全文获取类型
收费全文 | 2283篇 |
免费 | 149篇 |
国内免费 | 2篇 |
专业分类
林业 | 96篇 |
农学 | 32篇 |
基础科学 | 7篇 |
223篇 | |
综合类 | 666篇 |
农作物 | 55篇 |
水产渔业 | 209篇 |
畜牧兽医 | 988篇 |
园艺 | 65篇 |
植物保护 | 93篇 |
出版年
2023年 | 16篇 |
2022年 | 17篇 |
2021年 | 40篇 |
2020年 | 41篇 |
2019年 | 50篇 |
2018年 | 44篇 |
2017年 | 39篇 |
2016年 | 47篇 |
2015年 | 47篇 |
2014年 | 42篇 |
2013年 | 100篇 |
2012年 | 78篇 |
2011年 | 122篇 |
2010年 | 59篇 |
2009年 | 64篇 |
2008年 | 84篇 |
2007年 | 106篇 |
2006年 | 101篇 |
2005年 | 92篇 |
2004年 | 71篇 |
2003年 | 63篇 |
2002年 | 63篇 |
2001年 | 38篇 |
2000年 | 48篇 |
1999年 | 31篇 |
1995年 | 14篇 |
1992年 | 28篇 |
1991年 | 27篇 |
1990年 | 25篇 |
1989年 | 22篇 |
1988年 | 15篇 |
1987年 | 42篇 |
1986年 | 60篇 |
1985年 | 57篇 |
1984年 | 43篇 |
1983年 | 46篇 |
1982年 | 36篇 |
1981年 | 34篇 |
1980年 | 39篇 |
1979年 | 35篇 |
1978年 | 38篇 |
1977年 | 31篇 |
1976年 | 31篇 |
1975年 | 29篇 |
1974年 | 33篇 |
1973年 | 19篇 |
1972年 | 16篇 |
1971年 | 16篇 |
1970年 | 15篇 |
1969年 | 18篇 |
排序方式: 共有2434条查询结果,搜索用时 15 毫秒
51.
52.
Robert M. REES Juliette MAIRE Anna FLORENCE Nicholas COWAN Ute SKIBA Tony van der WEERDEN Xiaotang JU 《农业科学与工程前沿(英文版)》2020,7(1):75-80
Nitrous oxide (N2O) emissions make up a significant part of agricultural greenhouse gas emissions. There is an urgent need to identify new approaches to the mitigation of these emissions with emerging technology. In this short review four approaches to precision managements of agricultural systems are described based on examples of work being undertaken in the UK and New Zealand. They offer the opportunity for N2O mitigation without any reduction in productivity. These approaches depend upon new sensor technology, modeling and spatial information with which to make management decisions and interventions that can both improve agricultural productivity and environmental protection. 相似文献
53.
Day Casey C. Zollner Patrick A. Gilbert Jonathan H. McCann Nicholas P. 《Landscape Ecology》2020,35(10):2191-2208
Landscape Ecology - Functional landscape connectivity is vital for the conservation of wildlife species. Landscape connectivity models often overlook factors such as mortality and asymmetry in... 相似文献
54.
Robinson P 《Science (New York, N.Y.)》1966,154(3746):264
A specimen of the murid rodent Nesokia indica has been recovered from a late Paleolithic archeological site in the Sudan. This is a range 1200 km south of the site of any known occurrences, and it indicates a different environment near the Nile River than that which exists at the present time. The late Paleolithic water table is inferred to have been more stable, allowing for permanent moist soil. 相似文献
55.
56.
Makris NC Ratilal P Symonds DT Jagannathan S Lee S Nero RW 《Science (New York, N.Y.)》2006,311(5761):660-663
Until now, continental shelf environments have been monitored with highly localized line-transect methods from slow-moving research vessels. These methods significantly undersample fish populations in time and space, leaving an incomplete and ambiguous record of abundance and behavior. We show that fish populations in continental shelf environments can be instantaneously imaged over thousands of square kilometers and continuously monitored by a remote sensing technique in which the ocean acts as an acoustic waveguide. The technique has revealed the instantaneous horizontal structural characteristics and volatile short-term behavior of very large fish shoals, containing tens of millions of fish and stretching for many kilometers. 相似文献
57.
Godfree Chigeza Steve Boahen Melaku Gedil Eric Agoyi Hapson Mushoriwa Nicholas Denwar Therese Gondwe Abush Tesfaye Alpha Kamara Oladeji Emmanuel Alamu David Chikoye 《Plant Breeding》2019,138(4):455-464
Formal public sector soybean breeding in Africa spans over four decades, and it was initiated by the International Institute of Tropical Agricultural (IITA). As the demand of soybean continues to outstrip production, strategic projects such the Tropical Legume (TL) were initiated, in which the main goal was to enhance the productivity of soybean in the farmers’ fields in Sub‐Saharan Africa. One of the strategies to enhance the productivity of soybean in the farmers’ fields is through developing and deploying improved soybean varieties in the target countries. Through the TL I and TL II projects, a number of varieties were released in the target countries, Kenya, Nigeria, Malawi and Mozambique by employing participatory variety selection (PVS). This review provides highlights of the achievements made by IITA breeding programme and insights of what needs to be done to enhance yield improvement for soybean in Africa using demand‐driven breeding approaches. 相似文献
58.
Frdrick G. Sunstrum Wubishet A. Bekele Charlene P. Wight Weikai Yan Yuanhong Chen Nicholas A. Tinker 《Plant Breeding》2019,138(1):82-94
We developed 178 recombinant inbred lines from a southern‐by‐spring oat population designated as “TxH.” These lines were genotyped to generate a high‐quality linkage map that resolved 6,902 markers into 21 linkage groups that matched closely with the latest hexaploid oat consensus map. Three major quantitative trait loci (QTLs) affecting heading date were found in locations that are consistent with known QTLs and candidate genes, and two other QTLs affecting heading date were found in novel locations. Five QTLs affecting plant height were found. Both sets of QTLs are responsible for transgressive segregation observed for these two traits. Four QTLs affecting resistance to crown rust, caused by the pathogen Puccinia coronata f. sp. avenae, were identified. Two of these QTLs are consistent with known clusters of rust resistance genes, while two may represent new locations of novel rust resistance genes. A complete set of SNP sequences suitable for generating markers for molecular selection is provided. 相似文献
59.
Emilie Laurin Krishna Thakur Peter G. Mohr Paul Hick Mark St. J. Crane Ian A. Gardner Nicholas J. G. Moody Axel Colling Ingo Ernst 《Journal of fish diseases》2019,42(11):1471-1491
Samples from multiple animals may be pooled and tested to reduce costs of surveillance for infectious agents in aquatic animal populations. The primary advantage of pooling is increased population‐level coverage when prevalence is low (<10%) and the number of tests is fixed, because of increased likelihood of including target analyte from at least one infected animal in a tested pool. Important questions and a priori design considerations need to be addressed. Unfortunately, pooling recommendations in disease‐specific chapters of the 2018 OIE Aquatic Manual are incomplete and, except for amphibian chytrid fungus, are not supported by peer‐reviewed research. A systematic review identified only 12 peer‐reviewed aquatic diagnostic accuracy and surveillance studies using pooled samples. No clear patterns for pooling methods and characteristics were evident across reviewed studies, although most authors agreed there is a negative effect on detection. Therefore, our purpose was to review pooling procedures used in published aquatic infectious disease research, present evidence‐based guidelines, and provide simulated data examples for white spot syndrome virus in shrimp. A decision tree of pooling guidelines was developed for use by peer‐reviewed journals and research institutions for the design, statistical analysis and reporting of comparative accuracy studies of individual and pooled tests for surveillance purposes. 相似文献
60.
Gustafson L Ellis S Robinson T Marenghi F Merrill P Hawkins L Giray C Wagner B 《Journal of fish diseases》2007,30(2):101-109
The distribution of infectious salmon anaemia (ISA) was examined among 80 cages from three Atlantic salmon grow-out farms in Maine, USA that were stocked with smolts from a single hatchery. Cage-level disease was broadly defined as one or more moribund fish testing positive for infectious salmon anaemia virus (ISAV) by RT-PCR and a second confirmatory test (IFAT, culture or genotype sequence). Spatio-temporal and cage-level risks were explored using logistic regression and survival analysis. Non-spatial risk factors associated with ISA, or shortened survival time to disease, included increased predation, trucking company choice for smolt transfers, a finely-sedimented benthic substrate, and smaller average size of smolts at stocking. Univariable analysis identified the time-dependent spatial factor 'adjacency to newly infected cages' to be predictive of new infection in neighbouring cages 11-12 weeks later. However, none of the spatial factors, or their lags retained relevance in multiple-variable models. The results suggest a diffuse distribution of virus exposure throughout infected sites, with host-susceptibility factors probably influencing disease manifestation in individual cages. The narrow focus of the current study may limit application of the findings to other sites and year-classes. However, these data support the relevance of husbandry efforts to optimize fish health in regions affected by ISAV. 相似文献