全文获取类型
收费全文 | 323篇 |
免费 | 4篇 |
专业分类
林业 | 44篇 |
农学 | 5篇 |
基础科学 | 2篇 |
108篇 | |
综合类 | 50篇 |
农作物 | 7篇 |
水产渔业 | 24篇 |
畜牧兽医 | 61篇 |
园艺 | 12篇 |
植物保护 | 14篇 |
出版年
2023年 | 3篇 |
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 7篇 |
2018年 | 4篇 |
2017年 | 11篇 |
2016年 | 2篇 |
2015年 | 8篇 |
2014年 | 5篇 |
2013年 | 14篇 |
2012年 | 17篇 |
2011年 | 16篇 |
2010年 | 3篇 |
2009年 | 8篇 |
2008年 | 15篇 |
2007年 | 23篇 |
2006年 | 21篇 |
2005年 | 13篇 |
2004年 | 9篇 |
2003年 | 17篇 |
2002年 | 10篇 |
2001年 | 9篇 |
2000年 | 7篇 |
1999年 | 3篇 |
1998年 | 7篇 |
1996年 | 2篇 |
1995年 | 14篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 6篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1968年 | 2篇 |
1963年 | 3篇 |
1947年 | 4篇 |
1934年 | 1篇 |
排序方式: 共有327条查询结果,搜索用时 468 毫秒
241.
E Rozema R Popescu H Sonderegger CW Huck J Winkler G Krupitza E Urban B Kopp 《Journal of agricultural and food chemistry》2012,60(29):7204-7210
Sphingolipid metabolites regulate cellular processes such as cell proliferation, differentiation, and apoptosis. In this study, glucocerebrosides (GluCer) from rhizomes of Arisaema amurense and Pinellia ternata were fully characterized using 1- and 2-dimensional nuclear magnetic spin resonance (NMR) and circular dichroism (CD) spectroscopy and tandem collision-induced dissociation mass spectrometry (ESI-MS/CID-MS). Three new acylated and seven known GluCer were elucidated with 4,8-sphingadienine (4,8-SD, d18:2) as backbone. 4,8-SD is a metabolite after enzymatical hydrolysis of GluCer in the gut lumen. In this study, 4,8-SD was hydrolyzed from GluCer and chromatographically purified on silica gel. In contrast to the GluCer, 4,8-SD showed cytotoxic effects in the WST-1 assay. GluCer with 4,8-SD as sphingoid backbone are present in plants consumed as food, such as spinach, soy, and eggplant. 相似文献
242.
Harald Sverdrup Todd C. McDonnell Timothy J. Sullivan Bengt Nihlgård Salim Belyazid Beat Rihm Ellen Porter William D. Bowman Linda Geiser 《Water, air, and soil pollution》2012,223(1):371-387
The ForSAFE-VEG model was used to estimate atmospheric nitrogen deposition and climate effects on soil chemistry and ground
vegetation in alpine and subalpine zones of the northern and central Rocky Mountains region in the USA from 1750 to 2500.
Model simulations for a generalized site illustrated how the critical load of atmospheric nitrogen deposition could be estimated
to protect plant biodiversity. The results appear reasonable compared with past model applications in northern Europe. Atmospheric
N deposition critical loads estimated to protect plant biodiversity were 1 to 2 kg N/ha/year. This range could be greater,
depending on the values selected for critical site-specific parameters (precipitation, temperature, soil chemistry, plant
nutrient uptake, and any eventual harvest of biomass) and the amount of biodiversity change allowed. 相似文献
243.
Ira Handayani Hamada Saad Shanti Ratnakomala Puspita Lisdiyanti Wien Kusharyoto Janina Krause Andreas Kulik Wolfgang Wohlleben Saefuddin Aziz Harald Gross Athina Gavriilidou Nadine Ziemert Yvonne Mast 《Marine drugs》2021,19(6)
Indonesia is one of the most biodiverse countries in the world and a promising resource for novel natural compound producers. Actinomycetes produce about two thirds of all clinically used antibiotics. Thus, exploiting Indonesia’s microbial diversity for actinomycetes may lead to the discovery of novel antibiotics. A total of 422 actinomycete strains were isolated from three different unique areas in Indonesia and tested for their antimicrobial activity. Nine potent bioactive strains were prioritized for further drug screening approaches. The nine strains were cultivated in different solid and liquid media, and a combination of genome mining analysis and mass spectrometry (MS)-based molecular networking was employed to identify potential novel compounds. By correlating secondary metabolite gene cluster data with MS-based molecular networking results, we identified several gene cluster-encoded biosynthetic products from the nine strains, including naphthyridinomycin, amicetin, echinomycin, tirandamycin, antimycin, and desferrioxamine B. Moreover, 16 putative ion clusters and numerous gene clusters were detected that could not be associated with any known compound, indicating that the strains can produce novel secondary metabolites. Our results demonstrate that sampling of actinomycetes from unique and biodiversity-rich habitats, such as Indonesia, along with a combination of gene cluster networking and molecular networking approaches, accelerates natural product identification. 相似文献
244.
Arne Steffenrem Harald Kvaalen Knut Sigmund Dalen Olav A. Høibø 《Scandinavian Journal of Forest Research》2014,29(5):506-514
We have described a high-throughput method for ring width and relative wood density analysis of unprepared increment cores based on conventional computer tomography scanners (CT scanners) used in health care. The method was developed for analysis of 5-mm increment cores collected in forest genetic and tree breeding trials. For these studies, the relative differences between individuals are more important than the exact value. The method is highly efficient in terms of quantitative data collection from large number of samples. There are, however, limitations in terms of resolution and accuracy on very small volumes of wood that must be considered when using the method to measure individual growth rings or increment cores thinner than 5 mm. However, in studies comprising large number of samples, the use of cost-efficient CT scanning on the major part of the material, combined with more laborious high-resolution scanning on sub-samples can be a good combination for efficient determination of radial variation in growth rate and wood density. 相似文献
245.
246.
The two enantiomers of the insecticide fipronil were made by preparative HPLC. The insecticidal activities of the racemic mixture and the two enantiomers against selected agricultural or household pests (cotton stainer, Dysdercus cingulatus F; grain weevil, Sitophilus granarius L and house fly, Musca domestica L) were determined. There was no significant difference in acute or residual activity between the racemic mixture and the enantiomers of fipronil, indicating that there is no preferred chiral form of the compound in these key species of important insects. This observation clearly suggests that there is no major scope for marketing the insecticide in a one-enantiomer form. 相似文献
247.
Roland F.?GrafEmail author Kurt?Bollmann Werner?Suter Harald?Bugmann 《Landscape Ecology》2005,20(6):703-717
The role of scale in ecology is widely recognized as being of vital importance for understanding ecological patterns and processes.
The capercaillie (Tetrao urogallus) is a forest grouse species with large spatial requirements and highly specialized habitat preferences. Habitat models at
the forest stand scale can only partly explain capercaillie occurrence, and some studies at the landscape scale have emphasized
the role of large-scale effects. We hypothesized that both the ability of single variables and multivariate models to explain
capercaillie occurrence would vary with the spatial scale of the analysis. To test this hypothesis, we varied the grain size
of our analysis from 1 to just over 1100 hectares and built univariate and multivariate habitat suitability models for capercaillie
in the Swiss Alps. The variance explained by the univariate models was found to vary among the predictors and with spatial
scale. Within the multivariate models, the best single-scale model (using all predictor variables at the same scale) worked
at a scale equivalent to a small annual home range. The multi-scale model, in which each predictor variable was entered at
the scale at which it had performed best in the univariate model, did slightly better than the best single-scale model. Our
results confirm that habitat variables should be included at different spatial scales when species-habitat relationships are
investigated. 相似文献
248.
249.
Harald Pothmann Jessica Müller Isabella Pothmann Alexander Tichy Marc Drillich 《Reproduction in domestic animals》2019,54(2):350-357
The objectives of this study were as follows: (a) to assess the reproducibility of polymorphonuclear neutrophil (PMN) cell counts at five predefined endometrial sites (corpus uteri, left horn base, right horn base, left horn tip and right horn tip) and (b) to determine the agreement for the diagnosis of subclinical endometritis (SE) between the different endometrial sites. Forty milking cows between 28 and 34 days post‐partum were enrolled for endometrial sampling using cytobrush technique. Intraclass correlation coefficient (ICC) was calculated to evaluate the reproducibility of PMN counts at different sites. The right horn base was found to have the greatest agreement of PMN counts with the other endometrial sites (ICC = 0.66–0.85). Twenty‐eight of 40 cows showed no signs of clinical endometritis and were used for evaluation of agreement for the diagnosis of SE, analysed by using Cohen´s kappa (κ) statistics. Agreement for SE diagnosis with PMN cut‐off ≥5% was greatest between the right horn base and the right horn tip (κ = 0.84), and with PMN cut‐off ≥18% between the right horn base and left horn tip (κ = 1.0), respectively. The results indicate that the right horn base can be regarded as suitable for cytobrush sampling. The probability to detect an animal positive for SE (PMN ≥ 5%) with a single cytobrush sampling was 51.0%; thus, a second sampling is recommended to improve the accuracy. 相似文献
250.