全文获取类型
收费全文 | 425篇 |
免费 | 39篇 |
专业分类
林业 | 21篇 |
农学 | 14篇 |
107篇 | |
综合类 | 46篇 |
农作物 | 26篇 |
水产渔业 | 36篇 |
畜牧兽医 | 179篇 |
园艺 | 3篇 |
植物保护 | 32篇 |
出版年
2023年 | 6篇 |
2021年 | 4篇 |
2020年 | 13篇 |
2019年 | 9篇 |
2018年 | 15篇 |
2017年 | 10篇 |
2016年 | 12篇 |
2015年 | 11篇 |
2014年 | 13篇 |
2013年 | 18篇 |
2012年 | 32篇 |
2011年 | 39篇 |
2010年 | 17篇 |
2009年 | 16篇 |
2008年 | 19篇 |
2007年 | 20篇 |
2006年 | 15篇 |
2005年 | 21篇 |
2004年 | 14篇 |
2003年 | 14篇 |
2002年 | 8篇 |
2001年 | 10篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 8篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1990年 | 5篇 |
1989年 | 8篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1975年 | 3篇 |
1973年 | 2篇 |
1965年 | 3篇 |
1964年 | 5篇 |
1963年 | 4篇 |
排序方式: 共有464条查询结果,搜索用时 15 毫秒
31.
Travel and Activity Choices for Transit Travelers at Terminals with Dynamic Information Provision 下载免费PDF全文
This study explores the impacts of providing dynamic information on travelers' behavior and the induced demand for terminal‐surrounding activities. A nested logit model was used to identify the important factors, and a questionnaire was designed to explore the preference of travelers regarding activities and travel choices. Adopting dynamic information was found to have a significant influence on travel decisions. The results show that an increased duration of activity participation may accompany an alteration of departure time or mode choice. The results also show that the use of dynamic information for travelers is related to induced activity participation and travelers' socioeconomic characteristics. The content of the dynamic information should be designed in accordance with the preference of travelers to encourage travelers participating in terminal‐surrounding activities. 相似文献
32.
Chang Chien SW Wang MC Hsu JH Seshaiah K 《Journal of agricultural and food chemistry》2006,54(18):6790-6799
The qualitative and quantitative characteristics of soil organic carbon (SOC) and related humic acids (HAs) extracted from the soils of field plots were investigated after 8 years of annual paddy (Oryza sativa L.) and upland maize (Zea mays L.) rotation with various fertilizations. Seven fertilization treatments were selected: Ck (no inputs); Chem (chemical fertilizer of NPK); Comp (swine compost); Comp + 33% of Chem N rate; Comp + 67% of Chem N rate; GM (legume green manure) + 33% of Chem N rate; and peat + 33% of Chem N rate. Organic and inorganic nitrogen inputs of six treatments were equivalent with respect of nitrogen content, but Comp, GM, and peat treatments were complemented with various amounts of inorganic N. After harvest of the eighth paddy crop, surface soil samples collected from the plots were subjected to soil characterizations and extraction of humic substances, which were used for chemical, spectroscopic (FTIR, 13C NMR, ESR, X-ray diffractometry), delta13C, and 14C dating analyses. The yields of HAs extracted from the seven treatments were significantly different. Treatment containing persistent organic compound such as the peat + 33% N treatment increased the humification process in topsoils and produced higher yield of HA. Spectroscopic analyses revealed that fertilization treatments changed the functional groups, alkyl C, crystalline characteristics, and delta13C ratios of HAs and turnover rate of SOC considerably. The SOC of the peat + 33% N treatment had the highest mean residence time of 3100 years. Various fertilizer treatments are correlated with turnover rate of SOC and related HAs, which are associated with concerned carbon sequestration as well as mitigation of CO2 emission in the soil environment. 相似文献
33.
34.
根据关中地区水文气象条件和棉花需水规律的研究资料分析,说明关中的气候和土壤资源完全能满足旱地棉花丰产所要求的条件。丰产示范结果进一步证明关中旱地棉田是能够获得高产和稳产的,其关键在于掌握自然特点,运用旱地丰产栽培技术,保证全苗和促进早期发育。 相似文献
35.
Summary Inheritance of yield and its component (number of ears per plant, number of spikelets per ear, number of kernels per ear, 1000-kernel weight), together with the inheritance of morphological characters (flag leaf length, flag leaf breadth, peduncle length, extrusion length and leaf sheath length) and anthesis date was studied in a 5-parent diallel cross of spring wheat varieties. The diallel analysis of gene actions indicated that a large part of the total genetic variation observed for all the characters studied was in the form of additive genetic effects. The degree of dominance was also determined for each character. Number of ears per plant showed most overdominance, followed by leaf sheath length. Full or nearly full dominance was found for anthesis date, flag leaf length and yield per plant. Other characters showed partial dominance. Correlation coefficients showed that yield per plant, as well as being correlated with the yield components, was also assiciated with flag leaf breadth and leaf sheath length. There was no evidence of genetic barriers to the combining of ideal characters among the varieties of different origin. 相似文献
36.
Roginsky V Barsukova T Hsu CF Kilmartin PA 《Journal of agricultural and food chemistry》2003,51(19):5798-5802
A series of eight green, eight oolong, and 17 black teas have been analyzed for polyphenol content by absorbance at 272 nm and cyclic voltammetry response at an inert carbon electrode, a new method developed to provide a rapid measure of easily oxidizable polyphenols in beverages. The chain-breaking antioxidant activity of the teas has also been determined during the chain oxidation of methyl linoleate in a pH 7.4 micellar solution, for which realistic kinetic parameters have been derived. While higher mean values were obtained for green teas than for oolong and black teas, the differences were not large, and the spread of values within each type was considerable. The absorbance at 272 nm correlated well with the cyclic voltammetry response only for green teas and black teas taken on their own. The cyclic voltammetry measure and the antioxidant activity correlated well only for the green teas, where the polyphenol content is dominated by epigallocatechin gallate. 相似文献
37.
38.
Films of silicon dioxide (SiO2) were deposited at room temperature by means of catalyzed binary reaction sequence chemistry. The binary reaction SiCl4 + 2H2O --> SiO2 + 4HCl was separated into SiCl4 and H2O half-reactions, and the half-reactions were then performed in an ABAB ellipsis sequence and catalyzed with pyridine. The pyridine catalyst lowered the deposition temperature from >600 to 300 kelvin and reduced the reactant flux required for complete reactions from approximately 10(9) to approximately 10(4) Langmuirs. Growth rates of approximately 2.1 angstroms per AB reaction cycle were obtained at room temperature for reactant pressures of 15 millitorr and 60-second exposure times with 200 millitorr of pyridine. This catalytic technique may be general and should facilitate the chemical vapor deposition of other oxide and nitride materials. 相似文献
39.
D H Hsu R de Waal Malefyt D F Fiorentino M N Dang P Vieira J de Vries H Spits T R Mosmann K W Moore 《Science (New York, N.Y.)》1990,250(4982):830-832
Cytokine synthesis inhibitory factor (CSIF; interleukin-10), a product of mouse TH2 T cell clones that inhibits synthesis of cytokines by mouse TH1 T cell clones, exhibits extensive sequence similarity to an uncharacterized open reading frame in the Epstein-Barr virus BCRF1. Recombinant BCRF1 protein mimics the activity of interleukin-10, suggesting that BCRF1 may have a role in the interaction of the virus with the host's immune system. 相似文献
40.