全文获取类型
收费全文 | 314篇 |
免费 | 58篇 |
专业分类
林业 | 18篇 |
农学 | 13篇 |
54篇 | |
综合类 | 12篇 |
农作物 | 9篇 |
水产渔业 | 82篇 |
畜牧兽医 | 166篇 |
园艺 | 7篇 |
植物保护 | 11篇 |
出版年
2023年 | 5篇 |
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 4篇 |
2018年 | 25篇 |
2017年 | 18篇 |
2016年 | 18篇 |
2015年 | 13篇 |
2014年 | 16篇 |
2013年 | 48篇 |
2012年 | 19篇 |
2011年 | 23篇 |
2010年 | 17篇 |
2009年 | 10篇 |
2008年 | 12篇 |
2007年 | 12篇 |
2006年 | 7篇 |
2005年 | 5篇 |
2004年 | 5篇 |
2003年 | 4篇 |
2002年 | 6篇 |
2001年 | 10篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 11篇 |
1997年 | 9篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1994年 | 9篇 |
1993年 | 4篇 |
1992年 | 7篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1979年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1970年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有372条查询结果,搜索用时 15 毫秒
81.
M Abad JC Garcia DJ Sprecher G Cassar RM Friendship MM Buhr RN Kirkwood 《Reproduction in domestic animals》2007,42(4):418-422
In swine, the use of frozen-thawed (FT) sperm for artificial insemination (AI) is limited because of poor sow fertility, possibly associated with a post-thaw capacitation-like status resulting in fewer fully viable sperm. Sow fertility to AI with FT sperm may improve with deeper deposition of sperm within the female tract, insemination very close to ovulation, or reversal of cryocapacitation by seminal plasma (SP). We performed two experiments to examine these suggestions. In experiment 1, 122 multiparous Yorkshire sows received 600 IU equine chorionic gonadotrophin at weaning and 5 mg pLH 80 h later to control time of ovulation. The predicted time of ovulation (PTO) was 38 h after pLH injection. Thereafter, sows were assigned on the basis of parity to a single AI of FT sperm at 2 h before PTO, or at 12 h before PTO, or FT sperm supplemented with 10% SP at 12 h before PTO. Control sows received fresh semen at 12 h before PTO. All semen doses were adjusted to 3 x 10(9) live cells and deposited into the cervix. Experiment 2 employed 99 multiparous crossbred sows and repeated the treatments of experiment 1 except that all FT inseminations were intrauterine. In both experiments, farrowing rates were lower (p < 0.01) following FT inseminations with no effect of time of insemination or of supplemental SP. In experiment 1, litter size was smaller following FT insemination (p < 0.05), but no effect on litter size was evident in experiment 2. Supplemental SP had no effect on litter size in either experiment. The lack of effect of either SP or timing of FT insemination on sow fertility suggests that the non-lethal sperm cryoinjury affecting fertility involves more than just cryocapacitation. 相似文献
82.
Bjærke O, Østbye K, Lampe HM, Vøllestad LA. Covariation in shape and foraging behaviour in lateral plate morphs in the three‐spined stickleback. Ecology of Freshwater Fish 2010: 19: 249–256. © 2010 John Wiley & Sons A/S Abstract – In three‐spined stickleback (Gasterosteus aculeatus) colonisation of freshwater has led to rapid evolution in various morphological and behavioural traits. Examples are reduction in lateral plate number and increased benthic foraging. These changes are believed to result from natural selection, but the evolutionary mechanisms driving behavioural changes and how such changes are associated with phenotypes, are poorly understood. Here, we study three different lateral plate morphs from a brackish water lake and one morph from a river upstream. We investigate if the lateral plate morphs differ in overall body shape and then experimentally test how foraging behaviour differ among morphs and with body shape. Foraging behaviour is measured as the consumption efficiency of benthic and pelagic prey types. The results show that lateral plate morphs differ in overall body shape and that body shape significantly co‐varies with foraging behaviour. 相似文献
83.
In the industry for the prefabrication of single-family houses, previous research had indicated that individual companies have problems in securing the product quality of incoming softwood timber. This implies that they need to carry out a quality inspection and adjust the softwood timber when it arrives at their facility in order to fit their production. Opinions within the industry concerning product quality deficiencies differ with regard to the handling procedures and the percentage of perceived deficiencies. However, there are prefabricators of single-family houses that need to find additional areas for use for their purchased softwood timber, and spend several working hours on softwood timber to meet the quality criteria agreed upon. A previous study by Eliasson and Gustafsson puts forward a number of proposals regarding the quality deficiencies of softwood timber in this context. The present work transforms some of these proposals into hypotheses and aims at describing and understanding what affects the perception of product quality deficiencies. Questionnaires were used to collect data. The paper concludes that the purchase volume is indicated to be related to the volume portion of the deficiency in the product quality and that the level of information- and communication-technology support in production (i.e. the degree of automation) is indicated to be related to the inspection activity point. An extension of the proposed hypotheses concludes that the inspection activity point on arrival and/or on delivery into production also affects how companies do perceive product quality deficiencies. Research regarding what affects product quality deficiencies is lacking in recognizing and knowing what is aligned with the perception of product quality deficiencies; the individual companies will have an opportunity to affect and manage their appearance and thereby enhance the use of softwood timber. 相似文献
84.
Structural basis for gluten intolerance in celiac sprue 总被引:1,自引:0,他引:1
Shan L Molberg Ø Parrot I Hausch F Filiz F Gray GM Sollid LM Khosla C 《Science (New York, N.Y.)》2002,297(5590):2275-2279
Celiac Sprue, a widely prevalent autoimmune disease of the small intestine, is induced in genetically susceptible individuals by exposure to dietary gluten. A 33-mer peptide was identified that has several characteristics suggesting it is the primary initiator of the inflammatory response to gluten in Celiac Sprue patients. In vitro and in vivo studies in rats and humans demonstrated that it is stable toward breakdown by all gastric, pancreatic, and intestinal brush-border membrane proteases. The peptide reacted with tissue transglutaminase, the major autoantigen in Celiac Sprue, with substantially greater selectivity than known natural substrates of this extracellular enzyme. It was a potent inducer of gut-derived human T cell lines from 14 of 14 Celiac Sprue patients. Homologs of this peptide were found in all food grains that are toxic to Celiac Sprue patients but are absent from all nontoxic food grains. The peptide could be detoxified in in vitro and in vivo assays by exposure to a bacterial prolyl endopeptidase, suggesting a strategy for oral peptidase supplement therapy for Celiac Sprue. 相似文献
85.
86.
Øyvind Almskar Schnell 《Water, air, and soil pollution》2001,130(1-4):817-824
The subfossil chironomid community of Lille Hovvatn during the last 150 years was analysed. A short sediment core was taken in 1999, sliced at 0.5 cm intervals and dated using the 210Pb method. A total of 1588 specimens were identified, most of them to species level, and 37 chironomid taxa were found. Effects of acidification were recorded on several species up-core, especially in the distribution of Micropsectra insignilobus and Stictochironomus rosenshoeldi. Ordination analysis showed that the chironomid community of Lille Hovvatn is different from the one in Store Hovvatn based on the abundance of the various species, but that the species composition is almost identical in the two lakes. The reappearance of S. rosenshoeldi in the upper 1 cm of the sediment in Lille Hovvatn probably is the first response among the chironomids to the increased pH values measured in the lake during the last decade. 相似文献
87.
Carpet-forming bryophytes (mosses) have been used extensively since the late 1960's in assessing regional and temporal variability of atmospheric heavy-metal deposition. A large-scale decrease in heavy-metal deposition occurred during the 1970's in Sweden, probably also in other parts of northern Europe. The decrease was closely related to known changes in atmospheric emissions. 相似文献
88.
Åke Iverfeldt 《Water, air, and soil pollution》1991,56(1):553-564
A seasonal variation of both particle and gaseous Hg concentrations in the atmosphere is present in south-western Sweden.
An average gaseous Hg level of 3.7 ng m−3 is found in winter, compared to 2.8 ng m−3 in summer. A weak decreasing south-north gradient for gaseous Hg in air over the Nordic countries is also present, with yearly
average values from 3.2 to 2.8 ng m−3. A gradient for particulate Hg is less clear. An air parcel trajectory sector classification of gaseous Hg levels in air,
and to some extent the particulate associated Hg, clearly demonstrates the increased concentrations in the southern sectors,
especially in south-western Sweden where the gaseous Hg increase is about I ng m−3. These observations are consistent with an influence from the European continent. The average concentrations of Hg in precipitation
at the various stations show a pronounced decreasing south-north gradient. A major portion of the total Hg present in precipitation
is associated with particles. For the southern stations, a strong correlation between Hg and sulfate, or pH, is present suggesting
a connection between Hg in precipitation and anthropogenic activities. 相似文献
89.
90.
The collection of Swedish local red clover strains, owned by the Swedish Seed Growers' Association, may serve as an attempt to organize a gene bank for land-races of red clover in Northern Europe. From all 43 strains seed is available and it is hoped that seed of satisfactory germination capacity can be kept available for the future. It may be obtained for research purposes in samples of not larger than 100 grams from the Swedish Seed Association, Uppsala 1, Sweden. 相似文献