全文获取类型
收费全文 | 3837篇 |
免费 | 214篇 |
国内免费 | 311篇 |
专业分类
林业 | 245篇 |
农学 | 446篇 |
基础科学 | 38篇 |
151篇 | |
综合类 | 1622篇 |
农作物 | 628篇 |
水产渔业 | 16篇 |
畜牧兽医 | 108篇 |
园艺 | 211篇 |
植物保护 | 897篇 |
出版年
2024年 | 11篇 |
2023年 | 76篇 |
2022年 | 138篇 |
2021年 | 138篇 |
2020年 | 130篇 |
2019年 | 140篇 |
2018年 | 89篇 |
2017年 | 100篇 |
2016年 | 180篇 |
2015年 | 154篇 |
2014年 | 202篇 |
2013年 | 196篇 |
2012年 | 238篇 |
2011年 | 253篇 |
2010年 | 197篇 |
2009年 | 201篇 |
2008年 | 197篇 |
2007年 | 174篇 |
2006年 | 170篇 |
2005年 | 141篇 |
2004年 | 166篇 |
2003年 | 127篇 |
2002年 | 94篇 |
2001年 | 118篇 |
2000年 | 97篇 |
1999年 | 82篇 |
1998年 | 72篇 |
1997年 | 60篇 |
1996年 | 57篇 |
1995年 | 66篇 |
1994年 | 32篇 |
1993年 | 50篇 |
1992年 | 41篇 |
1991年 | 49篇 |
1990年 | 33篇 |
1989年 | 18篇 |
1988年 | 25篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1978年 | 3篇 |
1963年 | 1篇 |
1962年 | 1篇 |
1956年 | 1篇 |
1955年 | 5篇 |
排序方式: 共有4362条查询结果,搜索用时 343 毫秒
81.
82.
观察了捕食线虫性真菌——少孢节丛孢菌的超微结构,以探讨捕食线虫性真菌的杀虫机理。结果显示,少孢节丛孢菌属于隔膜类真菌,隔膜中央有孔,菌丝细胞一般呈长形竹节状;菌株的捕食器为黏性菌环和菌网,形成捕食器的菌丝细胞结构不同于一般的营养菌丝,胞质中含有许多电子密集体,呈大小不等的黑色类圆形颗粒状,多数排列在捕食器菌丝细胞的边缘区域,这是捕食线虫性真菌捕食器菌丝细胞的一个重要特征。 相似文献
83.
The pathogenicity of Alternaria spp. isolated from wheat leaves collected in regions where alternaria leaf blight has been reported was compared with that of IMI reference isolates of A. triticina and A. alternata using two durum and two bread wheat genotypes. To identify isolates putatively corresponding to A. triticina , morphological and DNA sequence analyses based on ribosomal DNA from the internal transcribed spacer (ITS) region (ITS1, 5·8S rRNA gene, ITS2) and toxicity bioassays of culture filtrate were combined. Glasshouse inoculations provided reliable information to assess the pathogenicity of A. triticina isolates on wheat. Alternaria leaf blight symptoms were produced by the A. triticina isolates only on durum wheat cv. Bansi, while A. alternata , A. tenuissima and A. arborescens isolates were found to be nonpathogenic on the wheat cultivars tested. Alternaria triticina isolates were distinguished from other Alternaria species by Simmons and Roberts' sporulation pattern 6 and two to three conidia per sporulation unit associated with primary conidia bearing long (> 7 µ m) apical secondary conidiophores. Phylogenetic analysis also proved effective at discriminating wheat-pathogenic A. triticina from other nonpathogenic Alternaria species. Alternaria triticina isolates yielded longer ITS sequences than A. alternata , A. tenuissima and A. arborescens isolates, leading to clear-cut differences as visualized with agarose gel electrophoresis. Additionally, only culture filtrates of A. triticina isolates caused nonspecific necrotic lesions on leaves of 3-week-old wheat plants. 相似文献
84.
Genotypic diversity in Fusarium pseudograminearum and F. graminearum from Australia and the relationship between diversity and pathogen aggressiveness for head blight and/or crown rot of wheat were examined. Amplified fragment length polymorphism (AFLP) analysis revealed a high level of genotypic diversity within each species. Sixty-three of the 149 AFLP loci were significantly different between the two species and 70 of 72 F. pseudograminearum and 56 of 59 F. graminearum isolates had distinct haplotypes. When head blight and crown rot severity data from a recently published work on isolates representing the entire range of aggressiveness were used, only the genotypic diversity of F. pseudograminearum was significantly associated with its aggressiveness for the two diseases. Cluster analyses clearly demonstrated the polyphyletic structures that exist in both pathogen populations. The spatial diversity within F. graminearum was high within a single field, while frequent gene flow ( N m ∼ 14) and a low fixation index ( G st = 0·03) were recorded among F. pseudograminearum isolates from the adjacent states of New South Wales and Queensland. The differences in population structure between the heterothallic F. pseudograminearum (teleomorph G. coronicola ) and the homothallic F. graminearum (teleomorph G. zeae ) were not as pronounced as expected given their contrasting mating systems. Neither species was panmictic or strictly clonal. This points to sexual recombination in F. pseudograminearum , suggesting that ascospores of G. coronicola may also play a role in its biology and epidemiology. 相似文献
85.
Alternaria solani causes diseases on foliage (early blight), basal stems of seedlings (collar rot), stems of adult plants (stem lesions), and
fruits (fruit rot) of tomato. Early blight is the most destructive of these diseases and hence receives considerable attention
in breeding. For over 60 years, breeding for early blight resistance has been practiced, but the development of cultivars
with high levels of resistance has been hampered by the lack of sources of strong resistance in the cultivated tomato and
by the quantitative expression and polygenic inheritance of the resistance. In some accessions of wild species, high levels
of early blight resistance have been found, but breeding lines still have unfavorable horticultural traits from the donor
parent. Recently, the first linkage maps with loci controlling early blight resistance have been developed based on interspecific
crosses. These maps may facilitate marker-assisted selection. This overview presents the current knowledge about the A. solani–tomato complex with respect to its biology, genetics, and breeding. 相似文献
86.
Kazunori Fuke Naofumi Hozumi Yoshinari Enami Kazuho Matsuura Akitoshi Tajimi 《Journal of General Plant Pathology》2006,72(1):74-75
Anthracnose disease was found on centipede grass [Eremochloa ophiuroides (Munro) Hack.] planted as a ground cover on paddy field levees in Shiga Prefecture in 2004. The symptoms were ear blight,
stalk blight, and leaf spots. The causal fungus was morphologically identified as Colletotrichum caudatum (Sacc.) Peck. This is the first report of centipede grass anthracnose caused by C. caudatum. 相似文献
87.
88.
通过对不同种植时间、不同种植基质的香根草Vetiveria zizanioides分株苗、组培苗根际丛枝菌根(AM菌)感染检测,探讨了香根草对AM菌的感染特性.结果表明,在消过毒的森林泥炭土中,组培苗种植12个月感染率只有20.0%,感染强度低;种植22个月只有53.3%,感染强度为中.分株苗种植在自然土壤中,3个月就有AM菌感染,其感染率为56.7%;种植22个月感染率达到最高峰,为80.0%,感染强度为中等;种植时间为33个月时,感染率不再增加,但感染强度进一步增高.说明香根草根际AM菌的感染率和感染强度可能与苗源无关,而与种植基质密切相关. 相似文献
89.
对广东省将推广的54份杂交稻组合对稻瘟病和白叶枯病的抗病性进行了鉴定。对稻瘟病的抗病性鉴定表明:抗病组合共49个,占90.7%;其中,高抗(抗性比≥91%)组合30个,占55.6%。对稻白叶枯病的抗病性鉴定表明:没有高抗(HR)和抗(R)的组合,仅有一个杂交稻组合(西胜2175)表现为中抗(mR),仅占1.9%,其余53个组合都表现感病,占98.1%。进一步分析表明:对稻瘟病表现高抗的30个杂交稻组合都不抗白叶枯病,而中抗白叶枯病的杂交稻组合西胜2175对稻瘟病表现为中抗,抗性比为74%。 相似文献
90.
采用无菌技术从银杏茎中分离到一株内生真菌(No.1028),经形态分类学和rDNAITS序列分析研究鉴定为黑孢属Nigrosporasp.,菌丝生长速率法测定结果表明,其代谢产物对重要作物真菌病害病原菌具有明显的抑制作用。离体条件下内生真菌发酵液对番茄早疫病菌、黄瓜枯萎病菌、菜豆炭疽病菌、葡萄炭疽病菌、水稻纹枯病菌、黄瓜立枯病菌均有较强的抑制作用,对上述不同病原菌的抑制率分别为66.7%、48.3%、64.6%、36.5%、57.1%和23.0%。经提取分离得到纯的白色晶体状活性物质。同时也研究了不同碳源、氮源、无机离子对内生真菌No.1028生物学特性和生长的影响,发现玉米粉、黄豆饼粉比较适合其生长和抑菌代谢产物的合成,Na 对抑菌代谢产物的合成有较明显的促进作用。 相似文献