全文获取类型
收费全文 | 737篇 |
免费 | 63篇 |
专业分类
林业 | 8篇 |
农学 | 4篇 |
基础科学 | 4篇 |
56篇 | |
综合类 | 107篇 |
农作物 | 22篇 |
水产渔业 | 23篇 |
畜牧兽医 | 514篇 |
园艺 | 8篇 |
植物保护 | 54篇 |
出版年
2022年 | 6篇 |
2021年 | 10篇 |
2020年 | 13篇 |
2019年 | 15篇 |
2018年 | 13篇 |
2017年 | 22篇 |
2016年 | 15篇 |
2015年 | 17篇 |
2014年 | 11篇 |
2013年 | 34篇 |
2012年 | 32篇 |
2011年 | 30篇 |
2010年 | 26篇 |
2009年 | 21篇 |
2008年 | 35篇 |
2007年 | 29篇 |
2006年 | 27篇 |
2005年 | 22篇 |
2004年 | 24篇 |
2003年 | 32篇 |
2002年 | 27篇 |
2001年 | 22篇 |
2000年 | 19篇 |
1999年 | 19篇 |
1998年 | 18篇 |
1995年 | 6篇 |
1994年 | 8篇 |
1993年 | 5篇 |
1992年 | 10篇 |
1991年 | 12篇 |
1990年 | 11篇 |
1989年 | 10篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1985年 | 7篇 |
1984年 | 9篇 |
1980年 | 6篇 |
1979年 | 10篇 |
1978年 | 7篇 |
1976年 | 10篇 |
1975年 | 7篇 |
1974年 | 7篇 |
1973年 | 8篇 |
1972年 | 9篇 |
1971年 | 11篇 |
1970年 | 6篇 |
1969年 | 7篇 |
1968年 | 5篇 |
1966年 | 7篇 |
1924年 | 5篇 |
排序方式: 共有800条查询结果,搜索用时 15 毫秒
21.
de Laforcade AM Freeman LM Rush JE 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2003,17(3):315-318
The purpose of this study was to determine whether nitric oxide (NO) concentrations are high in dogs with chronic valvular disease (CVD) and dilated cardiomyopathy (DCM) compared to healthy controls and to determine whether NO concentrations are correlated with type of cardiac disease, disease severity, medical therapy, or serum tumor necrosis factor (TNF) and interleukin-1 (IL-1). Blood was collected from 32 dogs with DCM, from 10 dogs with CVD, and from 10 healthy controls. Indirect determination of NO concentrations was performed by a commercial photoabsorbance assay that uses a Greiss reagent to measure the concentration of nitrite and nitrate (NN), end products of NO metabolism. TNF and IL-1 activities were measured by bioassay. Mean NN concentrations were significantly higher in dogs with heart disease (median, 4.57 microM; range, 0.00-31.05 microM) than in controls (median, 0.00 microM; range, 0.00-6.16 microM; P = .04). NN concentrations in dogs with cardiac disease were not correlated with type or severity of cardiac disease, medication type, or TNF and IL-1 concentrations. NN concentrations were inversely correlated with fractional shortening. The results of this study suggest that metabolites of NO are increased in some dogs with cardiac disease, but these increases appear to be independent of disease severity, TNF and IL-1 concentrations, and type of pharmacologic intervention. 相似文献
22.
Denoyes-Rothan B Guérin G Délye C Smith B Minz D Maymon M Freeman S 《Phytopathology》2003,93(2):219-228
ABSTRACT Ninety-five isolates of Colletotrichum including 81 isolates of C. acutatum (62 from strawberry) and 14 isolates of C. gloeosporioides (13 from strawberry) were characterized by various molecular methods and pathogenicity tests. Results based on random amplified polymorphic DNA (RAPD) polymorphism and internal transcribed spacer (ITS) 2 sequence data provided clear genetic evidence of two subgroups in C. acutatum. The first subgroup, characterized as CA-clonal, included only isolates from strawberry and exhibited identical RAPD patterns and nearly identical ITS2 sequence analysis. A larger genetic group, CA-variable, included isolates from various hosts and exhibited variable RAPD patterns and divergent ITS2 sequence analysis. Within the C. acutatum population isolated from strawberry, the CA-clonal group is prevalent in Europe (54 isolates of 62). A subset of European C. acutatum isolates isolated from strawberry and representing the CA-clonal and CA-variable groups was assigned to two pathogenicity groups. No correlation could be drawn between genetic and pathogenicity groups. On the basis of molecular data, it is proposed that the CA-clonal subgroup contains closely related, highly virulent C. acutatum isolates that may have developed host specialization to strawberry. C. gloeosporioides isolates from Europe, which were rarely observed were either slightly or nonpathogenic on strawberry. The absence of correlation between genetic polymorphism and geographical origin in Colletotrichum spp. suggests a worldwide dissemination of isolates, probably through international plant exchanges. 相似文献
23.
Waldrop JE Rozanski EA Freeman LM Rush JE 《Journal of the American Animal Hospital Association》2003,39(6):523-527
Fifty-five dogs received packed red blood cell (PRBC) transfusions for gastrointestinal (GI) hemorrhage during a 26-month period (1999 to 2001), accounting for 11.7% of the PRBC transfusions in that time. Thirty-nine (61%) dogs had an intestinal pathology (primary or secondary) as the cause of GI hemorrhage, including intestinal masses, gastroenteritis, hepatic disease, and renal disease. Nonsteroidal and steroidal anti-inflammatory drug use was found frequently in dogs with GI hemorrhage. Sixteen (39%) dogs were identified as having immune-mediated thrombocytopenia (IMT) and associated GI hemorrhage. Dogs with IMT received more transfusions of PRBC than nonIMT dogs (P<0.03) and received a significantly larger total volume of PRBC (P<0.01) during hospitalization. 相似文献
24.
Richter RA Freeman DE Wallig M Whittem T Baker GJ 《American journal of veterinary research》2002,63(7):934-941
OBJECTIVES: To study the functional and structural responses of the right dorsal colon (RDC) of ponies to phenylbutazone (PBZ) in vitro at a concentration that could be achieved in vivo. ANIMALS: 8 adult ponies. PROCEDURE: Short circuit current and conductance were measured in mucosa from the RDC. Tissues incubated with and without HCO3- were exposed to PBZ, bumetanide, or indomethacin. Bidirectional Cl- fluxes were determined. After a baseline flux period, prostaglandin E2 (PGE2) was added to the serosal surfaces and a second flux period followed. Light and transmission electron microscopy were performed. RESULTS: Baseline short circuit current was diminished significantly by PBZ and indomethacin, and increased significantly after addictions of PGE2. After PGE2 was added, Cl- secretion increased significantly in tissues in HCO3- -free solutions and solutions with anti-inflammatory drugs, compared with corresponding baseline measurements and with control tissues exposed to PGE2. Bumetanide did not affect baseline short circuit current and Cl- fluxes. The predominant histologic change was apoptosis of surface epithelial cells treated with PBZ and to a lesser extent in those treated with indomethacin. CONCLUSIONS AND CLINICAL RELEVANCE: Prostaglandin-induced Cl- secretion appeared to involve a transporter that might also secrete HCO3-. Both PBZ and indomethacin altered ion transport in RDC and caused apoptosis; PBZ can damage mucosa through a mechanism that could be important in vivo. The clinically harmful effect of PBZ on equine RDC in vivo could be mediated through its effects on Cl- and HCO3- secretion. 相似文献
25.
26.
Host Range and Characterization of Sunflower mosaic virus 总被引:1,自引:0,他引:1
ABSTRACT Sunflower mosaic is caused by a putative member of the family Potyviridae. Sunflower mosaic virus (SuMV) was characterized in terms of host range, physical and biological characteristics, and partial nucleotide and amino acid sequence. Cells infected with SuMV had cytoplasmic inclusion bodies typical of potyviruses. Of 74 genera tested, only species in Helianthus, Sanvitalia, and Zinnia, all Asteraceae, were systemic hosts. Commercial sunflower hybrids from the United States, Europe, and South Africa were all equally susceptible. The mean length of purified particles is approximately 723 nm. The virus was transmitted by Myzus persicae and Capitphorus elaegni, and also was seedborne in at least one sunflower cultivar. Indirect enzyme-linked immunosorbent assay tests with a broad-spectrum potyvirus monoclonal antibody were strongly positive. SuMV-specific polyclonal antisera recognized SuMV and, to a lesser extent, Tobacco etch virus (TEV). When tested against a panel of 31 potyvirus-differentiating monoclonal antibodies, SuMV was distinct from any potyvirus previously tested. SuMV shared four epitopes with TEV, but had a reaction profile more similar to Tulip breaking virus (TBV). SuMV did not possess epitopes unique only to TBV. The predicted coat protein had a molecular weight of 30.5 kDa. The 3' end of the virus genome was cloned and sequenced. Phylogenetic analysis of the coat protein amino acid sequence revealed that SuMV is a distinct species within the family Potyviridae, most closely related to TEV. 相似文献
27.
28.
29.
S. Hughes B. Reynolds S. A. Brittain J. A. Hudson C. Freeman 《Soil Use and Management》1998,14(4):248-251
Abstract. Recently, there has been interest in the occurrence of bromide (Br- ) in natural waters since it has been demonstrated that Br- , in association with humic substances in raw waters, is readily incorporated into haloacetic acids in the form of organically bound bromine (Br) during water chlorination. We report results of the effects of experimentally rewetting a naturally drained gully mire on the hydrochemistry of Br- , iron (Fe) and dissolved organic carbon (DOC) in the peat water. Results obtained over a three year period showed that rewetting substantially increased the concentrations of these solutes in the pore water, with peak values of 1 mg dm-3 (Br- ), > 60 mg dm-3 (Fe) and > 300 mg dm-3 (DOC) detected in some samples after rewetting, compared with typical values < 0.05 mg dm-3 (Br- ), < 1 mg dm-3 (Fe) and < 15 mg dm-3 (DOC) under the drained conditions. Bromide, Fe and DOC release were highly seasonal, with the largest concentrations observed in late-summer to autumn. However, whereas seasonal peak concentrations of Fe and DOC have since remained at these higher levels, seasonal peak concentrations of Br- were progressively attenuated over time, suggesting the latter phenomenon is a flush effect, with no longer-term consequences for water quality. 相似文献
30.
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