全文获取类型
收费全文 | 714篇 |
免费 | 84篇 |
专业分类
林业 | 29篇 |
农学 | 7篇 |
基础科学 | 6篇 |
51篇 | |
综合类 | 204篇 |
农作物 | 28篇 |
水产渔业 | 76篇 |
畜牧兽医 | 338篇 |
园艺 | 16篇 |
植物保护 | 43篇 |
出版年
2023年 | 5篇 |
2022年 | 3篇 |
2021年 | 8篇 |
2020年 | 9篇 |
2019年 | 15篇 |
2018年 | 15篇 |
2017年 | 15篇 |
2016年 | 7篇 |
2015年 | 14篇 |
2014年 | 27篇 |
2013年 | 21篇 |
2012年 | 68篇 |
2011年 | 77篇 |
2010年 | 26篇 |
2009年 | 21篇 |
2008年 | 58篇 |
2007年 | 49篇 |
2006年 | 61篇 |
2005年 | 63篇 |
2004年 | 35篇 |
2003年 | 39篇 |
2002年 | 47篇 |
2001年 | 14篇 |
2000年 | 13篇 |
1999年 | 6篇 |
1998年 | 6篇 |
1997年 | 4篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1970年 | 1篇 |
1969年 | 3篇 |
1968年 | 4篇 |
1928年 | 1篇 |
1916年 | 1篇 |
排序方式: 共有798条查询结果,搜索用时 15 毫秒
81.
Ruiz-Matute AI Brokl M Sanz ML Soria AC Côté GL Collins ME Rastall RA 《Journal of agricultural and food chemistry》2011,59(8):3693-3700
The selective fermentation by human gut bacteria of gluco-oligosaccharides obtained from the reaction between the glucosyl group of sucrose and cellobiose, catalyzed by dextransucrases (DSR) from Leuconostoc mesenteroides , has been evaluated. Oligosaccharides were fractionated according to their molecular weight, and their effect on the growth of different bacterial groups was studied. To determine the structure (position and configuration of glycosidic linkages)-function relationship, their properties were compared to those of DSR maltose acceptor products (DSRMal) and of recognized prebiotic carbohydrates (fructo-oligosaccharides, FOS). Cellobiose acceptor products (DSRCel) showed bifidogenic properties similar to those of FOS. However, no significant differences related to molecular weight or isomeric configurations were found for DSRCel and DSRMal products. 相似文献
82.
83.
Evaluating simultaneous impacts of three anthropogenic effects on a floodplain-dwelling marsupial Antechinus flavipes 总被引:1,自引:0,他引:1
Regulation of river flows has altered floodplain ecosystems around the world. Floods are less frequent, which leads to reduction of favourable environmental conditions for many terrestrial and aquatic organisms adapted to natural flooding regimes. In Australia, the Murray River floodplains have been subjected to decline in inundations, to extensive logging and to removal of fallen timber. The yellow-footed antechinus (Antechinus flavipes) is the only small, native, ground-dwelling/semi-arboreal mammal on most floodplains of south-eastern Australia, yet the effects of floods on its population dynamics largely are unknown. Here, we found positive effects of proximity to flooding, higher woodloads and of abundance of large, hollow-bearing trees on antechinus numbers. Mean trapping rates of antechinuses were lowest in 2003 following a 3-year period with no inundation, higher in 2004 following the first breeding season during a small, controlled flood in 2003, and higher again in 2005, following a small, controlled flood in 2004. In 2004 and 2005, trapping rates declined with distance from floodwaters. This study provides evidence for the benefits of using management flows to inundate floodplains, conserving large trees and ensuring high woodloads in floodplains for sustaining populations of the yellow-footed antechinus. 相似文献
84.
Over four hundred vegetation samples were collected for total Hg determination as part of a biogeochemical survey in the Precambrian
Shield region near Huntsville, Ontario. An objective of the survey was to obtain accurate data describing the spatial and
temporal variation of Hg concentrations in vegetation. Five tree species, clubmosses, mosses, lichen and fungi were collected
along three transects each 8 to 10 km long. The samples were digested using a hot H2SO4/HNO3 mixture followed by cold-vapor AAS detection. Very low detection limits (less than 1.0 ng g−1) were achieved by performing the analyses in a clean, Hg-free laboratory. The Hg concentration of coniferous needles did
not vary significantly over eight weeks of the summer, but did vary significantly between first and second year growth. In
all tree species examined, Hg concentrations in needles/leaves were two to three times as high (by dry weight) as that in
twig tissue from the same branch. Differences in Hg content between tissues of different types and ages constituted a major
source of within-site variation between plants of the same species. 相似文献
85.
Onisko BC Tambling DR Gorder GW Diaz DG Ericson JL Prisbylla MP Spillner CJ 《Journal of agricultural and food chemistry》2002,50(7):1922-1928
The metabolism of fonofos, a thiophosphonate insecticide, was investigated in mature lettuce (Latuca sativa), beet (Beta vulgaris), and wheat (Triticum aestivum). Six new metabolites were identified by LC-MS and LC-MS-MS analysis using fast atom bombardment (FAB) and packed capillary LC columns with application of the on-column focusing technique. These methods provided the sensitivity required to identify unknown metabolites that were present in the mature plants at only 20-230 ppb. Structural elucidation was facilitated by use of fonofos labeled with both carbon-14 and carbon-13 in the phenyl ring. In all three plants fonofos was converted to a glucose conjugate of thiophenoxylactic acid. Oxidation of the glucose conjugate gave isomeric sulfoxides in all species examined. Thiophenoxylactic acid was found esterified to malonic acid in lettuce. In beets, S-phenylcysteine was found as its malonic acid amide. A second metabolite unique to beets was N-(malonyl)-[2[(ethoxyethylphosphinothionyl)oxy]phenyl]cysteine. This novel structure was confirmed by synthesis. 相似文献
86.
87.
The objective of this study was to assess the stability of ELISA plates prepared with one of three blocking agents and used with one of two conjugates at various time intervals after preparation of the plates. Two of the blocking agents used were commercially available: one termed stabilgaurd (stab) and one manufactured by SVANOVA Biotek AB Inc. (svan). The third blocking agent used was bovine serum albumin (bsa). A polyclonal rabbit anti-bovine IgG (poly) and an anti-bovine IgG monoclonal (mono) conjugate were used. Eighteen composite individual cow milk samples collected late in lactation (200-400 days in milk) were used in this study. An indirect microtitre plate ELISA that used the Ostertagia ostertagi antigen was used to quantify antibodies against the parasite, present in the milk samples. Each of six blocking agent/conjugate combinations (called systems) were used to test 18 milk sub-samples at 1, 4 and 24 weeks after blocking the plates. Plates blocked with stab and svan were kept at room temperature and an additional set were incubated at 37 degrees C so as to mimic long term storage (about 1 year) and tested only once at 4 weeks. Those blocked with bsa were frozen at -20 degrees C. Concordance correlation coefficients (CCC) and reproducibility were used to assess the agreement between test results conducted on the same milk sample at the various test-times using a particular system. Generally, there was good agreement between tests conducted at different times for all systems. However, the svan-mono and bsa-poly systems had the best agreement with overall CCC values of 96% and 93%, respectively. The svan-poly system had the lowest CCC of 75%. The CCC and reproducibility ranked the systems in a similar way. The high CCC between tests done using plates kept at room temperature and ones incubated at 37 degrees C, suggested that plates would be stable up to a year after blocking. The storage of plates blocked with svan and stab agents under room temperature, makes them more convenient to use and transport relative to bsa-blocked plates that have to be frozen. 相似文献
88.
AIM: To determine the effect of increasing molybdenum (Mo) intakes on serum and liver copper (Cu) concentrations and growth rates of grazing red deer (Cervus elaphus). METHODS: Molybdenum- and Cu-amended fertilisers were applied to six 1.1-ha paddocks in a 3 x 2 design. Three levels of Mo were applied on two paddocks at each level in mid April (designated Day 1); levels were: none (control), 0.5 (medium) and 1.0 (high) kg Mo/ha as sodium molybdate. In late May (Day 39), two levels of Cu (none and 3.0 kg Cu/ha, as copper sulphate) were applied to each of the three levels of Mo-treated paddocks. Pasture Mo, Cu and sulphur (S) concentrations were measured at about fortnightly intervals. In late June (Day 74), ten 6-month-old red deer hinds were placed on the six experimental pastures, and serum and liver Cu concentrations were monitored at about monthly intervals for 102 days. The hinds were weighed on four occasions during the trial. RESULTS: Mean pasture Mo concentrations on Day 56 were 2, 4.6 and 11.3 mg/kg dry matter (DM) for the untreated control, medium and high Mo-treated pastures, respectively. Pasture Cu concentration was 95 mg/kg DM on Day 59, 53 mg/kg DM on Day 90, and 9 mg/kg DM by Day 153. Mean S concentration in pasture was 3.3 (range 3.03-3.45) g/kg DM. Copper application to pasture had no significant effect on serum and liver Cu concentrations in deer so data were pooled within Mo treatment. Mean initial (Day 74) serum Cu concentration was 9.2 micromol/L. In the deer grazing the control Mo pasture, this increased to 10.3 micromol/L on Day 112, before decreasing to 6.4 micromol/L on Day 176. In deer grazing the medium and high Mo-treated pastures, mean serum Cu concentrations were 3.8 and 3.9 micromol/L, respectively, on Day 112, and 2.5 and 3.3 micromol/L, respectively, on Day 176. Mean initial (Day 74) liver Cu concentration was 131 micromol/kg fresh tissue. In the deer grazing the control Mo pasture, this declined to 120 and 52 micromol/kg on Days 112 and Day 176, respectively. In deer grazing the medium and high Mo-treated pastures, liver Cu concentrations decreased to 55 and 52 micromol/kg fresh tissue, respectively, on Day 112, and 21 and 20 micromol/kg fresh tissue, respectively, on Day 176. Mean serum and liver Cu concentrations were not significantly different between deer grazing the medium and high Mo-treated pastures, and were lower (serum p=0.003, liver p<0.001) in those groups than in deer grazing the untreated control pastures. No clinical signs of Cu deficiency associated with lameness were observed. Deer grazing pastures that had Mo concentrations >10 mg/kg DM had lower (p=0.002) growth rates (100 vs 130 g/day) than those on pastures containing <2.4 mg Mo/kg DM. CONCLUSION: Increasing pasture Mo concentrations from 2 mg/kg DM to > or =4.6 mg/kg DM significantly reduced serum and liver Cu concentrations in grazing deer. Reduced growth rate was observed at pasture Mo concentrations >10 mg/kg DM. 相似文献
89.
Supernumerary cheek teeth (n = 24): clinical features, diagnosis, treatment and outcome in 15 horses
REASONS FOR PERFORMING STUDY: There are few reports of case series of horses with supernumerary cheek teeth (SCT) that document clinical findings, treatment and long-term outcome. OBJECTIVES: To review the clinical and ancillary diagnostic findings and responses to different treatments in horses with SCT. METHODS: The case records of 15 horses were reviewed and long-term outcomes obtained by telephone interview. RESULTS: Fifteen horses with a total of 24 SCT were identified. Two SCT were incidental findings and were not treated. Clinical signs were improved or resolved in 11 of 13 of the teeth treated conservatively and all 6 treated by extraction had a favourable outcome. Four horses were subjected to euthanasia within a short period of diagnosis, either due to a poor prognosis at the outset or failure to respond to initial conservative treatment. CONCLUSIONS: Some SCT are chance findings and do not cause clinical signs. In those instances where clinical signs of dental disease are mild, conservative treatment including the management of diastema and reduction of overgrowths is often effective. Horses with severe clinical signs attributable to an SCT are likely to require extraction of the offending tooth. POTENTIAL RELEVANCE: An SCT is an uncommon dental anomaly but should be considered in the differential diagnosis of cases with signs of severe dental disease. The preferred management for SCT is very variable and determined by the severity of the associated changes, but ranges from conservative measures through forceps extraction per os to major facial flap surgery. 相似文献
90.
R. F. Webb C. A. Quinn F. A. Cockram A. J. Husband† 《Australian veterinary journal》1980,56(4):172-175
Procedures for the diagnosis of Br. ovis infection in rams were evaluated by examining 10 rams artificially infected by preputial inoculation. Observations were undertaken at weekly intervals for 1 year to follow changes in clinical, bacteriological and serological findings. Clinical lesions were detected in 1 ram 3 weeks after inoculation and in all rams by 8 weeks; lesions were undetectable in 3 rams at the completion of the trial. The presence of inflammatory cells in semen samples was the earliest indication of infection being demonstrated in 2 rams at 2 weeks and in all rams by 8 weeks; subsequently 86% of samples were positive. Br. ovis was detected in semen smears from 3 rams at 4 weeks but only once in all rams (at 27 weeks); overall 52% of semen smears were positive from 4 weeks onwards. Br. ovis was cultured from semen of 5 rams after 4 weeks and from all rams at 5 weeks; thereafter 97% of samples were positive. All rams developed significant titres to the CFT between 2 and 9 weeks; thereafter the CFT was a reliable indication of infection in 6 rams, highly suggestive in 3 and unreliable in one. By 8–10 weeks all rams developed significant titres to the IHA which were then maintained in all rams for the remainder of the trial. 相似文献