全文获取类型
收费全文 | 523篇 |
免费 | 21篇 |
专业分类
林业 | 42篇 |
农学 | 6篇 |
基础科学 | 6篇 |
93篇 | |
综合类 | 67篇 |
农作物 | 10篇 |
水产渔业 | 34篇 |
畜牧兽医 | 228篇 |
园艺 | 17篇 |
植物保护 | 41篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2021年 | 13篇 |
2020年 | 12篇 |
2019年 | 17篇 |
2018年 | 15篇 |
2017年 | 11篇 |
2016年 | 17篇 |
2015年 | 13篇 |
2014年 | 16篇 |
2013年 | 19篇 |
2012年 | 33篇 |
2011年 | 44篇 |
2010年 | 23篇 |
2009年 | 19篇 |
2008年 | 38篇 |
2007年 | 38篇 |
2006年 | 40篇 |
2005年 | 42篇 |
2004年 | 27篇 |
2003年 | 20篇 |
2002年 | 33篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 7篇 |
1998年 | 5篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1971年 | 1篇 |
1967年 | 1篇 |
1934年 | 1篇 |
排序方式: 共有544条查询结果,搜索用时 15 毫秒
41.
42.
E.?A.?CatchpoleEmail author Y.?Fan B.?J.?T.?Morgan T.?H.?Clutton-Brock T.?Coulson 《Journal of Agricultural, Biological & Environmental Statistics》2004,9(1):1-26
A detailed and extensive mark-recapture-recovery study of red deer on the island of Rum forms the basis of the modeling of
this article. We analyze male and female deer separately, and report results for both in this article, but use the female
data to demonstrate our modeling approach. We provide a model-selection procedure that allows us to describe the survival
by a combination of age-classes, with common survival within each class, and senility, which is modeled continuously as a
parametric function of age. Dispersal out of the study area is modeled separately. Survival and dispersal probabilities are
examined for the possible influence of both environmental and individual covariates, including a range of alternative measures
of population density. The resulting model is succinct and biologically realistic. We compare and contrast survival rates
of male and female deer of different ages and compare the factors that affect their survival. We demonstrate large differences
in the rate of senescence between males and females even though their senescence begins at the same age. The differences between
the sexes suggest that, in population modeling of sexually size-dimorphic species, it is important to identify sex-specific
survival functions. 相似文献
43.
Michele R. Derrick Jarvis L. Moyers Keith A. Yarborough Mike Warren 《Water, air, and soil pollution》1984,21(1-4):171-181
Aerosol chemistry, precipitation and visibility parameters are currently being measured at Big Bend National Park in Texas. This is part of a large-scale air resource evaluation program which the National Park Service is sponsoring in several southwestern national parks and monuments to determine the potential impact of local and distant pollutant sources on the environmental quality within these areas. Analysis of aerosol samples collected at six sites in the Southwest indicates that soil-derived components, organic materials and the acid-base ions of sulfate, nitrate, and ammonium are the major constituents of suspended airborne particulate matter in the remote areas of the arid region. Comparison of particulate matter chemistry and precipitation chemistry data at Big Bend National Park shows consistent features which indicate that the airborne alkaline soil material and NH3 largely neutralize the atmospheric acidic species of H2SO4 and HNO3. Given the similarity of the particulate matter composition and loading at the other monitoring sites, it is suggested that the trace chemical composition of precipitation will be similar in many remote regions of the Southwest. 相似文献
44.
45.
A map of the interactome network of the metazoan C. elegans 总被引:1,自引:0,他引:1
Li S Armstrong CM Bertin N Ge H Milstein S Boxem M Vidalain PO Han JD Chesneau A Hao T Goldberg DS Li N Martinez M Rual JF Lamesch P Xu L Tewari M Wong SL Zhang LV Berriz GF Jacotot L Vaglio P Reboul J Hirozane-Kishikawa T Li Q Gabel HW Elewa A Baumgartner B Rose DJ Yu H Bosak S Sequerra R Fraser A Mango SE Saxton WM Strome S Van Den Heuvel S Piano F Vandenhaute J Sardet C Gerstein M Doucette-Stamm L Gunsalus KC Harper JW Cusick ME Roth FP Hill DE Vidal M 《Science (New York, N.Y.)》2004,303(5657):540-543
46.
Davis S Begon M De Bruyn L Ageyev VS Klassovskiy NL Pole SB Viljugrein H Stenseth NC Leirs H 《Science (New York, N.Y.)》2004,304(5671):736-738
In Kazakhstan and elsewhere in central Asia, the bacterium Yersinia pestis circulates in natural populations of gerbils, which are the source of human cases of bubonic plague. Our analysis of field data collected between 1955 and 1996 shows that plague invades, fades out, and reinvades in response to fluctuations in the abundance of its main reservoir host, the great gerbil (Rhombomys opimus). This is a rare empirical example of the two types of abundance thresholds for infectious disease-invasion and persistence- operating in a single wildlife population. We parameterized predictive models that should reduce the costs of plague surveillance in central Asia and thereby encourage its continuance. 相似文献
47.
48.
Hillenmeyer ME Fung E Wildenhain J Pierce SE Hoon S Lee W Proctor M St Onge RP Tyers M Koller D Altman RB Davis RW Nislow C Giaever G 《Science (New York, N.Y.)》2008,320(5874):362-365
Genetics aims to understand the relation between genotype and phenotype. However, because complete deletion of most yeast genes ( approximately 80%) has no obvious phenotypic consequence in rich medium, it is difficult to study their functions. To uncover phenotypes for this nonessential fraction of the genome, we performed 1144 chemical genomic assays on the yeast whole-genome heterozygous and homozygous deletion collections and quantified the growth fitness of each deletion strain in the presence of chemical or environmental stress conditions. We found that 97% of gene deletions exhibited a measurable growth phenotype, suggesting that nearly all genes are essential for optimal growth in at least one condition. 相似文献
49.
Torchia M 《Science (New York, N.Y.)》2011,331(6019):858; author reply 858
50.
A century ago, W. G. MacCallum identified distinct male and female forms in malaria parasites of both birds and humans. Since then, scientists have been puzzled by the high female-to-male ratios of parasites in Plasmodium infections and by the mechanism of sex determination. The sex ratio of malaria parasites was shown to become progressively more male as conditions that allow motility and subsequent fertilization by the male parasites become adverse. This resulted from an increased immune response against male gametes, which coincides with intense host erythropoietic activity. Natural and artificial induction of erythropoiesis in vertebrate hosts provoked a shift toward male parasite production. This change in parasite sex ratio led to reduced reproductive success in the parasite, which suggests that sex determination is adaptive and is regulated by the hematologic state of the host. 相似文献