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   28464篇
  免费   1276篇
  国内免费   215篇
耳鼻咽喉   813篇
儿科学   1921篇
妇产科学   914篇
基础医学   2175篇
口腔科学   1523篇
临床医学   2259篇
内科学   4814篇
皮肤病学   738篇
神经病学   1835篇
特种医学   1185篇
外国民族医学   3篇
外科学   6044篇
综合类   750篇
现状与发展   2篇
一般理论   10篇
预防医学   1142篇
眼科学   837篇
药学   1678篇
  4篇
中国医学   470篇
肿瘤学   838篇
  2024年   32篇
  2023年   302篇
  2022年   342篇
  2021年   618篇
  2020年   425篇
  2019年   514篇
  2018年   799篇
  2017年   725篇
  2016年   802篇
  2015年   739篇
  2014年   1061篇
  2013年   1401篇
  2012年   1748篇
  2011年   1940篇
  2010年   1030篇
  2009年   670篇
  2008年   1433篇
  2007年   1695篇
  2006年   1669篇
  2005年   1755篇
  2004年   1744篇
  2003年   1708篇
  2002年   1621篇
  2001年   1060篇
  2000年   1129篇
  1999年   730篇
  1998年   269篇
  1997年   216篇
  1996年   176篇
  1995年   109篇
  1994年   86篇
  1993年   64篇
  1992年   146篇
  1991年   107篇
  1990年   98篇
  1989年   90篇
  1988年   76篇
  1987年   74篇
  1986年   85篇
  1985年   64篇
  1984年   47篇
  1983年   41篇
  1979年   37篇
  1978年   27篇
  1974年   44篇
  1973年   29篇
  1972年   25篇
  1971年   26篇
  1970年   29篇
  1969年   25篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Proto-oncogenes, growth factors/receptors, and tumour suppressor genes were analysed in malignant metastatic insulinomas. Normal pancreas showed only a moderate immunoreaction for c-myc proto-oncogene and a strong reaction for insulin. Benign insulinomas were slightly or moderately positive for transforming growth factor a (TGFα), weakly positive for epidermal growth factor receptor (EGF-R), and strongly positive for c-myc and insulin. In malignant insulinomas, besides a strong immunoreaction for c-myc and TGFα, activation of c-K-ras and overexpression of p53 protein were found. Insulin reaction was moderate or strong. Three out of six malignant insulinomas displayed a c-K-ras point mutation at codon 12. All mutations were guanine to cytosine transversion, resulting in amino acid substitution, glycine to arginine. Mutations were present in metastatic insulinomas only. Patients with mutated c-K-ras oncogene had overexpression of p53 protein as well as c-myc and TGFα overexpression. Our results support the view that malignant progression is a consequence of more than one genetic lesion and suggest that activation of myc, TGFα, and ras genesα plays a role in a multistep process of tumour progression, perhaps serving as an initiating event.  相似文献   
82.
83.
By means of light, scanning electron microscopy and planimetry, the pathomorphology of gastric ulcers (GU) was investigated in patients who had died from liver cirrhosis (LC) and in rats with experimental portal hypertension (PH). It was noticed that GU are frequent (13.3%) in patients with LC. Experimental GU induced in rats with PH persist longer and their areas are larger than in ulcers without cirrhosis. The treatment of ulcers through abdominal wall with low-intensive infrared laser irradiation (LILR) causes significant acceleration of their epithelialization in the rat without cirrhosis. Ulcers in the animals with cirrhosis do not repair under LILR influence, but their area significantly decreases after forming collateral shunting. The congestion in the portal system is the main pathogenetic element in gastroesophageal ulcerogenesis. The laser therapy without decreasing portal hypertension is not efficient.  相似文献   
84.
BACKGROUND: Aeroallergen sampling provides information regarding the onset, duration and severity of the pollen season that clinicians use to guide allergen selection for skin testing and treatment. OBJECTIVES: This atmospheric survey reports (1) airborne pollen contributions in Adana in one-year period (2) pollen onset, duration and peak level (3) the relationship between airborne pollen and selected meteorological variables and; (4) effects on symptoms in pollen allergic children. METHODS: Pollen sampling was performed with a volumetric Burkard Spore Trap. Meteorological data were measured daily from April 2001 to April 2002. Asthma symptom scores were investigated in 186 pollen allergic children that were on follow up in pediatric allergy outpatient clinics during same period. RESULTS: Average measurements included 82.5% tree pollen, 7.7% grass pollen and 9.8% herb pollen 54 taxa were identified during one year. The most prominent tree pollens were Cupressaceae, Eucalyptus and Pinus. The most common herb was Chenopodiaceae pollen family. When airborne pollen levels were examined in relation to single meteorological conditions; daily variations in total pollen counts were not significantly correlated with any variable studied (humidity, rainfall, temperature and wind) (p > 0.05). On the other hand, statistically significant relationship between pollen concentration and symptom scores were found (p > 0.05). Positive correlations were seen between both Gramineae and Herb pollen, and humidity and rainfall from March to July. However, positive correlations were detected between tree pollen counts and temperature and humidity in May and June. CONCLUSION: This survey is the first volumetric airborne pollen analysis conducted in the survey area in Adana. This study suggested that the effects of weather on pollen count and symptom scores in this population could not be clearly identified with the evaluation of one-year data. However, pollen counts had effect on allergic symptoms in pollen allergic children. Examination of the complex interaction of multiple whether parameters would perhaps more fully elucidate the relationship between meteorology and aerobiology and provide the clinician with information necessary to forecast pollen prevalence. An awareness of the ever chancing, local aeroallergen patterns requires regular monitoring. Such awareness serves as a useful guide in the effective testing and treatment of atopic patients.  相似文献   
85.
A Western blot to detect anti-HSP70 autoantibodies has been reported to be of diagnostic value for immune-mediated hearing loss patients. While setting up this Western blot in our lab, we detected two main problems. First, some patients were positive for antibodies to a 70-kDa protein when tested against a whole cell lysate, but negative if the antigen used was purified HSP70. Second, if high amounts of purified HSP70 were loaded on the gel, both patients and healthy controls were positive. We have developed and optimized an ELISA as an alternative to the Western blot. This assay is more appropriate to identify positive and negative individuals because it is semi-quantitative. The ELISA is also more sensitive, requiring very low concentrations of the antigen and thus minimizing false positives. Finally, we demonstrated that immune-mediated hearing loss patients recognize mainly the native form of HSP70, a fact that potentially leads to false negatives when a denaturing Western blot assay is used for diagnosis. To test the diagnostic value of the ELISA, we performed a blind test with 70 hearing loss patients, as well as 30 healthy controls. A sensitivity of 84% and a specificity of 93% were obtained, superior to what has been reported so far for the Western blot.  相似文献   
86.
Several real-time PCR procedures for the detection and genotyping of oocysts of Cryptosporidium parvum were evaluated. A 40-cycle amplification of a 157-bp fragment from the C. parvum beta-tubulin gene detected individual oocysts which were introduced into the reaction mixture by micromanipulation. SYBR Green I melting curve analysis was used to confirm the specificity of the method when DNA extracted from fecal samples spiked with oocysts was analyzed. Because C. parvum isolates infecting humans comprise two distinct genotypes, designated type 1 and type 2, real-time PCR methods for discriminating C. parvum genotypes were developed. The first method used the same beta-tubulin amplification primers and two fluorescently labeled antisense oligonucleotide probes spanning a 49-bp polymorphic sequence diagnostic for C. parvum type 1 and type 2. The second genotyping method used SYBR Green I fluorescence and targeted a polymorphic coding region within the GP900/poly(T) gene. Both methods discriminated between type 1 and type 2 C. parvum on the basis of melting curve analysis. To our knowledge, this is the first report describing the application of melting curve analysis for genotyping of C. parvum oocysts.  相似文献   
87.
The familial paraganglioma syndrome is an autosomal dominant disorder characterized by the presence of carotid body paragangliomas and, less frequently, paragangliomas of the glomus jugulare, glomus vagale, and adrenal pheochromocytomas. Germline mutations of the genes for succinate dehydrogenase subunits D, B, or C (SDHD, SDHB, SDHC) have been identified in some kindreds with familial paraganglioma. In this study, we report the clinicopathologic features of four different kindreds with familial paraganglioma, which were screened for germline mutations in the SDHD gene. DNA was obtained from tumor and normal tissue, as well as from peripheral blood. Mutation analysis was performed by single-strand conformation polymorphism analysis and DNA sequencing. SDHD germline mutations were detected in the affected family members of the four families, as well as in several asymptomatic carriers. An identical mutation in exon 4 of SDHD (334-337delACTG) was identified in two apparently unrelated kindreds. The third family showed a germline mutation in exon 2 (W43X). The mutations present in these three families had been previously described in Spanish families, suggesting a founder effect. The fourth family exhibited a mutation in exon 2 of SDHD (170-171delTT), which had not been previously identified. The affected family members of the four kindreds showed paragangliomas, located in the head and neck region, and all of them were benign. These results confirm that genetic testing of SDHD may be a powerful tool for the identification of the syndrome in patients with multiple or bilateral paragangliomas.  相似文献   
88.
We have previously shown that the selection of haplotype tag single nucleotide polymorphisms (htSNPs) and their statistical analysis in a multi-locus transmission/disequilibrium test (TDT) results in a more cost-effective genotyping strategy in disease association studies of genes by minimising redundancy due to linkage disequilibrium between SNPs. Further savings can be achieved by the use of a two-stage genotyping strategy. This approach is illustrated here in conjunction with the multi-locus TDT in determining whether common alleles of the immune regulatory genes RANK and its ligand TRANCE (RANKL) are associated with type 1 diabetes (T1D). A saving of approximately 75% of potential genotyping reactions could be made with minimal loss of power. There was little evidence from our analysis for association between the TRANCE and RANK genes and T1D in the populations tested.  相似文献   
89.
秦巴山区初中学生心理健康状况调查研究   总被引:11,自引:0,他引:11  
目的 了解秦巴山区初中学生心理健康状况及其影响的主要因素。方法 采用 SCL-90临床症状自评量表随机对陕西省安康地区双溪乡初中学生进行心理健康测查。结果 秦巴山区双溪乡初中学生心理健康状况与全国初中学生心理健康常模比较 ,并未出现显著性差异 ;影响初中男生心理健康因素从大到小的顺序为 :抑郁 >躯体化 >焦虑 >强迫 >精神病性 >恐怖 >人际关系 >偏执 >其它 >敌对 ;影响女生心理健康因素从大到小的顺序为 :抑郁 >躯体化 >焦虑 >人际关系>强迫 >精神病性 >恐怖 >敌对 >其它 >偏执。结论 秦巴山区初中学生心理健康状况良好。影响秦巴山区初中学生心理健康的最主要因素为 :抑郁、躯体化和焦虑。  相似文献   
90.
Adhesion molecules are important for leukocyte extravasation and for the delivery of costimulatory signals in T cell activation. We therefore interfered in the immune process leading to islet inflammation in diabetes prone NOD mice by oral vaccination with plasmid DNA encoding soluble ICAM-1. Female NOD mice were treated orally with ICAM-1, TGF-beta, or control plasmid DNA and received a single injection of cyclophosphamide for synchronization and acceleration of the disease process in the pancreas. Quantitative RT-PCR analysis of pancreatic mRNA showed that cyclophosphamide induced the expression of Th1 cytokines (IFN-gamma and IL-12p40) in vehicle- or control plasmid-treated mice. Treatment with ICAM-1 and TGF-beta DNA resulted in increased levels of IL-10 mRNA in the pancreas, indicating an anti-inflammatory regulatory immune response. Histological analysis of pancreatic islets showed that the DNA treatment did not alter islet infiltration in response to cyclophosphamide. Hence vaccination with the ICAM-1 plasmid had not suppressed leukocyte migration but rather modulated lymphocyte activity, similarly as seen for the TGF-beta-encoding plasmid. Neither of the three plasmids caused recognizable changes in cytokine expression in the small intestine, Peyer's patches, or mesenteric lymph nodes. We conclude that oral vaccination with DNA encoding immunoregulatory molecules such as ICAM-1 and TGF-beta represents an approach for modulating the ongoing inflammatory process in the pancreas of diabetes prone NOD mice.  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