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   44084篇
  免费   3913篇
  国内免费   3037篇
耳鼻咽喉   368篇
儿科学   679篇
妇产科学   629篇
基础医学   5524篇
口腔科学   712篇
临床医学   5793篇
内科学   7051篇
皮肤病学   470篇
神经病学   2769篇
特种医学   1402篇
外国民族医学   17篇
外科学   4829篇
综合类   6907篇
现状与发展   6篇
一般理论   7篇
预防医学   2611篇
眼科学   1198篇
药学   4419篇
  33篇
中国医学   1926篇
肿瘤学   3684篇
  2024年   86篇
  2023年   619篇
  2022年   982篇
  2021年   2195篇
  2020年   1621篇
  2019年   1556篇
  2018年   1618篇
  2017年   1398篇
  2016年   1302篇
  2015年   1940篇
  2014年   2412篇
  2013年   2188篇
  2012年   3255篇
  2011年   3499篇
  2010年   2086篇
  2009年   1712篇
  2008年   2356篇
  2007年   2403篇
  2006年   2252篇
  2005年   2255篇
  2004年   1543篇
  2003年   1499篇
  2002年   1259篇
  2001年   1118篇
  2000年   1143篇
  1999年   1249篇
  1998年   662篇
  1997年   723篇
  1996年   546篇
  1995年   490篇
  1994年   414篇
  1993年   301篇
  1992年   369篇
  1991年   321篇
  1990年   271篇
  1989年   238篇
  1988年   222篇
  1987年   186篇
  1986年   169篇
  1985年   125篇
  1984年   69篇
  1983年   78篇
  1982年   47篇
  1981年   53篇
  1980年   29篇
  1979年   44篇
  1978年   20篇
  1977年   17篇
  1974年   18篇
  1973年   16篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
NT-proBNP的检测在急性心肌梗死中的应用   总被引:3,自引:0,他引:3  
目的探讨N末端B型脑钠尿肽(NT-proBNP)在急性心肌梗死(AMI)患者的临床应用价值。方法应用电化学发光法检测急性ST段抬高型心肌梗塞患者53例血中NT-proBNP的水平变化,分析其与心功能分级的关系。对照组为健康体检者24例,均已排除心、脑血管疾病。结果急性ST段抬高型心肌梗塞患者血中NT-proBNP水平显著高于正常心功能对照组(P〈0.01)。患病组心功能≥Ⅱ级组血NT-proBNP显著高于心功能Ⅰ级组,心功能Ⅰ~Ⅳ级患者组各组间血清NT-proBNP水平差异均有统计学意义(P〈0.01),随着心功能级数递增,NT-proBNP水平增高。NT-proBNP与Killip分级呈正相关。结论AMI后心脏钠尿肽系统激活,其改变与心功能损伤程度有关,因此NT-proBNP的测定可为临床诊断提供依据。  相似文献   
82.
Purpose Post operative monitoring is crucial for the success of microsurgical free tissue transfer. Sophisticated and expensive methods are available for monitoring. We propose a novel technique using digital photography and the internet as a reliable and cost effective method to monitor free tissue transfers. Methods 163 micro‐vascular procedures were monitored using this technique over 8 months. Serial photographs taken to show flap color. Capillary refill time, pin prick‐ bleed time and color and hand held Doppler signal was recorded in the movie mode of a standard 5 mega pixel camera with duration of 15 seconds. Data was sent to the surgeon at regular intervals and or as deemed necessary. Results Analysis of the 67 cases is presented. 5 re‐explorations were done. The early diagnosis of venous congestion was possible using this technique. Timely intervention contributed to the success of the re‐explorations and these flaps could be salvaged. The file size of images was in the range of 1 MB–6 MB. The file size of an entire set of images ranged about 7 MB–9 MB. These were sent across the ADSL internet lines. Conclusion The use of the digital images and the internet allow reconstructive surgeons to have a reliable picture of the state of their free tissue transfers. This permits decrease in observer error and saves valuable time which otherwise needs to be spent to verify situations of doubt and offers an ideal solution to the logistic problem of having to visit the patient in case of doubt.  相似文献   
83.
目的 探讨实时双平面超声心动图的临床应用价值。方法 对 83例受检者进行实时双平面超声 (BP)检查 ,其中男 46例 ,女 3 7例 ,平均年龄 2 0 92± 19 16岁。正常人 10例 ,先天性心脏病 44例 ,心瓣膜病 2 6例 ,其他心脏病变3例。结果 实时双平面超声有助于理解心脏立体解剖 ;能通过有限的声窗获得更多的切面 ,并可显示常规经胸超声不易得到的切面 ;多切面显示心脏瓣膜及其病变 ,有利于获得瓣膜狭窄或关闭不全的最佳观察平面 ;多切面显示房、室间隔缺损 ,便于寻找缺损的最佳显示切面以及与毗邻结构的关系。房、室间隔缺损BP、2DE测值与手术测值均有良好相关性 ;室间隔缺损BP测值与手术测值无显著性差异 ;BP、2DE均有低估房间隔缺损大小的倾向。实时双平面超声能同时显示复杂先心病的多种解剖畸形 ,有利于确定房室连接 ;辨认主、肺动脉。结论 实时双平面超声有其独特的优势 ,可为心血管疾病的准确诊断提供更多的信息。  相似文献   
84.
目的 检测 4 9例肝外胆管癌和 10例正常胆管Bcl 2和Bax的表达。方法 免疫组化ABC法。结果 Bcl 2在胆管癌中阳性表达 (48.98% )显著高于正常胆管 (10 .0 0 % ) (P <0 .0 5 ) ;高、中分化胆管癌Bcl 2阳性表达显著高于低分化癌 (P <0 .0 5 ) ;胆管癌Bax阳性表达 (5 3.0 6 % )与正常胆管 (80 .0 0 % )相比无统计学意义 (P >0 .0 5 ) ,正常胆管Bax阳性表达显著高于Bcl 2阳性表达 (P<0 .0 1) ,而胆管癌中Bcl 2与Bax阳性表达无显著性差异 (P >0 .0 5 )。结论 Bcl 2过度表达对胆管癌的发生可能起促进作用 ;胆管癌中Bcl 2低表达可能是预后不良的预测指标之一。  相似文献   
85.
目的 探讨全直肠系膜切除术在预防直肠癌术后局部复发中的作用 ,以及同该操作相关的一些并发症。方法 回顾性分析 16 8例直肠癌的临床资料。结果 全组无手术死亡 ,术后随访1~ 36月 ,局部复发 6例 (3.6 % ) ,术后吻合口漏 13例 (10 .7% ) ,多数保肛患者出现便频、便急等症状。结论 全直肠系膜切除术能有效降低直肠癌术后局部复发率 ,提高保肛率 ,但存在吻合口漏 ,控便功能等问题需进一步解决。  相似文献   
86.
对冠心病心绞痛中医证候规律研究类的文献,从证候要素分布的差异、主要证候分类的差异、证候要素与理化指标的相关研究等方面进行比较分析,初步认为本病的证候要素应证组合是以气虚、血瘀为中心,阴虚、痰浊为次中心,气滞、阳虚、热蕴为外围所组成的多层次的证候体系。  相似文献   
87.
88.
Polycyclic aromatic hydrocarbons (PAH), of which benzo[a]pyrene is a representative member, are combustion-related environmental pollutants and include known carcinogens. Laboratory animal studies indicate that the dose of PAHs to the fetus is on the order of a 10th that to the mother and that there is heightened susceptibility to PAH-induced carcinogenesis during the fetal and infancy periods. Carcinogen-DNA adducts, a measure of procarcinogenic genetic damage, are considered a biomarker of increased cancer risk. Here we compare the levels of benzo[a]pyrene-DNA adducts as a proxy for PAH-DNA damage measured in maternal blood and newborn cord blood obtained at delivery in four different populations of mothers (total of 867) and newborns (total of 822), representing a 30-fold range of exposure to ambient PAHs. The populations include residents in Northern Manhattan, participants in a study of the effects of the World Trade Center disaster, residents in Krakow, Poland, and residents in Tongliang, China. Mean adduct concentrations in both maternal and cord blood and the proportion of samples with detectable adducts, increased across the populations [Northern Manhattan < World Trade Center (WTC) < Krakow < Tongliang], consistent with the trend in estimated ambient exposure to PAHs (P < 0.001). For mothers, the means in the respective populations were Northern Manhattan (0.21 adducts per 10(8) nucleotides), WTC (0.23 adducts per 10(8) nucleotides), Krakow (0.28 adducts per 10(8) nucleotides), Tongliang (0.31 adducts per 10(8) nucleotides); the corresponding means in the newborns were Northern Manhattan (0.23), WTC (0.24), Krakow (0.29), Tongliang (0.31). The percentage of mothers with detectable levels of adducts in the respective populations were Northern Manhattan (36.8%), WTC (57.5%), Krakow (72.9%), Tongliang (73.4%); the corresponding percentages among the newborns were Northern Manhattan (42.4%), WTC (60.6%), Krakow (71.1%), Tongliang (79.5%). Despite the estimated 10-fold lower PAH dose to the fetus based on laboratory animal experiments, the adduct levels in the newborns were similar to or higher than in the mothers. This study suggests that the fetus may be 10-fold more susceptible to DNA damage than the mother and that in utero exposure to polycyclic aromatic hydrocarbons may disproportionately increase carcinogenic risk. The data support preventive policies to limit PAH exposure to pregnant women and children.  相似文献   
89.
亚急性甲状腺炎的CT诊断   总被引:4,自引:1,他引:3  
目的:探讨亚急性甲状腺炎的CT表现和特点,提高对该病影像表现的认识。材料和方法:回顾性分析10例亚急性甲状腺炎CT影像特征及临床资料,共16个病灶,其中9例经手术病理证实,1例临床证实。同时抽取局限型甲状腺癌65例,就部分征象作对照分析。结果:亚急性甲状腺炎局限性3例,弥漫性7例。CT表现分3型:①局限于甲状腺一侧叶的低密度病变,病变甲状腺肿大,峡部可受累,3例;②甲状腺两叶各有一低密度病变,呈不对称肿大,病灶之间有正常甲状腺组织,6例共12个病灶;③甲状腺两叶及岬部均匀肿大,略不对称,1例。CT平扫病变为低密度,增强扫描后呈轻到中度均匀强化(15/16),腺内更低密度结节少见(1/16)。病变处甲状腺边缘模糊(16/16),与正常甲状腺组织界限不清(15/16),而局限型甲状腺癌病灶与正常甲状腺腺组织分界清楚(62/65),两者极不一样(P<0.01)。结论:亚急性甲状腺炎CT表现有一定特点,熟悉这些特点对于诊断及鉴别诊断很有帮助。  相似文献   
90.
The natural history of lamivudine-resistant hepatitis B virus (HBV) infection in renal transplant recipients (RTx) is unclear, despite its increasing incidence. Twenty-nine HBsAg-positive RTx with rising HBV DNA received lamivudine therapy. The course of lamivudine-resistant HBV infection was studied prospectively. During 68.7 +/- 12.5 months of follow-up, 14 (48.3%) patients developed lamivudine resistance, at 10-35 months (mean 16.9 +/- 7.0). All showed mutant sequences at codons 552 and 528 of the YMDD motif, while 13 patients demonstrated wild-type sequence at codon 555. Lamivudine resistance was unrelated to patient demographics, HBeAg status/sero-conversion, or genotype. Following resistance, HBV DNA and alanine aminotransferase showed an initial increase followed by spontaneous gradual reduction. The subsequent peak HBV DNA was lower (1.26 +/- 1.09 x 10(9) vs. 6.26 +/- 12.23 x 10(9) copies/mL, p = 0.011), while that of alanine aminotransferase was higher (196 +/- 117 vs. 77 +/- 47 imicro/l, p = 0.005), compared with pretreatment levels. Post-resistance hepatitic flare occurred in 11 (78.6%) patients. This was transient in four (36.4%), but became chronic in six (54.5%) patients. Decompensation was noted in one patient during this flare, but all survived. We conclude that drug resistance is prevalent in lamivudine-treated RTx. Despite a lower ensuing peak viremia compared with baseline, hepatitic flare is common. While most patients have spontaneous resolution, a minority may develop potentially fatal decompensation during the preceding exacerbation.  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