全文获取类型
收费全文 | 130篇 |
免费 | 4篇 |
国内免费 | 2篇 |
出版年
2022年 | 3篇 |
2020年 | 3篇 |
2019年 | 5篇 |
2018年 | 3篇 |
2017年 | 1篇 |
2016年 | 2篇 |
2015年 | 2篇 |
2014年 | 4篇 |
2013年 | 2篇 |
2012年 | 3篇 |
2011年 | 6篇 |
2010年 | 4篇 |
2009年 | 3篇 |
2008年 | 2篇 |
2007年 | 7篇 |
2006年 | 1篇 |
2004年 | 1篇 |
2003年 | 1篇 |
2001年 | 2篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 9篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 14篇 |
1976年 | 5篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 3篇 |
排序方式: 共有136条查询结果,搜索用时 15 毫秒
51.
The sites of glycosylation of zeins, the maize (Zea mays L.) storage proteins, were studied using the affinity of the lectin Concanavalin A (Con A) for certain glycosides. Zeins which were extracted from kernels of Illinois High Protein (IHP), W22, W64A and Oh43 were separated by isoelectric focusing and analyzed with a radiolabeled Con A binding technique. Certain sub-groups of the zein proteins contained carbohydrate moities which bound Con A while others did not. Zeins extracted from Oh43 kernels had a higher relative affinity for Con A than those of other maize lines. Further analyses of the zeins of Oh43 by gas chromatography demonstrated the presence of fucose, mannose and glucose. 相似文献
52.
Shashank Gaur Theresa B. Kuhlenschmidt Mark S. Kuhlenschmidt Juan E. Andrade 《Parasitology international》2018,67(2):170-175
Cryptosporidium parvum is the second leading cause of persistent diarrhea among children in low-resource settings. This study examined the effect of oregano essential oil (OEO) and carvacrol (CV) on inhibition of C. parvum infectivity in vitro. HCT-8 cells were seeded (1 × 106) in 96-well microtiter plates until confluency. Cell viability and infectivity were assessed by seeding HCT-8 cell monolayers with C. parvum oocysts (1 × 104) in two modalities: 1) 4 h co-culture with bioactive (0–250 μg/mL) followed by washing and incubation (48 h, 37 °C, 5% CO2) in bioactive-free media; and 2) 4 h co-culture of C. parvum oocysts followed by washing and treatment with bioactive (0–250 μg/mL) during 48-h incubation. Cell viability was tested using Live/Dead? assay whereas infectivity was measured using C. parvum-specific antibody staining via immunofluorescence detection. Loss of cell viability was observed starting at 125 μg/mL and 60 μg/mL for OEO and CV, respectively. Neither OEO nor CV modulated the invasion of C. parvum sporozoites in HCT-8 cells. Treatment with bioactive after invasion reduced relative C. parvum infectivity in a dose-dependent manner to 55.6 ± 10.4% and 45.8 ± 4.1% at 60 and 30 μg/mL of OEO and CV, respectively. OEO and CV are potential bioactives to counteract C. parvum infection in children. 相似文献
53.
The effect of beta-endorphin on natural cytotoxicity and antibody dependent cellular cytotoxicity 总被引:2,自引:0,他引:2
The ability of the central nervous system to modulate immune responsiveness has received increasing attention. A potential mechanism that would allow the central nervous system to alter the immune system is the release of neuroendocrine and neurotransmitter polypeptides into the peripheral circulation with subsequent modulation of immunocyte function. In this report, we demonstrate that the neuropeptide, beta-[D-ALA2]-endorphin augments natural cytotoxicity but does not effect antibody-dependent cellular cytotoxicity. The observations are discussed in relation to the mechanisms for natural cytotoxicity and antibody dependent cellular cytotoxicity. 相似文献
54.
Supply of cellulosic biomass in Illinois and implications for the Conservation Reserve Program 下载免费PDF全文
We developed a mathematical programming model to estimate the supply of cellulosic biomass in Illinois at various biomass prices and examine the implications of biomass production for the maintenance costs of the Conservation Reserve Program (CRP). We find that Illinois has the potential to produce about 38.4–54.5 million dry metric tons (MT) of biomass in 2020 at a biomass price of $150/MT, depending on the production costs of cellulosic feedstocks, residue collection technology, and rates of yield increases of conventional crops. Corn stover will account for more than 65% of the total biomass production across biomass prices and the scenarios considered, while the roles of wheat straw and energy crops are quite limited. Given biomass prices of $50/MT‐$150/MT, many landowners would convert their expiring CRP lands to croplands. To maintain the size of the CRP during the 2007–2020 period at the 2007 levels in Illinois, total program maintenance costs would be $104.6–176.5 million at a biomass price of $50/MT, depending on biomass production conditions and crop yields on CRP lands. This would increase to $155.2–245.4 million at a biomass price of $150/MT. 相似文献
55.
BENJAMIN J. O'NEAL EDWARD J. HESKE JOSHUA D. STAFFORD 《The Journal of wildlife management》2008,72(3):654-664
Abstract: Conservation programs that facilitate restoration of natural areas on private land are one of the best strategies for recovery of valuable wetland acreage in critical ecoregions of the United States. Wetlands enrolled in the Conservation Reserve Enhancement Program (CREP) provide many ecological functions but may be particularly important as habitat for migrant and resident waterbirds; however, use of, and factors associated with use of, CREP wetlands as stopover and breeding sites have not been evaluated. We surveyed a random sample of CREP wetlands in the Illinois River watershed in 2004 and 2005 to quantify use of restored wetlands by spring migrating and breeding waterbirds. Waterbirds used 75% of wetlands during spring migration. Total use-day abundance for the entire spring migration ranged from 0 to 49,633 per wetland and averaged 6,437 ± 1,887 (SE). Semipermanent wetlands supported the greatest total number of use-days and the greatest number of use-days relative to wetland area. Species richness ranged from 0 to 42 (x̄ = 10.0 ± 1.5 [SE]), and 5 of these species were classified as endangered in Illinois. Density of waterfowl breeding pairs ranged from 0.0 pairs/ha to 16.6 pairs/ha (x̄ = 1.9 ± 0.5 [SE] pairs/ha), and 16 species of wetland birds were identified as local breeders. Density of waterfowl broods ranged from 0.0 broods/ha to 3.6 broods/ha and averaged 0.5 ± 0.1 (SE) broods/ha. We also modeled spring stopover use, waterbird species richness, and waterfowl reproduction in relation to spatial, physical, and floristic characteristics of CREP wetlands. The best approximating models to explain variation in all 3 dependent variables included only the covariate accounting for level of hydrologic management (i.e., none, passive, or active). Active management was associated with 858% greater use-days during spring than sites with only passive water management. Sites where hydrology was passively managed also averaged 402% greater species richness than sites where no hydrologic management was possible. Density of waterfowl broods was 120% greater on passively managed sites than on sites without water management but was 29% less on sites with active compared to passive hydrologic management. Densities of waterfowl broods also were greatest when ratios of open water to cover were 70:30. Models that accounted for vegetation quality and landscape variables ranked lower than models based solely on hydrologic management or vegetation cover in all candidate sets. Although placement and clustering of sites may be critical for maintaining populations of some wetland bird species, these factors appeared to be less important for attracting migrant waterbirds in our study area. In the context of restored CREP wetlands, we suggest the greatest gains in waterbird use and reproduction may be accomplished by emphasizing site-specific restoration efforts related to hydrology and floristic structure. (JOURNAL OF WILDLIFE MANAGEMENT 72(3):654–664; 2008) 相似文献
56.
Allelic allotype inclusion and exclusion among rabbit Ig-bearing lymphocytes of peripheral blood and lymphoid organs 总被引:1,自引:0,他引:1
Mononuclear cells isolated from peripheral blood, appendix, sacculus rotundus, mesenteric lymph nodes, and spleen of b4b5 heterozygous rabbits were examined for surface Ig allotypes of the b locus. Ig allotype-bearing cells were detected as cells binding erythrocytes or bacteria coated with monospecific anti-b4 or anti-b5 antibody (Ab). Rosetting the cells with Ab-coated erythrocytes indicated that many peripheral blood lymphocytes, but relatively few appendix cells, bore both the b4 and b5 allotypes. Lymphocytes bearing both the b4 and b5 allotypes were also detected by incubating the cells with a mixture of Escherichia coli coated with anti-b4 Ab and Gaffkya tetragena coated with anti-b5 Ab. The percentage of Ig-positive lymphocytes binding both bacteria was 22–31% in the peripheral blood, 4–6% in the appendix, 3–5% in the sacculus rotundus, 4–10% in the mesenteric lymph nodes, and 5% in the spleen. Thus, the percentage of double-bearing lymphocytes was higher in the blood than in the appendix, sacculus rotundus, mesenteric lymph nodes, or spleen. The b4b5-bearing cells in the blood were not cells with adsorbed cytophilic Ab, since these cells still bore both the b4 and b5 allotypes after pronase digestion and Ig regeneration. These double-bearing lymphocytes, i.e., cells exhibiting allelic allotype inclusion, are probably less differentiated cells. 相似文献
57.
58.
Complex organization of zein genes in maize 总被引:1,自引:0,他引:1
We have examined the fragments of maize nuclear DNA that are homologous to three cloned cDNAs prepared from zein mRNA. Southern blots of high molecular weight ( > 40 kb) maize nuclear DNA cleaved with BamHI, HindIII or EcoRI were hybridized to three zein cDNA plasmid probes. Multiple restriction fragments in a wide range of size classes were observed to hybridize with all three probes. Our results indicate the occurrence of families of genes in the maize genome that are related by their sequences to a given zein mRNA sequence. 相似文献
59.
60.
Andrew D. Gilbert Christopher N. Jacques Joseph D. Lancaster Aaron P. Yetter Heath M. Hagy 《The Journal of wildlife management》2020,84(6):1063-1071
Aerial surveys flown at low altitudes allow detection, identification, and enumeration of waterfowl and other waterbirds, but few studies have assessed disturbance to these guilds during the nonbreeding period. Excessive disturbance can potentially increase energy expenditure and exposure to hunting mortality contrary to objectives of many waterfowl sanctuaries where surveys are conducted. We used concurrent ground and aerial surveys to estimate the proportion of waterfowl and other waterbirds that exhibited a noticeable reaction (i.e., disturbance) or left the survey area entirely (i.e., abandonment) during low-altitude (i.e., 60–90 m above ground level) aerial surveys during September through January 2014–2017 in Illinois, USA. Overall, disturbance and abandonment probabilities of waterfowl (x̄ = 14 ± 2% [SE] and x̄ = 3 ± 1%, respectively) during aerial surveys were low. However, disturbance and abandonment probabilities varied considerably among taxa (e.g., American coot [Fulica americana] x̄ = 2 ± 1% and x̄ = 0 ± 0%, respectively; killdeer [Charadrius vociferus] x̄ = 92 ± 8% and x̄ = 17 ± 17%, respectively). Additionally, disturbance and abandonment probabilities of light geese (i.e., snow goose [Chen caerulescens] and Ross's goose [C. rossii]) and greater white-fronted geese (Anser albifrons) were relatively high, and nearly all light geese abandoned a survey location as a result of the aerial survey. Among waterfowl taxa, the odds of disturbance from the survey aircraft were 2.2–6.2 times greater at locations closed to waterfowl hunting than locations open to waterfowl hunting. Temperature, wind speed, and cloud cover were not important predictors of disturbance for most guilds, except for a negative influence of temperature on disturbance of geese. Low-altitude aerial surveys were not a significant source of disturbance for many taxa and abandonment events were rare, except events involving light geese. Periodic low-altitude aerial surveys appear to be compatible with objectives of providing sanctuary conditions for most waterfowl and other waterbirds. © 2020 The Wildlife Society. 相似文献