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   159篇
  免费   8篇
  国内免费   1篇
林业   15篇
农学   8篇
  10篇
综合类   10篇
农作物   4篇
水产渔业   23篇
畜牧兽医   89篇
园艺   1篇
植物保护   8篇
  2022年   3篇
  2021年   13篇
  2020年   1篇
  2019年   3篇
  2018年   3篇
  2017年   9篇
  2016年   7篇
  2015年   6篇
  2014年   9篇
  2013年   7篇
  2012年   8篇
  2011年   10篇
  2010年   6篇
  2009年   7篇
  2008年   8篇
  2007年   3篇
  2006年   2篇
  2005年   4篇
  2004年   3篇
  2003年   12篇
  2002年   11篇
  2001年   9篇
  2000年   6篇
  1999年   2篇
  1998年   2篇
  1996年   1篇
  1992年   2篇
  1991年   2篇
  1990年   1篇
  1989年   2篇
  1984年   2篇
  1981年   2篇
  1979年   1篇
  1966年   1篇
排序方式: 共有168条查询结果,搜索用时 31 毫秒
151.
The objective of this study is to clarify the relationships between tree sizes and the anatomical, chemical, and physical characteristics of reaction wood. Naturally inclined stems or branches in 23 Japanese angiosperms, including 3 tree sizes at adult trees, 7 arbor, 7 subarbor, and 9 shrub species, were used. The presence of a gelatinous (G-) layer, basic density, vessel frequency, and lignin content were examined on the upper and lower sides of each sample. Almost all the species showed a decrease in vessel frequency and lignin content on the upper side, which are typical characteristics of reaction wood in angiosperms. A G-layer was formed in four arbor, one subarbor, and two shrub species. The ratio of the upper and lower sides in vessel frequency and lignin content gradually decreased with an increase in tree size. Based on the results of the principal component and cluster analyses, shrub species were classified into the different groups: from arbor and subarbor groups. These results indicate that the magnitude of alteration in the characteristics due to reaction wood formation of arbor and subarbor might differ from that of shrub, although the characteristics changed by reaction wood formation might be the same in the three tree sizes at adult trees.  相似文献   
152.
Chimeric simian and human immunodeficiency viruses (SHIVs) are useful tool for investigating AIDS pathogenesis and for development of vaccine. We constructed a SHIV-vpr vector (designated as SHIV-3sj) by replacing vpr region with restriction enzyme sites. SHIV-3sj was designed to express inserted gene along with its viral replication. Five cytokine genes were inserted into SHIV-3sj, and ability of viral replication and expression of the inserted genes were examined. The short insert including RANTES and IL-5 resulted in the successful expression from SHIV-3sj, while the construct having longer genes including IL-2, IL-6 and IL-12p35 failed to become replication competent. These results suggest that the length of the insert is an important factor for the replication ability of SHIV-3sj vector.  相似文献   
153.
The prevalence of Cryptosporidium infection was examined in 480 healthy cattle (0-39 months old) in the Tokachi district in Hokkaido during the period from June to September in 2000 and from June to July in 2001. C. parvum oocysts were detected in 6 of 50 cattle (0-2 months old) in 2001; while C. muris was detected in 2 of 56 cattle (6-8 months old) in 2001, in 1 of 15 cattle (9-11 months old) in 2001, in 1 of 88 cattle (15-17 months old) in 2000, in 4 of 89 cattle (18-21 months old) in 2000 and in 2 of 53 cattle (21-23 months old) in 2000.  相似文献   
154.
Lactoferrin (LF), a member of the transferrin (TF) protein family, is an iron-binding protein that is known to interact with bacteria through a specific receptor. We examined the binding of bovine LF (bLF), bovine TF (bTF), and ovotransferrin (OTF) by Toxoplasma gondii using a fluorescence test and the streptavidin-biotin (SAB) method using biotin-streptavidin, and found that bLF, bTF, and OTF bound to the protein components of T. gondii. Furthermore, we confirmed that bLF, bTF, and OTF bound a 42 kDa soluble protein of T. gondii by far Western blot method. These results demonstrated that bLF binding proteins are present on T. gondii.  相似文献   
155.
Neospora caninum is a veterinary medically important pathogen capable of causing abortion in cattle and neuromuscular paralysis in dogs. The surface antigen 1 of N. caninum (NcSAG1) is an important candidate for the development of a diagnostic reagent for neosporosis. In order to establish an effective diagnostic method, the gene encoding truncated NcSAG1 (NcSAG1t) lacking a signal peptide and C-terminal hydrophobic regions was cloned and expressed in Escherichia coli as a fusion protein with glutathione S-transferase (GST). The purified GST-NcSAG1t was tested in an enzyme-linked immunosorbent assay (ELISA) for the detection of N. caninum antibodies in cattle. The ELISA with GST-NcSAG1t clearly differentiated between immunofluorescent antibody test (IFAT)-positive and -negative sera from cattle. In addition, the ELISA detected no cross-reactivity with sera from mice experimentally infected with the closely related parasite Toxoplasma gondii. Field serum samples collected from cattle in Brazil were examined for the diagnosis of neosporosis by using the ELISA. Of the 197 samples analyzed, 66 (33.5%) samples were positive for antibodies to N. caninum. Of the 66 ELISA-positive samples, 60 (90%) samples were confirmed as positive by Western blot analysis with whole parasite antigens. These results suggest that the recombinant NcSAG1t could be a reliable reagent for use as an antigen in ELISA for the serodiagnosis of N. caninum infection in cattle.  相似文献   
156.
Babesia caballi merozoites were prepared by combining two improved methods of cultivation and purification of merozoites using Percoll-gradiation, and the protein compositions of merozoites were analyzed by two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting. The relative molecular masses of the major proteins and protein masses separated by electrophoresis were >94, 80-70, 50-45, 34-30, 30-28 and 18 kDa. By Western blotting, twelve proteins or protein groups were recognized by pooled sera from two horses experimentally infected with B. caballi. Among twelve proteins, five new proteins (54, 30-26, 24, and two 18 kDa) were identified, and the 48 kDa protein was revealed to consist of 2 components in the B. caballi merozoite. One protein (54 kDa) of B. caballi was also recognized by the pooled sera from two horses experimentally infected with B. equi.  相似文献   
157.
158.
Growth characteristics [stem diameter (D), tree height (H), and bole volume (V)], stress-wave velocity (SWV), and Pilodyn penetration (P) were measured for 21 seed provenances of 24-year-old teak trees planted in Indonesia to characterize variation in tree growth characteristics, SWV, and P among seed provenances. Broad-sense heritability and correlations between the measured characteristics were also determined. Significant differences for all measured characteristics were observed among provenances, indicating that these characteristics are genetically controlled. Broad-sense heritabilities of growth characteristics, SWV, and P are moderate values. These results indicate potential for improving growth characteristics and wood properties of teak trees with the help of breeding programs. Highly significant positive correlations were observed among the growth characteristics, suggesting that they are closely related. In contrast, no significant correlations were observed between the growth characteristics and SWV, indicating that they are independent. We conclude that mechanical properties are also important criteria for selecting plus trees in tree breeding programs. Principal component analysis revealed that seed provenances from Indonesia (Bangilan, Deling, and Randublatung) and India (Malabar and Central Province) have high scores of growth characteristics and SWV.  相似文献   
159.
In Japan, selective thinning is a common thinning method, though line thinning receives much attention because of its economic merits. In this study, we examined effects of the two thinning methods on bird communities in Todo fir (Abies sachalinensis) plantations in Hokkaido, Japan. We surveyed bird species in forests under four different management types — unthinned, selectively thinned, line-thinned plantation, and naturally regenerated forest (here after referred to as natural forest) stands — using a line-transect method. We also investigated vegetation structure (canopy tree and understory) of these stands. Bird species richness did not differ between natural forests and plantations, while bird total abundance was greater in plantations than in natural forests. Bird species richness and total abundance were comparable among the three management types for plantations. Abundances of 10 bird species were different among the four management types, and five species were more abundant in line-thinned plantations. However, two species were more abundant in selectively thinned stands than in line-thinned stands, and they frequently appeared in natural forests. There were no distinct differences in vegetation structure among the management types for plantations. Our results suggest that line thinning could be beneficial for some bird species in plantations.  相似文献   
160.
ABSTRACT:   Stock structure of Japanese flounder Paralichthys olivaceus has been inferred mainly from either morphological or genetic analyses. However, because the results of both analyses did not always agree with each other, an inclusive conclusion has never been obtained. In this study, the stock structure has been inferred from both morphological and genetic analyses using 722 wild Japanese flounder collected from nine locations along the Japanese coast. The dorsal and anal fin ray counts were larger in the southern than in the northern populations. In total, 1041 bp of mitochondrial NADH dehydrogenase subunit-2 ( ND2 ) and 1830 bp of ND5 sequences were aligned. There are 578 variable sites in the concatenated sequence from the two genes, which defined a total of 490 haplotypes. Both results of morphological and genetic analyses indicated that the western Kyushu group, which included the Nagasaki and Kagoshima populations, was divided from the other seven populations. This is the first report to reveal the heterogeneity of the western Kyushu group based on statistical analysis.  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