全文获取类型
收费全文 | 163篇 |
免费 | 0篇 |
专业分类
林业 | 7篇 |
农学 | 5篇 |
58篇 | |
综合类 | 34篇 |
农作物 | 4篇 |
水产渔业 | 1篇 |
畜牧兽医 | 50篇 |
园艺 | 2篇 |
植物保护 | 2篇 |
出版年
2020年 | 2篇 |
2019年 | 6篇 |
2018年 | 9篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 3篇 |
2014年 | 5篇 |
2013年 | 11篇 |
2012年 | 8篇 |
2011年 | 11篇 |
2010年 | 7篇 |
2009年 | 3篇 |
2008年 | 6篇 |
2007年 | 13篇 |
2006年 | 6篇 |
2005年 | 1篇 |
2004年 | 5篇 |
2003年 | 3篇 |
2002年 | 1篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1986年 | 2篇 |
1980年 | 1篇 |
1979年 | 7篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1974年 | 4篇 |
1973年 | 5篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1969年 | 4篇 |
1968年 | 2篇 |
1967年 | 4篇 |
1966年 | 6篇 |
排序方式: 共有163条查询结果,搜索用时 15 毫秒
1.
Amelinckx S Zhang XB Bernaerts D Zhang XF Ivanov V Nagy JB 《Science (New York, N.Y.)》1994,265(5172):635-639
The concept of a spatial-velocity hodograph is introduced to describe quantitatively the extrusion of a carbon tubule from a catalytic particle. The conditions under which a continuous tubular surface can be generated are discussed in terms of this hodograph, the shape of which determines the geometry of the initial nanotube. The model is consistent with all observed tubular shapes and explains why the formation process induces stresses that may lead to "spontaneous" plastic deformation of the tubule. This result is due to the violation of the continuity condition, that is, to the mismatch between the extrusion velocity by the catalytic particle, required to generate a continuous tubular surface, and the rate of carbon deposition. 相似文献
2.
3.
Sapundzhiev E Pupaki D Zahariev P Georgiev G Ivanov I 《Journal of veterinary medicine. A, Physiology, pathology, clinical medicine》2007,54(9):499-500
The result of the histological diagnosis from postmortal investigation of the Indian elephant (Elephas maximus) uterus structure is presented in the current study. The rare anatomical finding showed altered nodular part from the uterus wall. Through conventional and histochemical staining neoplasmatic formations were determined and diagnosis Fibroleiomyoma was established, which should not be accepted as the prime cause for the animal's death. 相似文献
4.
G. N. Fedotov G. V. Dobrovol’skii V. I. Putlyaev A. V. Garshev V. K. Ivanov E. I. Pakhomov 《Eurasian Soil Science》2006,39(7):738-747
The colloidal structures in soils were studied by scanning and transmission electron microscopy. Small-angle neutron scattering was used in the pioneering study of the colloidal soil structures and their rearrangements under the effect of different factors. It was found that colloidal particles are fixed apart in a gel matrix formed by organic molecules. The results obtained suggest that the organomineral gel is composed of soil humus occurring, at least in part, in a gel-like status and reinforced by organic and inorganic colloidal particles. In the interaction with water, the reinforced humus gel behaves as many polymers: it swells, absorbing water and increasing in volume; it shrinks under drying conditions. Different impacts on the soil affect the status of the reinforced humus gel, which results in the observed changes of the soil properties. 相似文献
5.
Belobrov V. P. Yudin S. S. Yaroslavtseva N. V. Yudina A. V. Dridiger V. K. Stukalov R. S. Kluev N. N. Zamotaev I. V. Ermolaev N. R. Ivanov A. L. Kholodov V. A. 《Eurasian Soil Science》2020,53(7):968-977
Eurasian Soil Science - This article presents the results of research on the impact of no-till technology on the natural bulk density and macro- and microaggregate composition of the topsoil... 相似文献
6.
The phenomenon of mineralization (biological mineralization) of organic matter in chernozems has been studied. A decrease
in the content of Corg with time can be considered an index of the organic matter mineralization. It is suggested that the humus horizons of modern
chernozems contain the pools of organic matter of different ages: easily decomposable organic matter, labile biologically
active humus, stable biologically active humus, and relatively inert humus. The composition and mean residence times of these
pools and their contribution to the total organic matter content have been estimated. The particular types of the biological
mineralization have been determined on the basis of the comparison between the velocities of mineralization (M) and humification
(H) processes: total unidirectional mineralization (M ≫ H), equilibrium mineralization (M ∼ H), nonequilibrium mineralization
(M> <H), and zero mineralization. The separation of subtypes is based on data on the relative rates (%) of the organic matter
mineralization. On the basis of available experimental data on chernozems buried under kurgans and in loess sediments (with
the age of up to 800 ka), the quantitative relationship of the humus content in the buried soils on their age has been found;
it has an exponential shape. During the first 100 ka after the soil burial, the soil humus content gradually (with a slowing
intensity) decreases from 100–75 to 6.5% of its content in the virgin chernozems. Then, 100–1000 ka after the soil burial,
the soil humus content remains approximately constant (6.5% of the initial level, or 0.3% of the soil mass). The rates of
mineralization have been estimated. It is shown that the elemental composition (C, H, N, O) of humic acids remains relatively
stable for a long time due to the regeneration of the chemical structure of humus (matric restoration of humus). It is suggested
that several different forms of humus related to pedogenesis should be distinguished in the biosphere. The renewable humus
in the equilibrium state with the environment is typical of the open biospheric (soil) systems. The fossil humus, whose content
decreases with time, and whose composition remains stable, is typical of the semiclosed and closed systems. With time, it
transforms into residual humus, whose content and composition remain stable. The fossilized organic matter in the fossil soils
and sediments of the past geological epochs (Mesozoic and Paleozoic) considerably differs from the renewable, fossil, and
residual humus. 相似文献
7.
Ivanov I. V. Prikhodko V. E. Zamotaev I. V. Manakhov D. V. Novenko E. Yu. Kalinin P. I. Markova L. M. Plaksina A. L. 《Eurasian Soil Science》2019,52(6):593-609
Eurasian Soil Science - The relationship between soil formation and sedimentation on the floodplain of the Utyaganka River (the Ural River basin) in the Arkaim Reserve (Chelyabinsk oblast, Southern... 相似文献
8.
Radar soundings of the subsurface of Mars 总被引:2,自引:0,他引:2
Picardi G Plaut JJ Biccari D Bombaci O Calabrese D Cartacci M Cicchetti A Clifford SM Edenhofer P Farrell WM Federico C Frigeri A Gurnett DA Hagfors T Heggy E Herique A Huff RL Ivanov AB Johnson WT Jordan RL Kirchner DL Kofman W Leuschen CJ Nielsen E Orosei R Pettinelli E Phillips RJ Plettemeier D Safaeinili A Seu R Stofan ER Vannaroni G Watters TR Zampolini E 《Science (New York, N.Y.)》2005,310(5756):1925-1928
The martian subsurface has been probed to kilometer depths by the Mars Advanced Radar for Subsurface and Ionospheric Sounding instrument aboard the Mars Express orbiter. Signals penetrate the polar layered deposits, probably imaging the base of the deposits. Data from the northern lowlands of Chryse Planitia have revealed a shallowly buried quasi-circular structure about 250 kilometers in diameter that is interpreted to be an impact basin. In addition, a planar reflector associated with the basin structure may indicate the presence of a low-loss deposit that is more than 1 kilometer thick. 相似文献
9.
10.
Bourges P Sidis Y Fong HF Regnault LP Bossy J Ivanov A Keimer B 《Science (New York, N.Y.)》2000,288(5469):1234-1237
A comprehensive inelastic neutron scattering study of magnetic excitations in the near optimally doped high-temperature superconductor YBa(2)Cu(3)O(6.85) is presented. The spin correlations in the normal state are commensurate with the crystal lattice, and the intensity is peaked around the wave vector characterizing the antiferromagnetic state of the insulating precursor, YBa(2)Cu(3)O(6). Profound modifications of the spin excitation spectrum appear abruptly below the superconducting transition temperature T(c), where a commensurate resonant mode and a set of weaker incommensurate peaks develop. The data are consistent with models that are based on an underlying two-dimensional Fermi surface, predicting a continuous, downward dispersion relation connecting the resonant mode and the incommensurate excitations. The magnetic incommensurability in the YBa(2)Cu(3)O(6+)(x) system is thus not simply related to that of another high-temperature superconductor, La(2-)(x)Sr(x)CuO(4), where incommensurate peaks persist well above T(c). The temperature-dependent incommensurability is difficult to reconcile with interpretations based on charge stripe formation in YBa(2)Cu(3)O(6+x) near optimum doping. 相似文献