全文获取类型
收费全文 | 217篇 |
免费 | 15篇 |
专业分类
林业 | 36篇 |
农学 | 7篇 |
基础科学 | 6篇 |
48篇 | |
综合类 | 10篇 |
农作物 | 7篇 |
水产渔业 | 35篇 |
畜牧兽医 | 59篇 |
园艺 | 6篇 |
植物保护 | 18篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 8篇 |
2020年 | 9篇 |
2019年 | 16篇 |
2018年 | 18篇 |
2017年 | 11篇 |
2016年 | 13篇 |
2015年 | 7篇 |
2014年 | 14篇 |
2013年 | 10篇 |
2012年 | 12篇 |
2011年 | 19篇 |
2010年 | 8篇 |
2009年 | 8篇 |
2008年 | 8篇 |
2007年 | 7篇 |
2006年 | 7篇 |
2005年 | 12篇 |
2004年 | 2篇 |
2003年 | 6篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1985年 | 2篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1970年 | 1篇 |
1969年 | 3篇 |
1962年 | 1篇 |
排序方式: 共有232条查询结果,搜索用时 218 毫秒
101.
Jan Kopecky Marek Omelka Jitka Novotna Yvan Moënne-Loccoz Marketa Sagova-Mareckova 《Soil biology & biochemistry》2011,43(3):697-700
The diversity of environmental mycobacteria was studied in water-logged acidic forest soil. Mycobacteria were assessed in upper and lower soil horizons and summer and winter seasons using T-RFLP and sequencing of 16S rRNA gene produced with Mycobacterium-specific primers. Mycobacteria diversity differed between both the two seasons and soil horizons. Cloning revealed the presence of mycobacteria belonging to three major clusters recognized within the genus, i.e. fast-growing, intermediate, and slow-growing species, with unprecedented abundance and diversity of the latter. Two novel clusters of sequences unrelated to the known mycobacteria were identified. This study raises the possibility that forest wetlands could serve as environmental reservoirs for an unexplored diversity of mycobacteria including those related to pathogenic species. 相似文献
102.
103.
Baran Agnieszka Klimkowicz-Pawlas Agnieszka Ukalska-Jaruga Aleksandra Mierzwa-Hersztek Monika Gondek Krzysztof Szara-Bąk Magdalena Tarnawski Marek Spałek Iwona 《Journal of Soils and Sediments》2021,21(6):2418-2431
Journal of Soils and Sediments - The aims of the study were to investigate the interaction between fractions of organic matter and polycyclic aromatic hydrocarbons (PAHs) in bottom sediments and to... 相似文献
104.
This paper addresses the oxidation by ultraviolet radiation of methylparaben, a ubiquitous and suspicious preservative which is massively added to cosmetics and personal care products. Experiments included pH and temperature variation, as well as several experimental conditions such as presence/absence of hydrogen peroxide, titanium dioxide, or some different water matrix (surface water or ground water). Results were evaluated under the line source spherical emission model, so quantum yield was the adequate target variable for explaining the process. A modified Arrhenius correlation including pH level was used for modelling the whole system. 相似文献
105.
Performance tests of Northern mirror carp (M72) and three different crossbreds were conducted in semi‐intensive pond conditions from the larval stage up to market size. The aim of this study was to evaluate the possible utilization of new hybrid combinations (M72 × PL – Poho?elice mirror carp) and (M72 × Dor – Israeli mirror carp), and to compare them with a hybrid widely reared as a commercial product (M72 × M2 – Hungarian mirror carp) and with M72 purebred. The testing model was derived from similar studies carried out in the conditions of the Czech Republic, where an internal control of different scale cover is used to eliminate all non‐genetic effects. ancova revealed at market size significantly better growth in M72 × Dor (1 619±28.3 g; LS mean±SE) and M72 × PL (1475±29.8 g) compared with M72 (1278±26.3 g). Survival during the test of 3 years duration was significantly the best in the M72 × Dor hybrid as were the dressing out parameters measured at market size, even if these were significantly different only in proportion of fillets with skin (39.1±0.28%). Interestingly, the crossbred M72 × M2 commonly used by Czech fishermen showed for both, growth (1371±26.2 g) and survival, the lowest values among crossbreds and with regard to dressing out parameters mostly among all tested groups. 相似文献
106.
Otomar Linhart Marek Rodina Martin Flajshans Nicola Mavrodiev Jana Nebesarova David Gela Martin Kocour 《Aquaculture International》2006,14(1-2):9-25
The tench Tinca tinca is an interesting fish from the viewpoint of polyploidy and related atypical reproduction aspects. Triploid tench were produced
artificially. Studies of spermiation as well as of sperm motility and structure were performed on several triploid and diploid
males simultaneously with individual experimental crosses with diploid females to define their reproductive capacities. The
testes of triploids visually looked less developed in the most of cases with lower sperm production (0.05 cm3 sperm per male), GSI and weight of testes compared to diploids (0.58 cm3 sperm per male). Analysis of variance showed significant influence of ploidy level on the percentage of motile spermatozoa.
Triploidy did not change percentage of live spermatozoa and velocity of spermatozoa at the first time of sperm movement. The
study of sperm structure by scanning electron microscopy revealed that most sperm cells were of normal structure with some
anomalies. Sperm heads of triploid and diploid males were mostly round-shaped, 1.86±0.2 and 1.6±0.18 μm in diameter. The midpiece
of triploid spermatozoa was slightly narrower than that of diploid ones with typical cylindrical shape. Flow cytometry revealed
sperm cells of triploids to be largely aneuploid (1.47 n) with high mosaic DNA, oscillating from haploid DNA content (1.0 n)
to diploid DNA content (1.9 n). Experimental crosses between triploid males and diploid females revealed that these males
were capable to stimulate effective development with relatively high level of fertilization and hatching rates from 0 to 70%.
In conclusion, triploidization does not seem to guarantee sterility of tench. 相似文献
107.
108.
Marcin Polak Jarosław Wiącek Marek Kucharczyk Robert Orzechowski 《European Journal of Forest Research》2013,132(5-6):931-941
The very rapid development of the road infrastructure in recent years has adversely affected the natural environment. The main effects of this have been the loss or deteriorating quality of habitats, the mortality of animals due to collisions with road vehicles, the withdrawal of birds as a result of disturbance and excessive noise in the neighbourhood of roads. In this study, we attempted to define the influence of a busy road on a breeding community of woodland birds. Individuals were counted using the point method at 54 observation points located at three various distances (60, 310, 560 m) from the road. At each point, we determined the habitat parameters and the intensity of noise. In total, 995 individuals of 39 species were recorded on the study plot. This study showed that the area was homogeneous with respect to habitat. The number of birds per point increased with distance from the road. Species diversity was lower near the road. The density of nine common species increased with distance from the road. Great Tit Parus major and Song Thrush Turdus philomelos preferred the neighbourhood of the road, whereas the numbers of the other species were the highest in the middle row of points. The number and species diversity of birds were correlated with the pattern of sound propagation across our study area. Our results showed that the species particularly sensitive to road traffic were those nesting near the ground and with low-frequency calls. 相似文献
109.
110.
Aleš Lebeda Michaela Sedlářová Marek Petřivalský Jitka Prokopová 《European journal of plant pathology / European Foundation for Plant Pathology》2008,122(1):71-89
Plant pathogenic oomycetes, including biotrophic downy mildews and hemibiotrophs/necrotrophs such as Phytophthora and Pythium, cause enormous economic losses on cultivated crops. Lettuce breeders and growers face the threat of Bremia lactucae, the causal agent of lettuce downy mildew. This pathogen damages leaf tissues and lettuce heads and is also frequent on wild
Asteraceae plants. The interactions of Lactuca spp. with B. lactucae (abbr. lettuce–Bremia) display extreme variability, due to a long co-evolutionary history. For this reason, during the last 30 years, the lettuce–Bremia pathosystem has been used as a model for many studies at the population, individual, organ, tissue, cellular, physiological
and molecular levels, as well as on genetic variability and the genetics of host–parasite interactions. The first part of
this review summarizes recent data on host–parasite specificity, host variability, resistance mechanisms and genetics of lettuce–Bremia interactions. The second part focuses on the development infection structures. Phenotypic expression of infection, behaviour
of B. lactucae on leaf surfaces, the process of penetration, development of primary infection structures, hyphae and haustoria are discussed
in relation to different resistance mechanisms. In the third part, the components of host resistance and the variability of
defence responses are analysed. The role of reactive oxygen species (ROS), antioxidant enzymes, nitric oxide (NO), phenolic
compounds, reorganization of cytoskeleton, electrolyte leakage, membrane damage, cell wall disruption, hypersensitive reaction
and plant energetics are discussed in relation to defence responses. In general, the extreme variability of interactions between
lettuce and Bremia, and their phenotypic expression, results from diversity of the genetic background. Different mechanisms of resistance are
conditioned by an orchestra of defence responses at the tissue, cell, and molecular levels. The various events responsible
for defence involve a complex interaction of the processes and reactions mentioned above. This review also provides an overview
on the timing of pathogen development, host pathological anatomy, cytology and physiology of lettuce–Bremia associations. The significance of these factors on the expression of different resistance mechanisms (non-host and host resistance,
race-specific and race non-specific resistance, field resistance) is discussed. 相似文献