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   9159篇
  免费   800篇
  国内免费   411篇
耳鼻咽喉   151篇
儿科学   195篇
妇产科学   138篇
基础医学   1072篇
口腔科学   126篇
临床医学   1099篇
内科学   1293篇
皮肤病学   59篇
神经病学   413篇
特种医学   457篇
外国民族医学   1篇
外科学   920篇
综合类   1274篇
现状与发展   4篇
一般理论   2篇
预防医学   739篇
眼科学   246篇
药学   921篇
  12篇
中国医学   483篇
肿瘤学   765篇
  2024年   108篇
  2023年   165篇
  2022年   332篇
  2021年   401篇
  2020年   333篇
  2019年   301篇
  2018年   320篇
  2017年   293篇
  2016年   314篇
  2015年   407篇
  2014年   507篇
  2013年   518篇
  2012年   719篇
  2011年   767篇
  2010年   447篇
  2009年   372篇
  2008年   428篇
  2007年   466篇
  2006年   426篇
  2005年   425篇
  2004年   292篇
  2003年   270篇
  2002年   245篇
  2001年   178篇
  2000年   164篇
  1999年   215篇
  1998年   108篇
  1997年   101篇
  1996年   88篇
  1995年   81篇
  1994年   70篇
  1993年   51篇
  1992年   49篇
  1991年   62篇
  1990年   51篇
  1989年   49篇
  1988年   33篇
  1987年   33篇
  1986年   30篇
  1985年   29篇
  1984年   9篇
  1983年   10篇
  1981年   11篇
  1980年   7篇
  1979年   8篇
  1978年   7篇
  1975年   6篇
  1974年   14篇
  1973年   6篇
  1971年   6篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Wan R  Mo Y  Chien S  Li Y  Li Y  Tollerud DJ  Zhang Q 《Nanotoxicology》2011,5(4):568-582
Nickel is an important economic commodity, but it can cause skin sensitization and may cause lung diseases such as lung fibrosis, pneumonitis, bronchial asthma and lung cancer. With development of nanotechnology, nano-sized nickel (Nano-Ni) and nano-sized titanium dioxide (Nano-TiO?) particles have been developed and produced for many years with new formulations and surface properties to meet novel demands. Our previous studies have shown that Nano-Ni instilled into rat lungs caused a greater inflammatory response as compared with standard-sized nickel (5 μm) at equivalent mass concentrations. Nano-Ni caused a persistent high level of inflammation in lungs even at low doses. Recently, several studies have shown that nanoparticles can translocate from the lungs to the circulatory system. To evaluate the potential systemic effects of metal nanoparticles, we compared the effects of Nano-Ni and Nano-TiO? on matrix metalloproteinases 2 and 9 (MMP-2 and MMP-9) gene expression and activity. Our results showed that exposure of human monocyte U937 to Nano-Ni caused dose- and time- dependent increase in MMP-2 and MMP-9 mRNA expression and pro-MMP-2 and pro-MMP-9 activity, but Nano-TiO? did not. Nano-Ni also caused dose- and time- related increase in tissue inhibitor of metalloproteinases 1 (TIMP-1), but Nano-TiO? did not. To determine the potential mechanisms involved, we measured the expression of hypoxia inducible factor 1α (HIF-1α) in U937 cells exposed to Nano-Ni and Nano-TiO?. Our results showed that exposure to Nano-Ni caused HIF-1α accumulation in the nucleus. Furthermore, pre-treatment of U937 cells with heat shock protein 90 (Hsp90) inhibitor, 17-(Allylamino)-17-demethoxygeldanamycin (17-AAG), prior to exposure to Nano-Ni significantly abolished Nano-Ni-induced MMP-2 and MMP-9 mRNA upregulation and increased pro-MMP-2 and pro-MMP-9 activity. Our results suggest that HIF-1α accumulation may be involved in the increased MMP-2 and MMP-9 production in U937 cells exposed to Nano-Ni.  相似文献   
42.
耳鸣掩蔽治疗条件的测定   总被引:7,自引:1,他引:6  
目的 寻找耳鸣掩蔽治疗较为合适的掩蔽时间、掩蔽声类型的组合。方法 受试的27名耳蜗性耳鸣患者,平均分别来自于三个治疗点,并定为甲、乙、丙三组。按析因试验设计原理将掩蔽声设定为窄带噪声(nar-row band noise,NBN)、宽带噪声(wide band noise,WBN)和言语噪声(spech noisre,SN)三个因素,掩蔽时间设定为15、30、45min三个水平共九种组合,每组内患  相似文献   
43.
目的:探讨认知行为疗法对化疗癌症患儿治疗依从性及免疫功能的影响,为癌症患儿的心理护理提供依据。方法:采用便利抽样方法选取符合标准的癌症患儿50例,并按照癌症类型、分期和年龄进行配对,根据其意愿分为治疗组和对照组各25例。对照组只采用常规心理护理,治疗组采用认知行为疗法,干预时间共5周。干预前后,采用Frankl依从量表(Frankl compliance scale,FCS)、Houpt行为量表(Houpt behavior scale,HBS)和外周血淋巴细胞含量(peripheral blood lymphocyte content,PBLC)评估其治疗依从性及免疫功能,并对结果进行比较分析。结果:干预后,治疗组的治疗依从性(3.20±0.40)、NK细胞含量(natural kill cell,NKC;20.36±10.76)明显高于对照组的治疗依从性(2.72±0.61)及NK细胞含量(16.68±8.44),且差异具有统计学意义(t治疗依从性=3.256,P=0.002;t NK细胞含量=2.356,P=0.024)。T淋巴细胞含量较干预前明显增加(72.26±11.34 vs. 76.33±11.07;t=2.460,P=0.021),但对照组干预前后在治疗依从性及淋巴细胞含量上并无明显差异(均P >0.05)。结论:认知行为疗法通过纠正患儿对患癌事件的歪曲认知,可以增强治疗依从性,对提高免疫调节能力及改善预后有一定的积极作用。  相似文献   
44.
OBJECTIVE: To evaluate expectation and knowledge on obstetric ultrasound examination in the first and second trimester in a Chinese population. METHOD: A cross-sectional survey was conducted in a university obstetric clinic in Hong Kong. Chinese pregnant women who underwent the first trimester early scan sessions, or the second trimester anomaly scan sessions were invited to complete a self-administered questionnaire, which contained items on their knowledge, expectation, and sociodemographic characteristics. RESULTS: In all 276 eligible pregnant women (117 in the first trimester and 159 in the second trimester) were recruited. Although 249 women (90.2%) claimed they understood the indication of the ultrasound examination, only 93 of them were correct (33.7%). The median perceived overall-detection rate for structural abnormalities was 66.5%. Living in Hong Kong for more than 7 years was significantly associated with higher knowledge level and expectation from ultrasound examination. Attaining tertiary education level was also significantly associated with higher knowledge level. Over 90% of the pregnant women studied wished to know the fetal gender from the anomaly scan examination. CONCLUSION: Knowledge of Chinese pregnant women on ultrasound was generally unsatisfactory. Understanding their limitation of knowledge and expectations helps to devise appropriate education in the local setting.  相似文献   
45.
Background China is one of the high burden countries of Mycobacterium tuberculosis (TB) infection globally, with high incidence and mortality. We studied the molecular characteristics of rifampin (RIF) and isoniazid (INH) resistant Mycobacterium tuberculosis strains from Beijing, China, in order to find out the genetic marker for rapid detection of specific drug resistance. Methods Forty pansusceptible and 81 resistant strains of Mycobacterium tuberculosis isolated from Beijing, China during 2002-2005 were analyzed. The modified rifampin oligonucleotide (RIFO) assay based on reverse line blot hybridization was used to detect mutations in the 81 bp hot-spot region of rpoB gene, which is associated with RIF resistance. The INH resistance associated genes, regulatory region mab-inhA (-15C/T) and structural gene katG S315T were detected by reverse line blot hybridization and PCR-restriction fragment length polymorphism (RFLP) method respectively. All the strains were typed by spoligotying and the Beijing genotype was further subdivided by NTF locus analysis. The distribution of drug resistance associated mutations in the above genes was compared in these groups. Results Sixty-five (91.5%) of 71 RIF resistant and 52 (92.9%) of 56 multidrug-resistant (MDR, i.e. resistant to at least RIF and INH) strains were found to harbor mutations in the rpoB hot-spot region. No mutation was detected in RIF sensitive strains. The specificity and sensitivity of the modified RIFO assay were 100% and 91.5%, respectively, katG315 AGC〉ACC and inhA-15C〉T mutations were found in 40 (60.6%) and 10 (15.2%) of 66 INH resistant strains, respectively; 7.6% of INH-resistant strains had mutations in both of these genes. Therefore, a combined use of both katG315 and inhA-15 identified 68.2% of INH-resistant strains. The Beijing genotype accounted for 91.7% of total strains and was further subdivided into "modern" (76.6%) and "ancestral" (23.4%) group. There is no significant difference between "ancestral" and "modern" group in prevalance of drug resistance-associated gene mutations. Conclusions The hot-spot region of rpoB gene can be used as genetic marker for detection of RIF resistant strains; a combined use of both katG315 and inhA-15 can improve the detection rate of I NH resistant strains; the Beijing genotype is prevalent in Beijing, China; the modified RIFO assay can be a practical tool for rapid detection of RIF resistant and MDR isolates in the routine diagnostic work.  相似文献   
46.
李佳  陆会平  冯振博  莫伟嘉 《重庆医学》2013,(28):3393-3394,3397
目的筛选冻存慢病毒转染后稳转肝癌细胞株HepG2的最佳冻存液。方法采用甘油和二甲基亚砜(DMSO)2种不同冻存保护剂,以4种不同比例的冻存液分别冻存慢病毒转染后肝癌细胞HepG2及未转染的HepG2细胞,并对上述细胞复苏后的存活率及增殖能力进行比较分析。结果采用甘油为冻存保护剂时,冻存液[DMEM∶胎牛血清(FBS)∶甘油]比例为0∶9∶1的转染后细胞存活率最高(P=0.001);未转染细胞存活率与冻存液比例无关(P=0.293)。采用DMSO为冻存保护剂时,转染后细胞存活率为0%;未转染细胞存活率在60%及以上,且与冻存液比例无关(P=0.487)。冻存液中血清含量越高,复苏后细胞的增殖能力越强(P<0.05)。结论冻存慢病毒转染后的稳转肝癌细胞株HepG2的最佳冻存液为90%FBS+10%甘油。  相似文献   
47.
目的 研究姜黄素对A549细胞增殖的抑制作用,并探讨其可能的分子机制.方法 不同浓度姜黄素处理A549细胞后,分别用平板克隆形成实验、MTT法检测A549细胞的克隆形成数和增殖.20 μmol/L姜黄素处理A549细胞24、48、72 h后,FCM检测细胞周期;RT-PCR、Western blot检测P53、P21、PCNA及eIF4E mRNA和蛋白的表达水平.结果 20 μmol/L姜黄素可引起A549细胞S期阻滞,抑制细胞增殖,减少细胞的克隆形成数.20 μmol/L姜黄素作用A54924 h后P53、P21 mRNA和蛋白表达上调,48 h或72 h后变得尤明显.此外,20μmol/L姜黄素处理A549细胞48 h后可引起PCNA、eIF4E mRNA和蛋白表达水平下调,72 h后尤明显.结论 姜黄素可抑制A549的克隆形成数和细胞增殖,其机制可能与姜黄素促进P53和P21基因表达,抑制PCNA和eIF4E基因表达有关.  相似文献   
48.
目的 考察用纤维素酶-乙醇协同提取龙须藤总黄酮的最佳提取工艺条件.方法 在单因素分析的基础上进行Box-Behnken效应面优化,以龙须藤总黄酮提取率为指标,并采用Design expert 7.0.0软件对数据进行分析.结果 纤维素酶-乙醇协同提取龙须藤总黄酮的最佳工艺条件为:每1 g药材酶用量9.13 mg、酶解时间2.06 h、酶解温度51.03℃.在优化条件下,提取率平均值为19.24%(RSD为1.68%),与预测值19.02%接近.结论 纤维素酶-乙醇协同提取龙须藤总黄酮可获得较高的提取率.  相似文献   
49.
鼻灌洗在职业和环境医学中的应用   总被引:2,自引:0,他引:2  
鼻灌洗(nasallavage,NAL)是一种简便易行的检查方法,它可客观地反映呼吸系统的病理生理变化。由于NAL没有创伤性,可重复检查,因此特别适合于现场研究和以儿童作为研究对象的调查。自本世纪90年代以来,许多国家已将NAL用于环境医学与职业医学...  相似文献   
50.
The association between vitamin D and hemoglobin has been suggested. Vitamin D can affect erythropoiesis by the induction of erythroid progenitor cell proliferation and enhance iron absorption by regulating the iron-hepcidin-ferroportin axis in monocytes. However, this relationship in pregnant women is scarce. The purpose of this study was to investigate the association between plasma vitamin D levels with hemoglobin concentration in pregnant women considering each trimester and iron supplementation. The data were obtained from Zhoushan Pregnant Women Cohort, collected from 2011 to 2018. Plasma 25(OH)D was measured in each trimester using liquid chromatography–tandem mass spectrometry. Generalized estimating equations and multiple linear regressions were performed. Finally, 2962 pregnant women and 4419 observations in the first trimester were included in this study. Plasma 25(OH)D in first trimester (T1) (β = 0.06, p = 0.0177), second trimester (T2) (β = 0.15, p < 0.0001), and third trimester (T3) (β = 0.12, p = 0.0006) were positively associated with Hb. Association between plasma 25(OH)D levels in T1 and Hb concentration was positively associated with gestational age (β = 0.005, p = 0.0421). Pregnant women with VD deficiency in T1 (OR = 1.42, 95% CI: 1.07–1.88) or T2 (OR = 1.94, 95% CI: 1.30–2.89) presented an increased risk of anemia, compared with women without VD deficiency. Moreover, the significant relationship between VD and Hb was only observed among women with iron supplementation during pregnancy. Plasma 25(OH)D levels in each trimester were positively associated with Hb concentration. Iron supplementation might be an important factor affecting the relationship between VD and Hb.  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