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   15326篇
  免费   1306篇
  国内免费   1246篇
耳鼻咽喉   106篇
儿科学   141篇
妇产科学   227篇
基础医学   1851篇
口腔科学   326篇
临床医学   2202篇
内科学   2479篇
皮肤病学   124篇
神经病学   845篇
特种医学   617篇
外国民族医学   11篇
外科学   1664篇
综合类   2370篇
现状与发展   3篇
一般理论   3篇
预防医学   865篇
眼科学   362篇
药学   1573篇
  12篇
中国医学   807篇
肿瘤学   1290篇
  2024年   50篇
  2023年   260篇
  2022年   657篇
  2021年   866篇
  2020年   575篇
  2019年   519篇
  2018年   559篇
  2017年   440篇
  2016年   450篇
  2015年   675篇
  2014年   850篇
  2013年   702篇
  2012年   1090篇
  2011年   1208篇
  2010年   699篇
  2009年   646篇
  2008年   793篇
  2007年   799篇
  2006年   741篇
  2005年   772篇
  2004年   489篇
  2003年   491篇
  2002年   439篇
  2001年   339篇
  2000年   390篇
  1999年   436篇
  1998年   267篇
  1997年   248篇
  1996年   210篇
  1995年   207篇
  1994年   150篇
  1993年   110篇
  1992年   137篇
  1991年   86篇
  1990年   86篇
  1989年   80篇
  1988年   62篇
  1987年   73篇
  1986年   51篇
  1985年   52篇
  1984年   26篇
  1983年   17篇
  1982年   5篇
  1981年   10篇
  1980年   6篇
  1979年   9篇
  1968年   4篇
  1964年   4篇
  1954年   3篇
  1931年   6篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
本文报告了6~9个月胎儿长骨的化学成分的测定结果及其组织特点并与成人作了比较。自1985~1987年共进行了胎儿骨移植40例,随访38例,经4~20个月(平均10.3个月)的临床观察,证实胎儿骨移植后“爬行替代”快,骨诱导能力强,排斥反应不明显,笔者认为这些特点与胎骨的形态结构及化学成分有关。胎儿骨的采取和贮存简便,应用方便,易于推广和普及。  相似文献   
42.
Response properties of reticulospinal neurons in the lateral reticular nucleus (LRN) area to natural cutaneous stimulation were investigated systematically in 45 urethane-anesthetized rats by using extracellular recording techniques. A total of 64 neurons were tested with peripheral stimuli, of which 19 were responsive only to noxious stimuli; 7 responsive to both noxious and non-noxious stimuli; 4 responsive only to non-noxious stimuli; and 34 not responsive to any cutaneous stimuli. Both the noxious and non-noxious receptive fields were large and bilateral. Among the neurons responding to noxious stimuli, the majority (72%) was excited. This study provides evidence that some reticulospinal neurons in the rat LRN area are involved in the mechanisms of nociception.  相似文献   
43.
子宫阔韧带内静脉的解剖学研究及其临床意义   总被引:2,自引:0,他引:2  
子宫底和体上部的静脉汇集于子宫角处浅出,应称子宫上静脉。该静脉续为卵巢静脉。子宫上静脉1条者占30%,2条者占56.7%,3条者占13.3%。子宫上静脉与输卵管峡部中点相对处的口径是3.7±0.2mm,卵巢丛与子宫上静脉汇合后的口径为5.0±0.4mm。输卵管峡部中点与子宫上静脉的间距为6.3±0.6mm。在输卵管系膜中见有输卵管静脉汇入子宫上静脉。本文研究结果认为盆腔静脉淤血症的发生,与结扎手术中损伤子宫上静脉和输卵管静脉有关。  相似文献   
44.
Summary: In this work, blends of monomer casting polyamide 6 (MCPA6) and acrylonitrile‐butadiene‐styrene (ABS) were successfully prepared by in situ polymerization via the application of ε‐caprolactam as a reactive solvent. The morphology and thermal properties of MCPA6/ABS were investigated by means of wide angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM), respectively. The domain sizes of the ABS phase in MCPA6/ABS blends were much finer than those in corresponding polyamide 6 (PA6)/ABS blends prepared by simple melt blending. With an increased amount of ABS in MCPA6, the melt enthalpy (ΔHf), the rate of crystallization (Tc) and the degree of crystallinity (Xc(DSC)) of MCPA6 in MCPA6/ABS blends were all decreased. The degree of supercooling (ΔTd) showed a contrary trend. However, the melting temperatures of these blends were almost unchanged. All the results could be attributed to in situ polymerization and the hydrolysis reaction of ABS that occurred during the polymerization process. Furthermore, WAXD results showed that only α‐form crystals existed in the MCPA6/ABS blends, despite the ABS content and heat treatment.

SEM micrograph of the fractured surface of an MCPA6/ABS blend with an ABS content of 20 wt.‐% (×10 000).  相似文献   

45.
Immunoregulatory effects of morphine on human lymphocytes.   总被引:7,自引:0,他引:7       下载免费PDF全文
It is now well established that parenteral drug abuse is a significant risk factor for contracting human immunodeficiency virus type 1 (HIV-1) infection and subsequently developing AIDS. Earlier studies have shown that morphine can modulate various immune responses and therefore support the premise that morphine is a cofactor in susceptibility to and progression of HIV infection. Dysregulation of interferon (IFN) production, nonspecific apoptosis of T cells, and the immune response to soluble HIV gene products have been associated with potential mechanisms of pathogenesis in HIV disease. The present study was undertaken to examine the immunomodulatory role of morphine on HIV protein-induced lymphocyte proliferative responses, Sendai and Newcastle disease virus-induced alpha IFN (IFN-alpha) and IFN-beta production by lymphocytes and fibroblast cells, respectively, and induction of apoptosis of normal lymphocytes in vitro. Our results demonstrate that HIV protein-induced human lymphocyte proliferative responses were significantly inhibited by morphine in a dose-dependent manner. Furthermore, morphine significantly inhibited both IFN-alpha and IFN-beta production by normal lymphocytes and fibroblasts but induced apoptosis of normal lymphocytes. Inhibition of IFN-alpha production by morphine could be reversed by the opiate receptor antagonist naloxone. This suggests that the immunomodulatory effects of morphine are mediated through the opioid receptor. These studies support a role of morphine as a cofactor in the pathogenesis of HIV infection and describe some of the possible pathologic mechanisms which underlie the immunoregulatory effects of morphine.  相似文献   
46.
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   
47.
Saccharomyces cerevisiae ATS1 (-tubulin suppressor 1) was originally identified as a high-copy suppressor of class two -tubulin mutations and was proposed to have a regulatory role in coordinating the microtubule state with the cell cycle. Here, we show that Ats1p interacts with Nap1p, a cytoplasmic protein that regulates the activity of the Cdc28p/Clb2p complex. Loss of Nap1p results in a delayed switch from polar to isotropic bud growth. The delayed switch results in elongated buds. Nap1p and Ats1p interact in two-hybrid and co-immunoprecipitation assays. Both nap1 and ats1 cells have a Clb2p-dependent elongated bud morphology. Deletion of ATS1 partially suppresses the elongated bud morphology and benomyl resistance of nap1 mutants. Our results suggest Ats1p might regulate coordination of the microtubule state with the cell cycle through an interaction with Nap1p.Communicated by S. Hohmann  相似文献   
48.
National Taiwan University College of Medicine (NTUCM) introduced small groups of teaching and basic-clinical integrated courses for medical students in 1992. By using computer network and multimedia techniques, this study tried to overcome barriers to learning in small group teaching. The Department of Medical Informatics of NTUCM established campus networking and computer classrooms and provided Internet and intranet network services including mail, netnews, bulletin board systems (BBS), world wide web (WWW), gopher, ftp and local file servers. To implement an interactive learning environment, the authors first tried mail lists, newsgroups and BBS. Next an integrated learning system prototype on the WWW was developed to provide functions including online syllabus, discussion boards simulated to BBS, online talk, interactive case studies, virtual classroom with video on demand (VOD) and Internet medical resources. The results showed that after the medical students completed the required course of medical informatics and had good network access using a network to communicate with each other became a daily practice. In the future, the system will extend to the tutoring of clinical practice and continuing medical education. The authors expect a national medical education network and more international cooperation and exchange.  相似文献   
49.
The lifespan of antigen-bearing dendritic cells (DCs) is determined by signals from pathogens and T cells. These signals regulate DC survival by modulating expression of Bcl-2 family proteins. Toll-like receptors and T cell costimulatory molecules both trigger a DC survival pathway that is dependent on Bcl-x(L). However, Toll-like receptors uniquely increase expression of Bim and trigger cell death by a pathway that is blocked by Bcl-2. This pathway serves as a molecular 'timer' that sets the lifespan of DCs and regulates the magnitude of T cell responses in vivo. Thus, signals derived from the innate and acquired immune systems control DC lifespan and immunogenicity by distinct molecular mechanisms.  相似文献   
50.
运用敏感的B_9细胞增殖试验检测了81例多发性骨髓瘤(MM)患者血清IL-6活性,同时分析了标本的几种急性相蛋白含量,结果表明,68%MM患者血清中IL-6活性大于5μ/ml(正常对照为5μ/ml以下),几种急性相蛋白中C-反应性蛋白(CRP)在MM时升高(P<0.01),平均达正常对照组的17倍以上,MM患者补体C_4与正常对照组无差异(p>0.05),C_3、白蛋白及转铁蛋白在MM时分别比正常下降24.42%、38.83%和32.80%,且与疾病分期有关,在血清IL-6大于5μ/ml的55例中,IL-6活性与CRP、C_3、白蛋白的相关系数分别为0.46,-0.34和-0.29,IL-6与转铁蛋白浓度相关不明显。本文结果提示:CRP、C_3及白蛋白等含量的变化可作为反映MM病情的简易而敏感的指标。  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