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   4958篇
  免费   350篇
  国内免费   1篇
林业   396篇
农学   233篇
基础科学   44篇
  1152篇
综合类   166篇
农作物   218篇
水产渔业   616篇
畜牧兽医   1925篇
园艺   109篇
植物保护   450篇
  2023年   48篇
  2022年   68篇
  2021年   155篇
  2020年   152篇
  2019年   168篇
  2018年   284篇
  2017年   225篇
  2016年   224篇
  2015年   174篇
  2014年   221篇
  2013年   317篇
  2012年   334篇
  2011年   351篇
  2010年   205篇
  2009年   223篇
  2008年   288篇
  2007年   262篇
  2006年   227篇
  2005年   212篇
  2004年   192篇
  2003年   152篇
  2002年   154篇
  2001年   99篇
  2000年   93篇
  1999年   69篇
  1998年   33篇
  1997年   21篇
  1996年   18篇
  1995年   27篇
  1994年   9篇
  1993年   13篇
  1992年   22篇
  1991年   21篇
  1990年   25篇
  1989年   20篇
  1988年   10篇
  1987年   17篇
  1986年   11篇
  1985年   8篇
  1984年   8篇
  1983年   14篇
  1982年   9篇
  1981年   8篇
  1980年   14篇
  1978年   8篇
  1977年   11篇
  1976年   8篇
  1973年   7篇
  1969年   12篇
  1967年   8篇
排序方式: 共有5309条查询结果,搜索用时 46 毫秒
71.
The following compounds of milk from Indian-Rhino (Rhinoceros unicorns) were examined: water-, fat-, protein-, potassium-, sodium-, calcium-content. Besides this we analyzed by gas-Liquid chromatography the short-chain and the long-chain fatty-acids.  相似文献   
72.
73.
Two Hungarian virus isolates from sweet pepper (K8) and melon (S4) were identified as cucumber mosaic virus (CMV) on the basis of host plant reactions and serology. The isolates were purified and antisera prepared. Homologous antiserum titers in double-diffusion tests were 256 (K8) and 512 (S4). They were serologically closely related to each other and to other CMV isolates. On the basis of symptoms they belong to different symptomatological groups of CMV; this was supported by serological properties. Sedimentation coefficients were c. 93 S, at 2 mg ml–1. Purified preparations, stained with 2% uranyl acetate, showed spherical particles. In ELISA purified preparations reacted with each other's antisera.Samenvatting Twee hongaarse virusisolaten uit paprika (K8) en meloen (S4) werden geïdentificeerd als komkommermozaïekvirus (CMV) met behulp van toetsplanten en serologie. Beide isolaten werden gezuiverd en er werden antisera tegen bereid. De homologe titers van de antisera in de agar-geldiffusietoets bedroegen 256 (K8) en 512 (S4). K8 en S4 waren serologisch nauw verwant aan elkaar, evenals aan andere CMV-isolaten. Op grond van hun symptomen op toetsplanten behoren ze tot verschillende symptomatologische groepen van CMV. Dit laatste werd gesteund door de serologische eigenschappen. Beide isolaten hebben een sedimentatiecoëfficiënt van ca 93 S, bij een concentratie van 2 mg ml–1. Gezuiverde preparaten, gekleurd met 2% uranylacetaat, bleken bolvormige deeltjes te bevatten. In ELISA reageerden gezuiverde preparaten van K8 en S4 met elkaars antisera.  相似文献   
74.
The carcasses and meat and fat properties of a group of five bulls fed a basal diet with an addition of 0.80 kg of dried pig excrements for 135 days were compared with a group of five control bulls fed the basal diet. The pre-mortal examination of the clinical state of the animals, the post-mortal veterinary inspection of the meat and internal organs, and the comparison of blood transaminase activity did not reveal any signs of health disorders ascribable to the experimental diet. The organoleptic examination and determination of the basic and some other technological characteristics and other properties of the meat and fat did not show any significant differences in quality to justify a decision by which the meat of the experimental bulls would be treated as less valuable or non-edible.  相似文献   
75.
There are very few resistance records on cattle nematodes. South American successive records have been increasing rapidly since the year 2000. In Argentina, increasing dissatisfaction based on the exclusive use of macrocyclic lactones has prompted the use of benzimidazoles in the Pampean region. The studied farm is located in the Argentina humid Pampas and had apparently poor results after anthelmintic treatments. Evaluation of resistance was firstly based on faecal egg reduction after treatment in November 2001 and June 2002 and was complemented with worm counts obtained by necropsy in June 2002. The study reports that the reduction of faecal egg excretion after benzimidazole (reduction 31-79%) or ivermectin treatments (76-97%) in November 2001 was insufficient and these poor results were confirmed in June 2002 (benzimidazoles (65-89%) and ivermectin (47-77%)). Several methods for evaluating faecal egg count reduction were performed and yielded different results. A new method based on the estimated faecal egg counts (corrected from the initial faecal egg counts and animal type using a general linear model) was used and gave higher flexibility in the interpretation of putative resistance to anthelmintics. From necropsy results, it could be concluded that Cooperia oncophora was resistant to avermectins and benzimidazoles and that Cooperia punctata, Ostertagia ostertagi and Haemonchus placei were resistant to benzimidazoles. This case of multispecies and multidrug resistance is probably not unique and could reflect the emergence of resistances in Argentina. This emergence is probably due to the intensive use of anthelmintics, the absence of refugia, and the frequent circulation of infected cattle.  相似文献   
76.
77.
Routine histopathological diagnosis of one representative 3-month-old pig from a group suffering from diarrhoea revealed a massive degree of parasitation by Cryptosporidium parvum, with a concomitant infection by porcine circovirus type 2 (PCV2), that was confirmed by immunohistochemical procedures. The areas of intestine where parasites were more numerous presented abundant PCV2 infected cells in mucosa and submucosa. The concurrence of C. parvum, a rare primary intestinal pathogen in post-weaning and growing pigs, and PCV2 infections suggest an increased susceptibility as a result of an immunosuppression state.  相似文献   
78.
Purpose The goal of our study was the evaluation of a practical method for the recording of flash electroretinograms (ERGs) in sedated, standing horses with the DTL? microfiber electrode. Methods The horses were sedated intravenously with detomidine hydrochloride (0.015 mg/kg). The pupil was dilated and the auriculopalpebral nerve was blocked. The ERGs were recorded with the active electrode on the cornea (DTL?), the reference electrode near the lateral canthus, and the ground electrode over the occipital bone. The light intensities of the white strobe light were 0.03 cd·s/m2 (scotopic) and 3 cd·s/m2 (scotopic and photopic). Photopic and scotopic single flash and flicker responses to Ganzfeld stimulation were recorded. During the 20‐min dark adaptation period the retina was stimulated every 5 min with the 0.03 cd·s/m2 single flash. Results The median b‐wave amplitudes and implicit times were 38 µV and 33 ms (photopic cone‐dominated response), 43 µV and 63 ms (5‐min dark adaptation), 72 µV and 89 ms (10 min), 147 µV and 103 ms (15 min), 188 µV and 109 ms (20 min, 0.03 cd·s/m2, rod response), and 186 µV and 77 ms (20 min, 3 cd·s/m2, maximal combined rod‐cone response). A steady increase in amplitude and implicit time was noted during dark adaptation. No oscillatory potentials could be isolated. Conclusions The use of detomidine hydrochloride sedation and the DTL? microfiber electrode allowed the recording of good quality ERGs. This protocol should permit the detection of functional problems in the retina without the risk involved with general anesthesia.  相似文献   
79.
Zucchini yellow mosaic virus (ZYMV) has emerged as an important pathogen of cucurbits within the last few years in Hungary. The Hungarian isolates show a high biological variability, have specific nucleotide and amino acid sequences in the N-terminal region of coat protein and form a distinct branch in the phylogenetic tree. The virus is spread very efficiently in the field by several aphid species in a non-persistent manner. It can be transmitted by seed in holl-less seeded oil pumpkin (Cucurbita pepo (L) var Styriaca), although at a very low rate. Three isolates from seed transmission assay experiments were chosen and their nucleotide sequences of coat proteins have been compared with the available CP sequences of ZYMV. According to the sequence analysis, the Hungarian isolates belong to the Central European branch in the phylogenetic tree and, together with the ZYMV isolates from Austria and Slovenia, share specific amino acids at positions 16, 17, 27 and 37 which are characteristic only to these isolates. The phylogenetic tree suggests the common origin of distantly distributed isolates which can be attributed to widespread seed transmission.  相似文献   
80.
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