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   344篇
  免费   10篇
林业   38篇
农学   10篇
  62篇
综合类   13篇
农作物   8篇
水产渔业   20篇
畜牧兽医   180篇
园艺   5篇
植物保护   18篇
  2022年   6篇
  2021年   20篇
  2020年   7篇
  2019年   8篇
  2018年   9篇
  2017年   4篇
  2016年   8篇
  2015年   22篇
  2014年   19篇
  2013年   28篇
  2012年   29篇
  2011年   31篇
  2010年   14篇
  2009年   8篇
  2008年   21篇
  2007年   24篇
  2006年   23篇
  2005年   15篇
  2004年   16篇
  2003年   14篇
  2002年   10篇
  2001年   11篇
  2000年   1篇
  1999年   1篇
  1989年   2篇
  1988年   1篇
  1971年   1篇
  1968年   1篇
排序方式: 共有354条查询结果,搜索用时 31 毫秒
131.
Sea urchin petalloid coelomocytes effectuate the clotting pathway by undergoing a rapid and dynamic cellular transformation that leads to cellular adhesion and wounds closure. We have identified high levels of activity of arylsulfatase (Ars) associated with coelomocytes of the sea urchin Lytechinus variegatus (Lamarck, 1816). Ars activity was extracted from clotted coelomocytes with EDTA and showed high levels of activity up to a 1:100 dilution. Clot formation from isolated coelomic fluid was significantly inhibited by the ARS inhibitor, p-nitrophenyl phosphate. Ars activity was collected by 80% ethanol precipitation, a diagnostic test previously used in Ars isolation. Cellular extraction studies in the presence and absence of the non-ionic detergent Triton X-100 indicated that some Ars activity was present intracellularly, possibly in intracellular membrane-bound compartments, however the majority of Ars activity was extracted from the extracellular coelomocyte membrane. Polyclonal anti-sea urchin embryo Ars antibodies recognized a single protein band with an approximate molecular weight of 75 kDa on western blots. Immunofluorescence using the anti-sea urchin Ars antibody revealed an intracellular and extracellular staining of Ars in both petalloid and filopodial coelomocytes. Taken together, these data indicate that coelomocyte Ars might be involved in cell-to-cell crosslinking of surface sulfated polysaccharides vital for clot formation.  相似文献   
132.
The reaction products of an alkaline treatment of non-phenolic β-O-4-type lignin model compounds (C6–C2-type) consisting of p-hydroxyphenyl (H), guaiacyl (G), and/or syringyl (S) nuclei were identified and quantified. This was performed to examine how the type of H, G, or S nucleus affect the reaction product profiles. The major identified and quantified reaction products were phenol derivatives that were liberated from the aryl sides of the β-O-4 ether bonds of the lignin model compounds. Other products included derivatives of phenylethane-1,2-diol (glycol-type), benzaldehyde, and acetophenone, which originated from the alkyl sides of the β-O-4 ether bonds of the lignin model compounds. Although the type of aromatic nucleus of the aryl side of the β-O-4 ether bond of the lignin model compounds did not significantly affect the profile of the reaction products, the type of the alkyl side nucleus was influential. The glycol-type compound was the exclusive major reaction product when the S nucleus was on the alkyl side of the β-O-4 ether bond. On the other hand, when the H or G nucleus was present, a benzaldehyde derivative was the other major reaction product.  相似文献   
133.
We investigated the effect of exposure to low salinity water on plasma ion regulation and survival rates in artificially wounded devil stinger Inimicus japonicus. All fishes survived in 33% seawater (SW), while survival rate in 100% SW was 5.1% at 24 h. In 100% SW, plasma Na+, K+, Mg2+, and Ca2+ concentrations significantly increased to 238?±?49.9, 9.6?±?2.4, 15.1?±?3.5 and 5.0?±?0.7 mmol/l at 6 h, respectively; the gill Na+/K+–ATPase (NKA) activity was almost stable, although only one fish survived to 24 h. In 33% SW, plasma Na+ and K+ concentrations remained at the same level, and plasma Mg2+ and Ca2+ concentrations gradually increased to 16.2?±?0.7 and 4.5?±?0.2 mmol/l until 24 h, respectively. The NKA activity significantly increased to 5.1?±?1.1 µmol ADP/mg protein per h at 6 h. A positive correlation was observed between the wound surface area against body weight and the plasma ion concentrations, although no difference was observed in the restoration rate of the wounded area between 100 and 33% SW. These results indicate that exposure of wounded fish to low salinity water improves survivability by favoring plasma ion regulation without influencing the restoration rate.  相似文献   
134.
135.
The aim of the present study was to optimise the culture conditions for the in vitro production of bovine embryos. The development of in vitro fertilised bovine oocytes in CR1aa supplemented with 5% calf serum and IVD101 culture media were compared using traditional microdrops and Well of the Well (WOW) culture systems either under 5% or 20% oxygen tension. After 7 days of culture, a significantly higher blastocyst formation rate was obtained for embryos cultured in CR1aa medium compared to those cultured in IVD101, irrespective of O2 tensions and culture systems. The blastocyst formation in IVD101 was suppressed under 20% O2 compared to 5% O2 . Despite their similar total cell numbers, higher rates of inner cell mass (ICM) cells were observed in blastocysts developed in IVD101 medium than in those developed in CR1aa, irrespective of O2 tensions. There was no significant difference in blastocyst formation, total, ICM and trophectoderm (TE) cell numbers between embryos obtained by microdrop and WOW culture systems irrespective of the culture media and O2 tensions used. In conclusion, CR1aa resulted in higher blastocyst formation rates irrespective of O2 tension, whereas IVD101 supported blastocyst formation only under low O2 levels but enhanced the proliferation of ICM cells.  相似文献   
136.
Recently, we have identified novel saponins from edible seeds of Japanese horse chestnut ( Aesculus turbinata BLUME) after processing the natural seeds with wood ashes to remove bitterness. We attempted to determine anti-obesity effects of those saponins from edible seeds as well as natural seeds. The purified individual components of saponins from natural and edible seeds inhibited pancreatic lipase in vitro. The potency was in the order of escins > desacylescins > deacetylescins. Escins Ib and IIb as well as deacetylescins Ib and IIb with the angeloyl moiety were more potent than the corresponding Ia and IIa series with the tigloyl moiety. Moreover, in vivo anti-obesity effects of the saponin fractions were monitored for 8 weeks in mice fed high-fat diets. Saponin fractions from both seeds significantly attenuated the elevation in body weight, the mass of peritoneal adipose tissues, and plasma triacylglycerol, which was accompanied by higher contents of undigested fats in feces without changes in food intake, indicating the effective inhibition of fat digestion in vivo. Taken together, saponin fractions including desacylescins and deacetylescins from edible seeds are potentially useful for the development of nutraceutical foods with anti-obesity effects and more attenuated bitter taste.  相似文献   
137.
Formosa landlocked salmon (Oncorhynchus masou formosanus), an endemic, critically endangered subspecies of Cherry salmon (Oncorhynchus masou) complex, is only found in Taiwan. Because the eyed eggs and ungutted carcasses of Pacific salmons (genus Oncorhynchus) are imported for aquaculture and food to Taiwan from overseas every year, the requirement for preventing illegal trade or accidental commercial imports to avoid unwanted fish from contaminating the gene pool of Formosa landlocked salmon and infect them with diseases is critical for the conservation of Formosa landlocked salmon. Traditional morphology‐based species identification is impossible for salmon eggs and larvae that lack clearly defined morphological features. In the present study, the genetic differences among four subspecies (Oncorhynchus masou ishikawae, O. masou subsp., Oncorhynchus masou masou and O. masou formosanus) of Cherry salmon complex were determined from microsatellite DNA and amplified fragment length polymorphism analyses. We successfully generated a genetic marker to aid traditional taxonomy and investigate the integrity of the current taxonomic status among members of Cherry salmon complex. Use of molecular markers, in combination with traditional morphological identification, is a promising tool for identifying four closely related subspecies of Cherry salmon complex.  相似文献   
138.
We developed new F1 hybrids of Chinese cabbage (Brassica rapa L. ssp. pekinensis) that allow cultivation earlier in spring without heating by introducing extremely late-bolting alleles at two homologs of the flowering repressor Flowering Locus C (BrFLC2 and BrFLC3) from non-heading ‘Leafy Green Parental Line No. 2’. These new F1 hybrids were produced by the following four steps. First, the extremely late bolting selected lines were developed. These selected lines headed in spring after overwintering cultivation, whereas the conventional F1 cultivars flowered. Secondly, an investigation of the three plantings showed that our F1 hybrids formed heads when seeds were sown from mid-February to early March, whereas the conventional F1 cultivar did not form heads because of premature bolting. Thirdly, we identified some F1 hybrids with extremely late bolting during early spring cultivation in an investigation of many F1 hybrids. Finally, based on an investigation across four cold regions for 2 years, we compared the commercialization rate, defined as the proportion of plants greater than 2000 g in weight and with a flowering stalk less than 10 cm long. Then we identified a F1 of MS02 × 12-04 which had a high commercialization rate on average (92%), whereas the rates of three conventional F1 cultivars were only 0–2%. In the near future, these F1 hybrids will be valuable late-bolting cultivars despite climate change, permitting stable cultivation and harvest over wide regions.  相似文献   
139.
Isoflavones (IFs), found in the form of both aglycones and glucosides in soybean foods, induce weak estrogenic activities. Although IFs have a number of health benefits, it was previously reported that IFs cause nephrocalcinosis (NC) in the kidney of male Fischer 344 (F344) rats. The present study aims to elucidate the safety of IFs by focusing on IF-induced NC formation in rats. Fermented soybean extract (FSE) containing 420 mg/g isoflavone aglycones was orally administered to male F344 and Sprague-Dawley (SD) rats for 28 days. FSE induced NC formation in the kidney of F344 rats, but not in SD rats. However, absorption of IFs did not differ between F344 and SD rats. NC formation and its severity of FSE were histologically compared with those of soybean extract (SE) containing 518 mg/g isoflavone glucosides in F344 rats. There were no differences in the number of NC formations and the extent of calcium deposit between FSE and SE groups. To examine the dose effect of FSE on NC formation, doses of 20, 140, or 1000 mg/kg FSE were administered to F344 rats for 90 days. NC formation was observed in the 140 and 1000 mg/kg groups. These results indicated that a high dose of oral administration of IFs induced NC formation depending on the strain of rat.  相似文献   
140.
We studied microbe-plant interactions of white lupin, a cluster root-forming plant, under low P and N conditions to examine increased nutrient acquisition by plants either by a shift to a more specialized microbial community or changes in microbial enzyme production. White lupin plants were grown in rhizoboxes filled with either P- or N-deficient soil; fertilized soil was used as control. After cultivation of plants in a glasshouse for 41 d, plant growth (shoot and roots) and P and N accumulation in shoots were measured. Microbial functions were analyzed by P- and N-cycling enzymes. The microbial community structure was estimated by fingerprinting (denaturing gradient gel electrophoresis) and sequencing techniques. P deficiency induced the released citrate and acid phosphomonoesterases from cluster roots and stimulated the production of microbe-derived alkaline phosphomonoesterase in the rhizosphere. P deficiency decreased microbial diversity in the cluster root rhizosphere. Increased relative abundance of Burkholderiales in the rhizosphere of P deficient plants might be responsible for the degradation of different organic P fractions such as phytates. N deficiency induced an increase of the number of nodules and P concentration in shoot as well as roots of white lupin. We clarified that high release of citrate from cluster roots might be the preferred mechanisms to meet the P demand of nodulated plants under N deficiency. In addition, the high abundance of Rhizobiales and Rhodospirillales in the rhizosphere of cluster roots showed that the importance of N-fixing microorganisms under N deficiency. The contribution of rhizosphere microorganisms due to similar activities of N-cycling enzymes under the two different N treatments is less important for N nutrition of plants. Further understanding of the regulation of cluster roots under N-deficiency will provide new information on the interactions between P and N nutrition.  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