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   4823篇
  免费   362篇
  国内免费   26篇
耳鼻咽喉   21篇
儿科学   84篇
妇产科学   135篇
基础医学   989篇
口腔科学   41篇
临床医学   420篇
内科学   1088篇
皮肤病学   51篇
神经病学   582篇
特种医学   114篇
外科学   503篇
综合类   15篇
一般理论   2篇
预防医学   297篇
眼科学   100篇
药学   381篇
中国医学   8篇
肿瘤学   380篇
  2024年   3篇
  2023年   62篇
  2022年   161篇
  2021年   220篇
  2020年   99篇
  2019年   142篇
  2018年   163篇
  2017年   97篇
  2016年   129篇
  2015年   158篇
  2014年   186篇
  2013年   227篇
  2012年   364篇
  2011年   422篇
  2010年   238篇
  2009年   219篇
  2008年   367篇
  2007年   362篇
  2006年   345篇
  2005年   288篇
  2004年   259篇
  2003年   247篇
  2002年   208篇
  2001年   30篇
  2000年   14篇
  1999年   28篇
  1998年   36篇
  1997年   33篇
  1996年   19篇
  1995年   19篇
  1994年   6篇
  1993年   10篇
  1992年   7篇
  1991年   6篇
  1990年   2篇
  1988年   2篇
  1987年   3篇
  1986年   3篇
  1984年   4篇
  1983年   3篇
  1982年   3篇
  1981年   3篇
  1980年   3篇
  1979年   1篇
  1978年   2篇
  1974年   3篇
  1972年   1篇
  1969年   1篇
  1968年   1篇
  1964年   1篇
排序方式: 共有5211条查询结果,搜索用时 31 毫秒
101.
This study aimed to identify genetic mechanisms underlying severe retinal degeneration in one large family from northern Sweden, members of which presented with early-onset autosomal recessive retinitis pigmentosa and juvenile macular dystrophy. The clinical records of affected family members were analysed retrospectively and ophthalmological and electrophysiological examinations were performed in selected cases. Mutation screening was initially performed with microarrays, interrogating known mutations in the genes associated with recessive retinitis pigmentosa, Leber congenital amaurosis and Stargardt disease. Searching for homozygous regions with putative causative disease genes was done by high-density SNP-array genotyping, followed by segregation analysis of the family members. Two distinct phenotypes of retinal dystrophy, Leber congenital amaurosis and Stargardt disease were present in the family. In the family, four patients with Leber congenital amaurosis were homozygous for a novel c.2557C>T (p.Q853X) mutation in the CRB1 gene, while of two cases with Stargardt disease, one was homozygous for c.5461-10T>C in the ABCA4 gene and another was carrier of the same mutation and a novel ABCA4 mutation c.4773+3A>G. Sequence analysis of the entire ABCA4 gene in patients with Stargardt disease revealed complex alleles with additional sequence variants, which were evaluated by bioinformatics tools. In conclusion, presence of different genetic mechanisms resulting in variable phenotype within the family is not rare and can challenge molecular geneticists, ophthalmologists and genetic counsellors.  相似文献   
102.
The influence of different substituents on the optical properties of poly(amide imide)s and polyimides is systematically investigated. All of the polymers exhibit good solubility and film‐forming ability, high thermal stability, and glass transition temperatures of 162–209 °C for poly(amide imide)s and of 209–274 °C for polyimides. The optical transmittance of the films at 450 nm is above 80% for all the studied polyimides and poly(amide imide)s containing benzonitrile units linked in the 2,6‐position. The values of refractive index for poly(amide imide)s are in the range of 1.623–1.748 and for polyimides in the domain of 1.672–1.768.

  相似文献   

103.
The review considers the up to date achievements in the role of membrane phosphoinositides and keys enzymes of the lipid branch of the phosphoinositide signal pathway (PI-pathway) in unicellular eukaryotes. Particular attention is paid to mechanisms of phospholipase C (PLC) activation and the PLC interaction both with cell surface receptors and with the effector cytoplasm targets. The role of protein kinase C (PKC) in intracellular signaling and the relationship of the PI-pathway key enzymes with protein tyrosine kinases (PTK)-signaling and cAMP-protein kinase A (PKA) pathway are discussed.  相似文献   
104.
Stage 4 neuroblastomas have a high rate of local and metastatic relapse and associated disease mortality. The central nervous system (CNS) is currently one of the most common isolated relapse sites, yet the genomic alterations that contribute to these metastases are unknown. This study sought to identify recurrent DNA copy number alterations (CNAs) and target genes relating to neuroblastoma CNS metastases by studying 19 pre‐CNS primary tumors and 27 CNS metastases, including 12 matched pairs. SNP microarray analyses revealed that MYCN amplified (MYCNA) tumors had recurrent CNAs different from non‐MYCNA cohorts. Several CNAs known to be prevalent among primary neuroblastomas occurred more frequently in CNS metastases, including 4p?, 7q+, 12q+, and 19q? in non‐MYCNA metastases, and 9p? and 14q? irrespective of MYCNA status. In addition, novel CNS metastases‐related CNAs included 18q22.1 gains in non‐MYCNA pre‐CNS primaries and 5p15.33 gains and 15q26.1→tel losses in non‐MYCNA CNS metastases. Based on minimal common regions, gene expression, and biological properties, TERT (5p), NR2F2 (15q), ALDH1A3 (15q), CDKN2A (9p), and possibly CDH7 and CDH19 (18q) were candidate genes associated with the CNS metastatic process. Notably, the 5p15 minimal common region contained only TERT, and non‐MYCNA CNS metastases with focal 5p15 gains had increased TERT expression, similar to MYCNA tumors. These findings suggest that a specific genomic lesion (18q22.1 gain) predisposes to CNS metastases and that distinct lesions are recurrently acquired during metastatic progression. Among the acquired lesions, increased TERT copy number and expression appears likely to function in lieu of MYCNA to promote CNS metastasis. © 2013 Wiley Periodicals, Inc.  相似文献   
105.
106.
107.
Oral and Maxillofacial Surgery - Presently, the functional reconstruction of the tongue in patients after subtotal or total glossectomy with the removal of the oral floor muscles and spearing of...  相似文献   
108.
The development of novel materials with improved functional characteristics for supercapacitor electrodes is of current concern and calls for elaboration of innovative approaches. We report on an eco-friendly enzymatic synthesis of a composite based on poly(3,4-ethylenedioxythiophene) (PEDOT) and multi-walled carbon nanotubes (MWCNTs). The redox active compound, sodium 1,2-naphthoquinone-4-sulfonate (NQS), was used as a dopant for the backbone of the polymer. Oxidative polymerization of 3,4-ethylenedioxythiophene (EDOT) was catalyzed by a high redox potential laccase from the fungus Trametes hirsuta. Atmospheric oxygen served as an oxidant. A uniform thin layer of NQS-doped PEDOT formed on the surface of MWCNTs as a result of the enzymatic polymerization. The PEDOT–NQS/MWCNT composite showed a high specific capacitance of ca. 575 F g−1 at a potential scan rate of 5 mV s−1 and an excellent cycling stability within a potential window between −0.5 and 1.0 V, which makes it a promising electrode material for high-performance supercapacitors.

The use of redox active NSQ as a dopant of PEDOT dramatically increases the specific capacitance and cyclic stability of enzymatically synthesized PEDOT–NSQ/MWCNT composite.  相似文献   
109.
110.
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