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   31983篇
  免费   3149篇
  国内免费   1631篇
耳鼻咽喉   331篇
儿科学   564篇
妇产科学   359篇
基础医学   2714篇
口腔科学   517篇
临床医学   4177篇
内科学   3351篇
皮肤病学   707篇
神经病学   1146篇
特种医学   1150篇
外国民族医学   9篇
外科学   2165篇
综合类   7007篇
现状与发展   7篇
一般理论   2篇
预防医学   3495篇
眼科学   641篇
药学   3950篇
  64篇
中国医学   2616篇
肿瘤学   1791篇
  2024年   107篇
  2023年   422篇
  2022年   1401篇
  2021年   1868篇
  2020年   1492篇
  2019年   896篇
  2018年   975篇
  2017年   1137篇
  2016年   898篇
  2015年   1585篇
  2014年   2009篇
  2013年   2229篇
  2012年   3160篇
  2011年   3260篇
  2010年   2425篇
  2009年   2040篇
  2008年   2089篇
  2007年   1917篇
  2006年   1561篇
  2005年   1263篇
  2004年   837篇
  2003年   692篇
  2002年   464篇
  2001年   399篇
  2000年   308篇
  1999年   166篇
  1998年   91篇
  1997年   84篇
  1996年   71篇
  1995年   76篇
  1994年   47篇
  1993年   38篇
  1992年   53篇
  1991年   54篇
  1990年   31篇
  1989年   23篇
  1988年   26篇
  1987年   22篇
  1985年   14篇
  1966年   13篇
  1965年   40篇
  1964年   31篇
  1963年   26篇
  1962年   27篇
  1959年   48篇
  1958年   51篇
  1957年   65篇
  1956年   28篇
  1955年   18篇
  1954年   21篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
目的:检测视黄酸依赖Fas/RARα表达载体转染HL-60细胞启动的凋亡效应。方法:成功构建视黄酸依赖Fas/RARα表达载体,用脂质体转染HL-60白血病细胞,经四甲基偶氮唑盐[3-(4,5-dimethylthiaol-2-yl)-2,5-diphenyl tetrazolium bromide,MTT]、流式细胞、DNA梯形带和透射电镜等方法观测视黄酸处理后细胞凋亡效应的发生。结果:以一定剂量的视黄酸处理HL-60后,细胞增殖受抑,呈凋亡性变。结论:视黄酸及其依赖的融合基因表达可协同诱导HL-60细胞发生凋亡效应。  相似文献   
92.
目的探讨粉防己碱预处理对心肌缺血/再灌注过程中大鼠肿瘤坏死因子-α表达及与核因子活化的影响以及相关关系。方法60只SD大鼠随机分为3组:缺血/再灌注损伤组、假手术组、粉防己碱治疗组,缺血/再灌注损伤组结扎大鼠左前降支造成心肌缺血30min后再灌注24h后处死大鼠;假手术组只穿针不结扎,余步骤同缺血/再灌注损伤组;粉防己碱治疗组在缺血前30min腹腔注射粉防己碱,余步骤同缺血/再灌注损伤组。24h后取心肌标本,用酶联免疫吸附法检测心肌组织中肿瘤坏死因子-α表达水平,凝胶电泳迁移率变化分析检测核因子的活性。结果粉防己碱组与缺血再灌注组相比肿瘤坏死因子-α表达水平明显减低(208.40±25.12 VS 306.65±17.78,P<0.01)而与假手术组相比表达明显增强(208.40±25.12 VS 61.45±9.20,P<0.01)。粉防己碱组核因子的活性明显低于缺血再灌注组(29.58±1.56 VS 40.33±4.39,P<0.01)而与假手术组无显著性差异(29.58±1.56 VS 30.09±3.46,P>0.05)。结论粉防己碱预处理可以使心肌缺血/再灌注损伤过程中肿瘤坏死因子-α生成明显减少,核因子的活化受到有效抑制,从而起到减轻心肌缺血/再灌注损伤的作用。  相似文献   
93.
中国北方人群系统性红斑狼疮患者KIR基因多态性的研究   总被引:2,自引:1,他引:2  
目的:检测和分析系统性红斑狼疮患者的杀伤细胞免疫球蛋白样受体(KIR)基因的多态性, 探讨系统性红斑狼疮(SLE)从基因到临床表达的发病机制.方法:应用PCR-SSP技术检测北方62例确诊SLE患者和61例同一区域同一民族正常对照者的KIR基因位点多态性.结果:SLE 患者KIR基因表型分布较常见的为KIR3DP1、 2DL1、 2DP1、 3DL1、 2DL3及1D, 其次为2DS4、 2DL5、 3DS1、 2DS2、 2DS5和2DL2, 较低者为2DS1、 2DS3及3DP1V, SLE病例组KIR3DS1, 2DL2、 2DL5和2DL3基因型频率比对照组显著降低(P<0.01).结论:中国北方人群的SLE的发生可能与多个KIR基因等位基因有相关性.  相似文献   
94.
低强度脉冲电磁场对大鼠骨质疏松的影响   总被引:1,自引:0,他引:1  
目的:观察低强度脉冲电磁场(pulsed electromagnetic fields,PEMFs)对去卵巢诱导骨质疏松症的大鼠生化指标和骨应力的影响。方法:雌性SD大鼠30只,随机等分为3组(n=10),分别为假手术组(Sham)、骨质疏松模型组(Model)、脉冲电磁场照射组(PEMFs)。经适应4wk后,在25mg·Kg^-1戊巴比妥钠腹腔麻醉下,Model组和PEMFs组摘除双侧卵巢.Sham组找到但不切除卵巢。各实验组均在相同环境下饲养,模型制备4wk后开始治疗,由GZY型低强度低频率脉冲电磁场发生仪产生低频脉冲磁场,根据实验要求,我们使用亥姆霍兹线圈形成均匀磁场,PEMFs组经照射刺激治疗,频率14.3Hz,场强2Gs.日照8h。Model组和Sham组正常饲养。治疗8wk后,对各组大鼠血清、尿液中ALP和Ca以及骨应力进行检测。结果:(1)ALP、Ca检测结果:与Model组相比,PEMFs组ALP值、Ca值差异均有统计学意义(P〈0.05)。其中,血清中ALP值,Model组为(275.16±228,57),PEMFs组为(179.30±87.68);Ca值,Model组为(2,66±0,13),PEMFs组为(2.52±0.05)。(2)骨应力检测结果:Model组为(923.60±34.15Pa),PEMFs组为(1152.85±118,20Pa),组间差异有统计学意义(P〈0.05)。结论:研究发现,PEMFs对于促进骨重建、提高Ca吸收和骨应力恢复具有积极作用。  相似文献   
95.
Scrotal leiomyomas with atypical bizarre nuclei are rare, which might be misdiagnosed as malignant tumor. We describe a case of scrotal bizarre leiomyoma in a 65-yr-old man. The tumor was a 1 cm-sized, well circumscribed, oval mass arising from the tunica dartos muscle. Histologically, it was formed by whorling bundles of fusiform cells with occasional atypical, pleomorphic nuclei and pseudo-inclusions. Mitosis was not found. Although morphologically atypical, scrotal bizarre leiomyomas take on a biologic behavior not different from that of conventional leiomyoma, they should be distinguished from leiomyosarcoma to avoid unnecessary treatment.  相似文献   
96.
Although estrogen is known to play a crucial role in the pathogenesis of breast cancer, the molecular mechanisms underlying the action of estrogen remain elusive. In the present study, we focused on keratinocyte growth factor (KGF) and its receptor (KGFR) in the pathogenesis of breast cancer, as a growth factor mediating estrogen action, since significant roles of KGF were demonstrated in various steroid hormone-dependent tissues. First, using paraffin-embedded specimens from 42 breast cancer patients, we examined expression patterns of KGF and KGFR by both immunohistochemistry using newly generated antibodies and nonradioactive in situ hybridization with T-T dimerized synthetic oligonucleotide probes. We next compared the results with the expression of estrogen receptor (ER) alpha and beta, proliferative activity and apoptotic frequency (TUNEL staining). Also, the similar approaches were taken to analyze the expression and role of KGF in ER-positive (MCF7, ZR-75-1) and ER-negative (SK-BR-3, MDA-MB-231) human breast cancer cell lines in vitro. In the surgical specimens, KGF was expressed in cancer cells as well as stromal cells in 19/42 cases (45%), while KGFR was found in cancer cells in 24/42 cases (57%). The distribution of protein and mRNA in the analysis of both KGF and KGFR expression generally coincided. Moreover, KGF expression was closely associated with the expression of ER alpha, and the coexpression of KGF and KGFR significantly correlated with lower TUNEL index, but not with proliferative activity. In accordance with the in vivo findings, KGF expression was detected only in ER alpha-positive MCF7 and ZR-75-1 cells in vitro. And more importantly, we found the inhibitory effect of KGF upon the induction of apoptosis by anticancer drugs in MCF7 cells. Collectively, our results indicate that ER alpha may be involved in KGF expression, and that KGF may play antiapoptotic roles, rather than mitogenic, in human breast cancer.  相似文献   
97.
The purpose of this study was to determine whether 20 patients who received an early postmastectomy rehabilitation treatment program showed more improvement in range of shoulder motion and functional activities than 13 patients who received instruction for exercise only. Data were obtained at preoperatively, three days after operation, at discharge and at postdischarge one month for each patient on parameters such as range of motion of the ipsilateral shoulder joint, upper extremity circumferential measurements, as well as 10 elements of shoulder function. Postoperatively, both groups showed an increased range of motion of the shoulder joint and improved functional activities, but the group that received postoperative rehabilitation management had a better range of shoulder motion and less difficulty in five items for functional assessment. This study also showed that an early rehabilitation program did not increase postoperative complications. We concluded that an early rehabilitation program or intensive instruction program only by a well-trained physical therapist or physiatrist was beneficial to postmastectomy patients in regaining the function and range of shoulder motion, and significantly better in a rehabilitation group.  相似文献   
98.
Systemic lupus erythematosus (SLE), a complex multigenic disease, is a typical antibody-mediated autoimmune disease characterized by production of autoantibodies against a variety of autoantigens and immune complex-type tissue inflammation, most prominently in the kidney. Evidence suggests that genetic factors predisposing to aberrant proliferation/maturation of self-reactive B cells initiate and propagate the disease. In SLE-prone New Zealand Black (NZB) mice and their F1 cross with New Zealand White (NZW) mice, B cell abnormalities can be ascribed mainly to self-reactive CD5+ B1 cells. Our genome-wide scans to search for susceptibility genes for aberrant activation of B1 cells in these mice showed evidence that the gene, Ltk, encoding leukocyte tyrosine kinase (LTK), is a possible candidate. LTK is a receptor-type protein tyrosine kinase, belonging to the insulin receptor superfamily, and is mainly expressed in B lymphocyte precursors and neuronal tissues. Sequence and functional analyses of the gene revealed that NZB has a gain-of-function polymorphism in the LTK kinase domain near YXXM, a binding motif of the p85 subunit of phosphatidylinositol 3-kinase (PI3K). SLE patients also had this type of Ltk polymorphism with a significantly higher frequency compared with the healthy controls. Our findings suggest that these polymorphic LTKs cause up-regulation of the PI3K pathway and possibly form one genetic component of susceptibility to abnormal proliferation of self-reactive B cells in SLE.  相似文献   
99.
Summary.  We have evaluated PCR–RFLP as a practical method for rapid typing of enteroviruses causing aseptic meningitis in Korea. Through blind examination of 80 clinical isolates from patients with aseptic meningitis, we have compared the results of conventional serotyping with PCR–RFLP based genotyping, which was developed for this study. Among the 80 case isolates, which had been previously typed by routine neutralization test, only 42 cases (52.5%) were matched with typing by PCR–RFLP. The result clearly demonstrated that the enterovirus serotype does not coincide with the genotype. Therefore, the classification of enteroviruses by genotyping with PCR–RFLP, although rapid and simple, may be complicated by regional or seasonal differences. However, the PCR–RFLP method developed in this study is applicable to the epidemiological study of enteroviruses when regional or seasonal differences exist, and is useful in identifying the source of an infection. Received August 6, 2001; accepted April 15, 2002 Published online July 10, 2002  相似文献   
100.
目的 探讨酒精对小鼠睾丸的组织结构、内皮型一氧化氮合酶 (eNOS)、增殖细胞核抗原 (PCNA)及细胞凋亡的影响。 方法 用 5 %、10 %及 15 % 3种不同浓度的酒精作用于 2 2d龄小鼠 ,取睾丸做石蜡切片、HE染色 ;用免疫组织化学方法检测睾丸eNOS、细胞增殖的变化 ;TUNEL法检测细胞凋亡的变化 ,并进行统计学分析。 结果 随着酒精浓度的增大 ,睾丸组织结构发生明显改变 ,生精小管的直径逐渐减小 ,eNOS阳性细胞面积密度逐渐增大 ,单位面积内PCNA阳性细胞和凋亡细胞数目增加 ,高浓度酒精组与其他组差异极显著 (P <0 0 1)。 结论 酒精可使生精小管的直径变小 ,eNOS及PCNA表达增强 ,凋亡细胞增加并随酒精浓度的增大而变化加重。这可能是过量饮酒导致生精细胞减少 ,生殖能力降低的重要因素。  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