全文获取类型
收费全文 | 1707篇 |
免费 | 93篇 |
国内免费 | 8篇 |
专业分类
耳鼻咽喉 | 14篇 |
儿科学 | 49篇 |
妇产科学 | 50篇 |
基础医学 | 339篇 |
口腔科学 | 38篇 |
临床医学 | 190篇 |
内科学 | 315篇 |
皮肤病学 | 29篇 |
神经病学 | 122篇 |
特种医学 | 57篇 |
外科学 | 278篇 |
综合类 | 14篇 |
预防医学 | 111篇 |
眼科学 | 8篇 |
药学 | 129篇 |
中国医学 | 2篇 |
肿瘤学 | 63篇 |
出版年
2023年 | 8篇 |
2022年 | 20篇 |
2021年 | 28篇 |
2020年 | 18篇 |
2019年 | 22篇 |
2018年 | 23篇 |
2017年 | 28篇 |
2016年 | 31篇 |
2015年 | 38篇 |
2014年 | 33篇 |
2013年 | 60篇 |
2012年 | 102篇 |
2011年 | 79篇 |
2010年 | 60篇 |
2009年 | 59篇 |
2008年 | 102篇 |
2007年 | 105篇 |
2006年 | 125篇 |
2005年 | 113篇 |
2004年 | 113篇 |
2003年 | 85篇 |
2002年 | 103篇 |
2001年 | 19篇 |
2000年 | 10篇 |
1999年 | 18篇 |
1998年 | 25篇 |
1997年 | 15篇 |
1996年 | 27篇 |
1995年 | 13篇 |
1994年 | 18篇 |
1993年 | 14篇 |
1992年 | 8篇 |
1991年 | 12篇 |
1990年 | 9篇 |
1989年 | 8篇 |
1987年 | 12篇 |
1986年 | 7篇 |
1985年 | 8篇 |
1984年 | 11篇 |
1983年 | 7篇 |
1981年 | 7篇 |
1980年 | 11篇 |
1937年 | 9篇 |
1930年 | 6篇 |
1929年 | 7篇 |
1928年 | 11篇 |
1926年 | 8篇 |
1925年 | 7篇 |
1923年 | 6篇 |
1922年 | 6篇 |
排序方式: 共有1808条查询结果,搜索用时 15 毫秒
51.
Stefan Polenz Willy Kunz Benjamin Braun Andrea Franke Elena Lpez Frank Brückner Christoph Leyens 《Materials》2021,14(12)
Ceramic matrix composites (CMCs) are refractory ceramic materials with damage-tolerant behavior. Coming from the space industry, this class of materials is increasingly being used in other applications, such as automotive construction for high-performance brake discs, furnace technology, heat coatings for pipe systems and landing flaps on reusable rocket sections. In order to produce CMC faster and more cost-efficiently for the increasing demand, a new additive manufacturing process is being tested, which in the future should also be able to realize material joints and higher component wall thicknesses than conventional processes. The main features of the process are as follows. A ceramic fiber bundle is de-sized and infiltrated with ceramic suspension. The bundle infiltrated with matrix material is dried and then applied to a body form. During application, the matrix material is melted by laser radiation without damaging the fiber material. For the initial validation of the material system, samples are pressed and analyzed for their absorption properties using integrating sphere measurement. With the results, a suitable processing laser is selected, and initial melting tests of the matrix system are carried out. After the first validation of the process, a test system is set up, and the first test specimens are produced to determine the material parameters. 相似文献
52.
Summary Menadione and NH4Cl were reported to lower the islet content of reduced pyridine nucleotides. They were used to investigate the possible significance
of NAD(P)H in the regulation of glucagon release by glucose and arginine. Menadione (10–25 μmol/l) enhanced arginine-stimulated
glucagon release at a low glucose concentration (3.3 mmol/l), but failed both to affect glucagon secretion in the sole presence
of glucose (3.3 mmol/l) and to suppress the inhibitory action of glucose 11.1 mmol/l upon glucagon output. In contrast to
menadione, NH4Cl inhibited arginine-stimulated glucagon release at the low glucose concentration. The inhibitory action of glucose in high
concentration upon glucagon release was not suppressed by NH4Cl. These findings do not permit to extrapolate to the A2-cell the concept that reduced pyridine nucleotides represent a major coupling factor in the nutritional regulation of hormonal
release. 相似文献
53.
Generation of CD8 suppressor factor and β chemokines, induced by xenogeneic immunization, in the prevention of simian immunodeficiency virus infection in macaques 下载免费PDF全文
Yufei Wang Louisa Tao Elaine Mitchell Willy M. J. M. Bogers Carl Doyle Christopher A. Bravery Lesley A. Bergmeier Charles G. Kelly Jonathan L. Heeney Thomas Lehner 《Proceedings of the National Academy of Sciences of the United States of America》1998,95(9):5223-5228
Previous xenogeneic immunization experiments in rhesus macaques with simian immunodeficiency virus (SIV) grown in human CD4+ T cells consistently elicited protection from challenge with live SIV. However, the mechanism of protection has not been established. We present evidence that xenogeneic immunization induced significant CD8 suppressor factor, RANTES (regulated upon activation, normal T cell expressed and secreted), macrophage inflammatory protein (MIP) 1α, and MIP-1β (P < 0.001 - P < 0.02). The concentrations of these increased significantly in protected as compared with infected macaques (P < 0.001). Xenogeneic stimulation in vitro also up-regulated CD8 suppressor factors (SF; P < 0.001) and the β chemokines which were neutralized by antibodies to the 3 β chemokines. Recombinant human RANTES, MIP-1α and MIP-1β which bind to simian CCR5, suppressed SIV replication in a dose-dependent manner, with RANTES being more effective than the other two chemokines. The results suggest that immunization with SIV grown in human CD4+ T cells induces CD8-suppressor factor, RANTES, MIP-1α and MIP-1β which may block CCR5 receptors and prevent the virus from binding and fusion to CD4+ cells. 相似文献
54.
An open-label assessment of TMC 125--a new, next-generation NNRTI, for 7 days in HIV-1 infected individuals with NNRTI resistance 总被引:3,自引:0,他引:3
55.
A murine model of minor histocompatibility antigen (miHCag)-mismatched bone marrow transplantation (BMT) was used to study the development of immunoregulatory cells in the posttransplantation period and their possible involvement in the dissociated graft-versus-host (GVH) and graft-versus-leukemia (GVL) reactivity of posttransplantation donor lymphocyte infusions (DLIs). DLI, applied immediately after BMT, induced GVH disease (GVHD), but when DLI was delayed for 3 weeks, GVHD was avoided while a distinct GVL response was allowed to develop. A population of Mac1+Ly6-G+Ly6-C+ immature myeloid cells, found in small numbers in normal mice, strongly expanded in spleens of chimeras, reaching a maximum level at week 3 and returning to base level by week 12. Upon isolation, these cells exhibited interferon-gamma (IFN-gamma)-dependent, nitric oxide (NO)-mediated suppressor activity toward in vitro alloresponses, suggesting that, after in vivo DLI, they are activated by IFN-gamma to produce NO and suppress GVH reactivity. Because not only alloactivated T-cell proliferation but also leukemia cell growth was found susceptible to inhibition by exogenous NO, in vivo activation of these cells after DLI may explain the occurrence of a GVL effect despite suppression of GVHD. This suggested sequence of events was supported by the finding that the ex vivo antihost proliferative response of spleen cells, recovered shortly after in vivo DLI, was characterized by strong mRNA production of the monokines interleukin-1 (IL-1), IL-6, and tumor necrosis factor-alpha (TNF-alpha) and of inducible nitric oxide synthase (iNOS). Our data suggest that transiently expanding Mac1+Ly6-G+Ly6-C+ immature myeloid cells (probably as a result of extramedullary myelopoiesis) may play a role in controlling GVH while promoting GVL reactivity of DLI after allogeneic BMT. 相似文献
56.
Kevin Willy Gerrit Frommeyer Dirk G. Dechering Kristina Wasmer Dennis Höwel Sarah S. Welle Nils Bögeholz Christian Ellermann Julian Wolfes Benjamin Rath Patrick R. Leitz Julia Köbe Philipp S. Lange Patrick Müller Florian Reinke Lars Eckardt 《Clinical cardiology》2020,43(12):1423-1427
BackgroundAblation emerged as first line therapy in the treatment of various arrhythmias. Nevertheless, in older patients (pts), decision is often made pro drug treatment as more complications and less benefit are suspected.HypothesisWe hypothesized that different kind of ablations can be performed safely regardless of the pts age.MethodsWe enrolled all pts aged >80 years (yrs) who underwent ablation for three different arrhythmias (atrial flutter [AFL], atrioventricular nodal re‐entry tachycardia [AVNRT], ventricular tachycardia [VT]) between August 2002 and December 2018. Procedural data and outcome were compared with matched groups aged 60 to 80 years and 40 to 60 years, respectively. Periprocedural and in‐hospital complications were analyzed.ResultsThe analysis included 1191 patients (397 pts per group: 63% AFL, 23% AVNRT, 14% VT) who underwent ablation. Acute success was high in all types of arrhythmias irrespective of age (>80, 60‐80, 40‐60 years: AFL 97%/98%/98%, AVNRT 97%/95%/97%, VT 82%/86%/93%). Rate of periprocedural complications were similar in all groups treated for AFL and AVNRT. For VT ablations significant differences were noted between pts > 80 or 60 to 80 years and those aged 40‐60 years (16.1%/14.3%/3.6%). Most complications were infections and groin haematoma. No strokes, iatrogenic atrioventricular blocks and deaths related to the ablation occurred.ConclusionAblation appears safe in pts > 80 years. Success rates were comparable to matched younger cohorts. A significant difference was observed for VT patients. 相似文献
57.
58.
59.
Mark P. Mattson David B. Allison Luigi Fontana Michelle Harvie Valter D. Longo Willy J. Malaisse Michael Mosley Lucia Notterpek Eric Ravussin Frank A. J. L. Scheer Thomas N. Seyfried Krista A. Varady Satchidananda Panda 《Proceedings of the National Academy of Sciences of the United States of America》2014,111(47):16647-16653
Although major research efforts have focused on how specific components of foodstuffs affect health, relatively little is known about a more fundamental aspect of diet, the frequency and circadian timing of meals, and potential benefits of intermittent periods with no or very low energy intakes. The most common eating pattern in modern societies, three meals plus snacks every day, is abnormal from an evolutionary perspective. Emerging findings from studies of animal models and human subjects suggest that intermittent energy restriction periods of as little as 16 h can improve health indicators and counteract disease processes. The mechanisms involve a metabolic shift to fat metabolism and ketone production, and stimulation of adaptive cellular stress responses that prevent and repair molecular damage. As data on the optimal frequency and timing of meals crystalizes, it will be critical to develop strategies to incorporate those eating patterns into health care policy and practice, and the lifestyles of the population. 相似文献