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   563篇
  免费   25篇
林业   34篇
农学   15篇
  95篇
综合类   36篇
农作物   22篇
水产渔业   98篇
畜牧兽医   237篇
园艺   6篇
植物保护   45篇
  2023年   3篇
  2022年   7篇
  2021年   11篇
  2020年   11篇
  2019年   11篇
  2018年   10篇
  2017年   13篇
  2016年   23篇
  2015年   23篇
  2014年   18篇
  2013年   28篇
  2012年   36篇
  2011年   45篇
  2010年   24篇
  2009年   20篇
  2008年   45篇
  2007年   33篇
  2006年   47篇
  2005年   37篇
  2004年   31篇
  2003年   32篇
  2002年   23篇
  2001年   13篇
  2000年   11篇
  1999年   2篇
  1998年   4篇
  1996年   2篇
  1995年   3篇
  1994年   1篇
  1992年   3篇
  1991年   4篇
  1990年   2篇
  1989年   3篇
  1988年   2篇
  1985年   1篇
  1975年   1篇
  1974年   1篇
  1971年   1篇
  1970年   2篇
  1966年   1篇
排序方式: 共有588条查询结果,搜索用时 15 毫秒
21.
A total of 267 fecal and serum samples collected from individual pigs reared on a Salmonella-positive farm were subjected to bacteriological and serological examinations of Salmonella. Salmonella was isolated from 47 pigs (17.6%) and prevalence of antibody to lipopolysaccharide (LPS) of S. Typhimurium, which was partly common to S. O4, 12: d: -, was observed in 90 pigs (33.7%). Salmonella was isolated from 26 (28.9%) of 90 antibody-positive pigs and 21 (11.9%) of 177 antibody-negative pigs. Twenty-one of 36 pigs (58.3%) positive for S. O4, 12: d: -, five of 10 pigs (50.0%) positive for S. Havana, and none for S. Anatum had antibodies. Thus, seropositive rates were higher than isolation-positive rates, and antibody prevalence was associated with serovars of the isolates. Then, we analyzed antibody prevalence among pigs on Japanese pig farms. The antibodies to LPS of S. Typhimurium were found in 195 of 1,498 pigs (13.0%) and in at least one serum sample on 35 of 52 farms (67.3%). Our results indicate that Salmonella does not seem to be so prevalent in pigs though it is widely prevalent among pig farms.  相似文献   
22.
The masticatory muscles and their related structures of the skull were observed in the Indian gavial (Gavialis gangeticus), the false gavial (Tomistoma schlegelii), and the African slender-snouted crocodile (Mecistops cataphractus) to detail some morphological differences in comparison with the other crocodile species, and to compare and elucidate the functional strategy of themasticatory apparatus in these long-snouted species. The Musculus pterygoideus posterior was relatively smaller in the three species compared with many short-snouted crocodiles. It suggests that the masticatory power in fish-eating long-snouted species is not so high as in the short-snouted crocodiles, while the masticatory muscles were morphologically different among the three long-snouted species as follows. The M. pterygoideus posterior of the false gavial was extended in the lateral side of the lower jaw unlike the Indian gavial. The M. pseudotemporalis and the Fenestra supratemporalis were largely developed in the Indian gavial, however we suggest that the other two species possess the weak bundles in this muscle. The false gavial and the African slender-snouted crocodile have the pterygoid bone well-developed extending dorso-ventrally and it is suggested that the M. adductor mandibulae posterior attached to the pterygoid bone may be much larger than the Indian gavial. These data morphologically clarify the masticatory mechanism in the long-snouted crocodiles different from the short-snouted species, and demonstrate that the evolutional strategy to share the functional role in the masticatory muscles have been differently established between the Indian gavial and the other two species. We also obtained the morphological data in the fossil skull of the Machikane crocodile (Toyotamaphymeia machikanense) and concluded from the fossil characters that the considerable developments of the M.pterygoideus posterior and the M.pseudotemporalis in this species had not morphologically been consistent with both the Indian and false gavials.  相似文献   
23.
24.
The entire genome of bacteriophage OP1, lytic for Xanthomonas oryzae pv. oryzae causing bacterial leaf blight of rice, and the partial genomes of related phages were sequenced and analyzed. The OP1 genome comprises double-stranded, 4785-bp long DNA with 51.1% G + C content. Fifty-nine open reading frames (ORFs) were detected. ORF25 had similarity with the tail fiber gene of phages, whose product is related to host specificity. The ORF25 regions were amplified from four host-range mutants (OP1h, OP1hC, OP1h2, and OP1h2C) by polymerase chain reaction, and their deduced amino acid sequences were compared. Three mutants (OP1hC, OP1h2, OP1h2C) had duplications of a small domain in the N-terminal portion, although there were slight differences in the position of the duplicated sequences. One mutant OP1h had substituted amino acids in the duplication region. New mutants isolated in the laboratory (OP1hC and OP1h2C from OP1 and OP1h2) acquired the ability to lyse strain N5874 belonging to phagovar (lysotype) C. However, they rapidly lost this lytic ability when incubated with other phagovars. This loss was always accompanied by a loss of the characteristic repeats, suggesting that the host range of OP1-related phages changed mainly through duplication and deletion of a small domain in ORF25. The nucleotide sequence data reported are available in the DDBJ/EMBL/GenBank databases under the accession numbers AP008979, AB214312 to AB214316  相似文献   
25.
Transencapsidation of the Rice gall dwarf virus (RGDV) inner core by the Rice dwarf virus (RDV) outer capsid P8 protein was examined in vitro and in planta. When RGDV core particles were incubated with an extract from RDV P8-transgenic rice leaf tissue, RDV P8 encapsidated the RGDV core particles to form double-shelled virus-like particles in vitro. In contrast, when RDV P8-transgenic rice plants were inoculated with RGDV, progeny RGDV particles contained RGDV P8 but RDV P8 was not detectable in the virions. No significant differences were found in acquisition by the vector insects and subsequent transmission rates between RGDV infecting nontransgenic rice plants and those infecting RDV P8-transgenic rice plants. These results indicate that mechanisms of and/or requirements for interactions between P8 and the inner core particles of phytoreoviruses differ between in vitro and in planta.  相似文献   
26.
When the conidia of Blumeria graminis f. sp. hordei (Bgh) are inoculated on barley coleoptile cells they produce short germ tubes called primary germ tubes (PGTs) about 2 h after inoculation. We evaluated the positive role of a PGT in inducing accessibility of the host cell under the germ tube. When an appressorium (APP) penetrated the same cell on which a PGT was present, the ratio of haustorium formation (penetration efficiency) was significantly higher than when an APP penetrated the cell adjacent to the one on which a PGT was present. When an APP penetrated the cell laterally adjacent to the one on which a PGT was present we killed the cell under the PGT by puncturing it with a microneedle and then investigated the penetration efficiency of the cell adjacent to the dead cell. As a control we killed the cell longitudinally adjacent to the one on which a PGT was present and investigated the penetration efficiency of the laterally adjacent cell. The results showed that the penetration efficiency of the former was significantly lower than that of the latter. This suggests that some accessibility factor might transfer from a cell on which a PGT is present to a laterally adjacent cell. The existence of a conidium body but not a PGT was not effective for induced accessibility of the host cell. Moreover, when a Bgh germling was removed 6 h after inoculation and another germling was transferred to the same cell, the penetration efficiency was significantly higher than that of control. As a control, a Bgh germling was transferred to a cell on which no germling was present. These results suggest that the existence of PGT is effective for induced accessibility of a host cell when penetrated by Bgh. However, it is unclear whether or not a PGT secretes some substance(s) which suppresses the resistance induction of a host cell.  相似文献   
27.
ABSTRACT:   Age and growth of alfonsino Beryx splendens (Lowe) were studied using counts of presumed daily incremental growth rings on the transverse section of otoliths of fish collected from the Kanto District, central Japan. Microstructural growth increments were observed from the core to the outermost margin of the broadest of approximately 50 branches formed on the surface of an otolith. Of 98 otoliths examined, 46 were readable. The number of increments and fish lengths ranged from 448 (218 mm fork length [FL]) to 3701 (411 mm FL). The ages of these fish were estimated to be 1 year, 2 months and 10 years, 2 months, respectively, assuming that an increment was formed daily. The von Bertalanffy growth equation combined for males and females was expressed as follows: L t  = 542 {1 −  exp  [−0.133( t  + 2.00)]}, where L t is fork length (mm) at yearly age t . The results of the present study were compared with those of other researchers who had studied alfonsino from central Japan.  相似文献   
28.
29.
The Standard for the Exchange of Nonclinical Data (SEND), adopted by the US FDA, is part of a set of regulations and guidances requiring the submission of standardized electronic study data for nonclinical and clinical data submissions. SEND is the nonclinical implementation of SDTM (Study Data Tabulation Model), the standard electronic format for clinical regulatory submissions to FDA. SEND, SDTM, and the associated Controlled Terminology have been developed by CDISC (Clinical Data Interchange Standards Consortium). In order to successfully implement SEND, interdisciplinary contributions between sponsors and CROs, need a model for task allocation. This is being undertaken by the Pharmaceutical Users Software Exchange (PhUSE). Because SEND is currently the preferred submission format of the US FDA only and will become required by it starting in December 2016, only American academic societies and companies are actively involved. An exception to this is the INHAND initiative, which leads the way in standardizing terminology for toxicological pathology. On the other hand, international globalization of other clinical and nonclinical practices is not feasible because there are substantial differences between the US and non-US countries in CRO involvement in drug development. Thus, non-US countries must consider and develop approaches to SEND that meet their needs. This paper summarizes the activities of the major organizations involved in SEND development and implementation, discusses the effective use of SEND, and details a compliance scheme (research material of the Showa University School of Medicine) illustrating how pharmaceutical companies can complete a large amount of work up to an FDA application with the effective utilization of CROs and solution providers.  相似文献   
30.
Canine melanoma is one of the most important diseases in small animal medicine. Protein phosphatase 2A (PP2A), a well conserved serine/threonine phosphatase, plays a critical role as a tumor suppressor. SET/I2PP2A is an endogenous inhibitor for PP2A, which directly binds to PP2A and suppresses its phosphatase activity. Elevated SET protein levels have been reported to exacerbate human tumor progression. The role of SET in canine melanoma, however, has not been understood. Here, we investigated the potential therapeutic role for SET inhibitors in canine melanoma. The expression of SET protein was observed in 6 canine melanoma cell lines. We used CMeC-1 cells (primary origin) and CMeC-2 cells (metastatic origin) to generate cell lines stably expressing SET-targeting shRNAs. Knockdown of SET expression in CMeC-2, but not in CMeC-1, leads to decreased cell proliferation, invasion and colony formation. Phosphorylation level of p70 S6 kinase was decreased by SET knockdown in CMeC-2, suggesting the involvement of mTOR (mammalian target of rapamycin)/p70 S6 kinase signaling. The SET inhibitors, OP449 and FTY720, more effectively killed CMeC-2 than CMeC-1. We observed PP2A activation in CMeC-2 treated with OP449 and FTY720. These results demonstrated the potential therapeutic application of SET inhibitors for canine melanoma.  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