全文获取类型
收费全文 | 2357篇 |
免费 | 226篇 |
国内免费 | 12篇 |
专业分类
林业 | 186篇 |
农学 | 114篇 |
基础科学 | 8篇 |
398篇 | |
综合类 | 140篇 |
农作物 | 170篇 |
水产渔业 | 294篇 |
畜牧兽医 | 1028篇 |
园艺 | 57篇 |
植物保护 | 200篇 |
出版年
2024年 | 3篇 |
2023年 | 38篇 |
2022年 | 72篇 |
2021年 | 131篇 |
2020年 | 140篇 |
2019年 | 169篇 |
2018年 | 154篇 |
2017年 | 150篇 |
2016年 | 148篇 |
2015年 | 98篇 |
2014年 | 137篇 |
2013年 | 154篇 |
2012年 | 155篇 |
2011年 | 178篇 |
2010年 | 95篇 |
2009年 | 88篇 |
2008年 | 89篇 |
2007年 | 104篇 |
2006年 | 66篇 |
2005年 | 52篇 |
2004年 | 40篇 |
2003年 | 58篇 |
2002年 | 65篇 |
2001年 | 39篇 |
2000年 | 46篇 |
1999年 | 24篇 |
1998年 | 12篇 |
1997年 | 5篇 |
1996年 | 3篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1992年 | 8篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1970年 | 3篇 |
1969年 | 2篇 |
排序方式: 共有2595条查询结果,搜索用时 125 毫秒
991.
Effect of different culture conditions on the structural diversity of prokaryote communities in the sediment of earth ponds stocked with gilthead seabream Sparus aurata (Linnaeus, 1758)
下载免费PDF全文
![点击此处可从《Aquaculture Research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yolanda J Silva Sónia Manco Rodrigo Costa Vera Rodrigues Jorge Dias Hugo Ferreira Pedro Pousão‐Ferreira Adelaide Almeida Angela Cunha Ricardo Calado Newton C M Gomes 《Aquaculture Research》2015,46(7):1760-1769
In this study, we evaluate the use of polymerase chain reaction‐denaturing gradient gel electrophoresis (PCR‐DGGE) for monitoring the effect of different aquaculture practices on sediment prokaryote (Archaea and Bacteria) communities. The effect of initial fish (gilthead seabream Sparus aurata) stocking density on the structural diversity of prokaryote communities of earth ponds bottom sediments was evaluated using PCR‐DGGE after a 5 month grow‐out period. An identical approach was used to monitor the effect of supplying different fish feeds [commercial feed (CD) versus an ecofeed (ECO)]. One additional variable was the use of copper sulphate (CuSO4) as an algicide in some of the experimental rearing tanks. The statistical analyses of prokaryote community profiles showed that the presence of fish in earth ponds significantly influenced the structure of sediment prokaryote communities, when compared with earth ponds without fish, independently of the stocking density. Our results also indicated that the structure of the prokaryote communities of earth ponds supplied with the ECO feed shared a strong similarity with that fed CD. Curiously, the use of CuSO4 in ponds receiving the ECO feed promoted significant differences on the structural composition of the bacterial community, but not on the archaeal community. DGGE molecular fingerprints are suitable for fast evaluation of new management practices in food‐fish production on earth ponds by monitoring shifts on microbial communities in bottom sediments. 相似文献
992.
Effects of stocking density on intermediate culture of the razor clam Ensis arcuatus (Pharidae: Bivalvia)
下载免费PDF全文
![点击此处可从《Aquaculture Research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Fiz da Costa Berta Barreiro Justa Ojea Susana Nóvoa Dorotea Martínez‐Patiño 《Aquaculture Research》2015,46(8):1858-1865
Commercial production of most bivalve species involves a phase of intermediate cultivation during which juveniles are grown under protected conditions until they can be transferred to the final grow‐out location. Consequently, the aim of this study was investigating the effect of density on growth and survival in the intermediate culture of the razor clam Ensis arcuatus in raft. Two series of experiments were performed, using in the first experiment two holding systems: 5‐L plastic bottles and PVC cylinders, both perforated, covered with a 1 mm mesh net to prevent razor clam escape and a 10‐cm layer of coarse grained sand (300–1200 μm grain diameter). In this trial, two stocking densities were tested: 0.15 and 0.30 kg m?2. In the second one‐two densities were essayed (0.62 and 1.24 kg m?2) in the PCV cylinders. In the first experiment after 27 of trial higher growth in cylinders at low density was observed. At the end of this trial all juveniles died in the 5‐L plastic bottles and higher growth and survival were recorded in the cylinders at low density. In the second experiment, significant differences in growth and survival were found on day 70, with the best results at low density. Five‐L plastic bottles must be rejected as holding system for the intermediate culture of E. arcuatus and the PVC cylinders at low densities could be a good alternative. At the end of the experiment razor clams reached the adequate size for their transfer into the grow‐out system. 相似文献
993.
Induced polyploidy in inter‐subspecific maize hybrids to reduce heterosis breakdown and restore reproductive fertility
下载免费PDF全文
![点击此处可从《Grass and Forage Science》网站下载免费的PDF全文](/ch/ext_images/free.gif)
I. A. K. Niazi S. Rauf J. A. Teixeira da Silva Z. Iqbal H. Munir 《Grass and Forage Science》2015,70(4):682-694
The aim of this study was to reduce the breakdown of hybrid vigour by crossing maize × teosinte subspecies through induced tetraploidy and to improve the biomass and reproductive fertility of the induced tetraploids. To achieve this, seeds of maize breeding lines selected from an open‐pollinated population ‘Sargodha‐2002’ and a maize × teosinte cross were germinated in colchicine solution (0·25, 0·5 or 1·0%) until they had a thick radical and protruded plumule. Colchicine at 0·5% induced the highest number of tetraploids with the lowest number of chimeric plants. The induced tetraploids of maize and maize × teosinte crosses showed a significant (P ≤ 0·05) increase in leaf area (5 and 14%), total soluble solids (20 and 18%), leaf oil percentage (42 and 12%) and leaf crude protein contents (10 and 14%) in leaves relative to the diploid subspecies. Moreover, induced tetraploidy also arrested hybrid vigour by slowing down the decay of heterosis in progenies (4x) for plant height, leaf biomass and leaf oil percentage. Induced maize × teosinte hybrid tetraploids selected for frequent bivalent chromosome pairing resulted in higher seed setting cob?1 (increased 58%), pollen fertility (increased 59%) and seed setting percentage (increased 100%) than the quadrivalent variant. 相似文献
994.
José Roberto Pereira de Sousa Fernando da Silva Carvalho-Filho Maria Cristina Esposito 《Journal of insect science (Online)》2015,15(1)
This study aimed at surveying the local calliphorid and sarcophagid species in
Maranhão State (Brazil) to determine their distribution and abundance, as well
as the distribution of exotic Chrysomya species. In total, 18,128
calliphorid specimens were collected, distributed in 7 genera and 14 species. The
species Hemilucilia semidiaphana (Rondani, 1850) and
Paralucilia paraensis (Mello, 1969) were new state records.
Chrysomya albiceps (Wiedemann, 1819) and Cochliomyia
macellaria (F., 1775) were the most abundant species, and the exotic
species of Chrysomya together contributed more than 50% of
total blow fly abundance. The abundance distribution of the calliphorid community
conformed to a log series model, characterized by a steep curve that reflects an
assemblage with a high degree of dominance. For the Sarcophagidae, a total of 14,810
specimens were collected and distributed in 15 genera, 11 subgenera, and 52 species.
Tricharaea (Sarcophagula)
occidua (F., 1794) and Peckia
(Sarcodexia) lambens (Wiedemann, 1830) were the
most abundant species. The abundance distribution of the species followed a log
normal model, with a gentler slope, consistent with a more uniform community. The
cumulative species curve for the sarcophagids did not reach the asymptote.
Forty-three sarcophagid species were new state records and 22 were new records for
the Brazilian northeast, which emphasizes the need for a continued survey in this
region. 相似文献
995.
996.
997.
Direct determination of methyl parathion insecticide in rice samples by headspace solid‐phase microextraction–gas chromatography–mass spectrometry
下载免费PDF全文
![点击此处可从《Pest management science》网站下载免费的PDF全文](/ch/ext_images/free.gif)
998.
Daniele Dietrich Moura Costa Dandie Antunes Bozza Luiz Eduardo Rizzo Juan Garcia Michele Dietrich Moura Costa Ciro Alberto de Oliveira Ribeiro 《Fish physiology and biochemistry》2016,42(6):1721-1732
Endocrine-disrupting chemicals (EDCs) are widespread used and can interfere on hormone regulation with adverse consequences for both biota and human. Vitellogenin (vtg) is a yolk precursor protein synthesized by the liver in response to estrogen. In order to characterize the vtg of tropical fish Rhamdia quelen and establish a molecular biomarker, adult male individuals were exposed to 17-β-estradiol (E2) for vtg induction and anti-R. quelen vtg polyclonal antibodies production. Vitellogenic female fish were used as positive control group. E2-induced vtg was characterized as a glycolipophosphoprotein of high molecular mass with peptide mass fingerprint very similar in E2-exposed male and vitellogenic female fish. A polyclonal serum containing anti-R. quelen vtg antibodies was produced and showed high specificity and sensibility to detect the vtg of three fish species: R. quelen, Piaractus mesopotamicus and Prochilodus lineatus. Wildlife and laboratory studies reported that EDCs released into the environment may alter the levels of plasma vtg in male fish, making this protein a valuable biomarker of xenoestrogens exposure. Then, we propose the use of anti-R. quelen vtg as a tool for biomonitoring studies and water quality assessment in Brazil and South American countries where the three fish species occur. 相似文献
999.
1000.
Simoni Campos Dias Maria Cristina Mattar da Silva Edson Luis Zangrando Figueira Osmundo Brilhante de Oliveira-Neto Loaiane Alves de Lima Maria Fátima Grossi-de-Sa 《Pesticide biochemistry and physiology》2010,98(1):39-4821
Innumerable proteinaceous α-amylase inhibitors have been isolated and identified from different plant species. Among them, an α-amylase inhibitor gene with bioinsecticidal potential toward Anthonomus grandis (cotton boll weevil) was previously identified in rye seeds (Secale cereale). This cereal inhibitor was expressed in tobacco plants (Nicotiana tabacum) under control of phytohemaglutinin promoter by using Agrobacterium tumefasciens - mediated transformation. Presence of αBIII-rye gene and further protein expression were confirmed by PCR and Western blot analysis, respectively. Immunological assays indicated that the recombinant inhibitor was expressed in concentration range from 0.1% to 0.28% (w:w) of the total protein in tobacco seeds of R0 plants. From 14 independent transformants, five plants with expression levels between 0.20% and 0.28% in seeds were in vitro assayed against A. grandis amylolytic enzymes causing clear inhibition. Moreover, bioassays using transgenic seed flour mixture for artificial diet produced 74% mortality in A. grandis first larval instar. These data suggest that rye inhibitor could be a promising biotechnological tool for produce transgenic cotton plants with an increased resistance to cotton boll weevil. Moreover, αBIII-rye gene should be considered a potential compound for a pyramiding strategy aiming to delay insect-resistance. 相似文献