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   45236篇
  免费   2119篇
  国内免费   363篇
耳鼻咽喉   471篇
儿科学   818篇
妇产科学   1298篇
基础医学   5353篇
口腔科学   1722篇
临床医学   3510篇
内科学   12655篇
皮肤病学   932篇
神经病学   3961篇
特种医学   1188篇
外科学   6833篇
综合类   170篇
一般理论   9篇
预防医学   2461篇
眼科学   719篇
药学   2431篇
  4篇
中国医学   114篇
肿瘤学   3069篇
  2024年   131篇
  2023年   362篇
  2022年   786篇
  2021年   1500篇
  2020年   835篇
  2019年   1119篇
  2018年   1550篇
  2017年   1016篇
  2016年   1110篇
  2015年   1306篇
  2014年   1790篇
  2013年   2357篇
  2012年   3614篇
  2011年   3565篇
  2010年   2010篇
  2009年   1747篇
  2008年   3036篇
  2007年   3149篇
  2006年   2939篇
  2005年   2909篇
  2004年   2621篇
  2003年   2350篇
  2002年   2078篇
  2001年   272篇
  2000年   188篇
  1999年   290篇
  1998年   366篇
  1997年   323篇
  1996年   284篇
  1995年   279篇
  1994年   219篇
  1993年   164篇
  1992年   140篇
  1991年   100篇
  1990年   102篇
  1989年   84篇
  1988年   65篇
  1987年   57篇
  1986年   73篇
  1985年   70篇
  1984年   73篇
  1983年   65篇
  1982年   94篇
  1981年   66篇
  1980年   71篇
  1979年   39篇
  1978年   47篇
  1977年   37篇
  1976年   35篇
  1974年   29篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Multidetector computed tomographic (CT) anatomy was used to evaluate the lungs of 10 loggerhead sea turtle (Caretta caretta) without pulmonary disease, in order to provide a baseline of turtle lung anatomy by CT imaging. In all patients, in this retrospective anatomic study, the CT datasets were carefully evaluated for assessment of the bronchial tree morphology and branching pattern, of the arborization pattern of pulmonary arteries and veins and of the bronchoarterial–bronchovenous diameter ratios. Imaging anatomy was compared with previous published data based on dissection and microscopic anatomy. With the increasing availability of advanced imaging tools for wildlife animal patients, a detailed CT anatomy background is required to decipher correctly the pathologic respiratory conditions of sea turtles. Anat Rec, 302:1658–1665, 2019. © 2018 American Association for Anatomy  相似文献   
12.
Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is an established treatment for high-risk hematological malignancies in the pediatric population, but relapse remains the leading cause of death. We analyzed risk factors associated with relapse.Data from 353 allo-HSCTs from 1989 to 2015 in our center were studied retrospectively. We performed a multivariate analysis of pre- and postransplantation variables and developed a predictive risk score for relapse using the significant factors in this training cohort. The results were confirmed in a validation cohort of 90 allo-HSCTs done in our institution from 2016 to the present.A total of 104 patients relapsed after allo-HSCT, with a relapse cumulative incidence of 31 ± 2%. In multivariate analysis, only 2 variables influenced relapse: disease phase (advanced versus early, HR, 2.84; 95% CI, 1.76 to 4.57; P?=?.001) and presence of chronic graft-versus-host disease (GVHD) (acute GVHD versus chronic GVHD [HR, 4.27; 95% CI, 1.99 to 9.15; P?=?.0001] and no GVHD versus chronic GVHD [HR, 6.86; 95% CI, 3.63 to 12.97] P?=?.0001]. Applying the personalized risk score (0 to 3), the relapse cumulative incidence was 70 ± 5% in patients with a score of 3 (without GVHD and in the advanced phase) compared with 6 ± 4% in patients with a score of 0 (with chronic GVHD and in an early phase). This score has been verified in the validation set. With a median follow-up of 54 months, the disease-free survival (DFS) and overall survival rate were 37 ± 3% and 45 ± 4%, respectively.The association of GVHD with the graft-versus-leukemia effect is clearly established in our study, and the form of GVHD associated with less relapse and the best DFS is the classical form of chronic GVHD according to the National Institutes of Health classification. The proposed relapse risk score was validated in an independent cohort and allows personalization of the prognosis.  相似文献   
13.
14.
Ioana Agache  Isabella Annesi‐Maesano  Andreas Bonertz  Francesco Branca  Andrew Cant  Zlatko Fras  Frank Ingenrieth  Leyla Namazova‐Baranova  Mikaela Odemyr  Antonio Spanevello  Stefan Vieths  Arzu Yorgancioglu  Montserat Alvaro‐Lozano  Domingo Barber Hernandez  Toms Chivato  Stefano Del Giacco  Zuzana Diamant  Ibon Eguiluz‐Gracia  Roy Gert van Wijk  Philippe Gevaert  Anke Graessel  Peter Hellings  Karin Hoffmann‐Sommergruber  Marek Jutel  Susanne Lau  Antti Lauerma  Jose Maria Olaguibel  Liam O'Mahony  Cevdet Ozdemir  Oscar Palomares  Oliver Pfaar  Joaquin Sastre  Glennis Scadding  Carsten Schmidt‐Weber  Peter Schmid‐Grendelmeier  Mohamed Shamji  Isabel Skypala  Monica Spinola  Otto Spranger  Maria Torres  Andrea Vereda  Sergio Bonini 《Allergy》2019,74(11):2064-2076
The European Academy of Allergy and Clinical Immunology (EAACI) organized the first European Strategic Forum on Allergic Diseases and Asthma. The main aim was to bring together all relevant stakeholders and decision‐makers in the field of allergy, asthma and clinical Immunology around an open debate on contemporary challenges and potential solutions for the next decade. The Strategic Forum was an upscaling of the EAACI White Paper aiming to integrate the Academy's output with the perspective offered by EAACI's partners. This collaboration is fundamental for adapting and integrating allergy and asthma care into the context of real‐world problems. The Strategic Forum on Allergic Diseases brought together all partners who have the drive and the influence to make positive change: national and international societies, patients’ organizations, regulatory bodies and industry representatives. An open debate with a special focus on drug development and biomedical engineering, big data and information technology and allergic diseases and asthma in the context of environmental health concluded that connecting science with the transformation of care and a joint agreement between all partners on priorities and needs are essential to ensure a better management of allergic diseases and asthma in the advent of precision medicine together with global access to innovative and affordable diagnostics and therapeutics.  相似文献   
15.
16.
This paper develops and tests a dynamic model of hospital focus. It does so by tracing the performance trajectories of specialist and general hospitals to identify whether a performance gap exists and whether it widens or shrinks over time. Our longitudinal analyses of all hospital organizations within the English National Health Service (NHS) reveal not only a notable performance gap between specialist and general hospitals in particular with regards to patient satisfaction that widens over time, but also the emergence of a gap especially with regards to hospital staff job satisfaction. These findings reflect the considerable potential of specialization as a means to enhance hospital effectiveness. However, they also alert health policy makers to the threat of a widening performance gap between specialist and general hospitals with potential negative repercussions at the patient and health system level.  相似文献   
17.

Background

It is widely recognized that there are multiple risk factors for early-life mortality. In practice most interventions to curb early-life mortality target births based on a single risk factor, such as poverty. However, most premature deaths are not from the targeted group. Thus interventions target many births that are at not at high risk and miss many births at high risk.

Methods

Using data from the second wave of Demographic and Health Surveys from India and a hierarchical Bayesian model, we estimate infant mortality risk for 73.320 infants in India as a function of 4 risk factors. We show how this information can be used to improve program targeting. We compare our novel approach against common programs that target groups based on a single risk factor.

Results

A conventional approach that targets mothers in the lowest quintile of income correctly identifies only 30% of infant deaths. By contrast, using four risk factors simultaneously we identify a group of births of the same size that includes 57% of all deaths. Using the 2012 census to translate these percentages into numbers, there were 25.642.200 births in 2012 and 4.4% died before the age of one. Our approach correctly identifies 643.106 of 1.128.257 infant deaths while poverty only identifies 338.477 infant deaths.

Conclusion

Our approach considerably improves program targeting by identifying more infant deaths than the usual approach that targets births based on a single risk factor. This leads to more efficient program targeting. This is particularly useful in developing countries, where resources are lacking and needs are high.
  相似文献   
18.
The quality of aquatic environments all around the world is being altered by different human activities that represent direct threat to the ecological system and the aquatic biota. This study aimed to evaluate the occurrence of histological and genotoxic alterations in Prochilodus lacustris as indicators of anthropic impacts in a lacustrine environment in northeast Brazil. The histological alterations were evaluated using the histological alteration index, and the genotoxic alterations were detected using the micronuclei test, at three sampling stations (S1, S2 and S3). The gills presented lesions with three stages of severity, with mild lesions more frequent in the specimens collected at station S1. Mild hepatic tissue lesions were the most frequent type in both areas. Micronucleus analysis showed that station S3 was the most affected. The biological responses observed indicated that the fish are under influence of environmental changes. It is important to highlight that the organisms collected at station S3 had a more compromised health status.  相似文献   
19.
Background: Primary stability has a relevant role in the long‐term success of dental implants. A quantitative method for the measurement of implant stability has been introduced (resonance frequency analysis RFA]). Information about the significance of RFA measurements and about the relationship between RFA values and their association with implant osseointegration, success, or failure is important from a clinical point of view. Purpose: The aim of the present histological and histomorphometric study was to see if a correlation existed between the bone‐implant contact (BIC) percentage of retrieved human implants and RFA values. Materials and Methods: Seven implants inserted in the posterior mandible, with a sandblasted and acid‐etched surface and retrieved after a 6‐month period, were evaluated in the present study. These seven implants had been retrieved for different causes. All these implants were submerged and were retrieved with a 5‐mm trephine bur and immersed in 10% buffered formalin to be processed for histology. Results: A statistically significant correlation could be detected between implant stability quotient and BIC (p=.016). Conclusions: Even if the relationship between bone structure and RFA is still not fully understood, in our study, a statistically significant correlation was found between RFA and BIC values. Further studies are needed to evaluate a correlation of RFA and BIC in human implants retrieved after a range of healing periods.  相似文献   
20.
This in vitro study evaluated, using a bacterial leakage model, whether intracanal medication with calcium hydroxide [Ca(OH)2]-based pastes prepared with different vehicles, has inhibitory effect on corono-apical leakage of bacteria. Forty instrumented human canines were dressed with Ca(OH)2 p.a. associated with: G1 = distilled water; G2 = polyethylene glycol (PG); G3 = PG + CMCP; and G4 = glycerin. Five teeth with intact crowns served as negative controls and 5 instrumented teeth without temporary dressing served as positive controls. All teeth were mounted in a 2-chamber apparatus and then exposed to human saliva for 63 days. Leakage was recorded when turbidity was observed in the lower chamber. Fifty percent of the samples of G1 and G2, 10% of G3 and 80% of G4 were fully contaminated after 9 weeks. Statistically significant differences were observed with paired comparisons G3 and G4 (p=0.0069), with G3 achieving better seal against bacterial leakage than G4.  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