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   9233篇
  免费   674篇
  国内免费   79篇
耳鼻咽喉   69篇
儿科学   211篇
妇产科学   65篇
基础医学   1001篇
口腔科学   200篇
临床医学   631篇
内科学   2670篇
皮肤病学   467篇
神经病学   508篇
特种医学   414篇
外科学   1660篇
综合类   34篇
一般理论   1篇
预防医学   219篇
眼科学   103篇
药学   526篇
中国医学   9篇
肿瘤学   1198篇
  2024年   9篇
  2023年   147篇
  2022年   298篇
  2021年   468篇
  2020年   226篇
  2019年   303篇
  2018年   379篇
  2017年   344篇
  2016年   365篇
  2015年   342篇
  2014年   439篇
  2013年   454篇
  2012年   779篇
  2011年   791篇
  2010年   400篇
  2009年   339篇
  2008年   549篇
  2007年   608篇
  2006年   538篇
  2005年   508篇
  2004年   416篇
  2003年   336篇
  2002年   277篇
  2001年   60篇
  2000年   55篇
  1999年   72篇
  1998年   49篇
  1997年   41篇
  1996年   33篇
  1995年   25篇
  1994年   28篇
  1993年   28篇
  1992年   36篇
  1991年   27篇
  1990年   21篇
  1989年   17篇
  1988年   31篇
  1987年   16篇
  1986年   23篇
  1985年   34篇
  1984年   18篇
  1983年   7篇
  1982年   3篇
  1981年   7篇
  1980年   3篇
  1979年   10篇
  1977年   4篇
  1973年   5篇
  1972年   4篇
  1970年   3篇
排序方式: 共有9986条查询结果,搜索用时 31 毫秒
51.
52.
53.
Summary The immunofluorescent localization of glomerular basement membrane (GBM) antigens was examined in 52 specimens from normal kidneys and in various renal diseases using antisera to human GBM HGBM), IV type collagen (IV Col) and P3 antigen, a rat nephritogen. Anti-HGBM serum normally stained the GBM and the mesangium in a restrictive pattern, anti-IV Col serum stained the GBM and the mesangium in a wider pattern and anti-P3 serum stained only the GBM. In mesangial proliferative glomerulonephritis, including IgA nephropathy pathy and Henoch-Schönlein nephritis, the widened mesangial areas were stained with anti-HGBM and anti-IV Col sera. In membranous nephropathy, the punched-out lesions of thickened GBM were demonstrated with the three antisera in moderate cases and a double linear distribution with fine granulation with anti-HGBM and anti-IV Col sera were revealed in one severe case. In membranoproliferative glomerulonephritis, the expanded mesangium and thickened capillary walls were stained with anti-HGBM and anti-IV Col sera, while the outer line of glomerular capillary walls was only positive with anti-P3 serum. In crescentic glomerulonephritis, the collapsed glomerular tufts were stained normally with anti-HGBM and anti-P3 sera and weakly with anti-IV Col serum. In diabetic nephropathy, anti-HGBM serum stained the GBM in a double linear distribution without reacting with the expanded mesangium; anti-IV Col serum stained the mesangium and the GBM in a less clear double linear fashion while anti-P3 serum stained the GBM as single line. Thin membrane disease and Alport's syndrome had normal reactivity with all antisera. However, in one case of Alport's syndrome anti-HGBM and anti-P3 sera stained the GBM in a focal and segmental pattern, while normal staining with anti-IV Col serum was found. In lesions with adhesions and crescents the staining was positive for HGBM and IV Col and negative for P3; obsolescent glomeruli were stained with anti-HGBM and anti-P3 sera, and had diminished staining with anti-IV Col serum.The identification of the various structural glomerular antigens is useful in the classification of certain types of glomerular diseases. Further insight into the mechanisms underlying these conditions may be obtained in this way.  相似文献   
54.
LIS1 is mutated in the human neuronal migration defect lissencephaly and along with NDEL1 (formerly NUDEL) participates in the regulation of cytoplasmic dynein function during neuronal development. Targeted disruption of Ndel1 suggested that NDEL1 could have other molecular targets that regulate microtubule organization for proper neuronal migration. To further understanding the molecular mechanism of LIS1 and lissencephaly, we identified the katanin p60 microtubule-severing protein as an additional molecular target of NDEL1. We demonstrate that phosphorylation of NDEL1 by Cdk5 facilitates interaction between NDEL1 and p60, suggesting that P-NDEL1 regulates the distribution of katanin p60. Abnormal accumulation of p60 in nucleus of Ndel1 null mutants supports an essential role of NDEL1 in p60 regulation. Complete loss of NDEL1 or expression of dominant negative mutants of p60 in migrating neurons results in defective migration and elongation of nuclear-centrosomal distance. Our results suggest that NDEL1 is essential for mitotic cell division and neuronal migration not only via regulation of cytoplasmic dynein function but also by modulation of katanin p60 localization and function.  相似文献   
55.
To develop new biomaterials for making medical devices, polymer alloys composed of a phospholipid polymer, poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), and polyethylene (PE) were prepared. The PE/PMPC alloy membrane could be obtained by a combination of solution mixing and solvent evaporation methods using xylene and n-butanol mixture as a solvent. Moreover, thermal treatment was applied to improve the mechanical properties of the PE/PMPC alloy membrane. In the PE/PMPC alloy membrane, the PMPC domains were located not only inside the membrane but also at the surface. Surface analysis of the PE/PMPC alloy membrane with X-ray photoelectron spectroscopy, wettability evaluation, and dynamic contact angle measurements revealed that the phospholipid polar groups in the PMPC covered the surface even after thermal treatment. Blood compatibility tests with attention to platelet adhesion and change in morphology of adhered platelets showed that the PE/PMPC alloy membrane had excellent platelet adhesion resistance. We finally concluded that the PE/PMPC alloy could be used as biomaterials instead of poly(vinyl chloride)-based materials.  相似文献   
56.
57.
Rab proteins play a critical role in intracellular vesicle trafficking and require post‐translational modification by adding lipids at the C‐terminus for proper functions. This modification is preceded by the formation of a trimeric protein complex with the Rab escort protein (REP) and the Rab geranylgeranyltransferase (RabGGTase). However, the genetic hierarchy among these proteins and the tissue‐specificity of each protein function are not yet clearly understood. Here we identified the Caenorhabditis elegans rep‐1 gene and found that a rep‐1 mutant showed a mild defect in synaptic transmission and defecation behaviors. Genetic analyses using the exocytic Rab mutants rab‐3 or rab‐27 suggested that rep‐1 functions only in the RAB‐27 pathway, and not in the RAB‐3 pathway, for synaptic transmission at neuromuscular junctions. However, the disruption of REP‐1 did not cause defecation defects compared to severe defects in either RAB‐27 or RabGGTase disruption, suggesting that REP‐1 is not essential for RAB‐27 signaling in defection. Some Rab proteins did not physically interact with REP‐1, and localization of these Rab proteins was not severely affected by REP‐1 disruption. These findings suggest that REP‐1 functions are required in specific Rab pathways and in specific tissues, and that some Rab proteins are functionally prenylated without REP‐1.  相似文献   
58.
Cigarette smoke condensate (CSC) was separated into severalfractions and each was tested for an inhibitory effect on theearly antigen (EA) of Epstein-Barr virus (EBV) which can beinduced by 12-0-tetradecanoylphorbol-13-acetate (TPA) in Rajicells. Two diastereoisomers of 2,7,11-cembratriene-4,6-diol(- and ß-CBT) were isolated from the neutral fractionsof CSC and these showed potent inhibitory effects on the inductionof EBV-EA by TPA. The doses of - and ß-CBT requiredfor 50% inhibition of EBV-EA induction by TPA were 7.7 and 6.7µg/ml, respectively, which are comparable with those ofretinoic acid, a potent inhibitor of induction of epideral ornithinedecarboxylase (ODC) activity and tumor promotion by TPA in mice.Application of - and ß-CBT to mouse skin prior totreatment with TPA inhibited TPA-induced ODC activity. The degreeof inhibition was dependent on the dose and application of 16.5µmol/mouse of - and ß-CBT resulted in a 50 and40% reduction, respectively, of the maximum of the ODC activityinduced as a result of treatment with TPA. In initiation-promotionexperiments, -CBT markedly inhibited the promoting effect ofTPA on skin tumor formation in mice which were initiated with7,12-dimethylbenz[a]anthracene, but ß-CBT was foundto be less effective. Application of 3.3 µmol of -CBT40 min prior to treatment with TPA (1 µg) resulted ina 53% reduction in the number of papillomas per mouse. Our presentdata suggest that EBV-EA inhibition assay using Raji cells iseffective for the first screening of inhibitors of tumor promotion,and provide evidence that CSC contains antitumor-promoting agentsin addition to carcinogenic and tumor-promoting agents alreadyreported.  相似文献   
59.
A new operative method named as "Extraperiosteal air plombage" against chronic empyema were performed to 80 patients and its cure rate by the first operation was 93.8% which is a good and high rate. Know-how to perform the operation without failure is (1) to complete the excoriation of the pleural debris, (2) to seal completely the leakage such as bronchiolar fistula, (3) to perform the extraperiosteal abbration rather over much to attach the lung to the muscle layer, (4) to close the chest wall completely, and (5) to wash out thoroughly the extraperiosteal cavity with brush and enough saline solution and to use the effective antibiotica.  相似文献   
60.
Malnutrition negatively affects the quality of life of patients with dysphagia. Despite the need for nutritional status assessment in patients with dysphagia, standard, effective nutritional assessments are not yet available, and the identification of optimal nutritional assessment items for patients with dysphagia is inadequate. We conducted a scoping review of the use of nutritional assessment items in adult patients with oropharyngeal and esophageal dysphagia. The MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials databases were searched to identify articles published in English within the last 30 years. Twenty-two studies met the inclusion criteria. Seven nutritional assessment categories were identified: body mass index (BMI), nutritional screening tool, anthropometric measurements, body composition, dietary assessment, blood biomarkers, and other. BMI and albumin were more commonly assessed in adults. The Global Leadership Initiative on Malnutrition (GLIM), defining new diagnostic criteria for malnutrition, includes the categories of BMI, nutritional screening tool, anthropometric measurements, body composition, and dietary assessment as its required components, but not the blood biomarkers and the “other” categories. We recommend assessing nutritional status, including GLIM criteria, in adult patients with dysphagia. This would standardize nutritional assessments in patients with dysphagia and allow future global comparisons of the prevalence and outcomes of malnutrition, as well as of appropriate interventions.  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