全文获取类型
收费全文 | 1492篇 |
免费 | 99篇 |
国内免费 | 2篇 |
专业分类
林业 | 64篇 |
农学 | 27篇 |
基础科学 | 16篇 |
243篇 | |
综合类 | 256篇 |
农作物 | 48篇 |
水产渔业 | 82篇 |
畜牧兽医 | 679篇 |
园艺 | 40篇 |
植物保护 | 138篇 |
出版年
2023年 | 7篇 |
2022年 | 8篇 |
2021年 | 16篇 |
2020年 | 32篇 |
2019年 | 25篇 |
2018年 | 24篇 |
2017年 | 24篇 |
2016年 | 27篇 |
2015年 | 27篇 |
2014年 | 29篇 |
2013年 | 75篇 |
2012年 | 80篇 |
2011年 | 105篇 |
2010年 | 71篇 |
2009年 | 43篇 |
2008年 | 106篇 |
2007年 | 111篇 |
2006年 | 100篇 |
2005年 | 92篇 |
2004年 | 86篇 |
2003年 | 80篇 |
2002年 | 104篇 |
2001年 | 18篇 |
2000年 | 21篇 |
1999年 | 20篇 |
1998年 | 21篇 |
1997年 | 16篇 |
1996年 | 20篇 |
1995年 | 8篇 |
1994年 | 12篇 |
1993年 | 15篇 |
1992年 | 14篇 |
1991年 | 9篇 |
1990年 | 10篇 |
1989年 | 15篇 |
1988年 | 5篇 |
1987年 | 12篇 |
1986年 | 7篇 |
1985年 | 5篇 |
1984年 | 9篇 |
1983年 | 12篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 7篇 |
1977年 | 8篇 |
1976年 | 3篇 |
1974年 | 5篇 |
1971年 | 3篇 |
1968年 | 3篇 |
1962年 | 3篇 |
排序方式: 共有1593条查询结果,搜索用时 15 毫秒
131.
132.
Francisco A Uzal Derek J Fisher Juliann Saputo Sameera Sayeed Bruce A McClane Glenn Songer Hien T Trinh Mariano E Fernandez Miyakawa Sharon Gard 《Journal of veterinary diagnostic investigation》2008,20(5):668-672
Enterotoxemia caused by Clostridium perfringens type D in sheep is believed to result from the action of epsilon toxin (ETX). However, the sole role of ETX in the intestinal changes of the acute and chronic forms of enterotoxemia in goats remains controversial, and the synergistic action of other C. perfringens toxins has been suggested previously. The current study examined 2 goats that were found dead without premonitory clinical signs. Gross lesions at necropsy consisted of multifocal fibrinonecrotic enterocolitis, edematous lungs, and excess pleural fluid. Histologically, there were multifocal fibrinonecrotic and ulcerative ileitis and colitis, edema of the colonic serosa, and proteinaceous interstitial edema of the lungs. Clostridium perfringens type D carrying the genes for enterotoxin (CPE) and beta2 toxin (CPB2) was cultured from intestinal content and feces of 1 of 2 goats, while C. perfringens type D CPB2-positive was isolated from the other animal. When multiple colonies of the primary isolations from both animals were tested by Western blot, most of the isolates expressed CPB2, and only a few isolates from the first case expressed CPE. Alpha toxin and ETX were detected in ileal and colonic contents and feces of both animals by antigen capture enzyme-linked immunosorbent assay. CPB2, but not CPE, was identified in the small and large intestines of both goats by immunohistochemistry. These findings indicate that CPB2 may have contributed to the necrotic changes observed in the intestine, possibly assisting ETX transit across the intestinal mucosa. 相似文献
133.
Bordiga M Travaglia F Meyrand M German JB Lebrilla CB Coïsson JD Arlorio M Barile D 《Journal of agricultural and food chemistry》2012,60(14):3700-3707
Over forty-five complex free oligosaccharides (of which several are novel) have been isolated and chemically characterized by gas chromatography and high resolution and high mass accuracy matrix-assisted laser desorption/ionization mass spectrometry (MALDI-FTICR MS) in red and white wines, Grignolino and Chardonnay, respectively. Oligosaccharides with a degree of polymerization between 3 and 14 were separated from simple monosaccharides and disaccharides by solid-phase extraction. The concentrations of free oligosaccharides were over 100 mg/L in both red and white wines. The free oligosaccharides-characterized for the first time in the present study-include hexose-oligosaccharides, xyloglucans, and arabinogalactans and may be the natural byproduct of the degradation of cell wall polysaccharides. The coupled gas chromatography and accurate mass spectrometry approach revealed an effective method to characterize and quantify complex functional oligosaccharides in both red and white wine. 相似文献
134.
Isolation,purification, and biochemical characterization of a novel water soluble protein from Inca peanut (Plukenetia volubilis L.) 总被引:1,自引:0,他引:1
Sathe SK Hamaker BR Sze-Tao KW Venkatachalam M 《Journal of agricultural and food chemistry》2002,50(17):4906-4908
A water soluble storage albumin from Inca peanut (IPA) accounted for approximately 25% (w/w) of defatted seed flour weight, representing 31% of the total seed protein. IPA is a 3S storage protein composed of two glycosylated polypeptides, with estimated molecular weights (MW) of 32800 and 34800 Da, respectively. IPA has an estimated sugar content of 4.8% +/- 0.92% (n = 6). IPA is a basic protein (pI of approximately 9.4) and contains all of the essential amino acids in adequate amounts when compared to the FAO/WHO recommended pattern for a human adult. The tryptophan content of IPA is unusually high (44 mg/g of protein), whereas the phenylalanine content is low (9 mg/g of protein). IPA is a highly digestible protein in vitro. 相似文献
135.
The fate of Amazonian forest fragments: A 32-year investigation 总被引:2,自引:0,他引:2
William F. Laurance José L.C. Camargo Regina C.C. Luizão Susan G. Laurance Stuart L. Pimm Emilio M. Bruna Philip C. Stouffer G. Bruce Williamson Julieta Benítez-Malvido Heraldo L. Vasconcelos Kyle S. Van Houtan Charles E. Zartman Sarah A. Boyle Raphael K. Didham Ana Andrade Thomas E. Lovejoy 《Biological conservation》2011,(1):56-67
We synthesize findings to date from the world’s largest and longest-running experimental study of habitat fragmentation, located in central Amazonia. Over the past 32 years, Amazonian forest fragments ranging from 1 to 100 ha have experienced a wide array of ecological changes. Edge effects have been a dominant driver of fragment dynamics, strongly affecting forest microclimate, tree mortality, carbon storage, fauna, and other aspects of fragment ecology. However, edge-effect intensity varies markedly in space and time, and is influenced by factors such as edge age, the number of nearby edges, and the adjoining matrix of modified vegetation surrounding fragments. In our study area, the matrix has changed markedly over the course of the study (evolving from large cattle pastures to mosaics of abandoned pasture and regrowth forest) and this in turn has strongly influenced fragment dynamics and faunal persistence. Rare weather events, especially windstorms and droughts, have further altered fragment ecology. In general, populations and communities of species in fragments are hyperdynamic relative to nearby intact forest. Some edge and fragment-isolation effects have declined with a partial recovery of secondary forests around fragments, but other changes, such as altered patterns of tree recruitment, are ongoing. Fragments are highly sensitive to external vicissitudes, and even small changes in local land-management practices may drive fragmented ecosystems in markedly different directions. The effects of fragmentation are likely to interact synergistically with other anthropogenic threats such as logging, hunting, and especially fire, creating an even greater peril for the Amazonian biota. 相似文献
136.
LoCascio RG Ninonuevo MR Freeman SL Sela DA Grimm R Lebrilla CB Mills DA German JB 《Journal of agricultural and food chemistry》2007,55(22):8914-8919
The molecular basis by which human breast milk supports the development of a protective intestinal microbiome in infants is unknown. After lactose and lipids, human milk oligosaccharides (HMOs) are quantitatively the third largest and most diverse component of breast milk. In this work, glycomic profiling of HMO consumption by bifidobacteria using Fourier transform ion cyclotron resonance mass spectrometry reveals that one species, Bifidobacterium longum biovar infantis ATCC 15697, an isolate from the infant gut, preferentially consumes small mass oligosaccharides, representing 63.9% of the total HMOs available. These HMOs were detected in human breast milk at the onset and constantly through the first month of lactation by use of high performance liquid chromatography-chip time-of-flight mass spectrometry. Further characterization revealed that strain ATCC 15697 possesses both fucosidase and sialidase activities not present in the other tested strains. This work provides evidence that these small mass HMOs are selectively metabolized by select bifidobacterial strains and represent a potential new class of bioactive molecules functioning as prebiotics to facilitate a protective gut colonization in breast-fed newborns. 相似文献
137.
While many species of earthworms are globally distributed, very little is known about the genetic population dynamics of this diverse group. We present the characterization of novel simple sequence repeat (SSR) markers, including primer information, number of alleles, repeat motif, and approximate size ranges, to be used in population genetic analyses of the earthworm Lumbricus rubellus Hoffmeister 1843. Specifically, we designed and characterized 12 novel, polymorphic markers derived from published expressed sequence tags (EST) for amplification in L. rubellus. The mean number of alleles per locus was 6.25 ± 1.91, indicating these markers will be sufficiently polymorphic for population genetic studies of this species. 相似文献
138.
Lee HJ Shan G Ahn KC Park EK Watanabe T Gee SJ Hammock BD 《Journal of agricultural and food chemistry》2004,52(5):1039-1043
A competitive enzyme-linked immunosorbent assay (ELISA) for the detection of cypermethrin was developed. Two haptens, the trans- and cis-isomers of 3-[(+/-)-cyano-3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropanecarbonyloxy]methyl]phenoxyacetic acid, were conjugated with thyroglobulin as immunogens. Four antisera were generated and screened against six different coating antigens. The assay that was the most sensitive for cypermethrin was optimized and characterized. The IC(50) for cypermethrin was 13.5 +/- 4.3 microg/L, and the lower detection limit (LDL) was 1.3 +/- 0.5 microg/L. This ELISA had relatively low cross-reactivities with other major pyrethroids, such as deltamethrin, phenothrin, resmethrin, fluvalinate, and permethrin. Methanol was found to be the best organic cosolvent for this ELISA, with an optimal sensitivity observed at a concentration of 40% (v/v). The assay parameters were unchanged at pH values between 5.0 and 8.0, whereas higher ionic strengths strongly suppressed the absorbances. To increase the sensitivity of the overall method, a C(18) sorbent-based solid-phase extraction was applied to various domestic and environmental water samples. The water samples, fortified with cypermethrin, were analyzed according to this method. Good recoveries and correlation with spike levels were observed. 相似文献
139.
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
140.
Steven W. Effler Carol M. Brooks Jeffrey M. Addess Susan M. Doerr Michelle L. Storey Bruce A. Wagner 《Water, air, and soil pollution》1991,55(3-4):427-444
Concentrations of Cl, total ammonia (TNH3), NO3 plus NO2, total P (TP), and soluble reactive P (SRP) were measured at two sites, located 5 km apart, on Ninemile Creek, New York, for a period of more than 8 mo. The sites bound the most recently formed Solvay waste beds, associated with the production of soda ash, that adjoin the creek. Concentrations of Cl and T-NH3 increased on average by factors of 16.1 and 7.6, respectively, over the monitored stream reach. The estimated average loadings of these materials to the stream over this reach were 2.3 × 105 and 1.2 × 102 kg d?1, respectively. These inputs are attributable to the Solvay waste beds. The loading of Cl from this source has not changed significantly over a 4 yr period since the closure of the soda ash manufacturing facility. This is the single largest source of Cl, and the second largest source of T-NH3, to polluted Onondaga Lake. Profiles of Cl in the lake indicated that at times the creek inflow plunges to subsurface layers as a result of its elevated density. This is at least in part a result of the creek's ionic enrichment. The concentration of SRP decreased by a factor of 2.0 on average over the study reach, probably due to adsorption to the CaCO3 deposits that cover the stream bed in this area. However, the TP load from the creek to the lake is not significantly affected by this phenomenon. 相似文献