全文获取类型
收费全文 | 279篇 |
免费 | 7篇 |
国内免费 | 5篇 |
专业分类
林业 | 40篇 |
农学 | 16篇 |
基础科学 | 2篇 |
47篇 | |
综合类 | 12篇 |
农作物 | 28篇 |
水产渔业 | 38篇 |
畜牧兽医 | 69篇 |
园艺 | 14篇 |
植物保护 | 25篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 9篇 |
2021年 | 13篇 |
2020年 | 15篇 |
2019年 | 15篇 |
2018年 | 14篇 |
2017年 | 13篇 |
2016年 | 13篇 |
2015年 | 12篇 |
2014年 | 8篇 |
2013年 | 26篇 |
2012年 | 19篇 |
2011年 | 25篇 |
2010年 | 19篇 |
2009年 | 13篇 |
2008年 | 12篇 |
2007年 | 9篇 |
2006年 | 6篇 |
2005年 | 6篇 |
2004年 | 7篇 |
2003年 | 11篇 |
2002年 | 3篇 |
2001年 | 3篇 |
2000年 | 6篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1991年 | 1篇 |
1985年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有291条查询结果,搜索用时 16 毫秒
71.
Tyler D Eddy Heike K Lotze Elizabeth A Fulton Marta Coll Cameron H Ainsworth Júlio Neves de Araújo Catherine M Bulman Alida Bundy Villy Christensen John C Field Neil A Gribble Mejs Hasan Steve Mackinson Howard Townsend 《Fish and Fisheries》2017,18(1):40-53
Since the 1950s, invertebrate fisheries catches have rapidly expanded globally to more than 10 million tonnes annually, with twice as many target species, and are now significant contributors to global seafood provision, export, trade and local livelihoods. Invertebrates play important and diverse functional roles in marine ecosystems, yet the ecosystem effects of their exploitation are poorly understood. Using 12 ecosystem models distributed worldwide, we analysed the trade‐offs of various invertebrate fisheries and their ecosystem effects as well as ecological indicators. Although less recognized for their contributions to marine food webs, our results show that the magnitude of trophic impacts of invertebrates on other species of commercial and conservation interest is comparable with those of forage fish. Generally, cephalopods showed the strongest ecosystem effects and were characterized by a strong top‐down predatory role. Lobster, and to a lesser extent, crabs, shrimp and prawns, also showed strong ecosystem effects, but at lower trophic levels. Benthic invertebrates, including epifauna and infauna, also showed considerable ecosystem effects, but with strong bottom‐up characteristics. In contrast, urchins, bivalves, and gastropods showed generally lower ecosystem effects in our simulations. Invertebrates also strongly contributed to benthic–pelagic coupling, with exploitation of benthic invertebrates impacting pelagic fishes and vice versa. Finally, on average, invertebrates produced maximum sustainable yield at lower levels of depletion (~45%) than forage fish (~65%), highlighting the need for management targets that avoid negative consequences for target species and marine ecosystems as a whole. 相似文献
72.
M. Hasan F. Seyis A. G. Badani J. Pons-Kühnemann W. Friedt W. Lühs R. J. Snowdon 《Genetic Resources and Crop Evolution》2006,53(4):793-802
Genetic diversity throughout the rapeseed (Brassica napus ssp. napus) primary gene pool was examined by obtaining detailed molecular genetic information at simple sequence repeat (SSR) loci
for a broad range of winter and spring oilseed, fodder and leaf rape gene bank accessions. The plant material investigated
was selected from a preliminary B. napus core collection developed from European gene bank material, and was intended to cover as broadly as possible the diversity
present in the species, excluding swedes (B. napus ssp. napobrassica (L.) Hanelt). A set of 96 genotypes was characterised using publicly available mapped SSR markers spread over the B. napus genome. Allelic information from 30 SSR primer combinations amplifying 220 alleles at 51 polymorphic loci provided unique
genetic fingerprints for all genotypes. UPGMA clustering enabled identification of four general groups with increasing genetic
diversity as follows (1) spring oilseed and fodder; (2) winter oilseed; (3) winter fodder; (4) vegetable genotypes. The most
extreme allelic variation was observed in a spring kale from the United Kingdom and a Japanese spring vegetable genotype,
and two winter rape accessions from Korea and Japan, respectively. Unexpectedly the next most distinct genotypes were two
old winter oilseed varieties from Germany and Ukraine, respectively. A number of other accessions were also found to be genetically
distinct from the other material of the same type. The molecular genetic information gained enables the identification of
untapped genetic variability for rapeseed breeding and is potentially interesting with respect to increasing heterosis in
oilseed rape hybrids. 相似文献
73.
Kara Emine Erman Pirlak Uğur Özdılek Hasan Göksel 《Water, air, and soil pollution》2004,153(1-4):173-186
Water, Air, &; Soil Pollution - The Province of Ni?de, located in central Anatolia, supplies approximately 25% of the total potato production in Turkey. In order to investigate selected... 相似文献
74.
The kinetics of the reactions of chlorpyrifos-methyl, an organophosphorus insecticide, with hydrogen sulfide (H(2)S) and bisulfide (HS(-)) were determined in well-defined aqueous solutions. The resulting pseudo-first-order rate constant for chlorpyrifos-methyl with bisulfide yielded a second-order rate constant of (2.1 +/- 0.3) x 10(-3) M(-1) s(-1). The second-order rate constant for chlorpyrifos-methyl with hydrogen sulfide is significantly slower than the second-order rate constant with bisulfide. The contribution of H(2)S to the observed degradation rate constant of chlorpyrifos-methyl at concentrations of up to 4 mM H(2)S is not significant. The second-order rate constant of chlorpyrifos-methyl with H(2)S was too low to be measured in this study. The results indicate that HS(-) present at environmentally relevant concentrations may represent an important sink for phosphorothionate triesters in a coastal marine environment, while H(2)S reacts too slowly to be environmentally relevant (pH 6-9). Trichloropyridinol, the major product of hydrolysis of chlorpyrifos-methyl, is only a minor product of the reaction of chlorpyrifos-methyl with bisulfide; however, trichloropyridinol was found to be stable under the experimental conditions. 相似文献
75.
Pharmaceutical industrial waste was collected from Ghaziabad (Cooper Pharma Ltd.) and analyzed for color, odor, specific gravity, turbidity, pH, total solids, suspended solids, dissolved solids, volatile solids, dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), organic and inorganic nitrogen, sulfur, chlorides, sulfates and phosphates. The detrimental effects of industrial waste on microorganisms were studied in the system with lower and higher volumes of the wastes (0.5–12 ml) using glucose substrate as a source of carbon for microorganisms. The cultures of saprophytic and nitrifying bacteria were grown from sewage and pea gravel, respectively, and tested for their nature. 相似文献
76.
SK Shaheenur Islam Holy Akwar Md. Mehedi Hossain Md. Abu Sufian Md. Zakiul Hasan Shovon Chakma Tongkorn Meeyam Warangkhana Chaisowwong Veerasak Punyapornwithaya Nitish C. Debnath Eric Brum Duangporn Pichpol 《Zoonoses and public health》2020,67(6):658-672
Analysis of environmental samples obtained from the Live Poultry Markets (LPMs) of Dhaka City, Bangladesh, has revealed that the highest degree of prevalence of highly pathogenic avian influenza A (HPAI, H5N1), besides other subtypes of the LPAI virus, poses the plausible risk of transmission of these viruses between human and poultry species. The present study was conducted using the OIE risk analysis framework to assess the risk level of each pathway successively. The estimated risk parameters were integrated towards to obtain the overall risk level for each specific HPAI transmission pathway using the matrix adapted by Cristobel Zepeda accompanying other expert consultations. The relevant data obtained from published and unpublished sources, together with survey data of field observations, were used to formulate and confirm the risk pathways and their associated risks. The results revealed that the risk of the release of the HPAI virus was medium when exposure was high. Additionally, the consequence would be considered very high with a medium degree of uncertainty for all parameters. Ultimately, the overall risk for transmission was estimated as medium with a medium degree of uncertainty. The findings of this study reveal that there is a significant threat that HPAI virus transmission could occur among poultry and humans and effectively sustain within the environment of the LPMs. Our findings are primarily focused on public health considerations, the hygienic slaughter of poultry and the relevant cleaning and sanitation practices conducted in the LPMs to support evidence‐based decision‐making processes. The findings of the study have the potential to be used to formulate effective risk reduction measures and can be further adapted in low‐resource settings without major infrastructural changes required of the LPMs. All of which would reduce the risk of HPAI virus release and further lessen the degree of exposure and transmission in established LPMs. 相似文献
77.
Serhat Karaca Sibel Erdoğan Mehtap Güney Cihan Çakmakçı Muammer Sarıbey Aşkın Kor Hasan Ülker 《Animal Science Journal》2021,92(1):e13561
This study examined how inclusion of dried distillers' grains with solubles (DDGS) in finishing lamb diets for different periods affects some physiological indicators and meat quality. A total of 40 male lambs were divided into four groups according to feeding regimen during the 120-day finishing period as follows: C120: no DDGS included in diet for 120 days; D120: DDGS included in diet for 120 days; D75: no DDGS included in diet for 45 days + DDGS included in diet for 75 days; D45: no DDGS included in diet for 75 days + DDGS included in diet for 45 days. Dietary inclusion rate of DDGS was 27.5%. Fattening performance and rumen parameters were not affected by treatment. Feeding regimens had no significant effect on meat quality except the instrumental tenderness and juiciness score. DDGS fed lambs had higher level of total trans fatty acids and n-6/n-3 ratio in meat. 10t-C18:1, 11t-C18:1 and 9c,11t conjugated linoleic acid contents of adipose tissue were higher in all the DDGS groups compared with C120 lambs (p < .001). These results suggest that soybean meal can be replaced with corn DDGS in lamb diets for up to 120 days during the finishing period with no adverse effects on some physiological response feedlot performance and meat quality. 相似文献
78.
Ali Kadivar Habiballah Rashidzadeh Najmeh Davoodian Hasan Nazari Rohallah Dehghani Tafti Heidar Heidari Khoei Hasan Seidi Samani Jahangir Modaresi Ebrahim Ahmadi 《Reproduction in domestic animals》2021,56(2):287-291
Accurate diagnosis of foetal sex in pregnant mare is helpful for many breeders, both for private or commercial purposes. In this study, in order to pre-natal foetal sexing in equine, we used TaqMan duplex real-time PCR to detect the specific regions of SRY and TSPY genes on extracted cell-free foetal DNA from maternal blood. Peripheral blood samples from 50 pregnant Arabian mares with singleton foetuses were collected. Cell-free foetal DNA was extracted from maternal plasma, and duplex real-time PCR assays were performed with TaqMan probes and primers. Amplification of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene was used as control of DNA extraction procedure. From the 50 sampled mares, 28 cases had female and 22 mares had male foetuses. The final results for 46 samples were conclusive, and from them, 43 cases were predicted correctly. Sensitivity, specificity and accuracy of the test were 90.48%, 96% and 93.48%, respectively. In conclusion, a TaqMan duplex real-time PCR was set up to pre-natal detection of foetal sex in equine. The method was fast and decreased the false-positive and false-negative results. The technique can be used as a routine procedure in farms by collecting only a blood sample. 相似文献
79.
Subhankar Biswas Qumrul Ahsan Ahmed Cenna Mahbub Hasan Azman Hassan 《Fibers and Polymers》2013,14(10):1762-1767
A systematic study has been carried out to investigate the mechanical and physical properties of jute, bamboo and coir (brown and white) single fibers. The tensile properties (tensile strength, Young’s modulus and strain to failure) were determined by varying span length. Scanning electron microscopic analysis was also carried out to determine the physical properties of fibers in order to correlate with its strength, Young’s modulus and strain to failure. The Young’s modulus and strain to failure were corrected using newly developed equations. The study revealed that with increasing test span length the Young’s modulus increased and tensile strength as well as strain to failure decreased. This is because no extensometer could be used in this test set-up and machine displacement (denoted by α) was used for the modulus determination. It is also attributed that larger span length helps to minimize the machine displacement compared to smaller ones due to the reduced relative effect of slippage in the clamps. Among all fibers, the Young’s modulus of bamboo fiber was the highest. Jute fiber had smoother surface compared to other three examined fibers. 相似文献
80.
Monira Ahsan Tahmina Akter Zaman Choudhury M. Hasan Chihiro Ito S. K. Nazrul Islam 《Fitoterapia》2000,71(6)
3,5-Dimethoxy-4-geranyloxycinnamyl alcohol (1), 8-methoxy-N-methylflindersine (2), xanthyletin and sesamin have been isolated from petroleum ether extract of the stem bark of Zanthoxylum rhesta. The petroleum ether extract and 8-methoxy-N-methylflindersine showed cytotoxicity on brine shrimp nauplii. 相似文献