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   4117篇
  免费   175篇
  国内免费   91篇
耳鼻咽喉   6篇
儿科学   5篇
妇产科学   14篇
基础医学   317篇
口腔科学   23篇
临床医学   163篇
内科学   293篇
皮肤病学   21篇
神经病学   310篇
特种医学   100篇
外科学   109篇
综合类   936篇
预防医学   354篇
眼科学   26篇
药学   911篇
中国医学   742篇
肿瘤学   53篇
  2024年   3篇
  2023年   14篇
  2022年   9篇
  2021年   25篇
  2020年   36篇
  2019年   42篇
  2018年   78篇
  2017年   59篇
  2016年   82篇
  2015年   65篇
  2014年   162篇
  2013年   179篇
  2012年   267篇
  2011年   375篇
  2010年   277篇
  2009年   268篇
  2008年   254篇
  2007年   284篇
  2006年   243篇
  2005年   236篇
  2004年   194篇
  2003年   183篇
  2002年   173篇
  2001年   116篇
  2000年   112篇
  1999年   109篇
  1998年   81篇
  1997年   85篇
  1996年   82篇
  1995年   62篇
  1994年   63篇
  1993年   42篇
  1992年   28篇
  1991年   27篇
  1990年   15篇
  1989年   13篇
  1988年   4篇
  1987年   3篇
  1986年   3篇
  1985年   7篇
  1984年   11篇
  1983年   2篇
  1982年   2篇
  1981年   6篇
  1978年   1篇
  1976年   1篇
排序方式: 共有4383条查询结果,搜索用时 15 毫秒
31.
Diffusion magnetic resonance imaging (MRI) exhibits contrast that identifies macro‐ and microstructural changes in neurodegenerative diseases. Previous studies have shown that MR diffusion tensor imaging (DTI) can observe changes in spinal cord white matter in animals and humans affected with symptomatic amyotrophic lateral sclerosis (ALS). The goal of this preclinical work was to investigate the sensitivity of DTI for the detection of signs of tissue damage before symptoms appear. High‐field MRI data were acquired using a 9.4‐T animal scanner to examine the spinal cord of an ALS mouse model at pre‐ and post‐symptomatic stages (days 80 and 120, respectively). The MRI results were validated using yellow fluorescent protein (YFP) via optical microscopy of spinal cord tissue slices collected from the YFP,G93A‐SOD1 mouse strain. DTI maps of diffusion‐weighted imaging (DWI) signal intensity, mean diffusivity (MD), fractional anisotropy (FA), axial diffusivity (AD) and radial diffusivity (RD) were computed for axial slices of the lumbar region of the spinal cord. Significant changes were observed in FA (6.7% decrease, p < 0.01), AD (19.5% decrease, p < 0.01) and RD (16.1% increase, p < 0.001) at postnatal day 80 (P80). These differences were correlated with changes in axonal fluorescence intensity and membrane cellular markers. This study demonstrates the value of DTI as a potential tool to detect the underlying pathological progression associated with ALS, and may accelerate the discovery of therapeutic strategies for patients with this disease.  相似文献   
32.
Arimoclomol, an amplifier of heat shock protein expression involved in cellular stress response, has emerged as a potential therapeutic candidate in amyotrophic lateral sclerosis (ALS) in recent years. Treatment with arimoclomol was reported to improve survival and muscle function in a mouse model of motor neuron disease. Several single- and multiple-dose safety studies have been completed in healthy control subjects. A 3-month Phase IIa study in people with ALS demonstrated safety at dosages up to 300 mg/day and another study is currently recruiting participants with familial ALS caused by mutations in the superoxide dismutase gene. We review the rationale for testing arimoclomol in sporadic and familial ALS in the context of available safety and pharmacokinetic data. Published and unpublished literature relative to the drug in the past two decades is discussed. The current review attempts to bring together our existing understanding of the actions of arimoclomol with the disease profile of ALS. The pharmacological profile of arimoclomol and the available preclinical data make it a promising therapeutic possibility in ALS.  相似文献   
33.
34.
目的研究复方健耳剂对小鼠耳蜗组织超氧化物歧化酶(SOD)1表达的影响,探讨其预防老年性耳蜗感音神经性损害机制。方法选择断奶DBA/2J小鼠10只,随机分为对照组和中药组各5只,对照组小鼠为常规饲料与日常饮水喂养;中药组小鼠为常规饲料与中药溶液喂养;至4.3月龄时两组同时终止实验,取出耳蜗,利用Real Time PCR技术定量检测两组耳蜗组织SOD1的表达。结果中药组SOD1的表达比对照组高(P<0.05)。结论复方健耳剂通过对SOD1的表达影响可能是其有效对抗老年性耳蜗感音神经性损害的重要机制之一。  相似文献   
35.
《Neurological research》2013,35(8):693-702
Abstract

Objectives:

In the SOD1G93A mouse model of amyotrophic lateral sclerosis (ALS), a selective degeneration of fast-fatigable motor units and consequently an early decline of contractile force in individual fast-twitch muscles have been observed in the preclinical stage. However, most human muscles include fast and slow motor units. Gastrocnemius-soleus group (GS) contains such a mixture of units.

Methods:

We have investigated changes in the mechanical properties of GS at different SOD1G93A stages in mice. For this purpose, the tibial nerve was repetitively stimulated with rectangular pulses and the force of GS twitches was recorded using a strain gauge fixed to the Achilles tendon.

Results:

Isometric and tetanic force were attenuated but not before the first clinical signs developed. However, already at preclinical stages, single twitches showed a slower decay compared to control. Consequently, fusion of GS twitches occurred at lower stimulus rates. Furthermore, already preclinically, the temporal course of successive twitch amplitudes changed during repetitive stimulation at increasing rates. The peak amplitudes as well as the potentiation following decay (fatigue) were lower in preclinical mice than in control.

Discussion:

The time-lapse analysis of the contractile pattern as well as of the twitch configuration of the mixed muscle GS have revealed distinctive differences between wild-type controls and preclinical SOD1G93A mice. It would be of interest to know whether these preclinical changes are also detectable in ALS patients.  相似文献   
36.
Primary liver cancer or hepatocellular carcinoma (HCC) is one of the most frequent tumors representing the fifth commonest malignancy worldwide and the third cause of mortality from cancer. Currently, the treatments for HCC are not so effective and new strategies are needed for its fight. Chemoprevention, the use of natural or synthetic chemical agents to reverse, suppress or prevent carcinogenesis is considered an important way for confronting HCC. Many of the chemopreventive agents are phytochemicals, namely non-nutritive plant chemicals with protective or disease preventive properties. In this review, we focus on plant polyphenols, one of the most important classes of phytochemicals, their chemopreventive properties against HCC and discuss the molecular mechanisms accounting for this activity.  相似文献   
37.
Human gastric diseases have shown significant changes in the activity and expression of superoxide dismutase (SOD) isoforms. The aim of this study was to detect Mn‐SOD activity and expression in the tissue of gastric mucosa, primarily in chronic gastritis (immunohistochemical Helicobacter pylori‐negative gastritis, without other pathohistological changes) and to evaluate their possible connection with pathohistological diagnosis. We examined 51 consecutive outpatients undergoing endoscopy for upper gastrointestinal symptoms. Patients were classified based on their histopathological examinations and divided into three groups: 51 patients (archive samples between 2004–2009) with chronic immunohistochemical Helicobacter pylori‐negative gastritis (mononuclear cells infiltration were graded as absent, moderate, severe) divided into three groups. Severity of gastritis was graded according to the updated Sydney system. Gastric tissue samples were used to determine the expression of Mn‐SOD with anti‐Mn‐SOD Ab immunohistochemically. The Mn‐SOD expression was more frequently present in specimens with severe and moderate inflammation of gastric mucosa than in those with normal mucosa. In patients with normal histological finding, positive immunoreactivity of Mn‐SOD was not found. Our results determine the changes in Mn‐SOD expression occurring in the normal gastric mucosa that had undergone changes in the intensity of chronic inflammatory infiltrates in the lamina propria.  相似文献   
38.
目的探讨金水宝胶囊联合依帕司他片治疗糖尿病肾病的临床疗效。方法选取2014年9月—2017年4月商丘市第一人民医院收治的糖尿病肾病患者172例,随机分为对照组和治疗组,每组各86例。对照组口服依帕司他片,50 mg/次,1次/d。治疗组在对照组治疗的基础上口服金水宝胶囊,3粒/次,3次/d。两组患者均连续治疗8周。观察两组的临床疗效,比较两组的血糖、肾功能指标、24 h尿微量蛋白定量、血清氧化指标和血清抗氧化指标。结果治疗后,对照组和治疗组的总有效率分别为75.6%、93.0%,两组比较差异有统计学意义(P0.05)。治疗后,两组空腹血糖、糖化血红蛋白水平均显著降低,同组治疗前后比较差异有统计学意义(P0.05);且治疗组血糖指标明显低于对照组,两组比较差异具有统计学意义(P0.05)。治疗后,两组血清肌酐(Scr)、尿素氮(BUN)、胱抑素C(Cys-C)、血清β2微球蛋白(β2-MG)、24 h尿微量蛋白定量、尿蛋白排泄率(UAER)水平均显著降低,同组治疗前后比较差异有统计学意义(P0.05);且治疗组这些观察指标明显低于对照组,两组比较差异具有统计学意义(P0.05)。治疗后,两组活性氧(ROS)、脂质过氧化氢(LHP)和晚期蛋白氧化产物(AOPPS)水平均显著下降,同组治疗前后比较差异有统计学意义(P0.05);且治疗组血清氧化指标明显低于对照组,两组比较差异具有统计学意义(P0.05)。治疗后,两组超氧化物歧化酶(SOD)、维生素E(VitE)、维生素C(VitC)和总抗氧化能力(T-AOC)水平均显著升高,同组治疗前后比较差异有统计学意义(P0.05);且治疗组血清抗氧化指标明显高于对照组,两组比较差异具有统计学意义(P0.05)。结论金水宝胶囊联合依帕司他片治疗糖尿病肾病具有较好的临床疗效,可改善肾功能,增强抗氧化能力,降低氧化反应,具有一定临床推广应用价值。  相似文献   
39.
目的考察海马补肾丸对小鼠学习记忆障碍的改善作用,并探讨其作用机制。方法小鼠随机分为对照组、模型组、吡拉西坦组、龟龄集组和海马补肾丸组。采用腹腔注射东莨菪碱制备小鼠记忆获得性障碍模型,计算学习正确率,测定蛋白含量和乙酰胆碱酯酶活力。采用腹腔注射亚硝酸钠制备小鼠记忆巩固性障碍模型,计算训练、测定学习正确率,测定蛋白含量、去甲肾上腺素(NE)、多巴胺(DA)、5-羟色胺(5-HT)以及丙二醛(MDA)、超氧化物歧化酶(SOD)含量。结果海马补肾丸2.20 g/kg组能显著增加小鼠学习记忆的正确率(P0.05),显著降低乙酰胆碱酯酶活力(P0.01)。测定时,与模型组比较,海马补肾丸1.10、2.20 g/kg组能显著增加小鼠学习记忆正确率(P0.05),能不同程度增加小鼠大脑SOD含量,降低MDA含量(P0.05、0.01)。结论海马补肾丸能明显改善小鼠的记忆获得、记忆巩固障碍,推测其作用机制主要是通过降低乙酰胆碱酯酶活性,增加脑内乙酰胆碱的含量,改善记忆获得能力;通过抗脑组织的氧化损伤,增加大脑SOD含量,降低MDA含量,改善记忆巩固能力。  相似文献   
40.
目的探讨胃得安胶囊联合兰索拉唑治疗胃溃疡的临床效果。方法选取2016年7月—2018年7月天津市第五中心医院收治的胃溃疡患者96例,随机分成对照组(48例)和治疗组(48例)。对照组早餐前30 min口服兰索拉唑肠溶胶囊,30 mg/次,1次/d。治疗组在对照组基础上口服胃得安胶囊,2粒/次,3次/d。两组患者均连续治疗6周。观察两组患者临床疗效,同时比较治疗前后两组患者上腹痛评分、反酸评分、前列腺素(PG)E2、C反应蛋白(CRP)、白介素-17(IL-17)、超氧化物歧化酶(SOD)和脂质过氧化物(LPO)水平以及幽门螺杆菌根除率、溃疡愈合率及复发率。结果治疗后,对照组临床有效率为87.5%,显著低于治疗组的100.0%,两组比较差异有统计学意义(P0.05)。治疗后,两组患者中上腹痛评分和反酸评分均显著降低(P0.05),且治疗组患者中上腹痛评分和反酸评分明显低于对照组(P0.05)。治疗后,两组患者胃液中PGE2浓度及血清SOD水平均显著升高(P0.05),血清CRP、IL-17、LPO浓度则均显著降低(P0.05),且治疗组患者这些指标水平明显好于对照组(P0.05)。治疗后,治疗组幽门螺杆菌根除率、溃疡愈合率分别为93.8%、75.0%,均显著高于对照组(P0.05)。随访6个月,治疗组复发率为8.3%,比对照组的25%明显显著降低(P0.05)。结论胃得安胶囊联合兰索拉唑治疗胃溃疡的整体疗效切实,促进溃疡愈合,增强胃黏膜的防御功能及机体的抗氧化能力。  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