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981.
The CLAVATA1 (CLV1) and CLAVATA3 (CLV3) proteins form a potential receptor and ligand pair that regulates the balance between cell proliferation and differentiation at the shoot meristem of Arabidopsis. CLV1 encodes a receptor-kinase, and CLV3 encodes a predicted small, secreted polypeptide. We demonstrate that the CLV3 and CLV1 proteins coimmunoprecipitate in vivo, that yeast cells expressing CLV1 and CLV2 bind to CLV3 from plant extracts, and that binding requires CLV1 kinase activity. CLV3 only associates with the presumed active CLV1 protein complex in vivo. More than 75% of CLV3 in cauliflower extracts is bound with CLV1, consistent with hypotheses of ligand sequestration. Soluble CLV3 was found in an approximately 25-kilodalton multimeric complex. 相似文献
982.
Summary As organic farming refrains from high and chemical inputs it needs varieties better adapted to organic conditions to improve
the yield stability and quality of crops. In order to make genebank accessions more accessible for the utilisation in organic
breeding programmes, a participatory research project with farmers was carried out in 2002 and 2003. From the Dutch genebank
collection 37 onion accessions, divided into five different groups (according to their market use), were selected and planted
at a commercial organic farm. Farmer participation in characterisation and evaluation of the material resulted in including
additional plant traits for genebank characterisation as well as new selection criteria for breeding. It also provided researchers
insight into how organic farmers evaluate and value certain plant traits. Variation for important properties was found within
and between the five groups. To establish base populations, the farmers, in collaboration with the researchers, selected the
best genotypes within the five groups of onion accessions. The new base populations may be exploited in order to achieve better-adapted
material for organic farming systems. 相似文献
983.
Amplification of c-erbB-2 and aggressive human breast tumors? 总被引:11,自引:0,他引:11
984.
985.
Squyres SW Arvidson RE Bell JF Brückner J Cabrol NA Calvin W Carr MH Christensen PR Clark BC Crumpler L Marais DJ d'Uston C Economou T Farmer J Farrand W Folkner W Golombek M Gorevan S Grant JA Greeley R Grotzinger J Haskin L Herkenhoff KE Hviid S Johnson J Klingelhöfer G Knoll AH Landis G Lemmon M Li R Madsen MB Malin MC McLennan SM McSween HY Ming DW Moersch J Morris RV Parker T Rice JW Richter L Rieder R Sims M Smith M Smith P Soderblom LA Sullivan R Wänke H Wdowiak T Wolff M Yen A 《Science (New York, N.Y.)》2004,306(5702):1698-1703
The Mars Exploration Rover Opportunity has investigated the landing site in Eagle crater and the nearby plains within Meridiani Planum. The soils consist of fine-grained basaltic sand and a surface lag of hematite-rich spherules, spherule fragments, and other granules. Wind ripples are common. Underlying the thin soil layer, and exposed within small impact craters and troughs, are flat-lying sedimentary rocks. These rocks are finely laminated, are rich in sulfur, and contain abundant sulfate salts. Small-scale cross-lamination in some locations provides evidence for deposition in flowing liquid water. We interpret the rocks to be a mixture of chemical and siliciclastic sediments formed by episodic inundation by shallow surface water, followed by evaporation, exposure, and desiccation. Hematite-rich spherules are embedded in the rock and eroding from them. We interpret these spherules to be concretions formed by postdepositional diagenesis, again involving liquid water. 相似文献
986.
Gellert R Rieder R Anderson RC Brückner J Clark BC Dreibus G Economou T Klingelhöfer G Lugmair GW Ming DW Squyres SW D'Uston C Wänke H Yen A Zipfel J 《Science (New York, N.Y.)》2004,305(5685):829-832
The alpha particle x-ray spectrometer on the Spirit rover determined major and minor elements of soils and rocks in Gusev crater in order to unravel the crustal evolution of planet Mars. The composition of soils is similar to those at previous landing sites, as a result of global mixing and distribution by dust storms. Rocks (fresh surfaces exposed by the rock abrasion tool) resemble volcanic rocks of primitive basaltic composition with low intrinsic potassium contents. High abundance of bromine (up to 170 parts per million) in rocks may indicate the alteration of surfaces formed during a past period of aqueous activity in Gusev crater. 相似文献
987.
Squyres SW Arvidson RE Ruff S Gellert R Morris RV Ming DW Crumpler L Farmer JD Marais DJ Yen A McLennan SM Calvin W Bell JF Clark BC Wang A McCoy TJ Schmidt ME de Souza PA 《Science (New York, N.Y.)》2008,320(5879):1063-1067
Mineral deposits on the martian surface can elucidate ancient environmental conditions on the planet. Opaline silica deposits (as much as 91 weight percent SiO2) have been found in association with volcanic materials by the Mars rover Spirit. The deposits are present both as light-toned soils and as bedrock. We interpret these materials to have formed under hydrothermal conditions and therefore to be strong indicators of a former aqueous environment. This discovery is important for understanding the past habitability of Mars because hydrothermal environments on Earth support thriving microbial ecosystems. 相似文献
988.
Levine JA Lanningham-Foster LM McCrady SK Krizan AC Olson LR Kane PH Jensen MD Clark MM 《Science (New York, N.Y.)》2005,307(5709):584-586
Obesity occurs when energy intake exceeds energy expenditure. Humans expend energy through purposeful exercise and through changes in posture and movement that are associated with the routines of daily life [called nonexercise activity thermogenesis (NEAT)]. To examine NEAT's role in obesity, we recruited 10 lean and 10 mildly obese sedentary volunteers and measured their body postures and movements every half-second for 10 days. Obese individuals were seated, on average, 2 hours longer per day than lean individuals. Posture allocation did not change when the obese individuals lost weight or when lean individuals gained weight, suggesting that it is biologically determined. If obese individuals adopted the NEAT-enhanced behaviors of their lean counterparts, they might expend an additional 350 calories (kcal) per day. 相似文献
989.
Weber ME Clark PU Ricken W Mitrovica JX Hostetler SW Kuhn G 《Science (New York, N.Y.)》2011,334(6060):1265-1269
The timing of the last maximum extent of the Antarctic ice sheets relative to those in the Northern Hemisphere remains poorly understood. We develop a chronology for the Weddell Sea sector of the East Antarctic Ice Sheet that, combined with ages from other Antarctic ice-sheet sectors, indicates that the advance to and retreat from their maximum extent was within dating uncertainties synchronous with most sectors of Northern Hemisphere ice sheets. Surface climate forcing of Antarctic mass balance would probably cause an opposite response, whereby a warming climate would increase accumulation but not surface melting. Our new data support teleconnections involving sea-level forcing from Northern Hemisphere ice sheets and changes in North Atlantic deep-water formation and attendant heat flux to Antarctic grounding lines to synchronize the hemispheric ice sheets. 相似文献
990.
McSween HY Arvidson RE Bell JF Blaney D Cabrol NA Christensen PR Clark BC Crisp JA Crumpler LS Des Marais DJ Farmer JD Gellert R Ghosh A Gorevan S Graff T Grant J Haskin LA Herkenhoff KE Johnson JR Jolliff BL Klingelhoefer G Knudson AT McLennan S Milam KA Moersch JE Morris RV Rieder R Ruff SW De Souza PA Squyres SW Wänke H Wang A Wyatt MB Yen A Zipfel J 《Science (New York, N.Y.)》2004,305(5685):842-845
The Spirit landing site in Gusev Crater on Mars contains dark, fine-grained, vesicular rocks interpreted as lavas. Pancam and Mini-Thermal Emission Spectrometer (Mini-TES) spectra suggest that all of these rocks are similar but have variable coatings and dust mantles. Magnified images of brushed and abraded rock surfaces show alteration rinds and veins. Rock interiors contain =25% megacrysts. Chemical analyses of rocks by the Alpha Particle X-ray Spectrometer are consistent with picritic basalts, containing normative olivine, pyroxenes, plagioclase, and accessory FeTi oxides. M?ssbauer, Pancam, and Mini-TES spectra confirm the presence of olivine, magnetite, and probably pyroxene. These basalts extend the known range of rock compositions composing the martian crust. 相似文献