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   21899篇
  免费   1260篇
  国内免费   920篇
耳鼻咽喉   110篇
儿科学   446篇
妇产科学   251篇
基础医学   2830篇
口腔科学   539篇
临床医学   1900篇
内科学   3826篇
皮肤病学   537篇
神经病学   1012篇
特种医学   805篇
外国民族医学   2篇
外科学   3014篇
综合类   3447篇
现状与发展   4篇
预防医学   938篇
眼科学   344篇
药学   2296篇
  5篇
中国医学   973篇
肿瘤学   800篇
  2024年   21篇
  2023年   229篇
  2022年   482篇
  2021年   592篇
  2020年   648篇
  2019年   528篇
  2018年   490篇
  2017年   572篇
  2016年   577篇
  2015年   644篇
  2014年   1318篇
  2013年   1545篇
  2012年   1352篇
  2011年   1428篇
  2010年   1226篇
  2009年   1244篇
  2008年   1196篇
  2007年   1169篇
  2006年   1003篇
  2005年   978篇
  2004年   855篇
  2003年   783篇
  2002年   618篇
  2001年   607篇
  2000年   526篇
  1999年   483篇
  1998年   413篇
  1997年   430篇
  1996年   363篇
  1995年   300篇
  1994年   275篇
  1993年   184篇
  1992年   146篇
  1991年   149篇
  1990年   118篇
  1989年   80篇
  1988年   79篇
  1987年   47篇
  1986年   48篇
  1985年   51篇
  1984年   47篇
  1983年   20篇
  1982年   38篇
  1981年   28篇
  1980年   25篇
  1979年   24篇
  1978年   20篇
  1977年   14篇
  1976年   14篇
  1973年   12篇
排序方式: 共有10000条查询结果,搜索用时 796 毫秒
31.
丹参与雷公藤多甙联合治疗急性坏死性胰腺炎的实验研究   总被引:4,自引:0,他引:4  
目的 探讨丹参与雷公藤多甙联合应用对急性坏死性胰腺炎 (acutenecrotizingpancreatitis,ANP)的治疗作用。 方法 采用单次过量 2 0 %L 精氨酸 (10 0 0mg/ 10 0g大鼠体重 )皮下注射建立ANP动物模型。测定血清淀粉酶、TNF α、IL 1β水平 ,并观察胰腺组织的病理变化。根据血清淀粉酶、TNF α、IL 1β水平及胰腺组织的变化来评价胰腺炎的严重程度。 结果 大鼠皮下注射过量L 精氨酸后 ,血清淀粉酶、TNF α、IL 1β水平升高 ,胰腺变性坏死。丹参与雷公藤多甙联合治疗ANP ,可显著降低血清淀粉酶、抑制炎症细胞因子的过度生成 ,组织受损程度明显减轻。结论 丹参与雷公藤多甙联合应用对ANP动物模型具有很好治疗效果 ,可能具有临床应用价值  相似文献   
32.
目的:探讨超声造影诊断肝孤立性坏死结节的价值。材料和方法:回顾分析了12例肝孤立性坏死结节的超声造影表现。结果:12例病灶造影动脉期、门脉期、实质期均无增强,呈边界清晰的造影剂充盈缺损区。结论:超声造影对诊断肝孤立性坏死结节具有较高的价值。目的:探讨超声造影诊断肝孤立性坏死结节的价值。材料和方法:回顾分析了12例肝孤立性坏死结节的超声造影表现。结果:12例病灶造影动脉期、门脉期、实质期均无增强,呈边界清晰的造影剂充盈缺损区。结论:超声造影对诊断肝孤立性坏死结节具有较高的价值。  相似文献   
33.
High cord blood immunoglobulin E (cbIgE) is known to be associated with increased risks of atopic diseases in childhood. The relationship between genetic polymorphisms and high cbIgE has not been well documented. A cross-sectional study was conducted to assess the association between cbIgE and genetic polymorphisms of interleukin (IL)-4 -590C/T, the beta-subunit of the high-affinity receptor for IgE (FcepsilonRI-beta) E237G, lymphotoxin (LT)-alphaNcoI alleles, and tumor necrosis factor (TNF)-alpha -308G/A. A total of 320 mother-neonate pairs were recruited from four maternity hospitals from different locations of Taiwan. Cord blood was obtained and assayed for cbIgE. Polymerase chain reaction followed by restriction fragment length polymorphism was used to assess the genotypes. Three hundred pairs of mothers and neonates were included in the final analysis. Infants with IL-4 -590 C allele were found to have higher risk of elevated cbIgE (> or =0.35 IU/ml, 24.3%) (p = 0.004). After adjusting for gender, birth order, maternal age, and history of allergic disease in maternal and paternal families, odds ratios for CC and CT genotypes were 4.41 and 3.16 (95% confidence interval 0.78-22.67, and 1.66-6.13), respectively, using TT genotype as reference. The genotypes of FcepsilonRI-beta, LT-alpha, and TNF-alpha were not associated with cbIgE before or after the adjustment. Our finding suggested a significant association of cbIgE with genetic polymorphism of IL-4 -590C/T, but not with the genotypes of FcepsilonRI-beta, LT-alpha, and TNF-alpha.  相似文献   
34.
子宫内膜异位症患者血清TNF-α和TNF-β的测定   总被引:7,自引:1,他引:6  
目的:了解子宫内膜异位症(简称内异症)患者血清中肿瘤坏死因子-α(TNF-α)和肿瘤坏死因子-β(TNF-β)的水平以及在腹腔镜保守性手术治疗前后的变化。方法:采用酶联免疫吸附法检测82例内异症患者(内异症组)和68例非内异症妇女(对照组)血清中TNF-α和TNF-β的含量及49例手术前后两者水平的变化。结果:内异症组血清TNF-α和TNF-β含量均显著高于对照组(P<0.01),且二者表达量随病情加重有上升趋势(P<0.05)。手术后Ⅲ~Ⅳ期患者血清中的TNF-α和Ⅰ~Ⅳ期患者血清TNF-β的含量随着内异灶的清除逐渐下降。结论:检测患者血清中TNF-α和TNF-β的含量,对术后随访、监测及手术效果的评价具有重要意义。  相似文献   
35.
目的:探讨细胞活素肿瘤坏死因子-α(TNF-α)、SNAP(S-Nitroso-Nacetyl-penicillamine)对胰腺癌细胞产生血管内皮生长因子A、C(VEGF-A、C)的调节.方法:用Northern杂交和Western杂交法分析6种人胰腺癌细胞株中VEGF-A、C基因和蛋白的表达;以TNF-α或SNAP刺激其中两个细胞株后用逆转录-聚合酶链式反应技术(RT-PCR)分析其VEGF-A、C基因的表达.结果:Northern杂交法显示这6种胰腺癌细胞株均有4.1kb VEGF-A基因和2.4kb VEGF-C基因的表达;Western杂交法显示它们均有分子量为43kD的VEGF-A蛋白质和分子量为55kD的VEGF-C蛋白质的表达.RT-PCR分析法显示:TNF-α使细胞株COLO-357产生VEGF-A、VEGF-C mRNA分别减少约1~2.5倍、1~2倍,使细胞株CAPAN-1产生VEGF-A、VEGF-C mRNA分别减少约1倍、1.6~2.5倍;而SNAP刺激细胞株COLO-357产生VEGF-A mRNA增加约5倍,刺激细胞株CAPAN-1产生VEGF-A mRNA增加约4倍,但对这两种细胞株产生VEGF-C mRNA均无明显刺激作用.结论:细胞活素TNF-α和低氧通过调节血管内皮生长因子A、C的表达而影响胰腺癌细胞的生物学特性,抑制癌细胞的增殖,促进其凋亡、死亡或进展、恶化.  相似文献   
36.
Human tumor–infiltrating lymphocytes (TILs) derived from pleural or ascitic fluid were incubated with recombinant interleukin 2 and transfected with human tumor necrosis factor (TNF) a gene by the lipofection procedure. The resulting TILs secreted significant amounts of TNF in the culture supernatant and exhibited cytotoxicity against established cell lines, such as K562 and Daudi, and autologous tumor cells. The TNF gene–transfected TILs exhibited an augmented killing of autologous tumor cells.  相似文献   
37.
Summary Tumor necrosis factor α (10−10–10−8M) had no effects on cyclic AMP production by the osteoblastic osteosarcomal cells, Saos-2 and G292, or normal rat calvarial cells. The cytokine did, however, inhibit the parathyroid hormone (PTH)-induced effect on cyclic AMP in the Saos-2 and normal rat osteoblastic cells. This inhibitory effect did not occur on prostaglandin E2-induced cyclic AMP increases in the osteoblastic cells. Interleukin-1 (10 U/ml −100 U/ml) did not produce any effect on basal levels or PTH-induced cyclic AMP increases in these cells.  相似文献   
38.
Arsenical necrosis of the jaws   总被引:3,自引:0,他引:3  
After a brief historical review of the use of arsenic in dental practice two cases of arsenical necrosis of the jaws, affecting the maxilla and mandible respectively, are reported. Both patients were treated conservatively over an extended period with excellent results. It is concluded that there is no justification, whatsoever, for the use of arsenic in modern dental practice and that, although prolonged, conservative treatment of chemical necrosis of the jaws is preferable to more radical treatment.  相似文献   
39.
急性脑梗塞患者血清肿瘤坏死因子水平变化的观察   总被引:7,自引:0,他引:7  
采用双抗体夹心ELISA法对30例正常对照和36例急性脑梗塞患者血清肿瘤坏死因子(TNF)水平进行了检测。结果显示:急性脑梗塞组血清TNF水平显著高于正常对照组,血清TNF水平变化与脑梗塞容积大小密切相关,恢复期血清TNF水平显著降低。结果提示,TNF参与了脑梗塞发生后病理变化过程,检测血清TNF对判定脑梗塞容积大小有一定的临床意义。  相似文献   
40.
Conclusion The mechanisms that regulate regeneration of kidney epithelial cells after acute tubular necrosis are poorly understood. Repair of the nephron can take place in the adverse systemic metabolic setting caused by failure of renal function. This clinical observation suggests that factors released at the site of the tubular insult can mediate repair. Studies carried out in this and other laboratories show that kidney epithelial cells can release and respond to polypeptide growth factors which may thereby contribute to renal regeneration by autocrine and paracrine mechanisms. Specific growth factors secreted by cells and deposited in the tubular basement membrane prior to injury may subsequently participate in nephron repair. In addition, adenine nucleotides released from injured or dying cells at the injury site or provided exogenously could stimulate surviving renal epithelial cells at the edges of the wound to migrate along the basement membrane to rapidly reepithelialize the nephron and subsequently initiate mitogenesis to replace cells lost by necrosis.The nephrotoxic effect of many agents used in cancer chemotherapy and the older age of patients undergoing complicated surgical procedures has increased the incidence of ARF, whereas the mortality rate has not changed since the early 1950s [22]. Thus there is considerable need for innovative therapeutic strategies. An important goal of future research efforts is to identify new growth factors that facilitate migration, differentiation, and proliferation of renal epithelial cells at sites of tubular necrosis. Isolation and use of these agents in combination with dialysis and nutritional support could speed renal regeneration and thereby improve the outcome in patients with this condition.Abbreviations ARF acute renal failure - ECM extracellular matrix - EGF epidermal growth factor - FGF fibroblast growth factor - IGF insulin-like growth factor - MGSA melanocyte growth-stimulating activity - PDGF platelet-derived growth factor - IGF transforming growth factor  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