全文获取类型
收费全文 | 110671篇 |
免费 | 6172篇 |
国内免费 | 68篇 |
专业分类
林业 | 4718篇 |
农学 | 3584篇 |
基础科学 | 577篇 |
13659篇 | |
综合类 | 17383篇 |
农作物 | 3793篇 |
水产渔业 | 5955篇 |
畜牧兽医 | 58775篇 |
园艺 | 1343篇 |
植物保护 | 7124篇 |
出版年
2018年 | 1885篇 |
2017年 | 1988篇 |
2016年 | 1832篇 |
2015年 | 1571篇 |
2014年 | 1818篇 |
2013年 | 4552篇 |
2012年 | 3425篇 |
2011年 | 3917篇 |
2010年 | 2522篇 |
2009年 | 2442篇 |
2008年 | 3705篇 |
2007年 | 3564篇 |
2006年 | 3331篇 |
2005年 | 3037篇 |
2004年 | 2956篇 |
2003年 | 2970篇 |
2002年 | 2707篇 |
2001年 | 3619篇 |
2000年 | 3648篇 |
1999年 | 2906篇 |
1998年 | 1158篇 |
1997年 | 1060篇 |
1996年 | 985篇 |
1995年 | 1174篇 |
1994年 | 1064篇 |
1993年 | 981篇 |
1992年 | 2318篇 |
1991年 | 2485篇 |
1990年 | 2343篇 |
1989年 | 2280篇 |
1988年 | 2154篇 |
1987年 | 2164篇 |
1986年 | 2147篇 |
1985年 | 2073篇 |
1984年 | 1722篇 |
1983年 | 1532篇 |
1982年 | 978篇 |
1979年 | 1521篇 |
1978年 | 1210篇 |
1977年 | 1138篇 |
1976年 | 1087篇 |
1975年 | 1137篇 |
1974年 | 1405篇 |
1973年 | 1318篇 |
1972年 | 1345篇 |
1971年 | 1195篇 |
1970年 | 1153篇 |
1969年 | 1149篇 |
1968年 | 971篇 |
1967年 | 1002篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
We report on an outbreak of enzootic abortion in a herd of goats with high losses caused by mixed infection with Coxiella burnetii and Chlamydia psittaci. Both agents could be detected by microscopic investigation of smears from afterbirths by Giménez staining and by a capture enzyme-linked immunofluorescence assay (Capture ELIFA). Additionally, Coxiella burnetii was isolated from the same tissues in BGM cell cultures. Serological investigations with CF, indirect ELIFA, and IF tests revealed high antibody titers against both agents in most animals. Coxiella antigen was still detected 91 days later in milk samples of two infected goats by Capture ELIFA. 相似文献
92.
There is only limited information on sheep interferon available. Recent publications have reported on: 1. an interferon (IFN) alpha subtype, which is secreted by the fetal trophectoderm into the lumen of the uterus between the 10th and 21st day of gestation. It was therefore named ovine trophoblast protein (oTP-1), and is responsible for signalling pregnancy to the ewe via high affinity receptors in the endometrium. It is thought that oTP-1 acts by directly influencing prostaglandin metabolism. 2. the role of lentivirus-induced interferon (LV-IFN) in the pathogenesis of Maedi/Visna. The results indicate that LV-IFN limits viral replication and therefore contributes to virus persistence and is also responsible for a chronic inflammatory process. 3. the mitogen- or antigen-dependent induction of ovine interferon gamma (IFN gamma) and its characterization. 相似文献
93.
94.
95.
Serum antibody (virus neutralisation, complement fixation, IgM and IgG) responses to equine herpesvirus-1 (EHV-1) infection were measured in six foals which were initially free from EHV-1 and EHV-4 infection and maternally-derived antibodies. Following primary infection, high titres of virus neutralisation and complement fixation antibodies were detectable against EHV-1, however, corresponding antibody levels against EHV-4 were low or inapparent, although the two viruses share a number of cross-reactive epitopes. In addition, following the primary infection with EHV-1, IgM levels increased before those of IgG, virus neutralisation and complement fixation antibodies, peaked sooner and thereafter declined. Stimulation of IgM levels was observed on secondary infection with EHV-1 given 61 days later. In contrast, IgG, virus neutralisation and complement fixation antibodies following primary infection were more sustained and no increase in their levels was observed on secondary infection. No consistent changes in IgM or IgG levels were seen after administration of dexamethasone to reactivate latent virus. 相似文献
96.
97.
Long‐term experiments are a classical case of repeated measurements. Traits are measured on the same experimental unit over many years so that correlations arise between the observations made on the same plot in consecutive years. This paper describes the analysis of a three‐crop‐rotation long‐term experiment. We analysed the yields of the crops and the organic carbon content in the topsoil over 30 consecutive years. Several variance–covariance approaches are discussed and the trait‐specific best fit is interpreted. Mixed models are used to describe the structure of the experiment. Both yields and soil organic carbon show a more or less pronounced variance heterogeneity. Especially for yields, the heterogeneity of cycles and years is dominant. The consideration of correlations results in a better model fit in all cases. 相似文献
98.
Application of new procedures in the sphere of the control of sexual functions requires an extension of present knowledge of postparturient endocrinium or endogenic factors comprised in postparturient physiology of sexual activity. According to recent data, oxytocin, besides its uterotonic and luteolytic activity, acts as an ovarian factor in the local intrafollicular regulation of stereidogenesis and as a modulator of uterine secretion of prostaglandines. Based on present knowledge of oxytocin effects, this study was aimed at investigation of the influence of repeated carbetocin (Depotocin inj. Spofa) administration on the dynamics of changes in thyroxine (T4), triiodothyronine (T3), 17 beta-estradiol (E2), progesterone (P4) concentrations and their mutual correlations from the 36th hour till the 51st day after parturition. Simultaneous study of a possible delayed influence of applied carbetocin on conception of ewes after oestrus evocation on day 51 after lambing was carried out. Nineteen ewes of the Slovak Merino breed, lambed in the first decade of February, were assigned to the experimental (n = 9) and to the control group (n = 10). Experimental ewes were subjected to repeated postparturient carbetocin treatment at the dose 0.07 mg per animal. The first dose was applied i. m. in 24 hours, and the second in 72 hours after parturition. On day 51 oestrus was induced in nine ewes of each group by combined treatment with chlorsuperlutin (Agelin, vaginal pessaries, Spofa) and PMSG (500 I.U./animal). On the day of PMSG application ewes were housed together with rams for the period of the next six days. Samples of blood were taken 24 hours before parturition (-1st day), up to 36 h after parturition and on days 4, 7, 14, 17, 21, 25, 34, 42 and 51 after parturition. Concentrations of T4, T3, E2 and P4 were determined by commercial kits RIA-test-T4; RIA-test-T3; RIA-test-ESTRA and RIA-test-PROG (URVJT Kosice). Animal of the control group showed variations of T4 concentrations (Tab. I, Fig. 1) at the level of original values (59.4 +/- 9.69 nmol.l-1) up to the 21st day with the exception of temporary drop on day 4 and rise on day 7, insignificant compared to the -1st day. T4 concentrations of the control group displayed an intermittent increasing trend with the statistically insignificant peak after 36 h and on day 17, compared to the -1st day. After the 21st day controls revealed a sustained moderate increase while the experimental ewes displayed a decline of its concentrations until the 51st day.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献
99.
J B Herrick 《Veterinary Clinics of North America: Food Animal Practice》1989,5(3):457-469
Marketing to veterinarians is the process of synchronizing the business aspects of his or her goods and services so that they are understood and desired by animal owners. The basic components of a successful marketing program are in four categories: the individual, the situation, the needs, and the implementation. Each category is important and all are interrelated; however, the implementation of a program should not begin until a self-analysis has been done and the situation and its needs are thoroughly researched. Programs that have been used by successful practitioners can be copied. No program can be effective unless the economic status of the client's enterprise is known and understood. 相似文献
100.
A. T. Szabó 《Genetic Resources and Crop Evolution》2005,52(3):347