全文获取类型
收费全文 | 507篇 |
免费 | 41篇 |
专业分类
林业 | 15篇 |
农学 | 16篇 |
基础科学 | 4篇 |
64篇 | |
综合类 | 114篇 |
农作物 | 34篇 |
水产渔业 | 24篇 |
畜牧兽医 | 248篇 |
园艺 | 5篇 |
植物保护 | 24篇 |
出版年
2023年 | 5篇 |
2020年 | 8篇 |
2019年 | 7篇 |
2018年 | 10篇 |
2017年 | 17篇 |
2016年 | 12篇 |
2015年 | 7篇 |
2014年 | 8篇 |
2013年 | 17篇 |
2012年 | 10篇 |
2011年 | 20篇 |
2010年 | 10篇 |
2009年 | 18篇 |
2008年 | 23篇 |
2007年 | 19篇 |
2006年 | 22篇 |
2005年 | 9篇 |
2004年 | 19篇 |
2003年 | 13篇 |
2002年 | 14篇 |
2001年 | 13篇 |
2000年 | 9篇 |
1999年 | 9篇 |
1998年 | 5篇 |
1997年 | 11篇 |
1995年 | 6篇 |
1993年 | 6篇 |
1992年 | 14篇 |
1991年 | 8篇 |
1990年 | 7篇 |
1989年 | 13篇 |
1988年 | 5篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 9篇 |
1984年 | 8篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1975年 | 8篇 |
1974年 | 5篇 |
1973年 | 9篇 |
1972年 | 5篇 |
1970年 | 4篇 |
1969年 | 5篇 |
1968年 | 4篇 |
排序方式: 共有548条查询结果,搜索用时 15 毫秒
31.
R. M. Wallace D. Stanek S. Griese D. Krulak N. M. Vora L. Pacha V. Kan M. Said C. Williams T. H. Burgess S. S. Clausen C. Austin J. Gabel M. Lehman L. N. Finelli G. Selvaggi P. Joyce F. Gordin D. Benator A. Bettano S. Cersovsky C. Blackmore S. V. Jones B. D. Buchanan A. I. Fernandez D. Dinelli K. Agnes A. Clark J. Gill M. Irmler D. Blythe K. Mitchell T. J. Whitman M. J. Zapor S. Zorich C. Witkop P. Jenkins P. Mora D. Droller S. Turner L. Dunn P. Williams C. Richards G. Ewing K. Chapman C. Corbitt T. Girimont R. Franka S. Recuenco J. D. Blanton K. A. Feldman 《Zoonoses and public health》2014,61(8):560-570
This article describes and contrasts the public health response to two human rabies cases: one organ recipient diagnosed within days of symptom onset and the transplant donor who was diagnosed 18 months post‐symptom onset. In response to an organ‐transplant‐related rabies case diagnosed in 2013, organ donor and recipient investigations were conducted by multiple public health agencies. Persons with potential exposure to infectious patient materials were assessed for rabies virus exposure. An exposure investigation was conducted to determine the source of the organ donor's infection. Over 100 persons from more than 20 agencies spent over 2700 h conducting contact investigations in healthcare, military and community settings. The 564 persons assessed include 417 healthcare workers [5.8% recommended for post‐exposure prophylaxis (PEP)], 96 community contacts (15.6% recommended for PEP), 30 autopsy personnel (50% recommended for PEP), and 21 other persons (4.8% recommended for PEP). Donor contacts represented 188 assessed with 20.2% recommended for PEP, compared with 5.6% of 306 recipient contacts recommended for PEP. Human rabies cases result in substantial use of public health and medical resources, especially when diagnosis is delayed. Although rare, clinicians should consider rabies in cases of encephalitis of unexplained aetiology, particularly for cases that may result in organ donation. 相似文献
32.
Abstract – Nile tilapia ( Oreochromis niloticus L.) is the dominant of the introduced tilapiines in many East African lakes and has flourished in the presence of introduced Nile perch ( Lates niloticus L.). We explored the hypothesis that O. niloticus exhibits increased omnivory in response to a decline in abundance of haplochromine cichlids. First, we quantified variation in habitat use and diet of O. niloticus in Lake Nabugabo, Uganda. Second, we compared the diet of O. niloticus in lakes with (Nabugabo, Victoria) and without (Mburo, Wamala, Nyamusingiri, Kyasanduka) introduced Nile perch. In Lake Nabugabo, a higher level of phytoplanktivory was observed in small juveniles than in larger fish and in wetland ecotone areas where haplochromines were most abundant. An omnivorous diet dominated by detritus and invertebrates was recorded for O. niloticus in lakes Nabugabo and Victoria, while a predominantly herbivorous diet was characteristic of O. niloticus in lakes without Nile perch. Availability of a broad food base in lakes where inshore insectivores have been reduced may explain the increased omnivory recorded in lakes Nabugabo and Victoria. 相似文献
33.
The epaulette shark (Hemiscyllium ocellatum) and the grey carpet shark (Chiloscyllium punctatum) are commonly found in periodically hypoxic environments. The ecophysiological time available for these animals to safely
exploit these niches during different seasonal temperatures was examined. The time to loss of righting reflex (T
LRR) was examined in response to an open ended anoxic challenge at three seasonal temperatures (23, 25 and 27°C). Ventilation
rates were measured in an open ended anoxic challenge at 23°C and during 1.5 h of anoxia followed by 2 h of re-oxygenation
at 23 and 25°C. The mean T
LRR of epaulette and grey carpet sharks was inversely proportional to temperature. The T
LRR was similar between species at 23°C; however, grey carpet sharks had significantly reduced T
LRR at higher temperatures. During the standardised anoxic challenge, epaulette sharks entered into ventilatory depression significantly
earlier at 25°C. During re-oxygenation, epaulette sharks exposed to anoxia at 23°C had no significant increase in ventilation
rates. However, after anoxic challenge and re-oxygenation at 25°C, epaulette sharks showed a significant increase in ventilation
rates during re-oxygenation. Grey carpet sharks displayed no evidence of ventilatory depression during anoxia. However, during
re-oxygenation, grey carpet sharks had significantly elevated ventilation rates above pre-experimental levels and control
animals. These data demonstrate that the anoxia tolerance times of both species were temperature dependent, with a significant
reduction in the T
LRR occurring at higher temperatures. Epaulette sharks had a significantly greater T
LRR at higher temperatures than grey carpet sharks, which did not enter into a ventilatory depression. 相似文献
34.
35.
P. S. Chapman 《The Journal of small animal practice》2001,42(11):527-529
36.
A total of 35 ejaculates were studied in order to assess the suitability of porcine semen for freezing according to the ejaculate characteristics. The effects of the freezing procedure were identified; a decrease in motility and acrosome quality was found after thawing. The best results on motility were linked to the ejaculates with a volume of less than 100 ml of the sperm‐rich fraction, a concentration lower than 450 × 106 spermatozoa/ml and an agglutination score below 2. However, the best normal apical ridge (NAR) was found when the volume of the sperm‐rich fraction was greater than 150 ml. For this reason, an intermediate volume of the sperm‐rich fraction of the ejaculate for the best motility and the best NAR, a concentration lower than 450 × 106 spermatozoa/ml and a rate of agglutination below 2 should provide the best quality after freezing. This study also attempted to determine whether a positive effect of ejaculate selection on the overall freezing performance might be expected. 相似文献
37.
38.
Plasma concentrations of thyroxine (T4), triiodothyronine (T3), prolactin, growth hormone and corticosterone were measured in immature domestic fowl which were infected with Eimeria maxima, uninfected but given the same amount of food as those infected (pair-fed) or fed ad libitum. Infection with E maxima caused a decrease in plasma T4 concentration whereas pair feeding caused an increase when food intake was minimal. Plasma T3 concentrations were decreased similarly in both infected and pair-fed birds. Infection caused an increase in plasma prolactin concentration, whereas pair-feeding did not. The plasma concentration of growth hormone was not affected by any of the treatments. Plasma corticosterone concentration was markedly increased on days 5 and 6 in pair-fed birds but was not affected by infection with E maxima. 相似文献
39.
G. P. Chapman 《Euphytica》1995,81(2):121-129
Summary Techniques of inflorescence and spikelet culture have been used for three major cereals. In maize, the influence of hormones on sexuality has been demonstrated. For wheat and barley the influence of supplying carbohydrate and nitrogen on grain content has been explored. Although in vitro seed setting is less efficient than in vivo the resulting grains, from optimal treatments, are in almost all respects normal or nearly so. Culture media to achieve this are precisely defined.In reviewing this work a major concern has been to highlight an elegant system of enquiry but at the same time to indicate the remarkably small area of interest to which it has been applied. As a prelude therefore to a consideration of the technical achievements, the range of spikelet form, and more particularly, function are examined. The aim is to encourage the application of inflorescence and spikelet culture to a much wider range of topics than hitherto. 相似文献
40.
The effect of two major dwarfing (Rht-B1b and Rht-D1b) genes varies with environment. Near-isogenic pairs (i.e., tall and
semidwarf) of six spring wheat lines, included in the International Adaptation Trial (IAT), were grown in 81 trials around
the world from 2001 to 2004. Trial yields ranged from 1 to 8 t ha−1 with a mean of ca. 4 t ha−1. Overall, the yield advantage of the lines possessing the dwarfing gene was ca. 10% and was particularly evident in trials
where the mean height of semidwarf isolines exceeded ca. 80 cm. However, the yield advantage was greater in the slightly taller
and older lines (Pavon and Galvez) than in the newer lines Nesser and Kauz and the two durum lines. Sixteen pairs of semidwarf/tall
near-isolines were grown in six managed drought environment trials at CIMMYT in northwestern Mexico. In these trials, height
and yield differences were small and/or negligible in the most droughted environment (2.5 t ha−1) and the slope of yield versus height for each isoline pair became consistently negative with increase in irrigation. In
the IAT, the slope of the yield versus height was much more variable at low heights or yields, presumably due to the fact
that there were many more factors driving the response. Even at the point where the slope became consistently negative (ca.
between 2 and 4 t ha−1), there were some trials where tall isolines equaled or exceeded the yield of semidwarf isolines, particularly in the most
recent developed cultivar, Kauz.
For submission to Euphytica as part of special issue “Challenges to International Wheat Breeding”. From the International
Symposium on Wheat Yield Potential: Challenges to International Wheat Breeding, Days Inn, Ciudad Obregón, Sonora, Mexico,
March 19–24th, 2006. 相似文献