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   247篇
  免费   4篇
  国内免费   2篇
林业   3篇
农学   1篇
基础科学   1篇
  28篇
综合类   9篇
农作物   1篇
水产渔业   43篇
畜牧兽医   154篇
植物保护   13篇
  2022年   17篇
  2021年   31篇
  2020年   7篇
  2019年   4篇
  2018年   3篇
  2017年   3篇
  2016年   7篇
  2015年   24篇
  2014年   19篇
  2013年   16篇
  2012年   6篇
  2011年   10篇
  2010年   6篇
  2009年   8篇
  2008年   14篇
  2007年   9篇
  2006年   10篇
  2005年   6篇
  2004年   10篇
  2003年   14篇
  2002年   13篇
  2001年   4篇
  2000年   3篇
  1998年   2篇
  1997年   1篇
  1996年   1篇
  1995年   2篇
  1994年   1篇
  1993年   1篇
  1953年   1篇
排序方式: 共有253条查询结果,搜索用时 15 毫秒
201.
Cytotoxic peptides were isolated from a trypsin digest of bovine αs1‐casein by a combination of ion‐exchange column chromatography and reversed‐phase high‐performance liquid chromatography as an indicator of cytotoxicity toward mouse spleen cells. Amino acids of the isolated peptides were sequenced as arginyl‐proly‐lysine, leucyl‐lysyl‐lysine and tyrosyl‐lysine, being compatible with sequences 1–3, 101–103 and 104–105 of bovine αs1‐casein, respectively. The isolated peptides displayed cytotoxicity toward healthy mouse T and B cells and human leukemic T and B cell lines in a commercially available serum‐free medium for lymphocytes, Celgrosser‐P, and were named α‐casecidins. Similar cytotoxicity was confirmed in chemically synthesized peptides corresponding to sequences 1–3, 101–103 and 100–105 of bovine αs1‐casein. The cytotoxicity induced by α‐casecidins was concluded to be because of necrosis, and was diminished in the presence of bovine serum albumin.  相似文献   
202.
The effects of early initiation of first service for dairy heifers on their fertility and productivity up to the third lactation were examined under constant raising and management conditions. Eight Holstein heifers in their early breeding regimens and eight Holstein heifers in their late breeding regimens were initiated to be bred at 12 and 15 months of age, respectively, and were first calved at 21.5 and 25.1 months of age, respectively, with bodyweights of 563 and 638 kg after calving, respectively. Early first breeding resulted in a lower bodyweight and a lower body condition score, but it did not affect the fertility or milk production during the first lactation of heifers as cows. The calving intervals of cows to the second and third calving were similar in early and late bred heifers. Although the early bred heifers had a significantly lower fat‐corrected milk yield at the second lactation than that of the late bred heifers, early breeding did not impair the productivity indicated by the mean milk yield per day from birth to the end of the third lactation with a shorter production period.  相似文献   
203.
ABSTRACT

Phosphorus (P) is a major nutrient supporting rice productivity. Improving low-P tolerance of rice is expected to reduce dependence on P fertilizer, thereby reducing rice production costs and environmental impacts. This report describes the mapping of quantitative trait loci (QTL) associated with P deficiency tolerance in japonica rice. An F5 population derived from a cross of the low-P tolerant cultivar Akamai (Yamagata) and the sensitive cultivar Koshihikari was evaluated for shoot growth under low-P conditions. Then single nucleotide polymorphism (SNP) profiles of the low-P tolerant and sensitive bulks were compared on a genome-wide scale by QTL-Seq, a rapid QTL mapping method using next-generation sequencing technology. Results show a major QTL associated with low-P tolerance located on the long arm of chromosome 12. It has been named QTL for low-P tolerance 1 or qLPT1. SNPs were detected in 45 genes of qLPT1 region and the 5 genes were harboring synonymous SNPs, although none of them had been reported as involved in low-P tolerance. This result implies that the novel gene responsible for low-P tolerance exists in qLPT1. This study will contribute to the elucidation of mechanisms underlying low-P tolerance of Akamai and will facilitate the breeding of rice with low-P tolerance.  相似文献   
204.
“家族经营协方”在日本农业经济中已经越来越被重视和推广。“家族经营协议”是指在日本农业经济中,为培育法人经营,确保务农事业后继有人,确立 家族务农场的法律地位而形成的一种民法。它的中心目标是把农业作为一种职业,认人们自由选择。同时,“家族经营协议”:以形式确定劳动力在生产经营中的重要作用,也给日本经济带来了新生命力,根据得中国学习借鉴。  相似文献   
205.
This study aimed to determine whether causative pathogens in mastitic milk can be determined by Gram staining after the centrifugation of milk. Gram staining was performed using unconcentrated and concentrated milk cells. Using this method, we found that the background of microscopic image of unconcentrated milk cells was complex and bacteria were difficult to detect. In contrast, the background of the smears in the concentrated milk cells was translucent, and bacterial and somatic cells were clearly visible. The sensitivity and specificity of the Gram staining of concentrated milk cells were 84.4% and 86.0% and 50.0% and 94.5% for the detection of gram-positive and gram-negative bacteria, respectively. The presented method provides a simple and inexpensive means of determining mastitis-causing pathogens.  相似文献   
206.
全放牧婆罗门牛和BMY牛胚胎回收适期的探讨   总被引:1,自引:0,他引:1  
选用婆罗门牛和BMY牛供体超数排卵,以第1次人工授精(AI)当日为0d,分别在AI第6~6.5天、7—7.5天和8—8.5天回收胚胎,统计≤16细胞胚、桑椹胚、囊胚和孵化胚的数量,计算各发育阶段胚胎所占的百分率,分析婆罗门牛和BMY牛的胚胎回收适期。结果表明:婆罗门牛AI第6~6.5天的桑椹胚率比BMY牛高43.54个百分点(P〈0.01),AI第8~8.5天的孵化胚率比BMY牛高35.94个百分点(P〈0.05),胚胎发育速度比BMY牛较快。罗门牛和BMY牛在AI第6~6.5天回收胚胎的囊胚率低,而第8—8.5天的孵化胚率高,胚胎回收以AI第7—7.5天为宜。  相似文献   
207.
Cancer immunotherapy is a novel cancer treatment for canine tumors. Indoleamine 2,3-dioxygenase 1 (IDO1) is overexpressed in some human tumors and inhibits antitumor immunity. In this study, we comprehensively evaluated expression pattern of IDO1 and the nature of IDO1-expressing cells in canine normal and tumor tissues. In normal tissue samples, IDO1 expression was detected only in the lymph nodes, spleen, tonsil tissues, and colon tissues. In contrast, IDO1-positive tumor cells were observed in several tumor tissue types. This is the first study to evaluate IDO1 expression in canine normal and tumor tissues, and the results suggest that IDO1 is a promising target for novel cancer immunotherapy in dogs with tumors.  相似文献   
208.
209.
We conducted a tuberculosis (TB) serosurveillance program of captive elephants in Nepal and compared hematology and biochemistry parameters between seropositive and seronegative elephants. A total of 153 elephants (male=20, female=133) from four national parks were tested for TB using the ElephantTB STAT-PAK® Assay (ChemBio Diagnostic Systems, Inc., Medford, NY, USA). The mean reported age for 138 elephants was 38.5 years (range 2–71 years). Seroprevalence for TB was 21.56% (33/153). The majority of seropositive elephants were female (n=30) and from Chitwan National Park (n=29). The occurrence of TB seropositive cases in other more remote national parks suggests TB may be widespread among the captive elephant population of Nepal. Hematology and biochemistry analyses were performed on 13 and 22 seropositive elephants, respectively and, nine elephants from a seronegative TB herd for comparison. Hematology parameters (hemoglobin, packed cell volume, platelet, white blood cells, and erythrocyte sedimentation rate) were comparable between the two groups. Total protein, globulin, and lactate dehydrogenase were significantly higher in seronegative elephants, and bilirubin was significantly higher in seropositive elephants whereas blood urea nitrogen, creatinine, glutamic oxaloacetic transaminase/aspartate aminotransferase (GOT/AST), glutamic pyruvic transaminase/alanine aminotransferase (GPT/ALT), gamma glutamyl transferase (GT), and albumin were not significantly different. The range of biochemical parameters that were significantly different between seropositive and seronegative elephants had narrow ranges. Thus, the potential of these parameters as a direct biomarker for TB diagnosis is limited based on the findings in this study. We recommend including blood parameters in future TB surveillance studies.  相似文献   
210.
We investigated the influence of paternal effects on progeny survival of the fugu Takifugu rubripes when multiple families were reared in communal tanks. Four males were crossed with four females in a factorial cross to give 16 families, and the half-siblings sharing the same mother were reared together. Male parentage was determined using microsatellite markers at 35 days. Although the maternal and tank effects were large, it was possible to detect paternal effects in relative survival rate and standard length (standardized in each tank), which were found to be significantly correlated. Paternal effects on growth rate suggest the existence of family-based differences in competition for food. Furthermore, genetic differences affecting larval growth appeared to be partly responsible for the disparity in survival rate observed among families.  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