全文获取类型
收费全文 | 1330篇 |
免费 | 53篇 |
专业分类
林业 | 102篇 |
农学 | 28篇 |
基础科学 | 12篇 |
219篇 | |
综合类 | 237篇 |
农作物 | 42篇 |
水产渔业 | 128篇 |
畜牧兽医 | 529篇 |
园艺 | 27篇 |
植物保护 | 59篇 |
出版年
2022年 | 7篇 |
2021年 | 19篇 |
2020年 | 25篇 |
2019年 | 20篇 |
2018年 | 26篇 |
2017年 | 19篇 |
2016年 | 21篇 |
2015年 | 15篇 |
2014年 | 21篇 |
2013年 | 43篇 |
2012年 | 73篇 |
2011年 | 78篇 |
2010年 | 46篇 |
2009年 | 47篇 |
2008年 | 76篇 |
2007年 | 100篇 |
2006年 | 89篇 |
2005年 | 89篇 |
2004年 | 65篇 |
2003年 | 71篇 |
2002年 | 83篇 |
2001年 | 17篇 |
2000年 | 21篇 |
1999年 | 20篇 |
1998年 | 13篇 |
1997年 | 9篇 |
1996年 | 9篇 |
1995年 | 15篇 |
1994年 | 20篇 |
1993年 | 13篇 |
1992年 | 11篇 |
1991年 | 10篇 |
1990年 | 16篇 |
1989年 | 20篇 |
1988年 | 13篇 |
1987年 | 10篇 |
1986年 | 12篇 |
1985年 | 6篇 |
1984年 | 14篇 |
1983年 | 5篇 |
1982年 | 9篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1976年 | 5篇 |
1975年 | 5篇 |
1974年 | 5篇 |
1973年 | 7篇 |
1972年 | 8篇 |
1970年 | 9篇 |
排序方式: 共有1383条查询结果,搜索用时 31 毫秒
31.
32.
Prevalence and intensity of gastrointestinal nematodes in slaughter lambs from central Alberta
下载免费PDF全文
![点击此处可从《The Canadian veterinary journal. La revue veterinaire canadienne》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Colwell DD Goater CP Jacobson KM 《The Canadian veterinary journal. La revue veterinaire canadienne》2002,43(10):775-777
Two trichostronglyes, Teladorsagia ostertagi and Nematodiru helvetianus, accounted for > 99% of nematodes recovered from gastrointestinal tracts of 47 lambs pastured in central Alberta during the summer of 2000. Their prevalence and mean intensity increased from < 10% and < 50 worms/host, in late June, to > 80% and approximately 1000 worms/host, by mid-July, respectively. 相似文献
33.
34.
Masuda K Sakaguchi M Saito S Deboer DJ Yamashita K Hasegawa A Ohno K Tsujimoto H 《Veterinary dermatology》2002,13(1):55-61
Three dogs were examined because of episodes of recurrent pruritic dermatitis in the spring, the season of Japanese cedar (Cryptomeria japonica, CJ) pollination in Japan. The dogs were shown to be sensitive to CJ pollen allergen using intradermal testing and antigen-specific IgE measurement. Fluorometric enzyme-linked immunosorbant assay (ELISA) showed increased concentrations of IgE specific to Cry j 1 and a negative result for Cry j 2 in the three dogs. The concentrations of IgE specific to Cry j 1 during the season of CJ pollination were higher than the concentrations found during the off-season in all the dogs, and the variation in the concentrations correlated with the variation in clinical signs. Peripheral blood mononuclear cells showed apparent proliferative responses to crude CJ pollen antigen and Cry j 1 during CJ pollination season. These findings indicated that Cry j 1 was the major allergen recognized by IgE and lymphocytes and resulted in the development of type I hypersensitivity to CJ pollen allergen in these atopic dogs. 相似文献
35.
ABSTRACT The genome of Tomato leaf curl virus (ToLCV) from Bangalore, India, a whitefly-transmitted geminivirus, was cloned (pIND9) and sequenced. The circular DNA of 2,759 nucleotides (U38239) is organized similarly to that of other begomoviruses with monopartite genomes. Comparison of the nucleotide sequence of pIND9 with other tomato-associated begomoviruses from India (Tomato leaf curl Bangalore virus [ToLCBV, Z48182]) and Tomato leaf curl New Delhi virus-Severe (ToLCNdV-Svr, U15015) showed moderate DNA sequence identities (82 to 87%) between capsid protein (CP) genes but low identities (66 to 67%) for the intergenic regions and the replication-associated protein (Rep) genes (75 to 81% identity). Phylogenetic trees generated with nucleotide sequences of the Rep and CP genes of 26 begomoviruses indicated that this ToLCV is distinct from other begomoviruses and that it may be a recombinant virus derived from at least three different viral lineages. Tomatoes (Lycopersicon esculentum) inoculated with the cloned DNA monomer of ToLCV (pIND9) via particle bombardment developed leaf curling and yellowing symptoms. The virus was transmitted by Bemisia tabaci biotype B from tomatoes infected via particle bombardment to healthy tomatoes and by sap inoculation from infected tomatoes to tomato, Nicotiana benthamiana and N. tabacum. This ToLCV is a distinct member of the genus Begomovirus from India that differs from the previously characterized Tomato leaf curl Sadasivanagar virus isolate Bangalore 1 (L12739), ToLCBV (Z48182), ToLCBV isolate Bangalore 4 (AF165098), and the bipartite ToLCNdV (U15015, U15016). Thus, this ToLCV is named Tomato leaf curl Karnataka virus (ToLCKV). 相似文献
36.
Robinson JE Birch RA Taylor JA Foster DL Padmanabhan V 《Domestic animal endocrinology》2002,23(1-2):43-52
It has long been recognised that steroids can have both organisational and activational effects on the reproductive neuroendocrine axis of many species, including the sheep. Specifically, if the ovine foetus is exposed to testosterone during a relatively short 'window' of in utero development (from approximately day 30-90 of a 147 day pregnancy) the neural mechanisms regulating gonadotrophin releasing hormone (GnRH) secretion become organised in a male-specific manner. In post-natal life the consequences of foetal androgen exposure are sexually differentiated responses of the GnRH neuronal network to activation by factors such as photoperiod and ovarian steroid hormones. Studies in the gonadectomized lamb have demonstrated that elevated concentrations of oestrogen (E) are unable to trigger a preovulatory-like GnRH surge in the male and the androgenized ewe lamb. Further, these animals have markedly reduced sensitivity to the inhibitory actions of progesterone on tonic GnRH release compared with normal ewes. The reasons for these abnormal steroid feedback mechanisms may reside in sexually dimorphic inputs to the GnRH neurone, including those from oestrogen-receptive neurones in the arcuate nucleus that synthetize the neuropeptide, neurokinin B (NKB). The consequences of in utero androgen exposure are reflected in a progressive and dramatic impairment of fertility in the ovary-intact ewe. 相似文献
37.
An exercise in leadership training for veterinary students aiming for careers in biomedical research
A group discussion on the theme of "leadership" has been a central event in the annual Cornell Leadership Program for Veterinary Students since 1990. However, these discussions were often unfocused and did not readily demonstrate the leadership skills of distinguished guests who were invited to participate. Since 1998, a new format for this session has been developed in which students and guests are assigned individual roles in a scenario that is unfolded by a moderator over two to three hours. This role-playing exercise ensures that every student is obliged to participate and has an opportunity to practice such leadership skills as critical thinking, verbal communication, and decision making under pressure and with inadequate information. The distinguished guests, in their assigned roles, are able to interact freely with the student fellows and thus demonstrate their expertise as experienced leaders. This challenging experience has become an enjoyable part of the 10-week Leadership Program and one that shows the importance of leadership skills for those who aspire to careers in the biomedical sciences. 相似文献
38.
Weiss DJ Blauvelt M Sykes J McClenahan D 《Veterinary clinical pathology / American Society for Veterinary Clinical Pathology》2000,29(3):97-104
Abstract: Three flow cytometric techniques were evaluated for determination of differential cell counts on canine clinical bone marrow specimens. Techniques included staining bone marrow specimens with 2'7'-dichlo-rofluorescein (DCF) or 3,3'-dihexyloxacarbocyanine iodide (DiOC6) and evaluation of forward-angle light scatter vs. side-angle light scatter plots. Flow cytometric evaluation of bone marrow cells stained with DCF failed to separate bone marrow cells into distinct cell populations. Staining with DiOC6 resulted in separation of bone marrow cells into populations of mature and immature erythroid cells, mature and immature myeloid cells, and lymphocytes. The scatter plot method resulted in identification of mature and immature erythroid cells, immature myeloid cells, metamyelocytes, and bands and segmenters. Lymphocytes could not be differentiated from mature erythroid cells by the scatter plot method. When the results of the DiOC6 method and the scatter plot method were compared with manual bone marrow differential cell counts, the scatter plot method had more similar mean values and higher correlation coefficients. The scatter plot method has the potential of providing rapid semiquantitative assessment of bone marrow differential cell counts in dogs for specimens that contain low numbers of lymphocytes. 相似文献
39.
Three hundred and forty-two Streptococcus uberis isolates were cultured from milk samples from subclinical and clinical cases of dairy cattle mastitis. The samples were collected from 15 different New Zealand farming regions, including eight specific farms, during field research trials and veterinary diagnostic investigations. Pulsed-field gel electrophoresis was used to determine and compare the degree of genetic dissimilarity between the restriction endonuclease fragment pattern of the 342 New Zealand and a single United States S. uberis isolate. The 343 isolates exhibited 330 different restriction endonuclease fragment patterns. The United States isolate had a pattern unlike any of the New Zealand isolates. Most of the isolates were genetically different strains (pattern deferred by at least 33%), but identical patterns were noted within the same or different quarters of an individual cow, different cows within the same farm, and from different cows from the same or different districts, farming regions or islands. Seven of the eight selected farms had at most only one pair of isolates with banding patterns, which differed by less than 33%. A high degree of dissimilarity was noted in individual herds in which all the samples were collected on the same day or over a 2-year period. The high degree of dissimilar isolates is an indication that S. uberis infections in New Zealand dairy cattle are largely due to the opportunistic nature of the organism in the cows' environment. Prevention and treatment of S. uberis mastitis will therefore need to be directed at a multitude of different strains present throughout the country as well as in individual herds. 相似文献
40.