全文获取类型
收费全文 | 5728篇 |
免费 | 259篇 |
国内免费 | 5篇 |
专业分类
林业 | 442篇 |
农学 | 196篇 |
基础科学 | 37篇 |
1134篇 | |
综合类 | 900篇 |
农作物 | 232篇 |
水产渔业 | 356篇 |
畜牧兽医 | 2109篇 |
园艺 | 182篇 |
植物保护 | 404篇 |
出版年
2023年 | 34篇 |
2022年 | 54篇 |
2021年 | 84篇 |
2020年 | 135篇 |
2019年 | 130篇 |
2018年 | 137篇 |
2017年 | 123篇 |
2016年 | 135篇 |
2015年 | 116篇 |
2014年 | 136篇 |
2013年 | 262篇 |
2012年 | 304篇 |
2011年 | 392篇 |
2010年 | 225篇 |
2009年 | 173篇 |
2008年 | 317篇 |
2007年 | 323篇 |
2006年 | 300篇 |
2005年 | 296篇 |
2004年 | 269篇 |
2003年 | 274篇 |
2002年 | 262篇 |
2001年 | 69篇 |
2000年 | 81篇 |
1999年 | 87篇 |
1998年 | 59篇 |
1997年 | 53篇 |
1996年 | 54篇 |
1995年 | 40篇 |
1994年 | 49篇 |
1993年 | 54篇 |
1992年 | 40篇 |
1991年 | 49篇 |
1990年 | 50篇 |
1989年 | 47篇 |
1988年 | 38篇 |
1987年 | 46篇 |
1986年 | 54篇 |
1985年 | 37篇 |
1984年 | 46篇 |
1983年 | 38篇 |
1982年 | 37篇 |
1981年 | 30篇 |
1980年 | 23篇 |
1979年 | 25篇 |
1978年 | 32篇 |
1977年 | 30篇 |
1975年 | 24篇 |
1973年 | 35篇 |
1972年 | 21篇 |
排序方式: 共有5992条查询结果,搜索用时 15 毫秒
51.
Un H Eskiizmirliler S Unal N Freuling CM Johnson N Fooks AR Müller T Vos A Aylan O 《Berliner und Münchener tier?rztliche Wochenschrift》2012,125(5-6):203-208
Following a sustained spill-over event from dogs to foxes, fox rabies spread rapidly in the Aegean region, Turkey. In order to control the outbreak a program of oral vaccination of foxes against rabies was introduced. In the selected vaccination area three annual campaigns between 2008 and 2010 were undertaken during the winter months whereby the vaccine baits were distributed exclusively by plane using a density of 18 baits per km2. Subsequently, fox rabies cases were reported only from locations bordering the non-vaccinated areas. Hence, it was shown that fox rabies control by means of oral rabies vaccination is feasible in Turkey. However, for the progress towards the elimination of fox-mediated rabies in Turkey to be maintained, it is necessary that political and financial support is secured to extend oral vaccination where infected foxes remain. 相似文献
52.
Emaga Thomas Happi Bindelle Jérôme Agneesens Richard Buldgen André Wathelet Bernard Paquot Michel 《Tropical animal health and production》2011,43(1):171-177
Musa sp. peels are widely used by smallholders as complementary feeds for cattle in the tropics. A study of the influence of the
variety and the maturation stage of the fruit on fermentability and metabolisable energy (ME) content of the peels was performed
using banana (Yangambi Km5) and plantain (Big Ebanga) peels at three stages of maturation in an in vitro model of the rumen.
Peel samples were analysed for starch, free sugars and fibre composition. Samples were incubated in the presence of rumen
fluid. Kinetics of gas production were modelled, ME content was calculated using prediction equation and short-chain fatty
acids production and molar ratio were measured after 72 h of fermentation. Final gas production was higher in plantain (269–339 ml
g−1) compared to banana (237–328 ml g−1) and plantain exhibited higher ME contents (8.9–9.7 MJ/kg of dry matter, DM) compared to banana (7.7–8.8 MJ/kg of DM). Butyrate
molar ratio decreased with maturity of the peels. The main influence of the variety and the stage of maturation on all fermentation
parameters as well as ME contents of the peels was correlated to changes in the carbohydrate fraction of the peels, including
starch and fibre. 相似文献
53.
Philippe G.A.C. Vanden Bergh Laurent L.M. Zecchinon Thomas Fett Daniel Desmecht 《Veterinary research》2009,40(4)
Actinobacillus pleuropneumoniae, the causative agent of porcine pleuropneumonia, produces Apx toxins that are recognized as major virulence factors. Recently, we showed that ApxIIIA-cytotoxic activity specifically targets Sus scrofa leukocytes. Since both LtxA from Aggregatibacter actinomycetemcomitans (aggressive periodontitis in humans) and LktA from Mannheimia haemolytica (pneumonia in ruminants) share this characteristic, respectively towards human and ruminant leukocytes, and because both use the CD18 subunit to interact with their respective LFA-1, we hypothesized that ApxIIIA was likely to bind porcine CD18 to exercise its deleterious effects on pig leukocytes. A β
2−integrin-deficient ApxIIIA-resistant human erythroleukemic cell line was transfected either with homologous or heterologous CD11a/CD18 heterodimers using a set of plasmids coding for human (ApxIIIA-resistant), bovine (-resistant) and porcine (-susceptible) CD11a and CD18 subunits. Cell preparations that switched from ApxIIIA-resistance to -susceptibility were then sought to identify the LFA-1 subunit involved. The results showed that the ApxIIIA-resistant recipient cell line was rendered susceptible only if the CD18 partner within the LFA-1 heterodimer was that of the pig. It is concluded that porcine CD18 is necessary to mediate A. pleuropneumoniae ApxIIIA toxin-induced leukolysis. 相似文献
54.
Thomas B. Moorman Jennifer K. Cowan Ellen L. Arthur Joel R. Coats 《Biology and Fertility of Soils》2001,33(6):541-545
Pesticide contamination of soil and groundwater at agricultural chemical distribution sites is a widespread problem in the USA. Alternatives to land-farming or solid waste disposal include biostimulation and phytoremediation. This research investigated the ability of compost, corn stalks, corn fermentation byproduct, peat, manure, and sawdust at rates of 0.5% and 5% (w/w) to stimulate biodegradation of atrazine [6-chloro-N-ethyl-N'-(1-methyethyl)-1,3,5-triazine-2,4-diamine], metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide], and trifluralin [2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine] added as a mixture to soil. Initial concentrations were 175ᆾ mg atrazine kg-1 soil, 182ᆭ mg metolachlor kg-1 soil, and 165ᆫ mg trifluralin kg-1 soil. After amendment addition, 30% of the atrazine, 33% of the metolachlor, and 44% of the trifluralin was degraded over 245 days, which included 63 days' aging prior to amendment additions. Atrazine degradation was enhanced by 0.5% manure, 5% peat, and 5% cornstalk amendments compared to nonamended soils. Metolachlor degradation was enhanced by all amendments at the 5% level, except for compost and peat. Amendments had no effect on trifluralin degradation. The 5% addition of compost, manure, and cornstalks resulted in significant increases in bacterial populations and dehydrogenase activity. A second experiment compared the persistence of atrazine, metolachlor, and trifluralin applied in a mixture to their persistence in soil individually. A combined average of 123 mg atrazine kg-1 remained in soil treated with the three-herbicide mixture compared to 31 mg atrazine kg-1 remaining in soil treated with atrazine only. Atrazine mineralization and atrazine-degrading microorganisms were suppressed by high concentrations of metolachlor, but not by trifluralin. 相似文献
55.
56.
Thomas W. M. Cameron 《Canadian journal of veterinary research》1963,27(7):165-168
Animal diseases are of considerable importance to human welfare both as a cause of illness in man and as a factor in reducing the food potential of the world. Perhaps the most important factor affecting the less developed areas is malnutrition and, while explosive epidemics among animals are of great importance, the most important sources of losses are the chronic, sub-acute or sub-clinical infections, especially those caused by the parasitic worms. 相似文献
57.
The majority of pregnancy loss in ruminants occurs during the first three weeks after conception, particularly during the period of conceptus elongation that occurs prior to pregnancy recognition and implantation. This review integrates established and new information on the biological role of ovarian progesterone(P4), prostaglandins(PGs),interferon tau(IFNT) and cortisol in endometrial function and conceptus elongation. Progesterone is secreted by the ovarian corpus luteum(CL) and is the unequivocal hormone of pregnancy. Prostaglandins(PGs) and cortisol are produced by both the epithelial cells of the endometrium and the trophectoderm of the elongating conceptus. In contrast, IFNT is produced solely by the conceptus trophectoderm and is the maternal recognition of pregnancy signal that inhibits production of luteolytic pulses of PGF2αby the endometrium to maintain the CL and thus production of P4. Available results in sheep support the idea that the individual, interactive, and coordinated actions of P4, PGs, IFNT and cortisol regulate conceptus elongation and implantation by controlling expression of genes in the endometrium and/or trophectoderm. An increased knowledge of conceptus-endometrial interactions during early pregnancy in ruminants is necessary to understand and elucidate the causes of infertility and recurrent early pregnancy loss and provide new strategies to improve fertility and thus reproductive efficiency. 相似文献
58.
59.
K Christiana Grim Thomas McCutchan Jun Li Margery Sullivan Thaddeus K Graczyk Glenn McConkey Michael Cranfield 《Journal of zoo and wildlife medicine》2004,35(2):154-161
Captive juvenile African black-footed penguins (Spheniscus demersus) housed in an outdoor enclosure at the Baltimore Zoo have an average 50% mortality from avian malarial (Plasmodium sp.) infection each year without intense monitoring for disease and chemotherapeutic intervention. During the 1996 malaria transmission season, the safety and efficacy of an anti-circumsporozoite (CSP) DNA vaccine encoding the Plasmodium gallinaceum CSP protein against P. relictum were studied. The goal was to reduce clinical disease and death without initiating sterile immunity after release into an area with stable, endemic avian malaria. The birds were monitored for adverse clinical signs associated with vaccination, the stimulation of an anti-CSP antibody response, and protection afforded by the vaccine. The presence of P. relictum in trapped culicine mosquitoes within the penguin enclosure was monitored to assess parasite pressure. Among the vaccinated penguins, the parasitemia rate dropped from approximately 50% to approximately 17% despite intense parasite pressure, as determined by mosquito infection rate. During the year of the vaccine trial, no mortalities due to malaria occurred and no undesirable vaccination side effects occurred. This is the first trial of an antimalarial vaccine in a captive penguin colony. 相似文献
60.