全文获取类型
收费全文 | 689篇 |
免费 | 66篇 |
专业分类
755篇 |
出版年
2023年 | 16篇 |
2022年 | 22篇 |
2021年 | 46篇 |
2020年 | 19篇 |
2019年 | 23篇 |
2018年 | 24篇 |
2017年 | 21篇 |
2016年 | 30篇 |
2015年 | 61篇 |
2014年 | 54篇 |
2013年 | 47篇 |
2012年 | 71篇 |
2011年 | 50篇 |
2010年 | 27篇 |
2009年 | 31篇 |
2008年 | 28篇 |
2007年 | 28篇 |
2006年 | 24篇 |
2005年 | 12篇 |
2004年 | 17篇 |
2003年 | 18篇 |
2002年 | 15篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1992年 | 3篇 |
1980年 | 2篇 |
1976年 | 2篇 |
1968年 | 5篇 |
1967年 | 2篇 |
1958年 | 1篇 |
1957年 | 1篇 |
1955年 | 1篇 |
1954年 | 1篇 |
1949年 | 1篇 |
1948年 | 1篇 |
1939年 | 1篇 |
1936年 | 1篇 |
1934年 | 1篇 |
1933年 | 1篇 |
1932年 | 2篇 |
1929年 | 2篇 |
1928年 | 1篇 |
1926年 | 1篇 |
1924年 | 1篇 |
1922年 | 1篇 |
1911年 | 3篇 |
排序方式: 共有755条查询结果,搜索用时 10 毫秒
11.
12.
13.
The Drosophila melanogaster genes zerknüllt (zen) and fushi tarazu (ftz) are members of the Hox gene family whose roles have changed significantly in the insect lineage and thus provide an opportunity to study the mechanisms
underlying the functional evolution of Hox proteins. We have studied the expression of orthologs of zen (DpuHox3) and ftz (Dpuftz) in the crustacean Daphnia pulex (Branchiopoda), both of which show a dynamic expression pattern. DpuHox3 is expressed in a complex pattern in early embryogenesis, with the most anterior boundary of expression lying at the anterior
limit of the second antennal segment as well as a ring of expression around the embryo. In later embryos, DpuHox3 expression is restricted to the mesoderm of mandibular limb buds. Dpuftz is first expressed in a ring around the embryo following the posterior limit of the mandibular segment. Later, Dpuftz is restricted to the posterior part of the mandibular segment. This is the first report of expression of a Hox3 ortholog in a crustacean, and together with Dpuftz data, the results presented here show that Hox3 and ftz have retained a Hox-like expression pattern in crustaceans. This is in accordance with the proposed model of Hox3 and ftz evolution in arthropods and allows a more precise pinpointing of the loss of ftz “Hox-like behaviour”: in the lineage between the Branchiopoda and the basal insect Thysanura. 相似文献
14.
Mechtcheriakova D Wlachos A Sobanov J Kopp T Reuschel R Bornancin F Cai R Zemann B Urtz N Stingl G Zlabinger G Woisetschläger M Baumruker T Billich A 《Cellular signalling》2007,19(4):748-760
Sphingosine 1-phosphate (S1P) levels in cells and, consequently, its bioactivity as a signalling molecule are controlled by the action of enzymes responsible for its synthesis and degradation. In the present report, we examined alterations in expression patterns of enzymes involved in S1P-metabolism (sphingosine kinases including their splice variants, sphingosine 1-phosphate phosphatases, and sphingosine 1-phosphate lyase) under certain inflammatory conditions. We found that sphingosine kinase type 1 (SPHK1) mRNA could be triggered in a cell type-specific manner; individual SPHK1 splice variants were induced with similar kinetics. Remarkably, expression and activity of S1P phosphatase 2 (SPP2) was found to be highly upregulated by inflammatory stimuli in a variety of cells (e.g., neutrophils, endothelial cells). Bandshift analysis using oligonucleotides spanning predicted NFkappaB sites within the SPP2 promoter and silencing of NFkappaB/RelA via RelA-directed siRNA demonstrated that SPP2 is an NFkappaB-dependent gene. Silencing of SPP2 expression in endothelial cells, in turn, led to a marked reduction of TNF-alpha-induced IL-1beta mRNA and protein and to a partial reduction of induced IL-8, suggesting a pro-inflammatory role of SPP2. Notably, up-regulation of SPP2 was detected in samples of lesional skin of patients with psoriasis, an inflammatory skin disease. This study provides detailed insights into the regulation of SPP2 gene expression and suggests that SPP2 might be a novel player in pro-inflammatory signalling. 相似文献
15.
Karl -Ernst Kaissling Maximilian Renner 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1968,59(4):357-361
Zusammenfassung Auf den Antennen aller drei Kasten von Apis mellifica konnten elektrophysiologisch 2 Typen von Riechzellen identifiziert werden, die auf Pheromone der Biene antworten. Der eine Typ ist auf Queen substance (9-Oxo-trans-2-decensäure), der andere auf den Sterzelduft der Arbeiterin spezialisiert. Beide Zelltypen werden bei Ableitungen von Porenplatten gefunden.
Antennal receptors for queen substance and scent gland odour in honeybees
Summary Electrophysiologically, we could identify two types of olfactory receptor cells, which respond to pheromones of the honeybee. These cells are associated with the poreplates on the antennae of all three castes of Apis mellifica. One of the cell types is specialized for the queen substance (9-oxo-trans-2-decenoic acid) while the other responds to the scent of the Nasanov gland.相似文献
16.
Eichinger Jonas F. Grill Maximilian J. Kermani Iman Davoodi Aydin Roland C. Wall Wolfgang A. Humphrey Jay D. Cyron Christian J. 《Biomechanics and modeling in mechanobiology》2021,20(5):1851-1870
Biomechanics and Modeling in Mechanobiology - Living soft tissues appear to promote the development and maintenance of a preferred mechanical state within a defined tolerance around a so-called set... 相似文献
17.
Caio Cesar de Souza Alves Adam Collison Luke Hatchwell Maximilian Plank Matthew Morten Paul S. Foster Sebastian L. Johnston Cristiane Fran?a da Costa Mauro Vieira de Almeida Henrique Couto Teixeira Ana Paula Ferreira Joerg Mattes 《PloS one》2013,8(11)
Background
Severe asthma is associated with T helper (TH) 2 and 17 cell activation, airway neutrophilia and phosphoinositide-3-kinase (PI3K) activation. Asthma exacerbations are commonly caused by rhinovirus (RV) and also associated with PI3K-driven inflammation. Anthraquinone derivatives have been shown to reduce PI3K-mediated AKT phosphorylation in-vitro.Objective
To determine the anti-inflammatory potential of anthraquinones in-vivo.Methods
BALB/c mice were sensitized and challenged with crude house dust mite extract to induce allergic airways disease and treated with mitoxantrone and a novel non-cytotoxic anthraquinone derivative. Allergic mice were also infected with RV1B to induce an exacerbation.Results
Anthraquinone treatment reduced AKT phosphorylation, hypoxia-inducible factor-1α and vascular endothelial growth factor expression, and ameliorated allergen- and RV-induced airways hyprereactivity, neutrophilic and eosinophilic inflammation, cytokine/chemokine expression, mucus hypersecretion, and expression of TH2 proteins in the airways. Anthraquinones also boosted type 1 interferon responses and limited RV replication in the lung.Conclusion
Non-cytotoxic anthraquinone derivatives may be of therapeutic benefit for the treatment of severe and RV-induced asthma by blocking pro-inflammatory pathways regulated by PI3K/AKT. 相似文献18.
19.
20.
Felix Roosen-Runge Marcus Hennig Tilo Seydel Fajun Zhang Maximilian W.A. Skoda Stefan Zorn Robert M.J. Jacobs Marco Maccarini Peter Fouquet Frank Schreiber 《Biochimica et Biophysica Acta - Proteins and Proteomics》2010,1804(1):68-75
We report on a combined cold neutron backscattering and spin-echo study of the short-range and long-range nanosecond diffusion of the model globular protein bovine serum albumin (BSA) in aqueous solution as a function of protein concentration and NaCl salt concentration. Complementary small angle X-ray scattering data are used to obtain information on the correlations of the proteins in solution. Particular emphasis is put on the effect of crowding, i.e. conditions under which the proteins cannot be considered as objects independent of each other. We thus address the question at which concentration this crowding starts to influence the static and in particular also the dynamical behaviour. We also briefly discuss qualitatively which charge effects, i.e. effects due to the interplay of charged molecules in an electrolyte solution, may be anticipated. Both the issue of crowding as well as that of charge effects are particularly relevant for proteins and their function under physiological conditions, where the protein volume fraction can be up to approximately 40% and salt ions are ubiquitous. The interpretation of the data is put in the context of existing studies on related systems and of existing theoretical models. 相似文献