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   198296篇
  免费   10384篇
  国内免费   783篇
耳鼻咽喉   2132篇
儿科学   5110篇
妇产科学   3766篇
基础医学   24116篇
口腔科学   3767篇
临床医学   20698篇
内科学   41075篇
皮肤病学   2679篇
神经病学   19692篇
特种医学   8296篇
外国民族医学   14篇
外科学   30419篇
综合类   2132篇
现状与发展   1篇
一般理论   150篇
预防医学   14257篇
眼科学   4494篇
药学   12822篇
  14篇
中国医学   270篇
肿瘤学   13559篇
  2024年   572篇
  2023年   1247篇
  2022年   1938篇
  2021年   4594篇
  2020年   2714篇
  2019年   4474篇
  2018年   5115篇
  2017年   3767篇
  2016年   4090篇
  2015年   4781篇
  2014年   6936篇
  2013年   9451篇
  2012年   14208篇
  2011年   14834篇
  2010年   8319篇
  2009年   7721篇
  2008年   13046篇
  2007年   13660篇
  2006年   13267篇
  2005年   13216篇
  2004年   12373篇
  2003年   11283篇
  2002年   10825篇
  2001年   1647篇
  2000年   1249篇
  1999年   1688篇
  1998年   2306篇
  1997年   1835篇
  1996年   1619篇
  1995年   1475篇
  1994年   1259篇
  1993年   1242篇
  1992年   849篇
  1991年   801篇
  1990年   694篇
  1989年   655篇
  1988年   589篇
  1987年   533篇
  1986年   558篇
  1985年   597篇
  1984年   756篇
  1983年   670篇
  1982年   875篇
  1981年   770篇
  1980年   695篇
  1979年   408篇
  1978年   437篇
  1977年   397篇
  1976年   364篇
  1974年   276篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
PURPOSE: The study goal was to evaluate the incidence of patients older than 40 years who required third molar removal. PATIENTS AND METHODS: Two prospective 5-year studies were compared over a 10-year period of 1992 to 1997 and 1997 to 2002. The study was initiated to evaluate how the large increase in the older population with longer life expectancies is reflected in the third molar population. RESULTS: In 1997, 10.5% of patients requiring third molar surgery were 40 years or older. In 2002, 17.3% of patients were 40 years or older. CONCLUSIONS: It is well known that patients 40 years and older have increased risk in removal of third molars. It is concluded that 1 patient in 5 in the high-risk category is in a very high risk category. The risk to patients and to the profession can be dramatically reduced by considering early removal of abnormal third molars.  相似文献   
82.
The purpose of this article is to review the literature on interprofessional education (IPE) and report on a preliminary survey of the current status of interprofessional education in seven academic health centers (AHCs) that have schools of dentistry associated with them. There is wide variability in interpretation of the term "interprofessional," and many barriers to interprofessional education exist including already overcrowded curricula in health professions schools, lack of support from faculty and administration, and financial constraints. Based on interviews completed at the authors' home institutions, it was recommended that topics such as ethics, communication skills, evidence-based practice, and informatics could be effectively taught in an interprofessional manner. Currently, some academic health centers are attempting to develop interprofessional education programs, but most of these efforts do not include dental students. Of the seven AHCs investigated in this study, only two had formal interprofessional educational activities that involved students from two or more health professions education programs. Dental school participants in this study professed a strong interest in interprofessional programs, but many interviewees from other professional schools and AHC administrators perceived that the dental school was isolated from other schools and disinterested in IPE. Many health care setting models in the future will include dentists as part of an interdisciplinary health care team; consequently, it is important for dental schools to become an active participant in future interprofessional educational initiatives.  相似文献   
83.
84.
BACKGROUND: The purpose of this study was to evaluate histologically the contribution of inorganic bovine bone biomaterial in a new experimental bone defect in dogs at different healing periods and to examine newly formed bone around the grafted mineral particles and their relationship in membrane-protected (test) and non-protected intrabony (control) defects. METHODS: Four round intrabony defects, 5 x 4 mm were made bilaterally (at different times) on the lateral bony mandibular angle in eight dogs. Two defects were filled with bovine bone mineral (BBM) particles and two remained non-grafted but were blood clotted. A collagen membrane covered each defect type (n = 4). This procedure was repeated on the contralateral side at a different given time to obtain two different healing periods in each dog. Thus, four specimens were obtained at 3, 6, 12, and 24 months postoperatively for each healing period. The non-decalcification method (Donath technique) with Stevenel's blue and van Gieson's picro fuchsin staining was used for histological examination. RESULTS: Newly formed bone was observed at all examined defect types. The BBM particles were clearly evident regardless of the healing period. At 3 and 6 months, newly formed bone, woven in nature, was incorporated with the grafted particles. High cellular bone with occasional osteoclasts was noted towards the surface of the mineral particles. No substantial difference was observed between the protected and the non-protected defects except for higher ossified centers around the membrane-protected defects. At the non-grafted sites, the membrane-protected defect showed newly formed bone near the bony walls, and particularly under the membrane, establishing a bony bridge over the defect at the healing periods. The non-grafted unprotected defect (control) showed bone formation only at the base and close to the bony walls leaving a healed concave configuration. At 1 and 2 years, the grafted sites showed full bone healing configuration. However, the grafted particles still dominated the previous defect area and were completely surrounded by the newly formed bone. Osteons and lamellar bone arrangement were established but the bone was still highly cellular and osteoclasts could still be identified. The non-grafted membrane-protected sites showed excellent bone healing although areas of non-mineralized soft tissue were often seen. The control sites healed but still presented with a concave surface configuration. CONCLUSIONS: BBM biomaterial is a highly osteoconductive material. In a 4-wall bony defect, newly formed bone was well evident in establishing excellent bone healing configuration with or without a regenerative biological barrier. The grafted material dominated the experimental sites with no substantial resorption at any healing period up to 2 years observation.  相似文献   
85.
Prospective evaluation of implants connected to teeth   总被引:1,自引:0,他引:1  
PURPOSE: This prospective clinical trial examined the effect on teeth and implants when rigidly or non-rigidly connected in a cross-arch model. MATERIALS AND METHODS: Thirty patients received 2 implants, 1 on each side of the mandible, and were restored with 3-unit fixed partial dentures connected either rigidly or non-rigidly to an abutment tooth. Patients were followed for at least 5 years post-restoration. RESULTS: Repeated-measures analysis revealed no significant difference in crestal bone loss at implants (rigid versus non-rigid methods). An overall significant difference (P < .001) was found comparing methods for teeth. Paired t tests revealed no significant differences in crestal bone levels for implants or teeth at the 5-year recall. Kaplan-Meier methods and the Cox proportional hazards model showed no differences between attachment methods with regard to success based on survival and bone loss criteria. During the 5-year recall period, 1 implant (rigid side) was removed. Four implants developed bone loss greater than 2 mm during the course of this trial. One tooth on the rigid side and 2 teeth on the non-rigid side had greater than 2 mm of crestal bone loss and were removed secondary to fractures. In all, 5 abutment teeth were removed, all of which had been treated with root canal therapy and fractured at the interface of the post within the tooth. There was no clear relationship of tooth fracture to attachment. Repeated-measures analysis of mobility values revealed no significant changes over the time course of this study, and paired t tests revealed no statistically significant differences between implants for mobility. Repeated-measures analysis and paired t tests for probing depth revealed no significant changes over the time course of this study. There were no significant differences in soft tissue indices for either attachment method. The percentage of patients who had measurable intrusion was 66% for the non-rigid group, and 44% for the rigid group; 25% of the non-rigid teeth had greater than 0.5 mm intrusion, compared with 12.5% for the rigid group. For the 2 time periods evaluated, there was no significant increase in intrusion over time. The non-rigid-side implant required more nonscheduled visits to treat problems than the rigid implant and the teeth. Discussion: Most patients were treated successfully with rigid or non-rigid attachment of implants to teeth. CONCLUSION: The high incidence of intrusion and non-scheduled patient visits suggest that alternative treatments without connecting implants to teeth may be indicated.  相似文献   
86.
This Working Section is concerned with evolving methods of assessment in dental education. It focuses on newer methods of assessment that might have relevance for broader application. Although it cannot provide answers to all the questions it raises, it is hoped that the contribution it makes is of value in the process of the development of a global network in dental education.  相似文献   
87.
BACKGROUND: A substantial proportion of people with risk factors for cardiovascular disease (CVD) are not identified before they develop clinical signs and symptoms. A multidisciplinary approach that includes a cardiovascular screening by oral health care providers can affect the identification of people at risk of experiencing cardiovascular events. METHODS: The authors extracted data from the 1999-2000 National Health and Nutrition Examination Survey (NHANES) and the 2001-2002 NHANES for people aged 40 to 85 years with no reported specific risk factors for coronary heart disease (CHD) and who had not seen a physician in the previous 12 months but had seen a dentist. They used these data to estimate the 10-year Framingham-based risk calculation scores for each subject to determine their global risk of experiencing acute CHD events. RESULTS: Eighteen percent of the male subjects had an increased 10-year global risk of experiencing a CHD event (> 10 percent risk score), 14.3 percent had a moderate, above-average risk score (> 10-< 20 percent), and an additional 4.3 percent had a high risk score (> or = 20 percent). Only one female subject had a risk score greater than 10 percent. When the authors extrapolated these results to the 2000 U.S. census data, they found that among men aged 40 to 85 years without reported risk factors who had not seen a physician but had seen a dentist in the previous 12 months, 332,262 had a greater than 10 to less than 20 percent risk of experiencing a CHD event, and 72,625 had a 20 percent or greater 10-year risk of experiencing a CHD event. CONCLUSION: Dentists can play an important role in identifying people in need of primary prevention strategies for CVD.  相似文献   
88.
BACKGROUND: Growth factors are generally accepted to be essential mediators of tissue repair via well-established mechanisms of action that include stimulatory effects on angiogenesis and cellular proliferation, ingrowth, differentiation, and matrix biosynthesis. The aim of this study was to evaluate in a large-scale, prospective, blinded, and randomized controlled clinical trial the safety and effectiveness of purified recombinant human platelet-derived growth factor (rhPDGF-BB) mixed with a synthetic beta-tricalcium phosphate (beta-TCP) matrix for the treatment of advanced periodontal osseous defects at 6 months of healing. METHODS: Eleven clinical centers enrolled 180 subjects, each requiring surgical treatment of a 4 mm or greater intrabony periodontal defect and meeting all inclusion and exclusion criteria. Subjects were randomized into one of three treatment groups: 1) beta-TCP + 0.3 mg/ml rhPDGF-BB in buffer; 2) beta-TCP + 1.0 mg/ml rhPDGF-BB in buffer; and 3) beta-TCP + buffer (active control). Safety data were assessed by the frequency and severity of adverse events. Effectiveness measurements included clinical attachment levels (CAL) and gingival recession (GR) measured clinically and linear bone growth (LBG) and percent bone fill (% BF) as assessed radiographically by an independent centralized radiology review center. The area under the curve (AUC), an assessment of the rate of healing, was also calculated for CAL measurements. The surgeons, clinical and radiographic evaluators, patients, and study sponsor were all masked with respect to treatment groups. RESULTS: CAL gain was significantly greater at 3 months for group 1 (rhPDGF 0.3 mg/ml) compared to group 3 (beta-TCP + buffer) (3.8 versus 3.3 mm; P = 0.032), although by 6 months, this finding was not statistically significant (P = 0.11). This early acceleration of CAL gain led to group 1 exhibiting a significantly greater rate of CAL gain between baseline and 6 months than group 3 as assessed by the AUC (68.4- versus 60.1-mm weeks; P = 0.033). rhPDGF (0.3 mg/ml)-treated sites also had significantly greater linear bone gain (2.6 versus 0.9 mm, respectively; P < 0.001) and percent defect fill (57% versus 18%, respectively; P < 0.001) than the sites receiving the bone substitute with buffer at 6 months. There was less GR at 3 months in group 1 compared to group 3 (P = 0.04); at 6 months, GR for group 1 remained unchanged, whereas there was a slight gain in gingival height for group 3 resulting in comparable GR. There were no serious adverse events attributable to any of the treatments. CONCLUSIONS: To our knowledge, this study is the largest prospective, randomized, triple-blinded, and controlled pivotal clinical trial reported to date assessing a putative periodontal regenerative and wound healing therapy. The study demonstrated that the use of rhPDGF-BB was safe and effective in the treatment of periodontal osseous defects. Treatment with rhPDGF-BB stimulated a significant increase in the rate of CAL gain, reduced gingival recession at 3 months post-surgery, and improved bone fill as compared to a beta-TCP bone substitute at 6 months.  相似文献   
89.
Template fabrication for a midpalatal orthodontic implant: technical note   总被引:2,自引:0,他引:2  
An implant has been developed as an adjunct to conventional orthodontic anchorage. Planning is advisable to determine the available bone and soft tissue thickness and the optimum position for orthodontic utilization. A simple method is described for fabrication of a radiographic and surgical template to aid in optimal placement of the implant.  相似文献   
90.
This article demonstrates the feasibility of using recombinant human bone morphogenetic protein (rhBMP-2) as a substitute for autogenous iliac crest bone for repair of congenital facial clefts in humans. In this series, 50 cleft sites were repaired in 43 patients using rhBMP-2 without the use of autogenous graft tissue. Successful osseous union was achieved in 49 of the 50 sites. In one patient, the graft failed to consolidate. Severe clefts were managed by combining distraction osteogenesis and rhBMP-2. Eliminating the need to harvest autogenous iliac crest bone resulted in substantial decrease in morbidity. The constructed alveolus performed clinically as normal bone and responded to natural tooth eruption and orthodontic movement. Histology of the tissue constructed showed normal, vital bone. Although additional investigation is warranted to determine the optimum protocol for the use of this material in alveolar cleft repair, the technique should be considered as a viable treatment option in cases in which avoiding iliac crest harvesting is desirable.  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