全文获取类型
收费全文 | 1052篇 |
免费 | 53篇 |
专业分类
林业 | 36篇 |
农学 | 35篇 |
基础科学 | 21篇 |
148篇 | |
综合类 | 88篇 |
农作物 | 37篇 |
水产渔业 | 72篇 |
畜牧兽医 | 595篇 |
园艺 | 11篇 |
植物保护 | 62篇 |
出版年
2021年 | 9篇 |
2020年 | 12篇 |
2019年 | 25篇 |
2018年 | 13篇 |
2017年 | 13篇 |
2016年 | 20篇 |
2015年 | 18篇 |
2014年 | 19篇 |
2013年 | 54篇 |
2012年 | 28篇 |
2011年 | 47篇 |
2010年 | 26篇 |
2009年 | 32篇 |
2008年 | 55篇 |
2007年 | 58篇 |
2006年 | 38篇 |
2005年 | 44篇 |
2004年 | 38篇 |
2003年 | 32篇 |
2002年 | 39篇 |
2001年 | 30篇 |
2000年 | 30篇 |
1999年 | 33篇 |
1998年 | 13篇 |
1997年 | 15篇 |
1996年 | 9篇 |
1995年 | 13篇 |
1994年 | 10篇 |
1993年 | 12篇 |
1992年 | 21篇 |
1991年 | 19篇 |
1990年 | 11篇 |
1989年 | 16篇 |
1988年 | 16篇 |
1987年 | 12篇 |
1986年 | 11篇 |
1985年 | 19篇 |
1984年 | 10篇 |
1983年 | 11篇 |
1982年 | 10篇 |
1981年 | 7篇 |
1979年 | 12篇 |
1978年 | 10篇 |
1977年 | 7篇 |
1975年 | 14篇 |
1974年 | 12篇 |
1973年 | 10篇 |
1971年 | 11篇 |
1969年 | 11篇 |
1967年 | 8篇 |
排序方式: 共有1105条查询结果,搜索用时 93 毫秒
991.
Mapping of QTL for resistance to powdery mildew and resistance gene analogues in perennial ryegrass 总被引:1,自引:0,他引:1
The objective of this study was to map resistance gene analogues (RGA) and quantitative trait loci (QTL) for powdery mildew resistance in perennial ryegrass ( Lolium perenne L.). The mapping population consisted of 184 F2 genotypes produced from a cross between one genotype of a synthetic perennial ryegrass variety Veyo and one genotype from the perennial ryegrass ecotype Falster. The greenhouse infection was measured as number of sporulating colonies on a 10-cm leaf area with the maximum possible number of colonies to be counted set to 50. The range of infection scores in the population was 0–50 and the heritability was 71.7%. In total, two QTL for powdery mildew resistance were identified, and mapped to linkage groups (LG) LG3 and LG7. Individually, these QTL explained between 7.5% and 22.1% of the total phenotypic variation. Six RGA and three laccases were mapped to LG2, LG3, LG4, LG5 and LG7, however, no close linkage between RGA and QTL was observed. 相似文献
992.
Lise Nistrup Jørgensen Egon Noe Ghita C. Nielsen Jens Erik Jensen Jens Erik Ørum Hans O. Pinnschmidt 《European journal of plant pathology / European Foundation for Plant Pathology》2008,121(3):303-312
Plant pathologists have traditionally worked in the area of clarifying and understanding the disease cycles of specific diseases,
factors influencing epidemiology, yield loss potential and host-pathogen interactions in order to be able to minimise the
disease risk, build warning systems or recommend specific control thresholds in relation to the application of fungicides.
The decision support system Crop Protection Online (CPO) is an example of a threshold-based system that determines economically
viable fungicide strategies. The system is based on using appropriate doses aimed at minimising the overall pesticide input.
CPO is used widely by advisors and many of the thresholds are generally accepted and disseminated through newsletters. The
national figures for the use of fungicides in cereals have shown a major reduction during the last 20 years and their use
today is much in line with the level that can be achieved from using CPO as indicated from validation trials. The number of
end-users among farmers has been stable at around 3% during the last 10 years (800–1,000 farmers). Major hurdles in increasing
the number of users are believed to be: (1) the requirements for carrying out assessments in the field, (2) farm sizes getting
larger, leaving less time for decision making for individual fields, (3) lack of economic incentives to change from standard
treatments, (4) the failure of decision support systems to interact with other computer-based programmes on the farm, (5)
the lack of compatibility of decision support systems with farmers’ ways of making decisions on crop protection in general,
(6) the need for direct interactions with advisors. A sociological investigation into the farmers’ way of making decisions
in the area of crop protection has shown that arable farmers can be divided into three major groups: (a) systems-orientated
farmers, (b) experienced-based farmers and (c) advisory-orientated farmers. The information required by these three groups
is different and has to be looked at individually from the end-user’s perspective rather than from the scientist’s perspective.
New ways of entering the decision support system where specific field inspections are omitted and where regional disease data
are relied on, have been investigated and tested in field trials. The results show possibilities for further developments
in that direction, which might be one way of gaining more end-users. 相似文献
993.
The competitive ability of pea-barley intercrops against weeds and the interactions with crop productivity and soil N availability 总被引:1,自引:0,他引:1
G. Corre-Hellou A. DibetH. Hauggaard-Nielsen Y. CrozatM. Gooding P. AmbusC. Dahlmann P. von FragsteinA. Pristeri M. MontiE.S. Jensen 《Field Crops Research》2011,122(3):264-272
Grain legumes, such as peas (Pisum sativum L.), are known to be weak competitors against weeds when grown as the sole crop. In this study, the weed-suppression effect of pea-barley (Hordeum vulgare L.) intercropping compared to the respective sole crops was examined in organic field experiments across Western Europe (i.e., Denmark, the United Kingdom, France, Germany and Italy). Spring pea (P) and barley (B) were sown either as the sole crop, at the recommended plant density (P100 and B100, respectively), or in replacement (P50B50) or additive (P100B50) intercropping designs for three seasons (2003-2005). The weed biomass was three times higher under the pea sole crops than under both the intercrops and barley sole crops at maturity. The inclusion of joint experiments in several countries and various growing conditions showed that intercrops maintain a highly asymmetric competition over weeds, regardless of the particular weed infestation (species and productivity), the crop biomass or the soil nitrogen availability. The intercropping weed suppression was highly resilient, whereas the weed suppression in pea sole crops was lower and more variable. The pea-barley intercrops exhibited high levels of weed suppression, even with a low percentage of barley in the total biomass. Despite a reduced leaf area in the case of a low soil N availability, the barley sole crops and intercrops displayed high weed suppression, probably because of their strong competitive capability to absorb soil N. Higher soil N availabilities entailed increased leaf areas and competitive ability for light, which contributed to the overall competitive ability against weeds for all of the treatments. The contribution of the weeds in the total dry matter and soil N acquisition was higher in the pea sole crop than in the other treatments, in spite of the higher leaf areas in the pea crops. 相似文献
994.
Massimiliano CarciofiShahnoor S. Shaik Susanne L. Jensen Andreas BlennowJan T. Svensson Éva VinczeKim H. Hebelstrup 《Journal of Cereal Science》2011,54(3):339-346
Plant starch is naturally phosphorylated at a fraction of the C6 and the C3 hydroxyl groups during its biosynthesis in plastids. Starch phosphate esters are important in starch metabolism and they also generate specific industrial functionality. Cereal grains starch contains little starch bound phosphate compared with potato tuber starch and in order to investigate the effect of increased endosperm starch phosphate, the potato starch phosphorylating enzyme glucan water dikinase (StGWD) was overexpressed specifically in the developing barley endosperm. StGWD overexpressors showed wild-type phenotype. Transgenic cereal grains synthesized starch with higher starch bound phosphate content (7.5 (±0.67) nmol/mg) compared to control lines (0.8 (±0.05) nmol/mg) with starch granules showing altered morphology and lower melting enthalpy. Our data indicate specific action of GWD during starch biosynthesis and demonstrates the possibility for in planta production of highly phosphorylated cereal starch. 相似文献
995.
996.
Liver Protective Effects of Morinda citrifolia (Noni) 总被引:1,自引:0,他引:1
Wang MY Nowicki D Anderson G Jensen J West B 《Plant foods for human nutrition (Dordrecht, Netherlands)》2008,63(2):59-63
This study evaluated the protective effects of Noni fruit juice on acute liver injury induced by carbon tetrachloride (CCl(4)) in female Sprague-Dawley (SD) rats. Liver damage (micro-centrilobular necrosis) was observed in animals pretreated with 20% placebo (drinking water) + CCl(4). However, pretreatment with 20% Noni juice in drinking water + CCl(4) resulted in markedly decreased hepatotoxic lesions. Furthermore, serum alanine aminotransferase and aspartate aminotransferase levels were significantly lower in the Noni group than the placebo group. In a correlative time-dependent study, one dose of CCl(4) (0.25 mL/kg in corn oil, p.o.) in female SD rats, pretreated with 10% placebo for 12 days, caused sequential progressive hepatotoxic lesions over a 24 h period, while a protective effect from 10% Noni juice pretreatment was observed. These results suggest that Noni juice is effective in protecting the liver from extrinsic toxin exposure. 相似文献
997.
The effectiveness of anthelmintics was evaluated in four herds of captive ruminants, wapiti (Cervus elaphus), Armenian red sheep (Ovis orientalis), giraffe (Giraffa camelopardalis), and pronghorn (Antilocapra americana), by the use of fecal egg reduction tests (FERTs) and a commercial larval development assay (LDA) designed to evaluate susceptibility or resistance of nematodes to anthelmintics. Haemonchus sp. was the predominant nematode in the red sheep, giraffe, and pronghorn herds, whereas Ostertagia sp. and Trichostrongylus sp. were predominant in the wapiti. The LDA data indicated susceptibility by the worms to benzimidazoles except in the red sheep flock, which showed a high level of resistance. High levels of resistance to levamisole were seen in the worm populations from the wapiti and red sheep, moderate resistance in the pronghorn herd, and susceptibility in the giraffe herd. Worms were susceptible in all four herds to a combination of benzimidazole/levamisole. There was suspected avermectin resistance by Trichostrongylus sp. in the wapiti herd and by Haemonchus sp. in the giraffe. The FERTs agreed with the LDA in showing the Haemonchus in the giraffe was susceptible to fenbendazole and had suspected resistance to ivermectin, whereas Haemonchus in the red sheep and pronghorn were susceptible to ivermectin. There was correlation between the tests evaluating anthelmintics. The LDA is useful as a screening test in the selection of an anthelmintic for use in grazing ruminants, but the effectiveness of a drug in a host species may depend as much on the dose used, and the method of administration, as it does on the parasite's sensitivity to the anthelmintic. 相似文献
998.
999.
Richard Skøtt Rasmussen Flemming Hausgaard Larsen Stig Jensen 《Aquaculture International》2007,15(2):97-107
Rainbow trout were studied at different rearing densities, fish sizes and feeding frequencies so that we could evaluate the
effect of these parameters on fin condition, growth and feed utilisation. In one study, two sizes of rainbow trout (18–70 g
or 48–125 g), fed to near satiation at 17.7°C, were examined at two rearing densities (11–41 kg m−3 or 21–92 kg m−3). This study showed that the anal fin was healthier (P < 0.05) at low densities. In the second study rainbow trout were again fed to near satiation and grown from 50 g to 125 g
in 16.4°C water, and they were fed either once daily or three times daily at two densities (18–45 kg m−3 or 54–124 kg m−3). Rainbow trout growth and feed utilisation were slightly but significantly (P < 0.05) reduced at high densities, while dorsal fin condition, surprisingly, was better (P < 0.0001) at the high densities. Possible explanations to these findings are discussed. Condition of the left pectoral fin
was improved at once daily feeding (P < 0.05) compared with three feedings per day, at which fights for feed possibly are more frequent. 相似文献
1000.
APETx2 is a peptide isolated from the sea anemone Anthopleura elegantissima. It is the most potent and selective inhibitor of acid-sensing ion channel 3 (ASIC3) and it is currently in preclinical studies as a novel analgesic for the treatment of chronic inflammatory pain. As a peptide it faces many challenges in the drug development process, including the potential lack of stability often associated with therapeutic peptides. In this study we determined the susceptibility of wild-type APETx2 to trypsin and pepsin and tested the applicability of backbone cyclisation as a strategy to improve its resistance to enzymatic degradation. Cyclisation with either a six-, seven- or eight-residue linker vastly improved the protease resistance of APETx2 but substantially decreased its potency against ASIC3. This suggests that either the N- or C-terminus of APETx2 is involved in its interaction with the channel, which we confirmed by making N- and C-terminal truncations. Truncation of either terminus, but especially the N-terminus, has detrimental effects on the ability of APETx2 to inhibit ASIC3. The current work indicates that cyclisation is unlikely to be a suitable strategy for stabilising APETx2, unless linkers can be engineered that do not interfere with binding to ASIC3. 相似文献