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   252篇
  免费   23篇
  国内免费   1篇
林业   17篇
农学   10篇
基础科学   1篇
  37篇
综合类   54篇
农作物   12篇
水产渔业   11篇
畜牧兽医   121篇
园艺   7篇
植物保护   6篇
  2023年   5篇
  2022年   7篇
  2021年   6篇
  2020年   18篇
  2019年   10篇
  2018年   9篇
  2017年   9篇
  2016年   13篇
  2015年   8篇
  2014年   10篇
  2013年   9篇
  2012年   21篇
  2011年   18篇
  2010年   17篇
  2009年   4篇
  2008年   19篇
  2007年   11篇
  2006年   13篇
  2005年   7篇
  2004年   10篇
  2003年   4篇
  2002年   13篇
  2001年   1篇
  2000年   2篇
  1999年   1篇
  1998年   1篇
  1996年   2篇
  1995年   1篇
  1994年   1篇
  1992年   2篇
  1989年   1篇
  1985年   3篇
  1984年   1篇
  1983年   1篇
  1979年   1篇
  1974年   1篇
  1973年   3篇
  1972年   3篇
  1964年   1篇
  1962年   1篇
  1949年   1篇
  1935年   1篇
  1931年   4篇
  1895年   2篇
排序方式: 共有276条查询结果,搜索用时 15 毫秒
121.
According to German food guidelines, almonds are the only oilseed ingredient allowed for the production of marzipan. Persipan is a marzipan surrogate in which the almonds are replaced by apricot or peach kernels. Cross-contamination of marzipan products with persipan may occur if both products are produced using the same production line. Adulterations or dilutions, respectively, of marzipan with other plant-derived products, for example, lupine or pea, have also been found. Almond and apricot plants are closely related. Consequently, classical analytical methods for the identification/differentiation often fail or are not sensitive enough to quantify apricot concentrations below 1%. Polymerase chain reaction (PCR)-based methods have been shown to enable the differentiation of closely related plant species in the past. These methods are characterized by high specificity and low detection limits. Isolation methods were developed and evaluated especially with respect to the matrix marzipan in terms of yield, purity, integrity, and amplificability of the isolated DNA. For the reliable detection of apricot, peach, pea, bean, lupine, soy, cashew, pistachio, and chickpea, qualitative standard and duplex PCR methods were developed and established. The applicability of these methods was tested by cross-reaction studies and analysis of spiked raw pastes. Contaminations at the level of 0.1% could be detected.  相似文献   
122.
Soil environmentally contaminated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was given by gavage to guinea pigs and rats. The development of a characteristic clinicopathologic syndrome in guinea pigs, the induction of aryl hydrocarbon hydroxylase in rats, and the presence of TCDD in the livers of both species show that TCDD in soil exhibits high biological availability after ingestion.  相似文献   
123.
How chaperone interactions affect protein folding pathways is a central problem in biology. With the use of optical tweezers and all-atom molecular dynamics simulations, we studied the effect of chaperone SecB on the folding and unfolding pathways of maltose binding protein (MBP) at the single-molecule level. In the absence of SecB, we find that the MBP polypeptide first collapses into a molten globulelike compacted state and then folds into a stable core structure onto which several alpha helices are finally wrapped. Interactions with SecB completely prevent stable tertiary contacts in the core structure but have no detectable effect on the folding of the external alpha helices. It appears that SecB only binds to the extended or molten globulelike structure and retains MBP in this latter state. Thus during MBP translocation, no energy is required to disrupt stable tertiary interactions.  相似文献   
124.
Selective autophagy can be mediated via receptor molecules that link specific cargoes to the autophagosomal membranes decorated by ubiquitin-like microtubule-associated protein light chain 3 (LC3) modifiers. Although several autophagy receptors have been identified, little is known about mechanisms controlling their functions in vivo. In this work, we found that phosphorylation of an autophagy receptor, optineurin, promoted selective autophagy of ubiquitin-coated cytosolic Salmonella enterica. The protein kinase TANK binding kinase 1 (TBK1) phosphorylated optineurin on serine-177, enhancing LC3 binding affinity and autophagic clearance of cytosolic Salmonella. Conversely, ubiquitin- or LC3-binding optineurin mutants and silencing of optineurin or TBK1 impaired Salmonella autophagy, resulting in increased intracellular bacterial proliferation. We propose that phosphorylation of autophagy receptors might be a general mechanism for regulation of cargo-selective autophagy.  相似文献   
125.
126.
127.
Modulation of the growth of human and murine cell lines in vitro by recombinant human tumor necrosis factor-alpha (rTNF-alpha) and recombinant human interferon-gamma (rIFN-gamma) was investigated. rTNF-alpha had cytostatic or cytolytic effects on only some tumor cell lines. When administered together with rIFN-gamma, rTNF-alpha showed enhanced antiproliferative effects on a subset of the cell lines tested. In contrast to its effects on sensitive tumor cells, rTNF-alpha augmented the growth of normal diploid fibroblasts. Variations in the proliferative response induced by rTNF-alpha were apparently not due to differences in either the number of binding sites per cell or their affinity for rTNF-alpha. These observations indicate that the effects of rTNF-alpha on cell growth are not limited to tumor cells, but rather that this protein may have a broad spectrum of activities in vivo.  相似文献   
128.
129.
130.
Financial assessment in forestry is characterized by considerable impacts of risk factors due to large time horizons. Accounting for the risk of timber price fluctuation mixtures of Rauli (Nothofagus alpina, P. et E., OERST.) and Douglas fir (Pseudotsuga menziesii, Mirb.) have been evaluated by different approaches. The data were taken from plantations in Southern Chile between 39°10′ and 39°50′ south latitude. Increments have been modelled in order to calculate possible financial returns and changed volume growth has been taken into consideration for mixtures of large blocks and single-tree mixtures of both species. The optimum proportions of both species varied depending on the different perspectives of the financial assessment: first, the effects of diversification shown by classical portfolio approach were low; second, the integration of moderate risk aversion of the decision maker resulted in predominance of stands with high proportions of Douglas fir, but optimum proportions of Rauli increased with higher degrees of risk aversion. The maximization of the expected surplus in relation to the fluctuation of net present values (NPVs) (Sharpe ratio) resulted in even higher optimum proportions of Rauli. However, mixed stands proved more advantageous in contrast to the financial assessment without consideration of the risk factor timber price fluctuation (maximization of NPV). Finally, the integration of further risk factors can have impacts on the results as well as the integration of further effects of single-tree mixtures. Both lacks of information should be investigated for more extensive assessments in the future.  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