全文获取类型
收费全文 | 11097篇 |
免费 | 900篇 |
国内免费 | 258篇 |
专业分类
耳鼻咽喉 | 54篇 |
儿科学 | 173篇 |
妇产科学 | 1237篇 |
基础医学 | 1574篇 |
口腔科学 | 167篇 |
临床医学 | 826篇 |
内科学 | 923篇 |
皮肤病学 | 140篇 |
神经病学 | 702篇 |
特种医学 | 183篇 |
外科学 | 1083篇 |
综合类 | 1433篇 |
现状与发展 | 1篇 |
一般理论 | 26篇 |
预防医学 | 1819篇 |
眼科学 | 77篇 |
药学 | 874篇 |
13篇 | |
中国医学 | 380篇 |
肿瘤学 | 570篇 |
出版年
2024年 | 23篇 |
2023年 | 207篇 |
2022年 | 278篇 |
2021年 | 477篇 |
2020年 | 489篇 |
2019年 | 512篇 |
2018年 | 518篇 |
2017年 | 450篇 |
2016年 | 444篇 |
2015年 | 430篇 |
2014年 | 750篇 |
2013年 | 876篇 |
2012年 | 666篇 |
2011年 | 704篇 |
2010年 | 624篇 |
2009年 | 532篇 |
2008年 | 479篇 |
2007年 | 503篇 |
2006年 | 460篇 |
2005年 | 353篇 |
2004年 | 400篇 |
2003年 | 319篇 |
2002年 | 240篇 |
2001年 | 199篇 |
2000年 | 176篇 |
1999年 | 159篇 |
1998年 | 118篇 |
1997年 | 110篇 |
1996年 | 93篇 |
1995年 | 80篇 |
1994年 | 53篇 |
1993年 | 50篇 |
1992年 | 53篇 |
1991年 | 49篇 |
1990年 | 38篇 |
1989年 | 32篇 |
1988年 | 32篇 |
1987年 | 20篇 |
1986年 | 19篇 |
1985年 | 34篇 |
1984年 | 42篇 |
1983年 | 24篇 |
1982年 | 19篇 |
1981年 | 26篇 |
1980年 | 17篇 |
1979年 | 22篇 |
1978年 | 11篇 |
1977年 | 15篇 |
1976年 | 8篇 |
1973年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Jan Schmeller Michael Wessolly Elena Mairinger Sabrina Borchert Thomas Hager Thomas Mairinger Kurt Werner Schmid Jeremias Wohlschlaeger Robert F.H. Walter Fabian D. Mairinger 《Pathology, research and practice》2019,215(2):381-386
Introduction
The usage of formalin-fixed paraffin embedded (FFPE) tissue is characterized by its long shelf-life and simple handling. Therefore it is the most commonly available tissue specimen in routine diagnostics and histological studies. Formaldehyde fixation may result in RNA degradation and cross linking with proteins, while storage conditions also affect RNA integrity. The present study was designed to investigate the influence of these factors on RNA analysis.Design
FFPE-derived RNA from sections of 23 patients with spontaneous pneumothoraxes was used. Unstained sections of FFPE tissue were stored at various temperatures (?80?°C, ?20?°C, 4?°C, 24?°C) prior to RNA extraction. The potential impact on RNA quality of semi-automatic and manual RNA isolation and three different deparaffinization agents (mineral oil, xylene and d-limonene) were compared.Results
The storage temperature of FFPE sections affects RNA concentration and fragmentation, with the optimal storage temperature below -20?°C. The RNA extracted with d-limonene shows equivalent quality to the RNA extracted using more toxic standard agents. The manual isolation provides a higher RNA yield compared to the semi-automatic isolation. However, no differences in the amount of longer RNA fragments were observed. Furthermore, the semi-automatic isolation showed an enhanced RNA quality.Conclusion
FFPE sections not directly used for RNA extraction should be stored below -20?°C to increase quality and yield of the RNA. Usage of semi-automatic isolation produces superior results and simplifies routine processes by having less hands-on-time. Replacement of toxic xylene by d-limonene may contribute to improved occupational safety while not influencing analytical results. 相似文献92.
Studies from the last decade on factors influencing reproductive planning after genetic counselling were reviewed. Increased possibilities of DNA-analysis and prenatal diagnosis might have brought about a shift in the paramountcy of factors influencing reproductive planning after genetic counselling. In contrast to the literature in the seventies, the magnitude of the genetic risk was no longer found to be one of the decisive factors in postcounselling reproductive planning. Instead, the interpretation of the risk as high or low and the desire to have children appeared to be paramount. The impact of new developments in DNA-analysis in prenatal diagnosis and presymptomatic testing will be an important subject for future studies on factors influencing reproductive planning. 相似文献
93.
The specification of a germ cell as sperm or oocyte and determination of cell number remain unsolved questions in developmental biology. This paper examines Caenorhabditis elegans FOG-1, a CPEB-related RNA-binding protein that controls the sperm fate. We find that abundant FOG-1 protein is observed transiently in germ cells just prior to their expression of an early sperm-differentiation marker. As the germline tissue elongates, abundant FOG-1 appears more and more distally as sperm become specified, but disappears when the germ line switches to oogenesis. This dynamic pattern is controlled by both globally acting and germline-specific sex-determining regulators. Importantly, the extent of FOG-1 expression corresponds roughly to sperm number in wild-type and mutants, altering sperm number. By contrast, three other key regulators of the sperm/oocyte decision do not similarly correspond to sperm number. We suggest that FOG-1 is precisely modulated in both time and space to specify sperm fate and control sperm number. 相似文献
94.
Jihai Xu Jing Wu Xiaofeng Teng Libing Cai Huizong Yuan Xiaokun Chen Mu Hu Xin Wang Ning Jiang Hong Chen 《American journal of medical genetics. Part A》2020,182(9):2117-2123
Polydactyly and syndactyly are digital abnormalities in limb‐associated birth defects usually caused by genetic disorders. In this study, a five‐generation Chinese pedigree was found with triphalangeal thumb polysyndactyly syndrome (TPTPS), showing an autosomal dominant pattern of inheritance. We utilized linkage analysis and whole genome sequencing (WGS) for the genetic diagnosis of this pedigree. Linkage analysis was performed using a genome‐wide single nucleotide polymorphism (SNP) chip and three genomic regions were identified in chromosomes 2, 6, and 7 with significant linkage signals. WGS discovered a copy number variation (CNV) mutation caused by a large duplication region at the tail of chromosome 7 located in exons 1–5 of the LMBR1 gene, including the zone of polarizing activity regulatory sequence (ZRS), with a length of approximately 180 kb. A real‐time polymerase chain reaction (PCR) assay confirmed the duplication. The findings of our study supported the notion that large duplications including the ZRS caused TPTPS. Our study showed that linkage analysis in combination with WGS could successfully identify the disease locus and causative mutation in TPTPS, which could help elucidate the molecular mechanisms and genotype–phenotype correlations in polydactyly. 相似文献
95.
Insulin-like growth factor binding protein-1 (IGFBP-1): a multifunctional role in the human female reproductive tract 总被引:3,自引:0,他引:3
Insulin-like growth factor-1 (IGFBP-1) is particularly important in human female reproductive physiology, where it is involved with other factors in a complex system which regulates menstrual cycles, puberty, ovulation, decidualization, implantation and fetal growth. This has implications for clinical obstetrics and gynaecology, where there is evidence for a pathophysiological role for IGFBP-1 in pre-eclampsia, intrauterine growth restriction, polycystic ovarian syndrome and trophoblast and endometrial neoplasms. 相似文献
96.
Point mutation of the BRAF gene is a common genetic event in papillary thyroid carcinomas. More recently, it has been found that BRAF can also participate in chromosomal rearrangement. In this study, we explore yet another possible mechanism of BRAF alteration, which involves copy number gain. Using fluorescence in situ hybridization with BRAF specific and chromosome 7 centromeric probes, we studied 62 follicular thyroid tumors and 32 papillary carcinomas. We found
that numerical changes in BRAF copy number were rare in papillary thyroid carcinomas, while they occurred in 16–45% of follicular tumors of conventional
and oncocytic (Hürthle cell) types. They were due to amplification of the gene or gain of one or more copies of chromosome
7. Tetrasomy for chromosome 7 was overall the most common finding. The changes in BRAF copy number did not overlap with RAS mutations in follicular tumors. In a group of follicular carcinomas, tumors with BRAF copy number gain were significantly more often widely invasive (67%) compared to tumors with no copy number change (18%).
By Western blotting, the tumors carrying four copies of the gene revealed higher expression of BRAF protein, suggesting that
copy number gain may represent another mechanism of BRAF activation in thyroid tumors. 相似文献
97.
Nichols SM Bavister BD Brenner CA Didier PJ Harrison RM Kubisch HM 《Human reproduction (Oxford, England)》2005,20(1):79-83
BACKGROUND: A decline in fertility is evident in human females past their middle thirties. This 'reproductive senescence', marked by a sharp decline in pregnancy rates, may be attributed to reductions in numbers of available oocytes and their quality. Because Old World primates exhibit ovarian morphology and physiological control and timing of menstrual cycles closely resembling those of humans, the current study investigated the rhesus macaque as a potential model for human reproductive senescence. METHODS: Ovaries collected from females aged 1-25 years and divided into five age groups were analysed histologically. RESULTS: General ovarian morphology demonstrated significant changes as the females approached menopause. The proportions of primordial and primary follicles all demonstrated significant differences across age groups (primordial: 77.1, 79.9, 69.7, 62.9, 55.1%; primary: 21.5, 18.8, 28.5, 35.2, 43.1% for age groups 1 to 5 respectively; P<0.0001 for both). Samples from females approaching or undergoing the menopausal transition (aged 20-25 years) demonstrated evidence of ovarian senescence, having scattered and atretic follicles, low numbers of primordial follicles and reduced stromal tissue. CONCLUSION: This study supports the value of the rhesus monkey as a model for reproductive ageing because its ovary undergoes follicular reservoir depletion similar to that seen in humans. 相似文献
98.
99.
M. J. Kelly R. L. Moss C. A. Dudley C. P. Fawcett 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1977,30(1):43-52
Summary The purpose of this study was to determine the specificity of the response of medial preoptic-septal neurons (mPOA-S) to microelectrophoresed 17-estradiol hemisuccinate (17E2S). In vitro studies were conducted initially to determine the release of the labeled 17E2S from multibarrel glass micropipettes. Subsequently, an isomer of 17E2S, 17-estradiol hemisuccinate (17E2S), was synthesized and purified. Thirty-six mPOA-S neurons from normal cycling female rats were tested with both 17E2S and 17E2S. Twelve of these units responded with inhibition to 17E2S, while none responded to 17E2S. Furthermore, fifty extrahypothalamic (cortical, hippocampal, thalamic) neurons were tested with 17E2S. The majority (N = 45) showed no response, three showed excitation and two inhibition to the microelectrophoresed steroid ester. These findings suggest that a specific receptor mechanism is responsible for the changes in mPOA-S unit activity, and that these effects may be important in the regulation of reproductive events.Supported by NIH Grant NS10434-END, awarded to R.L. MossPresently an NIH Postdoctoral Fellow at Max-Planck Institute for Biophysical Chemistry, Göttingen, West GermanyRecipient of an USPHS Career Development Award No. HD00146 相似文献
100.
探讨以纤维蛋白胶(fibrin sealant,FS)为载体,复合rhBMP-2\bFGF的注射型骨修复材料,修复犬桡骨节段性缺损的作用,为其临床应用提供实验依据.实验分为:实验组(FS bFGF rhBMP-2)、对照组(FS).于12只成年健康家犬右侧桡骨中上段造成2cm缺损,制成犬桡骨2cm骨缺损实验模型,然后严密缝合皮下组织及皮肤,将实验材料经伤口周围正常皮肤注射到骨缺损处,术后4、8、16、24w进行放射学检查,术后24w,标本进行组织学和骨密度检查,研究其成骨效应.结果表明:实验组骨缺损区在成骨活跃程度、骨密度和再生髓腔结构等方面均显著优于对照组,使骨缺损得到了成功的修复(P<0.01).以纤维蛋白胶为载体复合rhBMP-2和bFGF的注射型骨修复材料,具有高效的骨修复能力,对犬的骨缺损有很好的修复效果. 相似文献