囊联合应用可明显缓解症状,提高血清SOD活力,延缓颈椎间盘退变,对治疗颈椎病有明显疗效。  相似文献   
12.
The pharmacokinetics and haemodynamic effects of isosorbide dinitrate (ISDN) have been investigated following administration of single doses as a sublingual (SL) spray (2.5 mg), sublingual tablet (5 mg) and peroral tablet (10 mg) in a randomised, placebo-controlled double-blind cross-over trial in 16 healthy volunteers.After the sublingual spray Cmax was higher (39.0 ng·ml-1) and tmax was shorter (3.9 min) than after the sublingual (22.8 ng·ml-1 and 13.8 min) and peroral (16.9 ng·ml-1 and 25.6 min) tablets. The AUC of ISDN did not differ following any of the three formulations (1031; 879; 997 ng·ml-1·min, for the spray, SL tablet and PO-tablet, respectively). Mononitrate metabolites of ISDN (IS-2-MN and IS-5-MN) and total nitrates in plasma increased in proportion to the administered dose. This indicates that the fraction of the dose absorbed was the same for all the formulations but that the extent of first-pass metabolism increased in the order sublingual spray < sublingual tablet < peroral tablet. Thus, compared to the spray, the relative bioavailability of ISDN was 48% and 28% from the sublingual and peroral tablets, respectively.The haemodynamic effects were quantified using the a/b ratio of the finger pulse wave and the systolic blood pressure and heart rate under orthostatic conditions. For the a/b ratio of the finger pulse, the maximal effect was higher (emax=130%) and the time to emax (temax) shorter (16.6 min) after the spray than the sublingual tablet (84.4% and 25.5 min) or peroral tablet (90.2 and 31.3 min). The onset of effect was within 3, 5 and 7.5 min after the spray, sublingual and peroral tablets, respectively. A larger change in the orthostatically-induced decrease in systolic blood pressure and increase in heart rate was obtained following peroral than sublingual administration despite the similar plasma concentrations of ISDN. This probably reflects the larger amount of pharmacodynamically active mononitrate metabolites formed after oral dosing. The integrated effect following administration of 2.5 mg ISDN as spray was similar to that of a sublingual tablet of 5 mg.  相似文献   
13.
戴红 《山西中医》2009,25(4):54-55
目的:观察益气复脉汤对脑缺血再灌注模型大鼠血浆内皮素(ET)和降钙素基因相关肽(CGRP)含量变化的影响,探讨大鼠脑缺血再灌注损伤的中医药治疗方法。方法:采用线栓法制备大鼠右侧大脑中动脉脑缺血再灌注损伤模型,分别用益气复脉汤高、低剂量组、尼莫地平水溶液予以治疗,然后采用放射免疫法检测血清ET和CGRP含量。结果:模型组脑缺血再灌注大鼠血浆ET含量明显增高,而CGRP下降,治疗后ET值比对照组下降明显(P〈0.01),CGRP值比对照组增高明显(P〈0.05)。结论:益气复脉汤通过降低ET和增高CGRP,能够对脑缺血再灌注损伤脑起保护作用,其疗效优于尼莫地平。  相似文献   
14.
目的 探讨工频磁场 (PFMF)是否有促癌或协同促癌作用。方法 利用荧光光漂白后再恢复法观察漂白细胞荧光强度的恢复以判断经间隙连接的细胞间通讯 ,以相对荧光强度恢复速率(CFIRR)作为对细胞间隙连接通讯 (GJIC)作用的评价指标 ,研究不同磁场强度单独作用或协同佛波酯(TPA)对星形胶质细胞GJIC功能的影响。结果  3ng/mlTPA作用 1h时CFIRR的中位数 (Md)值为4 .53 % /min ,空白对照组为 9.74% /min ,两组的差异有显著性 (H =1 2 .0 84,P <0 .0 0 5)。 0 .8或 1 .6mT磁场作用 2 4h时CFIRR的Md 分别 8.2 5、6 .68% /min ,与空白对照组比较 ,差异无显著性 (H =32 .61 7,P >0 .0 5)。 0 .8或 1 .6mT磁场作用 2 3h ,再与TPA共同作用 1h时CFIRR的Md 分别为 3 .32、2 .85% /min ,与TPA组比较 ,差异无显著性 (H =2 .589,P >0 .0 5)。结论  0~ 1 .6mT的 50Hz磁场单独作用不能抑制星形胶质细胞GJIC功能 ;协同TPA ,不能增强TPA对星形胶质细胞GJIC的抑制作用 ;但是磁场对星形胶质细胞GJIC的抑制作用随着磁场强度增强呈递增趋势  相似文献   
15.
RASER: a new ultrafast magnetic resonance imaging method.   总被引:1,自引:0,他引:1  
A new MRI method is described to acquire a T(2)-weighted image from a single slice in a single shot. The technique is based on rapid acquisition by sequential excitation and refocusing (RASER). RASER avoids relaxation-related blurring because the magnetization is sequentially refocused in a manner that effectively creates a series of spin echoes with a constant echo time. RASER uses the quadratic phase produced by a frequency-swept chirp pulse to time-encode one dimension of the image. In another implementation the pulse can be used to excite multiple slices with phase-encoding and frequency-encoding in the other two dimensions. The RASER imaging sequence is presented along with single-shot and multislice images, and is compared to conventional spin-echo and echo-planar imaging sequences. A theoretical and empirical analysis of the spatial resolution is presented, and factors in choosing the spatial resolution for different applications are discussed. RASER produces high-quality single-shot images that are expected to be advantageous for a wide range of applications.  相似文献   
16.
17.
Summary: Severe secondary hyperparathyroidism in chronic dialysis patients has been recently treated by supraphysiological concentration of calcitriol achieved through pulse therapy. However, there are many patients resistant to this therapy, who usually have larger parathyroid gland(s). to overcome this resistance, calcitriol was injected directly into the enlarged glands under ultrasonographic guidance. We injected 70–90% of the calculated gland volume of calcitriol solution (1 μg/mL) into the glands of 7 patients three times per week for 2 weeks. the parathyroid hormone (PTH) levels decreased significantly after 2 weeks of direct injections of calcitriol. Following a further 4 weeks of calcitriol pulse therapy, PTH levels remained suppressed and serum alkaline phosphatase activity and the volume of parathyroid glands also decreased. During the long-term follow up, five patients remained well controlled with calcitriol pulse therapy, while two patients needed ethanol injections to control hyperparathyroidism. Although we could not completely rule out a toxic effect of the vehicle, direct injection of calcitriol into parathyroid glands may be another treatment option for chronic dialysis patients. Our data further support the important role of resistance of parathyroid cells to calcitriol in the pathogenesis of parathyroid hyper function in uraemic patients.  相似文献   
18.
A number of pulse sequence techniques, including magnetization-prepared gradient echo (MP-GRE), segmented GRE, and hybrid RARE, employ a relatively large number of variable pulse sequence parameters and acquire the image data during a transient signal evolution. These sequences have recently been proposed and/or used for clinical applications in the brain, spine, liver, and coronary arteries. Thus, the need for a method of deriving optimal pulse sequence parameter values for this class of sequences now exists. Due to the complexity of these sequences, conventional optimization approaches, such as applying differential calculus to signal difference equations, are inadequate. We have developed a general framework for adapting the simulated annealing algorithm to pulse sequence parameter value optimization, and applied this framework to the specific case of optimizing the white matter-gray matter signal difference for a T1-weighted variable flip angle 3D MP-RAGE sequence. Using our algorithm, the values of 35 sequence parameters, including the magnetization-preparation RF pulse flip angle and delay time, 32 flip angles in the variable flip angle gradient-echo acquisition sequence, and the magnetization recovery time, were derived. Optimized 3D MP-RAGE achieved up to a 130% increase in white matter-gray matter signal difference compared with optimized 3D RF-spoiled FLASH with the same total acquisition time. The simulated annealing approach was effective at deriving optimal parameter values for a specific 3D MP-RAGE imaging objective, and may be useful for other imaging objectives and sequences in this general class.  相似文献   
19.
This report describes a patient with an implantable defibrillator who suffered an inappropriate defibrillation shock upon retrieving some food items from his inadequately earthed refrigerator. Noise typical of electrical interference can be observed in the stored electrogram of the episode. The patient was instructed to earth his home appliances, but he decided to avoid his refrigerator altogether, and has had no subsequent shocks.  相似文献   
20.
本文通过对不同海拔高度藏汉族健康青青年的400幅脉图分析后认为,健康藏汉族青年的脉象以滑、平、弦、缓为多。结古和西宁的藏汉族青年脉力图的主要生理参数中不同海拔高度上有一定差异,表现为结古青年弦脉较多,而西宁教地区滑脉较多,究其形成原因,主要与高海拔缺氧、寒冷环境有密切关系;在民族间也存在一定差异,表现为汉族弦脉多,藏族滑脉多,它们的形成与移居高原后心血管的反庆和代偿机制有关,在性别间有明星的差异。  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