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   1709篇
  免费   112篇
  国内免费   120篇
耳鼻咽喉   29篇
儿科学   83篇
妇产科学   48篇
基础医学   144篇
口腔科学   32篇
临床医学   273篇
内科学   335篇
皮肤病学   81篇
神经病学   110篇
特种医学   113篇
外科学   228篇
综合类   62篇
预防医学   165篇
眼科学   52篇
药学   130篇
中国医学   4篇
肿瘤学   52篇
  2021年   22篇
  2020年   17篇
  2019年   33篇
  2018年   35篇
  2017年   23篇
  2016年   30篇
  2015年   43篇
  2014年   50篇
  2013年   78篇
  2012年   67篇
  2011年   70篇
  2010年   51篇
  2009年   64篇
  2008年   52篇
  2007年   111篇
  2006年   77篇
  2005年   53篇
  2004年   43篇
  2003年   36篇
  2002年   39篇
  2001年   39篇
  2000年   47篇
  1999年   48篇
  1998年   57篇
  1997年   40篇
  1996年   39篇
  1995年   31篇
  1994年   27篇
  1993年   25篇
  1992年   31篇
  1991年   35篇
  1990年   26篇
  1989年   46篇
  1988年   45篇
  1987年   37篇
  1986年   31篇
  1985年   27篇
  1983年   16篇
  1981年   14篇
  1980年   13篇
  1979年   19篇
  1976年   14篇
  1975年   14篇
  1974年   22篇
  1973年   13篇
  1972年   12篇
  1971年   16篇
  1968年   16篇
  1966年   13篇
  1958年   15篇
排序方式: 共有1941条查询结果,搜索用时 0 毫秒
21.
Objective To construct a eukaryotic expression system with pcDNA3-PfCSP/Hela for the Circ umsporozoite protein (CSP) gene of Plasmodium falciparum (P.falciparum), t o observe the immune responses in BALB/c mice induced by the expressed proteins .Methods The recombinant plasmid pcDNA3-PfCSP was transformed into the Hela cell line. The expressed protein was isolated and analyzed by using SDS-PAGE and used for immunization of BALB/c mice by subcutaneous, intravenous, and intraperitone al adminstration.Enzyme-linked immunosorbent assay(ELISA), Dot-ELISA, Wester n blot, T lymphocyte proliferation test, natural killer cell(NKC) activity assay , and CD4(+) and CD8(+) T cell detection were used for observation of humoral an d cellular immune responses.Results Immune sera strongly reacted with the expressed protein, antibody titer was up to 1∶6400 as detected by ELISA.Western blot analysis revealed a specific b and at 38.3 Kda.When the spleen cells of normal and immunized BALB/c mice we re specifically stimulated with expressed protein, the optical densities were 0 .12±0.03 and 0.34±0.04, respectively.The latter were significantly highe r than the former (P<0.01).We used the MTT colorimetric assay to measure NKC activity of mice spleen.The results showed that the NKC activity of immuni zed BALB/c mice was remarkably higher than that of the controls (P<0.05). CD4(+) and CD8(+) T cells were detected by using monoclonal antibody immunofluor escence methods.The results showed that the percentage of CD4(+) and CD8(+) T cells of immunized group were significantly higher than that of control group ( P<0.05).Conclusions The humoral and cell-mediated immune responses and elevated NKC activity to pr oducts made with a eukaryotic expression system could be specifically detected i n BALB/c mice.These findings indicate that the expressed protein could enhance the immune function in mice.  相似文献   
22.
0 引言 我科 1996 / 1998分别应用消痔灵与强的松龙混合液、消痔灵液、强的松龙液行鼻息肉内 ,鼻息肉蒂部注射治疗鼻息肉各 5 0例 ,并设对照组为鼻腔滴入及口服类固醇激素 5 0例 ,合计 2 0 0例 ,观察并对比其疗效 .1 对象和方法1.1 对象 男 12 8例 ,女 72例 ,年龄 8~ 78(平均 38)岁 ,病程 32 a~ 45 (平均 4.5 ) a.其中在本次治疗前做过一次鼻息肉摘除术后复发的 2 7例 ,做过 2次或 2次以上手术的 12例 .主要症状为鼻塞、流脓涕、头痛及嗅觉减退 .全部病例治疗前均行鼻窦 X线拍片 ,其中上颌窦炎 12 5例、筛窦炎 5 8例、蝶窦炎 2例、…  相似文献   
23.
BACKGROUND: Conventional cardiopulmonary resuscitation (CPR) includes 80-100/min precordial compressions with intermittent positive pressure ventilation (IPPV) after every fifth compression. To prevent gastric insufflation, chest compressions are held during IPPV if the patient is not intubated. Elimination of IPPV would simplify CPR and might offer physiologic advantages, but compression-induced ventilation without IPPV has been shown to result in hypercapnia. The authors hypothesized that application of continuous positive airway pressure (CPAP) might increase CO2 elimination during chest compressions. METHODS: After appropriate instrumentation and measurement of baseline data, ventricular fibrillation was induced in 18 pigs. Conventional CPR was performed as a control (CPR(C)) for 5 min. Pauses were then discontinued, and animals were assigned randomly to receive alternate trials of uninterrupted chest compressions at a rate of 80/min without IPPV, either at atmospheric airway pressure (CPR(ATM)) or with CPAP (CPR(CPAP)). CPAP was adjusted to produce a minute ventilation of 75% of the animal's baseline ventilation. Data were summarized as mean +/- SD and compared with Student t test for paired observations. RESULTS: During CPR without IPPV, CPAP decreased PaCO2 (55+/-28 vs. 100+/-16 mmHg) and increased SaO2 (0.86+/-0.19 vs. 0.50+/-0.18%; P < 0.001). CPAP also increased arteriovenous oxygen content difference (10.7+/-3.1 vs. 5.5+/-2.3 ml/dl blood) and CO2 elimination (120+/-20 vs. 12+/-20 ml/min; P < 0.01). Differences between CPR(CPAP) and CPR(ATM) in aortic blood pressure, cardiac output, and stroke volume were not significant. CONCLUSIONS: Mechanical ventilation may not be necessary during CPR as long as CPAP is applied. Discontinuation of IPPV will simplify CPR and may offer physiologic advantage.  相似文献   
24.
Presenting various stimuli in an MRI scanner can be difficult due to the high magnetic field associated with the scanner. Mechanical vibration stimuli are difficult to deliver to subjects in the MRI environment because most vibration devices contain internal circuitry that can adversely interact with the high magnetic field. Piezoelectric ceramics can provide a solution to this problem since they do not require any internal circuitry to vibrate. Piezoceramics are nonmagnetic and they can be made to vibrate if supplied with an alternating current from a straight wire. We designed a piezoceramic vibrotactile stimulator that is safe and effective in functional MRI experiments. The stimulator was tested in an fMRI experiment at 35 and 150 Hz. The results yielded activation sites in the primary sensory cortex and Brodmann area 40 at both frequencies.  相似文献   
25.
Skin tumors induced in mice by initiation-promotion (2 microg DMBA-2 microg TPA) protocols were found to be under multigenic control. Eighty- one N2 mice from the cross (BALB/cAnPt x SENCARA/Pt)F1 x SENCARA/Pt that were either solidly resistant (no papillomas) or highly susceptible (> or = 7 papillomas/mouse) were subjected to a 'genome scan' using 89 microsatellite markers to check for associations with susceptible and resistant phenotypes. A locus on Chr 5 (Skts4) was found to control the susceptibility of SENCARA/Pt mice and the resistance of BALB/cAnPt mice to papilloma formation. In addition, higher than expected linkage scores were seen for the markers D9Mit271, D11Mit268 and D12Mit56. Further work is required to establish whether genes determining papilloma formation are located in these regions of the genome. In general, no evidence was seen for loss of heterozygosity in microsatellite markers on Chrs 5, 9 and 11 in 17 microdissected papillomas from (BALB/c x SENCARA)F1 hybrid mice.   相似文献   
26.
报道了用GC/MS方法及衍生化技术研究6甲氧基正丁苯酞(MBP)在大鼠肝微粒体中的代谢转化结果。6甲氧基正丁苯酞在苯巴比妥(PB)诱导的大鼠肝微粒体中主要转化为3羟基、γ羟基取代物,6羟基正丁苯酞与一个环氧化代谢产物  相似文献   
27.
目的了解笔者所在医院2008年度临床感染病原菌的菌种分布及其耐药现状。方法用VITEK微生物自动鉴定仪鉴定菌种,纸片扩散法检测临床分离菌对各种抗菌药物的敏感性,判读标准参照当年的CLSI M100文件。结果临床分离的1900株病原菌中革兰阴性杆菌、革兰阳性球菌和真菌所占比例分别为68.42%、18.16%和12.32%。分离率最高的五种病原菌:铜绿假单胞菌、大肠埃希菌、肺炎克雷伯菌、鲍曼不动杆菌和白色假丝酵母菌,占所有分离病原菌的59.26%,排前20位的病原菌则占到近90%(89.63%)。革兰阴性杆菌仅对亚胺培南、头孢哌酮/舒巴坦、美洛培南、哌拉西林/他唑巴坦的平均耐药率低于30%,铜绿假单胞菌和鲍曼不动杆菌对亚胺培南、美洛培南的耐药率分别28.9%、32.9%和11.6%、24.7%,大肠埃希菌、肺炎克雷伯菌和奇异变形杆菌的ESBL阳性率分别是52.8%、37.2%和34.6%,金黄色葡萄球和凝固酶阴性葡萄球菌中耐甲氧西林株各占44.0%和60.0%,未检出万古霉素中介或耐药的葡萄球菌,检出万古霉素耐药的粪肠球菌和屎肠球菌各1株。念珠菌对氟康唑耐药率接近5%。结论临床感染病原菌构成变化不大,但真菌检出率逐年升高。非发酵菌耐药率最低的是头孢哌酮/舒巴坦,肠杆菌科耐药率最低的是亚胺培南,ESBL的阳性率逐年升高。加强病原菌及其耐药性检测和监测,对病原学诊断及指导合理选用抗生素具重要参考价值。  相似文献   
28.
羧乙基锗倍半氧化物(Ge—132)能促进培养乳鼠心肌细胞DNA和RNA的合成,提高超氧化物歧化酶(SOD)的活性,维持细胞膜结构的稳定。异丙基肾上腺素可使心肌细胞乳酸脱氢酶(LDH)释放增加,细胞搏动停止,超微结构显示肌膜和线粒体严重受损。Ge—132可显著减少异两基肾上腺素引起心肌细胞释放LDH,维持细胞的搏动功能和超微结构的完整。  相似文献   
29.
本文报道我国西南产麻黄——丽江麻黄Ephedra likiangensis Florin、匍枝丽江麻黄E.likiangensis f.mairei(Florin)C.Y.Cheng、藏麻黄E.saxatilis Royle ex Florin、山岭麻黄E.gerardiana Wall、垫状山岭麻黄E.gerardiana Var.congesta C.Y.Cheng、矮麻黄E.minuta Florin和异株矮麻黄E.minuta var.dioeca C.Y.Cheng,以及形态组织特征较特殊的宁夏产斑子麻黄E.lepidosperma C.Y.Cheng、新疆产窄膜麻黄E.lomatolepis Schrenk,西藏产西藏中麻黄E.intermedia var.tibetica Stapf的生药形态组织学研究结果。并根据对国产麻黄的生药形态组织学的系统研究结果,分别编写了各种国产麻黄(包括13种3变种1变型)的生药性状和生药显微特征检索表。  相似文献   
30.
用Boc-和Tos-基团分别保护氨基和侧链胍基,以1%交联度聚苯乙烯二苯甲氨基树脂为载体,用DCC固相法合成肽,HF断裂肽树脂键和去除侧链保护基团,粗产物经高效液相层析纯化,合成了心肌兴奋肽Phe-Met-Arg-Phe-NH_2及其类似物Phe-Pro-Arg-Phe-NH_2,并观察了此二种肽对大鼠血压和心率的影响。  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