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   23370篇
  免费   2432篇
  国内免费   1546篇
耳鼻咽喉   157篇
儿科学   381篇
妇产科学   255篇
基础医学   2935篇
口腔科学   349篇
临床医学   3159篇
内科学   3622篇
皮肤病学   218篇
神经病学   1547篇
特种医学   985篇
外国民族医学   20篇
外科学   2137篇
综合类   3558篇
现状与发展   5篇
一般理论   5篇
预防医学   1419篇
眼科学   821篇
药学   2523篇
  34篇
中国医学   1404篇
肿瘤学   1814篇
  2024年   96篇
  2023年   401篇
  2022年   1067篇
  2021年   1327篇
  2020年   987篇
  2019年   872篇
  2018年   908篇
  2017年   741篇
  2016年   740篇
  2015年   1012篇
  2014年   1396篇
  2013年   1130篇
  2012年   1680篇
  2011年   1760篇
  2010年   1076篇
  2009年   912篇
  2008年   1134篇
  2007年   1109篇
  2006年   1192篇
  2005年   1075篇
  2004年   685篇
  2003年   730篇
  2002年   609篇
  2001年   462篇
  2000年   582篇
  1999年   563篇
  1998年   368篇
  1997年   374篇
  1996年   274篇
  1995年   251篇
  1994年   209篇
  1993年   127篇
  1992年   202篇
  1991年   143篇
  1990年   132篇
  1989年   104篇
  1988年   109篇
  1987年   99篇
  1986年   97篇
  1985年   78篇
  1984年   38篇
  1983年   29篇
  1982年   24篇
  1979年   35篇
  1974年   35篇
  1973年   27篇
  1970年   24篇
  1969年   31篇
  1967年   29篇
  1966年   30篇
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
41.
Objective To examine the protective effects of hydroxysafflor yellow A (HSYA) against the senescence of mesenchymal stem cells (MSCs) induced by D-galactose (D-gal) in vitro, and investigate the potential mechanism involved. Methods Grouping experiment, Normal control (NC) group: conventional culture with complete medium; Senescence group: MSCs were cultured for 48 h with complete medium containing 10 g/L D-gal; HSYA group: on the basis of senescence induction, HSYA with the suitable concentration was used to protect MSCs. The key experimental indices associated with oxidative stress, inflammatory response, cell senescence, proliferation and apoptosis were measured through chemical colorimetry, β-galactosidase staining, EdU incorporation and flow cytometry, respectively. The relative quantity (RQ) of proteins related closely to cell proliferation, apoptosis, and NF-κB signaling were measured by Western blotting. Results As compared with Senescence group, treatment with HSYA (120 mg/L) effectively ameliorated the adverse situation of MSCs. Oxidation stress and inflammation along with D-Gal induction was dramatically alleviated in MSCs; The β-Gal-positive staining indicated that MSC senescence was significantly mitigated; The proliferative capability of MSCs was significantly increased by up-regulating PCNA and inhibiting p16 expression; The anti-apoptotic effect on MSCs was exerted by down-regulating the RQ of cleaved Caspase-3 and Bax; The activity of NF-κB signaling in MSCs was notably suppressed through inhibiting phosphorylation of IKKβ and p65. Conclusion HSYA (120 mg/L) significantly delayed the D-Gal-induced senescence process in MSCs through attenuating inflammatory reaction and oxidative stress, and suppressing the activity of NF-κB signaling.  相似文献   
42.
Hepatic ischemia–reperfusion injury (HIRI) is of common occurrence during liver surgery and transplantation. Pinocembrin (PIN) is a kind of flavonoid monomer extracted from the local traditional Chinese medicine Penthorum chinense Pursh (P. chinense). However, the effect of PIN on HIRI has not determined. We investigated the protective effect and potential mechanism of PIN against HIRI. Model mice were subjected to partial liver ischemia for 60 min, experimental mice were pretreated with PIN orally for 7 days, and H2O2-induced oxidative damage model in AML12 hepatic cells was established in vitro. Histopathologic analysis and serum biochemical levels revealed that PIN had hepatoprotective activities against HIRI. The variation of GSH, SOD, MDA, and ROS levels indicated that PIN treatments attenuated oxidative stress in tissue. PIN pretreatment obviously ameliorated apoptosis, and restrained the expression of HMGB1 and TLR4 in vivo. In vitro, compared with H2O2 group, the contents of ROS, mitochondrial membrane potential, apoptotic cells, and Bcl-2 protein were decreased, while the Bax protein expression was increased. Moreover, HMGB-1 small interfering RNA test and western blotting showed that PIN pretreatment reduced HMGB1 and TLR4 protein levels. In conclusion, PIN pretreatment effectively protected hepatocytes from HIRI and inhibited the HMGB1/TLR4 signaling pathway.  相似文献   
43.

In this study, exposure experiments were conducted to assess the effects of polystyrene nanoparticles (PS) and amine-modified polystyrene nanoparticles (APS) at environmental concentrations (1, 10, and 100 µg L??1) on two fungal species (Geotrichum candidum and Aspergillus niger), isolated from leaf litter in streams, concerning their growth and metabolic activity. Results showed that PS at 1 and 10 µg L??1 have hormesis effects on G. candidum growth. Compared with G. candidum, A. niger had higher sensitivity to nanoplastic exposure. Besides, the peroxidase and cellobiohydrolase activities of A. niger were significantly inhibited by nanoplastics (except 1 µg L??1 PS), which would weaken its metabolic activity in carbon cycling. These results provided a new thought on how the growth and functions of aquatic fungi cope with the stress induced by nanoplastics. Overall, the study provided evidence for the different responses of aquatic fungi to nanoplastics in streams.

  相似文献   
44.
45.
46.
47.
BACKGROUND: Chinese herbal medicine has a long history of human use. A novel herbal formula, anti-asthma herbal medicine intervention (ASHMI), has been shown to be an effective therapy in a murine model of allergic asthma. OBJECTIVE: This study was undertaken to compare the efficacy, safety, and immunomodulatory effects of ASHMI treatment in patients with moderate-severe, persistent asthma with prednisone therapy. METHODS: In a double-blind trial, 91 subjects underwent randomization. Forty-five subjects received oral ASHMI capsules and prednisone placebo tablets (ASHMI group) and 46 subjects received oral prednisone tablets and ASHMI placebo capsules (prednisone group) for 4 weeks. Spirometry measurements; symptom scores; side effects; and serum cortisol, cytokine, and IgE levels were evaluated before and after treatment. RESULTS: Posttreatment lung function was significantly improved in both groups as shown by increased FEV(1) and peak expiratory flow findings (P<.001). The improvement was slightly but significantly greater in the prednisone group (P<.05). Clinical symptom scores, use of beta(2)-bronchodilators, and serum IgE levels were reduced significantly, and to a similar degree in both groups (P<.001). T(H)2 cytokine levels were significantly reduced in both treated groups (P<.001) and were lower in the prednisone-treated group (P<.05). Serum IFN-gamma and cortisol levels were significantly decreased in the prednisone group (P<.001) but significantly increased in the ASHMI group (P<.001). No severe side effects were observed in either group. CONCLUSION: Anti-asthma herbal medicine intervention appears to be a safe and effective alternative medicine for treating asthma. In contrast with prednisone, ASHMI had no adverse effect on adrenal function and had a beneficial effect on T(H)1 and T(H)2 balance.  相似文献   
48.
儿童臀肌挛缩症免疫发病机理的研究   总被引:4,自引:0,他引:4  
本文对41例儿童臀肌挛缩症患者外周血及32例儿童臀肌挛缩症臀肌进行了系统的免疫学研究。结果表明:儿童臀肌挛缩症患者免疫调节功能紊乱,红细胞免疫功能低下,臀肌组织免疫复合物沉积,臀肌小血管数目减少及管壁损伤。由此认为免疫病理因素是儿童臀肌挛缩症的主要发病机理。  相似文献   
49.
目的 :研究孕激素受体拮抗剂米索前列醇对妊娠晚期引产的效果。方法 :采用双盲对照法 ,选择晚期妊娠无米索前列醇禁忌证 6 0例为研究组 ,采用阴道给药总量 1 0 0mg ;另选择有关参数相同的 6 0例 ,应用催产素 ,两组观察相关指标体系进行比较。结果 :引产效果 ,分娩时间 ,宫颈评分等指标研究组均优于对照组。结论 :米索前列醇用于晚期妊娠引产效果优 ,安全  相似文献   
50.
重视校级教学研究课题的组织与实施   总被引:1,自引:0,他引:1  
在高等教育教学改革的进程中 ,校级教学研究课题的组织与实施值得重视与加强。校级教学研究课题参与人数多 ,课题设计的自主性、针对性较强 ,有利于形成高校整体的教学研究氛围 ,直接促进教学改革的发展和教学效益的提高。本文对校级教学研究课题的特点及组织、实施中应注意的导向作一探讨 ,阐明校级教学研究课题在方法上应注意科学性 ,内容上应注重先进教学手段 ,结题时应注意具体、物化的成果形式。  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