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   357篇
  免费   57篇
  国内免费   1篇
林业   21篇
农学   17篇
基础科学   4篇
  66篇
综合类   19篇
农作物   19篇
水产渔业   29篇
畜牧兽医   209篇
园艺   9篇
植物保护   22篇
  2022年   3篇
  2021年   5篇
  2020年   13篇
  2019年   15篇
  2018年   15篇
  2017年   11篇
  2016年   7篇
  2015年   13篇
  2014年   11篇
  2013年   17篇
  2012年   20篇
  2011年   26篇
  2010年   14篇
  2009年   7篇
  2008年   28篇
  2007年   20篇
  2006年   24篇
  2005年   23篇
  2004年   10篇
  2003年   9篇
  2002年   17篇
  2001年   6篇
  2000年   11篇
  1999年   8篇
  1998年   3篇
  1997年   3篇
  1996年   5篇
  1995年   2篇
  1994年   1篇
  1993年   4篇
  1992年   7篇
  1991年   11篇
  1990年   7篇
  1989年   8篇
  1988年   7篇
  1987年   4篇
  1986年   4篇
  1985年   3篇
  1984年   1篇
  1983年   1篇
  1982年   2篇
  1981年   1篇
  1980年   1篇
  1977年   1篇
  1976年   2篇
  1975年   3篇
  1973年   1篇
排序方式: 共有415条查询结果,搜索用时 15 毫秒
361.
The aim of this study was to characterise the performance of new molecular methods for the detection and identification of Pseudomonas syringae pv. actinidiae (Psa) and to provide validation data in comparison to the assays mentioned in official diagnostic protocols and being currently used. Eleven molecular tests for the Psa detection were compared in an inter-laboratory comparison where each laboratory had to analyse the same panel of samples consisting of thirteen Psa-spiked kiwifruit wood extracts. Laboratories had to perform also isolation from the wood extracts. Data from this interlaboratory test performance study (TPS) was statistically analysed to assess the performance of each method. In order to provide complete validation data, both for detection and identification, this TPS was supplemented by a further study of identification from pure culture of phylogenetically closely related Pseudomonas spp., Psa, and bacterial strains associated with kiwifruit. The results of both these studies showed that simplex-PCRs gave good results, whereas duplex-PCR and real-time PCR were the most reliable tools for detection and identification of Psa. Nested and multiplex-PCR gave false-positive results. The use of the most reliable detection test is suggested for routine analyses, but when Psa-free status needs to be accurately assessed, it is recommended that at least two detection tests are used. This work provides a wide comparison of the available diagnostic methods, giving new information for a possible revision of the official diagnostic protocols (e.g. European and Mediterranean Plant Protection Organization (EPPO) protocol PM7/120 for the detection of Psa).  相似文献   
362.
363.
An acute, and usually fatal, diarrhea was induced in 11 healthy neonatal dairy calves by oral administration of an enteropathogenic viral inoculum. Fluid and electrolyte therapy was administered to several affected calves. Plasma corticoid values were determined by radio-immunoassay and competitive protein-binding assay, after purification of the plasma by paper chromatography. Statistical comparisons between control and diarrheic groups of calves were made on 5 corresponding experimental days. Plasma aldosterone values of 2 groups of diarrheic calves which died with and without treatment were greater (P less than 0.01) just before death than those of controls and diarrheic calves which recovered. Plasma hydrocortisone and progesterone values in the calves not treated were higher (P less than 0.05) on the day preceding death than in the controls. Plasma corticosterone concentration was increased (P less than 0.05) throughout the disease in both groups of calves that recoverd. These results indicate that the adrenal cortex of the neonatal calf can respond to the severe stressor influences and fluid-electrolyte losses of diarrhea.  相似文献   
364.
  • ? As the French national forest inventory does not currently monitor the lying compartment of the forest deadwood, the figures obtained on this topic are therefore partial. This study provides cost estimates and guidelines for assessing stumps, and standing and lying deadwood.
  • ? Comparisons were made between a fixed-area sampling method and a line-intersect one. LIS was judged more time-efficient, especially in dense understorey. Computer simulations were performed in order to estimate the gain in precision with increasing transect lengths. The results showed a continuous improvement in precision associated with increases in transect length. The longest transect tested (50 m) still had a large coefficient of variation, suggesting that improvement in precision at the plot level could still be gained with longer transects.
  • ? Therefore, from a practical standpoint in terms of fieldwork, we suggest that on a national scale lying deadwood should be measured by line-intersect sampling, whereas stumps, standing dead trees and snags can be monitored using standard fixed-area plots. To meet needs at the national level, we consider that local imprecision could be compensated for by the large number of plots measured each year.
  •   相似文献   
    365.
    366.
    One hundred twenty-six cutaneous mast cell tumors obtained by excisional biopsy from 106 dogs were evaluated using immunohistochemical staining for the presence of p53 protein. A standard avidin-biotin immunohistochemical protocol was used incorporating a polyclonal antibody of rabbit origin (CM-1) as the primary antibody. Histopathologic grading of tumors was performed on hemotoxylin and eosin-stained samples. There was a significant difference in the percentage of cells staining positive for p53 for the histopathologic grades (P = 0.0005). Grade III tumors had a significantly greater p53 content than did grade I or II tumors (P < 0.05). Clinical data obtained retrospectively was available for 54 dogs. Tumor recurred in 19 of 54 (35.2%) dogs. Twenty-nine dogs died by the end of the study; 9 of 29 (31.0%) died of mast cell tumor disease. Histopathologic grade showed a significant negative association with survival time. Both clinical stage and histopathologic grade showed a significant negative association with time to recurrence. The percentage of cells staining positive for p53 did not significantly improve the forward analysis. Immunohistochemical detection of p53 did not appear useful in characterizing the clinical association between cutaneous mast cell tumor cellular features and survival time or time to tumor recurrence in dogs.  相似文献   
    367.
    In a rainbow boa (Epicrates chenchria maurus) an affection of the spectacle of the eyes caused by the fungus Fusarium oxysporum is described for the first time. Enucleation was performed under premedication of Hypnodil and inhalation anesthesia with tracheal intubation, using Halothane. Résumé. On décrit, pour la première fois, chez le boa Epicrates chenchria maurus une affection des paupières transparentes causée par le fongus Fusarium oxysparum. L'énucléation a été faite sous prémédication d'Hypnodil et d'inhalation anesthésie avec intubation trachéale, utilisant Halothane. Zusammenfassung. In einer Boa, Epicrates chenchria maurus, wurde eine Erkrankung von der durchsichtigen Kapsel über dem Auge, verursacht durch den Fungus Fusarium oxysporum zum ersten Ma1 beschrieben. Enukleation wurde vorgenommen, unter Basisnarkose van Hypnodil und Einatmungsanästhesie mit trachealer Intubation, indem man Halothane gebrauchte.  相似文献   
    368.
    In calves inoculated with live swine influenza virus (SIV) A/sw/IL/75 (H1N1) intranasally, SIV was isolated for 7 days, and respiratory tract disease was observed. Antibody was detected in serum of inoculated calves from postinoculation day 9, and virus-neutralization antibody was demonstrated on postinoculation days 14 and 21. The primary response was low, but readily differentiated from the secondary response after calves were challenge exposed with homologous SIV. Pneumonic lesions were observed at necropsy, and histopathologic changes in airways and lungs were consistently found. Fluorescent staining revealed viral activity in epithelial cells of airways. The virus was transferred to healthy calves housed with inoculated calves.  相似文献   
    369.
    The aim of this work was to analyse the genetic origin of the Mexican Creole donkey, as well as its genetic diversity, by comparison with Spanish and African donkey populations by means of the D-loop region of mitochondrial DNA. To this end, the genomic DNA of 68 Mexican Creole donkeys from eight geographical regions in six States of the Republic of México and from a Sicilian donkey was obtained. By the polymerase chain-reaction technique (PCR) a fragment of 541 bp was amplified, corresponding to the most informative region of the mitochondrial DNA, the D-loop. The fragments were subsequently sequenced. The analysed sequences revealed 10 new Mexican haplotypes that were different from those of the Spanish and African breeds with which they were compared, showing high levels of genetic diversity. Analysis of the phylogenetic relationships in the different Creole varieties showed a tendency of origin towards Spanish breeds, mainly the Andaluza, Zamorano-Leonesa and Majorera from the Canary Islands; these in turn showed an African origin, seven Mexican haplotypes and three haplotypes similar to those analysed by Aranguren and colleagues (2004) of Spanish and African breeds being obtained. This work allows us to reach the preliminary conclusion that the origin of Mexican Creole donkey populations in the different states of the Republic of México is clearly of Iberian origin, the Spanish donkey breed Andaluza being the main one contributing to the populations of the Mexican Creole donkeys, followed by the Spanish breeds Zamorano-Leonesa and Majorera from the Canary Islands, and that the populations possess high levels of genetic diversity.  相似文献   
    370.
    Canine B‐cell lymphoma is a clinically heterogenous disease; however, it is generally treated as a single disease entity. The purpose of this clinical trial was to prospectively evaluate naïve canine B‐cell lymphoma patients using histopathology, flow cytometry (FC) and a standardized chemotherapy protocol to better define subsets of this disease that may respond differently to treatment. Sixty‐four dogs with naïve multicentric B‐cell lymphoma were treated with a standardized 19‐week CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone) chemotherapy protocol. Most of the dogs (84.3%) were diagnosed with diffuse large B‐cell lymphoma (DLBCL), followed by nodal marginal zone (7.8%), small B‐cell (4.7%), Burkitt‐like (1.6%) and follicular lymphoma (1.6%). FC confirmed the diagnosis of B‐cell lymphoma in all cases. There were no clear phenotyping differences between the subtypes of B‐cell lymphoma detectable by our FC panel. The histologic subtypes in this study exhibited a range of forward scatter values on flow cytometry, but all of the DLBCL cases were higher than a value of 469, while the only cases with a lower forward scatter value were follicular lymphoma and diffuse small B‐cell lymphoma. Dogs with DLBCL had a significantly better objective response rate to the CHOP protocol (96.3%) than the non‐DLBCL subtypes (70%, P = .024). The median progression‐free survival time for patients with DLBCL (233 days) was significantly longer than that of all other histopathologic subgroups combined (163 days, P = .0005).  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