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   175篇
  免费   4篇
  2021年   7篇
  2019年   1篇
  2018年   3篇
  2016年   1篇
  2015年   8篇
  2014年   12篇
  2013年   8篇
  2012年   11篇
  2011年   18篇
  2010年   14篇
  2009年   7篇
  2008年   16篇
  2007年   14篇
  2006年   7篇
  2005年   9篇
  2004年   7篇
  2003年   4篇
  2002年   2篇
  2001年   10篇
  2000年   4篇
  1999年   3篇
  1998年   4篇
  1997年   2篇
  1995年   1篇
  1994年   2篇
  1987年   1篇
  1978年   1篇
  1976年   1篇
  1957年   1篇
排序方式: 共有179条查询结果,搜索用时 15 毫秒
151.
152.

Introduction  

High Mobility Group Box 1 (HMGB1) is a nuclear non-histone protein. HMGB1, which is secreted by inflammatory cells and passively released from apoptotic and necrotic cells, may act as a pro-inflammatory mediator. As apoptotic cells accumulate in systemic lupus erythematosus (SLE), HMGB1 levels might be increased in SLE. HMGB1 may also serve as an autoantigen, leading to the production of anti-HMGB1 antibodies. In this study we determined levels of HMGB1 and anti-HMGB1 in SLE patients in comparison to healthy controls (HC) and analysed their relation with disease activity.  相似文献   
153.
Agriculture faces serious problems in feeding 9 billion people by 2050: production must be increased and ecosystem services maintained under conditions for growing crops that are predicted to worsen in many parts of the world. A proposed solution is sustainable intensification of agriculture, whereby yields are increased on land that is currently cultivated, so sparing land to deliver other ecosystem services. Genetically modified (GM) crops are already contributing to sustainable intensification through higher yields and lower environmental impacts, and have potential to deliver further significant improvements. Despite their widespread successful use elsewhere, the European Union (EU) has been slow to introduce GM crops: decisions on applications to import GM commodities are lengthy, and decision-making on applications to cultivate GM crops has virtually ceased. Delayed import approvals result in economic losses, particularly in the EU itself as a result of higher commodity prices. Failure to grant cultivation approvals costs EU farmers opportunities to reduce inputs, and results in loss of agricultural research and development from the EU to countries such as the United States and China. Delayed decision-making in the EU ostensibly results from scientific uncertainty about the effects of using GM crops; however, scientific uncertainty may be a means to justify a political decision to restrict cultivation of GM crops in the EU. The problems associated with delayed decision-making will not improve until there is clarity about the EU's agricultural policy objectives, and whether the use of GM crops will be permitted to contribute to achieving those objectives.  相似文献   
154.
155.
Fish populations in Albasini and Nandoni dams are negatively affected by extensive netting practices. This observation was made by the authors following a number of fish health assessment surveys related to aquatic pollution in the Luvuvhu River catchment. A comparison between the number and size of fish collected over a period of ten years indicated decreases in the average size and a consistent low number of fish, despite similar extensive sampling efforts. Unregulated netting is a common practice in both dams. This may become a serious problem as fish from these two dams are an important source of protein for the local communities. The purpose of this note is to report that gillnets are illegally used in the system and on the effect this could have on the fish population. The authors suggest educational and awareness initiatives to inform local communities about the importance of utilising fish in a sustainable manner to ensure the livelihood of generations to come.  相似文献   
156.
The debate concerning genetically modified crops illustrates confusion between the role of scientists and that of wider society in regulatory decision making. We identify two fundamental misunderstandings, which, if rectified, would allow progress with confidence. First, scientific risk assessment needs to test well-defined hypotheses, not simply collect data. Second, risk assessments need to be placed in the wider context of risk analysis to enable the wider 'non-scientific' questions to be considered in regulatory decision making. Such integration and understanding is urgently required because the challenges to regulation will escalate as scientific progress advances.  相似文献   
157.
Apoptotic cells are thought to play an essential role in the pathogenesis of systemic lupus erythematosus (SLE). We hypothesise that delayed or altered clearance of apoptotic cells after UV irradiation will lead to inflammation in the skin of SLE patients. Fifteen SLE patients and 13 controls were irradiated with two minimal erythemal doses (MEDs) of ultraviolet B light (UVB). Subsequently, skin biopsies were analysed (immuno)histologically, over 10 days, for numbers of apoptotic cells, T cells, macrophages, and deposition of immunoglobulin and complement. Additionally, to compare results with cutaneous lesions of SLE patients, 20 biopsies of lupus erythematosus (LE) skin lesions were analysed morphologically for apoptotic cells and infiltrate. Clearance rate of apoptotic cells after irradiation did not differ between patients and controls. Influx of macrophages in dermal and epidermal layers was significantly increased in patients compared with controls. Five out of 15 patients developed a dermal infiltrate that was associated with increased epidermal influx of T cells and macrophages but not with numbers of apoptotic cells or epidermal deposition of immunoglobulins. Macrophages were ingesting multiple apoptotic bodies. Inflammatory lesions in these patients were localised near accumulations of apoptotic keratinocytes similar as was seen in the majority of LE skin lesions. In vivo clearance rate of apoptotic cells is comparable between SLE patients and controls. However, the presence of inflammatory lesions in the vicinity of apoptotic cells, as observed both in UVB-induced and in LE skin lesions in SLE patients, suggests that these lesions result from an inflammatory clearance of apoptotic cells.  相似文献   
158.
Determining the impact of genetically modified (GM) crops on beneficial organisms is an important aspect of the environmental risk assessment of GM crops. In the present study, the impact of Bt maize expressing Cry1Ab on the development and behaviour of the parasitoid Campoletis sonorensis was compared to individuals reared on hosts fed conventionally bred plants partially resistant to the European corn borer (Ostrinia nubilalis Hübner) and on susceptible maize hybrids. Adult parasitoids reared on Bt maize-fed Spodoptera frugiperda larvae were significantly smaller (15–30%) than those reared in hosts fed either of the conventional maize hybrids. The magnitude of this effect was dependent on the size of the host at oviposition and its subsequent growth rate. The development time of C. sonorensis was not affected by the maize treatment. In choice tests, female parasitoids displayed no preference for hosts fed a specific maize hybrid. No Cry1Ab was detected within adult parasitoids.  相似文献   
159.
160.
Transgenic potatoes have been transformed with a gene coding the snowdrop lectin Galanthus nivalis agglutinin (GNA) and they have been shown to be partially resistant to aphids. GNA binds to insect gut cells, including those of aphids, consequently inducing disruption of nutrient assimilation. Aphid parasitoids are important natural biocontrol agents of aphids and some species such as Aphelinus abdominalis are commercially available. Aphid parasitoids are endoparasitoids during their larval stages and free-living insects as adults. They could be directly or indirectly affected by GNA during both these stages. In this work, we present data on the potential direct and indirect effects of GNA on adult A. abdominalis. Aphelinus abdominalis is a synovigenic species (eggs are matured throughout the adult life) which needs a diet relatively rich in proteins and amino-acids to produce anhydropic eggs (large, yolk-rich eggs that do not expand in the host during embryonic stages). Adult A. abdominalis females feed on aphid haemolymph and they may be directly exposed to the entomotoxin or indirectly affected by a change in aphid haemolymph quality due to intoxication by GNA. We conducted a first tier experiment to investigate this potential risk. A. abdominalis females were offered either aphids reared on control diet or aphids reared on GNA 0.1% diet as hosts (i.e., as food and oviposition sites). No trace of GNA was found in females fed with GNA-aphids but no GNA could be detected in the haemolymph of aphids fed a 0.1% GNA diet. Longevity and fecundity were not affected suggesting that the quality of the haemolymph necessary for A. abdominalis egg maturation and production was not significantly altered.  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