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   503篇
  免费   25篇
林业   34篇
农学   17篇
基础科学   1篇
  107篇
综合类   18篇
农作物   20篇
水产渔业   47篇
畜牧兽医   231篇
园艺   5篇
植物保护   48篇
  2023年   4篇
  2022年   5篇
  2021年   11篇
  2020年   8篇
  2019年   10篇
  2018年   11篇
  2017年   8篇
  2016年   16篇
  2015年   19篇
  2014年   14篇
  2013年   35篇
  2012年   23篇
  2011年   28篇
  2010年   18篇
  2009年   20篇
  2008年   34篇
  2007年   46篇
  2006年   39篇
  2005年   33篇
  2004年   20篇
  2003年   25篇
  2002年   15篇
  2001年   11篇
  2000年   10篇
  1999年   11篇
  1998年   2篇
  1996年   1篇
  1995年   2篇
  1992年   4篇
  1991年   4篇
  1990年   2篇
  1989年   7篇
  1988年   4篇
  1987年   5篇
  1986年   1篇
  1985年   7篇
  1984年   2篇
  1983年   1篇
  1980年   1篇
  1979年   3篇
  1977年   1篇
  1975年   2篇
  1974年   1篇
  1970年   1篇
  1969年   1篇
  1968年   1篇
  1966年   1篇
排序方式: 共有528条查询结果,搜索用时 31 毫秒
1.
2.
3.
In the present study, proportional parts, amounts of major constituents, vitamins, minerals and fatty acids composition of Silky fowl eggs were examined compared with those of hen eggs. The ratio of egg yolk weight to whole egg weight of Silky fowl egg was significantly larger than that of egg yolk of hen egg. The amount of cholesterol of Silky fowl eggs were significantly (P < 0.01) less than those of hen eggs. The amount of vitamins (B2, B6, D and E), calcium and potassium in Silky fowl eggs were significantly higher than those of hen eggs. Unsaturated fatty acids in Silky fowl eggs were 62.5% among total fatty acids, the unsaturated fatty acids of hen eggs were 53.9%. Especially, the contents of arachidonic acid, docosapentaenoic acid and docosahexaenoic acid in Silky fowl eggs were significantly larger than in hen eggs.  相似文献   
4.
Insulin‐like growth factor‐1 (IGF‐1) is one of the important factors for growth, milk production and reproductive functions and mainly released from the liver in response to growth hormone (GH) via GH receptor (GHR) in cattle. Recently, some single nucleotide polymorphisms (SNPs) were identified in the bovine GHR gene. Some GHR‐SNPs were shown to be related to plasma IGF‐1 concentration in cattle. Hence, the capacity to IGF‐1 production in the liver might be affected by GHR‐SNP and associated with performance in the future. This study examined whether GHR‐SNP is associated with IGF‐1 production in the liver of pre‐pubertal heifers. In 71 Holstein calves, blood samples for genomic DNA extraction were obtained immediately after birth. To genotype the GHR‐SNPs in the promoter region, polymerase chain reaction (PCR) products were digested with restriction enzyme NsiI (cutting sites: AA, AG and GG). All heifers at 4 months of age were intramuscularly injected with 0.4 mg oestradiol benzoate. Blood samples were obtained from the jugular vein just before (0 h) and 24 h after injection. The number of AA, AG and GG at the NsiI site was 0, 17 and 54 respectively. In AG and GG, plasma GH concentrations were higher pre‐injection than 24 h post‐injection (p < 0.01). Moreover, plasma GH concentrations in AG post‐injection were higher than in GG (p < 0.05). In contrast, the GG genotype exhibited higher plasma IGF‐1 concentrations in pre‐injection than post‐injection (p < 0.01), although oestradiol did not change IGF‐1 concentration in the AG genotype. We conclude that the GG polymorphism in the promoter region of GHR is associated with a higher potential capacity of IGF‐1 production in the liver of cattle.  相似文献   
5.
Heated and hydrated naturally occurring dolomite showed very strong antiviral activity. Infectivity of avian and human influenza, avian infectious bronchitis (coronavirus), Newcastle disease (paramyxovirus) and avian laryngotracheitis (herpesvirus) viruses dropped at least 1,000 fold following contact with the dolomite for five minutes at 4 degrees C. Dolomite is expected to be useful to inhibit the incidence of emerging and re-emerging infectious diseases.  相似文献   
6.
7.
The heading date is an important trait for determining regional and climatic adaptability in rice. To expand the adaptability of the indica rice cultivar ‘IR64’, we pyramided multiple early or late heading quantitative trait locus (QTLs) in the ‘IR64’ genetic background by crossing previously developed near-isogenic lines (NILs) with a single QTL for early or late heading. The effects of pyramiding QTLs were observed in three different climatic zones of the Philippines, Madagascar, and Japan. The early heading pyramiding lines (PYLs) headed 6.2 to 12.8 days earlier than ‘IR64’ while the late heading PYLs headed 18.8 to 27.1 days later than ‘IR64’. The PYLs tended to produce low grain yield compared to ‘IR64’. The low yield was not improved by combining SPIKE, which is a QTL that increases the number of spikelets per panicle. Conversely, ‘IR64-PYL(7+10)’ carrying Hd5 and Hd1 headed earlier, produced more tillers, and more panicles per m2 than ‘IR64’, and mitigated the yield decrease in early heading. These results suggest that the effects of pyramided QTLs on heading date were consistent across various environments and PYLs could be used to enhance the adaptation of ‘IR64’ in other rice growing environments.  相似文献   
8.
The effect of bleeding on white muscle quality in amberjack and red sea bream was evaluated by measuring ATP-related compounds, volatile basic nitrogen (VBN), and the trimethylamine (TMA) content. The freshness was evaluated by the K value, and the degree of spoilage was elucidated by VBN and TMA. ATP was rapidly converted to ADP and AMP in the muscle and IMP was the main product of ATP degradation during iced storage. For both species, the IMP content was higher in the muscles of fish that were bled than in those unbled during iced storage. Conversely, the K value and the levels of hypoxanthine (Hx) and VBN were higher in the muscle tissue of unbled fish than in the bled tissue of both species. Similarly, the TMA content was higher in the unbled muscle tissues of both species after a week of storage.  相似文献   
9.
Red radish anthocyanin extract, which consists of 12 known acylated anthocyanins, was reacted with 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH) to generate peroxyl radicals under acidic pH conditions at 37 degrees C. The reaction products were isolated using preparative HPLC, and their chemical structures were determined to be p-hydroxybenzoic acid (1), 6-O-(E)-p-coumaroyl-2-O-beta-d- glucopyranosyl-alpha-d-glucopyranoside (3), p-coumaric acid (4), 6-O-(E)-feruloyl-2-O-beta-d-glucopyranosyl-alpha-d-glucopyranoside (5), and ferulic acid (6). Some products were not identified. HPLC analyses of the mixture of acylated pelargonidin isolated from red radish and AAPH revealed that the acylated pelargonidins possess the radical scavenging ability on some common sites even if the characteristics of the intramolecular acyl units are different. Degradation rates of acylated pelargonidins and the formation rates of the resulting reaction products were found to be quite different.  相似文献   
10.
There has been less concern about soil mineralogical alteration than about soil physical, chemical and biological changes induced by termite nest-building activity. Furthermore, much less attention has been paid to free sesquioxides than to phyllosilicate minerals. In the present study, we conducted field morphological observations and selective dissolution analysis to characterize free sesquioxides in termite (Macrotermes bellicosus) mounds as compared with surrounding pedons in different toposequence positions, i.e., seasonally flooded valley bottom, hydromorphic fringe and well-drained upland sites. Distinctive redoximorphic features, such as surface yellowish layers on mound structures from the fringe site, indicate possible alteration of iron sesquioxide forms in the mounds due to the transportation of soil from reductive (aquic subsoil) to oxidative (epigeal mound) environments by the nest-building activity of M. bellicosus. On the other hand, the iron-soluble content in the dithionite-citrate-bicarbonate (DCB) system (Fed) was generally higher in the mound structures than at the adjacent sub-surface (Ap2) horizon at each toposequence position, while there was less difference in the content of acid ammonium oxalate (AAO) extractable iron (Feo) as compared to Fed. As a consequence, the iron activity index (Fed/Feo ratio) was found for the most part to be lower in the mound structures than in the neighboring Ap2 horizon. In addition, the content of Fed, AAO-soluble Al (Alo) and DCB-extractable Al (Ald) was significantly correlated with clay content in these soils. These findings suggest that M. bellicosus preferentially collects clay particles, probably from the clay-rich subsoils, such as the argillic horizon, which has been formed by the co-migration of phyllosilicate minerals and relatively crystalline sesquioxides. The species then likely incorporates them into the mounds, which induces an increase in the Fed content relative to that of Feo, resulting in a decreased iron activity index in the mound structures.  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