全文获取类型
收费全文 | 173篇 |
免费 | 9篇 |
国内免费 | 3篇 |
专业分类
林业 | 3篇 |
农学 | 6篇 |
31篇 | |
综合类 | 26篇 |
农作物 | 8篇 |
水产渔业 | 15篇 |
畜牧兽医 | 67篇 |
园艺 | 4篇 |
植物保护 | 25篇 |
出版年
2022年 | 2篇 |
2021年 | 1篇 |
2020年 | 2篇 |
2019年 | 3篇 |
2018年 | 7篇 |
2017年 | 4篇 |
2015年 | 3篇 |
2014年 | 2篇 |
2013年 | 5篇 |
2012年 | 12篇 |
2011年 | 6篇 |
2010年 | 7篇 |
2009年 | 8篇 |
2008年 | 10篇 |
2007年 | 8篇 |
2006年 | 5篇 |
2005年 | 7篇 |
2004年 | 5篇 |
2003年 | 10篇 |
2002年 | 4篇 |
2001年 | 10篇 |
2000年 | 5篇 |
1999年 | 6篇 |
1998年 | 2篇 |
1997年 | 7篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1983年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1954年 | 1篇 |
1948年 | 1篇 |
1937年 | 1篇 |
1896年 | 1篇 |
排序方式: 共有185条查询结果,搜索用时 109 毫秒
71.
M. Kenis S. Bacher R. H. A. Baker E. Branquart S. Brunel J. Holt P. E. Hulme A. MacLeod J. Pergl F. Petter P. Pyšek G. Schrader A. Sissons U. Starfinger U. Schaffner 《EPPO Bulletin》2012,42(1):21-27
Assessing the potential environmental impact of alien plants and plant pests is notoriously difficult. New protocols have been developed in the framework of the EC project PRATIQUE to provide guidance on environmental impact assessment in the EPPO pest risk analysis (PRA) decision‐support scheme and enhance consistency between risk assessors and risk ratings for different pests. A set of questions with rating guidance and examples is provided, and individual scores are summarized into final scores, using a hierarchy of risk matrices, to assess current and potential environmental impacts. Two separate protocols are available: for alien plants and for other pests. These protocols could also be used to assess environmental impact in other PRA schemes as well as to assign alien species to regional black lists or to prioritize species for management decisions. 相似文献
72.
A hybrid between an induced tetraploid of Hordeum chilense (2n = 28 = HchHchHchHch) and Triticum aestivum var. ‘Chinese Spring’ (2n = 42 = AABBDD) has been produced to test gene effects of this wild barley on homoeologous pairing in wheat. Cytological investigations in metaphase I have shown that the hybrid, which is perennial like H. chilense but morphologically more similar to the wheat parent, possesses the expected genome composition HchHch ABD and a stable euploid chromosome number of 2n = 35. Pairing among the homologous H. chilense chromosomes was almost complete. The level of non-homologous chromosome association proved to be lower than the range of pairing known from euhaploids of ‘Chinese Spring’. 相似文献
73.
In comparison to the surrounding soil, hot spot effects of middens of the epianecic earthworm Lumbricus terrestris were determined under different field conditions on a loamy sand. The impact of 3 different management systems was studied: 1. unmulched; 2. straw mulching; 3. intermediate crop: Sinapis alba. Furthermore, we considered 2 different crops (bean, lupine) and their growth stages. We monitored different enzyme activities and abiotic parameters of soil at 6 sampling dates between April and August 1998 parallel to abundances of microfauna (soil protozoa) and mesofauna (Enchytraeidae, Collembola, mites). The analysis of earthworm middens revealed enhanced enzyme activities and increased mesofaunal abundances. Differences between midden and reference samples were significant during the whole vegetation period and became maximal during ripening of crops. We found a distinct but not significant increase in individual numbers of soil flagellates in midden areas during leafing and heading of crops. Values of the studied parameters tended to be higher in bean plots but generally the crop impact on midden properties was not significant. Our results showed a significant positive synergistic effect between earthworm middens and intermediate crop. Straw mulching supported the hot spot effects of middens. 相似文献
74.
Natland JH Rosendahl B Hekinian R Dmitriev Y Fodor RV Goll RM Hoffert M Humphris SE Mattey DP Petersen N Roggenthen W Schrader EL Srivastava RK Warren N 《Science (New York, N.Y.)》1979,204(4393):613-616
The Galápagos mounds sea-floor hydrothermal system is at least 300,000 years old and once produced manganese-poor sediments, which nearly blanketed the area of the present mounds field. Present-day mound deposits are limited manganese-rich exposures, suggesting that the system has changed from rock-to water-dominated and has diminished in intensity with time. 相似文献
75.
Molecular cloning of the chicken progesterone receptor 总被引:16,自引:0,他引:16
O M Conneely W P Sullivan D O Toft M Birnbaumer R G Cook B L Maxwell T Zarucki-Schulz G L Greene W T Schrader B W O'Malley 《Science (New York, N.Y.)》1986,233(4765):767-770
To define the functional domains of the progesterone receptor required for gene regulation, complementary DNA (cDNA) clones encoding the chicken progesterone receptor have been isolated from a chicken oviduct lambda gt11 cDNA expression library. Positive clones expressed antigenic determinants that cross-reacted with six monospecific antibodies derived from two independent sources. A 36-amino acid peptide sequence obtained by microsequencing of purified progesterone receptor was encoded by nucleotide sequences in the longest cDNA clone. Analysis of the amino acid sequence of the progesterone receptor deduced from the cDNA clones revealed a cysteine-rich region that was homologous to a region found in the estrogen and glucocorticoid receptors and to the avian erythroblastosis virus gag-erb-A fusion protein. Northern blot analysis with chicken progesterone receptor cDNA's indicated the existence of at least three messenger RNA species. These messages were found only in oviduct and could be induced by estrogens. 相似文献
76.
The aphid-vectored Potato virus Y (PVY) is currently seen as an important limiting factor in the production of potatoes in many countries. Using a content-analysis
approach, we investigated the German extension literature for recommendations regarding the control of PVY. Media included
articles from periodicals addressing farmers and agricultural textbooks published in the last five decades (1955–2004). In
the current literature (1995–2004), the clearly dominating strategy was found to be insecticidal control, although this strategy
has been subject to some criticism in the scientific literature. Over the last five decades we also found a strongly increasing
representation of insecticidal strategies. Furthermore, over this period of time, information diversity, measured as the number
of different strategies proposed per article or per textbook, decreased consistently.
Electronic supplementary material The online version of this article () contains supplementary material that is available to authorized users. 相似文献
77.
A radical polymerization process that yields well-defined polymers normally obtained only through anionic polymerizations is reported. Atom transfer radical polymerizations of styrene were conducted with several solubilizing ligands for the copper(I) halides: 4,4'-di-tert-butyl, 4,4'-di-n-heptyl, and 4,4'-di-(5-nonyl)-2,2'-dipyridyl. The resulting polymerizations have all of the characteristics of a living polymerization and displayed linear semilogarithmic kinetic plots, a linear correlation between the number-average molecular weight and the monomer conversion, and low polydispersities (ratio of the weight-average to number-average molecular weights of 1.04 to 1.05). Similar results were obtained for the polymerization of acrylates. 相似文献
78.
Schrader F 《Science (New York, N.Y.)》1948,107(2772):155-159
79.
80.
Polarized and unpolarized neutron scattering was used to measure the wave vector- and frequency-dependent magnetic fluctuations in the normal state (from the superconducting transition temperature, Tc = 35 kelvin, up to 350 kelvin) of single crystals of La1.86Sr0.14CuO4. The peaks that dominate the fluctuations have amplitudes that decrease as T-2 and widths that increase in proportion to the thermal energy, kBT (where kB is Boltzmann's constant), and energy transfer added in quadrature. The nearly singular fluctuations are consistent with a nearby quantum critical point. 相似文献