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   48266篇
  免费   4599篇
  国内免费   3734篇
耳鼻咽喉   320篇
儿科学   380篇
妇产科学   444篇
基础医学   5716篇
口腔科学   727篇
临床医学   6663篇
内科学   6957篇
皮肤病学   495篇
神经病学   2489篇
特种医学   1964篇
外国民族医学   34篇
外科学   4997篇
综合类   8659篇
现状与发展   15篇
一般理论   5篇
预防医学   3126篇
眼科学   1373篇
药学   5200篇
  57篇
中国医学   2831篇
肿瘤学   4147篇
  2024年   188篇
  2023年   862篇
  2022年   2326篇
  2021年   2785篇
  2020年   2114篇
  2019年   1739篇
  2018年   1768篇
  2017年   1688篇
  2016年   1562篇
  2015年   2287篇
  2014年   2911篇
  2013年   2538篇
  2012年   3744篇
  2011年   3951篇
  2010年   2450篇
  2009年   1877篇
  2008年   2405篇
  2007年   2373篇
  2006年   2390篇
  2005年   2180篇
  2004年   1514篇
  2003年   1528篇
  2002年   1372篇
  2001年   1096篇
  2000年   1158篇
  1999年   1132篇
  1998年   743篇
  1997年   690篇
  1996年   475篇
  1995年   477篇
  1994年   438篇
  1993年   266篇
  1992年   291篇
  1991年   289篇
  1990年   171篇
  1989年   170篇
  1988年   162篇
  1987年   149篇
  1986年   97篇
  1985年   65篇
  1984年   62篇
  1983年   38篇
  1982年   23篇
  1981年   19篇
  1980年   9篇
  1979年   19篇
  1978年   3篇
  1972年   2篇
  1970年   1篇
  1968年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
用微量马桑内酯注入Wistar大鼠左侧前肢运动皮质,造成急性局灶型癫痫。用光镜、电镜和体视学方法研究其运动皮质第V层结构的改变。结果显示:癫痫大鼠运动皮质灶区、灶旁区的神经细胞数和胶质细胞数均分别比对照大鼠灶区和灶旁区显著减少;灶区神经毡中突触性终末数,显著减少;突触性终末的面积分数明显减少,而树突的面积分数无变化;神经胶质突起的面积分数增加。  相似文献   
62.
Background. Heparin bonding of the cardiopulmonary bypass (CPB) circuit may be associated with a reduced inflammatory response and improved clinical outcome. The relative contribution of a heparin-bonded oxygenator (ie, >80% of circuit surface area) to these effects was assessed in a group of pediatric patients.

Methods. Twenty-one pediatric patients undergoing CPB operations were assigned randomly to receive either a heparin-bonded oxygenator (group H, n = 11) or a nonbonded oxygenator (group C, n = 10) in otherwise nonbonded circuits. The two groups were similar in pathology, age, weight, CPB time, and cross-clamp time. Plasma levels of the cytokines tumor necrosis factor-, interleukin-6, and interleukin-8, as well as terminal complement complex, neutrophils, and elastase, were analyzed before, during, and after CPB.

Results. Significant levels of tumor necrosis factor- were not detected in either group. Plasma levels of all other markers increased during and after CPB compared with baseline. Plasma levels of interleukin-6 peaked in both groups 2 hours after the administration of protamine but remained significantly higher in group C 24 hours after operation. Plasma concentrations of interleukin-8 peaked at similar levels in both groups 30 minutes after protamine administration and returned to baseline thereafter. Levels of terminal complement complex and elastase peaked in both groups 30 minutes after protamine administration. Plasma levels of terminal complement complex were significantly higher at the end of CPB and after protamine administration in group C. Elastase levels were significantly higher 2 and 24 hours after CPB in group C. The ventilation time of patients in group H was significantly lower than that of patients in group C: 10 (range, 3 to 24) versus 22 (range, 7 to 24) hours, respectively (p < 0.01).

Conclusions. The present study confirms the proinflammatory nature of pediatric operations and demonstrates a lessened systemic inflammatory response with the use of heparin-bonded oxygenators. This is achieved without bonding of the entire circuit, which could have significant cost-benefit implications by negating the need for custom-built heparin-bonded circuitry.  相似文献   

63.
目的:探讨一氧化氮(NO)与先天性心脏病(CHD)引起的肺动脉高压(PH)发病间的关系。方法:应用NO试剂盒检测了CHD患儿肺动脉及上腔静脉血浆中NO含量。结果;(1)伴PH组肺动脉血浆NO含量明显高于不伴肺动脉高压组(37.58±9.99μmol/L:19.03±15.25μmol/L,P<0.01);(2)在PH组中,肺动脉血浆NO含量明显高于上腔静脉血(P<0.01);而不伴PH组,肺动脉和上腔静脉血浆NO含量无显著性差异(P>0.05)。结论:(1)伴PH的先心患儿肺动脉血浆NO含量升高;(2)NO可能介入了CHD引起的PH发病过程。  相似文献   
64.
目的:探讨螺旋CT血管造影(Spiral CT angiography,SCTA)技术,以期提高SCTA造影的质量。材料与方法:采用Somatom Plus 4螺旋CT扫描系统对10例病人行腹部SCTA检查。扫描技术和造影剂参数按病变范围和性质而定,三维重建采用最大强度投影法(MIP)或表面阴影显示法(SSD)或弯曲平面重建法(CPR)。结果:SCTA检查技术能可靠地显示血管形态和病变,评价腹部肿瘤与邻近血管关系。结论:SCTA是无创伤性的血管成像术,在很大范围可替代创伤性的血管造影。  相似文献   
65.
预防艾滋病健康教育媒体材料效果评价比较研究   总被引:6,自引:2,他引:4  
目的评价4种预防艾滋病健康教育媒体材料的信息传播效果和材料效果。该材料由课题组于2003-2005年间设计制作,包括“艾滋病知识”折页、“了解艾滋病”海报、“预防艾滋病健康教育手册”和“认识艾滋病”宣教片等4种。方法2005年12月在珠海市选取小学以上文化程度的18~60岁外来工为测试对象,随机分组对4种材料分别进行评价,各调查了251、248、257和252人,共1008人。通过问卷调查了解受访者的一般情况和对材料信息的可接受性、通俗性和材料形式的生动性等8项指标的评价,采用分级定量赋分的方法进行量化评分,采用SPSS10.1统计软件进行统计分析、比较。结果4种材料的信息传播效果和材料效果总得分平均值分别为74.2±15.0、77.7±13.5、73.0±13.8和77.2±13.6,得分最高的是海报,为77.7±13.5分,最低的是手册,为73.0±13.8分,差异有统计学意义,这种差异主要体现在信息传播效果的差异,而材料效果的差异无统计学意义。通俗性、简明性、生动性和可接受性是影响得分高低的主要因素。结论海报是最适合用于城市外来工进行预防艾滋病健康教育的传播材料,其次是宣教片。  相似文献   
66.
急性传染性非典型肺炎的影像表现   总被引:1,自引:0,他引:1  
目的探讨急性传染性非典型肺炎(SARS)的X线表现及变化规律.方法回顾性分析临床诊断SARS的61例患者,对发病后的一系列胸片和CT影像进行统计分析.结果患者以发热为最早起病症状,88.5%患者在起病1周内肺部出现肺局灶性斑片状模糊影,并迅速扩大.2周内病变达高峰,有57.4%患者两肺大部分肺野受累,病情重.83.6%患者在5周内肺部阴影逐渐消散.在恢复期16例CT扫描中,有13例显示肺部遗留纤维化病灶.有6例患者合并感染,病期延长,4例死亡.结论SARS早期出现肺部炎性改变,发展迅速,大部分两肺受累,重症比例高,易致肺纤维化.  相似文献   
67.
Introduction There is now increasing evidence that proximal tubular cells (PTCs) contribute to renal interstitial fibrosis by alteration of matrix turnover and by the generation of pro‐fibrotic cytokines such as TGF‐β1. Recent studies suggest that, through a process of transdifferentiation, the PTCs are one source of the interstitial myofibroblasts that directly drive the fibrotic process. The aim of this work was to examine the role and mechanism by which TGF‐β1 may regulate PTC phenotype and function. Methods Experiments were performed using both primary‐cultures of PTC and the human PTC cell line HK2. All experiments were performed on growth‐arrested cells in the absence of serum. Results TGF‐β1 altered cell phenotype, assessed by light microscopy, with cells appearing elongated and spindle‐shaped. This was associated with loss of cell–cell contact and rearrangement of the actin cytoskeleton, increased formation of stress fibres and focal adhesions. Disruption of the actin cytoskeleton with cytochalasin‐D prevented phenotypic alterations following addition of TGF‐β1. Transient transfection with Smad‐2/‐4 or Smad‐3/‐4 expression vectors did not alter cell phenotype. Previously, we have demonstrated β‐catenin translocation to PTC nuclei and its association with Smad proteins following addition of TGF‐β1, suggesting the possibility that TGF‐β1 may modulate Wnt signalling. Wnt‐responsive Xtwn‐reporter construct was, however, silent in response to TGF‐β1. Similarly, a second Wnt‐/LEF‐1‐regulated element Toplflash, which does not contain Smad‐binding sites, was insensitive to TGF‐β1 signalling. In contrast, phenotypic changes in response to TGF‐β1 were abrogated by inhibitors of the RhoA downstream target ROCK, which also prevented loss of cell–cell contact and adherens junction disassembly. Removal of TGF‐β1 and addition of 1% FCS, however, reverted cell phenotype to a typical cobblestone epitheliod appearance, suggesting that TGF‐β1 did not result in terminal PTC transdifferentiation. Cells grown on tissue culture dishes coated with either type‐I or type‐III collagen also acquired an elongated fibroblastic phenotype; this effect was exaggerated by the addition of TGF‐β1. In contrast to the cells stimulated with TGF‐β1 alone, following stimulation by both TGF‐β1 and exposure to interstitial collagens, cell phenotype was stable in that it was not reversed upon removal of TGF‐β1 and addition of FCS. Addition of TGF‐β1 to cells grown on type‐IV collagen had no greater effect than TGF‐β1 alone. Addition of TGF‐β1 alone had little effect on the expression of α‐SMA. In contrast, cells grown on either type‐I or type‐III collagen, following addition of TGF‐β1, demonstrated marked increased expression of α‐SMA, which appeared to be incorporated into the cell cytoskeleton. Similarly, the combination of interstitial collagen (either type‐I or type‐III) and TGF‐β1 had synergistic effect on the relocation and down‐regulation of the epithelial markers E‐cadherin and cytokeratin. Finally, the results demonstrated synergistic effects of coating with interstitial collagen (either type‐I or type‐III), on cell ‘fibroblastic’ cell function as assessed by cell migration and by the synthesis of type‐III and type‐IV collagen. Conclusion The results of these in vitro experiments suggest that terminal transdifferentiation of proximal tubular epithelial cells is the result of a combination of the effects of the pro‐fibrotic cytokine TGF‐β1 and exposure of the cells to components of the interstitial extra‐cellular matrix to which the cells are not exposed in the absence of damage to the tubular basement membrane.  相似文献   
68.
[目的]探讨切除侵犯中颅窝的咽旁颞下区巨大肿瘤安全而彻底的手术进路.利用颞部切口可充分暴露中颅窝底和颞下窝以及颌下进路显露咽旁区解剖的特点,联合进路切除2例咽旁颞下区巨大肿瘤.2例侵犯中颅窝底的咽旁颞下区肿瘤顺利切除,患者术中组织损伤、出血量相对较少,术后无严重并发症.[结论]颞部-颌下联合进路适合于侵犯中颅窝底的咽旁颞下区肿瘤的手术切除.  相似文献   
69.
Inactivated whole avian influenza virus (AIV) vaccine provides protection against homologous haemagglutinin (HA) subtype virus, but poor protection against a heterologous HA virus. Moreover, it induces chickens to produce antibodies to cross-reactive antigens, especially nucleoprotein, which is limits AIV serological surveillance. In this study, a recombinant fowlpox virus co-expressing HA (H5 subtype) and NA (N1 subtype) genes of AIV was evaluated for its ability to protect chickens against intramuscular challenge with a lethal dose of highly pathogenic (HP) AIV. Susceptible chickens were also vaccinated by wing-web puncture with the parent fowlpox vaccine virus. Following challenge 4 weeks later with HPAIV, all chickens vaccinated with recombinant virus were protected, while the chickens vaccinated with either the unaltered parent fowlpox vaccine virus or unvaccinated controls experienced 100% mortality following challenge. This protection was accompanied by the high levels of specific antibody to the respective components of the recombinant vaccine. The above results showed that rFPV-HA-NA could be a potential vaccine to replace current inactivated vaccines for preventing AI.  相似文献   
70.
经直肠超声引导前列腺穿刺活检203例临床分析   总被引:8,自引:1,他引:7  
目的评估经直肠超声引导的前列腺六针穿刺活检在前列腺癌及前列腺其他疾病的诊断和鉴别诊断的价值。方法对指肛检查阳性,血清PSA〉4pg/L及经直肠超声检查前列腺声像图异常怀疑有占位性病变的203人进行经直肠超声引导的前列腺穿刺活检。结果穿刺活检的203例病理结果:良性前列腺增生(BPH)104例占51.24%,前列腺癌(PCa)95例占46.80%,前列腺结核及前列腺平滑肌肉瘤各2例,分别占0.98%。结论经直肠超声引导的前列腺穿刺活检其操作简单,病人痛苦小,并发症少,较安全。在前列腺癌及其他前列腺疾病的诊断与鉴别诊断中有重要的临床价值。  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