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   6952篇
  免费   514篇
  国内免费   121篇
耳鼻咽喉   75篇
儿科学   120篇
妇产科学   189篇
基础医学   903篇
口腔科学   132篇
临床医学   948篇
内科学   929篇
皮肤病学   117篇
神经病学   417篇
特种医学   207篇
外国民族医学   6篇
外科学   459篇
综合类   782篇
一般理论   1篇
预防医学   591篇
眼科学   158篇
药学   597篇
  15篇
中国医学   277篇
肿瘤学   664篇
  2024年   83篇
  2023年   146篇
  2022年   342篇
  2021年   483篇
  2020年   358篇
  2019年   263篇
  2018年   265篇
  2017年   270篇
  2016年   210篇
  2015年   360篇
  2014年   426篇
  2013年   412篇
  2012年   573篇
  2011年   596篇
  2010年   328篇
  2009年   282篇
  2008年   391篇
  2007年   363篇
  2006年   285篇
  2005年   251篇
  2004年   200篇
  2003年   183篇
  2002年   137篇
  2001年   60篇
  2000年   53篇
  1999年   51篇
  1998年   35篇
  1997年   34篇
  1996年   15篇
  1995年   13篇
  1994年   20篇
  1993年   15篇
  1992年   14篇
  1991年   9篇
  1990年   8篇
  1989年   10篇
  1988年   4篇
  1987年   4篇
  1986年   2篇
  1985年   2篇
  1984年   2篇
  1983年   3篇
  1982年   2篇
  1981年   3篇
  1980年   3篇
  1979年   3篇
  1976年   2篇
  1973年   2篇
  1968年   3篇
  1905年   2篇
排序方式: 共有7587条查询结果,搜索用时 12 毫秒
71.
Dermal synthesis, following sun exposure, is the main source of vitamin D. This study characterizes ambient UVB radiation relevant for vitamin D production in Europe. A biological weighing function was applied to data from the Tropospheric Emissions Monitoring Internet Service (TEMIS) for 46 capital cities over an 18-year period (2004–2021) to isolate wavelengths relevant for vitamin D production (D-UVB). Cumulative and weighted D-UVB (CW-D-UVB) were calculated to approximate seasonal vitamin D accumulation and diminution. Monthly 25(OH)D concentration measurements were extracted from published reports. All data were analyzed by location and time. Despite a moderate latitudinal range (35–64° N), we observed large—up to five-fold—regional differences: the highest mean diurnal D-UVB dose of 5.57 kJ/m2 (SD = 3.55 kJ/m2) was observed in Nicosia (Cyprus) and the lowest in Reykjavik (Iceland, 1.16 ± 1.29 kJ/m2). Seasonal differences in diurnal D-UVB dose were even more pronounced, with a median 36-fold difference between annual peak and trough depending on a location (range: 10- to 525-fold). The mean duration of “vitamin D winter” was 126 days but varied widely (4 to 215 days). Monthly CW-D-UVB and 25(OH)D changes were very strongly correlated: the changes in 25(OH)D concentration increased by 12.6 nmol/L for every 100 kJ/m2 increment of CW-D-UVB in population-based studies (r2 = 0.79, p-value = 1.16 × 10−37). Understanding the differences in D-UVB radiation can help understand determinants of vitamin D status and guide region- and season-specific safe and effective sunlight exposure recommendations and vitamin D supplementation guidelines.  相似文献   
72.
Nonsyndromic mental retardation (NSMR) is the diagnosis of exclusion in mentally retarded individuals without additional abnormalities. We have recently identified a protein-truncating mutation, G408fsX437, in the gene CC2D1A on chromosome 19p13.12 in nine consanguineous Israeli Arab families with severe autosomal recessive NSMR, and have developed a comprehensive prevention program among the at-risk population in the village. The subjects tested were healthy women who were invited to undergo the genetic screening test as a part of their routine pregnancy monitoring. One hundred and seventeen subjects reported a family history positive for mental retardation. We tested 524 pregnant or preconceptional women and found 47 carriers (approximately 1/11), whose spouses were then recommended to undergo testing. We identified eight carrier couples, who were given genetic counseling and offered prenatal diagnosis. Of all the marriages, 28.6% were consanguineous; 16.5% of the total were between first cousins. The high prevalence of the mutation can be explained both by the founder effect owing to the generally high consanguinity rate among the inhabitants of the village, and also because two families with excessive numbers of mentally retarded offspring were unacceptable as marriage partners by the rest of the families. This is the first example of the establishment of a large-scale genetic screening program for autosomal recessive NSMR, which was made possible owing to the high frequency of the specific causative mutation in this isolated population.  相似文献   
73.
74.
中国人群2型糖尿病合并骨质疏松常见危险因素的Meta分析   总被引:4,自引:0,他引:4  
目的了解中国人群2型糖尿病合并骨质疏松的常见危险因素。方法通过检索中国期刊网全文数据库(CNKI)、中国生物医学文献数据库搜集资料,应用Meta分析的方法对纳入文献的结果进行统计量的合并,计算标准化均数差(SMD)或加权均数差(WMD)及其95%CI。结果有26篇文献进入Meta分析,其中年龄、病程、体质量指数、糖化血红蛋白、空腹血糖、空腹胰岛素、餐后2 h胰岛素、尿白蛋白定量、碱性磷酸酶与2型糖尿病合并骨质疏松相关,但尚不能认为胰岛素敏感指数、24 h尿蛋白定量、血钙、血磷与2型糖尿病合并骨质疏松有关。结论年龄、病程、体质量指数、糖化血红蛋白、空腹血糖、空腹胰岛素、餐后2 h胰岛素、尿白蛋白定量、碱性磷酸酶是2型糖尿病合并骨质疏松的危险因素。  相似文献   
75.
Germline mutations in the tumour suppressor BRCA2 predispose to breast, ovarian and a number of other human cancers. Brca2‐deficient mouse models are used for preclinical studies but the pattern of genomic alterations in these tumours has not yet been described in detail. We have performed whole‐exome DNA sequencing analysis of mouse mammary tumours from Blg–Cre Brca2f/f Trp53f/f animals, a model of BRCA2‐deficient human cancer. We also used the sequencing data to estimate DNA copy number alterations in these tumours and identified a recurrent copy number gain in Met, which has been found amplified in other mouse mammary cancer models. Through a comparative genomic analysis, we identified several mouse Blg–Cre Brca2f/f Trp53f/f mammary tumour somatic mutations in genes that are also mutated in human cancer, but few of these genes have been found frequently mutated in human breast cancer. A more detailed analysis of these somatic mutations revealed a set of genes that are mutated in human BRCA2 mutant breast and ovarian tumours and that are also mutated in mouse Brca2‐null, Trp53‐null mammary tumours. Finally, a DNA deletion surrounded by microhomology signature found in human BRCA1/2‐deficient cancers was not common in the genome of these mouse tumours. Although a useful model, there are some differences in the genomic landscape of tumours arising in Blg–Cre Brca2f/f Trp53f/f mice compared to human BRCA‐mutated breast cancers. Therefore, this needs to be taken into account in the use of this model. Copyright © 2015 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.  相似文献   
76.
Loss-of-function variants in ANKRD11 were identified as the cause of KBG syndrome, an autosomal dominant syndrome with specific dental, neurobehavioural, craniofacial and skeletal anomalies. We present the largest cohort of KBG syndrome cases confirmed by ANKRD11 variants reported so far, consisting of 20 patients from 13 families. Sixteen patients were molecularly diagnosed by Sanger sequencing of ANKRD11, one familial case and three sporadic patients were diagnosed through whole-exome sequencing and one patient was identified through genomewide array analysis. All patients were evaluated by a clinical geneticist. Detailed orofacial phenotyping, including orthodontic evaluation, intra-oral photographs and orthopantomograms, was performed in 10 patients and revealed besides the hallmark feature of macrodontia of central upper incisors, several additional dental anomalies as oligodontia, talon cusps and macrodontia of other teeth. Three-dimensional (3D) stereophotogrammetry was performed in 14 patients and 3D analysis of patients compared with controls showed consistent facial dysmorphisms comprising a bulbous nasal tip, upturned nose with a broad base and a round or triangular face. Many patients exhibited neurobehavioural problems, such as autism spectrum disorder or hyperactivity. One-third of patients presented with (conductive) hearing loss. Congenital heart defects, velopharyngeal insufficiency and hip anomalies were less frequent. On the basis of our observations, we recommend cardiac assessment in children and regular hearing tests in all individuals with a molecular diagnosis of KBG syndrome. As ANKRD11 is a relatively common gene in which sequence variants have been identified in individuals with neurodevelopmental disorders, it seems an important contributor to the aetiology of both sporadic and familial cases.  相似文献   
77.
人乳头瘤病毒(HPV)感染与宫颈癌的发生密切相关,是宫颈癌发生的最主要诱发因素.预防性HPV疫苗是一种预防宫颈癌的新方法,其效果得到了多项临床试验的肯定.治疗性HPV疫苗的研发同样备受关注,目前治疗性疫苗的类型很多,但因其机制较复杂,大多仍处在实验阶段.  相似文献   
78.
We conducted a case-control study to evaluate the association of miR-146a rs2910164 (C>G), miR-149 rs2292832 (T>C), miR-196a2 rs11614913 (T>C) and miR-499 rs3746444 (T>C) polymorphisms with the risk of hepatocellular carcinoma. A total of 274 patients with HCC were collected between January 2013 and December 2014. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was taken to determine the polymorphism of miR-146a C>G, miR-149 T>C, miR-196a2 T>C and miR-499 T>C. By comparing with control groups, patients with HCC were more likely to be males (OR=2.01, 95% CI=1.38-2.95), have older age (OR=1.52, 95% CI=1.09-2.13), have a history of alcohol drinking (OR=2.09, 95% CI=1.49-2.93), and be infected with HBV (OR=32.98, 95% CI=19.70-55.46) and HCV (OR=56.26, 95% CI=23.28-152.98) infection. By conditional regression analysis, individuals carrying the TC and CC genotypes of miR-196a2 T>C were found to be associated with an elevated risk of HCC compared to the TT genotype, and the adjusted odds ratio were 1.50 (1.03-2.17) and 2.86 (1.60-5.16), respectively. Moreover, the TC+CC genotype was correlated with an increased risk of HCC (OR=1.69, 95% CI=1.19-2.41) compared to the wide-type genotype. In conclusion, our results suggested that miR-196a2 T>C polymorphism is associated with HCC risk in Chinese population.  相似文献   
79.
目的:探讨人组织激肽释放酶11基因(KLK11基因)在卵巢癌组织中的表达状况.方法:应用免疫组织化学及逆转录PCR方法检测KLK11基因在卵巢癌组织、卵巢良性肿瘤组织及正常卵巢组织中的表达状况,研究其与肿瘤分期、组织病理学分型等相关预后因素的关系.结果:KLK11 mRNA及其蛋白hK11均在卵巢上皮细胞中表达,在卵巢癌组织中的表达均低于其在正常卵巢组织和卵巢良性肿瘤组织的表达;hK11蛋白在浆液性卵巢癌组织的表达高于其他类型的卵巢癌组织(P=0.012);早期卵巢癌(Ⅰ/Ⅱ期)组织中hK11蛋白的表达明显高于晚期卵巢癌(Ⅲ/Ⅳ期)(P=0.010);hK11蛋白在卵巢癌组织的表达水平与肿瘤的病理分级无明显关系(P=0.747);高水平的KLK11基因表达与卵巢癌临床分期等预后因素有明显相关性.结论:在卵巢癌组织中存在KLK11基因的表达下调,提示KLK11基因在卵巢癌中表达失调,可能对卵巢癌的诊断有一定价值.  相似文献   
80.
The capacity of a K. pneumoniae membrane proteoglycan (Kp-MPG) and four of its chemically defined derivatives to activate human monocytes was studied by measuring immunoreactive IL-1 beta, IL-6 and tumour necrosis factor-alpha (TNF-alpha) in culture supernatants. Monocyte culture supernatants were also tested for their comitogenic activity on concanavalin A-stimulated thymocytes and for their cytotoxic activity on the mouse fibroblastic L929 cell line. The four Kp-MPG derivatives were: (i) an acylpoly(1-3)galactoside (APG); (ii) an APG preparation submitted to acid hydrolysis which removed all fatty acids but left intact the galactose chain of APG (GC-APG); (iii) a preparation obtained by mild alkaline hydrolysis, containing additional ester-linked C14 and C16 fatty acids bound to the APG molecule (EFA-APG); and (iv) a polymer of the latter compound (APG pol). Kp-MPG induced the synthesis of IL-1 beta, IL-6 and TNF-alpha with dose-responses and kinetics similar to those of Salmonella minnesota lipopolysaccharide (Sm-Re-LPS). APG pol and EFA-APG induced the secretion of the three cytokines with lower potency than Kp-MPG or Sm-Re-LPS. APG did not trigger any detectable cytokine production and GC-APG induced only borderline and inconsistent responses. Our data demonstrate the critical role of ester-linked C14 and C16 fatty acids in the triggering of monocyte response to Kp-MPG derivatives.  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