全文获取类型
收费全文 | 5324篇 |
免费 | 150篇 |
国内免费 | 144篇 |
专业分类
林业 | 625篇 |
农学 | 426篇 |
基础科学 | 60篇 |
389篇 | |
综合类 | 1382篇 |
农作物 | 391篇 |
水产渔业 | 138篇 |
畜牧兽医 | 800篇 |
园艺 | 1097篇 |
植物保护 | 310篇 |
出版年
2024年 | 56篇 |
2023年 | 222篇 |
2022年 | 275篇 |
2021年 | 178篇 |
2020年 | 244篇 |
2019年 | 267篇 |
2018年 | 201篇 |
2017年 | 189篇 |
2016年 | 127篇 |
2015年 | 172篇 |
2014年 | 165篇 |
2013年 | 253篇 |
2012年 | 201篇 |
2011年 | 160篇 |
2010年 | 123篇 |
2009年 | 320篇 |
2008年 | 124篇 |
2007年 | 85篇 |
2006年 | 73篇 |
2005年 | 82篇 |
2004年 | 255篇 |
2003年 | 102篇 |
2002年 | 175篇 |
2001年 | 130篇 |
2000年 | 183篇 |
1999年 | 84篇 |
1998年 | 66篇 |
1997年 | 79篇 |
1996年 | 222篇 |
1995年 | 137篇 |
1994年 | 123篇 |
1993年 | 92篇 |
1992年 | 84篇 |
1991年 | 53篇 |
1990年 | 54篇 |
1989年 | 28篇 |
1988年 | 43篇 |
1987年 | 12篇 |
1986年 | 19篇 |
1985年 | 23篇 |
1984年 | 18篇 |
1983年 | 22篇 |
1982年 | 16篇 |
1981年 | 18篇 |
1980年 | 16篇 |
1979年 | 30篇 |
1978年 | 15篇 |
1977年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有5618条查询结果,搜索用时 15 毫秒
991.
稻田高产节水灌溉方式的研究 总被引:11,自引:0,他引:11
1984~1988年在中国水稻研究所实验场排水与其它农业措施相结合,采用节水灌溉措施和高产灌溉制度,综合考虑对田面水、土壤水、地下水和雨水的统一管理利用和合理调节控制,通过大田、小区、测坑试验和生产实践,提出了适合当地条件的节水高产灌排方式、地下水埋深度和排水量。这种水综合运用,既可节约灌溉用水量,减少灌水次数,还可降低排涝水量,减轻排涝能耗费用。 相似文献
992.
口蹄疫病毒结构蛋白P1基因转化玉米的初步研究 总被引:4,自引:0,他引:4
实验在构建口蹄疫病毒(Foot and Mouth Disease Virus,FMDV)结构蛋白P1基因植物双元表达载体(pBI131SP1、pBI21P1和pBI121AP1)的基础上,以玉米自交系8902、340、4112的Ⅱ型胚性愈伤组织为受体,用农杆菌介导法和基因枪轰击法转化玉米,获得31株抗性再生植株.GUS染色证明外源目的基因在玉米细胞和组织中得到了表达.PCR检测、Southem blotting鉴定证实目的基因P1已整合到再生植株的基因组中,共获得了13株转基因玉米植株,首次进行了FMDV抗原基因转化玉米的研究。 相似文献
993.
994.
以15个自交系为材料,按P(P-1)/2双列杂交设计,研究了株型和产量性状的遗传与相关.结果表明,近年育成的自交系,一般配合力有一定的改进,产量性状的一般配合力有明显的提高,各性状的一般配合力在亲本间存在显著差异.产量的一般配合力与单株叶数和穗粗的一般配合力存在极显著正相关。 相似文献
995.
996.
Thermal degradation kinetics of bioactive compounds from black rice flour (Oryza sativa L.) extracts
The effect of thermal processing on the degradation of the phytochemicals in black rice flour by means of fluorescence spectroscopy and degradation kinetics was investigated. In order to investigate the influence of food matrices, a comparative analysis between integral rice flour and different fractions was performed. The preliminary compositional results suggested a higher content in phytochemicals in fraction four of the seven fractions of black rice flour, which was sifting through a sieve with a diameter of 180 μm. The compositional complexity was highlighted by fluorescence spectroscopy. The heat-treatment caused structural changes that led to red- or blue-shifts in maximum emission. The first-order kinetic model was used to describe the mechanism of degradation. The activation energies were 10.07 ± 1.04 kJ/mol for total polyphenolic, 7.26 ± 0.58 kJ/mol for total monomeric anthocyanins and 6.71 ± 1.12 kJ/mol for antioxidant activity in case of integral flour extract. For fraction four extract obtained by, the Ea values were: 3.51 ± 0.53 kJ/mol, 11.49 ± 1.47 kJ/mol, 15.80 ± 1.50 kJ/mol and 19.91 ± 3.27 kJ/mol, respectively. The calculated values of the activation energy revealed higher temperature dependence of total polyphenols in integral flour and of antioxidant activity in fraction four, respectively. 相似文献
997.
The effect of inclusion of cashew globulin to a casein diet on lipid metabolism was studied in rats fed diets with two levels of cashew globulin meal. Inclusion of cashew globulin to a casein diet produced lower levels of total cholesterol, triacylglycerol and phospholipids in the serum and tissues and lower levels of serum lipoprotein cholesterol. There was decreased cholesterogenesis in the liver as evidenced by decreased activity of HMG CoA reductase and decreased release of lipoproteins into circulation. Rats fed cashew globulin along with casein also showed higher activity of LPL in the heart and adipose tissue and higher activity of LCAT. Increased hepatic diversion of cholesterol to bile acid synthesis and increased excretion of bile acids and sterols were also observed in these groups. Activity of glucose-6-phosphate dehydrogenase and malic enzyme was decreased in rats fed cashew globulin along with casein. This study demonstrates that cashew globulins included in the diet of rats are able to alter lipid metabolism which results in lower levels of lipid parameters in the serum and tissues. 相似文献
998.
Biodegradation measurements confirm the predictive value of the O:C‐ratio for biochar recalcitrance 下载免费PDF全文
Mo Bai Burkhard Wilske Franz Buegger Esben Wilson Bruun Martin Bach Hans‐Georg Frede Lutz Breuer 《植物养料与土壤学杂志》2014,177(4):633-637
Suitable predictors of degradability are sought to support the identification of biochars with large potential to increase C sequestration in soils. We determined the biodegradation of 9 chars from hydrothermal carbonization and pyrolysis in two agricultural soils. The 200‐ and 115‐day degradation correlated strongly with the O:C‐ and slightly with the H:C‐atomic ratio of 9 and 14 biochars, respectively. Highest temperature treatment and ash content did not show similar correlations. 相似文献
999.
Whittemore JC Marcum BA Mawby DI Coleman MV Hacket TB Lappin MR 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2011,25(4):818-824
Background: Microalbuminuria and C‐reactive protein (CRP) are predictors of morbidity and survival in critically ill human patients. Hypothesis/Objectives: To evaluate results of microalbuminuria assays (untimed single‐sample urine albumin concentration [U‐ALB] and the urine albumin : creatinine ratio [UACR]), serum CRP, and survival predictor index (SPI2) scores as predictors of survival in critically ill dogs. Animals: Seventy‐eight dogs admitted to intensive care units at University of Tennessee (UT) and Colorado State University (CSU). Methods: Prospective observational study. Critically ill dogs were eligible for enrollment, unless euthanized because of financial constraints. Samples were collected within 3 hours of admission. Spearman's rank‐correlation coefficients were determined for U‐ALB, UACR, CRP, and SPI2. U‐ALB, UACR, CRP, and SPI2 were assessed for associations with 7‐ and 30‐day survival by Mann‐Whitney U‐tests and receiver operating characteristic (ROC) curves. P‐values < .0125 were considered significant. Results: UT (n = 49) and CSU (n = 29) patients did not differ significantly. Forty percent (31/78) of dogs died. SPI2 was inversely correlated with U‐ALB (rs=?0.39, P < .001) and UACR (rs=?0.41, P < .001). CRP was not correlated with SPI2 (P= .019), U‐ALB (P > .1), or UACR (P > .1). U‐ALB and UACR had very high correlation (rs= 0.95, P < .001). SPI2, U‐ALB, and UACR differed significantly for survivors and nonsurvivors. SPI2, U‐ALB, and UACR had areas under the ROC curve (AUC) from 0.68 to 0.74 for survival prediction. Conclusions and Clinical Importance: Albuminuria and SPI2, but not CRP, are associated with survival in critically ill dogs. Suboptimal AUCs limit the value of microalbuminuria testing for clinical risk assessment. Additional studies are necessary to determine the usefulness of microalbuminuria testing in patient risk stratification for prospective research. 相似文献
1000.
【摘要】为研究超声辅助提取对大豆膳食纤维提取效率及物性的影响,以超声波进行辅助,并进行工艺优化和产品物性分析。在液料比,超声功率强度,超声温度和超声时间4个单因素试验的基础上,通过四元二次通用旋转组合设计试验优化超声辅助提取豆渣中大豆膳食纤维的工艺条件,并采用扫描电镜、红外光谱仪等对大豆膳食纤维产品进行了物性表征。试验结果表明,在液料比35ml/g,超声功率强度600W/g,超声温度50 ℃,间歇性超声处理累计时间50 min条件下大豆膳食纤维得率最高,达92.11%。物性分析结果表明,与酸溶碱沉提取、酶解辅助提取的大豆膳食纤维相比,超声辅助提取的大豆膳食纤维具有更高的持水力、溶胀力、结合水力和结合脂肪能力以及更丰富的空间网状结构;同时,超声处理增加了膳食纤维的游离羟基,但未改变其热降解机理。试验结果显示,超声辅助提取不仅能够提高大豆膳食纤维的提取率,而且对其加工性能有很好的改进作用。 相似文献