全文获取类型
收费全文 | 3036篇 |
免费 | 165篇 |
专业分类
林业 | 106篇 |
农学 | 104篇 |
基础科学 | 8篇 |
402篇 | |
综合类 | 588篇 |
农作物 | 99篇 |
水产渔业 | 179篇 |
畜牧兽医 | 1509篇 |
园艺 | 45篇 |
植物保护 | 161篇 |
出版年
2021年 | 40篇 |
2020年 | 44篇 |
2019年 | 49篇 |
2018年 | 42篇 |
2017年 | 41篇 |
2016年 | 40篇 |
2015年 | 52篇 |
2014年 | 48篇 |
2013年 | 112篇 |
2012年 | 101篇 |
2011年 | 148篇 |
2010年 | 64篇 |
2009年 | 73篇 |
2008年 | 116篇 |
2007年 | 98篇 |
2006年 | 116篇 |
2005年 | 100篇 |
2004年 | 103篇 |
2003年 | 103篇 |
2002年 | 84篇 |
2001年 | 65篇 |
2000年 | 75篇 |
1999年 | 60篇 |
1998年 | 30篇 |
1997年 | 35篇 |
1995年 | 28篇 |
1994年 | 41篇 |
1993年 | 57篇 |
1992年 | 57篇 |
1991年 | 65篇 |
1990年 | 63篇 |
1989年 | 57篇 |
1988年 | 57篇 |
1987年 | 45篇 |
1986年 | 65篇 |
1985年 | 48篇 |
1984年 | 41篇 |
1983年 | 40篇 |
1982年 | 29篇 |
1981年 | 36篇 |
1980年 | 31篇 |
1979年 | 43篇 |
1978年 | 33篇 |
1976年 | 29篇 |
1975年 | 34篇 |
1973年 | 36篇 |
1972年 | 38篇 |
1971年 | 43篇 |
1970年 | 32篇 |
1969年 | 37篇 |
排序方式: 共有3201条查询结果,搜索用时 15 毫秒
81.
Yasuyoshi Miyake Bimol Chandra Roy Masashi Ando Tokihiko Okada Yoshifumi Sawada Manabu Seoka 《Journal Of Aquatic Food Product Technology》2013,22(2):196-208
The effects of fasting on the quality of the dorsal and ventral ordinary muscles from cultured Pacific bluefin tuna (Thunnus orientalis) during chilled storage were investigated. Tuna were subjected to fasting for 2 days in the summer or 6 days in the winter prior to harvesting. The breaking strength of the dorsal ordinary muscle sampled in the summer increased until 24 h and then decreased. There were no significant differences in the lipid and glycogen content of the ordinary muscle after 9 h of storage between the controls and either fasting group. The pH of the ordinary muscle subjected to summer and winter fasting was higher than in the controls after 24–48 h of storage. However, the relationship between the pH and glycogen content was unclear. The metmyoglobin content during chilled storage was lower in the ordinary muscles from either fasting group than in the controls. In conclusion, fasting for 6 days in the winter improved the color stability of the ordinary muscle without a decline in its lipid content. 相似文献
82.
Assessment of Biogas use as an Energy Source from Anaerobic Digestion of Brewery Wastewater 总被引:1,自引:0,他引:1
Bahar Kasapgil Ince Orhan Ince G. Ken Anderson Semiha Arayici 《Water, air, and soil pollution》2001,126(3-4):239-251
Energy recovery from a crossflow ultrafiltration (UF) membraneunit employed in order to improve the performance of an anaerobic contact digester for the treatment of brewery wastewater was assessed. The performance of the pilot-scale anaerobic UF membrane system was studied for over 15 months. At steady-state conditions, an organic loading rate of 28.5 kg COD m-3 d-1, a hydraulic retention time of 4.2 days and overall COD and BOD removal efficiencies of 99% and almost 100% were achieved, respectively. Percent methane in biogas was found to be in a range of 67–79% with the corresponding methane yield of 0.28–0.35 m3 CH4 kg-1 CODremoved. The potential energy recovery from the system treating brewery wastewater at an OLR of 28.5 kg COD m-3 d-1 was 87 MJ d-1 which would enable to maintain all energy requirements of the feed pump, mixing and heating of the reactor contents. In addition to this, 71% of the energy requirement for recirculating the reactor content through the membranes would also be recovered. 相似文献
83.
Tarik Mitran Pabitra Kumar Mani Nirmalendu Basak Debasis Mazumder Manabendra Roy 《Archives of Agronomy and Soil Science》2016,62(1):1-18
A study on the rice–wheat cropping system was conducted at Bidhan Chandra Krishi Viswavidyalaya, West Bengal, India, to assess the effects of long-term manuring and fertilization on transformation of the inorganic phosphorus (P) fraction in soil after 22 years of the crop cycle. Soil samples were collected after Kharif from seven treated plots having different types of organic amendments like farm yard manure, paddy straw and green manuring with 50% substitution of nitrogen levels in rice crop only. The result showed that the yield trend of rice was maintained due to the buildup of P from various organic inputs. Although cultivation for 22 years without adding any fertilizer caused a significant decrease in almost all the forms of P viz. avail-P, saloid P, iron phosphorus fraction (Fe–P), aluminum phosphorus fraction (Al–P), calcium phosphorus fraction (Ca–P) and total P in control. Partial substitution of inorganic fertilizer N (50%) with organics, however, caused a significant increase in almost all the P fractions in soil over the control. The relative abundance of all the fractions of inorganic P irrespective of treatments was as follows: Fe–P > reductant soluble P fraction > occluded P > Al–P > Ca–P > saloid P. Saloid and Fe–P were the dominating fractions responsible for 92% variation of available P and total P levels, respectively. 相似文献
84.
The application of zinc (Zn) fertilizer to lentil is an agronomic strategy that has the potential to improve yield and enhance grain Zn concentration. A pot study was conducted to determine if Zn fertilizer applied to three popular Saskatchewan lentil cultivars could increase yield and concentration of Zn in the grain. The effects of soil and foliar applied Zn forms, including ZnSO4, Zn chelated with EDTA, Zn lignosulphonate, and a control were evaluated. Forms of Zn were not found to significantly increase yield (P = 0.828) or grain Zn concentration (P = 0.708) in any of the lentil cultivars tested. Fertilization with soil applied ZnSO4 resulted in significantly (P < 0.0001) higher amounts of residual available Zn in the soil relative to other Zn treatments. Soil fertilized with ZnSO4 had 1.13 mg kg?1 diethylenetriaminepentaacetic acid (DTPA)-extractable Zn compared to 0.84 mg Zn kg?1 and 0.77 mg Zn kg?1 in the soil and foliar applied chelated Zn, respectively. 相似文献
85.
Mak Chanratana Gwang Hyun Han Manoharan Melvin Joe Aritra Roy Choudhury Seshadri Sundaram Md. Abdul Halim 《Archives of Agronomy and Soil Science》2018,64(11):1489-1502
Methylobacterium oryzae CBMB20, a promising plant growth promoting bacteria (PGPB) and a biocontrol agent, was immobilized in different formulations such as wet chitosan, dry chitosan, wet alginate and dry alginate and were tested for tomato plant growth promotion. Chitosan solution (1.5%) with pH 5.5–6.0 and 90 min contact time was found optimal for immobilization. The chitosan formulations showed better entrapment efficiency and good degradability resistance apart from slow release of cells under prolonged incubation. Survivability of bacteria (80%) was observed in wet chitosan formulation even after 90 days of storage at 4°C. The spermosphere survival of bacteria was high in both dry and wet chitosan formulations applied soils even after 21 days under greenhouse conditions. While the alginate formulation degraded fully, partial degradation of chitosan formulation was observed even after 30 days, indicating its ability to support the survival of M. oryzae CBMB20 in soil. Plants inoculated with wet chitosan formulation registered 1.3 fold increase in the shoot and root length and dry weight compared to other treatments. Hence, chitosan formulation supporting better plant growth compared to alginate will be a better carrier for taking bacteria to the plant rhizosphere and thereby promote plant growth. 相似文献
86.
McCann MC Trujillo WA Riordan SG Sorbet R Bogdanova NN Sidhu RS 《Journal of agricultural and food chemistry》2007,55(10):4034-4042
The next generation of biotechnology-derived products with the combined benefit of herbicide tolerance and insect protection (MON 88017) was developed to withstand feeding damage caused by the coleopteran pest corn rootworm and over-the-top applications of glyphosate, the active ingredient in Roundup herbicides. As a part of a larger safety and characterization assessment, MON 88017 was grown under field conditions at geographically diverse locations within the United States and Argentina during the 2002 and 2003-2004 field seasons, respectively, along with a near-isogenic control and other conventional corn hybrids for compositional assessment. Field trials were conducted using a randomized complete block design with three replication blocks at each site. Corn forage samples were harvested at the late dough/early dent stage, ground, and analyzed for the concentration of proximate constituents, fibers, and minerals. Samples of mature grain were harvested, ground, and analyzed for the concentration of proximate constituents, fiber, minerals, amino acids, fatty acids, vitamins, antinutrients, and secondary metabolites. The results showed that the forage and grain from MON 88017 are compositionally equivalent to forage and grain from control and conventional corn hybrids. 相似文献
87.
Variation of polymeric proteins affects wheat end‐use quality. This research investigated associations of polymeric proteins with dough mixing strength and breadmaking characteristics in a near‐homogenous population of 139 recombinant inbred lines (RILs) derived from a cross between two hard red spring wheat breeding lines. Flours from the RILs grown at three locations were analyzed for molecular weight (MW) distribution of SDS‐extractable and unextractable proteins using size‐exclusion HPLC protocol. Correlations were calculated between mixing and breadmaking properties and HPLC absorbance data obtained a 0.01‐min retention time interval to identify protein fractions that had a significant effect on the quality traits. Very high MW polymeric proteins in the unextractable fraction had more distinct and positive associations with dough mixing strength and bread loaf volume than did other polymeric protein fractions, whereas extractable polymeric had negative influence. Consequently, the ratio of unextractable very high MW polymeric proteins to extractable polymeric proteins had greater correlations with dough mixing parameters than other HPLC absorbance area data. Covariate‐effect biplots also visually validated positive effects of unextractable very high MW polymeric proteins and negative effects of extractable polymeric proteins on mixing properties and loaf volume across three growing locations. 相似文献
88.
Summary Denitrification (using the acetylene block method) was determined in earthworm casts and soils from permanent, drained or undrained pasture plots fertilized with 0 or 200 kg N ha-1 year-1 as ammonium nitrate. Rates of N2O production from soil cores were about three times higher from the fertilized than from the unfertilized plots while drainage had a relatively small effect. Denitrification rates from casts were 3–5 times higher than those from soil irrespective of the drainage treatment. Casts generally had higher NO
inf3
sup-
, NH
inf4
sup+
, and moisture contents, and higher microbial respiration rates than soil. Rates of N2O production were determined primarily by NO
inf3
sup-
supply, secondarily by moisture; available C did not appear to limit denitrification in these pastures. Estimates of the potential contribution of casts to denitrification ranges from 10.1% of 29.3 kg ha-1 year-1 from the unfertilized, drained plot to 22% of 82.5 kg ha-1 year-1 from the fertilized undrained plot. 相似文献
89.
The critical load concept is now accepted throughout Europe as a means of estimating the sensitivity of key components of aquatic and terrestrial ecosystems to atmospheric inputs of sulphur (S) and nitrogen (N). Current UK freshwater maps, based on steady-state water chemistry, are derived using a critical acid neutralising capacity (ANCLIM) value of zero eql–1, which is based on the probability of occurrence of salmonid fish in lakes. In practice most acidification damage to salmonid fish occurs in nursery streams at the emergence and first feeding stages. In general a clear relationship exists between salmon (Salmo salar L.) and trout (S. trutta L.) densities in Scottish streams and ANC values. However, differences between sites depend on which ANC value is used (eg maximum, minimum or mean). By contrast, when the exceedance of critical loads is compared with salmonid densities the relationship is less clear because many exceeded sites have good salmonid densities. Many of these latter sites are found in north-west Scotland where sea-salt inputs are high and ANC is usually greater than zero eql–1, although diatom-based studies indicated slight acidification of these waters, with a point of change in diatom flora close to ANC=20 eql–1. These false exceedances are probably due to preferential adsorption of acidic SO4 deposition which results in an overestimate of exceedance values. All sites with a mean ANC 0 are fishless but some sites with negative minimum ANC values had normal salmonid densities. Consequently a mean ANCLIM value of zero in the critical load equations for UK freshwaters appears to be too low to protect salmonid stocks. Values between 20–50 eql–1 represent a more realistic range if prevention of long term damage to salmonid stocks is to be achieved. 相似文献
90.
A method tor direct visual or photomicrographic enumeration of soil propagules in soil-agar films and soil smears, stained with a mixture ofeuropium(III) ttienoyltrifluoroacetonate and the disodium salt of 4,41-bis(4-anilino-6-bis(2-hydroxyethyl)amino-S-triazin-2-ylamino)2,21-stilbene disulphonic acid, abbreviated to Eu(TTA)3 and fluorescent brightener (FB), respectively, is described.Soil-agar suspensions at 55–60°C were introduced into haemocytometer sample chambers of 100 μm and 20 μm depth which gave soil-agar film thicknesses of 25 μm and 12 μm, respectively, after air-drying. Soil smears air-dried on 1.25 cm2 and 1.0 cm2 areas of glass slide were 5.2–6.0 μm and 6.0–8.0 μm thick, respectively.The Eu(TTA)3 is best formulated in 50% (v/v) ethanol. The best concentrations of Eu(TTA)3 and FB for staining soil propagules were 2 mM and 25 μM. respectively. A staining period of 18 h for soil-agar films and 90–120 min for soil smears was found to be optimal. The optimum volumes of 50% ethanol for rinsing soil-agar films and soil smears were found to be 12.5 and 5.0 ml. respectively.Lack of in-depth focusing on agar films 25 μm thick resulted in 15–17 per cent error in enumerations. The 12 μm agar films and soil smears required little in-depth focusing and were acceptable for photomicrographic recording of numbers of soil propagules. It is concluded that incident u.v. photomicrographic recording of soil propagule numbers in thin agar films or soil smears is a practical solution to operator fatigue likely to occur during direct microscopy. 相似文献