全文获取类型
收费全文 | 358篇 |
免费 | 29篇 |
专业分类
林业 | 34篇 |
农学 | 11篇 |
基础科学 | 4篇 |
71篇 | |
综合类 | 38篇 |
农作物 | 11篇 |
水产渔业 | 55篇 |
畜牧兽医 | 101篇 |
园艺 | 18篇 |
植物保护 | 44篇 |
出版年
2024年 | 2篇 |
2023年 | 11篇 |
2022年 | 7篇 |
2021年 | 11篇 |
2020年 | 10篇 |
2019年 | 15篇 |
2018年 | 17篇 |
2017年 | 17篇 |
2016年 | 18篇 |
2015年 | 12篇 |
2014年 | 12篇 |
2013年 | 48篇 |
2012年 | 27篇 |
2011年 | 29篇 |
2010年 | 23篇 |
2009年 | 7篇 |
2008年 | 12篇 |
2007年 | 4篇 |
2006年 | 12篇 |
2005年 | 12篇 |
2004年 | 8篇 |
2003年 | 6篇 |
2002年 | 9篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1968年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有387条查询结果,搜索用时 31 毫秒
91.
The lumbosacral-canal system in birds most likely operates as a sense organ involved in the control of balanced walking and perching, but our knowledge of it is superficial. Penguins constitute interesting objects for the study of this system due to their upright walking, but only the Humboldt penguin, Spheniscus humboldti, and some incomplete fossil penguin synsacra have been studied in this respect. Here, we give an integrative comparative insight into the synsacral canal of extant Emperor penguin, Aptenodytes forsteri, Adelie penguin, Pygoscelis adeliae, and Eocene giant Anthropornis and/or Palaeeudyptes Antarctic penguins, using computed tomography imaging and associated data-extraction methodologies, complemented by analytical approaches ranging from geometric morphometrics to modularity, curvature, and wavelet analyses. We document that the variability in the number of synsacro-lumbar vertebrae is evolutionarily conserved, and all studied synsacra possess osteological correlates of the lumbosacral-canal system. We also found that Eocene and extant Antarctic penguins were separable on the basis of the main direction of the shape-related (size-independent) variability within said system, and A. forsteri was unique in the entire studied set in terms of the relative cranial shift of this compound structure. Moreover, we suggest that the evolutionary processes, shaping both the terrestrial posture and gait, were responsible, in extant penguins, for the increased simplicity and stability of the synsacral canal cross-sectional periodic patterns, as well as pave the way for the lumbosacral-canal system modularity characterized by reduced atomization/complexity. 相似文献
92.
Clémentine MITOYEN Cliodhna QUIGLEY Virginie CANOINE Silvia COLOMBO Simon WÖLFL Leonida FUSANI 《Integrative zoology》2023,18(4):720-735
Some multimodal signals—that is, occurring in more than one sensory modality—appear to carry additional information which is not present when component signals are presented separately. To understand the function of male ring dove's (Streptopelia risoria) multimodal courtship, we used audiovisual playback of male displays to investigate female response to stimuli differing in their audiovisual timing. From natural courtship recordings, we created a shifted stimulus where audio was shifted relative to video by a fixed value and a jittered stimulus, where each call was moved randomly along the visual channel. We presented 3 groups of females with the same stimulus type, that is, control, shifted, and jittered, for 7 days. We recorded their behavior and assessed pre- and post-test blood estradiol concentration. We found that playback exposure increased estradiol levels, confirming that this technique can be efficiently used to study doves’ sexual communication. Additionally, chasing behavior (indicating sexual stimulation) increased over experimental days only in the control condition, suggesting a role of multimodal timing on female response. This stresses the importance of signal configuration in multimodal communication, as additional information is likely to be contained in the temporal association between modalities. 相似文献
93.
94.
The purpose of this study was to investigate the influence of soil geochemistry on the concentrations of Ca, K, Mg, P, Co, Ni, Zn, Mn, Cu, and Fe in cabbage (Brassica oleracea L. var. capitata) grown on acid sulfate (AS) soils in Western Finland. A total of 11 topsoil (0–20 cm) and corresponding cabbage samples and three whole‐soil profiles (≈ 0–260 cm) were collected on three agricultural fields. The concentrations of Co and Zn in cabbage were correlated with the NH4Ac‐extractable (easily available) concentrations in the topsoil, indicating that the uptake of these elements in cabbage is largely governed by soil geochemistry. Yet, the concentrations of Co and Zn in cabbage were not in general elevated relative to that of Finnish average values, although some AS soils showed enriched concentrations of these metals in the soil and cabbage. Significant geochemical differences (e.g., oxidation depth, organic‐matter and S content, pH) were observed among the studied AS soils, while, on the other hand, the concentrations of Ca, K, Mg, P, Ni, Mn, Cu, and Fe in cabbage were relatively similar. The hydroxylamine‐extractable concentrations of these elements in the topsoil were not correlated to those in cabbage, suggesting that uptake is not governed by the oxide‐bound fraction of these elements in the soil. Similarly, the easily available concentrations of Ca, P, Ni, Mn, Cu, and Fe in the topsoil were not correlated to those in cabbage, indicating that uptake is independent of the easily available concentrations in the soil. Hence, it is suggested that cabbage can regulate and thus optimize its concentrations of Ca, P, Ni, Mn, Cu, and Fe. Oxidation depth affected neither the easily available concentrations of Co, Ni, Zn, and Mn in the topsoil nor the concentrations in cabbage. However, the subsoil with a lower oxidation depth, which is to a smaller extent affected by leaching, may partly be enriched in these metals. Nevertheless, these showed no increased concentrations in cabbage. Based on these findings, it is suggested that the large amounts of metals mobilized in AS soils are easily lost to drains, subsequently contaminating nearby waterways and estuaries whereas they are only partly enriched in cabbage and other previously studied crops (oat). 相似文献
95.
Purpose
Due to climatic and topographic conditions, soil erosion is a major problem in Turkey; approximately 86% of the land is suffering from some degree of erosion. This study investigated the relationship between bare soil slope length and the erosion-induced degradation of soil quality and the loss of carbon (C) and nitrogen (N) from the microbial biomass in eroded sediment in the Western Black Sea Region of Turkey. 相似文献96.
97.
The 16S rRNA genes from eight isolates of Renibacterium salmoninarum with different origins and dates of isolation were sequenced to evaluate the possibility to construct a diagnostic PCR system with target sites within this gene. The sequences were found to be identical but for one single position in one of the isolates, and two regions with an adequate number of nucleotide differences as compared to closely related species were identified. Species-specific fluorescent PCR primers complementary to these regions were constructed as well as oligonucleotides for DNA preparation by sequence capture. A mimic molecule was constructed to be used as an internal control. The PCR was specific and allowed the detection of DNA equivalent to 1-10 R. salmoninarum genomes per reaction. The DNA preparation with sequence capture and analysis by PCR with a mimic was found to be a reliable method for analysis of kidneys from fish with BKD. The amount of PCR inhibiting substances present in the tissue was reduced, and the relevant DNA was concentrated in the capture step. Furthermore, the use of the mimic molecule in the system assured that false negative results could be identified. 相似文献
98.
A list is given of aphid parasitoids found in Diyarbakır Province, Turkey. In the survey, performed between 1998 and 2000,
16 species of aphid parasitoids were found on different hosts in Diyarbakır Province.Monoctonus mali is reported for the first time in the Turkish aphid parasitoids fauna.
http://www.phytoparasitica.org posting Oct. 20, 2003. 相似文献
99.
Phyllonorycter apparella, a new record and a new pest of trembling aspen (Populus tremula) in Turkey
Phyllonorycter apparella (Herrich-Schäffer, 1855) (Lepidoptera: Gracillariidae) is a new record for the Turkish fauna and a new trembling aspen(Populus tremula L.) pest for Turkey. Its biology, damage and infestation ratio were studied in Sankami?. (Kars), Turkey, during 1996 and 1997.P. apparella has one generation a year. The developmental stages of the pest are described briefly. P.apparella hibernates in the adult stage. At the beginning of June, the adults appear. Females deposit their eggs on both leaf surfaces, generally one by one, 7–10 days after emerging. The early instars (sap-feeding larvae) start to mine mostly from the underside of leaves. Each mine has one larva, and each leaf may have up to 26 mines. The last instar (tissue-feeding larva) begins to pupate in the mine after mid August. The adults emerge from mid September to the beginning of October, and move to the trunks of old pine trees, where they hibernate in bark crevices. The infestation level may be as high as 90% of the leaves on some trees. 相似文献
100.
The effect of soil amended with stalks of sunflower (Helianthus annuus L.), alfalfa (Medicago sativa L.) and Hungarian vetch (Vicia pannonica Crantz) on onion bulb rot caused byFusarium oxysporum Schlecht. f.sp.cepae (Hanz.) Snyder Hansen andAspergillus niger v. Tieghem was tested in a soil naturally infested with the pathogens under field conditions. All treatments significantly
reduced bulb rot incidence. The fungal and antibacterial populations varied among all of the amended tested soils. Heterotrophic
fungal populations were more effective than heterotrophic bacterial populations in the suppression of disease. The highest
population of fungal microflora was found in plots amended with sunflower stalks. The carbon-to-nitrogen ratio and available
moisture content of amended soils have an indirect suppressive role on disease, by increasing the heterotrophic fungal population.
http://www.phytoparasitica.org posting June 18, 2002. 相似文献