全文获取类型
收费全文 | 26196篇 |
免费 | 775篇 |
国内免费 | 15篇 |
专业分类
林业 | 4290篇 |
农学 | 1617篇 |
基础科学 | 184篇 |
5191篇 | |
综合类 | 1148篇 |
农作物 | 2664篇 |
水产渔业 | 2803篇 |
畜牧兽医 | 5178篇 |
园艺 | 1277篇 |
植物保护 | 2634篇 |
出版年
2024年 | 13篇 |
2023年 | 104篇 |
2022年 | 173篇 |
2021年 | 346篇 |
2020年 | 351篇 |
2019年 | 373篇 |
2018年 | 3051篇 |
2017年 | 3043篇 |
2016年 | 1615篇 |
2015年 | 421篇 |
2014年 | 509篇 |
2013年 | 730篇 |
2012年 | 1581篇 |
2011年 | 2849篇 |
2010年 | 2465篇 |
2009年 | 1574篇 |
2008年 | 1890篇 |
2007年 | 2155篇 |
2006年 | 489篇 |
2005年 | 512篇 |
2004年 | 485篇 |
2003年 | 537篇 |
2002年 | 413篇 |
2001年 | 199篇 |
2000年 | 225篇 |
1999年 | 141篇 |
1998年 | 49篇 |
1997年 | 30篇 |
1996年 | 31篇 |
1995年 | 27篇 |
1994年 | 28篇 |
1993年 | 34篇 |
1992年 | 41篇 |
1991年 | 33篇 |
1990年 | 42篇 |
1989年 | 69篇 |
1988年 | 42篇 |
1987年 | 39篇 |
1986年 | 27篇 |
1985年 | 26篇 |
1984年 | 22篇 |
1983年 | 21篇 |
1981年 | 11篇 |
1980年 | 12篇 |
1979年 | 17篇 |
1977年 | 15篇 |
1976年 | 13篇 |
1972年 | 11篇 |
1968年 | 12篇 |
1966年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
81.
82.
Umma Tamima 《林业研究》2016,27(4):853-861
The objective was to evaluate the performance of the co-management of Nishorgo Support Project at Chunati Wildlife Sanctuary in Bangladesh. I adopted the Focus Groups Discussion method for opinion survey and applied the SWOTAHP technique for data analysis. Local people did not participate in the decision-making process of forest management and they perceived co-management as a threat to their livelihoods. Moreover, mistrust and misunderstanding among different stakeholders, political and ethical conflicts, lack of property rights of tribal communities, and lack of accountability and transparency were identified as the drawbacks of co-management. 相似文献
83.
84.
85.
86.
87.
88.
É. Darkó J. Fodor S. Dulai H. Ambrus A. Szenzenstein Z. Király B. Barnabás 《Journal of Agronomy and Crop Science》2011,197(6):454-465
To improve the abiotic stress tolerance of maize (Zea mays L.), doubled haploid (DH) plants were produced by in vitro selection of microspores exposed to tert‐butyl hydroperoxide (t‐BuOOH) as a powerful prooxidant This study investigated the tolerance of the progenies of t‐BuOOH‐selected DH lines to oxidative stress, cold and drought in controlled environment pot experiments by analyses of photosynthetic electron transport and CO2 assimilation processes, chlorophyll bleaching and lipid peroxidation of leaves. Our results demonstrated that the t‐BuOOH‐selected DH plants exhibited enhanced tolerance not only to oxidative stress‐induced by t‐BuOOH but also to cold and drought stresses. In addition, they showed elevated activities of antioxidant enzymes such as superoxide dismutase, ascorbate peroxidase, catalase, glutathione reductase and glutathione S‐transferase when compared with the DH lines derived from microspores that were not exposed to t‐BuOOH and to the original hybrid plants. The results suggest that the simultaneous up‐regulation of several antioxidant enzymes may contribute to the oxidative and cold stress tolerance of the t‐BuOOH‐selected DH lines, and that the in vitro microspore selection represents a potential way to improve abiotic stress tolerance in maize. 相似文献
89.
Elayna Cristina da Silva Maciel Edivaldo Sampaio de Almeida Filho William Bertoloni Janessa Sampaio de Abreu 《Journal of the World Aquaculture Society》2014,45(1):35-44
Different stunning methods (carbon dioxide [CO2] and hypothermia) used in industrial fish processing were compared with asphyxia in air, which is used in traditional fishing, to evaluate the effects of these methods on the stress responses and the meat quality of the Amazon hybrid surubim, Pseudoplatystoma fasciatum female × Leiarius marmoratus male. After the application, blood and behavioral indicators were evaluated. Following death by gill cutting, the fish were gutted, and analyses of muscle pH, rigor mortis, the exudation of the meat, and coloration were performed. Significantly higher levels of cortisol and glucose were exhibited by the fish subjected to asphyxia than by the fish stunned by either CO2 or hypothermia. The fish subjected to asphyxia displayed decreasing muscle pH during the first 2 h after death and showed higher rates of rigor mortis after 3 h than the fish that were stunned by the other two methods. The asphyxia is a practice that exposes fish to suffering by causing an increase in stress responses, which affects meat quality. The immersion of fish in water and ice (hypothermia) for 5 min was more effective stunning method than the use of CO2, resulting in higher loss of sensibility and greater welfare. 相似文献
90.
Effect of Stocking Density on Growth,Survival, and Condition of the Mexican Cichlid Cichlasoma beani
Edgar A. Aragon‐Flores Edna F. Valdez‐Hernandez Leonardo Martinez‐Cardenas Maria R. Castaeda‐Chavez Alfonso A. Gonzales‐Diaz Miriam Soria‐Barreto Javier M. J. Ruiz‐Velazco Emilio Pea‐Messina 《Journal of the World Aquaculture Society》2014,45(4):447-453
The Mexican cichlid Cichlasoma beani is currently exploited regionally as food and can be commercialized in the aquarium trade. Natural populations of C. beani may already be negatively affected by anthropogenic alteration of the areas in which it is distributed. The aim of the present study was to examine the effect on growth, survival, and condition of C. beani cultured in three stocking densities: three (D3), six (D6), and nine (D9) fish per each 40 L tank. At the end of a 6‐wk trial the fish cultured in D3 were longer, heavier, and grew faster than the rest of the treatments but their survival was the lowest compared to D6 and D9. The mortalities were caused by a strong aggressive behavior in D3. 相似文献