首页 | 官方网站   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   34178篇
  免费   3376篇
  国内免费   2715篇
医药卫生   40269篇
  2024年   119篇
  2023年   550篇
  2022年   1346篇
  2021年   1666篇
  2020年   1273篇
  2019年   1190篇
  2018年   1184篇
  2017年   1052篇
  2016年   1089篇
  2015年   1566篇
  2014年   1926篇
  2013年   1782篇
  2012年   2532篇
  2011年   2804篇
  2010年   1850篇
  2009年   1636篇
  2008年   1907篇
  2007年   1915篇
  2006年   1696篇
  2005年   1595篇
  2004年   1261篇
  2003年   1352篇
  2002年   1250篇
  2001年   940篇
  2000年   859篇
  1999年   774篇
  1998年   477篇
  1997年   424篇
  1996年   358篇
  1995年   319篇
  1994年   242篇
  1993年   176篇
  1992年   202篇
  1991年   153篇
  1990年   141篇
  1989年   123篇
  1988年   106篇
  1987年   111篇
  1986年   81篇
  1985年   71篇
  1984年   42篇
  1983年   23篇
  1982年   11篇
  1981年   11篇
  1980年   7篇
  1979年   15篇
  1977年   5篇
  1971年   5篇
  1964年   4篇
  1931年   6篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
MircroRNA functions as a tumor suppressor or a promoter in cholangiocarcinoma (CCA). Researchers have found that miR-203 functioned as tumor suppressor in many types of cancer. However, the role of miR-203 that plays in CCA remains to be clarified. We aimed to detect the expression level and the prognostic significance of miR-203 in CCA tissues. qRT-RCR was performed to examine the miR-203 expression levels in CCA tissue specimens and corresponding normal tissues. Our findings suggest that miR-203 expression was an independent poor prognostic factor for CCA patient overall survival. Therefore, miR-203 may serve as a valuable prognostic marker and promising treatment target for CCA.  相似文献   
992.
We conducted a study to analyze the association of three common SNPs of IL-17A rs2275913 and rs3748067 and IL-17F rs763780 gene polymorphisms with the risk of cervical cancer in a Chinese population. Our study included 352 cervical cancer patients and 352 controls between January 2013 and December 2014. Genotyping of IL-17A rs2275913 and rs3748067 and IL-17F rs763780 genes was performed by multiplex PCR assays using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). By χ2 test, there was significantly difference in the genotype distribution of IL-17A rs2275913 between cervical cancer patients and control subjects (χ2=11.45, P=0.003). By conditional logistic regression analysis, we found that individuals with the GA and AA genotypes were associated with an increased risk of cervical cancer when compared with the GG genotype in codominant model, and the adjusted Ors (95% CI) were 1.57 (1.13-2.18) and 2.01 (1.15-3.49), respectively. In dominant model, we found that the GA+AA genotype of rs2275913 was correlated with a moderate increased risk of cervical cancer compared with the GG genotype (OR=1.64, 95% CI=1.20-2.24). We only found significant interaction between rs2275913 polymorphism and HPV-16 or 18 infection in the risk of cervical cancer (P for interaction <0.05). In conclusion, our study suggests that IL-17A rs2275913 polymorphism may affect the development of cervical cancer in codominant and dominant models, and this gene polymorphism has interaction with HPV-16 or 18 infection.  相似文献   
993.
994.
Objective: To investigate the relationship between Surfactant protein B (SP-B) gene polymorphisms and bronchopulmonary dysplasia (BPD) development in preterm infants of China Han ethnic population. Methods: SP-B gene polymorphisms were studied in 134 neonates who were born at < 32 weeks of gestation, with the diagnosis of BPD and in a control group of 168 preterm infants without BPD. Genotyping for SP-B was performed by polymerase chain reaction (PCR) and gene sequencing. Results: In this study, three of the SNP genotypes, -18C/A, 1580C/T and 4564T/C were common identified in SP-B gene. The -18C/A genotype was found to be significantly associated with BPD (χ2 = 10.741, P < 0.01), with P < 0.01 for the dominant model (OR = 1.712, 95% CI = 1.228-2.3894) and the allelic model (OR = 1.787, 95% CI = 1.276-2.502). The 1580C/T genotype was found to be associated with BPD (χ2 = 7.014, P < 0.05), with P < 0.05 for the dominant model (OR = 0.752, 95% CI = 0.593-0.954) and P < 0.01 for the allelic model (OR = 0.706, 95% CI = 0.548-0.909). The 4564T/C genotypes and alleles were found not to be associated with BPD (χ2 = 3.399 and 3.227, P > 0.05). Conclusion: SP-B -18C/A and 1580C/T polymorphisms are associated with BPD. The 1580C/T polymorphism was protective while the -18C/A polymorphism increased the risk for BPD. SP-B 4564T/C polymorphism is not associated with BPD.  相似文献   
995.
Recurrent oral ulcer seriously threatens patients’ daily life and health. This study investigated potential genes and pathways that participate in the pathogenesis of recurrent oral ulcer by high throughput bioinformatic analysis. RT-PCR and Western blot were applied to further verify screened interleukins effect. Recurrent oral ulcer related genes were collected from websites and papers, and further found out from Human Genome 280 6.0 microarray data. Each pathway of recurrent oral ulcer related genes were got through chip hybridization. RT-PCR was applied to test four recurrent oral ulcer related genes to verify the microarray data. Data transformation, scatter plot, clustering analysis, and expression pattern analysis were used to analyze recurrent oral ulcer related gene expression changes. Recurrent oral ulcer gene microarray was successfully established. Microarray showed that 551 genes involved in recurrent oral ulcer activity and 196 genes were recurrent oral ulcer related genes. Of them, 76 genes up-regulated, 62 genes down-regulated, and 58 genes up-/down-regulated. Total expression level up-regulated 752 times (60%) and down-regulated 485 times (40%). IL-2 plays an important role in the occurrence, development and recurrence of recurrent oral ulcer on the mRNA and protein levels. Gene microarray can be used to analyze potential genes and pathways in recurrent oral ulcer. IL-2 may be involved in the pathogenesis of recurrent oral ulcer.  相似文献   
996.
A variety of CTX-M-type extended-spectrum β-lactamases (ESBLs), including hybrid ones, have been reported in China that are uncommon elsewhere. To better characterize the substrate profiles and enzymatic mechanisms of these enzymes, we performed comparative kinetic analyses of both parental and hybrid CTX-M enzymes, including CTX-M-15, -132, -123, -64, -14 and -55, that are known to confer variable levels of β-lactam resistance in the host strains. All tested enzymes were susceptible to serine β-lactamase inhibitors, with sulbactam exhibiting the weakest inhibitory effects. CTX-M-55, which differs from CTX-M-15 by one substitution, A77V, displayed enhanced catalytic activity (kcat/Km) against expanded-spectrum cephalosporins (ESCs). CTX-M-55 exhibits higher structure stability, most likely by forming hydrophobic interactions between A77V and various key residues in different helices, thereby stabilizing the core architecture of the helix cluster, and indirectly contributes to a more stable active site conformation, which in turn shows higher catalytic efficiency and is more tolerant to temperature change. Analyses of the hybrids and their parental prototypes showed that evolution from CTX-M-15 to CTX-M-132, CTX-M-123, and CTX-M-64, characterized by gradual enhancement of catalytic activity to ESCs, was attributed to introduction of different substitutions to amino acids distal to the active site of CTX-M-15. Similarly, the increased hydrolytic activities against cephalosporins and sensitivity to β-lactamase inhibitors, clavulanic acid and sulbactam, of CTX-M-64 were partly due to the amino acids that were different from CTX-M-14 and located at both the C and N termini of CTX-M-64. These data indicate that residues distal to the active site of CTX-Ms contributed to their enhanced catalytic activities to ESCs.  相似文献   
997.
998.
目的:观察活血通脉胶囊对冠心病心血瘀阻证患者血浆小分子代谢产物的调节作用。方法采用前瞻性研究方法,选择2009年1月至2013年12月在天津市大港地区就诊的136例冠心病心血瘀阻证患者,按简单随机抽样方法分成两组。对照组(68例)采用硝酸酯类、β受体阻滞剂、钙离子拮抗剂及肠溶阿司匹林等常规疗法;活血通脉胶囊组(68例)在常规治疗基础上给予活血通脉胶囊,每次4粒(每粒0.25 g),每日3次,30 d为1个疗程,共3个疗程。评定两组治疗后临床疗效和心电图疗效;采用酶联免疫吸附试验(ELISA)检测血浆和肽素、肿瘤坏死因子-α(TNF-α)及白细胞介素-10(IL-10)水平,计算TNF-α/IL-10比值。结果活血通脉胶囊组临床疗效及心电图疗效均明显高于对照组〔临床总有效率:89.71%(61/68)比80.88%(55/68);心电图总有效率:57.35%(39/68)比48.53%(33/68),均P<0.05〕。两组治疗后和肽素及TNF-α/IL-10比值均较治疗前明显降低,且以活血通脉胶囊组降低更显著〔和肽素(ng/L):0.22±0.04比0.31±0.05,TNF-α/IL-10比值:0.49±0.11比0.65±0.09,均P<0.05〕。结论在常规疗法基础上加用活血通脉胶囊能通过降低和肽素水平及TNF/IL-10比值来改善冠心病心血瘀阻证患者的治疗效果。  相似文献   
999.
目的:利用复合松质骨基质(Cancellous bone matrix ,CBM)的中空多孔钛假体(Hollow porous titanium prostheses, HPTP)观察兔体内假体周围及内部骨生成情况,探讨人工假体与骨质整合的改进方法。方法设计中空多孔(孔径2 mm)和无孔两种假体,表面行羟基磷灰石(Hydroxyapatite ,HA)喷涂。实验组分为无孔假体组(A组)、HPTP组(B组)和HPTP+CBM组(C组),每组16例。将假体分别植入48只4~6个月龄新西兰大白兔右侧股骨外侧髁,饲养至第3、8、12周时取材,以X线、显微镜、电镜及形态计量软件观察复合假体表面及内部骨生成情况。采用SPSS13.0进行t检验分析。结果三组植入物外表面HA涂层的组织生长情况类似;A组无孔,未见骨长入,B组和C组中骨组织最终可长入假体2 mm大的圆孔;各时间点C组中空腔内骨生长率均明显高于B组(P<0.01)。结论骨质可经HPTP假体孔洞长入腔内,达到交锁固定,较无孔假体更稳定;中空腔复合CBM后可明显加快骨长入并诱导骨生成,使假体与骨质更好整合。  相似文献   
1000.
目的对比局部置管溶栓和外周静脉溶栓治疗在下腔静脉滤器血栓形成中的溶栓疗效,缩短滤器植入时间,提高滤器取出率,降低滤器永久植入后中远期合并症。方法采用单中心前瞻性研究的方法,收集2013年2月至2014年8月期间北京积水潭医院血管外科收治的创伤性下肢骨折合并深静脉血栓并放置可回收性腔静脉滤器(Opt Ease)的患者,下腔静脉造影或彩超发现滤器下血栓≥1.0 cm者,采用随机数字表法分组,进行外周溶栓或导管溶栓治疗,对滤器的取出率进行对比分析讨论。结果外周溶栓组30例,滤器取出11例,取出率36.7%,导管溶栓组30例,滤器取出24例,取出率80.0%,导管溶栓组取出率明显高于外周溶栓取出率(P<0.05);两组间溶栓治疗后血栓大小变化的对比,导管溶栓组的溶栓效果优于外周溶栓组(P<0.05)。滤器取出后无再发肺栓塞表现。结论在下腔静脉滤器血栓形成中局部置管溶栓效果明显优于外周静脉溶栓治疗。  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-23

京公网安备 11010802026262号