全文获取类型
收费全文 | 5076篇 |
免费 | 599篇 |
国内免费 | 178篇 |
专业分类
林业 | 378篇 |
农学 | 529篇 |
基础科学 | 137篇 |
854篇 | |
综合类 | 929篇 |
农作物 | 251篇 |
水产渔业 | 443篇 |
畜牧兽医 | 1719篇 |
园艺 | 155篇 |
植物保护 | 458篇 |
出版年
2023年 | 66篇 |
2022年 | 74篇 |
2021年 | 67篇 |
2020年 | 78篇 |
2019年 | 135篇 |
2018年 | 243篇 |
2017年 | 245篇 |
2016年 | 203篇 |
2015年 | 220篇 |
2014年 | 214篇 |
2013年 | 257篇 |
2012年 | 279篇 |
2011年 | 340篇 |
2010年 | 346篇 |
2009年 | 276篇 |
2008年 | 313篇 |
2007年 | 278篇 |
2006年 | 261篇 |
2005年 | 235篇 |
2004年 | 151篇 |
2003年 | 138篇 |
2002年 | 85篇 |
2001年 | 184篇 |
2000年 | 194篇 |
1999年 | 134篇 |
1998年 | 85篇 |
1997年 | 72篇 |
1996年 | 66篇 |
1995年 | 61篇 |
1994年 | 46篇 |
1993年 | 41篇 |
1992年 | 68篇 |
1991年 | 57篇 |
1990年 | 61篇 |
1989年 | 36篇 |
1988年 | 44篇 |
1987年 | 22篇 |
1986年 | 25篇 |
1985年 | 16篇 |
1984年 | 9篇 |
1983年 | 12篇 |
1982年 | 5篇 |
1979年 | 9篇 |
1971年 | 4篇 |
1967年 | 4篇 |
1966年 | 6篇 |
1956年 | 4篇 |
1903年 | 4篇 |
1893年 | 4篇 |
1892年 | 7篇 |
排序方式: 共有5853条查询结果,搜索用时 15 毫秒
991.
Tabar MD Maggi RG Altet L Vilafranca M Francino O Roura X 《The Journal of small animal practice》2011,52(4):209-212
Generalised pyogranulomatous disease and hyperviscosity syndrome associated with a presumed monoclonal gammopathy was diagnosed in a three-year-old intact female Pomeranian. The Bartonella henselae antibody titer was 1:64 and Bartonella species DNA was amplified from the splenic tissue. Monoclonal gammopathies in dogs are typically associated with plasma cell and lymphoid dyscrasias and other inflammatory or infectious diseases such as ehrlichiosis and leishmaniosis. Based on this case report, infection with Bartonella species should also be added to the differential diagnoses for gammopathy in dogs. To the authors' knowledge, this is the first report of molecular evidence of Bartonella species infection in a sick dog in Spain. 相似文献
992.
One polyclonal antibody against florfenicol and thiamphenicol was produced and a competitive ELISA was developed for the detection of florfenicol and thiamphenicol in swine feed. The ELISA gave a 50% inhibiting concentration of 1.02 ng/mL for florfenicol. For swine feed fortified with 0.05 to 3.0 mg/kg, the interassay recoveries of florfenicol and thiamphenicol ranged from 86.4 to 118.6%, whereas intraassay recoveries of both drug ranged from 90.1 to 126.5% with less than 15% CV. Results obtained from HPLC-tandem mass spectrometry indicated this ELISA procedure could be used as a convenient method for rapid screening of florfenicol and thiamphenicol in swine feed. 相似文献
993.
Feng Q Wu GH Liang TM Ji HY Jiang XJ Gu W Wang W 《Journal of veterinary pharmacology and therapeutics》2011,34(1):51-57
Feng, Q., Wu, G. H., Liang, T. M., Ji, H. Y., Jiang, X. J., Gu, W., Wang, W. Pharmacokinetics of oxytetracycline in hemolymph from the Chinese mitten crab, Eriocheir sinensis. J. vet. Pharmacol. Therap. 34 , 51–57. The purpose of this study was to investigate the hemolymph kinetics and depuration time of oxytetracycline following intramuscular administration at doses of 2, 8 and 40 mg/kg body weight, respectively. The concentration of OTC in hemolymph was assayed using solid phase extraction and high performance liquid chromatography. The elimination half‐life of the terminal part of the elimination phase (t1/2β) ranged from 87.9 to 114.3 h. The total body clearance (CLb) was 0.0430 L/kg/h at the lower dose, 0.0123 L/kg/h at the medium dose and 0.0013 L/kg/h at the higher dose. The apparent volume of the central compartment (Vc) was found to be 1.383, 0.699 and 0.143 L/kg respectively. The depuration time for each dose was 13.6, 29.6 and 57.6 days, respectively. Results from the present study suggest that the 40 mg/kg dose might have the best therapeutic efficacy following intramuscular administration. 相似文献
994.
Wang R Yuan LG He LM Zhu LX Luo XY Zhang CY Yu JJ Fang BH Liu YH 《Journal of veterinary pharmacology and therapeutics》2011,34(3):247-251
Wang, R., Yuan, L.G., He, L.M., Zhu, L.X., Luo, X.Y., Zhang, C.Y., Yu, J.J., Fang, B.H., Liu, Y.H. Pharmacokinetics and bioavailability of valnemulin in broiler chickens. J. vet. Pharmacol. Therap. 34 , 247–251. The objective of this study was to investigate the pharmacokinetics and bioavailability of valnemulin in broiler chickens after intravenous (i.v.), intramuscular (i.m.) and oral administrations of 10 mg/kg body weight (bw). Plasma samples were analyzed by high‐performance liquid chromatography–tandem mass spectrometry (HPLC‐MS/MS). Pharmacokinetic characterization was performed by non‐compartmental analysis using WinNonlin program. After intravenous administration, distribution was wide with the volume of distribution based on terminal phase(Vz) of 4.27 ± 0.99 L /kg. Mean valnemulin t1/2β(h), Clβ(L /h /kg), Vss (L /kg) and AUC(0–∞)(μg·h /mL) values were 2.85, 0.99, 2.72 and 10.34, respectively. After intramuscular administration, valnemulin was rapidly absorbed with a Cmax of 2.2 μg/mL achieved at 0.43 h (tmax), and the absolute bioavailability (F) was 88.81%; and for the oral route the same parameters were 0.66 ± 0.15 μg/mL, 1.54 ± 0.27 h and 74.42%. A multiple‐peak phenomenon was present after oral administration. The plasma profile of valnemulin exhibited a secondary peak during 2–6 h and a tertiary peak at 32 h. The favorable PK behavior, such as the wide distribution, slow elimination and acceptable bioavailability indicated that it is likely to be effective in chickens. 相似文献
995.
996.
Ai L Weng YB Elsheikha HM Zhao GH Alasaad S Chen JX Li J Li HL Wang CR Chen MX Lin RQ Zhu XQ 《Veterinary parasitology》2011,181(2-4):329-334
The present study examined sequence variability in a portion of the mitochondrial cytochrome c oxidase subunit 1 (pcox1) and NADH dehydrogenase subunits 4 and 5 (pnad4 and pnad5) among 39 isolates of Fasciola spp., from different hosts from China, Niger, France, the United States of America, and Spain; and their phylogenetic relationships were re-constructed. Intra-species sequence variations were 0.0-1.1% for pcox1, 0.0-2.7% for pnad4, and 0.0-3.3% for pnad5 for Fasciola hepatica; 0.0-1.8% for pcox1, 0.0-2.5% for pnad4, and 0.0-4.2% for pnad5 for Fasciola gigantica, and 0.0-0.9% for pcox1, 0.0-0.2% for pnad4, and 0.0-1.1% for pnad5 for the intermediate Fasciola form. Whereas, nucleotide differences were 2.1-2.7% for pcox1, 3.1-3.3% for pnad4, and 4.2-4.8% for pnad5 between F. hepatica and F. gigantica; were 1.3-1.5% for pcox1, 2.1-2.9% for pnad4, 3.1-3.4% for pnad5 between F. hepatica and the intermediate form; and were 0.9-1.1% for pcox1, 1.4-1.8% for pnad4, 2.2-2.4% for pnad5 between F. gigantica and the intermediate form. Phylogenetic analysis based on the combined sequences of pcox1, pnad4 and pnad5 revealed distinct groupings of isolates of F. hepatica, F. gigantica, or the intermediate Fasciola form irrespective of their origin, demonstrating the usefulness of the mtDNA sequences for the delineation of Fasciola species, and reinforcing the genetic evidence for the existence of the intermediate Fasciola form. 相似文献
997.
Macroautophagy is a cellular degradation mechanism that involves the delivery of cytosolic components (macromolecules or organelles) by the autophagosome to the lysosome for degradation. In mammalian cells, macroautophagy and the ubiquitin proteasome system are 2 major mechanisms to eliminate abnormal proteins accumulated in pathological conditions. Here, the coordination of the 2 pathways to alleviate endoplasmic reticulum stress is reviewed. Also discussed is the regulatory role of macroautophagy and proteasome activity in cell survival and death, as well as the recent discoveries leading to novel strategies of simultaneous control of the proteasome and autophagy activity in anticancer treatment. 相似文献
998.
Marilyn L. Warburton Garrison Wilkes S. Taba Alain Charcosset Celine Mir Fabrice Dumas Delphine Madur Susanne Dreisigacker Claudia Bedoya B. M. Prasanna C. X. Xie Sarah Hearne Jorge Franco 《Genetic Resources and Crop Evolution》2011,58(8):1243-1261
Maize (Zea mays L. ssp. mays) was domesticated from one wild species ancestor, the Balsas teosinte (Zea mays ssp. parviglumis) about 9000 years ago. Higher levels of gene diversity are found in teosinte taxa compared to maize, following domestication and selection bottlenecks. Diversity in maize can be increased via gene flow from teosinte, which has certainly occurred from various taxa, but the rate of flow from different teosinte taxa and the final impact on maize evolution has been difficult to measure. One hundred populations from six Zea taxa, both domesticated (maize) and wild (teosinte), including domesticated landraces from Asia, Africa, and the Americas, were genotyped with 17 SSR markers using 15 individuals per population. Overall levels of diversity were high, and populations could be distinguished based on markers. Relationships between populations followed most published reports, or can now help resolve previously conflicting reports. Gene flow into maize from different teosinte groups, and gene flow between different teosintes, was estimated. Evidence for contributions from the Balsas teosintes and from Chalco teosintes (Z. mays ssp. mexicana) to the maize gene pool was found, as well as from Chalco into ssp. mexicana race ??Durango?? and Z. mays ssp. huehuetenengensis. These contributions are almost certainly the result of post-domestication (and ongoing) exchanges. This information must give more impetus to in situ conservation of teosinte species, and use of these teosintes to continue to direct the evolution of maize, especially in response to new diseases, insect pests, and other biotic and abiotic stresses. 相似文献
999.
Trend and uncertainty analysis of simulated climate change impacts with multiple GCMs and emission scenarios 总被引:1,自引:0,他引:1
Trends and uncertainty of the climate change impacts on hydrology, soil erosion, and wheat production during 2010-2039 at El Reno in central Oklahoma, USA, were evaluated for 12 climate change scenarios projected by four GCMs (CCSR/NIES, CGCM2, CSIRO-Mk2, and HadCM3) under three emissions scenarios (A2, B2, and GGa). Compared with the present climate, overall t-tests (n = 12) show that it is almost certain that mean precipitation will decline by some 6% (>98.5% probability), daily precipitation variance increase by 12% (>99%), and maximum and minimum temperature increase by 1.46 and 1.26 °C (>99%), respectively. Compared with the present climate under the same tillage systems, it is very likely (>90%) that evapotranpiration and long-term soil water storage will decease, but runoff and soil loss will increase despite the projected declines in precipitation. There will be no significant changes in wheat grain yield.Paired t-tests show that daily precipitation variance projected under GGa is greater than those under A2 and B2 (P = 0.1), resulting in greater runoff and soil loss under GGa (P = 0.1). HadCM3 projected greater mean annual precipitation than CGCM2 and CSIRO (P = 0.1). Consequently, greater runoff, grain yield, transpiration, soil evaporation, and soil water storage were simulated for HadCM3 (P = 0.1). The inconsistency among GCMs and differential impact responses between emission scenarios underscore the necessity of using multi-GCMs and multi-emission scenarios for impact assessments. Overall results show that no-till and conservation tillage systems will need to be adopted for better soil and water conservation and environmental protection in the region during the next several decades. 相似文献
1000.