全文获取类型
收费全文 | 1152篇 |
免费 | 72篇 |
国内免费 | 3篇 |
专业分类
林业 | 56篇 |
农学 | 24篇 |
基础科学 | 5篇 |
130篇 | |
综合类 | 191篇 |
农作物 | 39篇 |
水产渔业 | 157篇 |
畜牧兽医 | 573篇 |
园艺 | 26篇 |
植物保护 | 26篇 |
出版年
2023年 | 6篇 |
2022年 | 3篇 |
2021年 | 27篇 |
2020年 | 23篇 |
2019年 | 32篇 |
2018年 | 27篇 |
2017年 | 33篇 |
2016年 | 31篇 |
2015年 | 22篇 |
2014年 | 25篇 |
2013年 | 51篇 |
2012年 | 67篇 |
2011年 | 73篇 |
2010年 | 46篇 |
2009年 | 38篇 |
2008年 | 59篇 |
2007年 | 65篇 |
2006年 | 81篇 |
2005年 | 59篇 |
2004年 | 59篇 |
2003年 | 55篇 |
2002年 | 63篇 |
2001年 | 26篇 |
2000年 | 12篇 |
1999年 | 13篇 |
1998年 | 5篇 |
1997年 | 7篇 |
1996年 | 10篇 |
1995年 | 10篇 |
1994年 | 8篇 |
1993年 | 12篇 |
1992年 | 13篇 |
1991年 | 11篇 |
1990年 | 11篇 |
1989年 | 7篇 |
1988年 | 11篇 |
1987年 | 10篇 |
1986年 | 10篇 |
1985年 | 10篇 |
1984年 | 7篇 |
1983年 | 9篇 |
1982年 | 3篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1976年 | 3篇 |
1972年 | 6篇 |
1968年 | 4篇 |
1967年 | 4篇 |
1936年 | 3篇 |
1902年 | 2篇 |
排序方式: 共有1227条查询结果,搜索用时 31 毫秒
951.
Morris WE Venzano AJ Craig MI Diodati JA Funes D Elizondo A Mercado E Capellino F Delgado F Blanco-Viera J 《The Canadian veterinary journal. La revue veterinaire canadienne》2010,51(8):877-880
This study reports 3 cases of spontaneous papillomavirus infection in 1-week-old calves. Thickening of the omasum and abomasum wall, with acute inflammation, necrosis, ulceration, and neoplastic changes were seen in 1 calf. In the other 2, small papillomas were observed in the omasal mucosa, exhibiting proliferation of the parakeratinized epithelium. Papillomavirus antigens were detected by immunohistochemistry and virus-like particles were seen through electron microscopy. 相似文献
952.
953.
Tricia M. Bisby Patricia J. Holman George A. Pitoc Rebecca A. Packer Craig A. Thompson Rose E. Raskin 《Veterinary clinical pathology / American Society for Veterinary Clinical Pathology》2010,39(1):105-112
Abstract: A 5‐month‐old male neutered domestic shorthair cat was evaluated for spinal pain, ataxia, and anisocoria. Neuroanatomic localization indicated diffuse or multifocal central nervous system disease. On cerebrospinal fluid analysis, neutrophilic pleocytosis and intracellular protozoal merozoites were observed. The merozoites were oval, 2–4 μm in width and 4–6 μm in length, and had linear arrays of nuclear material concentrated at one pole. Serum was positive for Sarcocystis sp. antibodies and negative for Toxoplasma gondii antibodies. The organism was determined to be either Sarcocystis neurona or Sarcocystis dasypi based on sequence analysis of the internal transcribed spacer 1 ribosomal RNA genomic region. Clinical disease resolved following treatment with 3 different protocols for protozoal infection. This case is the first to demonstrate the antemortem diagnosis and survival of a domestic cat with Sarcocystis sp.‐associated encephalomyelitis. Clinicians and cytopathologists should include Sarcocystis sp. as a differential for feline inflammatory central nervous system disease characterized by neutrophilic pleocytosis. 相似文献
954.
955.
Waldo GL Ricks TK Hicks SN Cheever ML Kawano T Tsuboi K Wang X Montell C Kozasa T Sondek J Harden TK 《Science (New York, N.Y.)》2010,330(6006):974-980
Transmembrane signals initiated by a broad range of extracellular stimuli converge on nodes that regulate phospholipase C (PLC)-dependent inositol lipid hydrolysis for signal propagation. We describe how heterotrimeric guanine nucleotide-binding proteins (G proteins) activate PLC-βs and in turn are deactivated by these downstream effectors. The 2.7-angstrom structure of PLC-β3 bound to activated Gα(q) reveals a conserved module found within PLC-βs and other effectors optimized for rapid engagement of activated G proteins. The active site of PLC-β3 in the complex is occluded by an intramolecular plug that is likely removed upon G protein-dependent anchoring and orientation of the lipase at membrane surfaces. A second domain of PLC-β3 subsequently accelerates guanosine triphosphate hydrolysis by Gα(q), causing the complex to dissociate and terminate signal propagation. Mutations within this domain dramatically delay signal termination in vitro and in vivo. Consequently, this work suggests a dynamic catch-and-release mechanism used to sharpen spatiotemporal signals mediated by diverse sensory inputs. 相似文献
956.
Since bycatch reduction devices (BRDs) were first tested in Australian penaeid-trawl fisheries almost 20 years ago, there have been ongoing refinements to a discrete range of legislated designs; mostly in response to dynamic fishery-specific operational requirements. This study assesses the relative utility of the latest versions of two generic BRDs that have evolved/devolved in an estuarine fishery. Compared with a codend containing no BRD, a simplified Nordmøre-grid and radial escape section significantly reduced the total weight of bycatch by 74 and 36%, respectively. Catches of the targeted school prawns (Metapenaeus macleayi) were also reduced by 4 and 11%, respectively, although, at least for the Nordmøre-grid, these losses were apparently offset by the practicality of the revised design in terms of a simpler and cheaper construction. The presence of large quantities of displaced submerged plants (e.g. Egeria densa and Hydrilla verticillata) on the trawl grounds at certain times (which preclude using the Nordmøre-grid) may similarly compensate for the reduced efficiency of the radial escape section. In addition to quantifying the performance of the revised BRDs, the results provide direction for their future refinement in this and other similar fisheries. 相似文献
957.
Raphael Santos Craig A. Radford Joseph Poupin Christophe Brié Suzanne C. Mills René Galzin David Lecchini 《Fisheries Science》2012,78(1):75-80
The post-larval supply of two crustacean taxa (Brachyura and Stomatopoda) was monitored using one crest net over three lunar
months at Rangiroa Atoll, French Polynesia. We captured a total of 37,068 brachyuran and 12,697 stomatopod post-larvae during
the study. Post-larval supply was higher during the warm season (February–April) than during the cold season (June–July) for
both Brachyura (warm season: 85% of total post-larval supply) and Stomatopoda (warm season: 92%). Moreover, the pulse of the
brachyuran post-larval supply occurred predominantly around the last quarter, while the pulse of stomatopods occurred predominantly
around the new moon. However, for both taxa, the post-larval supply was lowest around the full moon and the first quarter.
Overall, our monitoring highlighted that the post-larval supply of Brachyura and Stomatopoda was modulated by seasons and
lunar phases at Rangiroa. 相似文献
958.
Craig F. Morris Arthur D. Bettge Marvin J. Pitts G. E. King Kameron Pecka Patrick J. McCluskey 《Cereal Chemistry》2008,85(3):359-365
The three major classes of endosperm texture (grain hardness) of soft and hard common, and durum wheat represent and define one of the leading determinants of the milling and end‐use quality of wheat. Although these three genetic classes are directly related to the Hardness locus and puroindoline gene function, much less is known about the kernel‐to‐kernel variation within pure varietal grain lots. Measurement of this variation is of considerable interest. The objective of this research was to compare kernel texture as determined by compression failure testing using endosperm bricks with results of whole‐kernel hardness obtained with the Single Kernel Characterization System 4100 hardness index (SKCS HI). In general terms, the variation obtained with the SKCS HI was of similar magnitude to that obtained using failure strain and failure energy of endosperm brick compression. Objective comparisons included frequency distribution plots, normalized frequency distribution plots, ANOVA model R2, and coefficients of variation. Results indicated that compression testing and SKCS HI similarly captured the main features of texture classes but also reflected notable differences in texture properties among and within soft, hard, and durum classes. Neither brick compression testing nor the SKCS HI may be reasonably expected to correctly classify all individual kernels as to genetic texture class. However, modest improvements in correct classification rate or, more importantly, better classification related to end‐use quality may still be achievable. 相似文献
959.
Soil water content on drip irrigated cotton: comparison of measured and simulated values obtained with the Hydrus 2-D model 总被引:2,自引:1,他引:1
Vinicius Bof Bufon Robert J. Lascano Craig Bednarz Jill D. Booker Dennis C. Gitz 《Irrigation Science》2012,30(4):259-273
Crop irrigation with subsurface drip (SDI) is increasing in the semiarid Texas High Plains (THP). Information on drip-tubing positioning, irrigation strategies, and wetted soil area is needed to increase rainwater effectiveness when well capacities are inadequate to meet full irrigation requirements. Time and resources necessary to test SDI strategies for different conditions through field experimentation is too large. However, a mechanistic model such as Hydrus-2D can quantify the effect of different installation geometries and irrigation strategies. Our objective was to experimentally validate the Hydrus-2D in an Amarillo soil in THP so that the model can be used to evaluate different irrigation frequency and timing strategies for SDI cotton. Results showed that Hydrus-2D simulated volumetric soil water content within ±3% of measured values, and simulation bias represented the smaller portion of the simulation error, indicating that the model can be used to evaluate irrigation strategies. 相似文献
960.
The authors have studied microstructure evolution during thermally induced phase separation in a class of binary supported lipid bilayers using a quantitative application of imaging ellipsometry. The bilayers consist of binary mixtures consisting of a higher melting glycosphingolipid, galactosylceramide (GalCer), which resides primarily in the outer leaflet, and a lower melting, unsaturated phospholipid, 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC). Three different bilayer compositions of GalCer/DLPC mixtures at 35:65, 20:80, and 10:90 molar ratios were cooled at controlled rates from their high-temperature homogeneous phase to temperatures corresponding to their phase coexistence regime and imaged in real time using imaging ellipsometry. During the thermotropic course of GalCer gelation, we find that two distinct types of morphological features modulate. First, the formation and growth of chain and fractal-like defects ascribed to the net change in molecular areas during the phase transition. The formation of these defects is consistent with the expected contraction in the molecular area during the liquid crystalline to gel-phase transition. Second, the nucleation and growth of irregularly shaped gel-phase domains, which exhibit either line-tension dominated compact shape or dendritic domains with extended interfaces. Quantifying domain morphology within the fractal framework reveals a close correspondence, and the quantization of the transition width confirms previous estimates of reduced phase transition cooperativity in supported bilayers. A comparison of domain properties indicates that thermal history, bilayer composition, and cooling rate all influence microstructure details including shapes, sizes, and distributions of domains and defects: At lower cooling rates and lower GalCer fractions compact domains form and at higher GalCer fractions (or at higher cooling rates) dendritic domains are evident. This transition of domain morphology from compact shapes to dendritic shapes at higher cooling rates and higher relative fractions of GalCer suggests kinetic control of shape equilibration in these phospho- and glycolipid mixtures. 相似文献