首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   208篇
  免费   11篇
林业   14篇
农学   8篇
基础科学   3篇
  58篇
综合类   24篇
农作物   9篇
水产渔业   20篇
畜牧兽医   45篇
园艺   3篇
植物保护   35篇
  2024年   1篇
  2023年   5篇
  2022年   2篇
  2021年   6篇
  2020年   4篇
  2019年   10篇
  2018年   4篇
  2017年   4篇
  2016年   5篇
  2015年   5篇
  2014年   1篇
  2013年   6篇
  2012年   11篇
  2011年   20篇
  2010年   10篇
  2009年   9篇
  2008年   23篇
  2007年   16篇
  2006年   9篇
  2005年   16篇
  2004年   9篇
  2003年   15篇
  2002年   10篇
  2001年   1篇
  2000年   1篇
  1998年   2篇
  1996年   5篇
  1995年   1篇
  1994年   1篇
  1993年   1篇
  1992年   1篇
  1986年   1篇
  1984年   1篇
  1982年   1篇
  1955年   1篇
  1870年   1篇
排序方式: 共有219条查询结果,搜索用时 0 毫秒
81.
Wholegrain consumption is associated with several health benefits, in contrast to the consumption of refined grains. This can partly be related to the antioxidant compounds in the outer parts of the grain kernel. The bioaccessibility of these antioxidant compounds from the wholegrain matrix during gastrointestinal digestion is crucial for their absorption and bioavailability. In the current study, the bioaccessible compounds from aleurone, bran and flour were obtained from a dynamic in vitro model of the upper gastrointestinal tract. They were collected at 1 h time intervals to assess their antioxidant capacity (TEAC assay) and also their anti-inflammatory effect (TNF-α reduction in U937 macrophages stimulated with LPS). The bioaccessible compounds from aleurone had the highest antioxidant capacity and provided a prolonged anti-inflammatory effect, shown by the TNF-α reduction of a relatively late time-interval (3–4 h after start of digestion). The contribution of ferulic acid to those effects was minor due to its low bioaccessibility. Aleurone seems a promising wheat fraction for cereal products with a healthy added value.  相似文献   
82.
Quantitative information about the amount and stability of organic carbon (OC) in different soil organic‐matter (OM) fractions and in specific organic compounds and compound‐classes is needed to improve our understanding of organic‐matter sequestration in soils. In the present paper, we summarize and integrate results performed on two different arable soils with continuous maize cropping (a) Stagnic Luvisol with maize cropping for 24 y, b) Luvic Phaeozem with maize cropping for 39 y) to identify (1) the storage of OC in different soil organic‐matter fractions, (2) the function of these fractions with respect to soil‐OC stabilization, (3) the importance and partitioning of fossil‐C deposits, and (4) the rates of soil‐OC stabilization as assessed by compound‐specific isotope analyses. The fractionation procedures included particle‐size fractionation, density fractionation, aggregate fractionation, acid hydrolysis, different oxidation procedures, isolation of extractable lipids and phospholipid fatty acids, pyrolysis, and the determination of black C. Stability of OC was determined by 13C and 14C analyses. The main inputs of OC were plant litter (both sites) and deposition of fossil C likely from coal combustion and lignite dust (only Phaeozem).  相似文献   
83.
This research project examined the potential hazards of a major class of insect growth regulators (IGRs) to survival, reproduction and larval growth in bumblebees Bombus terrestris L. Eight chitin synthesis inhibitors (CSIs) were tested: buprofezin, cyromazine, diflubenzuron, flucycloxuron, flufenoxuron, lufenuron, novaluron and teflubenzuron. These different IGRs, which are important in the control of pest insects in greenhouses, were applied via three different routes of exposure under laboratory conditions: dermal contact, and orally via the drinking of sugar/water and via pollen. The compounds were tested at their respective maximum field recommended concentrations (MFRC) and also in dose-response assays to calculate LC(50) values. In general, none of the CSIs showed acute worker toxicity. However, there was a dramatic reduction in brood production, especially after oral treatment with pollen and sugar/water. Conspicuously, egg fertility was reduced in all treatments with diflubenzuron and teflubenzuron. In addition to egg mortality, the worker bumblebees removed larvae from the treated nest, and in most cases these individuals were dead first-second instars. Under a binocular microscope, such larvae showed an abnormally formed cuticle leading to mechanical weakness and death. In another series of experiments using (14)C-diflubenzuron and (14)C-flufenoxuron, cuticular penetration in workers was studied for a better understanding of the differences in toxicity. With (14)C-diflubenzuron, transovarial transport and accumulation in the deposited eggs supported the strong reproductive effects. Overall, the present results suggest that CSIs should be applied with caution in combination with bumblebees. The compatibility of each compound to be used in combination with B. terrestris is discussed in relation to calculated LC(50) values, routes of uptake and effects.  相似文献   
84.
Objective— To evaluate outcome after transanal rectal pull-through amputation of single colorectal adenocarcinoma and in situ carcinoma (T is ) in dogs.
Study Design— Retrospective case series.
Animals— Dogs (n=11) with colorectal cancer.
Methods— Full-thickness colorectal amputation by either simple transanal (7 dogs) or combined abdominal–transanal (4) pull-through technique.
Results— Adenocarcinoma (8) and T is (2) were removed with 3–6 cm of grossly normal tissue, cranial and caudal to the tumor, or in 1 T is with 2 cm grossly normal tissue, cranial and caudal. Two dogs that had a combined abdominal–transanal approach died within 4 days. In the other dogs, postoperative complications included short-term tenesmus (6 dogs), rectal bleeding (11), rectal stricture (3), and long-term fecal incontinence (1). Postoperative recurrence and metastatic rates for adenocarcinoma were 18.2% and 0%, respectively. Median disease-free interval and survival time were not reached. Mean disease-free and overall survival times were 44.3 and 44.6 months (range, 0–75 months), respectively.
Conclusion— En bloc excision of colorectal T is and adenocarcinoma may be followed by a long survival. Complications of the transanal approach are usually moderate and self-limiting, but complications are more common and severe when more extensive resections are performed through a combined abdominal–transanal approach.
Clinical Relevance— Transanal rectal pull-through amputation is suitable for en bloc resection of colorectal neoplasia. A combined abdominal–transanal approach should be reserved for tumors extending from the mid-cranial region of the rectum to the descending colon.  相似文献   
85.
The toxicity of olive mill wastewaters (OMW) is commonly attributed to monomeric phenols. OMW were treated in an aerated, stirred reactor containing agricultural soil, where the oxidative polymerization of phenols took place. In 24 h, OMW monomeric phenols decreased by >90%. This resulted in a corresponding reduction in phytotoxicity, as measured by germination tests with tomato and English cress seeds, and in microbial toxicity, as measured by lag phase duration in Bacillus cereus batch growth. Soil germination capability after irrigation with OMW was assessed in long-term pot experiments. The relative germination percentage of tomato was higher when the soil was irrigated with treated OMW rather than with untreated ones, although it was lower than the control (e.g., soil irrigated with distilled water). At longer incubation times, a complete recovery of the soil germination capability was achieved with treated, but not with untreated, OMW.  相似文献   
86.
Essential oils from three species of Chrysanthemum growing in Tunisia (C. coronarium, C. fuscatum, and C. grandiflorum) were first analyzed by gas chromatography (GC) and GC/mass spectrometry (MS) and then evaluated for toxicity and antifeeding action against Tribolium confusum. The essential oils obtained from leaves and flowers shared a similar qualitative composition, but the relative proportions of the constituents were quite different. The essential oil of C. grandiflorum was rich in sesquiterpenoids, while those of C. fuscatum and C. coronarium were rich in monoterpenoids. The main common constituents of all the essential oils were ??-pinene, myrcene, ??-humulene, ??-caryophylene, spathulenol, and caryophyllene oxide. The most effective essential oil was obtained from the leaves of C. grandiflorum, that inhibited the relative growth rate (?0.03?mg/mg/d), efficiency of conversion of ingested food (?50.69%), relative consumption rate, caused an antifeeding effect (66.43%) and a high mortality (80%) of T. confusum larvae. Topical application C. grandiflorum essential oil caused a significant insect mortality that attends 27% after 7?days of treatment. While essential oil from C. coronarium flowers has contact and fumigant toxicity with a mortality of 9 and 13%, respectively. Results analysis highlights a relationship between essential oils composition and insecticidal activity against T. confusum. The study showed that each essential oil has specific chemical composition and act differently according to the nature of attributed test. The use of essential oils from different Chrysanthemum species with different methods helps poor farmers who store small amounts of grains to preserve it against pest infestation.  相似文献   
87.
88.
1,2-O-dilauryl-rac-glycero glutaric acid-(6′-methylresorufin) ester (DGGR) lipase activity has been proposed as a faster and less expensive test used in the diagnosis of acute pancreatitis (AP) compared to canine pancreatic lipase immunoreactivity (cPLI), which is considered the most sensitive and specific serum test available for dogs. Elevations in lipase activity have been observed in dogs with naturally occurring hypercortisolism (HC) and in those treated with exogenous steroids, which complicates the diagnosis of AP in dogs with HC. We compared lipase activity measured by DGGR and 1,2-diglyceride (1,2-DiG) assays in 22 dogs with HC, 22 with AP, and 22 healthy dogs. The dogs with HC had no clinical signs or ultrasonographic findings consistent with AP. DGGR lipase activity was elevated in 64% and 73% of the dogs with HC and AP, respectively, and in 18% of healthy dogs. 1,2-DiG lipase activity was high in 23% and 36% of the dogs with HC and AP, respectively, and in 5% of the healthy dogs. Both DGGR and 1,2-DiG lipase activities were significantly different between the healthy dogs and the other 2 groups, whereas no differences were detected between the dogs with HC and those with AP. Our results support a lack of specificity for both DGGR and 1,2-DiG lipase activity assays in aiding the diagnosis of AP in dogs with HC.  相似文献   
89.
In the present study, the antioxidant profile of olive oil antioxidants was investigated. Hydroxytyrosol and oleuropein are potent scavengers of hydroxyl radicals (OH*), peroxynitrite (ONOOH), and superoxide radicals (O(2)*(-)). Homovanillic alcohol, one of the main metabolites of hydroxytyrosol, and tyrosol are less potent scavengers of these reactive species. None of the olive oil antioxidants are good hypochlorous acid (HOCl) or hydrogen peroxide (H(2)O(2)) scavengers. Hydroxytyrosol efficiently protects against LDL oxidation in vitro and in vivo. However, no protective effect of hydroxytyrosol is usually demonstrated ex vivo against the oxidation of LDL isolated from humans after hydroxytyrosol consumption. The present study shows that this controversy is due to the isolation of LDL, which greatly reduces the protective effect of hydroxytyrosol against LDL oxidation. Hydroxytyrosol is an efficient scavenger of several free radicals. The physiological relevance of the high intrinsic antioxidant activity of hydroxytyrosol is illustrated by its protection against LDL oxidation.  相似文献   
90.
Many species of African nonhuman primates are naturally infected with simian immunodeficiency viruses (SIVs) in the wild and in captivity. In contrast to HIV-infected humans, these natural SIV hosts typically do not develop AIDS, despite chronic infection with a highly replicating virus. In this Review, we discuss the most recent advances on the mechanisms of protection from disease progression in natural SIV hosts, with emphasis on how they differ from pathogenic HIV/SIV infections of humans and rhesus macaques. These mechanisms include: (i) resolution of immune activation after acute infection, (ii) restricted pattern of target cell infection, and (iii) protection from mother-to-infant transmission. We highlight the areas that should be pursued in future studies, focusing on potential applications for the treatment and prevention of HIV infection.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号