全文获取类型
收费全文 | 23344篇 |
免费 | 405篇 |
国内免费 | 860篇 |
专业分类
林业 | 4466篇 |
农学 | 2361篇 |
基础科学 | 652篇 |
3799篇 | |
综合类 | 2839篇 |
农作物 | 2509篇 |
水产渔业 | 2082篇 |
畜牧兽医 | 2217篇 |
园艺 | 1355篇 |
植物保护 | 2329篇 |
出版年
2024年 | 30篇 |
2023年 | 117篇 |
2022年 | 252篇 |
2021年 | 332篇 |
2020年 | 333篇 |
2019年 | 312篇 |
2018年 | 2927篇 |
2017年 | 2976篇 |
2016年 | 1441篇 |
2015年 | 385篇 |
2014年 | 369篇 |
2013年 | 419篇 |
2012年 | 1225篇 |
2011年 | 2588篇 |
2010年 | 2562篇 |
2009年 | 1677篇 |
2008年 | 1672篇 |
2007年 | 1961篇 |
2006年 | 380篇 |
2005年 | 378篇 |
2004年 | 254篇 |
2003年 | 306篇 |
2002年 | 206篇 |
2001年 | 181篇 |
2000年 | 192篇 |
1999年 | 164篇 |
1998年 | 144篇 |
1997年 | 114篇 |
1996年 | 114篇 |
1995年 | 104篇 |
1994年 | 91篇 |
1993年 | 84篇 |
1992年 | 65篇 |
1991年 | 61篇 |
1990年 | 43篇 |
1989年 | 48篇 |
1988年 | 42篇 |
1987年 | 14篇 |
1986年 | 10篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1977年 | 4篇 |
1969年 | 1篇 |
1968年 | 4篇 |
1967年 | 1篇 |
1965年 | 2篇 |
1964年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
不同脱粒与干燥方式对稻米品质的影响 总被引:8,自引:0,他引:8
选用代表型品种 (组合 )南京 16 (代表中稻 )、金优 2 0 7(代表晚稻籼型 )、鄂宜 10 5(代表晚稻粳型 )进行不同的脱粒与干燥处理 ,以考察不同处理对稻米品质的影响。脱粒方式处理分为人工链杆击打、拖拉机带动石磙碾落和联合收割机脱粒 ;干燥方式处理分为在水泥地上自然晒干、放在竹垫上自然晒干和机械通风干燥。两种处理共交叉组合成 9种交叉处理。结果表明 ,不同脱粒与干燥处理对米质中的整精米率和垩白度指标影响最大。其中 ,脱粒方式对稻米整精米率的影响较大 ,同时对南京 16垩白度的影响较大 ;干燥方式对金优 2 0 7和晚粳鄂宜 10 5垩白度的影响较大 ;两种处理方式之间互作效应显著 ,最佳组合处理为联合收割机脱粒加机械通风干燥处理。不同处理方式对中稻品种南京 16米质的影响要大于对晚粳鄂宜 10 5和晚杂组合金优2 0 7。 相似文献
72.
Soybean oil content QTL mapping and integrating with meta-analysis method for mining genes 总被引:2,自引:0,他引:2
Zhao-ming Qi Qiong Wu Xue Han Ya-nan Sun Xiang-yu Du Chun-yan Liu Hong-wei Jiang Guo-hua Hu Qing-shan Chen 《Euphytica》2011,179(3):499-514
Oil content of soybean was a valuable quantitative trait controlled by multiple genes. Eleven QTLs were detected by both CIM
and MIM method with the population crossed between Charleston and Dong nong594 in recent 3 years (2007, 2008, 2009). Combining
the QTLs collected over the past 20 years, an integrated map of oil-content major QTLs in soybean was established using soymap2,
which was published in 2004, as a reference. Using the software BioMercator ver.2.1, QTLs were projected from their own maps
onto the reference map. In total, ninety-eight QTLs were integrated into soymap2. A meta-analysis method was used to narrow
down the confidence interval, and 20 consensus QTLs and their corresponding markers were obtained. Using a local version of
GENSCAN, 10,137 sequences in the consensus QTL intervals were predicted. With BLAST, these predicted genes were compared to
the International Protein Index database to mine the related genes. The results offer a basis for gene mining and molecular
breeding in soybean. 相似文献
73.
Five inbred lines, 10 single cross maize (Zea mays L.) hybrids and two standard cultivars as check were used to study the combining abilities and heterosis under three environmental
conditions. Random amplified polymorphic DNAs (RAPDs) markers were used to study the genetic diversity (GD) and further to
analyze relationship of RAPDs based GD with combining ability and heterosis in short duration maize. Spearman’s rank correlation
coefficients and linear regressions were analyzed to identify the most important factor determining heterosis and per se performance
of the hybrids. Variances due to general combining ability (GCA), specific combining ability (SCA) and their interactions
with environment were found to be significant. Twenty random primers generated 179 RAPD fragments. Of these, 102 RAPD fragments
were polymorphic. GD was determined using Jaccard’s similarity coefficient, and a dendogram was constructed by UPGMA cluster
analysis. The RAPDs based GD exhibited non-significant negative or positive association, non-significant linear regression
along with very low coefficient of determination (R
2) with SCA, high and mid parent heterosis (HP and MP) and per se performance of the hybrids. Significant positive correlations
and regressions along with high coefficients of determination were recorded for SCA with HP, MP and per se performance of
the hybrids. The HP and MP also established significant positive association and linear regression along with high coefficient
of determination with per se performance of hybrids whereas the parental mean did not establish any significant correlations
with the GD, HPH, MPH and grain yield of F1s. The present investigation, therefore, did not find any role of RAPDs based GD in determining hybrid heterosis and hybrid
performance in short duration sub-tropical maize. The SCA, however, has emerged as the most important factor in determination
of heterosis as well as per se performance of the hybrids in short duration maize. 相似文献
74.
Soil N mineralization is affected by microbial biomass and respiration, which are limited by available C and N. To examine the relationship between C and N for soil microbial dynamics and N dynamics, we conducted long-term laboratory incubation (150 days) after C and N amendment and measured changes in C and N mineralization, microbial biomass C, and dissolved C and N throughout the incubation period. The study soil was volcanic immature soil from the southern part of Japan, which contains lower C and N compared with other Japanese forest soils. Despite this, the area is covered by well-developed natural and plantation forests. Carbon amendment resulted in an increase in both microbial biomass and respiration, and net N mineralization decreased, probably due to increasing microbial immobilization. In contrast, N amendment resulted in a decrease in microbial respiration and an increase in net N mineralization, possibly due to decreased immobilization by microbes. Amendment of both C and N simultaneously did not affect microbial biomass and respiration, although net N mineralization was slightly increased. The results suggested that inhibitory effect on microbial respiration by N amendment should be reduced if carbon availability is higher. Thus, soil available C may limit microbial biomass and respiration in this volcanic immature soil. Even in immature soil where C and N substrate is low, soil C, such as plant root exudates and materials from above- and belowground dead organisms, might help to maintain microbial activity and N mineralization in this study site. 相似文献
75.
土壤侵蚀是全球性的严重环境问题。揭示土壤侵蚀过程,建立土壤侵蚀模型将为土地合理利用规划、水土保持措施优化配置、水土流失监测及水土保持减水减沙效益评价等生产实践提供重要科学依据和技术工具。土壤侵蚀预报模型按建模方法可分为经验模型与物理模型等,其中,经验模型主要是基于土壤侵蚀观测资料,采取统计分析的方法模拟侵蚀产沙量与降雨、植被、土壤、地形等影响因子之间的关系。自1953年刘善建在国内首次建立了坡面土壤侵蚀预报方程以来,不同学者根据各地的实际情况,建立了诸多不同的土壤侵蚀经验模型。由于国内土壤侵蚀物理模型研究起步晚,还很不成熟,而经验模型在侵蚀预报中一直处于重要地位,继续强化对它的研究,无疑可以进一步满足水土流失定量评价及水土保持决策等不同生产实践的迫切需求。 相似文献
76.
Niel Hens Christel Faes Marc Aerts Ziv Shkedy Koen Mintiens Hans Laevens Frank Boelaert 《Journal of Agricultural, Biological & Environmental Statistics》2007,12(4):498-513
Modeling infectious diseases data is a relatively young research area in which clustering and stratification are key features.
It is not unlikely for these data to have missing values. If values are missing completely at random, the analysis on the
complete cases is valid. However, in practice this assumption is usually not fulfilled. This article shows the effect of ignoring
missing data in modeling the force of infection of the bovine herpesvirus-1 in Belgian cattle and proposes the use of weighted
generalized estimating equations with constrained fractional polynomials as a flexible modeling tool. 相似文献
77.
Powdery scab caused by Spongospora subterranea f. sp. subterranea (Sss) causes extensive losses in potato production systems globally. Two pot experiments were established in the greenhouse in summer 2013 and winter 2014 to evaluate the effectiveness of different soil chemicals, fumigant, amendments and biological control agents (BCAs) against Sss in the rhizospheric soil, potato roots and tubers. The study used visual assessment methods to assess the effect of treatments on root galling and zoosporangia production, and qPCR to measure Sss concentration in the soil and in the potato roots and tubers. All six soil treatments, namely metam sodium, fluazinam, ZincMax, calcium cyanamide, Biocult and a combination of Bacillus subtilis and Trichoderma asperellum recorded significantly (P < 0.05) lower numbers of zoosporangia in the roots compared to the untreated control. The same effect was observed on the concentration of Sss DNA in the roots at tuber initiation. A more diverse picture was obtained when root gall scores at tuber initiation and Sss DNA in the rhizospheric soil at tuber initiation and harvesting were compared. Significant differences (P < 0.05) were also noted in disease severity, disease incidence, and tuber yield between metam sodium, fluazinam, ZincMax, calcium cyanamide and the untreated control. Calcium cyanamide gave the highest tuber yield. The study demonstrated the potential of soil treatments such as metam sodium, fluazinam, ZincMax and calcium cyanamide in managing Sss in potatoes by reducing the pathogen both in the rhizospheric soil and the roots of the potato plant. 相似文献
78.
Effects of diatom concentration in prepared feeds on growth and energy budget of the sea cucumber Apostichopus japonicus (Selenka) 下载免费PDF全文
Ce Shi Shuanglin Dong Surui Pei Fang Wang Xiangli Tian Qinfeng Gao 《Aquaculture Research》2015,46(3):609-617
Eight test diets were used in the experiment: seven fresh diatom (Cylindrotheca fusiformis) diets in which diatom occupied 100%, 83.3%, 50%, 33.3%, 20%, 14.3% and 11.1% in dry matter of the feeds (marked as D100, D83, D50, D33, D20, D14 and D11), and a formulated diet (70% Sargassum thunbergii powder, 20% sea mud and 10% fish meal, based on dry weight, marked as ST). The results showed that the specific growth rates (SGRs) of the animals fed diets D33, D20, D14 and D11 were not significantly different from the SGR of those fed diet ST. However, the energy allocated to growth for the animals fed with diet D14 was twice that of diet ST. For sea cucumbers fed diet D14 the largest expenditure part was allocated to respiration (55.4%), but for those fed diet ST, the largest part was allocated to faeces (62.7%). The organic content of diet D14 was also much lower than that of diet ST. Frozen diatom diets containing 14% (dry matter weight) fresh diatom could be an environmentally friendly feed as an alternative option for macroalgae powder. 相似文献
79.
80.
Akram Taghizadeh Saroukolai Saeid Moharramipour Mohammad Hadi Meshkatalsadat 《Journal of pest science》2010,83(1):3-8
Red flour beetle Tribolium castaneum (Herbst) and rice weevil Sitophilus oryzae (L.) are considered to be the major insect pests in storage. Essential oils from aromatic plants are recognized as proper
alternatives to fumigants. Thymus persicus (Ronniger ex Rech. f.) is one of these plants that have medicinal properties and is indigenous to Iran. The essential oil
was obtained from aerial parts of the plant and analyzed by GC and GC–MS. Carvacrol (44.69%) and thymol (11.05%) were the
major constituents of the oil extracted. In this experiment, fumigant toxicity of the essential oil was studied against T. castaneum, S. oryzae at 27 ± 1°C and 60 ± 5% RH in dark condition. The adult insects were exposed to the concentrations of 51.9, 111.1, 207.4
and 370.4 μl/l air to estimate median lethal time (LT50) values. The fumigant toxicity was increased in response to increased essential oil concentrations. The LT50 values at the lowest and the highest concentrations tested were ranged from 28.09 to 13.47 h for T. castaneum, and 3.86 to 2.30 h for S. oryzae. It was found that S. oryzae adults were much more susceptible to the oil than T. castaneum. After 24 h of exposure, the LC50 values (95% fiducial limit) for T. castaneum and S. oryzae were estimated to be 236.9 (186.27–292.81) and 3.34 (2.62–4.28) μl/l air, respectively. These results suggest that T. persicus essential oil merits further study as potential fumigant for the management of these stored-product insects. 相似文献