全文获取类型
收费全文 | 384篇 |
免费 | 44篇 |
专业分类
耳鼻咽喉 | 3篇 |
儿科学 | 6篇 |
妇产科学 | 1篇 |
基础医学 | 91篇 |
口腔科学 | 10篇 |
临床医学 | 39篇 |
内科学 | 86篇 |
皮肤病学 | 9篇 |
神经病学 | 44篇 |
特种医学 | 17篇 |
外科学 | 20篇 |
综合类 | 9篇 |
预防医学 | 12篇 |
眼科学 | 10篇 |
药学 | 28篇 |
中国医学 | 2篇 |
肿瘤学 | 41篇 |
出版年
2020年 | 3篇 |
2019年 | 6篇 |
2018年 | 6篇 |
2017年 | 8篇 |
2016年 | 7篇 |
2015年 | 9篇 |
2014年 | 13篇 |
2013年 | 13篇 |
2012年 | 17篇 |
2011年 | 8篇 |
2010年 | 12篇 |
2009年 | 9篇 |
2008年 | 22篇 |
2007年 | 8篇 |
2006年 | 18篇 |
2005年 | 15篇 |
2004年 | 16篇 |
2003年 | 18篇 |
2002年 | 18篇 |
2001年 | 6篇 |
2000年 | 21篇 |
1999年 | 15篇 |
1998年 | 9篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 7篇 |
1993年 | 3篇 |
1992年 | 10篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 13篇 |
1976年 | 4篇 |
1974年 | 6篇 |
1973年 | 3篇 |
1972年 | 4篇 |
1970年 | 4篇 |
1967年 | 3篇 |
1966年 | 6篇 |
1931年 | 3篇 |
1930年 | 4篇 |
1927年 | 2篇 |
1926年 | 4篇 |
1925年 | 3篇 |
1924年 | 2篇 |
1922年 | 3篇 |
排序方式: 共有428条查询结果,搜索用时 15 毫秒
1.
2.
3.
Neurofibromatosis 1 (NF1) is an autosomal dominant disorder caused by genetic alterations of the NF1 gene on 17q11.2. About 30% of NF1 patients develop plexiform neurofibromas (PNFs), which often cause severe clinical deficits. To determine whether there is a certain genotype underlying PNFs or subtypes of PNFs, we screened 42 NF1 patients from 41 families with PNFs for mutations in the NF1 gene. In 33 out of the 41 (80%) unrelated patients NF1 mutations were found, 24 are novel while the other 9 have been described in previous studies. The 33 mutations included 23 nonsense and frameshift, six splice and four missense mutations. The tumors in these patients had various sizes and features/growth characteristics. No correlation was found between the type or location of the NF1 mutations and size, location or feature of the PNFs, suggesting that many types of NF1 mutations can lead to development of PNFs. 相似文献
4.
Molecular study of frequency of mosaicism in neurofibromatosis 2 patients with bilateral vestibular schwannomas 总被引:5,自引:1,他引:5
下载免费PDF全文
![点击此处可从《Journal of medical genetics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Kluwe L Mautner V Heinrich B Dezube R Jacoby LB Friedrich RE MacCollin M 《Journal of medical genetics》2003,40(2):109-114
Neurofibromatosis 2 (NF2) is a severe autosomal dominant disorder that predisposes to multiple tumours of the nervous system. About half of all patients are founders with clinically unaffected parents. The purpose of the present study was to examine the extent to which mosaicism is present in NF2 founders. A total of 233 NF2 founders with bilateral vestibular schwannomas (BVS) were screened by exon scanning. NF2 mutations were detected in the blood samples of 122 patients (52%). In 10 of the 122 cases, the ratio of mutant to normal alleles was obviously less than 1, suggesting mosaicism. Tumour specimens were available from 35 of the 111 subjects in whom no mutation could be detected in blood specimens. Mutational analysis by exon scanning detected typical NF2 mutations in 21 of the 35 tumours. In nine subjects, the alterations found in tumours could be confirmed to be the constitutional mutation based on finding of identical mutations in pathologically and/or anatomically distinct second tumours. In six other subjects with only a single tumour available, allelic loss of the NF2 gene was found in addition to the mutation in each tumour, suggesting that either the mutation or the deletion of the NF2 gene is probably the constitutional genetic alteration. Our results suggest that failure to find constitutional mutations in blood specimen from these 15 patients was not because of the limitation of the applied screening technique, but the lack of the mutations in their leucocytes, best explained by mosaicism. Extrapolating the rate (15/35 = 43%) of mosaicism in these 35 cases to the 111 NF2 founders with no constitutional NF2 mutations found in their blood, we inferred 48 mosaic subjects (111 x 0.429). Adding the 10 mosaic cases detected directly in blood specimens, we estimate the rate of mosaicism to be 24.8% (58/233) in our cohort of 233 NF2 founders with bilateral vestibular schwannomas. 相似文献
5.
Recombination in adenovirus: crossover sites in intertypic recombinants are located in regions of homology 总被引:6,自引:0,他引:6
Wild-type recombinants have been selected from intertypic genetic crosses between Ad2 and Ad5 ts mutants, with lesions within or close to the hexon gene, and the structure of the recombinant genomes has been examined by restriction endonuclease analysis. The recombinants with a crossing over within or in the vicinity of the hexon gene were subjected to a more detailed analysis, using restriction enzyme maps of the HindIII A fragment (map coordinates, 50.1–72.8) constructed for endonucleases that cut the DNA many times, viz. HaeII, HindII, and TaqI. These analyses indicated that crossover sites are confined to regions of relatively high DNA homology. More detailed mapping within the hexon region of Ad2 and Ad5, using a large battery of enzymes, confirmed this and allowed subdivision into three zones on the basis of the distribution of restriction endonuclease recognition sites; at the left-hand amino terminus there is almost complete homology between Ad2 and Ad5, the right-hand half of the gene displays partial homology as judged by the even distribution of common and unique sites, while a central segment of the hexon gene has no common restriction sites. This segment, defined by unique sites, coincides with the region of the Ad2 hexon polypeptide implicated in the trypsin sensitivity of the native hexon, and probably also determines the type-specific antigenicity and electrophoretic mobility of the hexon. 相似文献
6.
Recombination in adenovirus: DNA sequence analysis of crossover sites in intertypic recombinants 总被引:1,自引:0,他引:1
The nucleotide sequence of the adenovirus type 5 genome has been determined for a 620-bp region that spans the C terminus of the pVI gene and the N terminus of the hexon gene, and compared to the adenovirus type 2 DNA sequence: 25 base changes have been identified, most of which do not lead to alterations in the amino acid sequence and regulatory signals in the region. Crossover sites in three intertypic recombinants have been previously located in this region of the genome by fine restriction mapping. A sequence determination for the three recombinants, and the four ts mutants used in generating the ts+ recombinants, was carried out. The crossovers were in each case located in a small region of complete sequence homology (from 45 to 156 nucleotides long) flanked on either side by sequences derived from each parent. These structures are compatible with a reciprocal crossing over model of generalised recombination, where a recombinant joint has resolved in a region of high DNA homology. For the recombinants considered here, this region abutts onto a neighbouring region of much lower sequence homology, and it is possible that the position of the crossover is determined at least in part by the termination of branch migration at a heterologous boundary. 相似文献
7.
Despite technical improvements, the mapping of MHC class II epitopes within complex antigens by genetic or biochemical methods is still laborious and expensive. Here, we describe a simple and fast procedure to directly map T helper cell epitopes within known antigens by bacterial expression cloning. Short antigenic fragments, created by digestion of the coding sequence of the antigen with frequently cutting restriction enzymes, are randomly ligated to the coding sequence of GFP in a bacterial expression vector. Bacteria expressing antigen-GFP fusion proteins are then fed directly to MHC II+ antigen-presenting cells and probed with antigen-specific T cells. Bacterial colonies recognized by T cells are expanded, and the antigenic fragments identified by plasmid extraction and sequence analysis. This direct epitope identification (DEPI) approach offers several advantages. First, bacterial colonies expressing the antigen in frame with GFP are easily detectable by virtue of their green appearance and thereby reduce the screening effort significantly. Second, short antigenic peptides normally unstable in bacteria are highly expressed when fused to GFP. Third, the uniformly high level of expression of short antigenic peptides fused to GFP permits the identification of epitopes even within proteins which are difficult to express in bacteria. Furthermore, by fusing double-stranded oligonucleotides to the GFP gene, crucial amino acids within T cell epitopes may be defined. Thus, this method not only facilitates the identification of T cell epitopes, but also makes it possible to assess the role of individual amino acids for MHC binding or T cell recognition. 相似文献
8.
Circulating growth factor levels are associated with tumorigenesis in neurofibromatosis type 1. 总被引:2,自引:0,他引:2
George A Mashour Pablo Hernáiz Driever Melanie Hartmann Stephanie N Drissel Tingguo Zhang Bianca Scharf Ursula Felderhoff-Müser Sadatoshi Sakuma Reinhard E Friedrich Robert L Martuza Victor Felix Mautner Andreas Kurtz 《Clinical cancer research》2004,10(17):5677-5683
PURPOSE: Neurofibromatosis type 1 (NF1) is characterized by systemic development of neurofibromas. Early clinical diagnosis can be ambiguous, and genetic diagnosis can be prohibitively difficult. Dysregulation of a number of growth factors has been suggested to be a mechanism of pathogenesis. This study was performed to assess the contribution of circulating growth factors for diffuse tumorigenesis and the diagnostic value of circulating growth factor identification in serum. EXPERIMENTAL DESIGN: The growth stimulation of neurofibroma-derived cells by serum from NF1 patients was tested, and serum growth factor levels in a cohort of NF1 patients (n = 39) between the ages of 7 and 70 years were analyzed. RESULTS: Concentrations of midkine (MK) and stem cell factor, but not epidermal growth factor, were substantially increased in serum of NF1 patients when compared with healthy controls. Within the NF1 group, MK levels increased dramatically at puberty from an average of 0.79 ng/mL in patients <18 years to 1.18 ng/mL in patients >18 years old. Stem cell factor and MK concentrations above a defined threshold in serum of NF1 patients are of diagnostic benefit for 96% of patients in the cohort tested. Furthermore, serum from NF1 patients enhanced proliferation of human neurofibroma-derived primary Schwann cells and endothelial cells substantially better than normal serum. CONCLUSIONS: Enhanced circulating growth factor levels contribute to diffuse tumorigenesis in NF1 and may provide the basis for molecular diagnosis. 相似文献
9.
An assessment of a non-invasive technique for measurement of stroke distance was made using a portable Doppler ultrasound machine. The aim was to determine the measurement error of repeated stroke distance measurements (Within-observer variability) and to assess measurement agreement between two operators (between-observer variability). The measurement error (within-observer variability) for both operators was similar at approximately 2 cm. However, the measurements of the two operators (between-observer variability) did not agree well. Using the mean (SD) of three readings by each operator, the mean difference between the operators was -0.21 cm (1.96) giving a 95% confidence interval for the differences of -4.0 to +3.6 cm. There were significant positive and negative correlations between stroke distance and a variety of variables (age, height, weight, heart rate), but the relations were weak. The results indicate that the Doppler ultrasound technique for measurement of stroke distance would best be used to study trend changes in an individual patient, or subject, by a single operator. 相似文献
10.