全文获取类型
收费全文 | 780篇 |
免费 | 54篇 |
国内免费 | 1篇 |
专业分类
林业 | 123篇 |
农学 | 12篇 |
基础科学 | 4篇 |
194篇 | |
综合类 | 84篇 |
农作物 | 23篇 |
水产渔业 | 41篇 |
畜牧兽医 | 266篇 |
园艺 | 31篇 |
植物保护 | 57篇 |
出版年
2023年 | 16篇 |
2022年 | 16篇 |
2021年 | 20篇 |
2020年 | 32篇 |
2019年 | 30篇 |
2018年 | 33篇 |
2017年 | 27篇 |
2016年 | 30篇 |
2015年 | 20篇 |
2014年 | 32篇 |
2013年 | 34篇 |
2012年 | 58篇 |
2011年 | 65篇 |
2010年 | 40篇 |
2009年 | 43篇 |
2008年 | 62篇 |
2007年 | 36篇 |
2006年 | 48篇 |
2005年 | 35篇 |
2004年 | 32篇 |
2003年 | 27篇 |
2002年 | 23篇 |
2001年 | 11篇 |
2000年 | 7篇 |
1999年 | 8篇 |
1998年 | 2篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1977年 | 1篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1958年 | 1篇 |
1941年 | 2篇 |
1940年 | 1篇 |
1939年 | 7篇 |
1938年 | 3篇 |
1937年 | 5篇 |
排序方式: 共有835条查询结果,搜索用时 468 毫秒
831.
Ying?Zhao Jinbo?ZhangEmail author Christoph?Müller Zucong?Cai 《Biology and Fertility of Soils》2018,54(5):659-669
Purple soils (Eutric Regosols) are widely distributed in humid subtropical Southwest China. They are characterized by high nitrification activities, with risks of severe NO3? leaching. Incorporation of crop residues is considered an effective method to reduce NO3? loss. In the present study, we compared the effects of alfalfa, rice straw, and sugarcane bagasse on gross N transformation turnover in a purple soil (purple soil, pH 7.62) compared with those in an acid soil (acid soil, pH 5.26), at 12 h, 3 months, and 6 months after residue incorporation. The gross N transformation rates were determined by 15N tracing. All tested crop residues stimulated the gross N mineralization rates, but reduced the net mineralization rates in both soils at 12 h after residue incorporation; however, the extent of the effect varied with the crop residue qualities, with rice straw having the strongest effects. Crop residues reduced net nitrification rates by depressing gross autotrophic nitrification rates and stimulating NO3? immobilization rates in the purple soil, particularly after rice straw incorporation (net nitrification rate decreased from 16.72 mg N kg?1 d?1 in the control to ??29.42 mg N kg?1 d?1 at 12 h of residue incorporation); however, crop residues did not affect the gross autotrophic nitrification rates in the acid soil. Crop residue effects subsided almost completely within 6 months, with sugarcane bagasse showing the longest lasting effects. The results indicated that crop residues affected the N transformation rates in a temporal manner, dependent on soil properties and residue qualities. 相似文献
832.
Tongbin?Zhu Cheng?Yang Jun?Wang Siman?Zeng Manqiang?Liu Jinling?Yang Bing?Bai Jianhua?Cao Xiaoyun?ChenEmail author Christoph?Müller 《Biology and Fertility of Soils》2018,54(1):107-118
We conducted a microcosm experiment with soil being sterilized, reinoculated with native microbial community and subsequently manipulated the bacterivorous nematodes, including three treatments: without (CK) or with introducing one species of the two bacterivores characterized with different body size but similar c-p (colonizer-persister) value (Rhabditis intermedia and Protorhabditis oxyuroides, accounted for 6 and 59% of bacterivores in initially undisturbed soil, respectively). We monitored the N2O and CO2 emissions, soil properties, and especially quantified gross N transformation rates using 15N tracing technique after the 50 days incubation. No significant differences were observed on soil NH4 + and NO3 ? concentrations between the CK and two bacterivores, but this was not the case for gross N transformation rates. In comparison to CK, R. intermedia did not affect soil N transformation rates, while P. oxyuroides significantly increased the rates of mineralization of organic N to NH4 +, oxidation of NH4 + to NO3 ?, immobilization of NO3 ? to organic N and dissimilatory NO3 ? reduction to NH4 +. Furthermore, the mean residence time of NH4 + and NO3 ? pool was greatly lowered by P. oxyuroides, suggesting it stimulated soil N turnover. Such stimulatory effect was unrelated to the changes in abundance of bacteria and ammonia-oxidizing bacteria (AOB). In contrast to CK, only P. oxyuroides significantly promoted soil N2O and CO2 emissions. Noticeably, bacterivores increased the mineralization of recalcitrant organic N but decreased soil δ13C-TOC and δ15N-TN values, in particular for P. oxyuroides. Combining trait-based approach and isotope-based analysis showed high potential in moving forward to a mechanistic understanding of bacterivore-mediated N cycling. 相似文献
833.
Claudia?KammannEmail authorView authors OrcID profile Stefan?Ratering Carolyn-Monika?G?rres Cécile?Guillet Christoph?Müller 《Biology and Fertility of Soils》2017,53(5):491-499
In this study, the impact of rose chafer (Cetonia aurata L.) larvae on net and gross methane (CH4) fluxes in soil from an old permanent grassland site (Giessen, Germany) was investigated. Previous studies at this site suggested the existence of Scarabaeidae larvae-induced “CH4-emitting hot spots” within the soil profile which may subsequently lead to increased CH4 oxidation. The net (soil + larvae) and gross (soil and larvae separated) CH4 fluxes were studied in a 3-month laboratory incubation. Addition of larvae changed the soil from a net sink (?330 ± 11 ng CH4 kg?1 h?1) to a net source (637 ± 205 ng CH4 kg?1 h?1). Supply of plant litter to the soil + larvae incubation jars tended to increase CH4 emissions which was not significant due to large variability. After 11–13 weeks of incubation, the net soil CH4 oxidation was significantly stimulated by 13–21% in the treatments containing larvae when these were taken out. Analysis of archaeal 16S rRNA genes revealed that the majority of the obtained clones were closely related to uncultured methanogens from guts of insects and other animals. Other sequences were relative to cultivated species of Methanobrevibacter, Methanoculleus, and Methanosarcina. Hence, Scarabaeidae larvae in soils (i) may represent an underestimated source of CH4 emissions in aerobic upland soils, (ii) may stimulate gross CH4 consumption in their direct soil environment, and, thus, (iii) contribute to the spatial heterogeneity often observed in the field with closed-chamber measurements. Long-term CH4-flux balances may be wrongly assessed when “exceptional” net CH4 flux rates (due to larvae hot spots) are excluded from data sets. 相似文献
834.
Stephan Leisengang Dennis Gluding Julia Hrster Verena Peek Daniela Ott Christoph Rummel Martin J. Schmidt 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2022,36(4):1373
BackgroundCompression of epidural adipose tissue (EAT) within the scope of cauda equina syndrome (CES) could lead to an enhanced expression of inflammatory mediators, possibly contributing to pain amplification in dogs.ObjectivesTo analyze expression of inflammatory adipo(‐cyto)kines within the EAT of dogs with CES.AnimalsClient‐owned dogs: 15 dogs with CES and 9 dogs euthanized for unrelated medical reasons (controls).MethodsProspective, experimental study. Epidural adipose tissue and subcutaneous adipose tissue were collected during dorsal laminectomy and used for real‐time quantitative polymerase chain reaction. Tissue explants were cultured for measurements of inflammation‐induced release of cytokines.ResultsResults show a CES‐associated upregulation of the cytokines tumor necrosis factor alpha (TNFα: mean ± SD: 18.88 ± 11.87, 95% CI: 10.90‐26.86 vs 9.66 ± 5.22, 95% CI: 5.29‐14.02, *: P = .04) and interleukin‐ (IL‐) 10 (20.1 ± 9.15, 95% CI: 14.82‐25.39 vs 11.52 ± 6.82, 95% CI: 5.82‐17.22, *: P = .03), whereas the expression of the adipokine leptin was attenuated in EAT of dogs with CES (3.07 ± 2.29, 95% CI: 1.80‐3.34 vs 9.83 ± 8.42, 95% CI: 3.36‐16.30, **: P = .007). Inflammatory stimulation of EAT explant cultures resulted in an enhanced release of IL‐6 (LPS: 5491.55 ± 4438, 95% CI: 833.7‐10 149; HMGB1: 1001.78 ± 522.2, 95% CI: 518.8‐1485; PBS: 310.9 ± 98.57, 95% CI: 228.5‐393.3, ***: P < .001).Conclusion and Clinical ImportanceExpression profile of inflammatory adipo(‐cyto)kines by EAT is influenced from compressive forces acting in dogs with CES and might contribute to amplification of pain. 相似文献
835.