全文获取类型
收费全文 | 19006篇 |
免费 | 205篇 |
国内免费 | 264篇 |
专业分类
林业 | 3793篇 |
农学 | 1482篇 |
基础科学 | 312篇 |
3165篇 | |
综合类 | 1698篇 |
农作物 | 2289篇 |
水产渔业 | 1949篇 |
畜牧兽医 | 1560篇 |
园艺 | 1232篇 |
植物保护 | 1995篇 |
出版年
2024年 | 25篇 |
2023年 | 60篇 |
2022年 | 160篇 |
2021年 | 175篇 |
2020年 | 143篇 |
2019年 | 171篇 |
2018年 | 2862篇 |
2017年 | 2891篇 |
2016年 | 1278篇 |
2015年 | 199篇 |
2014年 | 147篇 |
2013年 | 169篇 |
2012年 | 982篇 |
2011年 | 2333篇 |
2010年 | 2293篇 |
2009年 | 1400篇 |
2008年 | 1428篇 |
2007年 | 1708篇 |
2006年 | 118篇 |
2005年 | 173篇 |
2004年 | 151篇 |
2003年 | 178篇 |
2002年 | 93篇 |
2001年 | 53篇 |
2000年 | 85篇 |
1999年 | 27篇 |
1998年 | 13篇 |
1997年 | 15篇 |
1996年 | 14篇 |
1995年 | 7篇 |
1994年 | 11篇 |
1993年 | 24篇 |
1992年 | 13篇 |
1991年 | 9篇 |
1990年 | 11篇 |
1989年 | 14篇 |
1988年 | 19篇 |
1987年 | 6篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1977年 | 4篇 |
1972年 | 1篇 |
1969年 | 1篇 |
1968年 | 4篇 |
1967年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
1.
2.
采用定量分析与定性分析相结合的理论研究方式,通过景观评价要素筛选和专家打分,确定各个景观要素影响因子的初步权重,并运用网络层次分析法(ANP)分析汉回村作为长沙唯一的少数民族村落景观的合理性,揭示汉回村景观特色主导元素,同时对少数民族与汉族的融合地区乡村景观进行评价,旨在为乡村景观评价提供参考。研究结果表明汉回村乡村景观优势类型:民俗文化景观>自然生态景观>农业产业景观>建筑聚落景观,应保持与发展民俗文化景观优势,改善建筑聚落景观劣势。 相似文献
3.
4.
5.
A. Schots J. De Boer A. Schouten J. Roosien J. F. Zil Verentant H. Pomp L. Bouwman-Smits H. Overmars F. J. Gommers B. Visser W. J. Stiekema J. Bakker 《European journal of plant pathology / European Foundation for Plant Pathology》1992,98(2):183-191
Engineering resistance against various diseases and pests is hampered by the lack of suitable genes. To overcome this problem we started a research program aimed at obtaining resistance by transfecting plants with genes encoding monoclonal antibodies against pathogen specific proteins. The idea is that monoclonal antibodies will inhibit the biological activity of molecules that are essential for the pathogenesis. Potato cyst nematodes are chosen as a model and it is thought that monoclonal antibodies are able to block the function of the saliva proteins of this parasite. These proteins are, among others, responsible for the induction of multinucleate transfer cells upon which the nematode feeds. It is well documented that the ability of antibodies to bind molecules is sufficient to inactivate the function of an antigen and in view of the potential of animals to synthesize antibodies to almost any molecular structure, this strategy should be feasible for a wide range of diseases and pests.Antibodies have several desirable features with regard to protein engineering. The antibody (IgG) is a Y-shaped molecule, in which the domains forming the tips of the arms bind to antigen and those forming the stem are responsible for triggering effector functions (Fc fragments) that eliminate the antigen from the animal. Domains carrying the antigen-binding loops (Fv and Fab fragments) can be used separately from the Fc fragments without loss of affinity. The antigen-binding domains can also be endowed with new properties by fusing them to toxins or enzymes. Antibody engineering is also facilitated by the Polymerase Chain Reaction (PCR). A systematic comparison of the nucleotide sequence of more than 100 antibodies revealed that not only the 3′-ends, but also the 5′-ends of the antibody genes are relatively conserved. We were able to design a small set of primers with restriction sites for forced cloning, which allowed the amplification of genes encoding antibodies specific for the saliva proteins ofGlobodera rostochiensis. Complete heavy and light chain genes as well as single chain Fv fragments (scFv), in which the variable parts of the light (VL) and heavy chain (VH) are linked by a peptide, will be transferred to potato plants. A major challenge will be to establish a correct expression of the antibody genes with regard to three dimensional folding, assembly and intracellular location. 相似文献
6.
Shohei MATSUURA Shigeru HOSHINO Hideaki HAYASHI Tetsuyuki KOHGUCHI Kyoji HAGIWARA Toshihiro OMURA 《Journal of General Plant Pathology》2002,68(1):99-102
DAS-ELISA proved to be reliable enough to detect a latent infection by Tomato spotted wilt virus (TSWV) in asymptomatic stock plants of chrysanthemum. A high density of Frankliniella occidentalis, the predominant vector, in the presence of latently infected stock plants resulted in a high incidence of disease in the chrysanthemum
production field. The incidence of disease was low when the vector thrips were not abundant in spite of the presence of latently
infected stock plants. These results suggest that an infestation of the vector thrips causes severe secondary spread of TSWV
originating from latently infected stock plants in chrysanthemum production fields.
Received 27 July 2001/ Accepted in revised form 27 November 2001 相似文献
7.
8.
Eiji Tanaka Chihiro Tanaka Atsushi Ishihara Yasumasa Kuwahara Mitsuya Tsuda 《Journal of General Plant Pathology》2003,69(1):1-6
Aciculosporium take (Ascomycota; Clavicipitaceae) is a causal agent of witches' broom of
bamboo plants. The symptoms of this disease are believed to be induced by plant
hormones, particularly auxins. Indole-3-acetic acid (IAA) was identified in
cultures of this fungus in an l-tryptophan-supplemented liquid medium.
IAA production was confirmed on 30 isolates of A. take from various
hosts and locations at levels up to 1 mg/l. The biosynthetic pathway of
IAA in A. take culture was examined by analyzing intermediate products
and by feeding experiments. The results showed that the indole-3-pyruvic acid
pathway (l-tryptophan → indole-3-pyruvic acid → indole
acetaldehyde → IAA) was the dominant pathway in A. take.
Received: June 3, 2002 / Accepted: July 25, 2002 相似文献
9.
Hiromitsu Furuya Tsutomu Matsumoto Shin-ichi Fuji Hideki Naito 《Journal of General Plant Pathology》2003,69(2):115-119
Rice seedling growth, estimated by plant height and root development and discoloration, was better in pasteurized soil than
in unpasteurized soil obtained from a flooded rice field. Rice seedlings also grew better in sterilized soil modified by adding
roots harvested from the pasteurized soil than in soil modified by adding roots harvested from the unpasteurized soil. The
results demonstrate that seedling growth in the rice field soil was inhibited by soil microorganisms, even though no typical
symptoms such as seedling blight or damping-off appeared. Pythium aristosporum is suggested to be involved in the inhibition. Thus, it appears that inconspicuous restraint of rice seedling growth could
occur in soils of rice paddy fields.
Received: May 20, 2002 / Accepted: October 16, 2002
Acknowledgments The authors thank Dr. T. Ichitani, former professor at Osaka Prefectural University, for providing an isolate of Pythium aristosporum for comparison, and Mr. Mitsuaki Sato of Akita Prefectural College of Agriculture for technical assistance. 相似文献
10.
我国南方稻区稗草对二氯喹啉酸的抗药性测定 总被引:8,自引:0,他引:8
用琼脂法对2000年和2001年采收的29个稗草生态型对二氯喹啉酸的抗性水平进行了测定。结果表明:广东花都稗草对二氯喹啉酸最为敏感,其抑制中浓度IC50是0.148 0 mg/L;湖南安乡稗草对二氯喹啉酸的抗性极为明显,2000年和2001年样本IC50值分别是7.458和13.80 mg/L,其相对抗性比分别为50.4和93.2;2000年采收的湖南常德稗草也对二氯喹啉酸表现出高抗,其相对抗性比值是4.47,黄梅、汉寿、常德(b)、高桥4地稗草也表现出抗性,其相对抗性比值分别为2.37、3.12、2.44和2.20;其他22个稗草生态型对二氯喹啉酸仍未表现出抗性。 相似文献