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   2640篇
  免费   184篇
  国内免费   115篇
耳鼻咽喉   12篇
儿科学   105篇
妇产科学   31篇
基础医学   282篇
口腔科学   35篇
临床医学   324篇
内科学   610篇
皮肤病学   120篇
神经病学   99篇
特种医学   416篇
外国民族医学   1篇
外科学   243篇
综合类   60篇
一般理论   1篇
预防医学   273篇
眼科学   20篇
药学   153篇
中国医学   1篇
肿瘤学   153篇
  2023年   8篇
  2022年   17篇
  2021年   24篇
  2020年   23篇
  2019年   34篇
  2018年   44篇
  2017年   16篇
  2016年   43篇
  2015年   44篇
  2014年   46篇
  2013年   86篇
  2012年   75篇
  2011年   100篇
  2010年   83篇
  2009年   75篇
  2008年   98篇
  2007年   137篇
  2006年   106篇
  2005年   118篇
  2004年   87篇
  2003年   71篇
  2002年   59篇
  2001年   61篇
  2000年   65篇
  1999年   64篇
  1998年   109篇
  1997年   105篇
  1996年   115篇
  1995年   81篇
  1994年   79篇
  1993年   74篇
  1992年   37篇
  1991年   62篇
  1990年   55篇
  1989年   72篇
  1988年   66篇
  1987年   73篇
  1986年   43篇
  1985年   72篇
  1984年   29篇
  1983年   18篇
  1982年   30篇
  1981年   25篇
  1980年   36篇
  1979年   18篇
  1978年   22篇
  1977年   21篇
  1976年   35篇
  1975年   23篇
  1968年   9篇
排序方式: 共有2939条查询结果,搜索用时 15 毫秒
61.
Benign cutaneous vascular tumors of infancy: when to worry, what to do   总被引:2,自引:0,他引:2  
OBJECTIVES: To discuss the current knowledge regarding complicated hemangiomas (cervicofacial, periorbital, lumbosacral, and parotid), including the associated syndromes of diffuse neonatal hemangiomatosis and PHACES (posterior fossa malformations, most commonly of the Dandy-Walker variant; hemangiomas [especially large, plaquelike, facial lesions]; arterial anomalies; cardiac anomalies and coarctation of the aorta; eye abnormalities; and sternal cleft and/or supraumbilical raphe). To discuss 2 newly recognized entities that may be a source of diagnostic confusion with the common hemangioma, the kaposiform hemangioendothelioma and tufted angioma. To discuss the risks and benefits of current treatment options, including the use of systemic corticosteroids and interferon in necessary situations. DATA SOURCES: The pertinent world literature was reviewed and incorporated into experience from our pediatric dermatology practice at the University of Texas Medical School at Houston. CONCLUSIONS: The common hemangioma, kaposiform hemangioendothelioma, and tufted angioma, though benign histologically, may cause serious consequences for children. Dermatologists should be able to recognize unique clinical presentations of these lesions and obtain further diagnostic evaluation accordingly. Dermatologists should also be aware of available treatment options, including the use of systemic chemotherapy in life-threatening situations.  相似文献   
62.
63.
64.
65.
AMP-18,一种新发现的胃黏膜保护因子   总被引:3,自引:0,他引:3  
AMP-18是一种新发现的由胃腺体上皮细胞合成的小分子蛋白质,独特表达于胃黏膜,机体其他部位少见,胃癌组织中表达缺失.AMP-18 由185个氨基酸组成,除去N端信号肽(20个氨基酸)后大小约18 ku,第54-150个氨基酸组成高度保守的结构域(BRICHOS区域)承担主要的生理功能.AMP-18由胃腺体上皮细胞以胞吐的方式分泌到胃黏液中,他的合成和分泌与个体生长发育有关,并受福斯高林、吲哚美辛、地塞米松等药物的影响.目前发现 AMP-18的生理功能主要有促进胃黏膜上皮细胞的有丝分裂,促进细胞的迁徙,促胃肠黏膜损伤的修复,保持胃肠黏膜的完整等.  相似文献   
66.
While constructing a cDNA library of human embryos, we have isolated a clone homologous to jumonji, a mouse gene required for neural tube formation. We have determined the complete coding sequence of the human homologue (JMJ) and deduced the amino acid sequence of the putative protein. We show here that human and mouse jumonji putative proteins are homologous and present 90% identity. During human embryogenesis, JMJ mRNAs are predominantly expressed in neurons and particularly in dorsal root ganglion cells. They are also expressed in neurons of human adult cerebral cortex. In view of these observations, we propose JMJ as a candidate gene for developmental defects of the central nervous system in the human. The human JMJ gene maps at position 6p24-6p23.   相似文献   
67.
Expansion of trinucleotide CAG repeats coding for polyglutamine has been implicated in five neurodegenerative disorders, including spinocerebellar ataxia (SCA) 1 and SCA3 or Machado-Joseph disease (SCA3/MJD), two forms of type I autosomal dominant cerebellar ataxias (ADCA). Using the 1C2 antibody which specifically recognizes large polyglutamine tracts, particularly those that are expanded, we recently reported the detection of proteins with pathological glutamine expansions in lymphoblasts from another form of ADCA type I, SCA2, as well as from patients presenting with the distinct phenotype of ADCA type II. We now have screened a large series of patients with ADCA or isolated cases with cerebellar ataxia, for the presence of proteins with polyglutamine expansions. A 150 kDa SCA2 protein was detected in 16 out of 40 families with ADCA type I. This corresponds to 24% of all ADCA type I families, which is much more frequent than SCA1 in this series of patients (13%). The signal intensity of the SCA2 protein was negatively correlated to age at onset, as expected for an expanded and unstable trinucleotide repeat mutation. The disease segregated with markers closely linked to the SCA2 locus in all identified SCA2 families. In addition, a specific 130 kDa protein, which segregated with the disease, was detected in lymphoblasts of patients from nine families with ADCA type II. It was also visualized in the cerebral cortex of one of the patients, demonstrating its translation in the nervous system. Finally, no new disease-related proteins containing expanded polyglutamine tracts could be detected in lymphoblasts from the remaining patients with ADCA or isolated cases with cerebellar ataxia.   相似文献   
68.
Toxicological testing of compounds often is conducted at the maximum tolerated dose to identify potential target organs. Toxicities observed at these high doses may result in decreased body weight gain, food consumption and activity. These clinical signs are often associated with a generalized stress response. It has been known that stress may cause increased levels of corticosterone, which causes changes in circulating leukocyte profiles, decreases in thymus and spleen weights and changes in the microscopic structure of lymphoid organs. This makes it difficult to differentiate between stress-related changes and direct toxicity to the immune system in standard non-clinical toxicity testing in rats. In mice, MHC Class II expression was found to be a very sensitive biomarker of stress and maybe useful for the rat. Therefore, the objective of studies presented was to further characterize the effects of corticosterone and stressors on the immune system and identify potential biomarkers of stress in rats. Rats were treated with exogenous corticosterone (20 or 30 mg/kg BID) or ethanol (5 g/kg) for either 1 or 4 days. Restraint stress was also evaluated for a 3-day period. Blood and urine samples were collected during the treatment period for corticosterone measurements. At necropsy, blood samples for leukocyte differentials were collected. Spleen and thymus weights, cellularity, lymphocyte subpopulations and histopathology were also evaluated. Urine corticosterone levels were also investigated as a surrogate to measuring serum corticosterone. The results demonstrate that the pattern of responses to corticosterone or the stressors is different in mice and rats. Although, decreases in MHC Class II were found to be a sensitive indicator of stress in mice, only slight decreases were observed in rats with similar serum corticosterone AUC levels. Decreases in thymus weight were greater than spleen weight with corticosterone or ethanol or restraint stressor. No other single parameter or combination of parameters tested were obvious candidates as sensitive biomarkers of stress in rats. However, the good correlation between urine and serum corticosterone levels suggest that urine corticosterone may be a potential biomarker of stress induced changes to the immune response.  相似文献   
69.
Alzheimer's disease (AD) is the most common form of dementia, and is characterized by the degeneration of neurons and their synapses, and a higher number of amyloid plaques and neurofibrillary tangles (NFTs) compared with that found in non-demented individuals. Amyloid-β-peptides (Aβ) are major components of amyloid plaques in AD brain whereas NFTs are composed of Tau and associated with ubiquitin. The aim of the present study was to analyze the levels of Aβ42, hTau (total Tau) and ubiquitin in CSF of North Indian population. CSF Aβ42, Tau and ubiquitin were measured in CSF of AD patients as well as controls using ELISA assays. Here we report low Aβ42 levels in AD patients (324.24 ± 76.38 pg/ml) as compared to those in non-AD (NAD) (668.34 ± 43.13 pg/ml), neurological controls (NCs) (727.28 ± 46.49 pg/ml) and healthy controls (HCs) (976.47 ± 124.46 pg/ml). In contrast, hTau and ubiquitin levels were significantly high (568.65 ± 48.89 pg/ml and 36.82 ± 4.34 ng/ml, respectively) in AD patients compared to those in NAD, NC and HC. The hTau levels were 267.37 ± 36.64 pg/ml, 167.34 ± 44.27 pg/ml and 107.62 ± 24.27 pg/ml in NAD, NC and HC, respectively. Similarly, ubiquitin levels were 23.57 ± 2.32 ng/ml, 19.76 ± 3.64 ng/ml and 13.24 ± 4.56 ng/ml in NAD, NC and HC, respectively. In conclusion, low Aβ42 and high Tau–ubiquitin levels were found in North Indian AD patients.  相似文献   
70.
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