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   536篇
  免费   30篇
林业   12篇
农学   9篇
基础科学   7篇
  69篇
综合类   166篇
农作物   13篇
水产渔业   24篇
畜牧兽医   227篇
园艺   9篇
植物保护   30篇
  2021年   5篇
  2020年   5篇
  2019年   7篇
  2018年   7篇
  2017年   11篇
  2016年   12篇
  2015年   9篇
  2014年   13篇
  2013年   16篇
  2012年   11篇
  2011年   20篇
  2010年   17篇
  2009年   11篇
  2008年   24篇
  2007年   19篇
  2006年   11篇
  2005年   15篇
  2004年   22篇
  2003年   7篇
  2002年   7篇
  2001年   12篇
  2000年   7篇
  1999年   7篇
  1998年   9篇
  1997年   8篇
  1995年   7篇
  1994年   12篇
  1992年   8篇
  1991年   8篇
  1990年   6篇
  1989年   8篇
  1988年   9篇
  1987年   6篇
  1986年   11篇
  1985年   8篇
  1984年   6篇
  1983年   8篇
  1978年   7篇
  1976年   6篇
  1974年   14篇
  1973年   5篇
  1972年   4篇
  1971年   6篇
  1970年   6篇
  1969年   11篇
  1968年   5篇
  1967年   4篇
  1930年   5篇
  1920年   4篇
  1904年   4篇
排序方式: 共有566条查询结果,搜索用时 634 毫秒
141.
1. Ovomucoids were purified from Muscovy duck, domestic duck and domestic goose.

2. Peptide maps of cyanogen bromide‐cleaved ovomucoids from Muscovy duck and domestic duck were very similar to one another, but differed from that of goose.

3. Muscovy duck ovomucoid showed the same protease inhibitory pattern as ovomucoid from domestic duck, inhibiting trypsin in the molar ratio of 1:2 and chymotrypsin 1:1.

4. Inhibitory complexes could be detected between chymotrypsin and ovomucoid from both Muscovy and domestic duck, but not from goose, by using non‐denaturing gels.

5. No complexes could be detected between DFP‐inactivated chymotrypsin and any of the ovomucoids.

6. The results show that of ovomucoid from Muscovy duck more closely resembles that from domestic duck than goose.  相似文献   

142.
143.
Two Old English Sheepdog littermates were evaluated for weakness that developed during periods of minimally intense exercise. Lactic acidosis accompanied by increased muscle enzyme activity, an increased lactate/pyruvate ratio, and increased venous PO2 supported the possibility of defective mitochondrial oxygen use. Electromyographic abnormalities included increased insertional activity and complex repetitive discharges. Muscle alterations included scattered myofiber necrosis, abundant endomysial connective tissue, excessive glycogen accumulation, and greater than normal numbers and vacuolation of mitochondria. A distinctive pattern of subsarcolemmal mitochondrial aggregates, referred to as "ragged red fibers" in human mitochondrial myopathies, was observed in muscle biopsy samples from 1 dog. Several features of the disease in these dogs, including onset of weakness during early life, simultaneous disease in littermates, subtle nonprogressive weakness of at least 3 years' duration, and partial reversibility of lactic acidosis following rest were suggestive of an inborn error of metabolism, consistent with mitochondrial myopathy.  相似文献   
144.
Rhizomania, one of the most devastating diseases in sugar beet production, is caused by Beet necrotic yellow vein virus (BNYVV) and transmitted by Polymyxa betae. Previously, disease control was possible by cultivation of sugar beet hybrids carrying a major resistance gene Rz1, which restricts virus accumulation in taproots and suppresses symptom development. Over the last few years, BNYVV strains with four RNA components have arisen, which are able to overcome Rz1‐mediated resistance. All strains described so far possess an A67V amino acid exchange within the RNA3‐encoded P25 pathogenicity factor. In this study, BNYVV was isolated from Rz1 plants, collected in the United Kingdom, the Netherlands and Germany, displaying patches of strong rhizomania symptoms. Sequencing of the coat protein and P25 gene of three isolates showed 100% nucleotide sequence identity and detected AYPR as the P25 tetrad amino acid composition. The ability of this strain to accumulate to higher levels in young plants of Rz1 resistant but not in Rz1 + Rz2 resistant genotypes was initially demonstrated in a greenhouse assay in natural field soil from the Netherlands. This strain was loaded into a virus‐free P. betae population and compared to reference strains. The AYPR strain retained its resistance‐breaking ability in the Rz1 genotypes and displayed replication at a higher rate compared to the Rz1‐resistance‐breaking P type. The strain origin is unclear and it remains speculative whether the occurrence at different geographic locations is the result of independent selection or displacement of infested soil.  相似文献   
145.
Experiences from the Mitigation Options for Phosphorus and Sediment (MOPS) projects, which aim to determine the effectiveness of measures to reduce pollutant loading from agricultural land to surface waters, have been used to contribute to the findings of a recent paper (Kay et al., 2009, Agricultural Systems, 99, 67-75), which reviewed the efficacy of contemporary agricultural stewardship measures for ameliorating the water pollution problems of key concern to the UK water industry. MOPS1 is a recently completed 3-year research project on three different soil types in the UK, which focused on mitigation options for winter cereals. MOPS1 demonstrated that tramlines can be the major pathway for sediment and nutrient transfer from arable hillslopes, and that although minimum tillage, crop residue incorporation, contour cultivation, and beetle banks also have potential to be cost-effective mitigation options, tramline management is the one of the most promising treatments for mitigating diffuse pollution losses, as it was able to reduce sediment and nutrient losses by 72-99% in four out of five site years trialled. Using information from the MOPS projects, this paper builds on the findings of Kay et al. to provide an updated picture of the evidence available and the immediate needs for research in this area.  相似文献   
146.
Yield and nutritional responses to waterlogging of soybean cultivars   总被引:1,自引:0,他引:1  
Furrow irrigating soybean prior to a large, unexpected rainfall event can reduce nitrogen fixation and crop yield. The objective of this study was to evaluate the tolerance of soybean cultivars to waterlogged alluvial soils. Five cultivars were selected, which showed a range of tolerances to excessive soil water. Flood duration and flood timing experiments were conducted on clay and silt loam soils. Main plots were flooding duration and flood timing and subplots were soybean cultivars. Most cultivars were able to withstand flooding for 48–96 h without crop injury. Cultivars flooded during the V5 growth stage suffered the least amount of yield loss. The greatest yield losses from flooding occurred at the R5 growth stage. Soybean yields from cultivars flooded at R5 were reduced by 20–39% compared to non-flooded checks. Pioneer 94B73 (cv.) had no significant change in yield from flooding for 192 h at any of the three growth stages, compared to non-flooded controls.  相似文献   
147.
Analysis of the interlayer infrared conductivity of cuprate high-transition temperature superconductors reveals an anomalously large energy scale extending up to midinfrared frequencies that can be attributed to formation of the superconducting condensate. This unusual effect is observed in a va- riety of materials, including Tl2Ba2CuO6+x, La2-xSrxCuO4, and YBa2Cu3O6.6, which show an incoherent interlayer response in the normal state. Midinfrared range condensation was examined in the context of sum rules that can be formulated for the complex conductivity. One possible interpretation of these experiments is in terms of a kinetic energy change associated with the superconducting transition.  相似文献   
148.
149.
150.
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