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   1748篇
  免费   129篇
  国内免费   13篇
耳鼻咽喉   17篇
儿科学   150篇
妇产科学   44篇
基础医学   189篇
口腔科学   21篇
临床医学   155篇
内科学   279篇
皮肤病学   14篇
神经病学   150篇
特种医学   70篇
外科学   375篇
综合类   9篇
预防医学   122篇
眼科学   56篇
药学   123篇
中国医学   1篇
肿瘤学   115篇
  2022年   9篇
  2021年   25篇
  2020年   24篇
  2019年   39篇
  2018年   49篇
  2017年   29篇
  2016年   42篇
  2015年   49篇
  2014年   49篇
  2013年   74篇
  2012年   85篇
  2011年   74篇
  2010年   47篇
  2009年   50篇
  2008年   100篇
  2007年   101篇
  2006年   109篇
  2005年   113篇
  2004年   101篇
  2003年   111篇
  2002年   85篇
  2001年   24篇
  2000年   17篇
  1999年   26篇
  1998年   25篇
  1997年   20篇
  1996年   21篇
  1995年   17篇
  1994年   21篇
  1993年   13篇
  1992年   15篇
  1991年   19篇
  1990年   15篇
  1989年   8篇
  1988年   10篇
  1987年   10篇
  1986年   9篇
  1985年   23篇
  1984年   14篇
  1983年   18篇
  1982年   18篇
  1981年   15篇
  1980年   9篇
  1979年   15篇
  1978年   10篇
  1977年   12篇
  1976年   10篇
  1974年   8篇
  1972年   8篇
  1968年   8篇
排序方式: 共有1890条查询结果,搜索用时 209 毫秒
41.
Purpose: We present a genetic and clinical analysis of two sisters, 3 and 4 years of age, with nanophthalmos and macular folds. Methods: Ophthalmological examination, general paediatric examination and molecular genetic analysis of the MFRP gene were performed in both affected siblings. Results: Clinical analysis showed high hyperopia (+11 D and +12 D), short axial lengths (15 mm) and the presence of macular folds and optic nerve head drusen. Autofluorescence of the retina was generally normal with subtle macular abnormalities. Sequence analysis showed compound heterozygosity for severe MFRP mutations in both sisters: a previously reported p.Asn167fs (c.498dupC) and a novel stop codon mutation p.Gln91X (c.271C>T). Conclusion: These are the youngest nanophthalmos patients in the literature identified with severe loss of MFRP function, showing already the known structural abnormalities for this disease. Adult patients affected by homozygous or compound heterozygous MFRP mutations generally show signs of retinal dystrophy, with ERG disturbances and RPE abnormalities on autofluorescence imaging. ERG examination could not be performed in these children, but extensive RPE abnormalities were not seen at this young age.  相似文献   
42.
The human host defense peptide, LL‐37, is an important player in the first line of defense against invading microorganisms. LL‐37 and its precursor, hCAP18, have been detected in unstimulated whole saliva but no reports showing hCAP18/LL‐37 in isolated, parotid, and/or submandibular/sublingual saliva have been presented. Here, we measured the levels of hCAP18/LL‐37 in human parotid and submandibular/sublingual saliva and investigated the expression of hCAP18/LL‐37 in parotid and submandibular gland tissue. Parotid and submandibular/sublingual saliva was collected from healthy volunteers, and the levels of hCAP18/LL‐37 in saliva were analyzed by dot blot, ELISA, and western blotting. Cellular expression of hCAP18/LL‐37 in human parotid and submandibular glands was investigated by immunohistochemistry. Immunoreactivity for hCAP18/LL‐37 was detected in both parotid and submandibular/sublingual saliva of all individuals. The concentration of hCAP18/LL‐37 was similar in parotid and submandibular/sublingual saliva, and was determined by densitometric scanning of each dot and normalization to the total protein concentration of each sample, and by ELISA. Double immunohistochemistry revealed that intravascular neutrophils of both parotid and submandibular glands express hCAP18/LL‐37. For the first time, we demonstrate hCAP18/LL‐37 in isolated human parotid and submandibular/sublingual saliva and expression of hCAP18/LL‐37 in glandular intravascular neutrophils, indicating that neutrophils of the major salivary glands contribute to the LL‐37 content of whole saliva.  相似文献   
43.
5-Lipoxygenase (5-LO) is a tightly regulated enzyme in the synthesis of bioactive lipids from arachidonic acid. Here, we demonstrate that 5-LO is regulated by caspases, which are signaling molecules that control critical biological processes by means of specific limited proteolysis. Cell splitting of the Epstein-Barr virus-transformed B lymphocytic cell line BL41-E95-A caused a pronounced, but transient, reduction of functional 5-LO protein, accompanied by the appearance of a 62-kDa 5-LO cleavage product. In parallel, splitting of BL41-E95-A cells induced activation of caspase-6 (casp-6) and casp-8. Caspase activation and 5-LO degradation were blocked by the protein-synthesis inhibitor cycloheximide, and cell-permeable peptide inhibitors of casp-6 and casp-8 prevented 5-LO cleavage. Activation of casp-6 and casp-8 was connected to subsequent enhancement of cell proliferation, whereas selective caspase inhibition blocked cell growth. Last, isolated human 5-LO was cleaved by recombinant casp-6 in vitro to a 58-kDa fragment. Based on site-directed mutagenesis studies, 5-LO is cleaved by casp-6 after Asp-170, which in a homology-based 3D model of 5-LO is located on the enzyme periphery. We suggest that splitting of BL41-E95-A cells induces de novo synthesis of a protein involved in the activation of casp-6, which cleaves 5-LO.  相似文献   
44.
45.
46.
47.
[11C]Carbon monoxide (11CO) is a versatile building block for the synthesis of Positron Emission Tomography (PET) radioligands. However, the difficulty of trapping 11CO in a small solvent volume has limited its utility. We here report an evaluation of a simple, fully automated high‐pressure synthesizer prototype for the use in 11C‐carbonylation reactions. [11C]Carbon monoxide was easily prepared by online reduction of [11C]carbon dioxide using either Mo(s) or Zn(s) as the reducing agent. The conversion yield of 11CO was >99% when zinc was used as the reducing agent, and the corresponding value for Mo was approximately 71%. When the Zn or Mo column was constantly kept under inert atmosphere, no significant decrease in reducing properties was observed for more than 100 11CO productions. However, in our hands, Mo reductant was much easier to service. A total of nine functional groups were successfully radiolabeled using the 11CO synthesizer prototype. All measured radiochemical yields exceeded 37%, and the 11CO trapping efficiency was generally above 90%, except for the Suzuki coupling where the trapping efficiency was 80%. This high‐pressure synthesizer using [11C]carbon monoxide as the labeling precursor is easy to operate allowing for 11C‐carbonylation reactions to be performed in a high yield and in a routinely fashion.  相似文献   
48.
AIDS and Behavior - Pre-Exposure Prophylaxis (PrEP) health campaigns invite women to talk with their provider, partner, and peers about PrEP, though they do not offer specific guidance about who...  相似文献   
49.
The aim of this study was to determine the secretion of secretory immunoglobulins and gliadin antibodies in the small bowel in celiac disease. Twenty-four patients were investigated by perfusion of a defined jejunal segment. Four of the patients studied had a serum IgA deficiency and had no measurable amounts of secretory IgA in the perfusion fluid. The other patients demonstrated a significant increase in the jejunal concentration of secretory IgA (median 28.5 mg/liter) compared with healthy controls (median 16 mg/liter,N=16) and of IgM, celiac (median 12.3 mg/liter) compared to healthy controls (median 6.8 mg/liter,N=16). Jejunal IgA gliadin antibodies were detected in all patients except those with an IgA deficiency. All patients had jejunal IgM gliadin antibodies, but none of the patients had measurable jejunal IgG gliadin antibodies. A positive correlation was detected between serum and jejunal IgA gliadin antibody levels in the celiac patients, (P<0.01). Calculation of the ratio between gliadin antibodies and total levels of IgA and IgM in serum and jejunal perfusate demonstrated that the jejunal synthesis of gliadin antibodies of IgA and IgM type is both more pronounced and persistent than the systemic humoral immune response to gliadin.This work was supported by grants from the Swedish Medical Research Council, the Swedish Life Insurance Companies' Trust for Medical Research, and Th.C. Berghs Foundation and Pharmacia AB, Sweden.  相似文献   
50.
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