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   199篇
  免费   18篇
  国内免费   1篇
林业   10篇
农学   5篇
基础科学   2篇
  43篇
综合类   30篇
农作物   11篇
水产渔业   12篇
畜牧兽医   88篇
园艺   3篇
植物保护   14篇
  2023年   5篇
  2021年   9篇
  2020年   15篇
  2019年   4篇
  2018年   8篇
  2017年   4篇
  2016年   10篇
  2015年   4篇
  2014年   8篇
  2013年   9篇
  2012年   9篇
  2011年   18篇
  2010年   10篇
  2009年   6篇
  2008年   10篇
  2007年   16篇
  2006年   14篇
  2005年   7篇
  2004年   8篇
  2003年   8篇
  2002年   13篇
  2001年   2篇
  2000年   3篇
  1998年   3篇
  1994年   1篇
  1993年   2篇
  1992年   1篇
  1991年   1篇
  1990年   2篇
  1984年   1篇
  1977年   1篇
  1972年   1篇
  1963年   1篇
  1958年   1篇
  1955年   1篇
  1948年   2篇
排序方式: 共有218条查询结果,搜索用时 15 毫秒
51.
The use of bioherbicides containing fungal active ingredients or natural fungal molecules is one of the possible solutions to reduce the use of chemical products. This paper focuses on studies of bioherbicides, including both living fungi and natural fungal molecules, published in the last 45 years, and their associated weed targets; current problems in the development of bioherbicides are also discussed. Bibliometric methods based on the Web of Science database were used to analyse relevant articles published between 1973 and 2018. Overall analysis suggested that interest in bioherbicides extends over the preceding thirty years, when many potential microorganisms and natural fungal molecules were proposed. Furthermore, analysis of about 229 articles indicated an encouraging exploitable potential, although there is a real gap between the number of experimental studies and the small number of products currently on the market. A dozen fungal-based bioherbicides are on the market in the United States and Canada, while countries, such as China and South Africa, have one, and none is available in Europe. The active ingredients in these bioherbicides are living fungi, but no fungal molecule-based product is thus far on the market. Reasons for this gap include production hurdles, formulation process, ecological fitness, duration of herbicidal effects, and costly and time-consuming registration procedures. However, it is clear that analysis of fungus–plant interactions provides a promising source of bioherbicides that may be applied to appropriate cropping systems for environment-friendly, sustainable weed control.  相似文献   
52.
53.
Although pecans are associated with IgE-mediated food allergies, the allergens responsible remain to be identified and characterized. The 2S albumin gene was amplified from the pecan cDNA library. Dot-blots were used to screen the recombinant protein with pecan allergic patients' serum. The affinity purified native protein was analyzed by Edman sequencing and mass spectrometry/mass spectrometry (MS/MS) analysis. Cross-reactivity with walnut was determined by inhibition enzyme-linked immunosorbent assay (ELISA). Sequential epitopes were determined by probing the overlapping peptides with three different patients' serum pool. The 3-dimensional homology model was generated, and the locations of the pecan epitopes were compared with those of known sequential epitopes on other allergenic tree nut homologues. Of 28 patients tested by dot-blot, 22 (79%) bound to 2S albumin, designated as Car i 1. Edman sequencing and the MS/MS sequencing of native 2S albumin confirmed the identity of recombinant (r) Car i 1. Both pecan and walnut protein extracts inhibited the IgE-binding to rCar i 1. Sequential epitope mapping indicated weak, moderate, and strong reactivity against 12, 7, and 5 peptides, respectively. Of the 11 peptides recognized by all serum pools, 5 peptides were strongly reactive and located in 3 discrete regions of the Car i 1 (amino acids 43-57, 67-78, and 106-120). Three-dimensional modeling revealed IgE-reactive epitopes to be solvent accessible and share significant homology with other tree nuts providing a possible basis for previously observed cross-reactivity.  相似文献   
54.
Time/area closures have been widely used in fisheries management to prevent overfishing and the destruction of marine biodiversity. To a lesser degree, such spatio‐temporal management measures have been used to reduce by‐catch of finfish or protected species. However, as ecosystem‐based management approaches are employed and more fisheries are managed through multispecies, multiobjective models, the management of by‐catch will likely become increasingly important. The elimination of by‐catch has become a primary goal of the fishing policies of many countries. It is particularly relevant in the United States, as the deadline for setting annual catch limits (ACLs) in all fisheries passes in 2011. This will result in a dramatic expansion of the number of catch and by‐catch quotas. Such catch measures may result in the early closure of otherwise sustainable fisheries when by‐catch quotas are exceeded. To prevent such closures and the consequent economic hardship to fishers and the economy, it is imperative that managers be given the tools necessary to reduce by‐catch and improve fishing selectivity. Targeted spatio‐temporal fishery closures are one solution open to managers. Here, we examine how the spatio‐temporal and oceanographic characteristics of by‐catch may be used by managers to design fishery closures, and place these methods within a decision tree to assist managers to identify appropriate management measures. We argue that the current movement towards marine spatial planning (MSP) presents an important impetus to examine how we manage fisheries spatially, and we offer a first step towards the objective participation of fisheries in the MSP process.  相似文献   
55.
Lead foreign body in a cat''s bladder   总被引:1,自引:0,他引:1  
The follow-up history for 2 years, of a sterile lead implant (air-gun pellet) in a cat's bladder, shows that this does not form the nucleus for calculus formation.
Résumé. Après avoir suivi pendant deux ans l'implant stérile d'un plomb (plomb pour carabine à air comprimé) dans la vessie d'un chat, on a pu conclure qu'il ne sert pas de noyau lorsque se forme un calcul.
Zusammenfassung. Die sich über 2 Jahre erstreckende Beobachtung eines sterilen Bleiimplantats (Luftgewehrgeschoss) in der Blase einer Katze zeigt, dass dieses nicht den Kern einer Calculusbildung abgab.  相似文献   
56.
57.
58.
59.
Cassini's successful orbit insertion has provided the first examination of Saturn's magnetosphere in 23 years, revealing a dynamic plasma and magnetic environment on short and long time scales. There has been no noticeable change in the internal magnetic field, either in its strength or its near-alignment with the rotation axis. However, the external magnetic field is different compared with past spacecraft observations. The current sheet within the magnetosphere is thinner and more extended, and we observed small diamagnetic cavities and ion cyclotron waves of types that were not reported before.  相似文献   
60.
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