首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2282篇
  免费   127篇
  国内免费   1篇
林业   116篇
农学   134篇
基础科学   3篇
  411篇
综合类   150篇
农作物   296篇
水产渔业   201篇
畜牧兽医   934篇
园艺   35篇
植物保护   130篇
  2023年   14篇
  2022年   31篇
  2021年   58篇
  2020年   36篇
  2019年   44篇
  2018年   59篇
  2017年   65篇
  2016年   64篇
  2015年   67篇
  2014年   99篇
  2013年   136篇
  2012年   176篇
  2011年   186篇
  2010年   117篇
  2009年   127篇
  2008年   152篇
  2007年   144篇
  2006年   156篇
  2005年   89篇
  2004年   91篇
  2003年   91篇
  2002年   86篇
  2001年   70篇
  2000年   40篇
  1999年   26篇
  1998年   13篇
  1997年   4篇
  1996年   4篇
  1995年   7篇
  1994年   5篇
  1993年   5篇
  1992年   16篇
  1991年   5篇
  1990年   16篇
  1989年   13篇
  1988年   8篇
  1987年   7篇
  1985年   9篇
  1984年   7篇
  1981年   3篇
  1978年   4篇
  1977年   4篇
  1976年   3篇
  1975年   3篇
  1974年   7篇
  1973年   10篇
  1971年   3篇
  1966年   4篇
  1949年   2篇
  1929年   2篇
排序方式: 共有2410条查询结果,搜索用时 93 毫秒
991.
An acidic polysaccharide of Panax ginseng (APG), so called ginsan is known to have important immunomodulatory activities. It was recently reported that APG has radioprotective effects in mice but the detailed mechanism was not fully elucidated. This study examined the effects of APG on bone marrow cells (BMs). The phenotypical and functional changes in APG-treated BMs after gamma radiation were studied. The benefit of APG on BMs damaged by gamma radiation was determined by measuring the cell viability. Using 2 different assays, a pretreatment with APG significantly increased the viability of BMs against gamma radiation. APG-treated BMs had a significantly higher amount of IL-12, which is a major cytokine for immune responses, compared with the medium-treated BMs. The expression of MHC class II molecules of APG-treated BMs was also increased, and APG-treated BMs showed significantly higher levels of allogeneic CD4+ T lymphocyte proliferation. Furthermore, APG-treated mice had a larger number of BMs after gamma radiation than the control mice, and the BMs of APG-treated mice were successfully cultured into dendritic cells, which are the representative antigen-presenting cells. Overall, this study shows that APG alters the phenotype of BMs, increases the viability and alloreactivity of BMs after gamma radiation both in vitro and in vivo. Therefore, APG may be a good candidate radioprotective agent for BMs.  相似文献   
992.
993.
虫生真菌蝉拟青霉及其角变株的比较研究   总被引:2,自引:0,他引:2  
蝉拟青霉GZUIFR-JZD3菌株在沙氏培养基上可产生孢子型(JZD3-C)和菌丝型(JZD3-M)两类不同的角变。为了进一步研究其差异,笔者比较了两个角变株与原始菌株(JZD3)在不同培养基上的生长及产孢量。研究了其对甘蓝蚜的致病性并测定了它们的胞外多糖、蛋白酶、蛋白质、SOD和POD的含量。结果表明:3个菌株形态差异较大,在多数培养基上,JZD3生长最快,产孢量最大;胞外多糖、SOD、POD含量以及对蚜虫致病率也是JZD3菌株最佳;而蛋白酶和蛋白质含量则分别是JZD3-C和JZD3-M较高。  相似文献   
994.
995.
Artina pectinata (Comb pen shell, CPS) is a high-protein source that contains a variety of essential amino acids. Subcritical water hydrolysis (SWH) was used to recover amino acids from the posterior adductor muscle (PAM), anterior adductor muscle (ADM), and mantle. The temperatures ranged from 120 °C to 200 °C, and the pressure and time of hydrolysis were 3 MPa and 30 min, respectively. Further characterization of the hydrolysates was performed to ascertain amino acid profiles and biofunctional properties. The hydrolysates contained more free amino acids than the untreated samples. Antioxidant activity of treated samples increased as SW temperatures increased. At 200 °C, those inhibiting ACE had a maximum antihypertensive activity of 200 °C in 1% PAM, ADM, and mantle with 85.85 ± 0.67, 84.55 ± 0.18, and 82.15 ± 0.85%, respectively, compared to 97.57 ± 0.67% in 1% standard captopril. Perhaps the most significant finding was the predominance of taurine in the three parts following SW treatment at 120 °C. The hydrolysates may be of considerable interest for use in food or energy drinks. SWH demonstrates efficacy in recovering amino acids, particularly taurine, from edible parts of A. pectinata.  相似文献   
996.
In this study, we characterized and mapped a new and rare resistance gene (RphFT) in the Chinese barley variety ‘Fong Tien’. RphFT, a dominant gene, was mapped to chromosome 5HL at a genetic position of 142.1 cM using DArT‐seq markers. The gene was also confirmed to be present in Australian cultivar ‘Yagan’ based on allelic tests, and likely ‘Lockyer’ based on multipathotype tests. The genetic studies also confirmed the presence of Rph12 in Australian cultivar ‘Baudin’. Rph12 is also located on chromosome 5HL close to RphFT, and the two loci were confirmed to be independent. Gene RphFT is of limited breeding value because it is effective to only one pathotype of P. hordei, 220P+ +Rph13 in Australia; nevertheless, it may play a role in controlling leaf rust if used in combination with other Rph genes. The locus symbol Rph25 is recommended for RphFT in accordance with the rules and numbering system of barley gene nomenclature.  相似文献   
997.
Poly(lactic acid) (PLA) is known for environmentally friendly material as it is derived from annually renewable crops and biodegradable. Dispersant-free dyeing of PLA fabric with three temporarily solubilized azo disperse dyes which contain β-sulfatoethylsulfonyl group was investigated and their dyeing and fastness properties were compared with those of commercial disperse dyes. The temporarily solubilized azo disperse dyes were successfully applied to PLA fabric without the use of dispersant. The color yield on PLA fabric was dependent on dyebath pH and dyeing temperature as well. The optimum results were obtained at pH 7-8 and 110 °C. The dyes showed markedly higher color yield on PLA fabric when compared to commercial disperse dyes. Wash fastness was very poor to poor but light fastness was good. The COD levels of the dyeing effluent from the temporarily solubilized disperse dyes were considerably lower than those from commercial disperse dyes.  相似文献   
998.
The use of the hybrid joint has increased in recent years because of its superior mechanical characteristics. In this study, quasistatic experiments were performed to elucidate the failure mechanism of hybrid composite joints upon consideration of the properties of the adhesive, clamping force, and joint width. The results showed that the stiffness of the adhesive is the most important design parameter. In this study, two adhesives with different stiffness values were used. In the case of the joints using the adhesive with the lower stiffness modulus, it was observed that the load was transferred readily through the adhesive since it was shared between the bolt and adhesive more efficiently. This phenomenon allowed the hybrid joints that use the low-modulus adhesive to sustain greater loads before failure, as compared to the joints that use the stiffer adhesive.  相似文献   
999.
Intermittent drainage of rice fields alters soil redox potential and contributes to the reduction of CH4 emission and thus may reduce net global warming potential (GWP) during rice cultivation. Incorporation of green biomass helps maintaining soil organic matter, but may increase CH4 emission. We investigated net ecosystem carbon budget (NECB) and net GWP under two water management regimes—continuous flooding and intermittent drainage—having four biomass incorporation levels (0, 3, 6 and 12 Mg ha?1). Water management and biomass incorporation level demonstrated significant (P < 0.05) interaction effect on the NECB and GWP. Intermittent drainage decreased the NECB by ca. 6–46 % than continuous flooding under same rates of cover crop biomass (CCB) incorporation. Moreover, intermittent drainage reduced seasonal CH4–C fluxes by ca. 54–58 % and net GWP by 35–58 % compared to continuous flooding. There was also no significant reduction in rice yield because of intermittent drainage under similar CCB. This implies that incorporation of 3 Mg ha?1 CCB and intermittent drainage could be a good option for reducing net GWP and higher grain yield.  相似文献   
1000.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号