全文获取类型
收费全文 | 644篇 |
免费 | 42篇 |
专业分类
林业 | 20篇 |
农学 | 14篇 |
基础科学 | 1篇 |
44篇 | |
综合类 | 130篇 |
农作物 | 8篇 |
水产渔业 | 23篇 |
畜牧兽医 | 417篇 |
园艺 | 14篇 |
植物保护 | 15篇 |
出版年
2021年 | 7篇 |
2020年 | 5篇 |
2019年 | 12篇 |
2018年 | 6篇 |
2016年 | 15篇 |
2015年 | 5篇 |
2014年 | 14篇 |
2013年 | 28篇 |
2012年 | 19篇 |
2011年 | 15篇 |
2010年 | 12篇 |
2009年 | 24篇 |
2008年 | 33篇 |
2007年 | 28篇 |
2006年 | 17篇 |
2005年 | 17篇 |
2004年 | 35篇 |
2003年 | 12篇 |
2002年 | 17篇 |
2001年 | 20篇 |
2000年 | 16篇 |
1999年 | 12篇 |
1998年 | 19篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 6篇 |
1992年 | 14篇 |
1991年 | 15篇 |
1990年 | 15篇 |
1989年 | 13篇 |
1988年 | 5篇 |
1987年 | 10篇 |
1986年 | 8篇 |
1985年 | 17篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1980年 | 10篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1974年 | 12篇 |
1973年 | 11篇 |
1972年 | 5篇 |
1971年 | 6篇 |
1970年 | 6篇 |
1966年 | 4篇 |
1942年 | 4篇 |
1911年 | 4篇 |
排序方式: 共有686条查询结果,搜索用时 125 毫秒
31.
Summary Hemlock sawdust samples degraded by Ganoderma applanatum showed no electron-dense particles either in hyphae or in wood cell walls after aldehyde/OsO4 fixation. After KMnO4 fixation at early stage of attack, particles were in hyphae, hyphal sheath and wood cell walls. In samples prepared by a cytochemical technique which localizes cellulase activity at the ultrastructural level, particles were in hyphae, hyphal sheath and wood cell walls. The smallest diameter range of the particles lay between 3 and 7 nm which corresponds to the size of cellulases. Larger diameter particles were peresent which are probably aggregates of the smaller units. We believe that particles present in hyphal cytoplasm and hyphal sheath are cellulolytic enzymes. Whether particles present in attacked wood cell walls are enzymes or degradation products cannot be determined by this study. Nevertheles, the particles reveal the decay pattern in wood by the white-rot fungus G. applanatum. 相似文献
32.
33.
Agu RC Brosnan JM Bringhurst TA Palmer GH Jack FR 《Journal of agricultural and food chemistry》2007,55(9):3702-3707
Detailed studies were carried out on the influence of corn size distribution on the values obtained for diastatic power (DP) of commercially malted barley. Malted barley was screened using a screening box, and the DP activities of the different corns retained on the different compartments of the screening box were determined. The malt samples retained on the 2.8 mm screen had the highest DP activity, whereas the small corns (相似文献
34.
Csizmadi I Kahle L Ullman R Dawe U Zimmerman TP Friedenreich CM Bryant H Subar AF 《Public health nutrition》2007,10(1):88-96
BACKGROUND AND OBJECTIVE: Despite assumed similarities in Canadian and US dietary habits, some differences in food availability and nutrient fortification exist. Food-frequency questionnaires designed for the USA may therefore not provide the most accurate estimates of dietary intake in Canadian populations. Hence, we undertook to evaluate and modify the National Cancer Institute's Diet History Questionnaire (DHQ) and nutrient database. METHODS: Of the foods queried on the DHQ, those most likely to differ in nutrient composition were identified. Where possible these foods were matched to comparable foods in the Canadian Nutrient File. Nutrient values were examined and modified to reflect the Canadian content of minerals (calcium, iron, zinc) and vitamins (A, C, D, thiamin, riboflavin, niacin, B6, folate and B12). DHQs completed by 13 181 Alberta Cohort Study participants aged 35-69 years were analysed to estimate nutrient intakes using the original US and modified versions of the DHQ databases. Misclassification of intake for meeting the Dietary Reference Intake (DRI) was determined following analysis with the US nutrient database. RESULTS: Twenty-five per cent of 2411 foods deemed most likely to differ in nutrient profile were subsequently modified for folate, 11% for vitamin D, 10% for calcium and riboflavin, and between 7 and 10% for the remaining nutrients of interest. Misclassification with respect to meeting the DRI varied but was highest for folate (7%) and vitamin A (7%) among men, and for vitamin D (7%) among women over 50 years of age. CONCLUSIOn: Errors in nutrient intake estimates owing to differences in food fortification between the USA and Canada can be reduced in Canadian populations by using nutrient databases that reflect Canadian fortification practices. 相似文献
35.
N. B. Martin D. F. Houlihan C. Talbot R. M. Palmer 《Fish physiology and biochemistry》1993,12(2):131-141
Body composition and fractional rates of protein synthesis (percentage of the protein mass synthesized per day) were determined
in female Atlantic salmon returning to the River Tay, Scotland in July and in October after a 95 day period without food,
during which time the animals became sexually mature. During the 95 day period of starvation/sexual maturation the ventricle
and red muscle remained as a constant proportion of fresh weight whereas the liver, gill and ovary increased and the stomach
and white muscle decreased. Fractional rates of protein synthesis increased markedly in the liver, stomach and ovary during
the period of starvation/sexual maturation. In the gill, ventricle and white muscle fractional protein synthesis rates increased
slightly or remained constant. From the estimated rates of protein loss or gain in the various tissues it is concluded that
there is considerable protein turnover and repartitioning of amino acids during the period of starvation and sexual maturation.
The absolute rate of protein synthesis rates in the ovary indicates that this tissue made the largest contribution to the
energy and amino acid demands of the fish, whilst most of the amino acids required for maturation of the ovary were derived
from white muscle, principally as the result of increased muscle protein degradation. 相似文献
36.
37.
R. E. Luna‐Gierke K. Wymore J. Sadlowski P. Clogher R. W. Gierke M. Tobin‐D'Angelo A. Palmer C. Medus C. Nicholson S. McGuire H. Martin K. Garman P. M. Griffin R. K. Mody 《Zoonoses and public health》2014,61(7):492-498
We describe multiple‐aetiology infections involving non‐O157 Shiga toxin‐producing Escherichia coli (STEC) identified through laboratory‐based surveillance in nine FoodNet sites from 2001 to 2010. A multiple‐aetiology infection (MEI) was defined as isolation of non‐O157 STEC and laboratory evidence of any of the other nine pathogens under surveillance or isolation of >1 non‐O157 STEC serogroup from the same person within a 7‐day period. We compared exposures of patients with MEI during 2001–2010 with those of patients with single‐aetiology non‐O157 STEC infections (SEI) during 2008–2009 and with those of the FoodNet population from a survey conducted during 2006–2007. In total, 1870 non‐O157 STEC infections were reported; 68 (3.6%) were MEI; 60 included pathogens other than non‐O157 STEC; and eight involved >1 serogroup of non‐O157 STEC. Of the 68 MEI, 21 (31%) were part of six outbreaks. STEC O111 was isolated in 44% of all MEI. Of patients with MEI, 50% had contact with farm animals compared with 29% (P < 0.01) of persons with SEI; this difference was driven by infections involving STEC O111. More patients with non‐outbreak‐associated MEI reported drinking well water (62%) than respondents in a population survey (19%) (P < 0.01). Drinking well water and having contact with animals may be important exposures for MEI, especially those involving STEC O111. 相似文献
38.
Drosou Konstantina Craig Hayley Palmer Karren Kennedy Sandra L. Wishart John Oliveira Hugo R. Civáň Peter Martin Peter Brown Terence A. 《Genetic Resources and Crop Evolution》2022,69(7):2361-2381
Genetic Resources and Crop Evolution - We used genotyping-by-sequencing to investigate the evolutionary history of bere, the oldest barley variety still cultivated in Britain and possibly in all of... 相似文献
39.
S L Berger R H Palmer C C Hodges D G Hall 《Journal of the American Veterinary Medical Association》1991,198(1):132-134
A 13-month-old Doberman Pinscher was evaluated because of slowly progressive paraparesis and signs of depression. The dog had temporal, supraspinatus, and infraspinatus muscle atrophy, bilateral enophthalmos, superficial inguinal lymphadenopathy, tachycardia with pulse deficits, and lesions of active and inactive chorioretinitis. Neurologic abnormalities included hyperreflexic patellar reflexes, lack of conscious proprioception, signs of superficial pain in the hind limbs, and depressed hopping reflexes in the forelimbs. Cranial nerve abnormalities included decreased sensation in the left nostril and a delayed gag reflex. Results of cerebrospinal fluid analysis were characteristic of nonsuppurative inflammation. A diagnosis of multifocal neurologic disease was made. The dog did not have serum titers for fungal diseases, canine distemper, Ehrlichia canis infection, borreliosis, Rocky Mountain spotted fever, or toxoplasmosis. The dog did not respond to various antimicrobial treatments, and only slightly responded to corticosteroid treatment. The dog died during an anesthetic procedure. The postmortem diagnosis of Trypanosoma cruzi infection (canine Chagas disease) was made on identification of the amastigote form of the organism in sections of brain, spinal cord, and myocardium. 相似文献
40.
Summary Light and fluorescence microscopy were used to study coenocytic microspore germination from male-sterile (ms1 ms1) soybean plants. Anther squashes from male-sterile plants revealed that a low frequency of natural coenocytic microspore germination occurred in male-sterile anthers of four independent lines; [ms1-North carolina (T260H),ms1-Urbana (T266H),ms1-Tonica (T267H), andms1-Ames (T268H)]. Abnormalities such as giant tubes, branched tubes, tubes with swollen areas, and multiple tubes were observed from coenocytic microspores from all four lines. The Urbana line, however, demonstrated a higher percentage of coenocytic microspore germination than did the other three lines. Flowers of the Urbana line from both malefertile and male-sterile plants, as well as gynoecia pollinated with coenocytic microspores from sterile plants, were used for in vivo studies. Pollen-tube growth appeared normal in male-fertile plants. In contrast, coenocytic microspore tubes rarely were observed in gynoecia from male-sterile plants or in gynoecia from malefertile plants that had been artificially cross-pollinated withms1 ms1 plants. Few tubes from coenocytic microspores were observed in the vicinity of the micropylar region. A low frequency of seed set was achieved in the greenhouse on Urbana male-sterile plants grown in the absence of male-fertile plants. Thus, we believe either that some gametes from coenocytic microspores are able to participate in fertilization at low frequency or that apomixis occurs inms1 ms1 plants.Joint contribution: Agricultural Research Service, U.S. Department of Agriculture, and Journal Paper No. J-12310 of the Iowa Agriculture and Home Economics Experiment Station, Ames IA, 50011 USA. Project 2471. 相似文献