全文获取类型
收费全文 | 16000篇 |
免费 | 724篇 |
国内免费 | 59篇 |
专业分类
林业 | 4008篇 |
农学 | 389篇 |
基础科学 | 75篇 |
2482篇 | |
综合类 | 1197篇 |
农作物 | 532篇 |
水产渔业 | 559篇 |
畜牧兽医 | 6242篇 |
园艺 | 346篇 |
植物保护 | 953篇 |
出版年
2022年 | 107篇 |
2021年 | 167篇 |
2020年 | 205篇 |
2019年 | 126篇 |
2018年 | 360篇 |
2017年 | 324篇 |
2016年 | 342篇 |
2015年 | 303篇 |
2014年 | 322篇 |
2013年 | 812篇 |
2012年 | 665篇 |
2011年 | 671篇 |
2010年 | 409篇 |
2009年 | 341篇 |
2008年 | 584篇 |
2007年 | 640篇 |
2006年 | 613篇 |
2005年 | 576篇 |
2004年 | 539篇 |
2003年 | 528篇 |
2002年 | 447篇 |
2001年 | 347篇 |
2000年 | 336篇 |
1999年 | 240篇 |
1997年 | 108篇 |
1996年 | 149篇 |
1995年 | 162篇 |
1994年 | 117篇 |
1993年 | 118篇 |
1992年 | 187篇 |
1991年 | 182篇 |
1990年 | 188篇 |
1989年 | 198篇 |
1988年 | 180篇 |
1987年 | 150篇 |
1986年 | 175篇 |
1985年 | 151篇 |
1984年 | 161篇 |
1983年 | 139篇 |
1982年 | 108篇 |
1981年 | 140篇 |
1980年 | 104篇 |
1979年 | 188篇 |
1978年 | 128篇 |
1974年 | 104篇 |
1973年 | 116篇 |
1972年 | 110篇 |
1971年 | 105篇 |
1970年 | 99篇 |
1969年 | 102篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
Re: Recommendations from the Australian and New Zealand Equine Endocrine Group and the interpretation of plasma endogenous ACTH concentrations for the diagnosis of pituitary pars intermedia dysfunction (PPID)
下载免费PDF全文
![点击此处可从《Australian veterinary journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
122.
Hyperglycaemia in transition dairy cows: Effects of lactational stage and conjugated linoleic acid supplementation on glucose metabolism and turnover
下载免费PDF全文
![点击此处可从《Journal of animal physiology and animal nutrition》网站下载免费的PDF全文](/ch/ext_images/free.gif)
L. Grossen‐Rösti E. C. Kessler A. Tröscher R. M. Bruckmaier J. J. Gross 《Journal of animal physiology and animal nutrition》2018,102(2):483-494
Supplementing conjugated linoleic acid ( CLA ) is supposed to spare glucose due to the milk fat‐depressing effect of the trans ‐10, cis ‐12 CLA isomer, and allows repartitioning nutrients despite an energy deficiency in early lactation. However, there is still a lack of knowledge in terms of the dynamic pattern of the glucose turnover in transition dairy cows. We hypothesized that dairy cows supplemented with CLA have an altered rate of glucose turnover and insulin sensitivity during early lactation. We conducted three consecutive hyperglycaemic clamps (HGC ) in weeks ?2, +2 and +4 relative to parturition in Holstein cows supplemented daily either with 70 g of lipid‐encapsulated CLA (6.8 g trans ‐10, cis ‐12 and 6.6 g of the cis ‐9, trans ‐11 CLA isomer; CLA ; n = 11) or with 56 g of control fat ( CON ; n = 11). From week ?3 up to week +4 relative to parturition, milk yield and dry matter intake (DMI ) were recorded daily, while body weight (BW ) and milk composition were obtained once weekly. Blood samples were taken once weekly and every 30 min during the HGC . Plasma was analysed for concentrations of glucose, fatty acids (FFA ), beta‐hydroxybutyrate (BHB ), insulin, triglycerides and cholesterol. The CLA supplementation did not affect performance and metabolic parameters except for BHB and cholesterol. Furthermore, insulin concentrations and insulin sensitivity were affected by treatment. During the HGC in early lactation, insulin response was lower and decrease in FFA and BHB greater compared with the HGC in week ?2 although glucose target concentration achieved during the steady‐state period was similar for all three HGC . Our findings in terms of insulin and cholesterol suggest that body reserves are preserved through CLA feeding without restraining animal's performance. Furthermore, CLA effects on cholesterol and triglyceride concentrations indicated beneficial effects on hepatic lipid export contributing to an improved efficiency of prevailing metabolites in circulation. 相似文献
123.
Effects of oral supplementation of probiotic strains of Lactobacillus rhamnosus and Enterococcus faecium on diarrhoea events of foals in their first weeks of life
下载免费PDF全文
![点击此处可从《Journal of animal physiology and animal nutrition》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Christina Ströbel Elena Günther Vladimir Urubschurov Annette Zeyner 《Journal of animal physiology and animal nutrition》2018,102(5):1357-1365
Foal first diarrhoea is one of the most prominent problems in the early life of horses. Probiotics might have the potency to prevent or at least diminish neonatal diarrhoea. We hypothesised that the treatment of foals with probiotic strains of Lactobacillus rhamnosus and Enterococcus faecium starting early after birth and then daily over 2 weeks would prevent or mitigate foal heat diarrhoea. The influence of this probiotic treatment on diarrhoea incidence and growth and health performance of young foals was investigated. Thirty‐four foals were randomly allocated to two groups. From day 1 to 14 of life, the foals received either placebo (PG, n = 16) or the probiotic treatment (TG, n = 18). Clinical examination was performed, and the faeces consistency score (FCS, 1–5; with diarrhoea defined by ≤3) was recorded once per day in weeks 1 and 2 and once weekly in weeks 3–8 of life (WL). The body height was measured at birth and after two and eight WL. Diarrhoea occurred in the 1st WL in 19% and 61% of PG and TG foals respectively. In the 1st WL, diarrhoea lasted 0.3 ± 0.8 and 1.6 ± 1.4 days in PG and TG foals respectively. In the 2nd WL, diarrhoea occurred in 94% and 84% of PG and TG foals, respectively, and lasted for 3.0 ± 1.5 and 3.7 ± 1.6 days respectively. At least two periods of diarrhoea developed in 33% and 65% of PG and TG foals respectively. The TG foals grew slightly slower than the PG foals. The results indicated that the probiotic treatment of neonatal foals as performed in this study was not suitable to reduce diarrhoea within the first two WL, because contrary to the hypothesis, the TG foals suffered more frequently and for longer periods from diarrhoea than the PG foals. 相似文献
124.
UV‐light and dietary vitamin D and their effects on ionized calcium and 25‐OH‐D plasma concentrations in captive gentoo penguins (Pygoscelis papua)
下载免费PDF全文
![点击此处可从《Journal of animal physiology and animal nutrition》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ursina Tröndle Hanspeter W. Steinmetz Simon R. Rüegg Anja Müller Annette Liesegang 《Journal of animal physiology and animal nutrition》2018,102(5):1419-1428
In this study, the effect of ultraviolet (UV) light and dietary vitamin D on calcium metabolism in permanently indoor‐housed gentoo penguins (Pygoscelis papua ) was investigated. The study consisted of three periods, each completed with blood samples to analyse plasma concentrations of 25‐OH‐D, 1,25‐(OH)2‐D, ionized (iCa) and total calcium (tCa). During the first study period (D), animals were housed under routine conditions without UV‐light and fed a diet of different fish species, supplemented with 1,000 IU vitamin D per animal and day. The following study period (Baseline) of 28‐day duration consisted of the same diet without any vitamin D supplementation and without UV‐light. During the study period (UVB) artificial UV‐light was added for 3 weeks. The vitamin D content of fish was measured by high‐performance liquid chromatography. It varied between fish species and between facilities, ranging from no measurable content in capelin (Mallotus villosus ) to 7,340 IU vitamin D/kg original matter (OM) in herring (Clupea spp). The average dietary vitamin D content was 311 IU/kg OM at facility 1 and 6,325 IU/kg OM at facility 2, resulting in a vitamin D intake per animal and day without supplementation of 130 IU (25.5 IU/kg body weight BW) and 2,454 IU (438.2 IU/kg BW) respectively. The supplementation of vitamin D elevated significantly the plasma concentrations of 25‐OH‐D by an intraindividual difference of 15 (range ?2 to 59) nmol/L and tCa by 0.1 (0.0–0.3) mmol/L only at facility 2. The exposure to UV‐light raised the blood concentrations of tCa at facility 2 by 0.15 (0.1–0.2) mmol/L, and of iCa and tCa for females at facility 1 by 0.23 (0.13–0.41) mmol/L and 1.8 (1.1–2.5) mmol/L respectively. No significant influence of the study periods (D) and (UVB) was found for the concentrations of 1,25‐(OH)2‐D at both facilities. 相似文献
125.
Food intake and energy expenditure in growing cats with and without a predisposition to overweight
下载免费PDF全文
![点击此处可从《Journal of animal physiology and animal nutrition》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Vivien Ghielmetti Brigitta Wichert Simon Rüegg Diana Frey Annette Liesegang 《Journal of animal physiology and animal nutrition》2018,102(5):1401-1410
Overweight and obesity are multifactorial diseases caused by an imbalance in energy metabolism. An underlying genetic predisposition is often a factor in these conditions. In the cat breeding family of the Institute of Animal Nutrition at the Vetsuisse Faculty, University of Zurich, a segregating overweight phenotype with a genetic contribution was observed. From this breeding family, 26 kittens were followed from birth up to 8 months of age. During this time, food intake was measured using an automatic feeding station, and energy expenditure was investigated using indirect calorimetry at the ages of 4 and 6 months. Dual‐energy X‐ray absorptiometry (DEXA) was performed and blood glucose, leptin and insulin were measured at the ages of 4, 6 and 8 months. The kittens were also weighed daily for the first 2 weeks of life, every second day until weaning and once per week until 8 months of age. The body condition score (BCS) was evaluated monthly between 2 and 8 months of age. The main finding of this study is that a predisposition to overweight is connected to a higher food intake early in life, with no significant alterations in energy expenditure. The leptin blood levels were related to body fat percentage, and insulin sensitivity did not seem to be affected. 相似文献
126.
127.
Longitudinal analysis of allergen‐specific IgE and IgG subclasses as potential predictors of insect bite hypersensitivity following first exposure to Culicoides in Icelandic horses
下载免费PDF全文
![点击此处可从《Veterinary dermatology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
128.
129.
Can additional N fertiliser ameliorate the elevated CO2‐induced depression in grain and tissue N concentrations of wheat on a high soil N background?
下载免费PDF全文
![点击此处可从《Journal of Agronomy and Crop Science》网站下载免费的PDF全文](/ch/ext_images/free.gif)
M. Tausz R. M. Norton S. Tausz‐Posch M. Löw S. Seneweera G. O'Leary R. Armstrong G. J. Fitzgerald 《Journal of Agronomy and Crop Science》2017,203(6):574-583
Elevated CO2 stimulates crop yields but leads to lower tissue and grain nitrogen concentrations [N], raising concerns about grain quality in cereals. To test whether N fertiliser application above optimum growth requirements can alleviate the decline in tissue [N], wheat was grown in a Free Air CO2 Enrichment facility in a low‐rainfall cropping system on high soil N. Crops were grown with and without addition of 50–60 kg N/ha in 12 growing environments created by supplemental irrigation and two sowing dates over 3 years. Elevated CO2 increased yield and biomass (on average by 25%) and decreased biomass [N] (3%–9%) and grain [N] (5%). Nitrogen uptake was greater (20%) in crops grown under elevated CO2. Additional N supply had no effect on yield and biomass, confirming high soil N. Small increases in [N] with N addition were insufficient to offset declines in grain [N] under elevated CO2. Instead, N application increased the [N] in straw and decreased N harvest index. The results suggest that conventional addition of N does not mitigate grain [N] depression under elevated CO2, and lend support to hypotheses that link decreases in crop [N] with biochemical limitations rather than N supply. 相似文献
130.
Modelling Wheat Stomatal Resistance in Hourly Time Steps from Micrometeorological Variables and Soil Water Status
下载免费PDF全文
![点击此处可从《Journal of Agronomy and Crop Science》网站下载免费的PDF全文](/ch/ext_images/free.gif)
An accurate estimation of stomatal resistance (rS) also under drought stress conditions is of pivotal importance for any process‐based prediction of transpiration and the energy budget of real crop canopies and quantification of drought stress. A new model for rS was developed and parameterized for winter wheat using data from field experiments accounting for the influences of net radiation (RNet), air temperature (TAir) and vapour pressure deficit of the atmosphere (VPD) interacting with an average water potential in the rooted soil (ψRootedSoil). rS is simulated with a limiting factor approach as maximum of the metabolic (related to photosynthesis) and hydraulic (related to drought stress) acting influences assuming that, if drought stress occurs, it will dominate stomatal control: rS = max(rS(TAir), rS(RNet), rS(VPD, ψRootedSoil)). This transitional approach is suited to reproduce measured daily time courses of rS with a varying accuracy for the single measurement dates but performed satisfactorily for the whole data set (r2 = 0.63, RMSE = 59 s m?1, EF = 0.60). This new semi‐empiric approach calculates rS directly from external environmental conditions. Therefore, it can be easily implemented in existing model frameworks as link between operational crop growth models that use the concept of radiation use efficiency instead of mechanistic photosynthesis modelling and soil–vegetation–atmosphere transport models. 相似文献