全文获取类型
收费全文 | 1892篇 |
免费 | 160篇 |
专业分类
林业 | 251篇 |
农学 | 93篇 |
基础科学 | 14篇 |
354篇 | |
综合类 | 125篇 |
农作物 | 87篇 |
水产渔业 | 204篇 |
畜牧兽医 | 684篇 |
园艺 | 49篇 |
植物保护 | 191篇 |
出版年
2024年 | 4篇 |
2023年 | 23篇 |
2022年 | 47篇 |
2021年 | 68篇 |
2020年 | 57篇 |
2019年 | 54篇 |
2018年 | 122篇 |
2017年 | 102篇 |
2016年 | 98篇 |
2015年 | 57篇 |
2014年 | 72篇 |
2013年 | 123篇 |
2012年 | 152篇 |
2011年 | 136篇 |
2010年 | 72篇 |
2009年 | 80篇 |
2008年 | 132篇 |
2007年 | 125篇 |
2006年 | 96篇 |
2005年 | 85篇 |
2004年 | 77篇 |
2003年 | 75篇 |
2002年 | 62篇 |
2001年 | 37篇 |
2000年 | 16篇 |
1999年 | 10篇 |
1998年 | 8篇 |
1997年 | 5篇 |
1996年 | 8篇 |
1995年 | 12篇 |
1994年 | 7篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1972年 | 3篇 |
1971年 | 1篇 |
1968年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有2052条查询结果,搜索用时 15 毫秒
991.
992.
Here we present molecular evidence demonstrating that malaria parasites bearing high-level pyrimethamine resistance originally arrived in Africa from southeast Asia. The resistance alleles carried by these migrants are now spreading across Africa at an alarming rate, signaling the end of affordable malaria treatment and presenting sub-Saharan Africa with a public health crisis. 相似文献
993.
994.
Despite the general in vitro susceptibility of Staphylococcus aureus isolates that cause infectious bovine mastitis, the pathogen remains difficult to eradicate with the available antibiotics. The capacity to survive intracellularly has been proposed as a factor contributing to the persistence of S. aureus in the bovine mammary gland. The costs associated with the use of cows or goats to assess the in vivo efficacy of new antibacterial compounds constitute a major drawback. Therefore, in the present study, a mouse model of intramammary infection has been characterized for in vivo testing of new experimental drugs. An inoculum of 100 CFU of S. aureus per gland caused an important level of infection with minimal tissue damage as observed at 24 h post-inoculation. By microscopy, polymorphonuclear neutrophil cell infiltration of the infected mammary glands was observed to increase over time. At 12-24 h of infection, the pathogen was primarily found alive and dividing in neutrophils and occasionally within mammary epithelial cells. Intramuscular or intravenous injections of cephapirin at t = 0 and 10 h reduced the number of CFU/g of gland in a dose-dependent manner. In conclusion, the mouse model of infectious mastitis proposed here is suitable for primary evaluation of experimental drugs after parenteral treatment of intramammary infection with a pathogen such as S. aureus that presents both intracellular and extracellular phases of growth. 相似文献
995.
Mustafa Y. Canbolat Kenan Barik Ramazan Çakmakçi Fikrettin şahin 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2013,63(4):324-332
Abstract Biofertilizers are an alternative to mineral fertilizers for increasing soil productivity and plant growth in sustainable agriculture. The objective of this study was to evaluate possible effects of three mineral fertilizers and four plant growth promoting rhizobacteria (PGPR) strains as biofertilizer on soil properties and seedling growth of barley (Hordeum vulgare) at three different soil bulk densities, and in three harvest periods. The application treatments included the control (without bacteria inoculation and mineral fertilizers), mineral fertilizers (N, NP and P) and plant growth promoting rhizobacteria species (Bacillus licheniformis RC04, Paenibacillus polymyxa RC05, Pseudomonas putida RC06, and Bacillus OSU-142) in sterilized soil. The PGPR, fungi, seedling growth, soil pH, organic matter content, available P and mineral nitrogen were determined in soil compacted artificially to three bulk density levels (1.1, 1.25 and 1.40 Mg m?3) at 15, 30, and 45 days of plant harvest. The results showed that all the inoculated bacteria contributed to the amount of mineral nitrogen. Seed inoculation significantly increased the count of bacteria and fungi. Data suggest that seed inoculation of barley with PGPR strains tested increased root weight by 9–12.2%, and shoot weight by 29.7–43.3% compared with control. The N, NP and P application, however, increased root weight up to 18.2, 25.0 and 7.4% and shoot weight by 31.6, 43.4 and 26.4%, respectively. Our data show that PGPR stimulate barley growth and could be used as an alternative to chemical fertilizer. Soil compaction hampers the beneficial plant growth promoting properties of PGPR and should be avoided. 相似文献
996.
Önder Türkmen Atilla Dursun Metin Turan Çeknas Erdinç 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2013,63(3):168-174
The effects of calcium and humic acid on seed germination, growth and macro- and micro-nutrient contents of tomato (Lycopersicon esculentum L.) seedlings in saline soil conditions were evaluated. Different levels of humic acid (0, 500, 1000 and 2000 mg kg?1) and calcium (0, 100, 200 and 400 mg kg?1) were applied to growth media treated with 50 mg NaCl kg?1 before sowing seeds. Seed germination, hypocotyl length, cotyledon width and length, root size, shoot length, leaf number, shoot and root fresh weights, and shoot and root dry weights of the plant seedlings were determined. Macro- and micro-nutrient (N, P, K, Ca, Mg, S, Cu, Fe, Mn and Zn) contents of shoot and root of seedlings were also measured. Humic acid applied to the plant growth medium at 1000 mg kg?1 concentration increased seedling growth and nutrient contents of plants. Humic acid not only increased macro-nutrient contents, but also enhanced micro-nutrient contents of plant organs. However, high levels of humic acid arrested plant growth or decreased nutrient contents. Levels of 100 and 200 mg kg?1 Ca2+ application significantly increased N, Ca and S contents of shoot, and N and K contents of root. 相似文献
997.
Gerola Gislaine Passarella Boas Naiza Vilas Caetano Josiane Tarley César Ricardo Teixeira Gonçalves Affonso Celso Dragunski Douglas Cardoso 《Water, air, and soil pollution》2013,224(2):1-11
The impact of three commercially available nanoparticles (NPs) on trichloroethylene (TCE) adsorption onto granular activated carbon (GAC) was investigated. TCE adsorption isotherm and column breakthrough experiments were conducted in the presence and absence of silicon dioxide, titanium dioxide, and iron oxide nanoparticles. A rapid small-scale column test (RSSCT) was assessed for its ability to predict TCE adsorption in pilot-scale GAC in the presence and absence of NPs. Zeta potential of the three NPs and the GAC were measured. Particle size distribution of the NP dispersions was analyzed as a function of time. The surface area and the pore size distribution of the virgin and the exhausted GAC were obtained along with transmission electron microscopy and Fourier transform infrared spectroscopy analysis. The effect of NPs was found to be a function of their zeta potential, concentration, and particle size distribution. Due to their electrical charge, NPs attached to the GAC and blocked the pores and thus reduced the access to the internal pore structure. However, due to the fast adsorption kinetics of TCE, no effect from the three NPs was observed in the isotherm and kinetic studies. The RSSCT, on the other hand, accurately predicted the pilot-column TCE breakthrough in the presence of NPs. 相似文献
998.
Carla Verônica Corrêa Aline Mendes de Sousa Gouveia Natália de Brito Lima Lanna Ana Emília Barbosa Tavares Veridiana Zocoler Mendonça Felipe Girotto Campos 《Journal of plant nutrition》2013,36(16):2048-2056
AbstractThe current study aimed to evaluate the effect of split application of potassium (K) fertilizer on the production and quality of sweet potatoes. Ten treatments were evaluated in factorial design (3?×?3?+?1): three doses of potassium (60, 90, and 120?kg K2O ha?1); three application types (100% applied at planting; 50% applied at planting and 50% was given as topdressing; 25% applied at planting and 75% was given as topdressing) and one control (without the application of K2O either at planting or topdressing). The experiment used a randomized complete block design and four repetitions. The following parameters were studied: root number; root fresh matter per plant; total dry matter; yield; total macronutrient extraction; sugar content of starch; and commercial starch. The production characteristics of the roots presented a significant interaction between the factors doses of potassium and application types (parcelaments). Finally, better results were obtained when potassium was applied 50% at planting and 50% as topdressing. 相似文献
999.
Felipe Augusto Reis Gonçalves André Mundstock Xavier de Carvalho Leonardo Angelo de Aquino 《Journal of plant nutrition》2013,36(16):1884-1899
AbstractThe aim of this study was to evaluate the effect of forms of application and application rates of phosphate fertilizer on the agronomic characteristics of carrot. A field experiment was carried out in a 2?×?7 factorial arrangement, consisting of two forms of application of the P source (over the whole area or specifically in the strip of the double row), and seven application rates of P2O5 in randomized blocks, with four replicates. Shoot dry matter yield increased linearly, and root dry matter yield increased exponentially with an increase in P rate. Total and commercial yields increased exponentially, with higher yield for P application over the whole area. However, the agronomic efficiency for site-specific application was higher. Higher rates of P application caused increases in the soil attributes and technical traits of carrot, and the application of phosphorus fertilizer is more efficient when performed in a site-specific manner. 相似文献
1000.
Mehmet Dinçsoy 《Journal of plant nutrition》2013,36(20):2757-2772
AbstractThis study was conducted in the farmer field between the years 2014 and 2015. In this study, 3 doses of potassium (K) (0, 10, and 20?kg da?1) of K2SO4 (50% K2O) fertilizer and 3 doses of humic acid (HA) (0, 20, and 40?kg da?1) (85% HA) were used. Increase in the HA dose reflected significant effects on pH, salt, organic matter, phosphorus, magnesium, iron, and manganese contents of the experiment area at p?.01 level. It was determined that increased potassium applications affected the salt, magnesium (Mg), iron (Fe), and copper (Cu) contents at p?.01 level. Increased HA application on plant growth criteria had a significant effect on biological yield, grain yield, and harvest index (p?.01). However, K did not reflect any effect on the growth stage of wheat. Increased number of HA applications on grain and straw nutrient content were found to have significant (p?.01) effects on P, K, Ca, Mg, Fe, and Zn. Increased potassium applications had an effect on the P, K, Mg, Fe, and Zn contents with a significant level (p?.01). It was observed that HA applications were more effective than potassium applications on both general soil properties and yield and nutrient content. 相似文献