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   168篇
  免费   7篇
林业   15篇
农学   1篇
  28篇
综合类   4篇
农作物   7篇
水产渔业   35篇
畜牧兽医   61篇
园艺   2篇
植物保护   22篇
  2023年   1篇
  2021年   5篇
  2018年   4篇
  2017年   2篇
  2016年   5篇
  2015年   9篇
  2014年   7篇
  2013年   21篇
  2012年   5篇
  2011年   12篇
  2010年   8篇
  2009年   9篇
  2008年   10篇
  2007年   8篇
  2006年   8篇
  2005年   7篇
  2004年   8篇
  2003年   14篇
  2002年   8篇
  2001年   5篇
  2000年   6篇
  1999年   3篇
  1998年   1篇
  1996年   1篇
  1995年   1篇
  1992年   2篇
  1991年   3篇
  1990年   1篇
  1977年   1篇
排序方式: 共有175条查询结果,搜索用时 15 毫秒
41.
42.
The catabolism of arginine (Arg) by mixed rumen bacteria (B), mixed rumen protozoa (P), and their mixture (BP) was quantitatively investigated in an in vitro system in order to confirm the metabolic pathway of Arg and provide basic information for enzymatic and molecular studies as well as an understanding of the quantitative distribution of metabolites. Rumen microbial suspensions (B, P, and BP) collected from fistulated goats were anaerobically incubated with or without 1 mmol/L Arg at 39°C for 12 h. Arg and other related compounds such as citrulline (Cit), ornithine (Orn), proline (Pro) and 5‐aminovaleric acid (5AV) in both supernatant and hydrolyzates of B, P, and BP suspensions were analyzed by HPLC. The metabolic pathways of Arg in mixed rumen bacteria and mixed rumen protozoa were considered to be as follows: rumen bacteria, Arg → Cit → Orn → Pro → 5AV → VFAs + NH3; rumen protozoa, Arg → Cit → Orn → Pro → 5AV. The disappearance of Arg (1 mmol/L) was approximately 52.9 and 88.2% in B, 33.9 and 55.6% in P, and 52.8 and 85.2% in BP during 6 and 12 h incubations, respectively. When expressed in units of ‘per gram (g) of microbial nitrogen (MN)’, the net degradation rate of Arg in BP (50.3 µmol/g MN/h) was approximately 46% lower than that of B during a 12 h incubation period. The presence of protozoa tended to inhibit the production of Orn from Cit and the production of 5AV from Pro which were thought to be rate‐limiting steps of Arg metabolism in rumen microorganisms. As a result, protozoa appeared to have a saving effect on Arg metabolism, that is, protozoa protected Arg from wasteful exhaustion in the rumen.  相似文献   
43.
The effect of the endocrine-disrupting chemical 3,3',4,4',5-pentachlorobiphyenl (PCB 126) on intestinal microbiota after oral administration, and the improvement of intestinal microbiota and feces quantity by the subsequent administration of Lactobacillus acidophilus or Lactobacillus reuteri was investigated. All the rats were given 100 μg/kg bodyweight of PCB 126. The changes in bacterial counts were confirmed using a culture method. The administration of PCB 126 tended to decrease the bacterial counts of lactobacilli (109.6−1010.2 to 108.8−109.2) and bifidobacteria (105.3−106.1 to 103.6−104.2), and to increase those of Enterobacteriaceae (108.2−109.1 to 109.4−1010.3) and staphylococci (106.6−107.4 to 107.2−108.4) compared to no PCB 126 administration. After administration of PCB 126, L. acidophilus or L. reuteri orally administered to rats caused Enterobacteriaceae and staphylococci counts to decrease, suggesting that the intestinal microbiota was improved by the lactobacilli. The administration of L. acidophilus and L. reuteri improved the balance of intestinal microbiota, and defecation volume returned to its normal level. L. acidophilus and L. reuteri have a remedial effect on intestinal microbiota affected by PCB 126 and can function to lessen accumulated PCB 126 volume.  相似文献   
44.
The objective of this study was to confirm the stability of the genetic estimation of longevity of the Holstein population in Japan. Data on the first 10 lactation periods were obtained from the Livestock Improvement Association of Japan. Longevity was defined as the number of days from first calving until culling or censoring. DATA1 and DATA2 included the survival records for the periods 1991–2003 and 1991–2005, respectively. The proportional hazard model included the effects of the region-parity-lactation stage-milk yield class, age at first calving, the herd–year–season, and sire. The heritabilities on an original scale of DATA1 and DATA2 were 0.119 and 0.123, respectively. The estimated transmitting abilities (ETAs) of young sires in DATA1 may have been underestimated, but coefficient δ, which indicated the bias of genetic trend between DATA1 and DATA2, was not significant. The regression coefficient of ETAs between DATA1 and DATA2 was very close to 1. The proportional hazard model could steadily estimate the ETA for longevity of the sires in Japan.  相似文献   
45.
This article describes the catalytic effect of NaHCO3 on condensation reactions of monomeric hydroxymethylphenols (HMPs) to elucidate the cure-acceleration mechanism. By comparison of the kinetics of self-condensations of HMPs, NaHCO3 was proved to increase the reactivity of para-hydroxymethyl groups. The changes of 13C nuclear magnetic resonance (NMR) chemical shifts on each HMP system with the additive indicated that the addition of NaHCO3 enhanced some molecular interactions between HMPs and NaHCO3, facilitating a resonance effect that might play a similar role in dissociation of the phenolic hydroxyl groups of HMPs. In addition, computational modeling by molecular orbital calculations elucidated that hydrogen carbonate anion (HCO 3 ) forms an interaction between either the para-hydroxymethyl group and the phenolic hydroxyl group or between the two para-hydroxymethyl groups of HMPs by hydrogen bonds. From the experimental results, the authors proposed the mechanism of the catalytic action of NaHCO3: it appears to be due to the delocalization of an electron initiated by the interaction of the para-hydroxymethyl groups and the phenolic hydroxyl of HMPs with HCO 3 through hydrogen bonds, which results in facilitating the formation of active species.  相似文献   
46.
A female stillborn Holstein calf with shortened cervical and thoracic regions, protrusion of the tongue, and bilateral symmetric flexural contraction of the anterior limbs was delivered on gestation day 281. Multiple hemivertebrae, fused and misshaped vertebrae, synostosis and scoliosis of cervical, thoracic and lumbar vertebral column were found in the affected calf by radiographic and computed tomographic (CT) analysis. Ten pairs of ribs were present and the sternum consisted of 9 sternebrae. Multiple morphologic abnormalities including fusion, malformation, and displacement, were found in the ribs and sternum. Cardiac anomalies, including atrial septal defect and hypertrophy of right ventricle, were observed. DNA-polymerase chain reaction (PCR) analysis demonstrated that amplified product from the liver DNA of the affected calf had identical pattern to that associated with complex vertebral malformation (CVM) of Holstein calves and that her dam was a heterozygous carrier of CVM. The affected calf was diagnosed as having CVM based on the DNA-PCR results and the characteristic findings, and was recorded as a first documentation of CVM confirmed in a Holstein calf in Japan.  相似文献   
47.
G8 bovine group A rotaviruses isolated in Japan were genetically and serologically characterized. The VP7 gene nucleotide and amino acid sequences revealed high identity with each other. All Japanese G8 strains were classified into the same lineage in the phylogenetic analysis based on VP7 gene sequences. Antisera to four Japanese G8 strains neutralized other G8 strains, but their neutralizing titers were between 8-fold lower and 2-fold higher than homologous strains. These results suggest that the VP7s of Japanese G8 strains have similar genetic and serologic characteristics. Observed differences in the neutralizing abilities of antisera for each strain appear to depend on differences in the P serotypes/genotypes.  相似文献   
48.
We determined nearly the complete sequences of the 16S ribosomal RNA gene (rDNA) for Japanese strains of R. solanacearum. The comparison of 1471 nucleotide positions separated the Japanese strains into two groups, group 1 with biovars 1, 2, 3 and 4 strains which belonged to race 1, and group 2 with biovar 2 strains corresponding to race 3. Group 1 strains all had identical sequences, and strains representing the four biovars within the group did not differ from each other. Group 2 strains had characteristic nucleotides which differed at seven positions from group 1 strains. Comparative analysis of Japanese and foreign strains based on 16S rDNA sequences showed that Japanese group 1 was closely related to Asian and Australian biovars 3, 4 and 5, and belonged to the known division 1. Japanese group 2 was homogeneous to Indonesian biovars 2 and N2 in subdivision 2b. Since the differences in the nucleotides corresponded to restriction sites for the AluI, RFLP analysis of PCR-amplified 16S rDNA efficiently differentiated not only Japanese group 1 from group 2, but also differentiated three types of foreign strains which differed in biovar and geographic origin. Received 26 July 1999/ Accepted in revised form 19 November 1999  相似文献   
49.
弱光照射和无机营养供给对冷藏绿芦笋品质变化的影响   总被引:9,自引:0,他引:9  
绿芦笋嫩茎基部切口插入含有N、P、K营养的琼脂凝胶中 ,在 (6± 0 2 )℃下贮藏。贮藏期间 ,分别以有效光量子束密度 (PPFD)为 2 μmol·m-2 ·s-1的红色发光二极管和白色荧光灯作为弱光源 ,每天 2 4h连续照射绿芦笋 2 1d。结果表明 ,红光和白光对冷藏绿芦笋品质的保持具有相似的效果。供给无机营养的处理在红光或白光照射下 ,色值 (a 和ΔE ab)变化率、粗纤维含量增长率和可溶性固形物减少率为最低 ,其次是无营养供给的红光或白光处理 ,以黑暗处理为最高 ;供给无机营养处理的芦笋嫩茎伸长率大于无营养处理的 ;光线照射与否和无机营养供给有无与芦笋失重率之间无明显相关性  相似文献   
50.
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