全文获取类型
收费全文 | 5737篇 |
免费 | 34篇 |
专业分类
林业 | 269篇 |
农学 | 269篇 |
基础科学 | 17篇 |
1009篇 | |
综合类 | 419篇 |
农作物 | 741篇 |
水产渔业 | 495篇 |
畜牧兽医 | 2167篇 |
园艺 | 81篇 |
植物保护 | 304篇 |
出版年
2025年 | 7篇 |
2024年 | 70篇 |
2023年 | 64篇 |
2022年 | 99篇 |
2021年 | 191篇 |
2020年 | 137篇 |
2019年 | 151篇 |
2018年 | 183篇 |
2017年 | 175篇 |
2016年 | 193篇 |
2015年 | 173篇 |
2014年 | 261篇 |
2013年 | 306篇 |
2012年 | 387篇 |
2011年 | 448篇 |
2010年 | 255篇 |
2009年 | 217篇 |
2008年 | 347篇 |
2007年 | 336篇 |
2006年 | 306篇 |
2005年 | 264篇 |
2004年 | 257篇 |
2003年 | 219篇 |
2002年 | 169篇 |
2001年 | 138篇 |
2000年 | 99篇 |
1999年 | 60篇 |
1998年 | 29篇 |
1997年 | 20篇 |
1996年 | 11篇 |
1995年 | 13篇 |
1994年 | 5篇 |
1993年 | 9篇 |
1992年 | 17篇 |
1991年 | 15篇 |
1990年 | 23篇 |
1989年 | 18篇 |
1988年 | 10篇 |
1987年 | 9篇 |
1986年 | 7篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1980年 | 5篇 |
1978年 | 11篇 |
1974年 | 5篇 |
1972年 | 5篇 |
1970年 | 4篇 |
1969年 | 3篇 |
1968年 | 4篇 |
排序方式: 共有5771条查询结果,搜索用时 15 毫秒
51.
A new Hg2+-selective chemosensor based on dithiosquarylium (DTSQ) dye was investigated. Among various metal cations tested, exclusively Hg2+ ion responses to irreversible color change of DTSQ-1, along with the Hg2+-triggered desulfurization of dithiosquarylium into its oxygen analogue squarylium (SQ) dye. 相似文献
52.
M.‐S. Kim P. A. Hohenlohe K.‐H. Kim S.‐T. Seo N. B. Klopfenstein 《Forest Pathology》2016,46(2):164-167
Raffaelea quercus‐mongolicae is a fungus associated with oak wilt and deemed to cause extensive oak mortality in South Korea. Since the discovery of this fungus on a dead Mongolian oak (Quercus mongolica) in 2004, the mortality continued to spread southwards in South Korea. Despite continued expansion of the disease and associated significant impacts on forest ecosystems, information is lacking about the origin and genetic diversity of R. quercus‐mongolicae. Restriction‐site‐associated DNA (RAD) sequencing was used to assess genetic diversity and population structure among five populations (provinces) of R. quercus‐mongolicae in South Korea. In total, 179 single nucleotide polymorphisms (SNPs) were identified among 2,639 RAD loci across the nuclear genome of the 54 R. quercus‐mongolicae isolates (0.0012 SNPs per bp), which displayed an overall low expected heterozygosity and no apparent population structure. The low genetic diversity and no apparent population structure among South Korean populations of this ambrosia beetle‐vectored fungus support the hypothesis that this fungus was introduced to South Korea. 相似文献
53.
Youn HJ Lakritz J Rottinghaus GE Seo HS Kim DY Cho MH Marsh AE 《Veterinary parasitology》2004,125(3-4):409-414
We previously reported that alcoholic extracts of Sophora flavescens and Torilis japonica from South Korea demonstrated good efficacy in reducing replication of Toxoplasma gondii and Neospora caninum. To characterize the chemical component associated with anti-protozoal activity, specific fractions were isolated by high performance liquid chromatography (HPLC) and used for in vitro testing. These fractions were evaluated in vitro against T. gondii and N. caninum. Fractions of the herb extracts were serially diluted to final concentrations of 2.850 to 0.356 ng/ml in medium and added to wells containing replicating T. gondii and N. caninum. To determine the ability of each fraction to inhibit parasite proliferation, 3H-uracil incorporation was used to determine parasite replication. In cultures infected with T. gondii, a fraction of T. japonica (TJ2) inhibited T. gondii proliferation by 99.2, 94.4, 88.6 and 27.0% in the range from 2.850 to 0.356 ng/ml. Four fractions of S. flavescens (SF1-SF4) inhibited T. gondii proliferation by 99.6-60.6, 96.9-48.1, 92.3-68.2 and 95.4-52.9% in the range from 2.850 to 0.356 ng/ml. In cultures infected with N. caninum, a fraction of T. japonica (TJ2) inhibited N. caninum proliferation by 98.3, 95.5, 79.7 and 30.6% in the range from 2.850 to 0.356 ng/ml. Four fractions of S. flavescens (SF1-SF4) inhibited N. caninum proliferation by 97.1-25.9, 94.8-35.5, 95.9-33.7 and 95.4-49.4% in the range from 2.850 to 0.356 ng/ml. These fractions of T. japonica and S. flavescens extracts are currently undergoing in vivo evaluation in experimentally infected mice. 相似文献
54.
Park SI Matthijnssens J Saif LJ Kim HJ Park JG Alfajaro MM Kim DS Son KY Yang DK Hyun BH Kang MI Cho KO 《Veterinary microbiology》2011,152(1-2):55-66
Group A rotaviruses (GARVs) cause severe acute gastroenteritis in children and young animals. Although zoonotic infections with bovine-like G6 and G8 GARVs have been reported in many countries, there is little evidence for reassortment between bovine GARVs and GARVs from heterologous species. The finding of bovine GARVs with the G6 and G8 genotypes in combination with the typical porcine P[7] prompted us to characterize all 11 genes of 30 bovine GARVs isolated from clinically infected calves. By the comparison of the full-length ORF of VP7 and NSP1-5, and the partial VP1-4 and VP6 nucleotide sequences between the 30 Korean and other known strains, three different genome constellations were found. Twenty seven strains showed the G8-P[7]-I5-R1-C1-M2-A1-N1-T1-E1-H1 genotypes, a single strain possessed the G6-P[7]-I2-R2-C1-M2-A1-N2-T1-E2-H1 genotype constellation and 2 strains the G6-P[7]-I2-R2-C2-M2-A3-N2-T6-E2-H3 genotype constellation. The complete genome of a single reference strains for each of these three genotype constellations (KJ25, KJ9-1 and KJ19-2) was determined and analyzed. A detailed phylogenetic analysis revealed a complicated picture, with several reassortments among bovine-like, porcine-like and human-like GARV strains, resulting in several different reassortant strains successfully infecting cattle. 相似文献
55.
The market demand for marine-based cosmetics has shown a tremendous growth rate in the last decade. Marine resources represent a promising source of novel bioactive compounds for new cosmetic ingredient development. However, concern about sustainability also becomes an issue that should be considered in developing cosmetic ingredients. The fisheries industry (e.g., fishing, farming, and processing) generates large amounts of leftovers containing valuable substances, which are potent sources of cosmeceutical ingredients. Several bioactive substances could be extracted from the marine by-product that can be utilized as a potent ingredient to develop cosmetics products. Those bioactive substances (e.g., collagen from fish waste and chitin from crustacean waste) could be utilized as anti-photoaging, anti-wrinkle, skin barrier, and hair care products. From this perspective, this review aims to approach the potential active ingredients derived from marine by-products for cosmetics and discuss the possible activity of those active ingredients in promoting human beauty. In addition, this review also covers the prospect and challenge of using marine by-products toward the emerging concept of sustainable blue cosmetics. 相似文献
56.
Precision Agriculture - In recent years, different algorithms have been utilised to delineate management zones, areas with similar properties, within agricultural fields. However, there are few... 相似文献
57.
Ji Hyun Kim Sophie Fridman Hamutal Borochov‐Neori Tamar Sinai Dina Zilberg 《Aquaculture Research》2019,50(2):431-438
Garlic (Allium sativum) has been shown to possess antimicrobial properties against a range of disease‐causing agents, including fish parasites. Our study aimed to investigate the potential use of garlic as a treatment against Cryptocaryon irritans infection, using guppies (Poecilia reticulata) as the fish model. Garlic was freeze‐dried, powdered, and used as it is or as an aqueous extract. The content of allicin, its main active ingredient, was 1.25 mg/g in garlic powder and 0.82 mg/ml in the aqueous extract, as determined by HPLC analysis. Aqueous garlic extract fully immobilized C. irritans theronts and protomonts within 20 and 40 min, respectively, following exposure to 5 µl/ml. Treatment trials were performed, in which infected fish were fed with garlic powder‐supplemented feeds (5%, 10%, or 20% supplementation), bathed in garlic aqueous extract (250 or 500 µl/L) and subjected to a combined treatment which included both feeding and bathing. Results revealed that the tested treatments failed to cure the infection, though reduction in infection intensity on the caudal fin, but not on the gills, was evident following dietary supplementation with 20% of powdered garlic in one of the trials. 相似文献
58.
The long-term persistence of plant populations may partly depend on pollination processes and seed production. The exact role of pollination in determining plant population viability still remains largely unclear. Orchid species have often been shown to be pollinator limited. Especially, non-rewarding species are characterized by infrequent pollinator visits and low seed set. Therefore, it can be hypothesized that, if overall population fitness of orchid species is influenced by seed production, non-rewarding species should be more prone to local extinction than rewarding species. To study the importance of nectar reward on orchid persistence, we collected historical records about the distribution of 32 orchid species in Flanders (Belgium) and 37 orchid species in the Netherlands. For both regions, present distribution patterns were compared with historical data. Between 1930 (Flanders) or 1950 (the Netherlands) and 2000, 26 (81%) species showed decreases in distribution range in Flanders, eight of which had gone extinct, whereas 29 (78%) species showed declines in distribution area in the Netherlands, five of which went extinct. Contrary to previously reported results, orchid distribution patterns were not related to nectar reward. There was also no significant relationship between nectar reward and extinction for both regions. Orchids typically occurring in wet grasslands and heathlands suffered greater losses than orchids typically confined to forest habitats or calcareous grasslands. We conclude that the production of nectar does not represent a safeguard for local extinction of orchid species. Habitat loss and other deterministic threats associated with habitat fragmentation and deterioration are more important determinants of orchid persistence. 相似文献
59.
Did incentives help municipalities recover from the Great Recession? Evidence from Midwestern cities
This study assesses the impacts of local business incentives in the largest urban areas of Illinois, Michigan, and Wisconsin, three Midwestern states that share similar histories and settings. We assembled a unique dataset combining information on two types of incentives, tax increment financing districts and tax abatements, together with socio‐economic, geographic, fiscal, and spatial competitive characteristics for all of the municipalities in six metropolitan areas. The outcome measures include employment growth, establishment formation, and business relocation. The analysis extends knowledge of the effects of economic development incentives in two ways. First, we improve upon previous research by incorporating key factors in municipal decisions to offer incentives. Second, we add to limited empirical evidence concerning local incentives following the Great Recession. Variation in the use of incentives reflects not only local decision‐making but also differing fiscal capacities and situations of adaptation to adverse economic conditions, with some governments pulling back on incentives and others initiating new approaches to retain or lure businesses. 相似文献
60.