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   69955篇
  免费   7107篇
  国内免费   5570篇
耳鼻咽喉   649篇
儿科学   708篇
妇产科学   722篇
基础医学   7443篇
口腔科学   1229篇
临床医学   8644篇
内科学   9496篇
皮肤病学   634篇
神经病学   3293篇
特种医学   2428篇
外国民族医学   36篇
外科学   7012篇
综合类   14626篇
现状与发展   15篇
一般理论   6篇
预防医学   5615篇
眼科学   1701篇
药学   7659篇
  46篇
中国医学   4961篇
肿瘤学   5709篇
  2024年   256篇
  2023年   1080篇
  2022年   2790篇
  2021年   3433篇
  2020年   2782篇
  2019年   2387篇
  2018年   2397篇
  2017年   2316篇
  2016年   2225篇
  2015年   3319篇
  2014年   3881篇
  2013年   3611篇
  2012年   4781篇
  2011年   5353篇
  2010年   3653篇
  2009年   2796篇
  2008年   3282篇
  2007年   3754篇
  2006年   3553篇
  2005年   3207篇
  2004年   3193篇
  2003年   3707篇
  2002年   3327篇
  2001年   2706篇
  2000年   1868篇
  1999年   1430篇
  1998年   939篇
  1997年   901篇
  1996年   612篇
  1995年   581篇
  1994年   475篇
  1993年   301篇
  1992年   328篇
  1991年   275篇
  1990年   236篇
  1989年   209篇
  1988年   184篇
  1987年   150篇
  1986年   116篇
  1985年   94篇
  1984年   44篇
  1983年   30篇
  1982年   17篇
  1981年   24篇
  1980年   16篇
  1979年   12篇
  1963年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
吡那地尔对高血压心脏结构和功能重构的影响   总被引:5,自引:0,他引:5  
在等降压剂量下吡那地尔和赖诺普利可使4月龄自发性高血压大鼠的血压下降6.0 ̄8.0kPa,并接近同种属正常血压大刀瓣血压水平。  相似文献   
62.
This study compares the incidence of local tumor recurrence following primary excision with the CO2 laser, Nd:YAG laser (contact), Argon Beam Coagulator, or electrocautery. One hundred eight Fisher 344 rats with R3230AC mammary tumors (1.6 +/- 0.04 [SD] cm diameter) were used. All animals were randomized into groups of similar tumor size. In groups C and CS, excision was performed with a Sharplan 1060 CO2 laser (TEMoo, 25 W, continuous wave [CW], 0.2-mm spot size). Wounds in group CS were "sterilized" (0.5-mm spot size, 25 W, CW) by gently heating the wound without causing blanching or charring. In group N, a 0.4-mm contact Laser Blade and a Cooper 8000 Nd:YAG laser at 20 W CW was used. In groups SA1 and SA2, tumors were excised with the scalpel, and hemostasis and wound "sterilization" were accomplished with the Bard System 6000 Argon Beam Coagulator (ABC) at 40 W and 4 liters/min argon gas flow in SA1 and 12 liters/min in SA2. In group E, excision was accomplished at 40 W blend mode, 10 W spray mode. In group EA, excision was accomplished at 60 W cutting current, and hemostasis was achieved with the ABC. The animals were examined for evidence of recurrence for 34 days postoperatively. Mortalities were excluded from analysis. The incidence of recurrence was 11/14 (79%) in C, 6/16 (38%) in CS, 10/14 (71%) in SA1, 6/13 (46%) in SA2, 6/15 (40%) in N, 7/10 (70%) in EA, and 3/15 (20%) in E. Group E is statistically different (P less than .01) from groups EA, C, and SA1. Group C was different (P less than .01) from groups E, CS, and N. These results demonstrate an inverse relationship between tumor recurrence and local thermal effects at the surgical site. The ABC did not increase tumor recurrence. Contact YAG surgery was similar to CO2 laser excision and "sterilization." An attempt to study the influence of gas flow and pressure on local tumor recurrence and metastases should be made.  相似文献   
63.
摘要:目的 探究赖氨酸特异性甲基转移酶2C(lysine specific methyltransferase 2C,KMT2C)在胃癌发生发展中的 作用及机制。方法 通过 TCGA 数据库分析 KMT2C在胃癌与癌旁的表达差异。采用 Western blot检测 KMT2C在胃 癌与癌旁临床样本中的表达差异。通过 Kaplan-Meier Plotter数据库分析 KMT2C 对胃癌患者预后的影响。采用细胞 实验(克隆形成、EdU 及 CCK-8检测)及皮下瘤负荷模型检测 KMT2C 在体内外对胃癌细胞增殖能力的影响。结果 KMT2C在胃癌中高表达。胃癌患者中 KMT2C高表达组相对于 KMT2C低表达组预后较差。敲减 KMT2C在体内外 均有抑制胃癌 细 胞 增 殖 的 作 用。基 因 集 富 集 分 析 (GSEA)发 现 KMT2C 影 响 c-Myc信 号 通 路。敲 减 KMT2C 后, H3K4me1蛋白表达水平降低,同时,CDK4的 mRNA 与蛋白表达水平降低。KMT2C与c-Myc核内结合促进了c-Myc 与 CDK4的启动子区域的结合。结论 KMT2C通过影响c-Myc/CDK4信号通路促进胃癌细胞增殖。  相似文献   
64.
This study made a histological comparison (light microscope and transmission electron microscope) between vascularized bone graft (VBG) and non-vascularized bone graft (NVBG) in mandible of dog.The study showed:the healing process of VBG was the same as that of bone fracture.The "creeping substitution" process of NVBG was imbued with the inflammation induced by dead bone.There was no significat difference on the bone union between VBG and NVBG perhaps for the recipient region was better vascularized.  相似文献   
65.
呼出气氢测定试验对飞行人员乳糖酶缺乏症的研究   总被引:1,自引:1,他引:0  
倪鹤鹦  肖赞英 《医学争鸣》1989,10(5):328-331
对66名汉族飞行人员进行乳糖呼出气氢测定试验,乳糖吸收不良的发生率为83.3%,其中乳糖不耐受者占34.6%;与一般汉族人群无明显差别。对10名确定为中度以上乳糖吸收不良的飞行人员进行250ml鲜牛奶的试验结果,有50%呼出气氢含量在正常范围,并无一例出现胃肠道症状。提示较长期食用牛奶未能使乳糖酶缺乏状态发生改变,但每日食用适量牛奶属合理营养。  相似文献   
66.
The primary lesion in rheumatoid arthritis (RA) is a destructive synovitis characterized by proliferation of endothelial cells, fibroblasts, and vascular smooth muscle cells, and with perivascular lymphocyte aggregates. A nonhematopoietic growth factor, acidic fibroblast growth factor (aFGF), may induce many of the biological features found in rheumatoid synovium, including T cell activation. To determine if aFGF-responsive T cells are increased in RA, we developed an assay to measure the frequency of peripheral blood T cells that are costimulated by aFGF. The data indicate that the frequency of aFGF-responsive T cells is increased in RA and may change with disease activity and treatment.  相似文献   
67.
Although Cryptosporidium has been found worldwide in molluscan shellfish from waters contaminated with human and animal feces, little or no related environmental data have been obtained. In the present study, oysters ( Crassostrea virginica) were collected eight times over 3 years from seven sites in the Chesapeake Bay or its tributaries, with accompanying data on water temperature, salinity, rainfall, and streamflow. Oyster gill washings were examined by immunofluorescence microscopy for Cryptosporidium oocysts. Of 1,590 oysters collected, 19.6% had detectable oocysts. Of 53 collections, oocysts were detected 81% of the time. The time when the greatest percentage of oysters at most sites had detectable oocysts coincided with the time of greatest weekly and monthly rainfall, greatest streamflow into the Bay, and lowest water temperatures. In 28% of 53 collections, C. parvum genotypes 1 and 2 and C. baileyi were identified by PCR and gene sequencing. Oocyst infectivity was confirmed from 37.5% of 40 collections by initiating C. parvum genotype 2 infections in mice.  相似文献   
68.
69.
目的 探讨肝素酶(heparanase)和碱性成纤维细胞生长因子(bFGF)在人非小细胞肺癌(NSCLC)组织中表达的临床意义及其与肺癌转移和预后的关系。方法 采用免疫组织化学、原位杂交和Western blot方法,检测115例人NSCLC石蜡切片和45例新鲜肺癌及对应癌旁正常组织中肝素酶和bFGF的表达情况。采用χ^2检验、t检验、生存曲线和Cox比例风险回归等方法分析肝素酶和bFGF分别表达及共表达的意义。结果 免疫组织化学染色证实肝素酶(91/115)和bFGF(89/115)主要表达在癌细胞质和(或)细胞膜中,在正常肺泡上皮和支气管上皮中则呈阴性表达。Western blot也证实肝素酶在肺癌中的表达明显增高(P=0.041)。统计分析结果显示:肝素酶和bFGF的表达具有明显的一致性(P:0.0001),二者单独表达和共表达均与肺癌的分期、血管侵袭、淋巴结转移、微血管密度和预后有关,其中,二者共表达时与分期和微血管密度的相关性更显著;另外,bFGF还与肺癌的分化程度有关。多因素分析结果显示,肺癌的分化程度、血管浸润、淋巴结转移和bFGF的表达可以作为判断肺癌预后的危险因素,但肝素酶不是影响预后的独立因素。结论 肝素酶和bFGF均与肺癌的转移、血管生成和预后密切相关。  相似文献   
70.
The aim of this research was to study whether and to what extent Chinese cagA-positive Helicobacter pylori isolates differ from those in The Netherlands. Analysis of random amplified polymorphic DNA (RAPD)-PCR-assessed DNA fingerprints of chromosomal DNA of 24 cagA-positive H. pylori isolates from Dutch (n = 12) and Chinese (n = 10) patients yielded the absence of clustering. Based on comparison of the sequence of a 243-nucleotide part of cagA, the Dutch (group I) and Chinese (group II) H. pylori isolates formed two separate branches with high confidence limits in the phylogenetic tree. These two clusters were not observed when the sequence of a 240-bp part of glmM was used in the comparison. The number of nonsynonymous substitutions was much higher in cagA than in glmM, indicating positive selection. The average levels of divergence of cagA at the nucleotide and protein levels between group I and II isolates were found to be high, 13.3 and 17.9%, respectively. Possibly, the pathogenicity island (PAI) that has been integrated into the chromosome of the ancestor of H. pylori now circulating in China contained a different cagA than the PAI that has been integrated into the chromosome of the ancestor of H. pylori now circulating in The Netherlands. We conclude that in China and The Netherlands, two distinct cagA-positive H. pylori populations are circulating.  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