全文获取类型
收费全文 | 31026篇 |
免费 | 1680篇 |
国内免费 | 1939篇 |
专业分类
林业 | 3273篇 |
农学 | 2705篇 |
基础科学 | 789篇 |
2265篇 | |
综合类 | 12831篇 |
农作物 | 2676篇 |
水产渔业 | 1883篇 |
畜牧兽医 | 4664篇 |
园艺 | 2753篇 |
植物保护 | 806篇 |
出版年
2024年 | 162篇 |
2023年 | 400篇 |
2022年 | 702篇 |
2021年 | 925篇 |
2020年 | 914篇 |
2019年 | 1075篇 |
2018年 | 783篇 |
2017年 | 1000篇 |
2016年 | 1329篇 |
2015年 | 1531篇 |
2014年 | 1848篇 |
2013年 | 1996篇 |
2012年 | 2460篇 |
2011年 | 2167篇 |
2010年 | 1846篇 |
2009年 | 1979篇 |
2008年 | 1631篇 |
2007年 | 1852篇 |
2006年 | 1773篇 |
2005年 | 1471篇 |
2004年 | 966篇 |
2003年 | 775篇 |
2002年 | 650篇 |
2001年 | 570篇 |
2000年 | 529篇 |
1999年 | 439篇 |
1998年 | 396篇 |
1997年 | 308篇 |
1996年 | 307篇 |
1995年 | 276篇 |
1994年 | 255篇 |
1993年 | 237篇 |
1992年 | 196篇 |
1991年 | 192篇 |
1990年 | 182篇 |
1989年 | 134篇 |
1988年 | 95篇 |
1987年 | 61篇 |
1986年 | 42篇 |
1985年 | 40篇 |
1984年 | 31篇 |
1983年 | 15篇 |
1982年 | 20篇 |
1981年 | 28篇 |
1980年 | 18篇 |
1979年 | 11篇 |
1978年 | 7篇 |
1977年 | 6篇 |
1975年 | 4篇 |
1955年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Late blight, caused by Phytophthora infestans , is an ongoing threat to potato and tomato crop production worldwide and considerable fundamental and applied research is conducted with the long-term aim of improved disease control. Understanding the mechanisms, processes and rates of P. infestans evolution is an important factor in predicting the effectiveness and durability of new management practices. A range of phenotypic and genotypic tests has been applied to achieve this goal, but each has limitations and new methods are sought. Recent progress in P. infestans genomics is providing the raw data for such methods and new high-throughput codominant biomolecular markers are currently being developed that have tremendous potential in the study of P. infestans population biology, epidemiology, ecology, genetics and evolution. This paper reviews some key applications, recommends some changes in approach and reports on the status and potential of new and existing methods for probing P. infestans genetic diversity. 相似文献
62.
用钴—60辐照处理琼胶成品和干制石花菜。经钴—60辐照的琼胶成品,其凝胶强度均有所下降,其下降率与辐照剂量大小呈正比。石花菜经钴—60辐照后,可使琼胶提取率提高,但过高的辐照剂量,也同时会降低所制取琼胶的凝胶强度。通过适宜剂量的钴60—辐照处理干制石花菜,可提高琼胶提取率3%~5%,且制取的琼胶凝胶强度不受辐照的影响。 相似文献
63.
刘新林 《安徽农业大学学报》2001,(3):59-60
企业要有生气,首先要振奋企业精神。企业英雄具有特殊的品质,体现着企业的人格。企业英雄对企业文化的发展有着功不可没的作用。成功的企业都是通过企业精神的弘扬,其中重要的手段和方法之一就是通过对英雄人物的英雄事迹的弘扬,使企业成员的精神处于一种活跃的状态。 相似文献
64.
Significant differences of callus induction, green plant regeneration and culture efficiency were observed among restorer lines and their hybrids in rice. Average callus induction percentage of F1, hybrids was about twice that of their parents. Twenty doubled haploid (DH) lines that showed normal fertility with both indica and japonica CMS lines, were selected as widely compatible restorers (WCRs). TG8 derived from CPSLO17/Minghui 63 not only showed normal fertility to both indica and japonica test varieties and CMS lines, but also exhibited superior agronomic traits, in particular short plant, desired plant type, high tillerability, large panicles, good grain quality and resistance to rice blast disease. Strong heterosis for yield was observed in crosses between indica or japonica CMS lines and TG8. TG8 possessed a dominant, widely compatible gene (WCG) that was inherited from the variety CPSLO17. Results confirmed that the anther culture technique is a quick and effective way of developing widely compatible restorers in rice and that it is applicable to the direct use of intersubspecific heterosis with the three-line method. 相似文献
65.
Variation was investigated in 110 doubled haploid (DH) lines of wheat derived from wheat × maize crosses. Field observation revealed visible variations in 15 DH2 lines such as extreme dwarfism, low seed fertility, alteration of spike type and stripes. Six agronomic traits, i.e., heading date, spike number/ plant, culm length, spike length, seed fertility and grain weight were statistically analyzed in the DH2 and DH3 generations. Out of the 88 DH2 lines/DH3 groups, 26 %/64 % showed significant differences from the parental variety in the means of one or more traits. Ranges of the DH3 lines were larger than those of the DH2 lines, except for spike number/plant. Furthermore, analyses of variance within and between DH lines showed the presence of heterogeneity/heterozygosity in the DH2 lines/plants. These results indicated the occurrence of gametoclonal variation in the DH lines. It is considered that most of the variations detected were due to the colchicine treatment rather than to the 2,4-D treatment or in vitro culture. 相似文献
66.
同许多种其它果树一样,山植属的Crataegus grayana也可应用组织培养的方法,进行快速繁殖。在加入0.25ppmBA,0.5ppmIAA以及150ppm水解干酪素的MS培养基上,可由胚得到实生苗。在加入0.5ppm和300ppm水解干酪素的MS培养基上,由茎尖与茎段可得到壮实的试管苗。由于该植物胚在第一年内成熟度甚低,因此用茎尖或茎段进行快繁殖远优于用胚来进行。从此项研究结果看,其繁殖率为2~n-3~n(n为∮月数)。 相似文献
67.
徐海祥 《湖南农业大学学报(自然科学版)》1989,16(1)
本文对于二阶椭圆型Euler方程组 -∑D_αF_(q_α~i)(x,u,Du)+F_(ui)(x,u,Du)=0得到了一些积分恒等式,利用这些恒等式证明了某些方程组非平凡解的不存在性。 相似文献
68.
CTGF, a member of the CCN family of immediate early genes, is a recently discovered profibrotic growth factor, which is involved in many pathophysiologic procedures. CTGF acts as a downstream effector of TGF-β acting on interstitial cells to enhance the progression of fibrotic renal diseases. It has been shown that CTGF gene expression can be induced or blocked by some kinds of cytokine and drugs. It is an interesting candidate target for future intervention strategies of renal interstitial fibrosis. 相似文献
70.
It is difficult to treat landfill leachate in China.Traditional biologic method and physical method always have high expenses,or cann''t reach the discharge standards.The authors use a new biologic method to treat landfill leachate,which is the Wood_microbial System from Japan.The system to be digested by 3 aeration tanks and 1 reaction tank.The comparison combine processed wool_dust broken pieces with the certain grain degree size were throw in the tanks.Dirty and organic matter are in the digest tanks through the aeration reaction and aneration reaction repeatedly.In this experiment the speed of wastewater discharge and oxygen supply has been changed, and the change of biologic system and the effect of pollutant are removed. The optimal treatment condition can be found.The experiment shows that the system has a good result,special for nitrogenous.The BOD is average to do away with the rate to amount to 90%,almost reach the second class or third class for leachate standard.But BOD loading should be not beyond 4 kg/(m 3.d),othrwise,the system will not operate in normally. 相似文献