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   81506篇
  免费   7166篇
  国内免费   4905篇
医药卫生   93577篇
  2024年   86篇
  2023年   786篇
  2022年   1441篇
  2021年   3117篇
  2020年   2492篇
  2019年   2174篇
  2018年   2298篇
  2017年   2330篇
  2016年   2324篇
  2015年   3580篇
  2014年   4547篇
  2013年   4931篇
  2012年   7135篇
  2011年   7303篇
  2010年   5735篇
  2009年   4865篇
  2008年   5450篇
  2007年   5310篇
  2006年   5014篇
  2005年   4294篇
  2004年   3368篇
  2003年   3318篇
  2002年   2931篇
  2001年   2151篇
  2000年   1491篇
  1999年   1078篇
  1998年   655篇
  1997年   637篇
  1996年   454篇
  1995年   395篇
  1994年   292篇
  1993年   202篇
  1992年   208篇
  1991年   199篇
  1990年   140篇
  1989年   128篇
  1988年   117篇
  1987年   103篇
  1986年   80篇
  1985年   77篇
  1984年   35篇
  1983年   31篇
  1982年   24篇
  1981年   22篇
  1980年   20篇
  1979年   34篇
  1978年   19篇
  1977年   17篇
  1974年   23篇
  1973年   21篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Resistance to chemotherapy is a major challenge for the treatment of patients with colorectal cancer (CRC). Previous studies have found that microRNAs (miRNAs) play key roles in drug resistance; however, the role of miRNA‐373‐3p (miR‐375‐3p) in CRC remains unclear. The current study aimed to explore the potential function of miR‐375‐3p in 5‐fluorouracil (5‐FU) resistance. MicroRNA‐375‐3p was found to be widely downregulated in human CRC cell lines and tissues and to promote the sensitivity of CRC cells to 5‐FU by inducing colon cancer cell apoptosis and cycle arrest and by inhibiting cell growth, migration, and invasion in vitro. Thymidylate synthase (TYMS) was found to be a direct target of miR‐375‐3p, and TYMS knockdown exerted similar effects as miR‐375‐3p overexpression on the CRC cellular response to 5‐FU. Lipid‐coated calcium carbonate nanoparticles (NPs) were designed to cotransport 5‐FU and miR‐375‐3p into cells efficiently and rapidly and to release the drugs in a weakly acidic tumor microenvironment. The therapeutic effect of combined miR‐375 + 5‐FU/NPs was significantly higher than that of the individual treatments in mouse s.c. xenografts derived from HCT116 cells. Our results suggest that restoring miR‐375‐3p levels could be a future novel therapeutic strategy to enhance chemosensitivity to 5‐FU.  相似文献   
22.
Abstract

Background

Comorbidities are commonly seen in patients with coronavirus disease 2019 (COVID-19), but the clinical implication is not yet well-delineated. We aim to characterize the prevalence and clinical implications of comorbidities in patients with COVID-19.  相似文献   
23.
Ferroptosis is an iron-dependent novel cell death pathway. Deferoxamine, a ferroptosis inhibitor, has been reported to promote spinal cord injury repair. It has yet to be clarified whether ferroptosis inhibition represents the mechanism of action of Deferoxamine on spinal cord injury recovery. A rat model of Deferoxamine at thoracic 10 segment was established using a modified Allen's method. Ninety 8-week-old female Wistar rats were used. Rats in the Deferoxamine group were intraperitoneally injected with 100 mg/kg Deferoxamine 30 minutes before injury. Simultaneously, the Sham and Deferoxamine groups served as controls. Drug administration was conducted for 7 consecutive days. The results were as follows:(1) Electron microscopy revealed shrunken mitochondria in the spinal cord injury group.(2) The Basso, Beattie and Bresnahan locomotor rating score showed that recovery of the hindlimb was remarkably better in the Deferoxamine group than in the spinal cord injury group.(3) The iron concentration was lower in the Deferoxamine group than in the spinal cord injury group after injury.(4) Western blot assay revealed that, compared with the spinal cord injury group, GPX4, xCT, and glutathione expression was markedly increased in the Deferoxamine group.(5) Real-time polymerase chain reaction revealed that, compared with the Deferoxamine group, mRNA levels of ferroptosis-related genes Acyl-CoA synthetase family member 2(ACSF2) and iron-responsive element-binding protein 2(IREB2) were up-regulated in the Deferoxamine group.(6) Deferoxamine increased survival of neurons and inhibited gliosis. These findings confirm that Deferoxamine can repair spinal cord injury by inhibiting ferroptosis. Targeting ferroptosis is therefore a promising therapeutic approach for spinal cord injury.  相似文献   
24.
25.
张莲  杨崇康  罗启鹏  刘佳  陈严平  沈勇 《中草药》2020,51(3):588-593
目的对毛茛科乌头属药用植物乌头Aconitum carmichaelii地上部分进行化学成分研究。方法乌头干燥的茎叶用甲醇回流提取,所得的浸膏用1.5%HCl溶解,醋酸乙酯萃取得总粗提取物。粗提物用各种柱色谱进行分离纯化,经光谱数据(~1H-NMR、~(13)C-NMR、MS)进行结构鉴定。结果从乌头地上部分分离得到15个化合物,分别鉴定为3-羧基-吲哚(1)、corchoionol C(2)、β-谷甾醇-3-O-β-D-葡萄糖苷-6′-棕榈酸酯(3)、松脂素(4)、(+)-N-formylnorglaucine(5)、oxoglaucidaline(6)、海罂粟碱(7)、(+)-cataline(8)、山柰酚-7-O-α-L-鼠李糖苷(9)、山柰酚-3-O-β-(2″-乙酰基)-半乳糖苷(10)、megastigmane(11)、山柰酚-7-O-α-L-阿拉伯糖苷(12)、山柰酚-3-O-β-D-吡喃木糖苷(13)、山柰酚-3-O-β-D-葡萄糖苷(14)、槲皮素-3-O-β-D-半乳糖苷(15)。结论化合物1~15均为首次从该植物的地上部分中分离得到,其中化合物1~3、5、6、8~15为首次从乌头中分离得到。  相似文献   
26.
Abstract

Oxidative stress (OS) has been proposed to play a role in the development of EMs. Peroxiredoxins are a family of antioxidant proteins that exhibit peroxidase activity in a thioredoxin-dependent manner, protecting cells against OS. The Western blotting results showed that the relative expression of PRDX4 was significantly increased in ectopic endometria compared with the normal endometria of EMs-free (p?<?.05). The H2O2 concentration was also significantly higher in the ectopic endometrium. PRDX4 siRNA was transfected into primary ectopic endometrial stromal cells (EESCs). The viability of the transfected EESCs was measured by CCK-8 assay, and the results showed significantly decreased cell viability. Furthermore, the apoptosis rate and ROS generation in flow cytometry assays were significantly increased after the knockdown of PRDX4 expression (p?<?.05). Scratch assays and transwell assays revealed that decreased expression of PRDX4 mediated by siRNA inhibited EESC migration and invasion. In conclusion, these findings indicate the potential role of PRDX4 in the development of EMs and PRDX4 as a possible therapeutic target for EMs treatment.  相似文献   
27.
Aim: To describe differences in the deep lateral orbital wall (specifically, trigone) between Chinese, Malay, Indian and Caucasian subjects

Methods: Single-centre retrospective Computed Tomogram (CT)-based study; 20 subjects of each ethnicity were used from existing databases, matched for gender, average age and laterality. Subjects below 16 years of age were excluded. DICOM image viewing software CARESTREAM Vue PACS (Carestream Health Inc., USA) and OsiriX version 7.5 (Pixmeo., Switzerland) were used to measure deep lateral wall length, thickness and volume, as well as orbital depth and statistical analyses performed using Statistical Package for Social Sciences version 21 (IBM, USA).

Results: In each group, there were 12 males (60%) and average age was not significantly different (p = 0.682–0.987). Using Chinese subjects as a reference, in Chinese, Malay, Indian and Caucasian subjects, mean trigone thickness was 13.68, 14.02, 11.60 (p < 0.001) and 13.80 mm, curved total wall length 45.23, 42.29 (p = 0.048), 41.91 (p = 0.020) and 45.00 mm, curved trigone length 23.03, 22.61, 17.19 (p = 0.011) and 18.76 mm (p = 0.030) and trigone volume 3120.97, 3221.01, 1613.66 (p < 0.001), 2498.46 mm3 (= 0.059) respectively. Similarly, perpendicular orbital depth was 27.54, 24.97, 22.12 (p = 0.001) and 25.93 mm and diagonal orbital depth was 34.19, 33.27, 29.48 (p = 0.01) and 34.63 mm respectively.

Conclusions: Indian and, to a lesser extent, Caucasian subjects have smaller trigones compared to their Chinese and Malay counterparts. Indian subjects also have shallower orbits and due care should be taken during decompression surgery.  相似文献   

28.
目的 探讨接受新辅助放化疗的局部晚期食管鳞癌患者新辅助放疗剂量与病理完全缓解(pCR)的关系。方法 收集2017-2019年间在四川大学华西医院肿瘤中心经病理确诊为食管鳞癌并接受新辅助放化疗和手术的 116例局部晚期患者临床资料。116例患者中 40~45Gy组 80例,≥45Gy组 36例,分析两组术后pCR率。结果 全组患者的pCR率为38.8%(45/116),40~45Gy组与≥45Gy组的pCR率分别为44%(35/80)和28%(10/36)(P=0.105)。结论 术前新辅助采用较高的放疗剂量不增加局部晚期食管鳞癌的pCR率,有必要进行前瞻性的临床研究确定合适的新辅助放疗剂量。  相似文献   
29.
30.
目的:探讨PI3K抑制剂ZSTK-474对结直肠癌细胞增殖和侵袭的影响。方法:采用不同浓度(0、1、2、4、6、8和10 μmol/L)ZSTK-474处理结直肠癌HT-29和HCT-116细胞24 h和48 h,CCK8法检测细胞增殖活性并计算出ZSTK-474在两株结直肠癌细胞中的半数抑制浓度(IC50)。根据IC50的值选用浓度为4 μmol/L的ZSTK-474作用HT-29和HCT-116细胞24 h,同时设置加入等量的0.1%DMSO为对照。采用平板克隆形成实验检测细胞增殖,流式细胞仪检测细胞凋亡,qRT-PCR检测细胞PI3K、Akt的mRNA水平,Western blot 检测细胞PI3K、Akt的蛋白水平。结果:ZSTK-474可明显抑制HT-29和HCT-116细胞的增殖,且呈时间和剂量依赖性。ZSTK-474可抑制HT-29和HCT-116细胞的侵袭能力,但不影响其凋亡。ZSTK-474处理HT-29和HCT-116细胞24 h后,PI3K和Akt的mRNA和蛋白表达水平均显著下降。结论:ZSTK-474能够抑制结直肠癌细胞增殖,并且能抑制其侵袭。  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