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   815篇
  免费   58篇
  873篇
  2024年   3篇
  2023年   3篇
  2022年   9篇
  2021年   24篇
  2020年   7篇
  2019年   10篇
  2018年   20篇
  2017年   17篇
  2016年   25篇
  2015年   35篇
  2014年   42篇
  2013年   62篇
  2012年   63篇
  2011年   58篇
  2010年   29篇
  2009年   46篇
  2008年   44篇
  2007年   48篇
  2006年   29篇
  2005年   54篇
  2004年   38篇
  2003年   41篇
  2002年   42篇
  2001年   8篇
  2000年   9篇
  1999年   13篇
  1998年   10篇
  1997年   9篇
  1996年   8篇
  1995年   5篇
  1994年   2篇
  1993年   2篇
  1991年   4篇
  1990年   5篇
  1989年   4篇
  1988年   5篇
  1987年   4篇
  1986年   2篇
  1985年   2篇
  1984年   2篇
  1982年   2篇
  1981年   4篇
  1978年   2篇
  1975年   2篇
  1974年   3篇
  1969年   3篇
  1968年   1篇
  1967年   2篇
  1966年   2篇
  1965年   1篇
排序方式: 共有873条查询结果,搜索用时 15 毫秒
1.
Tachykinins protect against ethanol-induced gastric lesions in rats   总被引:3,自引:0,他引:3  
Subcutaneous pretreatment of rats with neurokinin (NK) A or the fragment NKA(4-10) reduced the degree of gastric lesions induced by oral administration of 96% ethanol. The protective effect of NKA(4-10) was dose-dependent. Arg-NKB, the water soluble derivative of NKB, was less effective than NKA or NKA(4-10) while [Me-Phe7]NKB, substance P (SP) and SP-methyl-ester were inactive. The NKA(4-10) antilesion effect was reversed by pretreatment with N-ethyl-maleimide, suggesting a possible involvement of sulphydryls in its action. Among the nonmammalian tachykinins, kassinin significantly reduced ethanol-induced lesions while eledoisin and physalaemin at equivalent molar doses were inactive. These results provide, for the first time, evidence that tachykinins and their derivatives exert gastroprotective activity toward ethanol-induced haemorrhagic lesions. Assuming a receptor-mediated mechanism, NK-2 sites could be involved.  相似文献   
2.
The strategy of the United Nations Decade on Ecosystem Restoration identifies three pathways for action for overcoming six global barriers thought to hamper upscaling. We evaluated 6,023 peer-reviewed and gray literature papers published over the last two decades to map the information landscape underlying the barriers and associated pathways for action across world regions, terrestrial ecosystem types, restorative interventions and their outcomes. Overall, the literature addressed more the financial and legislative barriers than the technical and research-related ones, supporting the view that social, economic and political factors hamper scaling up ecosystem restoration. Latin America, Africa, and North America were the most prominent regions in the literature, yet differed in the number of publications addressing each barrier. An overwhelming number of publications focused on forests (78%), while grasslands (6%), drylands (3%), and mangroves (2%) received less attention. Across the three pathways for action, the action lines on (1) promoting long-term ecosystem restoration actions and monitoring and (2) education on restoration were the most underrepresented in the literature. In general, restorative interventions assessed rendered positive outcomes except those of a political, legislative or financial nature which reported negative or inconclusive outcomes. Our indicative assessment reveals critical information gaps on barriers, pathways, and types of restorative interventions across world regions, particularly related to specific social issues such as education for ecosystem restoration. Finally, we call for refining “strength of evidence” assessment frameworks that can systematically appraise, synthesize and integrate information on traditional and practitioner knowledge as two essential components for improving decision-making in ecosystem restoration.  相似文献   
3.
The aim of radiotherapy is to eradicate cancer cells with ionizing radiation; tumor cell death following irradiation can be induced by several signaling pathways, most of which are triggered as a consequence of DNA damage, the primary and major relevant cell response to radiation. Several lines of evidence demonstrated that ceramide, a crucial sensor and/or effector of different signalling pathways promoting cell cycle arrest, death and differentiation, is directly involved in the molecular mechanisms underlying cellular response to irradiation. Most of the studies strongly support a direct relationship between ceramide accumulation and radiation-induced cell death, mainly apoptosis; for this reason, defining the contribution of the multiple metabolic pathways leading to ceramide formation and the causes of its dysregulated metabolism represent the main goal in order to elucidate the ceramide-mediated signaling in radiotherapy. In this review, we summarize the current knowledge concerning the different routes leading to ceramide accumulation in radiation-induced cell response with particular regard to the role of the enzymes involved in both ceramide neogenesis and catabolism. Emphasis is placed on sphingolipid breakdown as mechanism of ceramide generation activated following cell irradiation; the functional relevance of this pathway, and the role of glycosphingolipid glycohydrolases as direct targets of ionizing radiation are also discussed. These new findings add a further attractive point of investigation to better define the complex interplay between sphingolipid metabolism and radiation therapy.  相似文献   
4.
Nonalcoholic fatty liver disease (NAFLD) is currently the most common liver disease worldwide, both in adults and in children. NAFLD is characterized by aberrant lipid storage in hepatocytes (hepatic steatosis) and inflammatory progression to nonalcoholic steatohepatitis. Evidences so far suggest that intrahepatic lipid accumulation does not always derive from obesity. Gut microbiota has been considered as a regulator of energy homeostasis and ectopic fat deposition, suggesting its implications in metabolic diseases. Probiotics are live microbial that alter the enteric microflora and have beneficial effects on human health. Although the molecular mechanisms of probiotics have not been completely elucidated yet, many of their effects have proved to be beneficial in NAFLD, including the modulation of the intestinal microbiota, an antibacterial substance production, an improved epithelial barrier function and a reduced intestinal inflammation. Given the close anatomical and functional correlation between the bowel and the liver, and the immunoregulatory effects elicited by probiotics, the aim of this review is to summarize today's knowledge about probiotics in NAFLD, focusing in particular on their molecular and biochemical mechanisms, as well as highlighting their efficacy as an emerging therapeutic strategy to treat this condition.  相似文献   
5.
6.
Glycoconjugate Journal - Neisseria meningitidis is a major cause of bacterial meningitidis worldwide. Children less than five years and adolescents are particularly affected. Nearly all invasive...  相似文献   
7.
8.
In revegetation projects, distinguishing species that can be passively restored by natural regeneration from those requiring active restoration is not a trivial decision. We quantified tree species dominance (measured by an importance value index, IVIi) and used abundance–size correlations to select those species suitable for passive and/or active restoration of disturbed riparian vegetation in the Lacandonia region, Southern Mexico. We sampled riparian vegetation in a 50 × 10–m transect in each of six reference (RE) and five disturbed (DE) riparian ecosystems. Those species representing more than 50% of total IVI in each ecosystem were selected, and Spearman rank correlation between abundance and diameter classes was calculated. For eight species, it was determined that passive restoration could be sufficient for their establishment. Another eight species could be transplanted by means of active restoration. Five species regenerate well in only one ecosystem type, suggesting that both restoration strategies could be used depending on the degree of degradation. Finally, two species were determined to not be suitable for restoration in the RE (based on the above selection criteria) and were not selected during this initial stage of our restoration project. The high number of tree species found in the RE suggests that the species pool for ecological restoration is large. However, sampling in both ecosystem types helped us reduce the number of species that requires active restoration. Restoration objectives must guide the selection of which methods to implement; in different conditions, other criteria such as dispersal syndrome or social value could be considered in the species selection.  相似文献   
9.
The clinical usefulness of an immunotest was evaluated by using purified poly(adenosine diphosphate (ADP)-ribose) polymerase from Sulfolobus solfataricus (PARPSso) as an antigen to detect the presence of abnormal anti-PARP antibodies in the sera of patients with systemic lupus erythematosus (SLE) at different clinical stages. Sera from 44 patients with SLE, subgrouped on the basis of disease activity (16 with inactive disease, 28 with active disease) were analysed with a new immunotest to detect anti-PARP antibodies, and with an immunofluorescent (IIF) assay for antinuclear antibodies (ANA) detection. ANA detection by IIF revealed that sera of healthy subjects were negative, whereas sera from patients with SLE were positive in all cases (13 positive at 1:80, 15 at 1:160, 15 at 1:320, 1 at 1:640, v/v). Anti-PARP activity was higher in ANA-positive patients than in controls (p?=?0.005). Within the group of SLE sera, disease and anti-PARP activity was increased more significantly in patients with active than in those with inactive disease (p?p?=?0.001, respectively). Correlation between anti-PARP and disease activity in SLE patients was statistically significant (p?Sso seems to be suitable for detecting anti-PARP antibodies and could play a role as a serological marker of disease activity in patients with SLE.  相似文献   
10.
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