全文获取类型
收费全文 | 20685篇 |
免费 | 1655篇 |
国内免费 | 46篇 |
专业分类
耳鼻咽喉 | 153篇 |
儿科学 | 766篇 |
妇产科学 | 604篇 |
基础医学 | 2627篇 |
口腔科学 | 342篇 |
临床医学 | 2948篇 |
内科学 | 3848篇 |
皮肤病学 | 309篇 |
神经病学 | 1979篇 |
特种医学 | 429篇 |
外国民族医学 | 2篇 |
外科学 | 2140篇 |
综合类 | 360篇 |
一般理论 | 26篇 |
预防医学 | 2870篇 |
眼科学 | 319篇 |
药学 | 1297篇 |
1篇 | |
中国医学 | 35篇 |
肿瘤学 | 1331篇 |
出版年
2023年 | 187篇 |
2022年 | 267篇 |
2021年 | 570篇 |
2020年 | 338篇 |
2019年 | 642篇 |
2018年 | 723篇 |
2017年 | 470篇 |
2016年 | 551篇 |
2015年 | 593篇 |
2014年 | 768篇 |
2013年 | 1040篇 |
2012年 | 1554篇 |
2011年 | 1558篇 |
2010年 | 806篇 |
2009年 | 700篇 |
2008年 | 1245篇 |
2007年 | 1339篇 |
2006年 | 1267篇 |
2005年 | 1165篇 |
2004年 | 1079篇 |
2003年 | 986篇 |
2002年 | 923篇 |
2001年 | 300篇 |
2000年 | 266篇 |
1999年 | 280篇 |
1998年 | 186篇 |
1997年 | 148篇 |
1996年 | 127篇 |
1995年 | 124篇 |
1994年 | 117篇 |
1993年 | 105篇 |
1992年 | 200篇 |
1991年 | 194篇 |
1990年 | 153篇 |
1989年 | 154篇 |
1988年 | 143篇 |
1987年 | 130篇 |
1986年 | 145篇 |
1985年 | 92篇 |
1984年 | 77篇 |
1983年 | 73篇 |
1982年 | 42篇 |
1981年 | 53篇 |
1980年 | 33篇 |
1979年 | 65篇 |
1977年 | 30篇 |
1976年 | 30篇 |
1974年 | 29篇 |
1973年 | 42篇 |
1969年 | 30篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
42.
Martin F. Ward Angie Titchen Clare Morrell Brendan McCormack Alison Kitson 《Journal of clinical nursing》1998,7(1):29-36
? The paper describes a multiproject practice development programme undertaken over a period of 1 year. ? The background and development of the programme are outlined, whilst attention is paid to the innovatory nature of the work, particularly the use of inductive, deductive and integrated approaches to both change implementation and project supervision. ? The programme was monitored throughout using different data sources and the paper uses evaluative material retrospectively to provide answers to organizational and professional difficulties which arose during the course of the programme. ? The authors conclude that the use of combinations of different models for practice development has potential, but requires careful supervision. ? They also recommend that those involved in practice development are made fully aware of its local or micropolitics, and develop strategies to deal with change before it occurs, not after it has taken place. 相似文献
43.
Day cases: what are we counting? 总被引:1,自引:0,他引:1
44.
Walter G. Sannita Luisa Lopez Lino Maggi Guido Rosadini 《Documenta ophthalmologica. Advances in ophthalmology》1988,70(1):89-96
L-acetylcarnitine is a compound with cholinergic properties and putative action on the visual system and the glucose metabolism. Ten healthy, emmertropic volunteers (age range: 21 to 28 years) were studied. Each subject was administered 5, 10, and 30 mg/kg acute intravenous doses of L-acetylcarnitine and matching placebo. Retinal oscillatory potentials to full-field flash stimulation were recorded before and 30, 60, and 120 min after administration. A systematic reduction of the implicit time of the P2 and N2 oscillatory potential components was observed after administration of the 10 and 30 mg/kg doses: significant changes were not evident at the 5 mg dose or after placebo. The latency reduction was significantly correlated with the postdrug increment of the L-acetylcarnitine plasma concentration. No other systematic modification in latency of amplitude was observed.The results were presented in part at the XXV I.S.C.E.V. Symposium, Sarasota (Florida), April 26–30, 1987. 相似文献
45.
Gregor McWalter MA MSc Hugh Toner MA DipCouns MSc CPsychol Alison Corser BSc MPhil CPsychol Jenny Eastwood MBChB DipSocMed FRCPsych Mary Marshall MA DSA DASS Tony Turvey BSc MAppSci CPsychol 《Health & social care in the community》1994,2(4):213-219
The concept of need and the practice of needs assessment are both subject to a wide range of interpretations, to the likely detriment of individual assessments and to multidisciplinary working. Clear definition is important for individual assessment, for the development of multidisciplinary tools and in gathering planning information. The concept of need is clarified, firstly by distinguishing between need and the difficulties that engender it, and secondly through a taxonomy of need. These assist clear definitions of both need and needs assessment when linked with a consideration of the current help a person receives and a specification of the type of help required by a person to meet their needs. Such definitions have implications for the role of needs assessment in individual assessment, service evaluation, service management and planning and in the development of multidisciplinary needs assessment tools. 相似文献
46.
47.
48.
Leeta Alison Green Khoi Nguyen Bijan Berenji Meera Iyer Eileen Bauer Jorge R Barrio Mohammad Namavari Nagichettiar Satyamurthy Sanjiv S Gambhir 《Journal of nuclear medicine》2004,45(9):1560-1570
Reporter probe 9-(4-18F-fluoro-3-[hydroxymethyl]butyl)guanine (18F-FHBG) and reporter gene mutant herpes simplex virus type 1 thymidine kinase (HSV1-sr39tk) have been used for imaging reporter gene expression with PET. Current methods for quantitating the images using the percentage injected dose per gram of tissue do not distinguish between the effects of probe transport and subsequent phosphorylation. We therefore investigated tracer kinetic models for 18F-FHBG dynamic microPET data and noninvasive methods for determining blood time-activity curves in an adenoviral gene delivery model in mice. METHODS: 18F-FHBG (approximately 7.4 MBq [approximately 200 microCi]) was injected into 4 mice; 18F-FHBG concentrations in plasma and whole blood were measured from mouse heart left ventricle (LV) direct sampling. Replication-incompetent adenovirus (0-2 x 10(9) plaque-forming units) with the E1 region deleted (n = 8) or replaced by HSV1-sr39tk (n = 18) was tail-vein injected into mice. Mice were dynamically scanned using microPET (approximately 7.4 MBq [approximately 200 microCi] 18F-FHBG) over 1 h; regions of interest were drawn on images of the heart and liver. Serial whole blood 18F-FHBG concentrations were measured in 6 of the mice by LV sampling, and 1 least-squares ratio of the heart image to the LV time-activity curve was calculated for all 6 mice. For 2 control mice and 9 mice expressing HSV1-sr39tk, heart image (input function) and liver image time-activity curves (tissue curves) were fit to 2- and 3-compartment models using Levenberg-Marquardt nonlinear regression. The models were compared using an F statistic. HSV1-sr39TK enzyme activity was determined from liver samples and compared with model parameter estimates. For another 3 control mice and 6 HSV1-sr39TK-positive mice, the model-predicted relative percentage of metabolites was compared with high-performance liquid chromatography analysis. RESULTS: The ratio of 18F-FHBG in plasma to whole blood was 0.84 +/- 0.05 (mean +/- SE) by 30 s after injection. The least-squares ratio of the heart image time-activity curve to the LV time-activity curve was 0.83 +/- 0.02, consistent with the recovery coefficient for the partial-volume effect (0.81) based on independent measures of heart geometry. A 3-compartment model best described 18F-FHBG kinetics in mice expressing HSV1-sr39tk in the liver; a 2-compartment model best described the kinetics in control mice. The 3-compartment model parameter, k3, correlated well with the HSV1-sr39TK enzyme activity (r2 = 0.88). CONCLUSION: 18F-FHBG equilibrates rapidly between plasma and whole blood in mice. Heart image time-activity curves corrected for partial-volume effects well approximate LV time-activity curves and can be used as input functions for 2- and 3-compartment models. The model parameter k3 from the 3-compartment model can be used as a noninvasive estimate for HSV1-sr39TK reporter protein activity and can predict the relative percentage of metabolites. 相似文献
49.
Sabine Maguire Bruce Hunter Lindsay Hunter Jo Richard Sibert Mala Mann Alison Mary Kemp 《Archives of disease in childhood》2007,92(12):1113-1117
INTRODUCTION: A torn labial frenum is widely regarded as pathognomonic of abuse. METHODS: We systematically reviewed the evidence for this, and to define other intra-oral injuries found in physical abuse. Nine studies documented abusive torn labial frena in 27 children and 24 [corrected] were fatally abused: 22 were less than 5 years old. Only a direct blow to the face was substantiated as a mechanism of injury. RESULTS: Two studies noted accidentally torn labial frena, both from intubation. Abusive intra-oral injuries were widely distributed to the lips, gums, tongue and palate and included fractures, intrusion and extraction of the dentition, bites and contusions. CONCLUSIONS: Current literature does not support the diagnosis of abuse based on a torn labial frenum in isolation. The intra-oral hard and soft tissue should be examined in all suspected abuse cases, and a dental opinion sought where abnormalities are found. 相似文献
50.
Five strains of infectious bronchitis virus isolated from commercial chickens from the state of Pennsylvania, USA during the years 1998 and 1999 were studied. The strains were selected for cross-challenge in specific pathogen free chickens and virus neutralization in chick embryos on the basis of partial S1 sequence amino acid identity values. The partial sequences analysed spanned the hypervariable amino terminus region of S1 from amino acid residues 48 to 219, based on the Beaudette strain. Using their S1 identity values, the strains represented a continuum of genetic, and thus antigenic, relationships. When compared with strain PA/5083/99, strain PA/Wolgemuth/98 had high sequence identity (96%) followed by PA/171/99 (85%), PA/5344/98 (70%) and PA/1220/98 (34%). The method of Archetti and Horsfall was used for calculating antigenic relatedness values of virus neutralization tests. The same formula was also applied to the percentage protection values of cross-challenge tests to derive protective relatedness values among the strains. The antigenic relatedness values, protective relatedness values, and the partial S1 sequence identity values were then analysed. The findings indicated partial S1 sequence identity values were more strongly correlated with protective relatedness values and than antigenic relatedness values. 相似文献