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   30篇
  免费   2篇
林业   1篇
  3篇
综合类   5篇
农作物   1篇
畜牧兽医   18篇
园艺   2篇
植物保护   2篇
  2023年   1篇
  2021年   1篇
  2017年   3篇
  2014年   1篇
  2013年   1篇
  2011年   2篇
  2010年   2篇
  2009年   2篇
  2008年   1篇
  2007年   2篇
  2006年   1篇
  2005年   1篇
  2004年   3篇
  2003年   2篇
  2001年   2篇
  2000年   4篇
  1999年   1篇
  1997年   1篇
  1996年   1篇
排序方式: 共有32条查询结果,搜索用时 17 毫秒
1.
Muro M 《Science (New York, N.Y.)》2000,290(5491):422b-423b
State transportation officials have agreed to weigh a proposal to set aside a scientifically valuable parcel of a federal highway project for future research rather than excavating it and selling it to the highest bidder. Should it proceed, Arizona could set a new standard of stewardship for government agencies that determine the fate of ancient relics.  相似文献   
2.
Muro M 《Science (New York, N.Y.)》2000,290(5499):2045-2046
Conservationists have long contended, largely in impressionistic terms, that 70 years of American dam building and water diversion have destroyed the biological richness of the Colorado River delta, a key nursery of marine life at the end of the Southwest's great watercourse. Now researchers have confirmed those suspicions, using an important ecological player--clams--as a quantitative marker.  相似文献   
3.
The aim of this study was to evaluate the reproductive performance of three parities of gilts treated or not treated with gonadotropin to induce puberty. Sixty gilts received 600 IU of equine chorionic gonadotropin (eCG) followed by 2.5 mg of porcine luteinizing hormone (LH) 72 h later. Fifty‐nine other gilts were exposed only to a mature boar for 15 min twice daily. Artificial insemination (AI) was performed at 0, 12 and 24 h after the detection of oestrus, and gestation was confirmed by ultrasound after 35 days. Sows were inseminated at the first post‐weaning oestrus. The total numbers of piglets born, piglets born alive, stillborn, mummified foetuses, as well as pregnancy and farrowing rates were evaluated for each of the three parities. Culling rates, farrowing intervals and weaning‐to‐oestrous intervals (WEI) were also analysed. Mean age at puberty and oestrous manifestation were not significantly different between treatments (p = 0.0639; 179.20 ± 17.52 compared with 173.96 ± 16.94, 91.66% compared with 94.92%) across the experimental period. However, females that underwent puberty induction showed modest increases both in the number of total pigs born and in the number of piglets born alive. In conclusion, puberty induction through exogenous gonadotropin administration in field conditions did not induce a more concentrated first oestrous manifestation, but trended to a modest increase in the number of pigs born alive in the first parity and a reduced culling rate during the first gestation.  相似文献   
4.
Organic growing media employed in hydroponic crops could change their characteristics due to organic matter degradation during culture growing season. Traditional methods for measuring the stability of growing media (Biochemical Stability Index, Lemaire) do not take into account the activity of crop roots, nutrients in the growing media or microorganism presence. Three experiments were performed to determine the stability of six organic substrates. Stability was measured as the percentage of organic matter remaining in substrates. In experiment one (short duration and small scale without plant) 500 ml samples were incubated for 180 days following original methodology proposed by Lemaire (L) and with three modifications: (1) Inoculation with compost (I), (2) watered with nutrient solution (NS), and (3) both combined (I + NS). In experiment two (Long duration, medium scale) 10 l samples were incubated with and without a lolium crop for 720 days in a greenhouse. In experiment 3 stability of each substrate was real measured in 20 l hydroponic bags after use in four cycles of tomato production in a commercial greenhouse (2 years). All incubations were triplicated. Physicochemical properties of substrates were measured. Correlations between stability estimated in experiment one and two and real determinations in experiment three were analyzed. Lemaire methodology modified by adding and inoculum an nutrients (I + NS) was the best method to estimate the stability of organic growing media measured in real conditions in experiment 3. This new method greatly improves the estimation performed with original Lemaire methodology. Long term incubations with lolium also reproduce well the real stability of growing media but this methodology is not feasible because it requires four times longer and the amount of substrate required is 20 times larger for each sample.  相似文献   
5.
Trichinellosis is a cosmopolitan zoonotic disease affecting a wide variety of animals, including man. Non-encapsulated and encapsulated species diverge with respect to their developmental strategies. Little is known at the molecular level about parasite-derived mediators responsible for host muscle cell transformation occurring during trichinellosis. In this context, host-parasite relationships in Trichinella-infected animals could be related to different host-immune and cell mediators, e.g. nitric oxide (NO). Here, we investigate the stimulatory/inhibitory role of L1 antigens from four encapsulated (T. spiralis, T. britovi, T. nelsoni and T. nativa) and one non-encapsulated (T. pseudospiralis) Trichinella species on NO production from rat macrophages in vitro. Our results demonstrate that encapsulated and non-encapsulated Trichinella species differ in their capacity to stimulate the secretion of NO from host macrophages. Biological significance of these differences should be further assessed in the available experimental models.  相似文献   
6.
To try new acrosomal probes for assessing ram spermatozoa, we compared the LysoSensor? probe, which labels acidic organelles, with the frequently used peanut agglutinin acrosomal probe (PNA‐PE; phycoerythrin as fluorescent moiety). The previous microscopic observations showed a lack of relationship of LysoSensor? with acrosomal status. Semen was obtained from five rams and frozen in four pools. Each pool was analysed carrying out a triple staining propidium ioide/PNA‐PE/LysoSensor? Green DND‐189 to test acrosome labelling, and a double staining SYBR‐14/PI, to assess sperm viability. Stained samples were analysed by flow cytometry. All measurements were replicated. Data were processed using agreement and repeatability tests. LysoSensor? labelling did not agree with PNA (mean of differences: 30.8%; coefficient of agreement: 22.6%), confirming microscopic observations. Nevertheless, when LysoSensor? was compared with SYBR‐14/PI, the agreement was high (mean of differences: ?0.05%; coefficient of agreement: 5.07%). Repeatability of both methods was high and similar. LysoSensor? did not seem to specifically stain the acrosome, but it may accumulate in the cytoplasm and label viable spermatozoa. Therefore, LysoSensor? might not be used as an acrosomal probe in ram spermatozoa, but it could be used in other kind of studies, taking advantage of its pH sensitivity.  相似文献   
7.
8.
Summary Two culture systems for propagating first generation potatoes were compared; the traditional system used a peat/sand mixture with mineral fertilizer, and hydroponic culture used perlite and nutrient solution. Total production and the number of tubers obtained using the hydroponic system were significantly higher than using the traditional culture system. Tuber yields from in vitro plants and minitubers depended upon time of year. During the autumn/winter cycle yield from minitubers was double that from in vitro plants, whereas the reverse was true during the spring/summer cycle. Four hydroponic test cultures were carried out to study the influence of seed density. The number of tubers obtained increased significantly with seed density but there was no decrease in the number of large-diameter tubers.  相似文献   
9.
In the present work, the species-specific identification of Taeniid spp. cysticerci and sarcocystis cysts isolated from infected pigs and cattle was achieved by PCR. In particular: (i) multiplex-PCR derived from HDP2 DNA fragment, specific for Taenia saginata/Taenia solium; (ii) PCRs and PCR-RFLPs of the rDNA internal transcribed spacers 1 and 2 (ITS1 and ITS2) for the differential diagnosis of taeniids; (iii) PCR derived from the 18S rRNA gene and sequencing, specific for Sarcoystis spp. The combined application of these three PCR protocols provided an unequivocally specific diagnosis of T. saginata, T. solium, T. hydatigena, Sarcocystis hominis and Sarcocystis suihominis, and may have practical application in the identification of calcified degenerating or morphologically dubious cysts, for example in the slaughter house situation or in human biopsy samples.  相似文献   
10.
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