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   68750篇
  免费   4664篇
  国内免费   2501篇
耳鼻咽喉   305篇
儿科学   934篇
妇产科学   1000篇
基础医学   11710篇
口腔科学   940篇
临床医学   3728篇
内科学   10689篇
皮肤病学   1043篇
神经病学   10317篇
特种医学   826篇
外国民族医学   19篇
外科学   4095篇
综合类   7370篇
现状与发展   7篇
预防医学   1654篇
眼科学   599篇
药学   13178篇
  5篇
中国医学   1414篇
肿瘤学   6082篇
  2024年   126篇
  2023年   814篇
  2022年   1459篇
  2021年   2028篇
  2020年   1760篇
  2019年   1774篇
  2018年   1859篇
  2017年   1875篇
  2016年   1957篇
  2015年   2285篇
  2014年   3746篇
  2013年   5013篇
  2012年   3708篇
  2011年   4324篇
  2010年   3578篇
  2009年   3665篇
  2008年   3975篇
  2007年   3598篇
  2006年   3120篇
  2005年   2680篇
  2004年   2528篇
  2003年   2333篇
  2002年   1871篇
  2001年   1627篇
  2000年   1479篇
  1999年   1308篇
  1998年   1482篇
  1997年   1373篇
  1996年   1251篇
  1995年   995篇
  1994年   915篇
  1993年   818篇
  1992年   610篇
  1991年   561篇
  1990年   416篇
  1989年   357篇
  1988年   306篇
  1987年   283篇
  1986年   296篇
  1985年   362篇
  1984年   302篇
  1983年   189篇
  1982年   256篇
  1981年   211篇
  1980年   143篇
  1979年   93篇
  1978年   58篇
  1977年   45篇
  1976年   37篇
  1975年   33篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
子宫内膜息肉中雌、孕激素受体的表达   总被引:2,自引:0,他引:2  
目的检测子宫内膜息肉雌激素受体(ER)、孕激素受体(PR)的表达,探索子宫内膜息肉形成的原因及机制。方法子宫内膜息肉48例为观察组,正常子宫内膜36例为对照组,采用免疫组化SP法,行半定量分析,检测ER、PR的表达。结果增殖期的息肉组织中PR表达的评分结果为(2.89±2.16),低于增殖内膜的评分(4.04±1.73),差异有统计学意义(P<0.05);分泌期的内膜息肉中ER表达的评分结果为(3.80±1.64),高于分泌期内膜中的评分(2.64±1.45),差异有统计学意义(P<0.05)。结论增殖期的子宫内膜息肉中PR的表达降低及分泌期的息肉中ER表达增高可能参与了子宫内膜息肉的形成及发展。  相似文献   
52.
王莉 《世界肿瘤杂志》2005,4(3):243-244,F0003
近年来陆续发现了许多新的趋化因子和受体,研究发现趋化因子及其受体参与机体的多种生理和病理过程,并在肿瘤的侵袭转移中通过不同机制发挥着重要作用。本文对其进行简要综述。  相似文献   
53.
Graft thrombosis is the most common cause of first year graft failure in pediatric renal transplantation. The North American Pediatric Renal Transplant Cooperative Study (NAPRTCS) database was analyzed for cases of graft failure due to thrombosis among patients transplanted from 1998 to 2004. The impact of interleukin-2 (IL-2) receptor antagonists as induction therapy was determined. There were a total of 51 graft failures due to thrombosis among the 2750 reported renal transplants (1.85%) (95% CI (1.39%, 2.41%)). This represents the most common cause of graft loss during the first year post-transplant accounting for 35% of first year losses and 18% of all graft losses. The incidence of thrombosis among patients who received IL-2 receptor antibodies was 1.07% (12/1126) compared to 2.40% (39/1624) among patients who did not (OR 0.44, 95% CI 0.23, 0.84, p = 0.014). Use of IL-2 receptor blockade was the only significant prognostic factor in a multivariate model with previously identified risk factors. Analysis of NAPRTCS data found that the use of IL-2 receptor antibodies as induction therapy is associated with a significantly decreased risk of graft failure due to thrombosis. This provocative finding requires further investigation to determine whether thrombotic failure can be decreased by this therapeutic strategy.  相似文献   
54.
Radiotherapy(RT)is an important ap-proach for treatment of esophageal carcinoma(EC),especially for patients who have missedthe chance of surgical section.The efficacy ofRTis not satisfactory for its1-year,3-year and5-year survival rates being merely50%,20%,and10%respectively(1).Researches in recent years showed thatbetter efficacy can be obtained by combiningRTwith Chinese herbal medicines for EC thatincapable to be resected.Kang ai Injection(康艾注射液,KAI)is a Chinese herbal prep-arati…  相似文献   
55.
We studied 44 cases of Hodgkin's disease for the presence of Epstein-Barr virus (EBV) DNA, its localization and the expression of the EBV receptor on the tumour cells. EBV DNA was found in 52% (16/31) of the Hodgkin's lymphomas using the polymerase chain reaction. With a very sensitive non-radioactive DNA in situ hybridization technique in combination with immunohistochemistry for CD 30 or CD 15 antigens, EBV DNA was localized to Reed-Sternberg cells and its mononuclear variants. The relationship between the presence of EBV DNA and the expression of the EBV-receptor CR2 (CD 21) on Reed-Sternberg cells was studied using the same techniques and two different monoclonal anti-CD 21 antibodies. CR2 could be detected on a substantial number of the Reed-Sternberg cells in EBV DNA positive Hodgkin's lymphomas (9/12; 75%), whereas in EBV negative cases positivity with anti-CD 21 was rare (1/13; 8%). The results indicate that CR2 expression on Reed-Sternberg cells and the presence of EBV DNA sequences are frequently associated in Hodgkin's lymphomas.  相似文献   
56.
朱友成    C.Prenant    C.Crouzel    池志强 《药学学报》1994,29(11):823-828
羟甲芬太尼(I)是一个新的高强度高选择性阿片μ受体激动剂。本文用cis-A-N-[1-(2-羟基-2-苯乙基)-3-甲基-4-哌啶基]-苯胺(II)或cis-N-[1-(苯甲酰甲基)-3-甲基-4-哌啶基]-苯胺(III)作为前体合成了[11C]-羟甲芬太尼,以便用正电子发射断层扫描(PET)来观察μ受体。通过水解cis-A-羟甲芬太尼(I)和cis-N-[1-(苯甲酰甲基)-3-甲基-4-哌啶]-N-苯基丙酰胺(cis-IV)的4-N-丙酰基分别获得II和III。溴乙烷的格氏试剂与回旋加速器产生的[11C]-二氧化碳反应后继而直接加入邻苯二甲酸二酰氯和2,6-二叔丁基吡啶生成同位素标记中间体[11C]-丙酰氯。[11C]-丙酰氯与OH-前体(II)反应后再经HPLC分离纯化直接得[11C]-羟甲芬太尼;[11C]-丙酰氯与酮-前体(III)反应后,再用硼氢化钠甲醇溶液处理,然后进行HPLC分离纯化得[11C]-羟甲芬太尼。两种方法均可获得ll.1~14.8GBq/μmol的特异性放射化学纯[11C]-羟甲芬太尼。总共耗时为40~50min(EOB)。  相似文献   
57.
目的探讨酪氨酸激酶抑制剂(Tyrosine kinase inhibitor,TKI)对培养气管上皮细胞生长的影响.方法通过MMT法、3H-胸腺嘧啶(3H-TdR)掺入法及流式细胞计数,观察3种TKIs:Tyrphostin AG1478、Genistein(Sigma)及金转停对原代培养的大鼠气管上皮细胞增殖、周期及凋亡的影响,以及TKIs对表皮生长因子(EGF)的阻断作用.结果MTT法显示3种TKI均对气管上皮细胞的生长具有时间和剂量依赖性抑制作用,同时,TKI阻断EGF对气管上皮细胞生长的刺激作用,3种TKIs的作用无明显差异;1μmol/L的Tyrphostin AG1478、Genistein及金转停分别使气管上皮细胞的TdR掺入率降低18.3%、20.9%及19.7%,与MTT比色法结果一致.同时,Tyrphostin AG1478不仅加速气管上皮细胞的凋亡而且阻止细胞有丝分裂.TKIs可阻断表皮生长因子(EGF)对气管上皮细胞生长的刺激作用.结论TKIs不仅抑制对原代培养的大鼠气管上皮细胞的生长,加速其凋亡,而且可阻断EGF对气管上皮细胞生长的刺激作用,3种抑制剂的作用无明显差异.  相似文献   
58.
The seven serotypes (A–G) of botulinum neurotoxin (BoNT) are proteins produced by Clostridium botulinum and have multifunctional abilities: (i) they target cholinergic nerve endings via binding to ecto‐acceptors (ii) they undergo endocytosis/translocation and (iii) their light chains act intraneuronally to block acetylcholine release. The fundamental process of quantal transmitter release occurs by Ca2+‐regulated exocytosis involving sensitive factor attachment protein‐25 (SNAP‐25), syntaxin and synaptobrevin. Proteolytic cleavage by BoNT‐A of nine amino acids from the C‐terminal of SNAP‐25 disables its function, causing prolonged muscle weakness. This unique combination of activities underlies the effectiveness of BoNT‐A haemagglutinin complex in treating human conditions resulting from hyperactivity at peripheral cholinergic nerve endings. In vivo imaging and immunomicroscopy of murine muscles injected with type A toxin revealed that the extended duration of action results from the longevity of its protease, persistence of the cleaved SNAP‐25 and a protracted time course for the remodelling of treated nerve–muscle synapses. In addition, an application in pain management has been indicated by the ability of BoNT to inhibit neuropeptide release from nociceptors, thereby blocking central and peripheral pain sensitization processes. The widespread cellular distribution of SNAP‐25 and the diversity of the toxin's neuronal acceptors are being exploited for other therapeutic applications.  相似文献   
59.
Mechanical stimulation is known to be an essential factor in the regulation of cartilage metabolism. We tested the hypothesis that expression of lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) can be modulated by cyclic tensile stretch load in chondrocytes. Cyclic loading of repeated stretch stress at 10 cycles per minute with 10 kPa of stress for 6 h induced expression of LOX-1 to 2.6 times control in cultured bovine articular chondrocytes, equivalent to the addition of 10 microg/mL oxidized low density lipoprotein (ox-LDL) (2.4 times control). Application of the cyclic load to the chondrocytes along with 10 microg/mL ox-LDL resulted in synergistically increased LOX-1 expression to 6.3 times control. Individual application of cyclic loading and 10 microg/mL ox-LDL significantly suppressed chondrocytes viability (84.6% +/- 3.4% and 80.9% +/- 3.2% of control at 24 h, respectively; n = 3; p < 0.05) and proteoglycan synthesis [81.0% +/- 7.1% and 85.7% +/- 5.2% of control at 24 h, respectively; p < 0.05 when compared with 94.6% +/- 4.6% for native-LDL (n = 3)]. Cyclic loading and 10 microg/mL ox-LDL synergistically affected cell viability and proteoglycan synthesis, which were significantly suppressed to 45.6% +/- 4.9% and 48.7% +/- 6.7% of control at 24 h, respectively (n = 3; p < 0.01 when compared with individual application of cyclic loading or 10 microg/mL ox-LDL). In this study, we demonstrated synergistic effects of cyclic tensile stretch load and ox-LDL on cell viability and proteoglycan synthesis in chondrocytes, which may be mediated through enhanced expression of LOX-1 and which has important implications in the progression of cartilage degeneration in osteoarthritis.  相似文献   
60.
XGD-1对人外周血T淋巴细胞增殖和IL-2R表达的影响   总被引:1,自引:1,他引:0  
目的 探讨XGD—l的免疫抑制作用及其作用机理。方法 不同浓度的XGD—l作用于植物血凝索(PHA)和刀豆索A(ConA)诱导的正常人外周血T淋巴细胞,共同培养48h和72h,用改良MTT法观察XGD—l对人T淋巴细胞增殖的影响,用流式细胞术检测XGD—l对T淋巴细胞表面IL—2R表达的影响;同时观察联合应用CsA和XGD—l对细胞增殖及IL—2R表达的影响。结果 XGD—l对PHA和ConA诱导的正常人外周血T淋巴细胞增殖有明显的抑制作用,其作用与药物浓度有关,在一定剂量范围内,抑制作用随XGD—l剂量的递增而加强;XGD—l对PHA和ConA激活的T淋巴细胞表面IL-2R的表达有显著抑制作用,阳性率从正常对照活化细胞的47.67%降为25.03%;联合应用CsA,上述抑制作用增强。结论 XGD-l具有免疫抑制作用,能降低IL-2R表达,可能是其免疫抑制作用的重要机理之一。  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