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   10329篇
  免费   459篇
  国内免费   65篇
耳鼻咽喉   119篇
儿科学   103篇
妇产科学   83篇
基础医学   1161篇
口腔科学   298篇
临床医学   786篇
内科学   2279篇
皮肤病学   284篇
神经病学   655篇
特种医学   543篇
外科学   2042篇
综合类   58篇
一般理论   2篇
预防医学   412篇
眼科学   87篇
药学   807篇
中国医学   28篇
肿瘤学   1106篇
  2023年   55篇
  2022年   102篇
  2021年   175篇
  2020年   107篇
  2019年   145篇
  2018年   201篇
  2017年   147篇
  2016年   190篇
  2015年   194篇
  2014年   248篇
  2013年   291篇
  2012年   493篇
  2011年   527篇
  2010年   320篇
  2009年   258篇
  2008年   472篇
  2007年   473篇
  2006年   479篇
  2005年   465篇
  2004年   464篇
  2003年   463篇
  2002年   444篇
  2001年   332篇
  2000年   329篇
  1999年   321篇
  1998年   171篇
  1997年   103篇
  1996年   100篇
  1995年   103篇
  1994年   88篇
  1993年   58篇
  1992年   229篇
  1991年   211篇
  1990年   222篇
  1989年   221篇
  1988年   177篇
  1987年   198篇
  1986年   165篇
  1985年   157篇
  1984年   105篇
  1983年   86篇
  1982年   44篇
  1981年   55篇
  1979年   95篇
  1978年   42篇
  1977年   56篇
  1974年   47篇
  1972年   42篇
  1971年   41篇
  1969年   45篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
Advanced glycation end products are the chemical modification of proteins induced by sugars in a hyperglycemic condition. Extracellular matrix proteins are prominent targets of nonenzymatic glycation because of their slow turnover rates. The aim of this study was to investigate the influence of nonenzymatic glycation of type I collagen on the migration of keratinocytes. The migration of keratinocytes was dramatically promoted on native type I collagen-coated dishes compared with that on uncoated dishes. When type I collagen was glycated with glycolaldehyde, large amounts of advanced glycation end products were produced; the glycated collagen I-coated dishes did not promote the migration of keratinocytes. Glycated collagen I did not affect the proliferative capacity of keratinocytes. However, the adhesion of keratinocytes to glycated collagen I was profoundly diminished in a glycation intensity-dependent manner. alpha2beta1 integrin is responsible for the migration and adhesion of keratinocytes to type I collagen. Pretreatment with glycated collagen I did not affect the expression level or functional activity of alpha2beta1 integrin on keratinocytes. These findings suggest that in the presence of glycated collagen I, keratinocytes lose their adhesive and migratory abilities. As the glycation did not modify the alpha2beta1 integrin on keratinocytes, it is suggested that glycation may diminish the binding capacity of type I collagen.  相似文献   
23.
BACKGROUND: Although there is lymphatic flow into the popliteal fossa from a skin tumor located in the lower leg, popliteal metastasis is extremely rare. Recently, sentinel lymph nodes outside traditional nodal basins have been identified. This study investigated the incidence of sentinel nodes in the popliteal region and the indication for biopsy. METHODS: Fourteen patients with various skin cancers involving the lower extremities (nine melanomas, four squamous cell carcinomas, and one sweat gland carcinoma) underwent lymphoscintigraphy and excision with sentinel lymph node biopsy. RESULTS: In all 14 patients, hot spots showed accumulation in the groin region. Five of 14 patients (36%) demonstrated popliteal sentinel nodes in addition to the inguinal nodes. Three of five popliteal sentinel nodes were histologically studied. A patient with acral melanoma demonstrated micrometastasis of melanoma cells in a popliteal node but not in the groin node. CONCLUSION: This study demonstrates that sentinel lymph nodes located in the popliteal fossa are frequently detected by lymphoscintigraphy and that biopsy should be performed if popliteal nodes are identified.  相似文献   
24.
25.
OBJECTIVE: Neuropsychiatric disturbances are common and burdensome symptoms of dementia. Assessment and measurement of neuropsychiatric disturbances are indispensable to the management of patients with dementia. Neuropsychiatric Inventory (NPI) is a comprehensive assessment tool that evaluates psychiatric symptoms in dementia. We translated the NPI-Caregiver Distress Scale part of NPI (NPI-D) and NPI-Brief Questionnaire Form (NPI-Q) into Japanese and examined their validity and reliability. SUBJECTS AND METHODS: The subjects were 152 demented patients and the caregivers who lived with them. These patients consisted of 76 women and 76 men; their mean age was 73.9 +/- 7.8 (S.D.; range: 49 to 93) years. Their caregivers consisted of 46 men and 106 women; their mean age was 65.0 +/- 11.4 (S.D.; range: 35 to 90) years. The Mini-Mental State Examination (MMSE) was conducted with all patients and NPI-Q, NPI, NPI-D, and the Zarit caregiver burden interview (ZBI) were conducted with all caregivers. We examined validity of NPI-D by comparing its score with the MMSE and ZBI scores, and the validity of NPI-Q by comparing its score with the NPI and NPI-D scores. In order to evaluate test-retest reliability, NPI-D was re-adopted to 30 randomly selected caregivers by a different examiner one month later and NPI-Q was re-executed by 27 randomly selected caregivers one day later. RESULTS: Total NPI-D score was significantly correlated with ZBI (rs = 0.59, p < 0.01). Test-retest reliability of NPI-D was adequate (ri = 0.47, p < 0.01). Total NPI-Q severity score and distress score were strongly correlated with NPI (r = 0.77, p < 0.01) and NPI-D (r = 0.80, p < 0.01) scores, respectively. Test-retest reliability of the scores of NPI-Q was acceptably high (the severity score; ri = 0.81, p < 0.01, the distress score; ri = 0.80, p < 0.01). CONCLUSION: The Japanese version of NPI-D and NPI-Q demonstrated sufficient validity and reliability as well as the original version of them. These are useful tools for evaluating psychiatric symptoms in demented patients and their caregivers' distress attributable to these symptoms.  相似文献   
26.
A partially purified extract (COL 1-6) from whole plant of Cordia salicifolia showed an inhibitory effect on herpes simplex virus type 1 (HSV-1). The activity of COL 1-6 on different steps of HSV-1 replication in HeLa cells was investigated. Under single-cycle replication conditions, COL 1-6 exerted a greater than 99.9% inhibition in virus yield when added to the cells 3 h or 1.5 h before infection, and even when added 8 h after infection the extract still caused a greater than 99% inhibition. The extract has been shown to have a direct virucidal activity. And also, analysis of early events following infection showed that COL 1-6 affected viral penetration in HeLa cells but did not interfere with adsorption to the cells.  相似文献   
27.
Two hybridomas secreting two monoclonal antibodies IgG1 B1.4 and IgG2a B1.6 were obtained by immunizing BALB/c mice with human bladder cancer cell line EJ-1. In immunohistochemical staining of cryopreserved tissues, B1.4 reacted with 0 of 9 grade 1 TCC, 6 of 11 grade 2, all of 6 grade 3 and five metastatic specimens. The antigen recognized by B1.4 was not expressed by normal urothelial cells but were expressed by vascular endothelial cells and muscle of tunica media. The target antigen of B1.6 was expressed by normal urothelial cells and all grade of TCC. In this study, it was demonstrated that poorly differentiated bladder cancer and metastatic specimens of bladder cancer express a vascular carbohydrate antigen. Taking the escape mechanism of immune surveillance, into consideration, it is possible that the antigen recognized by B1.4 is an indicator of metastatic potential of bladder cancer.  相似文献   
28.
Antibodies to 3-methoxy-4-aminoazobenzene (3-MeO-AAB) and 2-methoxy-4-aminoazobenzene (2-MeO-AAB) DNA adducts were raised in rabbits against in vitro-adducted DNA samples. The enzyme-linked immunosorbent assay (ELISA) was used to determine the sensitivity and specificity of these antibodies. They proved highly specific for the modified DNA used as the immunogen, but cross-reacted with each other. Moreover, they showed cross reactivity with DNA modified by 4-( o -tolylazo)- o -toluidine, but not by other carcinogens, such as 4-aminobiphenyl or 4-nitroquinoline 1-oxide. The 50% inhibition level of antibody binding in the competitive ELISA was at 10–20 fmol of modified base per assay (equivalent to 1–2 adducts per 106 bases). Immunohistochemical staining indicated that these antibodies bind specifically to nuclear components of the liver in rats given either 3-MeO-AAB or 2-MeO-AAB at the dose of 50 mg/kg body weight.  相似文献   
29.
The vasodilator effects of C-type natriuretic peptide (CNP) were investigated in isolated rat cerebral arterioles. CNP caused dose-dependent vasodilation, maximally by 10.0±2.2% at 10−6 M. The median effective concentration (EC50) was 5.2×10−10 M. In contrast, atrial natriuretic peptide and B-type natriuretic peptide, other members of the natriuretic peptide family, produced little or no vasodilation. Pretreatment with methylene blue (10−4 M) abolished CNP-induced vasodilation, whereas pretreatment with NG-monomethyl--arginine or indomethacin did not inhibit vasodilation. Thus, CNP is suggested to cause significant vasodilation in cerebral arterioles via a cyclic guanosine monophosphate-dependent mechanism. © 1997 Elsevier Science B.V. All rights reserved.  相似文献   
30.
A review of data on 360 patients with esophageal squamous cell carcinoma who underwent esophageal resection revealed 14 cases (3.9%) and 16 lesions with synchronous gastric carcinomas. Among the 16 lesions, there were 14 (87.5%) early gastric carcinomas and two advanced carcinomas. Of the 14 early gastric carcinomas, two were minute (less than 5 mm in the largest diameter) early gastric carcinomas and four small (6-10 mm in the largest diameter). These gastric carcinomas were in a relatively early stage. The six early gastric carcinomas were not detected preoperatively. However, a thorough observation of the gastric mucosa could not be done in four of those due to stenosis which had developed as a result of the esophageal carcinoma. Therefore, intraoperative gastric observation should be done in cases in which the findings of the preoperative endoscopic examination of the stomach are inadequate and the upper gastrointestinal series reveal certain gastric abnormalities.  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