全文获取类型
收费全文 | 17330篇 |
免费 | 97篇 |
专业分类
林业 | 3701篇 |
农学 | 1324篇 |
基础科学 | 148篇 |
2962篇 | |
综合类 | 752篇 |
农作物 | 2130篇 |
水产渔业 | 1895篇 |
畜牧兽医 | 1431篇 |
园艺 | 1123篇 |
植物保护 | 1961篇 |
出版年
2023年 | 13篇 |
2022年 | 22篇 |
2021年 | 40篇 |
2020年 | 50篇 |
2019年 | 75篇 |
2018年 | 2773篇 |
2017年 | 2740篇 |
2016年 | 1231篇 |
2015年 | 91篇 |
2014年 | 54篇 |
2013年 | 77篇 |
2012年 | 868篇 |
2011年 | 2199篇 |
2010年 | 2135篇 |
2009年 | 1281篇 |
2008年 | 1382篇 |
2007年 | 1624篇 |
2006年 | 64篇 |
2005年 | 133篇 |
2004年 | 152篇 |
2003年 | 178篇 |
2002年 | 78篇 |
2001年 | 11篇 |
2000年 | 51篇 |
1999年 | 10篇 |
1998年 | 2篇 |
1997年 | 6篇 |
1995年 | 6篇 |
1994年 | 2篇 |
1993年 | 18篇 |
1992年 | 11篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 7篇 |
1988年 | 13篇 |
1987年 | 2篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1977年 | 5篇 |
1976年 | 2篇 |
1974年 | 3篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1969年 | 1篇 |
1968年 | 4篇 |
1967年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
101.
Maymó AC Cervera A Sarabia R Martínez-Pardo R Garcerá MD 《Pest management science》2002,58(9):928-934
The western flower thrips Frankliniella occidentalis (Pergande) is a very significant pest of a number of different agricultural crops in the south-east of Spain. The importance of thrips as a pest is not due mainly to the direct damage inflicted on the plant, but to the loss in commercial value which occurs as a consequence of the development of dark spots caused by the tomato spotted wilt virus (TSWV) which they transmit. The economic threshold is therefore almost zero, which enhances the problems of resistance management. The present work is part of a global project that attempts to evaluate the status of insecticide resistance in field populations of thrips obtained from several agricultural crops. We have studied, in either individual or pooled insects, some enzyme systems classically related to detoxification of insecticides: esterase and glutathione-S-transferase (GST). The activity of these enzymes from laboratory populations selected with various classes of insecticides has also been measured using several appropriate substrates. An increase in GST mean activity was found in two field-collected strains. Differences in frequency distributions of esterase and GST activities were found for both field-collected strains and for a laboratory strain selected with acrinathrin. These activities were compared with those of a wild-type reference strain. 相似文献
102.
Tateyama S Molina HA Uchida K Yamaguchi R Manuel MF 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2000,62(4):439-442
An epizootiological survey of necropsied cases (1993-1997) at University of the Philippines was performed. A total of 368 cases included 238 avian and 111 porcine cases. Amongst avian cases, the major cause of death was infectious diseases in 212 (89%) cases including 97 (41%) bacterial, 36 (15%) viral, and 21(9%) parasitic diseases. The majority of the avian bacterial diseases presented as septicemia (73 cases) and the viral diseases as Newcastle disease (17 cases). In porcine cases, the major cause of death was also infectious diseases, in 100 (90%) cases including 52 bacterial and 29 viral diseases. Porcine bacterial diseases were classified into 36 septicemia, 4 hemophillosis and 4 colibacillosis. Amongst the porcine viral diseases, most cases were diagnosed as Hog cholera (22 cases). 相似文献
103.
Maria Victoria Carapeto DVM Rafael Barrera DVM PhD Maria Cinta Mae DVM PhD Concepcin Zaragoza DVM PhD 《Journal of Equine Veterinary Science》2006,26(3):120-127
Serum electrophoresis is a useful technique to diagnose some diseases characterized by quantitative and qualitative changes in the serum proteins, such as the acute phase proteins. An increased synthesis of acute phase proteins has been associated with acute infection and inflammation. We wanted to study whether gastrointestinal diseases and disorders of the locomotor system in horses produce enough inflammatory reaction so the acute phase proteins can be detected by electrophoresis in serum. Serum total proteins were calculated, and the serum electrophoresis from 63 horses was performed. The horses were classified in 3 groups: Group I (19 healthy horses), Group II (20 horses suffering from inflammatory disorders of the gastrointestinal tract), and Group III (24 horses with inflammatory disorders of the locomotor system). Results indicated an increase of the acute phase proteins only in patent inflammatory disorders that showed a rapid progression. A global increase in those proteins was observed only for α1-globulins from Group II. 相似文献
104.
Leila Feiz Muhammad Irshad Rafael F Pont-Lezica Hervé Canut Elisabeth Jamet 《Plant methods》2006,2(1):10-13
Background
The ultimate goal of proteomic analysis of a cell compartment should be the exhaustive identification of resident proteins; excluding proteins from other cell compartments. Reaching such a goal closely depends on the reliability of the isolation procedure for the cell compartment of interest. Plant cell walls possess specific difficulties: (i) the lack of a surrounding membrane may result in the loss of cell wall proteins (CWP) during the isolation procedure, (ii) polysaccharide networks of cellulose, hemicelluloses and pectins form potential traps for contaminants such as intracellular proteins. Several reported procedures to isolate cell walls for proteomic analyses led to the isolation of a high proportion (more than 50%) of predicted intracellular proteins. Since isolated cell walls should hold secreted proteins, one can imagine alternative procedures to prepare cell walls containing a lower proportion of contaminant proteins. 相似文献105.
An introductory study was conducted to investigate the pyrethroid resistance ofHelicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) strains in Turkey, collected from cotton fields in the Adana and Antalya provinces, through
two different synthetic pyrethroid insecticides: lambda-cyhalothrin and esfenvalerate. In addition, the roles of glutathioneS-transferases (GSTs) in this resistance mechanism were analyzed. It was found that whereas resistance ratios for lambda-cyhalothrin
(LD50 levels) were 3- and 98-fold increased in the Adana and Antalya strains, respectively, esfenvalerate ratios were 3.3- and
92.3-fold increased in the Adana and Antalya strains, respectively, with respect to the susceptible strain. Furthermore, Adana
and Antalya strains showed 2.4- and 2.9-fold higher GST activities than the susceptible strain, respectively. In the Antalya
field strain, the minor increase in GST activity compared with the resistance levels implies that GSTs may be not greatly
involved in this resistance. It also provides evidence that they could not be the only metabolic mechanism responsible for
resistance to lambda-cyhalothrin and esfenvalerate inH. armigera from Turkey.
http://www.phytoparasitica.org posting Nov. 16, 2006. 相似文献
106.
107.
M. Lodovica Gullino Riccardo Savigliano Giuliana Gasparrini Corrado Clini 《Phytoparasitica》2007,35(4):321-329
Methyl bromide (MB) was phased out on January 1, 2005, and a Critical Use Exemption (CUE) process has been established in
order to define the rules for allocating the needed amounts of the fumigant. This paper deals with the effects of the CUE
process on Italian horticulture. The actual usage of the amounts of MB allocated to Italy for the year 2005 in the different
areas and on the economically most important crops was monitored and critically evaluated. The usage pattern monitored shows
that already in the first year after MB phaseout, Italy was able to replace it completely on crops such as zucchini, salad
greens, basil and watermelon. However, on crops such as tomato, pepper, melon, eggplant, strawberry, and cut flowers, further
work is required in order fully to replace MB. The emerging problems and research needs are discussed briefly. 相似文献
108.
David White Weidong Chen 《European journal of plant pathology / European Foundation for Plant Pathology》2007,119(1):3-12
Ascochyta blight is a serious disease of cool-season grain legumes (chickpea, faba bean, lentil and pea) caused by fungal
species of the anamorphic genus Ascochyta and related genera. Despite extensive studies on the biology, ecology, epidemiology
and management of the disease, little is known about the pathogenic determinants of these pathogens. This research aims at
using Ascochyta rabiei as a model for the genus in investigating genetic factors of pathogenicity, with the ultimate goal of elucidating pathogenic
mechanisms. Three advances were made: (1) insertional mutants with altered pathogenicity were identified through in vivo screening,
and genomic regions adjacent to the insertion sites in selected mutants were determined; (2) a phage library of A. rabiei genomic DNA was constructed, and the library was estimated to provide complete coverage of the A. rabiei genome. This library was used successfully to recover clones with DNA adjacent to insertional mutation sites and to isolate
specific genes; (3) DNA probes specific for an acyl-CoA ligase (cps1) and a polyketide synthase gene (pks1) were developed and library clones containing the corresponding genomic regions were identified from the phage library.
These advances provide the foundation and necessary tools for experimentation of ectopic complementation assays and targeted
mutagenesis to elucidate the genetic mechanisms of pathogenicity of A. rabiei. 相似文献
109.
如果管理得当,给哺乳期的仔猪补充乳可获得多方面的好处。为获得高断奶窝重而对母猪进行高繁殖性能和高营养需求的选择已使饲喂现代的母猪品种成为商业化养猪场中技术最先进的工作。如果青年母猪要 相似文献
110.
Simulating the cumulative effects of multiple forest management strategies on landscape measures of forest sustainability 总被引:1,自引:2,他引:1
While the cumulative effects of the actions of multiple owners have long been recognized as critically relevant to efforts
to maintain sustainable forests at the landscape scale, few studies have addressed these effects. We used the HARVEST timber
harvest simulator to predict the cumulative effects of four owner groups (two paper companies, a state forest and non-industrial
private owners) with different management objectives on landscape pattern in an upper Michigan landscape managed primarily
for timber production. We quantified trends in landscape pattern metrics that were linked to Montreal Process indicators of
forest sustainability, and used a simple wildlife habitat model to project habitat trends. Our results showed that most trends
were considered favorable for forest sustainability, but that some were not. The proportion of all age classes and some forest
types moved closer to presettlement conditions. The trend for the size of uneven-aged patches was essentially flat while the
average size of patches of the oldest and youngest age classes increased and the size of patches of the remaining age classes
decreased. Forest fragmentation generally declined, but edge density of age classes increased. Late seral forest habitat increased
while early successional habitat declined. The owners use different management systems that cumulatively produce a diversity
of habitats. Our approach provides a tool to evaluate such cumulative effects on other landscapes owned by multiple owners.
The approach holds promise for helping landowner groups develop and evaluate cooperative strategies to improve landscape patterns
for forest sustainability. 相似文献