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   195篇
  免费   0篇
  国内免费   1篇
农学   1篇
  25篇
综合类   4篇
农作物   1篇
水产渔业   45篇
畜牧兽医   105篇
植物保护   15篇
  2022年   2篇
  2021年   21篇
  2020年   2篇
  2017年   1篇
  2016年   1篇
  2015年   20篇
  2014年   16篇
  2013年   14篇
  2012年   3篇
  2011年   7篇
  2010年   9篇
  2009年   9篇
  2008年   9篇
  2007年   16篇
  2006年   11篇
  2005年   4篇
  2004年   8篇
  2003年   17篇
  2002年   11篇
  2001年   2篇
  2000年   1篇
  1999年   2篇
  1998年   3篇
  1997年   1篇
  1996年   1篇
  1995年   1篇
  1994年   2篇
  1993年   1篇
  1991年   1篇
排序方式: 共有196条查询结果,搜索用时 703 毫秒
31.
[Objective] The dormancy characteristics of Malus ‘Snowdrift’ in long-day treatment were studied, and 6-BA was used to break the dormancy, with the aim to achieve the purpose of flowering in autumn. [Method] The new shoots of ‘Snowdrift’ in long-day treatment were conducted with hydroponics to investigate their dormancy time. And cytokinin 6-benzyladenine(6-BA)was used to treat the dormant shoots, to investigate the budding, flowering and flower bud differentiation. [Result] The shoots in long-day treatment entered endodormancy after August 7~(th) and the shoots in the natural daylight entered endodormancy before July 18~(th). In long-day treatment, 116 buds, 198 flowers were observed after 6-BA spraying. [Conclusion] The optimum concentration of 6-BA was 300 mg/L. And the flower bud differentiation of ‘Snowdrift’ in long-day treatment was faster than those in natural daylight after 6-BA spraying.  相似文献   
32.
Myostatin (MSTN) is a negative regulator during muscle differentiation, whereas insulin‐like growth factors (IGFs) are essential for muscle development. MSTN and IGFs act oppositely during myogenesis, but there is little information on the mutual relationship of MSTN and IGFs. The present study was conducted to examine whether MSTN affects IGF expression during early myogenesis in cattle. IGF‐1 mRNA was similarly expressed in M. longissimus thoracis of double‐muscled (DM) and normal (NM) Japanese shorthorn cattle. IGF‐2 mRNA expression was consistently higher in the normal and regenerating muscle of DM cattle than those of NM cattle. When myoblasts were isolated from regenerating M. longissimus thoracis, IGF‐2 mRNA expression showed a significant increase in differentiating DM derived myoblasts (DM‐myoblasts) as compared with differentiating NM derived myoblasts (NM‐myoblasts). An addition of recombinant mouse myostatin (rMSTN) to myoblast cultures attenuated IGF‐2 mRNA expression and decreased myotube formation, but did not effect IGF‐1 mRNA expression. An activin‐like kinase (ALK) inhibitor, SB431542, mediates MSTN action, suppressed the translocation of Smad2/3 into the nucleus in DM‐myoblasts, and restored the attenuated IGF‐2 mRNA expression and the decreased myotube formation induced by rMSTN in myoblast cultures. The findings indicate that MSTN may negatively regulate myoblast differentiation by suppressing IGF‐2 expression via ALK‐Smad signaling.  相似文献   
33.
Our previous study detected a single nucleotide polymorphism (SNP), g.1471620G > T , in the 5' flanking region of the endothelial differentiation sphingolipid G-protein-coupled receptor 1 ( EDG1 ) gene, which has been considered as a positional functional candidate for the gene responsible for marbling, and showed association of the g.1471620G > T SNP with marbling in Japanese Black beef cattle. In the present study, we investigated the allele frequency distribution of the g.1471620G > T SNP among the 5 cattle breeds, Japanese Black, Japanese Brown, Japanese Short Horn, Holstein, and Brown Swiss breeds. The T allele at the g.1471620G > T SNP associated with high marbling was found at high frequency in Japanese Black breed that has been subjected to a strong selection for high marbling, while the allele was absent or at very low frequencies in the other breeds that have not been strongly selected for high marbling. Based on this finding, we hypothesized that the pressure of the strong selection for high marbling in Japanese Black breed has increased the frequency of the T allele at the g.1471620G > T SNP in the EDG1 .  相似文献   
34.
东汉末年的荆州,兴起了具有与此前儒教不同特点的新儒教-荆州学。它的形成不仅缘于宋忠、綦毋闿等刘表集团的内部成员,同时也包括了司马徽、庞德公等在野的名士。在这样广泛的交友关系中成立的荆州学到底具有怎样的特征。又是为何诞生于荆州?修习了荆州学的诸葛亮在刘备处仕官,最终在蜀汉建国过程中起到了重大作用。荆州学又在诸葛亮的思想里占据了怎样的地位?此外,在经学上师承宋忠的王肃对汉代经学的集大成者郑玄进行了全面的否定和批判。荆州学是经过了怎样的演变才出现了王肃反郑的现象?  相似文献   
35.
36.
A study of common minke and Bryde's whales was conducted in the western North Pacific in the 2000 and 2001 summer seasons to estimate prey selection of cetaceans as this is an important parameter in ecosystem models. Whale sighting and sampling surveys and prey surveys using quantitative echosounder and mid‐water trawl were carried out concurrently in the study. Biomasses of Japanese anchovy, walleye pollock and krill, which were major prey species of common minke and Bryde's whales, were estimated using an echosounder. The results suggested that common minke whale showed prey selection for Japanese anchovy while they seemed to avoid krill in both the offshore and coastal regions and walleye pollock in the continental shelf region. Selection for shoaling pelagic fish was similar to that in the eastern North Atlantic. Bryde's whale showed selection for Japanese anchovy in August 2000 and July 2001, while it showed prey selection for krill in May and June in 2001.  相似文献   
37.
ABSTRACT:   Because blood vitellogenin (Vg) has been considered a biomarker for environmental estrogens, the basal levels of Vg and 17β-estradiol (E2) were determined in male Japanese whiting reared under natural conditions. Serum levels of Vg and E2 were measured and gonadal development was assessed by gonadosomatic index (GSI) and histological observation in 8–10 male fish at monthly intervals throughout the annual reproductive cycle. Serum E2 was <60 pg/mL throughout the study period. In contrast, serum Vg exhibited seasonal changes: serum levels of Vg gradually increased from April to May (mean 63 ± 13 ng/mL and 124 ± 48 ng/mL in April and May, respectively), and then reached a peak value (mean 352 ± 68 ng/mL) in June. Thereafter, serum Vg gradually decreased, reaching undetectable levels (<50 ng/mL) in October. Serum levels of Vg tended to increase in the male fish in which the GSI was >1%. Histological observation revealed that testes in such male fish were in active spermatogenesis and then all of the testes of male fish in which serum Vg decreased to ND levels were regressed. These results suggest that Vg productive potency (sensitivity to estrogens) may increase in the spermatogenic stage, resulting in production of Vg in response to very low levels of natural or xenobiotic estrogens.  相似文献   
38.
Myostatin (MSTN), known as growth and differentiation factor 8 (GDF-8), is a member of the transforming growth factor β (TGF-β) superfamily that negatively regulates skeletal muscle mass. Myostatin binds with high affinity to the receptor serine threonine kinase activin receptor type IIB (ActRIIB). Activins that also belong to the TGF-β superfamily, stimulate follicle-stimulating hormone production in gonadotrophs and suppress growth hormone and adrenocorticotropic hormone production in somatotrophs and corticotrophs, respectively. The aim of the present paper was therefore to clarify the endocrine action of MSTN in adenohypophysis. The present study details the expression and cellular localization of MSTN and ActRIIB in porcine anterior pituitary gland. The mRNA of MSTN and ActRIIB was consistently expressed in RT-PCR. Immunohistochemistry of MSTN and specific hormones showed that MSTN localized in thyrotrophs and gonadotrophs, in which most of the MSTN immunoreactive cells were identified as thyrotrophs. The immunostaining of ActRIIB was restricted to corticotrophs. These results indicate that MSTN was mainly produced in thyrotrophs and its receptor, ActRIIB, was restrictively contained in corticotrophs. Interestingly, thyrotrophs immunoreactive for MSTN were frequently close to corticotrophs immunoreactive for ActRIIB. The present study suggests that MSTN from thyrotrophs may regulate corticotroph function as a paracrine mediator among the porcine anterior pituitary cells.  相似文献   
39.
40.
Several epiphytic strains of Enterobacter cloacae isolated from mulberry leaves were resistant to antibiotics such as streptomycin, kanamycin, ampicillin, tetracycline and chloramphenicol, and harbored a 100-kb plasmid designated pMUL1. Plasmid profile analysis of spontaneous mutants derived from Ent. cloacae MUL1 and MUL1 (RSF1010) suggested that pMUL1 confers resistance to multiple antibiotics. Southern blot analysis using probes of five antibiotic-resistance genes against EcoRI-digested DNA from pMUL1 and defective pMUL1s (mutants) revealed that all these genes were located within a 24-kb region of pMUL1 and that some genes were assigned to the defective plasmids. A similar antibiotic-resistance plasmid was detected in several orchid-pathogenic strains of Ent. cloacae, but not in the type-culture strain (JCM 1232) or strains of Ent. cloacae of insect-origin. Strains MUL1 and MUL1 (RSF1010) were then mated with epiphytic Erwinia spp. and Pseudomonas spp. on filters, respectively. Several recipient strains of epiphytic Er. herbicola simultaneously acquired plasmid pMUL1 and the phenotype of multiple-antibiotic resistance. Thus, pMUL1 was verified to be conjugative and to encode genes for multiple-antibiotic resistance, including genes homologous to the strA-strB of the nonconjugative IncQ plasmid RSF1010. These findings suggest that epiphytic Ent. cloacae may play a role in the dissemination of antibiotic-resistance genes among epiphytic bacteria and plant pathogenic bacteria. Received 10 January 2002/ Accepted in revised form 29 March 2002  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