全文获取类型
收费全文 | 400篇 |
免费 | 39篇 |
专业分类
林业 | 24篇 |
农学 | 21篇 |
基础科学 | 2篇 |
92篇 | |
综合类 | 16篇 |
农作物 | 25篇 |
水产渔业 | 50篇 |
畜牧兽医 | 173篇 |
园艺 | 9篇 |
植物保护 | 27篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 9篇 |
2020年 | 5篇 |
2019年 | 13篇 |
2018年 | 10篇 |
2017年 | 10篇 |
2016年 | 17篇 |
2015年 | 19篇 |
2014年 | 10篇 |
2013年 | 24篇 |
2012年 | 31篇 |
2011年 | 32篇 |
2010年 | 32篇 |
2009年 | 24篇 |
2008年 | 32篇 |
2007年 | 24篇 |
2006年 | 20篇 |
2005年 | 15篇 |
2004年 | 19篇 |
2003年 | 15篇 |
2002年 | 19篇 |
2001年 | 9篇 |
2000年 | 11篇 |
1999年 | 7篇 |
1998年 | 4篇 |
1996年 | 3篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1963年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有439条查询结果,搜索用时 18 毫秒
131.
Eugenia J. Olguín Gloria Sánchez-Galván Teresa Pérez-Pérez 《Water, air, and soil pollution》2007,181(1-4):135-147
Salvinia minima combines several advantages for being used in aquatic phytoremediation. The objectives of this work were to compare the growth kinetics and productivity of S. minima and Spirodela polyrrhiza in high-strength synthetic organic wastewater (HSWW) and to evaluate the growth characteristics of S. minima in various culture media, including anaerobic effluents from pig wastewater (PWAE). It was found that the Relative Growth Rate (RGR) of S. minima was significantly higher (p?<?0.05) compared to the RGR of S. polyrrhiza in Hutner Medium (HM) and in HSWW. Also, S. minima showed a 1.5 fold productivity and a 2.3 fold productivity, compared to S. polyrrhiza in HM and HSWW, respectively. Diauxic growth of S. minima was observed preferentially under pH control and there was a simultaneous consumption of two nitrogen sources. Productivity of S. minima was similar in pig waste anaerobic effluents (PWAE) and in HM without ammonium nitrate and amended with ammonium sulphate (MHM?+?AS), at an initial NH4 concentration of 35 mg l?1. Above this level, the productivity was found to decrease as the initial ammonium concentration increased, in both media. Growth was completely inhibited at 140 mg l?1 in the PWAE. In summary, S. minima is a better option than S. polyrrhiza for treating high-strength organic wastewater and lagoons should be operated at a maximum initial ammonium–nitrogen concentration of 70 mg l?1 and at a pH of 5.0 or 6.0. Likewise, the initial density should be maintained in the range of 7 to 15 g dw m?2. 相似文献
132.
Influence of distillation system,oak wood type,and aging time on volatile compounds of cider brandy 总被引:3,自引:0,他引:3
A study of the influence of distillation system, oak wood type, and aging time on volatile compounds of cider brandy was carried out. Acetaldehyde and acetaldehyde diethyl acetal were influenced by distillation technology, oak wood type, and maturation time. The majority ester, ethyl ethanoate, increased during aging, the highest level of this ester being detected in spirits distilled by double distillation. The alcohols of higher molecular weight were better recovered in the rectification column than in the double distillation system. Ethanoate esters decreased throughout aging of the spirits, and their degradation velocity was lower in distillates obtained from double distillation. Fatty acids and their ethyl esters presented the opposite evolution during aging, detecting an increase in ethyl esters and a decrease in their corresponding fatty acids. An increase of 1,1,3-triethoxypropane was detected during aging. French oak contributes the trans isomer of beta-methyl-gamma-octalactone and American oak contributes the cis isomer. 相似文献
133.
Duffort OA Polo F Lombardero M Díaz-Perales A Sánchez-Monge R García-Casado G Salcedo G Barber D 《Journal of agricultural and food chemistry》2002,50(26):7738-7741
Pru p 3 is a lipid transfer protein (LTP) that has been identified as the major peach (Prunus persica) allergen. However, little is known about the amount present in both raw and processed foodstuffs. Moreover, the in vivo release upon consumption of peach-containing foods remains unclear. We have developed a sensitive monoclonal antibody-based ELISA for Pru p 3. The method has been applied to measure the allergen levels in foodstuffs and the allergen release under different physiological conditions. A significant variability in all raw peaches and peach-containing foods tested has been detected. The allergen was extracted more efficiently at a low pH, and it was highly resistant to pepsin. This ELISA will be very useful in controlling the allergen concentration in diagnostics, in evaluating threshold levels in provocation tests, and in detecting hidden allergens in processed foods and cosmetics. 相似文献
134.
Rodríguez Madrera R Blanco Gomis D Mangas Alonso JJ 《Journal of agricultural and food chemistry》2003,51(27):7969-7973
A control of phenolic and furanic compounds in cider brandy was carried out during maturation in oak casks, studying three technological factors: distillation (rectification column vs double distillation), oak wood type (French vs American), and aging time (32 months). Gallic acid and benzoic and cinnamic aldehydes significantly increased during maturation of cider brandies, the highest level of these phenolics being obtained when aging was conducted in French oak casks. Benzoic acids increased during aging, though furanic compounds were not influenced by the time factor. Distillation and wood factors significantly influenced furanic concentration; 5-hydroxymethylfurfural not was detected in fresh spirits and was extracted in the highest proportion in French oak. Volatile furanics, such as 5-methylfurfural, furfural, and 2-furylmethyl ketone, were influenced by the distillation factor, with the use of the double distillation system producing a higher level of these compounds. Scopoletin was the majority coumarin detected in cider brandies, the highest yield of which was obtained with the use of American oak. 相似文献
135.
Soils in the Dry Valleys of Antarctica are considered to be among the world's most extreme environments. These soils are old, cold and dry with low contents of organic carbon and nitrogen. Habitats adjacent to water (lakes and ice melts) have significant biological activity as demonstrated by the presence of algal mats, lichens and small invertebrates, particularly nematodes, tardigrades and rotifers. In contrast, there are extensive areas in the Dry Valleys that are extremely dry with less than 5% moisture content. These soils are often salty and appear to be barren of life as they have a coarse texture due to their lack of plant organic material. In contrast, molecular techniques (DNA extraction from soils, cloning and rDNA sequence analysis) demonstrated the presence of a complex micro-eukaryotic food web whose structure and composition varied with moisture content and location. Micro-eukaryotic communities in soils with 0.2-1.3% moisture were represented by species of the yeast genus Trichosporon and an unidentified clade of micro-eukaryotes, whereas levels from 3.1% to 4.9% contained complex food webs including primary producers (chlorophytes and stramenopiles), symbionts (lichen associated fungi), saprophytes (fungi), predators (alveolates and cercozoans) and fungal nematode parasite/pathogens. The soils had a diversity of species (80 species from 15 sites) with a restricted number (3-21 species) at each site. The sensitive and measurable community structure of the low moisture Dry Valley soils provides an unparalleled opportunity to examine local and global environmental effects on micro-eukaryotic community dynamics with multiple trophic levels. 相似文献
136.
Andrew Smelser Michael Blanco Thomas Lübberstedt Axel Schechert Adam Vanous Candice Gardner 《Plant Breeding》2015,134(3):283-285
The doubled haploid breeding method can produce maize inbred lines faster than traditional methods, but there are challenges associated with it. Sorting haploid from hybrid seed based on visual colour markers is time consuming and can be difficult due to colour inhibitors that obscure pigmentation needed to distinguish between haploid, hybrid and outcrossed seed. In this study, weight was evaluated as a method to sort haploid from hybrid seed. A first experiment utilized two families for analysis in a preliminary study. Eleven haploid and hybrid kernels from both families were weighed for a total of 44 experimental units. A second experiment was carried out using six families, using the same format as the previous, for 132 experimental units. Hybrid seed weighed significantly more than haploid seed in both experiments. However, the interaction between line and kernel type was significant in the second experiment. In conclusion, efficacy of sorting haploid from hybrid kernels based on weight depends on the genotypes involved. 相似文献
137.
- 1. A basin approximation was used to analyse distribution patterns of different components of biodiversity (taxonomic richness, endemicity, taxonomic singularity, rarity) and conservation status of freshwater fish fauna in 27 Mediterranean Iberian rivers.
- 2. Basin area alone explained more than 80% of variation in native species richness. Larger basins featured not only a higher number of native species, but also more endemic and rare species and fewer diversified genera than smaller basins.
- 3. In contrast, smaller basins scored higher community conservation values, owing to their lower degree of invasion by introduced species.
- 4. The presence of dams was the most important factor determining the conservation status of fish communities, and it was also positively associated with the number of introduced species.
- 5. While the most important components of Iberian freshwater fish biodiversity are located in large basins, small unregulated basins feature better conserved fish communities.
138.
Lindsay G Ross Judith Sanchez Blanco Carlos Martínez-Palacios Ilie S Racotta & Mayra Toledo Cuevas 《Aquaculture Research》2007,38(9):909-917
Anaesthesia, sedation and transportation of the Atherinopsid, Menidia estor, were investigated using benzocaine, hypothermia and combinations of the two. The optimum dose rates of benzocaine for sedation of juvenile Chirostoma estor were 15 and 18 mg L−1. When hypothermia was used alone, stable sedation of C. estor was induced at 15 and 12°C, with no mortalities and full recovery after about 8 min. There was synergism when benzocaine and hypothermia were combined, with the optimal combination being at 15°C and 12 mg L−1 benzocaine. Successful transportation was conducted over 3.5 and 8.5 h using combined benzocaine and hypothermia. Aloe vera extract used in the transportation medium reduced scale loss. This work has, for the first time, defined a systematically derived system of safe, long distance, live transportation of this species and others of the genus Menidia. 相似文献
139.
In the dogfish sharkSqualus acanthias different germ cell stages are topographically segregated within the testis. Using this species we have developed methods
for the isolation and culture of Sertoli cells from premeiotic, meiotic and post-meiotic stages of spermatogenesis and present
preliminary evidence for stage-dependent variations in cell morphology and behavior, thymidine incorporation, protein synthesis
and steroidogenesis. The goal of future studies is to determine how maturational changes are regulated in Sertoli cells and,
in turn, to elucidate Sertoli cell-germ cell interactions. 相似文献
140.
Francesc Piferrer Michael Redding Wilfrid DuBois Gloria Callard 《Fish physiology and biochemistry》1993,11(1-6):293-298
Spermatogenesis is a unique developmental sequence involving multiple cell to cell interactions and several categories of regulatory molecules. In contrast to conventional mammalian models in which testicular organization is highly complex, the testis of the dogfish shark Squalus acanthias is technically advantageous for elucidating stage-dependent structural and functional charactericsics and for in vitro regulatory studies. Using incorporation of [3H]thymidine into acid-insoluble molecules as a measure of DNA synthesis by spermatocysts (germ cell/Sertoli cell units) of premeiotic stages, we obtained evidence of a growth inhibitory bioactivity (chalone) within the testis. This activity is differentially distributed (postmeiotic > meiotic > premeiotic), suggesting that more advanced developmental stages, which are upstream in the vascular pathway within the testis, may control the size of the proliferating spermatocyst population and, hence, the advance of less mature stages. These data provide direct evidence for humoral communication between stages of spermatogenesis. 相似文献