全文获取类型
收费全文 | 8915篇 |
免费 | 585篇 |
国内免费 | 50篇 |
专业分类
林业 | 555篇 |
农学 | 463篇 |
基础科学 | 80篇 |
1586篇 | |
综合类 | 633篇 |
农作物 | 436篇 |
水产渔业 | 676篇 |
畜牧兽医 | 4187篇 |
园艺 | 122篇 |
植物保护 | 812篇 |
出版年
2023年 | 84篇 |
2022年 | 136篇 |
2021年 | 278篇 |
2020年 | 266篇 |
2019年 | 333篇 |
2018年 | 315篇 |
2017年 | 330篇 |
2016年 | 335篇 |
2015年 | 235篇 |
2014年 | 319篇 |
2013年 | 499篇 |
2012年 | 509篇 |
2011年 | 558篇 |
2010年 | 280篇 |
2009年 | 317篇 |
2008年 | 449篇 |
2007年 | 444篇 |
2006年 | 386篇 |
2005年 | 367篇 |
2004年 | 347篇 |
2003年 | 303篇 |
2002年 | 339篇 |
2001年 | 241篇 |
2000年 | 243篇 |
1999年 | 209篇 |
1998年 | 58篇 |
1997年 | 61篇 |
1996年 | 56篇 |
1995年 | 54篇 |
1994年 | 38篇 |
1993年 | 40篇 |
1992年 | 80篇 |
1991年 | 54篇 |
1990年 | 64篇 |
1989年 | 70篇 |
1988年 | 65篇 |
1987年 | 53篇 |
1986年 | 49篇 |
1985年 | 60篇 |
1984年 | 39篇 |
1983年 | 42篇 |
1982年 | 30篇 |
1980年 | 23篇 |
1979年 | 37篇 |
1978年 | 21篇 |
1977年 | 21篇 |
1974年 | 23篇 |
1973年 | 25篇 |
1972年 | 24篇 |
1970年 | 26篇 |
排序方式: 共有9550条查询结果,搜索用时 15 毫秒
951.
952.
953.
Growth and photochemical response of triazine-susceptible and -resistant rutabaga ‘Laurentian’ genotypes to cyanazine (chloro-s-triazine) and metribuzin (methylthio-as-triazine) were evaluated. The young seedlings of the susceptible rutabaga were killed when cyanazine or metribuzin were applied either pre- or post-emergence. The triazine-resistant rutabaga, however, displayed a differential response to these herbicides. Metribuzin applied pre-emergence killed the seedlings at 0.4 kg ha?1, and at 0.2 kg ha?1 the growth was severely affected. Cyanazine even at higher rates applied pre- or post-emergence failed to inhibit growth in these plants.Chlorophyll fluorescence in leaf sections at the cotyledonary, 2-leaf and 4-leaf stages in the susceptible plants increased by 130 and 172% in response to 10?5 M cyanazine and metribuzin, respectively, suggesting that Photosystem II reactions in these plants were severely impaired. In resistant plants, there was little or no leaf chlorophyll fluorescence (LCF) increase at this herbicide concentration. However, at 10?4 M cyanazine and metribuzin, the LCF in resistant plants increased significantly and the increase was greater in response to metribuzin (86%) than to cyanazine (51%). This indicates that with these triazine-resistant genotypes, metribuzin is relatively more potent and at high rates is capable of interfering with photosynthesis. 相似文献
954.
Twenty-nine new records are reported from Turkey. The fungi species, including their macro-and microscopic features and distributions,
are described.
http://www.phytoparasitica.org posting July 14, 2004. 相似文献
955.
Eggs and L1 nymphs of the greenhouse whiteflyTrialeurodes vaporariorum (Westwood) (Hem.: Aleyrodidae) on bean leaves were directly sprayed with the fungicides maneb and mancozeb at recommended
rates for practical use. Strong ovicidal and nymphicidal effects were observed. These fungicides may prove to have practical
use for integration in IPM programs for whitefly control, as they also exert low or no toxicity to the whitefly parasitoidEncarsia formosa.
http://www.phytoparasitica.org posting April, 30, 2004. 相似文献
956.
N.?VovlasEmail author N.?J.?O.?Sim?es N.?Sasanelli M.?C.?V.?dos?Santos I.?M.?de?O.?Abrantes 《Phytoparasitica》2004,32(2):167-173
During a nematode survey, severe infections of tobacco feeder roots and heavy soil infestations byMeloidogyne incognita race 1 were found in S. Miguel (Azores islands, Portugal). This is the first record ofM. incognita infection of tobacco in Azores. Morphology of various life stages, analysis of the esterase electrophoretic pattern and differential
host tests were used for nematode characterization and identification. Nematode-induced mature galls were spherical and/or
ellipsoidal and usually contained more than one female, males and egg masses with eggs. Feeding sites were characterized by
the development of giant cells that contained granular cytoplasm and many hypertrophied nuclei. Giant cell cytoplasm was aggregated
along a thickened cell wall. Vascular tissues within galls appeared disorganized. The relationship between the initial nematode
population density and growth of tobacco plants was tested in a glasshouse experiment in which inoculum levels varied from
0 to 512 eggs and juveniles (J2) cm−3 of soil. Seinhorst’s model was fitted to height and top fresh weight data of the inoculated and control plants. Tolerance
limits with respect to plant height and fresh top weight of tobacco cv. ‘Erzegovina’ plants toM. incognita race 1 were estimated as 1.25 eggs and J2 cm−3 of soil. The maximum nematode reproduction rate was 404.7 at an initial population density of 4 eggs and J2 cm−3 of soil.
http://www.phytoparasitica.org posting March 2, 2004. 相似文献
957.
958.
Matthias?FladungEmail author Olaf?Nowitzki Birgit?Ziegenhagen Torsten?Markussen 《Wood Science and Technology》2004,38(3):207-215
We have extracted total DNA from different fractions of fresh wood as well as from cold-stored and air-dried wood harvested from transgenic aspen grown in the field. The highest amounts of DNA were obtained from bark/cambium tissue; the DNA quality, however, was poor. Best results in PCR and Southern blot analyses were obtained from DNA extracted from early wood. Using appropriate primer pairs, amplification products were obtained from both the foreign gene (transgene) and aspen genomic sequences. In Southern blot analyses transgene-specific hybridisation signals were obtained. This is the first report on the detection of foreign genes in wood sampled from genetically modified trees. 相似文献
959.
The Fusarium species are a group of saprophytic fungal organisms that are occasionally the cause of opportunistic infections in humans and animals. Central nervous system disease associated with a Fusarium species is most commonly described in horse, resulting in equine leukoencephalomalacia. This report describes a 2-year-old, spayed, female German Shepherd Dog with meningoencephalitis secondary to infection with Fusarium spp. Meningoencephalitis in dogs secondary to a species of Fusarium has not been previously reported. The diagnosis was made based on the histopathologic examination of brain tissues postmortem and special immunohistochemical stains specific for Fusarium solani. The clinical signs in this dog were indicative of multifocal brain disease and included seizures and a paradoxical vestibular syndrome. The clinical findings, diagnostic and histopathologic test results, and the comparative characterizations of other disseminated fungal diseases, especially aspergillosis, are described. 相似文献
960.
Clinical signs, humoral and cellular immune responses, and microscopic and gross tissue alterations resulting from acute experimental Ehrlichia canis infection in dogs were studied. Four dogs were inoculated with E. canis and four were used as uninfected controls. After a 10-14-day incubation period, infected dogs developed pyrexia up to 41 degrees C for 6-8 days. Antibody titers to E. canis antigen were demonstrable in all inoculated dogs at 30 days post-infection. Necropsy of infected animals revealed pale mucous membranes, generalized lymphadenopathy, splenomegaly, edema and ascites. Microcopically, the main lesions were: lymphoreticular hyperplasia in cortical areas of lymph nodes and spleenic white pulp, periportal accumulation of mononuclear cells and centrolobular fatty degeneration of the liver. Kidneys presented with glomerulonephritis characterized by interstitial mononuclear infiltration. Immunophenotyping of lymphocytes from lymph nodes and spleen sections displayed alterations in IgG, IgM, CD3+ and CD8+ cells population in infected dogs. 相似文献