全文获取类型
收费全文 | 4193篇 |
免费 | 348篇 |
国内免费 | 6篇 |
专业分类
耳鼻咽喉 | 44篇 |
儿科学 | 104篇 |
妇产科学 | 105篇 |
基础医学 | 491篇 |
口腔科学 | 313篇 |
临床医学 | 518篇 |
内科学 | 986篇 |
皮肤病学 | 28篇 |
神经病学 | 258篇 |
特种医学 | 176篇 |
外科学 | 535篇 |
综合类 | 75篇 |
一般理论 | 2篇 |
预防医学 | 386篇 |
眼科学 | 66篇 |
药学 | 326篇 |
1篇 | |
中国医学 | 3篇 |
肿瘤学 | 130篇 |
出版年
2021年 | 55篇 |
2020年 | 28篇 |
2019年 | 52篇 |
2018年 | 62篇 |
2017年 | 50篇 |
2016年 | 51篇 |
2015年 | 57篇 |
2014年 | 126篇 |
2013年 | 138篇 |
2012年 | 204篇 |
2011年 | 195篇 |
2010年 | 91篇 |
2009年 | 104篇 |
2008年 | 196篇 |
2007年 | 189篇 |
2006年 | 148篇 |
2005年 | 187篇 |
2004年 | 218篇 |
2003年 | 188篇 |
2002年 | 161篇 |
2001年 | 148篇 |
2000年 | 152篇 |
1999年 | 129篇 |
1998年 | 62篇 |
1997年 | 48篇 |
1996年 | 44篇 |
1995年 | 46篇 |
1994年 | 42篇 |
1993年 | 36篇 |
1992年 | 86篇 |
1991年 | 76篇 |
1990年 | 99篇 |
1989年 | 82篇 |
1988年 | 80篇 |
1987年 | 83篇 |
1986年 | 76篇 |
1985年 | 68篇 |
1984年 | 74篇 |
1983年 | 63篇 |
1982年 | 26篇 |
1981年 | 29篇 |
1980年 | 32篇 |
1979年 | 39篇 |
1978年 | 31篇 |
1977年 | 30篇 |
1976年 | 30篇 |
1974年 | 35篇 |
1971年 | 28篇 |
1968年 | 27篇 |
1966年 | 26篇 |
排序方式: 共有4547条查询结果,搜索用时 453 毫秒
61.
4-1BBL(-/-) mice have a defect in recall CD8+ T cell responses to viruses, whereas CD4+ T cell responses to virus are unimpaired in these mice. In contrast, both CD4+ and CD8+ T cells respond to 4-1BB ligand (4-1BBL) in vitro. To clarify the role of 4-1BB/4-1BBL in CD4+ versus CD8+ T cell responses in vivo, we compared CD4 (OT-II) and CD8 (OT-I) TCR transgenic T cells responding to the same antigen in an in vivo adoptive transfer model in 4-1BBL(+/+) versus 4-1BBL(-/-) mice. During primary and secondary responses, expression of 4-1BB on in vivo-activated TCR transgenic T cells was earlier and more transient than previously observed in vitro, correlating with expression of the early activation antigen CD69 and preceding the transition to the CD44hi state. Although 4-1BB is expressed early in the primary response, there was no effect of 4-1BBL deficiency on initial CD8 T cell expansion and only a minor effect on initial CD4 T cell expansion. The major effect of 4-1BB/4-1BBL interaction is on the T cell recall response. This is due to effects of 4-1BBL on maintenance of T cell numbers at the end of the primary response with additional effects of 4-1BBL on secondary expansion of T cells. 相似文献
62.
63.
We report studies on two patients (1 and 2) with Hurler disease. They both had all of the non-neurological features of Hurler disease to a similar and extreme degree and similar signs of brain damage on computed tomography. However, intellectual function was unusually well-preserved in patient 1, but seriously and typically impaired in patient 2. The reason for this discrepancy has been investigated by reference to the neuropathological findings, the results of -l-iduronidase assays using different substrates and comparisons to other cases (patients 3 and 4). We suggest that patient 1 is an unusual variant of the disease who may have had a very low residual -l-iduronidase activity in neuronal cells only, and that this could not be demonstrated by either enzyme assays on whole brain using the 4-methylumbelliferyliduronide substrate (Crowet al., 1983) or in studies on fibroblast lysates using a radioactive disaccharide substrate. 相似文献
64.
G. T. Stevenson V. M. Cole J. Summerton H. F. Watts 《Medical oncology (Northwood, London, England)》1984,1(4):275-278
A more effective use of antibody in treating cancer appears to require derivatives with enhanced cytotoxic potential. Working with anti-idiotype antibodies directed against neoplastic lymphocytes, we have shown previously that univalent antibody derivatives with intact Fc-regions can avoid antigenic modulation while retaining the ability to recruit cytotoxic effectors such as complement. Chimeric univalent antibodies represent an extension of this approach. To prepare them Fab′γ from antibody is linked by thioether bonds to half-cystine in normal Ig of the species to undergo immunotherapy. The derivatives FabIgG and FabFc utilize IgG and Fcγ respectively as the effector partners of the antibody Fab′γ. They appear superior to parent antibody in their ability to invoke complement and K-cell killing of target lymphocytes. They show promise of being minimally immunogenic and, because they present homologous Fc, should prove efficient recruiters of host effector functions. 相似文献
65.
So Yoon Sim Elizabeth Watts Dagna Constenla Shuoning Huang Logan Brenzel Bryan N. Patenaude 《Value in health》2021,24(1):70-77
ObjectivesUnderstanding the level of investment needed for the 2021-2030 decade is important as the global community faces the next strategic period for vaccines and immunization programs. To assist with this goal, we estimated the aggregate costs of immunization programs for ten vaccines in 94 low- and middle-income countries from 2011 to 2030.MethodWe calculated vaccine, immunization delivery and stockpile costs for 94 low- and middle-income countries leveraging the latest available data sources. We conducted scenario analyses to vary assumptions about the relationship between delivery cost and coverage as well as vaccine prices for fully self-financing countries.ResultsThe total aggregate cost of immunization programs in 94 countries for 10 vaccines from 2011 to 2030 is $70.8 billion (confidence interval: $56.6-$93.3) under the base case scenario and $84.1 billion ($72.8-$102.7) under an incremental delivery cost scenario, with an increasing trend over two decades. The relative proportion of vaccine and delivery costs for pneumococcal conjugate, human papillomavirus, and rotavirus vaccines increase as more countries introduce these vaccines. Nine countries in accelerated transition phase bear the highest burden of the costs in the next decade, and uncertainty with vaccine prices for the 17 fully self-financing countries could lead to total costs that are 1.3-13.1 times higher than the base case scenario.ConclusionResource mobilization efforts at the global and country levels will be needed to reach the level of investment needed for the coming decade. Global-level initiatives and targeted strategies for transitioning countries will help ensure the sustainability of immunization programs. 相似文献
66.
M. Rivington R. King D. Duckett P. Iannetta T. G. Benton P.J. Burgess C. Hawes L. Wellesley J. G. Polhill M. Aitkenhead L.‐M. Lozada‐Ellison G. Begg A. G. Williams A. Newton A. Lorenzo‐Arribas R. Neilson C. Watts J. Harris K. Loades D. Stewart D. Wardell‐Johnson G. Gandossi E. Udugbezi J.A. Hannam C. Keay 《Nutrition Bulletin》2021,46(1):88-97
The COVID‐19 pandemic is a major shock to society in terms of health and economy that is affecting both UK and global food and nutrition security. It is adding to the ‘perfect storm’ of threats to society from climate change, biodiversity loss and ecosystem degradation, at a time of considerable change, rising nationalism and breakdown in international collaboration. In the UK, the situation is further complicated due to Brexit. The UK COVID‐19 Food and Nutrition Security project, lasting one year, is funded by the Economic and Social Research Council and is assessing the ongoing impact of COVID‐19 on the four pillars of food and nutrition security: access, availability, utilisation and stability. It examines the food system, how it is responding, and potential knock on effects on the UK’s food and nutrition security, both in terms of the cascading risks from the pandemic and other threats. The study provides an opportunity to place the initial lessons being learnt from the on‐going responses to the pandemic in respect of food and nutrition security in the context of other long‐term challenges such as climate change and biodiversity loss. 相似文献
67.
W K Scott M A Nance R L Watts J P Hubble W C Koller K Lyons R Pahwa M B Stern A Colcher B C Hiner J Jankovic W G Ondo F H Allen C G Goetz G W Small D Masterman F Mastaglia N G Laing J M Stajich B Slotterbeck M W Booze R C Ribble E Rampersaud S G West R A Gibson L T Middleton A D Roses J L Haines B L Scott J M Vance M A Pericak-Vance 《JAMA》2001,286(18):2239-2244
CONTEXT: The relative contribution of genes vs environment in idiopathic Parkinson disease (PD) is controversial. Although genetic studies have identified 2 genes in which mutations cause rare single-gene variants of PD and observational studies have suggested a genetic component, twin studies have suggested that little genetic contribution exists in the common forms of PD. OBJECTIVE: To identify genetic risk factors for idiopathic PD. DESIGN, SETTING, AND PARTICIPANTS: Genetic linkage study conducted 1995-2000 in which a complete genomic screen (n = 344 markers) was performed in 174 families with multiple individuals diagnosed as having idiopathic PD, identified through probands in 13 clinic populations in the continental United States and Australia. A total of 870 family members were studied: 378 diagnosed as having PD, 379 unaffected by PD, and 113 with unclear status. MAIN OUTCOME MEASURES: Logarithm of odds (lod) scores generated from parametric and nonparametric genetic linkage analysis. RESULTS: Two-point parametric maximum parametric lod score (MLOD) and multipoint nonparametric lod score (LOD) linkage analysis detected significant evidence for linkage to 5 distinct chromosomal regions: chromosome 6 in the parkin gene (MLOD = 5.07; LOD = 5.47) in families with at least 1 individual with PD onset at younger than 40 years, chromosomes 17q (MLOD = 2.28; LOD = 2.62), 8p (MLOD = 2.01; LOD = 2.22), and 5q (MLOD = 2.39; LOD = 1.50) overall and in families with late-onset PD, and chromosome 9q (MLOD = 1.52; LOD = 2.59) in families with both levodopa-responsive and levodopa-nonresponsive patients. CONCLUSIONS: Our data suggest that the parkin gene is important in early-onset PD and that multiple genetic factors may be important in the development of idiopathic late-onset PD. 相似文献
68.
Association of single-nucleotide polymorphisms of the tau gene with late-onset Parkinson disease. 总被引:14,自引:1,他引:13
E R Martin W K Scott M A Nance R L Watts J P Hubble W C Koller K Lyons R Pahwa M B Stern A Colcher B C Hiner J Jankovic W G Ondo F H Allen C G Goetz G W Small D Masterman F Mastaglia N G Laing J M Stajich R C Ribble M W Booze A Rogala M A Hauser F Zhang R A Gibson L T Middleton A D Roses J L Haines B L Scott M A Pericak-Vance J M Vance 《JAMA》2001,286(18):2245-2250
CONTEXT: The human tau gene, which promotes assembly of neuronal microtubules, has been associated with several rare neurologic diseases that clinically include parkinsonian features. We recently observed linkage in idiopathic Parkinson disease (PD) to a region on chromosome 17q21 that contains the tau gene. These factors make tau a good candidate for investigation as a susceptibility gene for idiopathic PD, the most common form of the disease. OBJECTIVE: To investigate whether the tau gene is involved in idiopathic PD. DESIGN, SETTING, AND PARTICIPANTS: Among a sample of 1056 individuals from 235 families selected from 13 clinical centers in the United States and Australia and from a family ascertainment core center, we tested 5 single-nucleotide polymorphisms (SNPs) within the tau gene for association with PD, using family-based tests of association. Both affected (n = 426) and unaffected (n = 579) family members were included; 51 individuals had unclear PD status. Analyses were conducted to test individual SNPs and SNP haplotypes within the tau gene. MAIN OUTCOME MEASURE: Family-based tests of association, calculated using asymptotic distributions. RESULTS: Analysis of association between the SNPs and PD yielded significant evidence of association for 3 of the 5 SNPs tested: SNP 3, P =.03; SNP 9i, P =.04; and SNP 11, P =.04. The 2 other SNPs did not show evidence of significant association (SNP 9ii, P =.11, and SNP 9iii, P =.87). Strong evidence of association was found with haplotype analysis, with a positive association with one haplotype (P =.009) and a negative association with another haplotype (P =.007). Substantial linkage disequilibrium (P<.001) was detected between 4 of the 5 SNPs (SNPs 3, 9i, 9ii, and 11). CONCLUSIONS: This integrated approach of genetic linkage and positional association analyses implicates tau as a susceptibility gene for idiopathic PD. 相似文献
69.
70.
B S Gurian E H Baker S Jacobson B Lagerbom P Watts 《Journal of the American Geriatrics Society》1990,38(1):37-44
This paper presents the results of four studies that evaluated the use of neuroleptics in an aging population both in nursing homes and in a psychiatric teaching hospital. The purpose was to determine the degree to which prescribing practices were in compliance with recent court rulings respecting the right of patients to informed consent to "exceptional" medication. The results indicate that physicians in nursing homes do not inform their patients of the risks of neuroleptics, do not seek consent, and do not consider competency to be even an issue. Elderly patients in the acute academic setting were informed of risks and benefits. However, both consent to medication and the competency to give this consent were presumed until or unless the patient failed to acquiesce. The degree to which these practices might be in potential conflict with state law, ignore the benefits of a negotiated doctor/patient partnership, and demonstrate one aspect of poor quality of care are discussed, and policy recommendations are made. 相似文献