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   3912070篇
  免费   298758篇
  国内免费   34589篇
耳鼻咽喉   51360篇
儿科学   120550篇
妇产科学   95028篇
基础医学   511712篇
口腔科学   107077篇
临床医学   372464篇
内科学   714735篇
皮肤病学   86618篇
神经病学   297964篇
特种医学   150704篇
外国民族医学   952篇
外科学   552326篇
综合类   202527篇
现状与发展   110篇
一般理论   1307篇
预防医学   323380篇
眼科学   81359篇
药学   306457篇
  860篇
中国医学   59171篇
肿瘤学   208756篇
  2021年   46052篇
  2020年   38152篇
  2019年   45936篇
  2018年   53056篇
  2017年   48822篇
  2016年   50337篇
  2015年   62283篇
  2014年   81184篇
  2013年   113834篇
  2012年   146036篇
  2011年   154301篇
  2010年   110799篇
  2009年   101530篇
  2008年   138581篇
  2007年   143322篇
  2006年   140460篇
  2005年   129339篇
  2004年   118288篇
  2003年   111742篇
  2002年   105038篇
  2001年   172386篇
  2000年   174264篇
  1999年   142688篇
  1998年   40975篇
  1997年   36416篇
  1996年   36876篇
  1995年   35743篇
  1994年   33029篇
  1993年   30757篇
  1992年   110528篇
  1991年   106707篇
  1990年   103334篇
  1989年   99438篇
  1988年   91351篇
  1987年   89790篇
  1986年   84496篇
  1985年   80707篇
  1984年   60446篇
  1983年   51179篇
  1982年   30428篇
  1979年   53899篇
  1978年   38303篇
  1977年   32327篇
  1976年   30020篇
  1975年   32036篇
  1974年   38015篇
  1973年   36262篇
  1972年   33870篇
  1971年   31437篇
  1970年   28911篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
BACKGROUND: Recent studies have reported a relationship between obesity and periodontal disease. Obesity is the strongest risk factor for type 2 diabetes, which is, in turn, a risk factor for periodontal disease. An oral glucose tolerance test is necessary to diagnose diabetes; however, no study has examined the relationship between obesity and periodontal disease by taking oral glucose tolerance test results into consideration. METHODs: In all, 584 Japanese women aged between 40 and 79 years old, with at least 10 teeth, underwent health examinations. Body mass index, waist-hip ratio, body fat, and oral glucose tolerance test results were used as independent variables with known risk factors for periodontal disease. Mean probing pocket depth and mean attachment loss were used as the dependent variables. RESULTS: In all of the analyses, body mass index, body fat, and waist--hip ratio were significantly associated with the highest quintile of mean probing pocket depth, even when adjusted for oral glucose tolerance test results. In the multivariate analysis, the subjects with the highest quartile of body mass index had a significantly higher odds ratio (OR) for the highest quintile of mean probing pocket depth [OR, 4.3; 95% confidence interval (CI), 2.1--8.9; p<0.001], whereas neither impaired glucose tolerance nor diabetes were significantly associated with deep pockets. The relationships between the obesity indexes and mean attachment loss did not reach statistical significance. CONCLUSION: Obesity was associated with deep pockets in Japanese women, even after adjusting for oral glucose tolerance test.  相似文献   
992.
By the formation of cyclic guanosine 3',5'-monophosphate (cGMP), nitric oxide (NO)-sensitive enzyme-soluble guanylate cyclase (sGC) plays a receptor role for NO within the NO-cGMP signaling cascade, which is involved in vasodilatation and neurotransmission. The hypothesis that NO-cGMP signaling molecules modulate cells of the dentin-pulp complex was investigated in rat molars by histochemical, immunohistochemical, immuno-ultrastructural, and organ bath techniques. NO synthase (NOS) I-III, the sGC alpha(2)-subunit/beta(1)-subunit, and cGMP were detected in odontoblasts and blood vessels. NOS I, sGC alpha(2), and cGMP were identified in nerve fibers. Treatment of rat molars with the NO donor NONOate (10(-5) M) increased cGMP staining intensities in blood vessels and odontoblasts, while NO synthase inhibitor L-NAME (10(-4) M) attenuated intensity of the reaction products for cGMP, suggesting an effect of endogenous NO on sGC. These correlations of patterns and alterations of cGMP staining intensities after treatment with the NO donor or NO inhibitor might represent an NO-sGC-cGMP signaling-dependent modulation of odontoblasts, blood vessels, and nerve fibers in the dentin-pulp complex.  相似文献   
993.
We present the case of a sailor who sustained a penetrating grease gun injury to his face, and the challenging subsequent series of events.  相似文献   
994.
OBJECTIVES: To assess the sensitivity and responsiveness of an oral health related quality of life measure to tooth whitening. METHODS: Following screening at a clinic, 87 subjects were given an array of tooth whitening products to use at home and reviewed 8 weeks later. Subjects self-completed the 49-item Oral Health Impact Profile (OHIP) at baseline and follow-up, and rated their satisfaction with the whiteness of their teeth compared to baseline on a global transition scale. RESULTS: In terms of sensitivity, observed changes were apparent in overall OHIP scores (P<0.05) and across several domains, notably functional limitation (P<0.01). However, the magnitude of change (effect size) was generally small except for the functional domain. There was an observed gradient in observed change in OHIP scores and in the magnitude of such changes (effect sizes) in relation to global rating of satisfaction with the outcome, supporting the responsiveness of the measure. CONCLUSION: The OHIP scale is sensitive and responsive to the effects of tooth whitening. Greatest sensitivity and responsiveness was in relation to functional limitations. These findings have implications for the use of oral health related quality of life measures as an outcome measure of interventions aimed at improving dental aesthetics through tooth whitening.  相似文献   
995.
Possible link between glycolysis and apoptosis induced by sodium fluoride   总被引:4,自引:0,他引:4  
Fluoride has been used to prevent caries in the dentition, but the possible underlying mechanisms of cytotoxicity induction by this compound are still unclear. Since fluoride is known as an inhibitor of glycolytic enzymes, we investigated the possible connection between NaF-induced apoptosis and glycolysis in human promyelocytic leukemia HL-60 cells. NaF-induced apoptotic cell death is characterized by caspase activation, internucleosomal DNA fragmentation, loss of mitochondrial membrane potential, and production of apoptotic bodies. Higher activation of caspases-3 and -9, as compared with that of caspase-8, suggested the involvement of an extrinsic pathway. Utilization of glucose was nearly halted by NaF, whereas that of glutamine was rather enhanced. NaF enhanced the expression of Bad protein, but not that of Bcl-2 and Bax proteins, and reduced HIF-1alpha mRNA expression. Analysis of these data suggests a possible link between glycolysis and apoptosis.  相似文献   
996.
An online database of proteomes for two-dimensional electrophoresis (2DE) gel data was constructed and it is now freely accessible through a web-based interface. Proteins from three oral bacteria, Streptococcus mutans UA159, Actinobacillus actinomycetemcomitans HK1651, and Porphyromonas gingivalis W83, whose genome databases are freely available, were separated by 2DE, and protein spots were analyzed by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) and identified. About 1000 spots from the gels of P. gingivalis W83 were extracted and analyzed by MALDI-TOF, and 330 proteins were identified. In addition, 160 of 240 spots of A. actinomycetemcomitans and 158 of 356 spots of S. mutans were identified. Information such as spot coordinates on the gels, protein names (predicted functions), molecular weights, isoelectroric points, and links to online databases, including Oral Pathogen Sequence Databases of the Los Alamos National Laboratory Bioscience Division (ORALGEN) and National Center for Biotechnology Information (NCBI) or The Institute Genomic Research (TIGR), were stored in tables accessible through the relational database management system MySQL on an Apache web server. To test for functionality of this database system, responses of S. mutans to environmental changes were analyzed using the database and 21 spots on the gel were identified as proteins whose expression had been increased or decreased by environmental pH change without in-gel trypsin digestion, protein extraction, or MALDI-TOF/TOF-MS (mass spectrometer) analysis. The identified proteins are agreement with those reported in previous papers on acid tolerance of S. mutans, demonstrating the usefulness of the system. This database is available at http://www.myamagu.dent.kyushu-u.ac.jp/~bioinformatics/index.html or http://www.bipos.mascat.nihon-u.ac.jp/index.html.  相似文献   
997.
Cementum and dentin in hypophosphatasia   总被引:2,自引:0,他引:2  
Hypophosphatasia (HPP) often leads to premature loss of deciduous teeth, due to disturbed cementum formation. We addressed the question to what extent cementum and dentin are similarly affected. To this end, we compared teeth from children with HPP with those from matched controls and analyzed them microscopically and chemically. It was observed that both acellular and cellular cementum formation was affected. For dentin, however, no differences in mineral content were recorded. To explain the dissimilar effects on cementum and dentin in HPP, we assessed pyrophosphate (an inhibitor of mineralization) and the expression/activity of enzymes related to pyrophosphate metabolism in both the periodontal ligament and the pulp of normal teeth. Expression of nucleotide pyrophosphatase phosphodiesterase 1 (NPP1) in pulp proved to be significantly lower than in the periodontal ligament. Also, the activity of NPP1 was less in pulp, as was the concentration of pyrophosphate. Our findings suggest that mineralization of dentin is less likely to be under the influence of the inhibitory action of pyrophosphate than mineralization of cementum.  相似文献   
998.
AIM: To detect and to visualize radiographically vertical root fractures in extracted teeth with a prototype of a novel, high resolution, three-dimensional flat panel volume detector computer tomograph (FD-VCT) system. SUMMARY: Five teeth with root fillings and clinical symptoms such as fistulas and isolated periodontal pockets of 8 mm or more were extracted after dental radiography indicating lateral or periapical lesions. Vertical root fractures or cracks were suspected because of the symptoms and clinical findings were evident after extraction in all cases but fracture lines were not visible on routine dental radiographs acquired before extraction. The extracted teeth were explored with a prototype of a FD-VCT. Using the FD-VCT, in all cases vertical root fractures or crack lines could be detected clearly in different views, depiction-modes and cross-sections at a spatial resolution of 140 microm. The evaluation of the fracture lines and teeth could be performed in three-dimensional views. The FD-VCT findings were confirmed by detailed inspection of the extracted teeth. KEY LEARNING POINTS: The FD-VCT is an innovative diagnostic tool for non-destructive, three-dimensional evaluation of extracted teeth in pre-clinical and experimental studies. The FD-VCT allows precise visualization and evaluation of vertical root fractures or cracks in extracted teeth. Clinical application of the system may be possible if technical modifications reduce the exposure dose: the high resolution detector systems of the FD-VCT should be combined with radiation systems that focus the radiation to the area of interest.  相似文献   
999.
A Khan  M H Moola  P Cleaton-Jones 《SADJ》2005,60(10):418-421
AIM: To determine trends in fluorosis prevalence at water fluoride levels <0.3, >0.3 to <0.7, and >0.7 to 1.4 ppm from 1980 to 2000. METHODS: A systematic review of 55 published articles identified in a Medline search for peer-reviewed articles on fluorosis published from 1 January 1980 to 31 December 2000. The prevalence recorded with any fluorosis index was pooled and the trends over time were determined in the three water concentration categories. RESULTS: The fluorosis prevalence for the three fluoride categories were 16.7, 27.4 and 32.2 percent, respectively. A 16-fold and a 2-fold increase in fluorosis prevalence compared with reported rates in the 1940s was seen in non-fluoridated (= 0.3 ppm F) and fluoridated (>0.7 to = 1.4 ppm F) areas, respectively. There has been an increase in fluorosis prevalence over time in the three fluoride water concentration categories but linear regression analysis showed that none are significantly different from zero. CONCLUSION: This systematic review concurs with recent reports of an increase in fluorosis prevalence in fluoridated and non-fluoridated communities.  相似文献   
1000.
A novel treatment procedure is introduced for severe clicking of the temporomandibular joint (TMJ) associated with anterior disc displacement (ADD), using injections with botulinum toxin (BTX-A) in the lateral pterygoid muscle (LP). It has been suggested that ADD may be caused, precipitated, or maintained by LP activity, but the role of the LP in the dynamics of the TMJ clicking is uncertain. The case report includes 2 women, followed with clinical examinations, TMJ imaging, and electromyography (EMG), in whom local anesthetics in the LP could abolish the clicking for several days. BTX-A block of the LP (30 U Botox, given twice under EMG guidance with 6-month interval) temporarily reduced the action of the muscle, but the clicking was permanently eliminated and did not return during the observation period of 1 year, and a small but distinctive positional improvement in the disc-condyle relationship was obtained. However, the precise mechanisms behind the favourable treatment outcome are unclear.  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