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   102819篇
  免费   7617篇
  国内免费   375篇
耳鼻咽喉   1130篇
儿科学   2537篇
妇产科学   1649篇
基础医学   14542篇
口腔科学   2193篇
临床医学   10507篇
内科学   21853篇
皮肤病学   1801篇
神经病学   11004篇
特种医学   4204篇
外国民族医学   6篇
外科学   14640篇
综合类   1253篇
一般理论   73篇
预防医学   7935篇
眼科学   1744篇
药学   6915篇
  2篇
中国医学   111篇
肿瘤学   6712篇
  2023年   636篇
  2022年   1112篇
  2021年   2184篇
  2020年   1401篇
  2019年   1976篇
  2018年   2428篇
  2017年   1787篇
  2016年   2135篇
  2015年   2479篇
  2014年   3269篇
  2013年   4297篇
  2012年   6651篇
  2011年   6709篇
  2010年   3961篇
  2009年   3613篇
  2008年   5926篇
  2007年   6433篇
  2006年   5964篇
  2005年   5902篇
  2004年   5512篇
  2003年   4917篇
  2002年   4874篇
  2001年   1870篇
  2000年   1788篇
  1999年   1664篇
  1998年   1222篇
  1997年   997篇
  1996年   807篇
  1995年   815篇
  1994年   696篇
  1993年   635篇
  1992年   1152篇
  1991年   1067篇
  1990年   1013篇
  1989年   972篇
  1988年   865篇
  1987年   811篇
  1986年   831篇
  1985年   827篇
  1984年   669篇
  1983年   579篇
  1982年   552篇
  1981年   453篇
  1980年   395篇
  1979年   515篇
  1978年   407篇
  1977年   368篇
  1975年   328篇
  1974年   355篇
  1973年   344篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.

Background  

Acidogenic, acid-tolerant bacteria induce dental caries and require D-alanyl glycerol lipoteichoic acid (D-alanyl LTA) on their cell surface. Because fluoride inhibits acid-mediated enamel demineralization, an elevated antibody response to D-alanyl LTA may indicate subjects with more acidogenic bacteria and, therefore, an association of DMFT with fluoride exposure and gingival health not apparent in low responders.  相似文献   
92.
Seventy-six Class V non-undercut abrasion lesions were restored with composite and either Dentine Adhesive,† Bondlite,‡ ; or Dentin Bonding Agent ,§ without enamel etching. Restorations were trimmed and polished after approximately three weeks, and evaluated for integrity and marginal staining. Recall evaluations were carried out at three months, six months and one year. The cumulative loss incidence at one year for Dentine Adhesive, Bondlite , and Dentin Bonding Agent was 83 per cent, 25 per cent, and 33 per cent, respectively. Restorations with Dentin Bonding Agent had the most severe marginal staining, while Bondlite restorations had least marginal staining.  相似文献   
93.
OBJECTIVE: The aim of this study was to investigate the in-vitro marginal adaptation of all-ceramic class II inlays which were luted with conventional multi-stage pre-treatment cements and one new type of cement, which requires no conditioning. METHODS: The marginal adaptation of 56 all-ceramic inlays was determined with scanning electron microscopy and microleakage tests. The marginal integrity of each tooth was evaluated at cement-dentin and cement-enamel junctions, with regard to the transitions between tooth-cement and cement-inlay. The inlays were luted on human molars with two resin cements, one compomer, one resin modified glass-ionomer and one new resin cement in accordance with the manufacture's recommended pre-treatment. Light- and chemical-curing modifications were investigated. All tests were performed after thermal cycling and mechanical loading (TCML). RESULTS: For the resin cements and the new material the marginal integrity was higher than 90% before and after TCML. The marginal adaptation was between 55-80% for the resin modified glass-ionomer and lower than 20% for the compomer. The microleakage was lower than 20% for all cements, only the compomer showed values up to 100% penetration. SIGNIFICANCE: The difference in marginal integrity between the new universal resin cement without any tooth pre-treatment and conventional resin cements after total-etching, priming and bonding was not significant. Resin GIC may be used with restrictions and compomer cement should not be used with all-ceramic class II inlay restorations.  相似文献   
94.
A case of fatal mediastinitis following an odontogenic infection has been presented. The anatomic pathways through fascial planes from the mouth to the mediastinum have been reviewed. The causes of cervical emphysema when the oral cavity is an entry site have been discussed. Usually this process is benign, but the possibility that gas-forming anaerobes could be present in the emphysema and that insidious mediastinitis could concurrently occur is stressed. The presence of Bacteroides asaccharolyticus in the anaerobic cultures from the submandibular and chest abscesses, and the recovery of aerobic organisms, leads to speculation about a synergistic action between these organisms.  相似文献   
95.
Complications of third molar surgery   总被引:1,自引:0,他引:1  
This article addresses the incidence of specific complications and, where possible, offers a preventive or management strategy. Injuries of the inferior alveolar and lingual nerves are significant issues that are discussed separately in this text. Surgical removal of third molars is often associated with postoperative pain, swelling, and trismus. Factors thought to influence the incidence of complications after third molar removal include age, gender, medical history, oral contraceptives, presence of pericoronitis, poor oral hygiene, smoking, type of impaction, relationship of third molar to the inferior alveolar nerve, surgical time, surgical technique, surgeon experience, use of perioperative antibiotics, use of topical antiseptics, use of intra-socket medications, and anesthetic technique. Complications that are discussed further include alveolar osteitis, postoperative infection, hemorrhage, oro-antral communication, damage to adjacent teeth, displaced teeth, and fractures.  相似文献   
96.
This randomized crossover double-blind trial compared the efficacy of buccal infiltration with 4% articaine and 2% lidocaine (both with 1:100,000 epinephrine) in securing mandibular first molar pulp anesthesia. Injections were given at least 1 week apart in 31 healthy adult volunteers. Electronic pulp testing was undertaken at baseline and at 2 minute intervals until 30 minutes postinjection. A successful outcome was recorded in the absence of pulp sensation on two consecutive maximal pulp tester stimulations (80 muA). 64.5% of articaine and 38.7% of lidocaine infiltrations were successful (p = 0.008). Articaine infiltration produced significantly more episodes of no response to maximum stimulation in first molars than lidocaine (236 and 129, respectively, p < 0.001). Mandibular buccal infiltration is more effective with 4% articaine with epinephrine compared to 2% lidocaine with epinephrine. Both injections were associated with mild discomfort.  相似文献   
97.
Working as part of your team, your dental laboratory can increase your predictable success and decrease the stress of daily practice. This partnership should begin during the treatment planning phase and continue through to the insertion appointment. Many dentists are beginning to view their laboratory technician as a bonafide member of their patient care team. Thorough communication on both sides is crucial to reaching this predictable success. A trusting relationship will enable the dentist and the laboratory technician to communicate effectively. The laboratory must take the responsibility to communicate its concerns to the dentist, just as the dentist must take the responsibility to communicate effectively with the laboratory his or her needs and desires for each case. When effective communication techniques are followed, everyone is a winner. The dentist is more productive per hour and has reduced stress. The dental laboratory does not have to bear the burden of remakes, and spends less time on the phone or sending e-mail for routine cases. And most importantly, the patient receives an exceptional restoration that meets his or her expectations. In the end, the true measure of a great relationship between the dentist and the laboratory is happy patients who refer friends and family to your practice for years to come.  相似文献   
98.
Dental erosion involves dissolution of the hydroxyapatite fraction of enamel and dentine, so agents that reduce the dissolution rate of hydroxyapatite could find application in food products aimed at reducing erosion. This study was performed to test some common food ingredients and additives for their effect on the dissolution rate of hydroxyapatite in a citric acid solution representative of soft drinks. Pyrophosphate, tripolyphosphate and a linear chain polyphosphate (average 25 phosphate units) significantly reduced the hydroxyapatite dissolution rate by 35, 46 and 64%, respectively. Xanthan gum and carboxymethylcellulose significantly reduced the hydroxyapatite dissolution rate by 29 and 16%, respectively. The protective effect may be ascribed to the binding of condensed phosphate or to the formation of an adsorbed layer of gum at the hydroxyapatite surface. Several other common food additives had no statistically significant effect on the hydroxyapatite dissolution rate. Polyphosphate exhibited a considerable persistence of action, causing a reduction in the dissolution rate for 3 h after treatment. Tripolyphosphate was slightly persistent, and pyrophosphate and xanthan gum did not exhibit a substantial persistence of action. A solution containing polyphosphate and xanthan gum reduced the hydroxyapatite dissolution rate by 70% and exhibited a similar persistence of action to the solution containing only polyphosphate. These compounds are suggested to have potential as erosion-reducing agents in soft drinks.  相似文献   
99.
STATEMENT OF PROBLEM: The increasing trend toward esthetics has led to controversy as to the longevity of esthetic restorations and the wisdom of having traditional restorations replaced for esthetic reasons. With the assumption that the way dentists treat their own teeth may be a good indication of the accumulated wisdom of the profession, knowledge of dentists' own restorative choices may provide guidance in selecting the most appropriate restorations. PURPOSE: The purpose of this article was to determine restorative choices of dentists for personal molars and estimate restoration longevity. MATERIAL AND METHODS: Information about dentists' molars was obtained from a Web-based survey designed to receive dentists' demographic data and charting of 8 molar teeth with estimated longevity. Approximately 12,000 e-mails asking to access the website were sent to dentists' addresses randomly selected from a commercial database. Nonrespondents received 1 reminder. The responses were statistically analyzed with a chi-square analysis (alpha=.05). RESULTS: Seven hundred fifty-seven valid replies provided information for 6,034 teeth (22% unrestored, 75% restored, 2% missing). Restorations reported included amalgam (36%), gold inlay/onlay (13%), complete veneer crown (CVC) (10%), metal-ceramic crown (MCC) (8%), and composite (7%). Other esthetic options accounted for less than 3%. Restorations with more than 20 years longevity included amalgam restorations (58%), gold inlays/onlays (48%) and crowns (23%). Fifty-six percent of esthetic restorations and 5% of amalgams were placed in the last 5 years. The following restorations were placed in the last year (n=186): 38% esthetic, 29% crowns (18% MCC; 11% CVC), and 17% gold inlay/onlay or amalgam. Significant differences (P<.001) were identified for dentist's gender, year of graduation and practice location. CONCLUSIONS: Most dentists have not replaced traditional metallic restorations with esthetic alternatives. Dentists still choose nonesthetic options for significant numbers of their own restorations.  相似文献   
100.

Purpose

The inducible enzyme cyclooxygenase-2 (COX-2) catalyzes PGE2 production and plays an important role in the progression of many solid cancers. However, the role of COX-2 expression in cervical lymph node metastases of head and neck cancer has not been clarified yet.

Patient and methods

We comment on a male patient aged 53 who was admitted to an ENT-department with acute bleeding from an advanced hypopharyngeal carcinoma and a frontotemporal mass. Prior to palliative intended radiotherapy, the metastasis was resected. During the procedure, a small amount of tumor tissue was harvested for primary tumor cell culture.

Results

COX-2 overexpression was demonstrated in the primary tumor tissue, the metastasis, in the cultured tumor cells by standard immunohistochemistry, as well as cytochemistry.

Conclusions

A simultaneous expression of COX-2 in head and neck carcinoma was presented for the first time. Besides the prognostic impact in oral carcinogenesis, this COX-2 role of biomarker for aggressive head and neck squamous cell carcinomas should be further evaluated. Additionally, treatment of hypopharyngeal carcinomas with selective COX-2 inhibitors could be beneficial when administered in combination with radiochemotherapy.  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