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   575篇
  免费   38篇
  2023年   4篇
  2022年   9篇
  2021年   25篇
  2020年   19篇
  2019年   20篇
  2018年   17篇
  2017年   12篇
  2016年   23篇
  2015年   38篇
  2014年   42篇
  2013年   46篇
  2012年   54篇
  2011年   49篇
  2010年   28篇
  2009年   33篇
  2008年   31篇
  2007年   33篇
  2006年   35篇
  2005年   23篇
  2004年   23篇
  2003年   15篇
  2002年   14篇
  2001年   5篇
  2000年   3篇
  1999年   3篇
  1998年   2篇
  1995年   1篇
  1993年   1篇
  1987年   1篇
  1978年   1篇
  1969年   1篇
  1965年   1篇
  1939年   1篇
排序方式: 共有613条查询结果,搜索用时 140 毫秒
571.
The vascular disrupting agent combretastatin A-4 disodium phosphate (CA4P) induces fluctuations in peripheral blood neutrophil concentration. Because neutrophils have the potential to induce both vascular damage and angiogenesis we analyzed neutrophil involvement in the anti-tumoral effects of CA4P in C3H mammary carcinomas in CDF1 mice and in SCCVII squamous cell carcinomas in C3H/HeN mice. Flow cytometry analyses of peripheral blood before and up to 144 h after CA4P administration (25 and 250 mg/kg) revealed a decrease 1 h after treatment, followed by an early (3–6 h) and a late (>72 h) increase in the granulocyte concentration. We suggest that the early increase (3–6 h) in granulocyte concentration was caused by the initial decrease at 1 h and found that the late increase was associated with tumor size, and hence independent of CA4P. No alterations in neutrophil infiltration into the C3H tumor after CA4P treatment (25 and 250 mg/kg) were found. Correspondingly, neutrophil depletion in vivo, using an anti-neutrophil antibody, followed by CA4P treatment (25 mg/kg) did not increase the necrotic fraction in C3H tumors significantly. However, by increasing the CA4P dose to 250 mg/kg we found a significant increase of 359% in necrotic fraction when compared to neutrophil-depleted mice; in mice with no neutrophil depletion CA4P induced an 89% change indicating that the presence of neutrophils reduced the effect of CA4P. In contrast, neither CA4P nor 1A8 affected the necrotic fraction in the SCCVII tumors significantly. Hence, we suggest that the initial decrease in granulocyte concentration was caused by non-tumor-specific recruitment of neutrophils and that neutrophils may attenuate CA4P-mediated anti-tumor effect in some tumor models.  相似文献   
572.
Listeria monocytogenes is a gram‐positive facultative intracellular bacterium, which replicates in the cytoplasm of myeloid cells. Interferon β (IFNβ) has been reported to play an important role in the mechanisms underlying Listeria disease. Although studies in murine cells have proposed the bacteria‐derived cyclic‐di‐AMP to be the key bacterial immunostimulatory molecule, the mechanism for IFNβ expression during L. monocytogenes infection in human myeloid cells remains unknown. Here we report that in human macrophages, Listeria DNA rather than cyclic‐di‐AMP is stimulating the IFN response via a pathway dependent on the DNA sensors IFI16 and cGAS as well as the signalling adaptor molecule STING. Thus, Listeria DNA is a major trigger of IFNβ expression in human myeloid cells and is sensed to activate a pathway dependent on IFI16, cGAS and STING.  相似文献   
573.
Multiple myeloma (MM) is characterized by a malignant proliferation of plasma cells in the bone marrow with associated organ damage. Although the prognosis of MM has improved recently, the disease remains incurable for the large majority of patients. The eradication of residual disease in the bone marrow is a main target on the road toward cure. Immune cells play a role in the control of cancer and can be tools to attack residual MM cells. However, the myeloma-associated immune deficiency is a major hurdle to immunotherapy. We evaluated ex vivo the effects of low doses of the immunomodulatory drugs (IMiDs) lenalidomide and pomalidomide on several immune cell types from MM patients after autologous stem cell transplantation and with low tumor burden. We observed that these drugs increased CD4+ and CD8+ T-cell proliferation and cytokine production, enhanced the lytic capacity of cytotoxic T lymphocytes and reduced the suppressive effects of regulatory T cells on CD8+ T-cell responses. In addition, we found that functional dendritic cells (DCs) can be generated from mononuclear cells from MM patients. The presence of IMiDs improved the quality of antigen-specific T cells induced or expanded by these DCs as evidenced by a higher degree of T-cell polyfunctionality. Our results provide a rationale for the design of early phase clinical studies to assess the efficacy of DC-based immunotherapy in combination with posttransplant maintenance treatment with IMiDs in MM.  相似文献   
574.
Subgraph matching algorithms are used to find and enumerate specific interconnection structures in networks. By enumerating these specific structures/subgraphs, the fundamental properties of the network can be derived. More specifically in biological networks, subgraph matching algorithms are used to discover network motifs, specific patterns occurring more often than expected by chance. Finding these network motifs yields information on the underlying biological relations modelled by the network. In this work, we present the Index-based Subgraph Matching Algorithm with General Symmetries (ISMAGS), an improved version of the Index-based Subgraph Matching Algorithm (ISMA). ISMA quickly finds all instances of a predefined motif in a network by intelligently exploring the search space and taking into account easily identifiable symmetric structures. However, more complex symmetries (possibly involving switching multiple nodes) are not taken into account, resulting in superfluous output. ISMAGS overcomes this problem by using a customised symmetry analysis phase to detect all symmetric structures in the network motif subgraphs. These structures are then converted to symmetry-breaking constraints used to prune the search space and speed up calculations. The performance of the algorithm was tested on several types of networks (biological, social and computer networks) for various subgraphs with a varying degree of symmetry. For subgraphs with complex (multi-node) symmetric structures, high speed-up factors are obtained as the search space is pruned by the symmetry-breaking constraints. For subgraphs with no or simple symmetric structures, ISMAGS still reduces computation times by optimising set operations. Moreover, the calculated list of subgraph instances is minimal as it contains no instances that differ by only a subgraph symmetry. An implementation of the algorithm is freely available at https://github.com/mhoubraken/ISMAGS.  相似文献   
575.

Introduction and Aim

The association between thyroid dysfunction and mortality is controversial. Moreover, the impact of duration of thyroid dysfunction is unclarified. Our aim was to investigate the correlation between biochemically assessed thyroid function as well as dysfunction duration and mortality.

Methods

Register-based follow-up study of 239,768 individuals with a serum TSH measurement from hospitals and/or general practice in Funen, Denmark. Measurements were performed at a single laboratory from January 1st 1995 to January 1st 2011. Cox regression was used for mortality analyses and Charlson Comorbidity Index (CCI) was used as comorbidity score.

Results

Hazard ratios (HR) with 95% confidence intervals (CI) for mortality with decreased (<0.3 mIU/L) or elevated (>4.0 mIU/L) levels of TSH were 2.22; 2.14–2.30; P<0.0001 and 1.28; 1.22–1.35; P<0.0001, respectively. Adjusting for age, gender, CCI and diagnostic setting attenuated the risk estimates (HR 1.23; 95% CI: 1.19–1.28; P<0.0001, mean follow-up time 7.7 years, and HR 1.07; 95% CI: 1.02–1.13; P = 0.004, mean follow-up time 7.2 years) for decreased and elevated values of TSH, respectively. Mortality risk increased by a factor 1.09; 95% CI: 1.08–1.10; P<0.0001 or by a factor 1.03; 95% CI: 1.02–1.04; P<0.0001 for each six months a patient suffered from decreased or elevated TSH, respectively. Subdividing according to degree of thyroid dysfunction, overt hyperthyroidism (HRovert 1.12; 95% CI: 1.06–1.19; P<0.0001), subclinical hyperthyroidism (HRsubclinical 1.09; 95% CI: 1.02–1.17; P = 0.02) and overt hypothyroidism (HRovert 1.57; 95% CI: 1.34–1.83; P<0.0001), but not subclinical hypothyroidism (HRsubclinical 1.03; 95% CI: 0.97–1.09; P = 0.4) were associated with increased mortality.

Conclusions and Relevance

In a large-scale, population-based cohort with long-term follow-up (median 7.4 years), overt and subclinical hyperthyroidism and overt but not subclinical hypothyroidism were associated with increased mortality. Excess mortality with increasing duration of decreased or elevated serum TSH suggests the importance of timely intervention in individuals with thyroid dysfunction.  相似文献   
576.
DEVELOPMENT OF DISPLAY BEHAVIOR IN YOUNG CAPTIVE BEARDED SEALS   总被引:1,自引:0,他引:1  
In this study of the ontogeny of vocal behavior in captive bearded seals, Erignathus barbatus , (three males and three females), only males exhibited vocal displays. The onset of display behavior coincided with sexual maturity. Males exhibited three types of dive displays associated with the performance of vocalizations. Vocalizing individuals were frequently attended by another male that maintained passive muzzle contact with the vocalizing male. These interactions were non-aggressive and might play a role in the establishment of a social hierarchy or they might allow the attendee to obtain "near-field" vocal information from the displaying male. Captive males' vocalizations resembled those of males in the wild. However, display dives were shorter, and fewer vocalization types were documented among the captive males compared to bearded seals in the wild. The capacity of the captive males for producing well-formed, long calls with large frequency changes was also significantly less than for wild males. These capacities will likely develop further as the males grow older. Individual capacity for vocal production appears to develop gradually, showing plasticity in form development over time.  相似文献   
577.
578.
579.
Deoxynivalenol (DON) content and Fusarium spp. ( Fusarium graminearum , Fusarium culmorum , Fusarium avenaceum , Microdochium nivale and Fusarium poae ) of mycotoxin-producing Fusarium species in winter wheat in Belgium (Flanders) were determined. Field trials were set up in the varietal testing network of Flanders Agricultural Centre for Small Grains (Roeselare – Beitem, Belgium) and followed up during growing seasons 2001–2002, 2002–2003, 2003–2004 and 2004–2005. Fusarium infection and DON contamination were mainly influenced by location and environmental parameters. Mean DON levels ranged from 0 to 15 mg/kg. Over the period of four growing seasons cvs Deben, Ordeal and Napier had the highest DON contamination. Seasonal and local weather conditions before and during flowering together with local crop husbandry measures (crop rotation, soil preparation) seemed to be of great importance in explaining the variation in results obtained. At Bottelare a positive correlation between disease index and DON content was found for the growing seasons 2001–2002 and 2002–2003, but not the season 2003–2004. Fusarium graminearum and F. culmorum were in general the most frequently occurring Fusarium spp. in Flanders over the 4 years but the composition of the Fusarium population varied strongly from location to location and from year to year. Fusarium graminearum predominated in areas especially where maize was cultivated, whereas in areas with more small cereals in the crop rotation more F. culmorum was present. Also temperature played a role in the composition of Fusarium spp.  相似文献   
580.
Members of the pacifastin family are serine peptidase inhibitors, found in arthropods and have many members within different insect orders. Based on their structural characteristics, inhibitors of this peptide family are divided into two groups (I and II). Members of both groups exhibit specificity towards different types of serine peptidases. In addition, group I inhibitors display species selectivity. The specificity and selectivity of these inhibitors depends on the nature of their P1 residue and on additional interaction sites at the inhibitor's surface. Functional analysis studies have shown that crustacean pacifastin plays a key role in the immune response, whereas insect pacifastin-like peptides have multiple regulatory functions in processes involved in immunity, reproduction, phase transition, etc.  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