全文获取类型
收费全文 | 1005篇 |
免费 | 24篇 |
国内免费 | 17篇 |
专业分类
林业 | 45篇 |
农学 | 50篇 |
基础科学 | 27篇 |
49篇 | |
综合类 | 393篇 |
农作物 | 36篇 |
水产渔业 | 26篇 |
畜牧兽医 | 341篇 |
园艺 | 39篇 |
植物保护 | 40篇 |
出版年
2022年 | 12篇 |
2021年 | 14篇 |
2020年 | 7篇 |
2019年 | 16篇 |
2018年 | 21篇 |
2017年 | 7篇 |
2016年 | 12篇 |
2015年 | 15篇 |
2014年 | 13篇 |
2013年 | 22篇 |
2012年 | 42篇 |
2011年 | 55篇 |
2010年 | 20篇 |
2009年 | 25篇 |
2008年 | 41篇 |
2007年 | 42篇 |
2006年 | 50篇 |
2005年 | 46篇 |
2004年 | 36篇 |
2003年 | 41篇 |
2002年 | 43篇 |
2001年 | 37篇 |
2000年 | 57篇 |
1999年 | 31篇 |
1998年 | 10篇 |
1997年 | 16篇 |
1996年 | 17篇 |
1995年 | 15篇 |
1994年 | 17篇 |
1993年 | 6篇 |
1992年 | 16篇 |
1991年 | 19篇 |
1990年 | 14篇 |
1989年 | 10篇 |
1988年 | 7篇 |
1987年 | 5篇 |
1986年 | 7篇 |
1985年 | 9篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 9篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1973年 | 5篇 |
1966年 | 10篇 |
1963年 | 4篇 |
1956年 | 9篇 |
1955年 | 5篇 |
1948年 | 7篇 |
排序方式: 共有1046条查询结果,搜索用时 15 毫秒
101.
推行刚性预算管理是企业增收节支、提高效益的一项有效举措。本文结合安徽省潘村湖农场预算管理实践谈几点想法: 一、推行刚性预算管理的前提——财务预测企业财务管理的实践证明,财务预算需要以财务预测的结果为根据,财务预测质量的高低直接关系到财务预算编 相似文献
102.
Ogata H Audic S Renesto-Audiffren P Fournier PE Barbe V Samson D Roux V Cossart P Weissenbach J Claverie JM Raoult D 《Science (New York, N.Y.)》2001,293(5537):2093-2098
Rickettsia conorii is an obligate intracellular bacterium that causes Mediterranean spotted fever in humans. We determined the 1,268,755-nucleotide complete genome sequence of R. conorii, containing 1374 open reading frames. This genome exhibits 804 of the 834 genes of the previously determined R. prowazekii genome plus 552 supplementary open reading frames and a 10-fold increase in the number of repetitive elements. Despite these differences, the two genomes exhibit a nearly perfect colinearity that allowed the clear identification of different stages of gene alterations with gene remnants and 37 genes split in 105 fragments, of which 59 are transcribed. A 38-kilobase sequence inversion was dated shortly after the divergence of the genus. 相似文献
103.
Bedard WD Tilden PE Wood DL Silverstein RM Brownlee RG Rodin JO 《Science (New York, N.Y.)》1969,164(3885):1284-1285
In the field, both sexes of the western pine beetle, Dendroctonus brevicomis, are attracted by the female-produced bicyclic ketal exo-brevicomin; this response is enhanced by myrcene (a constituent of the beetle's host, ponderosapine), which is not an attractant by itself. This synergism may be part of the phenomenon of the mass attack on its host. Temnochila virescens chlorodia, one of the principal insectan predators of this beetle, is attracted by exo-brevicomin alone. 相似文献
104.
105.
Despite extensive evidence for regions of human visual cortex that respond selectively to faces, few studies have considered the cortical representation of the appearance of the rest of the human body. We present a series of functional magnetic resonance imaging (fMRI) studies revealing substantial evidence for a distinct cortical region in humans that responds selectively to images of the human body, as compared with a wide range of control stimuli. This region was found in the lateral occipitotemporal cortex in all subjects tested and apparently reflects a specialized neural system for the visual perception of the human body. 相似文献
106.
A theory is presented in which much of the structure of spiral galaxies arises from a percolation phase transition that underlies the phenomenon of propagating star formation. According to this view, the appearance of spiral arms is a consequence of the differential rotation of the galaxy and the characteristic divergence of correlation lengths for continuous phase transitions. Other structural properties of spiral galaxies, such as the distribution of the gaseous components and the luminosity, arise directly from a feedback mechanism that pins the star formation rate close to the critical point of the phase transition. The approach taken in this article differs from traditional dynamical views. The argument is presented that, at least for some galaxies, morphological and other features are already fixed by general properties of phase transitions, irrespective of detailed dynamic or other considerations. 相似文献
107.
A diverse assemblage of algal stromatolites occurs in Devonian reef complexes of the Canning Basin, Western Australia. Some forms grew on fore-reef depositional slopes down to at least 45 meters below sea level and are believed to be products of deepwater nonskeletal algae. It is concluded that algal stromatolites in the stratigraphic record are not to be regarded as diagnostic evidence for deposition in very shallow water. 相似文献
108.
Nakagawa T Kitagawa H Yasuda Y Tarasov PE Nishida K Gotanda K Sawai Y;Yangtze River Civilization Program Members 《Science (New York, N.Y.)》2003,299(5607):688-691
Pollen records from the annually laminated sediment sequence in Lake Suigetsu, Japan, suggest a sequence of climate changes during the Last Termination that resembles that of the North Atlantic region but with noticeable differences in timing. An interstadial interval commenced a few centuries earlier [approximately 15,000 years before the present (yr B.P.)] than the North Atlantic GI-1 (B?lling) event. Conversely, the onset of a Younger Dryas (YD)-like cold reversal (12,300 to 11,250 yr B.P.) postdated the North Atlantic GS-1 (YD) event by a few centuries. Climate in the Far East during the Last Termination reflected solar insolation changes as much as Atlantic influences. 相似文献
109.
Biomass and carbon budget of European forests, 1971 to 1990 总被引:2,自引:0,他引:2
In severely polluted areas, such as locally in Montshegorsk in northwestern Russia, all trees have died. However, measurements from Austria, Finland, France, Germany, Sweden, and Switzerland show a general increase of forest resources. The fertilization effects of pollutants override the adverse effects at least for the time being. Biomass was built up in the 1970s and 1980s in European forests. If there has been similar development in other continents, biomass accumulation in nontropical forests can account for a large proportion of the estimated mismatch between sinks and sources of atmospheric carbon dioxide. 相似文献
110.
Bourne PE 《Science (New York, N.Y.)》2002,296(5573):1609; author reply 1609