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   1402篇
  免费   89篇
  国内免费   33篇
耳鼻咽喉   8篇
儿科学   18篇
妇产科学   20篇
基础医学   193篇
口腔科学   19篇
临床医学   129篇
内科学   182篇
皮肤病学   25篇
神经病学   98篇
特种医学   51篇
外科学   139篇
综合类   191篇
现状与发展   1篇
预防医学   184篇
眼科学   10篇
药学   95篇
  1篇
中国医学   111篇
肿瘤学   49篇
  2024年   3篇
  2023年   14篇
  2022年   58篇
  2021年   84篇
  2020年   51篇
  2019年   35篇
  2018年   35篇
  2017年   42篇
  2016年   33篇
  2015年   35篇
  2014年   95篇
  2013年   96篇
  2012年   82篇
  2011年   92篇
  2010年   67篇
  2009年   69篇
  2008年   87篇
  2007年   74篇
  2006年   67篇
  2005年   42篇
  2004年   45篇
  2003年   28篇
  2002年   33篇
  2001年   22篇
  2000年   20篇
  1999年   21篇
  1998年   11篇
  1997年   17篇
  1996年   15篇
  1995年   15篇
  1994年   9篇
  1993年   8篇
  1992年   9篇
  1991年   9篇
  1990年   5篇
  1989年   10篇
  1988年   8篇
  1987年   9篇
  1986年   8篇
  1985年   7篇
  1984年   9篇
  1983年   5篇
  1982年   3篇
  1981年   9篇
  1980年   2篇
  1979年   4篇
  1978年   4篇
  1977年   9篇
  1976年   4篇
  1974年   4篇
排序方式: 共有1524条查询结果,搜索用时 0 毫秒
131.
Controlled freezing studies on boar sperm cryopreservation   总被引:2,自引:0,他引:2  
Boar spermatozoa from different males were frozen at a number of cooling rates using a controlled-rate freezing machine designed to minimise thermal variables involved in the cooling process, to see whether inter-boar sperm cryosurvival may be improved by changing cooling rate. Four cooling rates in the range 3 °C min−1 to 24 °C min−1 from +5 °C to −5 °C and five cooling rates in the range 5 °C min−1 to 80 °C min−1 from −5 °C to −80 °C were tested. Motile spermatozoa were assessed by CASA, plasma membrane integrity by fluorescent probes (SYBR14/propidium iodide) and flow cytometry, and acrosome membrane integrity by lectins (PSA-rhodamine) and fluorescent microscopy. Cooling rate affected sperm cryosurvival from different boars in different ways; that is, spermatozoa from some individuals were less susceptible than those from others. For some individuals, sperm cryosurvival was poor regardless of cooling rate, but for others it was better with faster rates. This confirms cooling rate effects on sperm cryosurvival depend on inter-individual boar differences more than on the cooling process itself.  相似文献   
132.
目的深入探讨腹主动脉阻断术的临床原理及其高中低位阻断安全时限等问题,以期在临床上安全地使用该技术。方法1980年-1982年我们首次进行了腹主动脉阻断安全时限及其阻断与撤钳后病理生理变化的前瞻性实验研究。结果表明:犬腹主动脉阻断25min为安全时限;在阻断安全时限内,犬体内血液动力学、血气酸碱、血液生化和主要的脏器超微结构(脑肺肝肾胰肠脊髓)仅发生轻度可逆性改变;如超出安全时限,上述指标则会发生难以代偿的严重改变。基于广义生命时空场论学说,通过对腹主动脉阻断术解剖学基础,腹主动脉阻断后与撤钳后综合征群(呼吸宭迫综合征、急性高血压性脑水肿、多脏器微栓塞病细胞综合征、撤钳后中枢性呼吸衰竭)及腹主动脉阻断所致的缺血再灌注损伤病理生理与细胞分子生物学机制等讨论,并根据近期实验与临床研究结果和结合文献复习对相关问题做了探讨,对临床上预防和治疗腹主动脉阻断术所致的缺血再灌注损伤提出了一整套对策。此外还叙述了预防腹主动脉阻断术并发症的远端主动脉灌注、脑脊液引流以及硬膜外冷却、控制性再灌注与缺血预/后处理等几种新技术。结果如果超出腹主动脉阻断术安全时限,则在术中与术后将发生缺血再灌注损伤、全身炎症反应综合征和多脏器衰竭。临床上,人类一次性持续腹主动脉阻断术安全时限如下:高位(T12水平,腹腔干A上)、中位(L2水平,肾A上)与低位(L4水平,髂总A上)均不能轻易超越25-30min。如术中须延时宁可采用间断阻断法。结论如果"二叉树耐受法则"(即体内任何一处大血管阻断均不能超出其固有安全时限,否则受术者非死必伤)被严格遵守,则腹主动脉阻断术中与术后病人的安全将得到保证。  相似文献   
133.
Introduction: A left atrioesophageal fistula is an uncommon but devastating complication that may occur during atrial fibrillation (AF) ablation, and may be due to thermal injury occurring during the radiofrequency (RF) ablation. We examined the feasibility of an esophageal cooling (ECO) method using a cooled water-irrigated intraesophageal balloon (IB).
Methods and Results: Eight patients with drug-refractory AF underwent RF catheter ablation to encircle the ipsilateral pulmonary veins. During the RF ablation at the posterior left atrium, the esophageal lumen was cooled using a 9-Fr. IB catheter with a balloon length of 40 mm and diameter of 10 mm, in which cooled water, with a water temperature of 4.5 ± 3.1 °C, was irrigated while the luminal esophageal temperature (LET) was measured with an intraesophageal probe placed at a site close to the tip of the ablation catheter. In the control, the LET increased from 36.4 ± 0.8 °C to 40.5 ± 1.7 °C within 26.1 ± 8.2 seconds during 3.9 ± 1.2 RF energy applications, whereas with the ECO the LET decreased to 30.2 ± 2.9 °C at baseline (P<0.01 vs control), and increased only to 33.5 ± 2.9 °C (P<0.01 vs control) at most, within 30 seconds during 3.9 ± 1.2 RF energy applications. All pulmonary veins were successfully isolated in all patients without any complications. During a follow-up period of 3.1 ± 1.2 months, no esophageal injuries were observed and all but one patient have been free from any symptoms.
Conclusions: Use of an IB successfully lowers LET. This might have the potential of preventing esophageal injury, although further study is required.  相似文献   
134.
‘Local module’ is a fundamental functional unit of the central nervous system that can be defined as the minimal portion of one or more neurons and/or one or more glial cells that operates as an independent integrative unit. This review focuses on the importance of neurotransmitter receptor heteromers for the operation of local modules. To illustrate this, we use the striatal spine module (SSM), comprised of the dendritic spine of the medium spiny neuron (MSN), its glutamatergic and dopaminergic terminals and astroglial processes. The SSM is found in the striatum, and although aspects such as neurotransmitters and receptors will be specific to the SSM, some general principles should apply to any local module in the brain. The analysis of some of the receptor heteromers in the SSM shows that receptor heteromerization is associated with particular elaborated functions in this local module. Adenosine A2A receptor–dopamine D2 receptor–glutamate metabotropic mGlu5 receptor heteromers are located adjacent to the glutamatergic synapse of the dendritic spine of the enkephalin MSN, and their cross-talk within the receptor heteromers helps to modulate postsynaptic plastic changes at the glutamatergic synapse. A1 receptor–A2A receptor heteromers are found in the glutamatergic terminals and the molecular cross-talk between the two receptors in the heteromer helps to modulate glutamate release. Finally, dopamine D2 receptor–non-α7 nicotinic acetylcholine receptor heteromers, which are located in dopaminergic terminals, introduce the new concept of autoreceptor heteromer.  相似文献   
135.
136.
目的通过两组不同的物理降温方法比较,探讨中药退热洗剂擦浴对外感高热的降温及护理效果。方法将68例患者随机分为退热洗剂擦浴治疗组和酒精擦浴对照组,两组患者均给予常规中西医结合治疗,治疗组在以上治疗的同时加用中药洗剂擦浴.对照组给予35%的酒精擦浴。在擦浴后分别测量30min、60min、90min后的体温,并与擦浴前所测的体温进行对比。结果在擦浴后30分钟时中药擦浴组的疗效低于酒精擦浴对照组(P〈0.os);在擦浴后60分钟时,两组的退热效果相当(尸〉0.05);在擦浴后90分钟时中药擦浴组的疗效优于酒精擦浴对照组(P〈0.05)。结论中药退热洗剂擦浴对外感高热症具有良好的降温效果。  相似文献   
137.
目的:探讨养血脱敏汤治疗过敏性紫癜的疗效.方法:将90例患者随机分成两组:对照组均采取病因治疗、控制感染、中断与过敏原的接触、肾上腺皮质激素、抗组织胺制剂、改善血管脆性及对症治疗;治疗组在对照组基础上加服自拟养血脱敏汤,日1剂,早晚2次,水煎服.结果:治疗组有效率93.3%,对照组有效率75.6%,两组比较差异具有显著性(P<0.05),治疗组明显优于对照组.结论:养血脱敏汤对过敏性紫癜具有满意疗效,值得推广应用.  相似文献   
138.
Objectives – To evaluate the feasibility and safety of head‐neck cooling in conscious normal volunteers (10) and patients with medically refractory epilepsy (5) without causing shivering. Patients and methods – We used a non‐invasive head‐neck cooling system (CoolSystems Inc., Lincoln, CA, USA). The tympanic temperature (TT) and intestinal temperature (IT) were measured as two measurements of ‘core temperature’ (CT), and multi‐site external temperatures, several physiologic variables and EEG were monitored. Seizure counts over 4‐week precooling, treatment and follow‐up phases were compared. Results – All 15 participants completed all the cooling sessions without significant complaints. At the end of 60 min of cooling, scalp temperature fell on average by 12.2°C (P < 0.001), TT by 1.67°C (P < 0.001), and IT by 0.12°C (P = NS). Average weekly seizure frequency decreased from 2.7 to 1.7 events per patient per week (MANOVA: P < 0.05). Conclusions – Non‐invasive head‐neck cooling is safe and well‐tolerated. Initial pilot data in patients suggest that additional therapeutic studies are warranted.  相似文献   
139.
Xerosis represents a physiological response of the stratum corneum (SC) to environmental threats. The influence of the environmental dew point (DP) is not fully understood. This parameter is the air temperature at which the relative humidity is maximum. This study aimed to assess the relationship between the environmental DP and the water‐holding capacity of the skin and lower lip vermilion. For comparison, SC property was evaluated after occlusive application of cooled and uncooled hydrogel pads. Electrometric measurements using a dermal phase meter (DPM) device were performed on the back of the hands, the cheeks and the lower lip of 40 healthy menopausal women. Assessments were performed in the outdoor conditions during winter and spring. The same measurements were recorded after hydrogel pads, at room temperature or cooled to 4 °C, were placed for 15 min on the test sites. The environmental DP was recorded at each evaluation time. The SC water‐holding capacity was discretely influenced by the DP. In the open‐air environmental conditions, a positive linear relationship was found on the cheeks between the DP and DPM values. The relationship was weaker on the lips. Conversely, a consistent increase in DPM values was recorded immediately after removal of the cooled and uncooled hydrogel pads. The observations made in the open‐air testing conditions are consistent with the predicted events following the Arrhenius law. By contrast, the combination of cooling and occlusion by the hydrogel pads is responsible for the reverse effect on the SC.  相似文献   
140.
ABSTRACT

Current approaches to QEEG-guided neurofeedback involve efforts to normalize the abnormalities seen, without reference to the functional localization of the cortical areas involved. Recent advances in cortical neurophysiology indicate that specific brain areas are developed to perform certain functions (cortical modules). Complex brain functions require cooperation between modules, particularly during a learning situation. For example, the left prefrontal “activation module” must cooperate with one or both occipital “visual modules” to attend and see something on a chalkboard. To remember what has been seen, both temporal “memory modules” must cooperate with the visual modules for the image to be retained in short-term memory. If the connections between these modules are not functioning optimally, visual learning will be impaired. Decreased coherence (hypocoherence) indicates a decrease in functional connectivity between these modules, and increased coherence (hypercoherence) indicates an increase in functional connectivity between the modules. Neurofeedback can be used to normalize coherence between these modules, thereby improving the efficiency of their cooperation in the learning process. If coherence is less than normal, it is trained up. If coherence is more than normal, it is trained down. Three cases are presented where this approach has succeeded in remediating the client's symptoms.  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