全文获取类型
| 收费全文 | 14329篇 |
| 免费 | 3929篇 |
| 国内免费 | 182篇 |
专业分类
| 林业 | 1346篇 |
| 农学 | 1742篇 |
| 基础科学 | 1169篇 |
| 2544篇 | |
| 综合类 | 4935篇 |
| 农作物 | 763篇 |
| 水产渔业 | 861篇 |
| 畜牧兽医 | 3189篇 |
| 园艺 | 705篇 |
| 植物保护 | 1186篇 |
出版年
| 2025年 | 129篇 |
| 2024年 | 312篇 |
| 2023年 | 384篇 |
| 2022年 | 594篇 |
| 2021年 | 664篇 |
| 2020年 | 639篇 |
| 2019年 | 635篇 |
| 2018年 | 566篇 |
| 2017年 | 741篇 |
| 2016年 | 665篇 |
| 2015年 | 739篇 |
| 2014年 | 791篇 |
| 2013年 | 894篇 |
| 2012年 | 1080篇 |
| 2011年 | 1153篇 |
| 2010年 | 1009篇 |
| 2009年 | 872篇 |
| 2008年 | 882篇 |
| 2007年 | 761篇 |
| 2006年 | 687篇 |
| 2005年 | 572篇 |
| 2004年 | 340篇 |
| 2003年 | 307篇 |
| 2002年 | 309篇 |
| 2001年 | 372篇 |
| 2000年 | 370篇 |
| 1999年 | 283篇 |
| 1998年 | 202篇 |
| 1997年 | 166篇 |
| 1996年 | 156篇 |
| 1995年 | 139篇 |
| 1994年 | 146篇 |
| 1993年 | 109篇 |
| 1992年 | 130篇 |
| 1991年 | 106篇 |
| 1990年 | 121篇 |
| 1989年 | 82篇 |
| 1988年 | 67篇 |
| 1987年 | 42篇 |
| 1986年 | 35篇 |
| 1985年 | 19篇 |
| 1984年 | 14篇 |
| 1983年 | 11篇 |
| 1982年 | 9篇 |
| 1981年 | 14篇 |
| 1980年 | 6篇 |
| 1979年 | 12篇 |
| 1966年 | 7篇 |
| 1963年 | 6篇 |
| 1892年 | 7篇 |
排序方式： 共有10000条查询结果，搜索用时 15 毫秒
31.
根据改性沥青的作用机理理论,通过室内试验确定合适的橡胶沥青制备方法,对由不同制备工艺的橡胶沥青的针入度、软化点、延度、黏度及弹性恢复率进行分析比较,结果表明：反应温度低于180℃时,低温变形能力及高温稳定性差,过高的温度导致橡胶沥青的脱硫及老化,反而达不到预期的结果,胶粉与沥青反应的最佳温度为190℃;胶粉不宜小于30目,胶粉粒径大,橡胶沥青低温性能差,粒径越小,黏度越高,低温变形能力越好。价格随胶粉细度增大而增大,经过经济性分析,胶粉的合适目数为60目;最佳掺量为24%（外掺）,掺量高不仅提高造价,而且降低沥青的施工性能。 相似文献
32.
The wheat grain is surrounded by a multilayered system composed of different tissues differing in their composition and mechanical properties. Up to now, these properties have been determined using classical tensile tests. However no methodology exists to evaluate the inter-tissular adherence. With this purpose, a micromechanical device adapted to wheat tissue (5 tissues with thickness varying from 2 to 55 μm) was built in order to investigate an interface of industrial interest for wheat processing (between the aleurone layer and the nucellar epidermis). Taking into account the complexity of the peel force measured, the stored elastic energy on the peel arms was estimated using tensile tests of peel arms and was found to approximate 0.15% of the total peel force at low peel rates. The energy dissipated was investigated as a function of peel test parameters (angle, curvature radius and rate), and seems to have a minimal influence when low peel rates were applied (20 μm s−1). The peel test was finally used to investigate the adherence distribution around the wheat grain using samples dissected in different directions. The bottom of the grain was the least adherent region, whereas the top of the grain towards the brush was the most adherent region. Even though the interpretation of the peel force was complex, this technique could be appropriate to evaluate the adherence within natural biological tissues. 相似文献
33.
The marine carotenoid fucoxanthin can be found in marine brown seaweeds, the macroalgae, and diatoms, the microalgae, and has remarkable biological properties. Numerous studies have shown that fucoxanthin has considerable potential and promising applications in human health. In this article, we review the current available scientific literature regarding the metabolism, safety, and bioactivities of fucoxanthin, including its antioxidant, anti-inflammatory, anticancer, anti-obese, antidiabetic, antiangiogenic and antimalarial activities, and its protective effects on the liver, blood vessels of the brain, bones, skin, and eyes. Although some studies have shown the bioavailability of fucoxanthin in brown seaweeds to be low in humans, many studies have suggested that a dietary combination of fucoxanthin and edible oil or lipid could increase the absorption rate of fucoxanthin, and thus it might be a promising marine drug. 相似文献
34.
35.
36.
37.
Bo Qi Zhengkai Yuan Shaorong Lu Kuo Liu Shanrong Li Liping Yang Jinhong Yu 《Fibers and Polymers》2014,15(2):326-333
The graphene oxide (GO) sheets are chemically grafted with γ-etheroxygentrimethoxysilane (KH560) and liquid crystalline epoxy (LCE) is synthesized from 4,4′-bis(2-hydroxyhexoxy)biphenyl (BP2) and epichlorohydrin before being incorporated into epoxy matrix. Then we present a novel approach to the fabrication of advanced polymer composites from epoxy matrix by incorporation of two modifiers, which are grafted GO (g-GO) and LCE. The mechanical properties of epoxy composites are greatly improved by incorporating LCE/g-GO hybrid fillers. For instance, the addition of 3 wt% hybrid filler (2 wt% g-GO and 1 wt% LCE) into the epoxy matrix resulted in the increases in impact strength by 132.6 %, tensile strength by 27.6 % and flexural strength by 37.5 %. Moreover, LCE/g-GO hybrid fillers are effective to increase thermal decomposition temperature, glass transition temperature, and storage modulus by strong affinity between the fillers and epoxy matrix. 相似文献
38.
Compared with hexaploid wheat, tetraploid durum is more susceptible to Fusarium crown rot (FCR) infection. The feasibility of enhancing FCR resistance in durum wheat by introgressing chromosome segments of hexaploid wheat was investigated by generating and analysing a backcross population derived from a susceptible durum wheat variety ??Bellaroi?? (recurrent parent) and a resistant hexaploid genotype ??CSCR6?? (donor parent). Together with a few scattered segments on various chromosomes, segments of a large section of the donor chromosome 6B showed a significant effect in enhancing FCR resistance in the durum background. However, a known major locus on the donor 3BL conferring high level of resistance to FCR in hexaploid wheat failed to provide any improvement in resistance than that of the genome average once it was introduced into the durum wheat. A small proportion of the backcross population gave similar resistance to the bread wheat variety ??Kennedy??, a level of FCR resistance acceptable to durum growers. These lines share a 4B segment from the hexaploid donor, although the segment was not among those with the largest individual effect across the whole population. These results show that it is feasible to improve FCR resistance of durum wheat by exploiting hexaploid chromosome segments, although resistance loci of the hexaploid wheat may not function properly in durum backgrounds. 相似文献
39.
40.