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   82493篇
  免费   5819篇
  国内免费   3738篇
耳鼻咽喉   348篇
儿科学   1481篇
妇产科学   847篇
基础医学   13057篇
口腔科学   1663篇
临床医学   6920篇
内科学   14403篇
皮肤病学   1027篇
神经病学   7729篇
特种医学   1314篇
外国民族医学   15篇
外科学   4847篇
综合类   13932篇
现状与发展   22篇
预防医学   4921篇
眼科学   967篇
药学   10561篇
  11篇
中国医学   2595篇
肿瘤学   5390篇
  2024年   179篇
  2023年   873篇
  2022年   2217篇
  2021年   3020篇
  2020年   2418篇
  2019年   2068篇
  2018年   2036篇
  2017年   2345篇
  2016年   2671篇
  2015年   3019篇
  2014年   5070篇
  2013年   5685篇
  2012年   5374篇
  2011年   6000篇
  2010年   4756篇
  2009年   4612篇
  2008年   4751篇
  2007年   4605篇
  2006年   4128篇
  2005年   3881篇
  2004年   3175篇
  2003年   2710篇
  2002年   2073篇
  2001年   1784篇
  2000年   1541篇
  1999年   1319篇
  1998年   1224篇
  1997年   1072篇
  1996年   917篇
  1995年   730篇
  1994年   704篇
  1993年   586篇
  1992年   505篇
  1991年   474篇
  1990年   394篇
  1989年   311篇
  1988年   296篇
  1987年   286篇
  1986年   256篇
  1985年   361篇
  1984年   317篇
  1983年   210篇
  1982年   244篇
  1981年   191篇
  1980年   164篇
  1979年   109篇
  1978年   91篇
  1977年   77篇
  1976年   67篇
  1975年   53篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
人PD-L2基因克隆及其在大肠杆菌中的表达   总被引:1,自引:1,他引:0  
目的 克隆人PD-L2基因并构建PD-L2胞外区的原核表达载体,在大肠杆菌中进行表达。方法 以RT-PCR方法从活化的人外周血单个核细胞总RNA中克隆PD-L2基因的cDNA,构建PD-L2胞外区的原核表达载体,在大肠杆菌BL21(ED3)中进行表达并鉴定。结果 克隆到PD-L2基因cDNA编码区全长序列,经DNA测序证明其与已报道的序列一致。进而构建了PD-L2胞外区的原核表达载体,并在大肠杆菌表达,免疫印迹分析表明在IPTG诱导后表达PD-L2胞外区蛋白,相对分子质量Mr为22000,与理论值大小相符。结论 成功克隆PD-L2基因,其胞外区蛋白在大肠杆菌中获得表达,为进一步研究PD-L2功能提供了条件。  相似文献   
82.
目的 探讨军人花粉症治疗的有效方法。方法 采用提高起始浓度和快速递增浓度 ,上臂外侧皮下注射的方法对 10 6位军人花粉症患者行快速免疫治疗 ,并对每一位患者治疗前后检测血清中总IgE和嗜酸细胞阳离子蛋白 (ECP)。 结果 治疗前后患者总IgE和ECP值有显著性差异。 10 6例患者经 1~ 3年随访复查 ,78例 2个以上发病季节未发作 ,或仅有轻微鼻痒、眼痒 ,18例症状减轻 ,发病时间缩短半月 ,10例症状无明显改善。显效 82例 ,有效 14例 ,无效 10例 ,总有效率为 90 .5 7%。结论 快速免疫治疗能使患者血清总IgE和ECP下降 ,对军人花粉症疗效好。  相似文献   
83.
Prostaglandin E1 (PGE1) has several potential therapeutic effects, including cytoprotection, vasodilation, and inhibition of platelet aggregation. This study investigates the protective action of PGE1 against hepatic ischemia/reperfusion injury in vivo using a complementary DNA microarray. PGE1 or saline was continuously administered intravenously to mice in which the left lobe of the liver was made ischemic for 30 minutes and then reperfused. Livers were harvested 0, 10, and 30 minutes postreperfusion. Messenger RNA was extracted, and the samples were labeled with two different fluorescent dyes and hybridized to the RIKEN set of 18,816 full-length enriched mouse complementary DNA microarrays. Serum alanine aminotransferase and aspartate aminotransferase levels at 180 minutes postreperfusion were significantly lower in the PGE1-treated group than in the saline-treated group. The cDNA microarray analysis revealed that the genes encoding heat-shock protein (HSP) 70, glucose-regulated protein 78, HSP86, and glutathione S-transferase were upregulated at the end of the ischemic period (0 minutes postreperfusion) in the PGE1 group. Our results suggested that PGE1 induces HSPs immediately after ischemia reperfusion. HSPs might therefore play an important role in the protective effects of PGE1 against ischemia/reperfusion injury of the liver.  相似文献   
84.
胆固醇通过分布于十二指肠和近段空肠黏膜上皮细胞刷状缘膜的Niemann—Pick C1样蛋白1摄取,ATP结合盒G5、G8抑制小肠对胆固醇的摄取过程。进入上皮细胞的胆固醇大多数被乙酰辅酶A,胆固醇转乙酰基酶2酯化,随后通过组装形成乳糜微粒,经淋巴管进入血循环;另一部分胆固醇则以未酯化形式直接进入血循环形成高密度脂蛋白颗粒。这些过程受核受体——肝脏X受体的调控。年龄、性别、黏膜屏障和小肠传输速度也影响胆固醇的吸收。  相似文献   
85.
谢福权  崔德威 《医学综述》2008,14(9):1326-1328
穹窿体是真核细胞中的核糖核蛋白颗粒,由肺耐药蛋白、穹窿体多聚腺苷二磷酸聚合酶、端粒酶相关蛋白和穹窿体RNA构成,其主要成分为肺耐药蛋白。肺耐药蛋白是介导肿瘤多药耐药的蛋白之一,可能与肿瘤的治疗效果和临床预后相关。穹窿体可能通过介导药物转运或者信号转导引起肿瘤的多药耐药。文章介绍了穹窿体的结构、成分及其介导多药耐药机制研究的新进展。  相似文献   
86.
Two embryonal CNS tumors, atypical teratoid/rabdoid tumor (AT/RT) and primitive neuroectodermal tumor (PNET), may be confused with each other and misdiagnosed. Here we report an infant with a congenital supratentorial tumor, which was detected by fetal MRI at 37 weeks gestation. On routine histological examination, the tumor was composed mainly of small undifferentiated cells, among which many rhabdoid cells and occasional sickle‐shaped embracing cells were observed. No mesenchymal or epithelial areas were evident. Our impression was that the tumor was an atypical example of AT/RT. Immunohistochemically, almost all the tumor cells were strongly positive for vimentin. However, epithelial membrane antigen was notably negative, and most of the tumor cell nuclei were clearly positive for INI1. In addition, many tumor cells were positive for neurofilament protein. There were also occasional small areas containing many tumor cells positive for glial fibrillary acidic protein. Finally, a diagnosis of PNET, with a rhabdoid phenotype and expression of neuronal and glial markers, was made. In the present case, application of INI1 immunostaining was very helpful for distinguishing PNET from AT/RT.  相似文献   
87.
BACKGROUND: Although there is increasing evidence suggesting that the vagus nerve functions as a connector between the nervous and immune systems in animals, little is known about the role of the vagus nerve in postoperative acute phase response in humans. MATERIALS AND METHODS: The extent of fever and acute phase protein response and the production of inflammatory cytokine during the early postoperative period were compared among the patients who had undergone total gastrectomy including truncal vagotomy (n = 13), those having distal gastrectomy with division of vagal branches (n = 14), and the patients with vagal nerve preserving gastrectomy (n = 12). RESULTS: There was no significant difference in serum levels of C-reactive protein, alpha-1-antirypsin, and interleukin-6 among the three groups. Also, postoperative maximum body temperature was similar. CONCLUSIONS: Vagotomy did not influence acute phase response after gastric cancer surgery. A multipathway mechanism for acute phase response including the induction of fever is suggested.  相似文献   
88.
In mycophenolate mofetil (MMF)-treated organ transplant recipients, lower mycophenolic acid (MPA) plasma concentrations have been found in cyclosporine (CsA) compared with tacrolimus (Tac)-based immunosuppressive regimens. We previously demonstrated that CsA decreases exposure to MPA and increases exposure to its metabolite MPA-glucuronide (MPAG), possibly by interfering with the biliary excretion of MPAG. To elucidate the role of the multidrug resistance-associated protein (Mrp)-2 in the interaction between MMF and CsA, we treated three groups of 10 Mrp2-deficient rats (TR- rat) for 6 days with either vehicle, CsA (8 mg/kg) or Tac (4 mg/kg) by oral gavage. Hereafter, co-administration with MMF (20 mg/kg) was started in all groups and continued through day 14. The 24-h MPA/MPAG area under the concentration-time curve (AUC) was determined after single (day 7) and multiple MMF doses (day 14). On both study days, there were no significant differences in the mean MPA and MPAG AUC between CsA and Tac-treated animals. We conclude that the pharmacokinetics of MMF are comparable in Mrp2-deficient rats receiving either CsA or Tac as co-medication. This finding suggests that CsA-mediated inhibition of the biliary excretion of MPAG by the Mrp2 transporter is the mechanism responsible for the interaction between CsA and MMF.  相似文献   
89.
BACKGROUND/PURPOSE: If the occlusion time of a closed chamber evaporimeter on the skin is too long, saturation might occur. We previously compared an open chamber and a closed chamber device on healthy volunteers. Comparable data on stripped skin with higher evaporation rates are not available. This study compares the sensitivity and correlation of open and closed chamber devices in a tape-stripping human model. The amount of tape removed SC was also quantified with a protein assay method. METHODS: Ten healthy volunteers (six male and four female; seven Caucasians and three Asian; mean age 38+/-16) were enrolled. In a randomized manner, one forearm was measured by an open chamber device and the opposite by a closed chamber device. After recording baseline measurements, 20 strippings were taken on each test site with tape disks. Transepidermal water loss (TEWL) was measured at the end of 10 and 20 tape strippings at each test site. Stratum corneum (SC) aggregates in the strips was assayed. RESULTS: The mean values obtained from two devices were similar after 10 trips and 20 strips. There was no statistically significant difference. The closed chamber device showed a slightly higher (but not significant) inter-individual coefficient of variation. SC aggregates in the strips were similar and without a statistically significant difference. CONCLUSION: The study suggests that both devices might yield similar TEWL values on stripped human skin in vivo.  相似文献   
90.
The response of periodontal nerves to experimentally induced occlusal trauma in rat molars was assessed by immunohistochemistry for protein gene product 9.5 (PGP 9.5) at light and electron microscopic levels, and by computerized image analysis. The occlusal surface on the left upper first molar of 8-wk-old male Wistar rats was raised approximately 1 min under ether anaesthesia. The rats were perfusion-fixed on d 1, 2, 3, 4, and 7 after bite-raising and then decalcified for 2–3 wk. Frozen sagittal cryostat sections were stained by the avidin-biotin complex method. By the second day after bite-raising many Ruffini endings were swollen and their outline unclear at the light microscopic level. Transmission electron microscopy disclosed PGP 9.5 reaction products within Ruffini endings that had unusually long cytoplasmic projections extending through enlarged slits of the Schwann sheaths and also diffuse extracellular PGP 9.5-immunoreactivity near the Ruffini endings. From d 2 to 4, thin nerve fibres on the pressure side of the periodontal ligament were orientated irregularly and had a prominent beaded appearance. An increase in beaded nerve terminals occurred at d 2–4 post elevation, and decreased later. These results suggest that occlusal trauma induces specific changes in the distribution and shape of nerve terminals in the periodontal ligament.  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