全文获取类型
收费全文 | 274篇 |
免费 | 22篇 |
专业分类
林业 | 38篇 |
农学 | 6篇 |
基础科学 | 4篇 |
67篇 | |
综合类 | 44篇 |
农作物 | 11篇 |
水产渔业 | 16篇 |
畜牧兽医 | 75篇 |
园艺 | 6篇 |
植物保护 | 29篇 |
出版年
2023年 | 3篇 |
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 7篇 |
2019年 | 4篇 |
2018年 | 9篇 |
2017年 | 6篇 |
2016年 | 5篇 |
2015年 | 9篇 |
2014年 | 11篇 |
2013年 | 16篇 |
2012年 | 15篇 |
2011年 | 17篇 |
2010年 | 18篇 |
2009年 | 11篇 |
2008年 | 15篇 |
2007年 | 17篇 |
2006年 | 14篇 |
2005年 | 17篇 |
2004年 | 15篇 |
2003年 | 17篇 |
2002年 | 9篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1975年 | 3篇 |
1974年 | 1篇 |
1969年 | 2篇 |
1956年 | 1篇 |
1949年 | 1篇 |
1932年 | 1篇 |
1925年 | 1篇 |
1901年 | 2篇 |
1896年 | 2篇 |
排序方式: 共有296条查询结果,搜索用时 15 毫秒
1.
2.
Azin Rekowski Monika A. Wimmer Bernd Hitzmann Bernhard Hermannseder Heike Hahn Christian Zrb 《植物养料与土壤学杂志》2020,183(2):260-270
Background: Nitrogen losses is an economic problem for wheat production and a high risk to the environment. Therefore, improved N fertilizer management is a key to increasing the N efficiency and minimizing N losses. To increase N efficiency, enhanced fertilizers such as urea combined with urease inhibitor can be used. Aims: The aim of present study was to evaluate the effects of different N forms on grain storage protein subunits in winter wheat and to examine whether the observed changes correlate with parameters of baking quality. Methods: The investigation was performed over two consecutive years at two locations in Germany. Protein subunits were analyzed by SDS‐PAGE. Results: Protein concentrations were similarly increased after fertilization with ammonium nitrate and urea + urease inhibitor. Analysis of the individual storage protein fractions indicated that both fertilizers specifically enhanced ω‐gliadins and HMW glutenins, but the effect was more pronounced in the ammonium nitrate treatment. Application of urea + urease inhibitor had greater influence on the protein composition and resulted in higher specific baking volume as well as the best fresh keeping ability, in comparison with urea treatment. Conclusion: Considering that the urea + urease inhibitor treatment resulted in almost comparable improvements of NUE and baking quality, with the additional benefit of reduced N losses in combination with easy handling, urea + urease inhibitor can be recommended as a viable alternative to both urea alone and ammonium nitrate treatments. This opens up an opportunity for the reduction of N loss in wheat production when use of urea is preferred. 相似文献
3.
新疆杨(Populus bolleana LAUCHE)是山西省北部乃至中国西北部重要的阔叶树造林树种,但目前发现只有雄性植株,它很可能是一个或几个无性系通过无性繁殖而大规模传播开来,基因变异狭窄,会给造林带来巨大的潜在危险。于2004年到2005年在山西省境内随机采集59个样树,在德国爱博斯瓦尔德大学(FH-Eberswalde)的生态实验室进行了同工酶分析。分析结果显示,在山西省境随机采样的59个新疆杨树中,88%的被猜测为是一个或同样的无性系。初步证实山西省境内的新疆杨造林基因变异有限,这就是说在山西境内新疆杨的造林潜在着巨大的风险。同时就避免或降低这种风险的可能性进行讨论。 相似文献
4.
A 5-year-old Holsteiner gelding from Germany was presented 2 months after a whitish discoloration of the left cornea was observed. Cytologic examination revealed intra- and extracellular globular structures, up to 4 micro m in size, consisting of a central spherical deeply basophilic body surrounded by an unstained halo. The structures were morphologically consistent with Histoplasma spp. Infection with Histoplasma organisms is not endemic in Europe. Topical use of fluconazole was successful in eliminating Histoplasma organisms within 10 days of initiation of treatment. 相似文献
5.
OBJECTIVE: To compare serum concentrations of 1,25-dihydroxycholecalciferol (1,25-[OH]2D3) and 25-hydroxycholecalciferol (25-[OH]D3) in healthy control dogs and dogs with naturally occurring acute renal failure (ARF) and chronic renal failure (CRF). ANIMALS: 24 control dogs, 10 dogs with ARF, and 40 dogs with CRF. PROCEDURE: Serum concentrations of 1,25-(OH)2D3 were measured by use of a quantitative radioimmunoassay, and serum concentrations of 25-(OH)D3 were measured by use of a protein-binding assay. RESULTS: Mean +/- SD serum concentration of 1,25-(OH)2D3 was 153 +/- 50 pmol/L in control dogs, 75 +/- 25 pmol/L in dogs with ARF, and 93 +/- 67 pmol/L in dogs with CRF. The concentration of 1,25-(OH)2D3 did not differ significantly between dogs with ARF and those with CRF and was in the reference range in most dogs; however, the concentration was significantly lower in dogs with ARF or CRF, compared with the concentration in control dogs. Mean +/- SD concentration of 25-(OH)D3 was 267 +/- 97 nmol/L in control dogs, 130 +/- 82 nmol/L in dogs with ARF, and 84 +/- 60 nmol/L in dogs with CRF. The concentration of 25-(OH)D3 was significantly lower in dogs with ARF or CRF, compared with the concentration in control dogs. CONCLUSIONS AND CLINICAL RELEVANCE: The concentration of 1,25-(OH)2D3 was within the reference range in most dogs with renal failure. Increased serum concentrations of parathyroid hormone indicated a relative deficiency of 1,25-(OH)2D3. A decrease in the serum concentration of 25-(OH)D3 in dogs with CRF appeared to be attributable to reduced intake and increased urinary loss. 相似文献
6.
Reconciling 14C and minirhizotron‐based estimates of fine‐root turnover with survival functions 下载免费PDF全文
The turnover of fine‐roots is a crucial component for the input of C to the soil. The amount of root litter input is depending on estimates of turnover times from different techniques. Turnover times from fine‐root cameras (minirhizotrons) often yield 75% higher root litter input estimates than turnover times estimated with the bomb‐radiocarbon signature of fine roots. We introduce a generic framework for the analysis of fine‐root 14C with different survival functions. So far, mostly an exponential function has been used to estimate the turnover time and mean age of fine roots. In the context of the introduced survival function framework we clarify the terms turnover time, mean residence time, mean longevity, and mean age, which are commonly used in studies of root turnover. Using a unique time series of fine‐root 14C (Fröberg 2012), we test if survival functions other than the exponential function are better in accordance with turnover‐time estimates commonly found with other methods. A survival function that corresponds to a two‐pool model was best in agreement with minirhizotron‐based estimates (mean residence time of 1.9 y). We argue that using fine‐root 14C and minirhizotron time‐to‐death data together would give the best constraints on fine‐root turnover. At the same time this could allow quantifying systematic biases inherent to both techniques. 相似文献
7.
Bashar W. Shaheen Chengming Wang Calvin M. Johnson Bernhard Kaltenboeck Dawn M. Boothe 《Veterinary microbiology》2009,139(3-4):379-385
Fluoroquinolones are used to treat infections caused by Escherichia coli in canine and feline veterinary patients, particularly those infecting the urinary tract. The gyrA gene is a primary target causing fluoroquinolone resistance in Gram negative coliforms, with mutations in codons 83 and 87 generally associated with high-level of resistance E. coli clinical isolates. We have developed a fluorescence resonance energy transfer (FRET) quantitative PCR to identify enrofloxacin-resistance in clinical E. coli isolates that carry mutations in codons 83 and 87 of gyrA. This real-time quantitative PCR assay is rapid, economical, and sensitive compared with cultured antimicrobial susceptibility testing. The assay identified as few as four genome copies per reaction from culture and 19 genome copies in urine. For the 70 isolates tested, the sensitivity was 87.5% (95% CI = 75–95.3%) (n = 42/48), specificity was 100% (95% CI = 87.3–100%) (n = 22/22), whereas accuracy was 91.4% (95% CI = 82.3–97%) (n = 64/70). Furthermore, we were able to accurately differentiate between the wild type and mutants E. coli directly from infected canine urine samples (n = 5) within 2 h. These results were confirmed by sequence alignments of the PCR products and comparison with the susceptibility testing. The FRET-PCR assay appears to have promising clinical application as an early diagnostic tool for rapid and sensitive detection and differentiation of the level of fluoroquinolone resistance among clinical E. coli isolates that may facilitate design of the dosing regimen. 相似文献
8.
Journal of Plant Diseases and Protection - This study explores the food plant spectrum of the sugar beet weevil (Asproparthenis punctiventris Germar; Coleoptera: Curculionidae), one of the most... 相似文献
9.
Briviba K Stracke BA Rüfer CE Watzl B Weibel FP Bub A 《Journal of agricultural and food chemistry》2007,55(19):7716-7721
The present study was performed to compare the effects on antioxidant activity and on DNA damage of organic and conventionally produced apples grown under controlled conditions in human peripheral blood lymphocytes. Six healthy volunteers consumed either organically or conventionally grown apples (Golden Delicious, 1000 g) from two neighboring commercial farms in a double-blinded, randomized, cross-over study. The average content of total identified and quantified polyphenols in the organically and conventionally produced apples was 308 and 321 microg/g fresh weight, respectively. No statistically significant differences in the sum of phenolic compounds or in either of the polyphenol classes were found between the agricultural methods. Consumption of neither organically nor conventionally grown apples caused any changes in antioxidant capacity of low-density lipoproteins (lag time test), endogenous DNA strand breaks, Fpg protein-sensitive sites, or capacity to protect DNA against damage caused by hydrogen peroxide. However, a statistically significant decrease in the levels of endonuclease III sensitive sites and an increased capacity to protect DNA against damage induced by iron chloride were determined 24 h after consumption in both groups of either organic or conventionally grown apples, indicating the similar antigenotoxic potential of both organically and conventionally grown apples. 相似文献
10.