全文获取类型
收费全文 | 763篇 |
免费 | 8篇 |
专业分类
林业 | 24篇 |
基础科学 | 1篇 |
44篇 | |
综合类 | 303篇 |
农作物 | 4篇 |
水产渔业 | 2篇 |
畜牧兽医 | 361篇 |
植物保护 | 32篇 |
出版年
2012年 | 35篇 |
2011年 | 63篇 |
2010年 | 9篇 |
2009年 | 5篇 |
2008年 | 44篇 |
2007年 | 54篇 |
2006年 | 39篇 |
2005年 | 33篇 |
2004年 | 43篇 |
2003年 | 49篇 |
2002年 | 29篇 |
2001年 | 32篇 |
2000年 | 39篇 |
1999年 | 25篇 |
1998年 | 8篇 |
1994年 | 8篇 |
1993年 | 12篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 9篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 11篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1979年 | 6篇 |
1976年 | 5篇 |
1974年 | 6篇 |
1970年 | 8篇 |
1969年 | 6篇 |
1966年 | 7篇 |
1963年 | 4篇 |
1961年 | 3篇 |
1960年 | 4篇 |
1959年 | 3篇 |
1958年 | 4篇 |
1957年 | 7篇 |
1955年 | 4篇 |
1954年 | 7篇 |
1953年 | 3篇 |
1942年 | 6篇 |
1941年 | 5篇 |
1939年 | 3篇 |
1938年 | 10篇 |
1937年 | 3篇 |
1935年 | 3篇 |
1933年 | 3篇 |
1924年 | 3篇 |
1916年 | 3篇 |
排序方式: 共有771条查询结果,搜索用时 109 毫秒
101.
Anderson WA Amasino RM Ares M Banerjee U Bartel B Corces VG Drennan CL Elgin SC Epstein IR Fanning E Guillette LJ Handelsman J Hatfull GF Hoy RR Kelley D Leinwand LA Losick R Lu Y Lynn DG Neuhauser C O'Dowd DK Olivera T Pevzner P Richards-Kortum RR Rine J Sah RL Strobel SA Walker GC Walt DR Warner IM Wessler S Willard HF Zare RN 《Science (New York, N.Y.)》2011,334(6057):760-761
102.
Vitamin D and sterol composition of 10 types of mushrooms from retail suppliers in the United States
Phillips KM Ruggio DM Horst RL Minor B Simon RR Feeney MJ Byrdwell WC Haytowitz DB 《Journal of agricultural and food chemistry》2011,59(14):7841-7853
Vitamin D(2) (ergocalciferol) and sterols were analyzed in mushrooms sampled nationwide in the United States to update the USDA Nutrient Database for Standard Reference. Vitamin D(2) was assayed using HPLC with [(3)H]-vitamin D(3) internal standard and sterols by GC-FID mass spectrometric (MS) confirmation. Vitamin D(2) was low (0.1-0.3 μg/100 g) in Agaricus bisporus (white button, crimini, portabella) and enoki, moderate in shiitake and oyster (0.4-0.7 μg/100 g), and high in morel, chanterelle, maitake (5.2-28.1 μg/100 g) and UV-treated portabella (3.4-20.9 μg/100 g), with significant variability among composites for some types. Ergosterol (mg/100 g) was highest in maitake and shiitake (79.2, 84.9) and lowest in morel and enoki (26.3, 35.5); the range was <10 mg/100 g among white button composites but 12-50 mg/100 g among samples of other types. All mushrooms contained ergosta-5,7-dienol (22,23-dihydroergosterol) (3.53-18.0 mg/100 g) and (except morel) ergosta-7-enol. Only morel contained brassicasterol (28.6 mg/100 g) and campesterol (1.23-4.54 mg/100 g) and no ergosta-7,22-dienol. MS was critical in distinguishing campesterol from ergosta-7,22-dienol. 相似文献
103.
Simon RR Phillips KM Horst RL Munro IC 《Journal of agricultural and food chemistry》2011,59(16):8724-8732
This study compared the compositional changes in mushrooms exposed to sunlight with those occurring after commercial ultraviolet (UV) light processing. Button mushrooms (75 kg) were processed in the presence or absence of UVB light; a third group was exposed to direct sunlight. Mushroom composition was evaluated using chemical analyses. Vitamin D concentrations were 5, 410, and 374 μg/100 g (dw) in control, UVB, and sunlight groups, respectively. On a dry weight basis, no significant changes in vitamin C, folate, vitamins B(6), vitamin B(5), riboflavin, niacin, amino acids, fatty acids, ergosterol, or agaritine were observed following UVB processing. Sunlight exposure resulted in a 26% loss of riboflavin, evidence of folate oxidation, and unexplained increases in ergosterol (9.5%). It was concluded that compositional effects of UVB light are limited to changes in vitamin D and show no detrimental changes relative to natural sunlight exposure and, therefore, provide important information relevant to the suitability and safety of UVB light technology for vitamin D enhanced mushrooms. 相似文献
104.
Holtkamp DJ Polson DD Torremorell M Morrison B Classen DM Becton L Henry S Rodibaugh MT Rowland RR Snelson H Straw B Yeske P Zimmerman J;American Association of Swine Veterinarians;United States Department of Agriculture PRRS-Coordinated Agricultural Project 《Tier?rztliche Praxis. Ausgabe G, Grosstiere/Nutztiere》2011,39(2):101-112
Standardized terminology for the porcine reproductive and respiratory syndrome virus (PRRSV) status of swine herds is necessary to facilitate communication between veterinarians, swine producers, genetic companies, and other industry participants. It is also required for implementation of regional and national efforts towards PRRSV control and elimination. The purpose of this paper is to provide a herd classification system for describing the PRRSV status of herds, based upon a set of definitions reflecting the biology and ecology of PRRSV. The herd classification system was developed by a definitions committee formed jointly by the American Association of Swine Veterinarians (AASV) and the United States Department of Agriculture PRRS-Coordinated Agricultural Project, and was approved by the AASV Board of Directors on March 9, 2010. The committee included veterinarians from private practice and industry, researchers, and representatives from AASV and the National Pork Board. Breeding herds, with or without growing pigs on the same premises, are categorized as Positive Unstable (Category I), Positive Stable (Category II), Provisional Negative (Category III), or Negative (Category IV) on the basis of herd shedding and exposure status. Growing-pig herds are categorized as Positive or Negative. Recommended testing procedures and decision rules for herd classification are detailed. 相似文献
105.
Karlstam L Hertil E Zeiss C Ropstad EO Bjerkås E Dubielzig RR Ekesten B 《Veterinary ophthalmology》2011,14(4):227-238
Objective To describe a slowly progressive retinopathy (SPR) in Shetland Sheepdogs. Animals Forty adult Shetlands Sheepdogs with ophthalmoscopic signs of SPR and six normal Shetland Sheepdogs were included in the study. Procedure Ophthalmic examination including slit‐lamp biomicroscopy and ophthalmoscopy was performed in all dogs. Electroretinograms and obstacle course‐test were performed in 13 affected and 6 normal dogs. The SPR dogs were subdivided into two groups according to their dark‐adapted b‐wave amplitudes. SPR1‐dogs had ophthalmoscopic signs of SPR, but normal dark‐adapted b‐wave amplitudes. Dogs with both ophthalmoscopic signs and subnormal, dark‐adapted b‐wave amplitudes were assigned to group SPR2. Eyes from two SPR2 dogs were obtained for microscopic examination. Results The ophthalmoscopic changes included bilateral, symmetrical, greyish discoloration in the peripheral tapetal fundus with normal or marginally attenuated vessels. Repeated examination showed that the ophthalmoscopic changes slowly spread across the central parts of the tapetal fundus, but did not progress to obvious neuroretinal thinning presenting as tapetal hyper‐reflectivity. The dogs did not appear seriously visually impaired. SPR2 showed significantly reduced b‐wave amplitudes throughout dark‐adaptation. Microscopy showed thinning of the outer nuclear layer and abnormal appearance of rod and cone outer segments. Testing for the progressive rod–cone degeneration ( prcd )‐mutation in three dogs with SPR was negative. Conclusion Slowly progressive retinopathy is a generalized rod–cone degeneration that on ophthalmoscopy looks similar to early stages of progressive retinal atrophy. The ophthalmoscopic findings are slowly progressive without tapetal hyper‐reflectivity. Visual impairment is not obvious and the electroretinogram is more subtly altered than in progressive retinal atrophy. The etiology remains unclear. SPR is not caused by the prcd‐mutation. 相似文献
106.
This case series describes a rare entity, nasal angiofibroma, in 13 dogs that were presented to the University of Wisconsin, School of Veterinary Medicine from 1988 to 2000. All dogs in this case series presented with clinical signs and radiographic changes that were strongly suggestive of a locally invasive neoplasm. However, histopathology completed on transnostral core biopsy samples revealed benign appearing vascular proliferation with secondary lymphosuppurative inflammation was established despite cytologic criteria of malignancy present in five dogs. On the basis of the outcomes in this case series, nasal angiofibroma should be considered a differential for dogs presenting with clinical signs consistent with a malignant nasal tumour. 相似文献
107.
Wang J Chan WG Haut SA Krauss MR Izac RR Hempfling WP 《Journal of agricultural and food chemistry》2005,53(12):4686-4691
A method for the determination of total N-nitroso compounds (NOC) by chemical denitrosation and subsequent chemiluminescence detection of evolved NO is described. Denitrosation was accomplished with CuCl in HCl at 70 degrees C. The detection limit for N-nitrosoproline (NPRO) was 1 pmol. NO formation from NPRO was linear (R(2) = 0.999) from 4 pmol to 2 nmol. Among the possible interfering compounds tested, only S-nitroso compounds contribute any significant interference. This method had several advantages over other similar methods: (1) A commercially available one-piece reaction vessel and a NO analyzer with software were used. (2) NO release occurred rapidly and was easily measured and quantified. (3) Compared to HBr or HI, CuCl was more convenient to work with and safe. (4) CuCl was suitable for samples in aqueous and most organic solvents. The application of this method to food, personal care products, and human body fluids demonstrates its utility. 相似文献
108.
109.
MARSHAK RR 《Journal of the American Veterinary Medical Association》1954,125(933):449-450
110.
The frequency sensitivity of the auditory nervous system of cricket frogs (Acris) varies geographically. This variation is closely matched to the spectral energy in their mating calls, thus enabling them to respond preferentially to the calls of their local dialect. 相似文献