全文获取类型
收费全文 | 16559篇 |
免费 | 2篇 |
专业分类
林业 | 3635篇 |
农学 | 1304篇 |
基础科学 | 140篇 |
2761篇 | |
综合类 | 735篇 |
农作物 | 2102篇 |
水产渔业 | 1794篇 |
畜牧兽医 | 1098篇 |
园艺 | 1112篇 |
植物保护 | 1880篇 |
出版年
2023年 | 3篇 |
2022年 | 2篇 |
2021年 | 4篇 |
2020年 | 8篇 |
2019年 | 4篇 |
2018年 | 2748篇 |
2017年 | 2707篇 |
2016年 | 1181篇 |
2015年 | 66篇 |
2014年 | 18篇 |
2013年 | 20篇 |
2012年 | 799篇 |
2011年 | 2129篇 |
2010年 | 2107篇 |
2009年 | 1259篇 |
2008年 | 1322篇 |
2007年 | 1579篇 |
2006年 | 35篇 |
2005年 | 107篇 |
2004年 | 107篇 |
2003年 | 160篇 |
2002年 | 66篇 |
2001年 | 6篇 |
2000年 | 40篇 |
1997年 | 2篇 |
1994年 | 1篇 |
1993年 | 13篇 |
1992年 | 8篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 6篇 |
1988年 | 13篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 4篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 4篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1970年 | 2篇 |
1969年 | 2篇 |
1968年 | 5篇 |
1967年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
Svetlana Antić-Mladenović Jörg Rinklebe Tina Frohne Hans-Joachim Stärk Rainer Wennrich Zorica Tomić Vlado Ličina 《Journal of Soils and Sediments》2011,11(3):406-415
Purpose
Serpentine soils exist in many regions around the world; they are naturally enriched with nickel (Ni). An adequate understanding of soil processes determining Ni solubility is a special need particularly since less research has been addressed to Ni behavior under dynamic and controlled redox conditions. Our aim was (1) to characterize the properties of a serpentine soil and (2) to determine the impact of predefined redox windows on the mobility and dynamics of Ni in a serpentine soil. 相似文献102.
Jiwen Yu Shuxun Yu Shuli Fan Meizhen Song Honghong Zhai Xingli Li Jinfa Zhang 《Euphytica》2012,187(2):191-201
Cotton is one of the most important oil-producing crops and the cottonseed meal provides important protein nutrients as animal feed. However, information on the genetic basis of cottonseed oil and protein contents is lacking. A backcross inbred line (BIL) population from a cross between Gossypium hirsutum as the recurrent parent and G. barbadense was used to identify quantitative trait loci (QTLs) for cottonseed oil, protein, and gossypol contents. The BIL population of 146 lines together with the two parental lines was tested in the same location for three years in China. Based on a genetic map of 392 SSR markers and a total genetic distance of 2,895.2 cM, 17 QTLs on 12 chromosomes for oil content, 22 QTLs on 12 chromosomes for protein content and three QTLs on two chromosomes for gossypol content were detected. Seed oil content was significantly and negatively correlated with seed protein content, which can be explained by eight QTLs for both oil and protein contents co-localized in the same regions but with opposite additive effects. This research represents the first report using a permanent advanced backcross inbred population of an interspecific hybrid population to identify QTLs for seed quality traits in cotton in three environments. 相似文献
103.
A new Hg2+-selective chemosensor based on dithiosquarylium (DTSQ) dye was investigated. Among various metal cations tested, exclusively
Hg2+ ion responses to irreversible color change of DTSQ-1, along with the Hg2+-triggered desulfurization of dithiosquarylium into its oxygen analogue squarylium (SQ) dye. 相似文献
104.
Bhaskar Bhagya Kandikere R. Sridhar Sahadevan Seena Chiu-Chung Young Ananthapadmanabha B. Arun 《Frontiers of Agriculture in China》2010,4(4):481-488
This study has been performed to evaluate the nutritional, antinutritional and protein qualities of tender pods of Canavalia maritima, the coastal sand dune wild legume of southwest India. The proximal features, minerals, amino acids, fatty acids, antinutritional
and protein qualities of fresh and pressure-cooked tender pods have been assessed. The crude protein was comparable to seeds
of many edible legumes. Cooking significantly elevated the carbohydrates and calorific value of tender pods (P < 0.05), while crude fiber was significantly decreased (P < 0.05). Minerals of fresh pods did not drain too much on cooking and K, Mg, Zn and Mn in fresh as well as cooked pods were
comparable or higher than the NRC-NAS recommended pattern. Although cooking decreased the essential amino acids, threonine,
valine, isoleucine, phenylalanine and lysine in cooked pods were equivalent or higher than the FAO-WHO-UNU recommended pattern.
The palmitoleic acid in fresh pods and eicosenoic acid in cooked pods were relatively high. Similarly, the essential fatty
acids, linolenic acid and linoleic acid were confined to fresh and cooked pods respectively. The fresh pods were devoid of
tannins and trypsin inhibitors. The total phenolics and hemagglutinin activity decreased substantially in cooked pods. The
diet of pressure-cooked pods showed improvement of in vivo protein quality, elevation of growth parameters and positive nitrogen balance in rats. Overall, the pressurecooking of tender
pods of C. maritima improved the nutritional qualities by lowering the hemagglutinin activity. 相似文献
105.
Prity Sundaram Srinivasan Samineni Sobhan B. Sajja S. P. Singh R. N. Sharma Pooran M. Gaur 《Euphytica》2018,214(4):63
Seed size, determined by 100-seed weight, is an important yield component and trade value trait in kabuli chickpea. In the present investigation, the small seeded kabuli genotype ICC 16644 was crossed with four genotypes (JGK 2, KAK 2, KRIPA and ICC 17109) and F1, F2 and F3 populations were developed to study the gene action involved in seed size and other yield attributing traits. Scaling test and joint scaling test revealed the presence of epistasis for days to first flower, days to maturity, plant height, number of pods per plant, number of seeds per plant, number of seeds per pod, biological yield per plant, grain yield per plant and 100-seed weight. Additive, additive?×?additive and dominance?×?dominance effects were found to govern days to first flower. Days to maturity and plant height were under the control of both the main as well as interaction effects. Number of seeds per pod was predominantly under the control of additive and additive?×?additive effects. For grain yield per plant, additive and dominance?×?dominance effects were significant in the cross ICC 16644?×?KAK 2, whereas, additive?×?additive effects were important in the cross ICC 16644?×?JGK 2. Additive, dominance and epistatic effects influenced seed size. The study emphasized the existence of duplicate epistasis for most of the traits. To explore both additive and non-additive gene actions for phenological traits and yield traits, selection in later generations would be more effective. 相似文献
106.
Shuzo Sueyoshi 《Journal of Wood Science》2008,54(4):285-288
Floor-impact sounds may introduce noise problems in dwelling-type environments. In particular, floor-impact sounds from lightweight
structures like wood-framed buildings should be paid significant attention. In this study, such floor-impact sounds were investigated
from the viewpoint of residents. The floor specifications of wood-framed structures were improved by using high-density underlay,
and heavy floor-impact sounds were evaluated by using both psychoacoustical and conventional methods. The results showed that
the floor-impact sound insulation grades specified in the Japanese Industrial Standards (JIS) did not correspond to the floor
specifications of wood-framed structures. The nonstationary loudness, which is a psychoacoustical index for nonstationary
sounds, changed with the specifications of wood-framed structures in a wider range of floor-impact sound levels in comparison
with the maximum A-weighted sound pressure level, which is a single-number index of the JIS. 相似文献
107.
Guanghua Wang Zhenhua Yu Junjie Liu Jian Jin Xiaobing Liu Makoto Kimura 《Biology and Fertility of Soils》2011,47(3):273-282
Bacteriophages (phages) are the most abundant biological entities on the planet and are important as the greatest genomic
reservoirs in both marine and terrestrial environments. In this study, we analysed T4-type phage communities in an upland
black soil by monitoring g23 clones in DNA extracted from seasonal soil samples with no fertilizer, chemical fertilizers, chemical fertilizers plus manure,
and natural restoration treatments. PCR products with degenerate primers MZIA1bis and MZIA6 were subjected to denaturing gradient
gel electrophoresis. In total, 46 clones with different g23 sequences were obtained. Phylogenetic analyses indicated that T4-type phage communities in the upland black soil were distinctly
different from those in marine environments and in an Antarctic lake, which strongly suggested that T4-type phage communities
in soil differed from those in aquatic environments. Among 46 clones, 18 clones formed clusters with the clones from rice
field soils, 14 clones formed three new clusters, and 13 clones were left as ungrouped, which indicated that T4-type phage
communities in the upland black soil were relatively similar to those in rice field soils but that specific communities also
inhabit in the upland black soil exclusively. 相似文献
108.
Background, aim and scope
This paper discusses a method investigating the reduction of free heavy metal cation contents in soil through the use of microbe-inducing precipitate (MIP). 相似文献109.
Varietal seed mixtures tend to increase and stabilize crop yields, yet their application is sparse. Large-scale cultivation of variety mixtures may require a better understanding of how inter-varietal interactions and their interaction with the environment may influence the grain yield of variety mixtures relative to their component varieties. For this purpose, six variety mixtures of spring barley and 14 component varieties were grown in each of 17 trial environments. A total of 28 observed and a priori plant characteristics, including grain yield, disease severity and weed competitiveness, were derived for each component variety in each trial. The relationship between inter-varietal diversity of each characteristic and the mixing effect on grain yield was analysed. Additionally, various types of yield stability were estimated and compared among mixtures and component varieties. One mixture out-yielded all of its component varieties in almost half of the trial environments. Inter-varietal diversity in grain yield potential correlated significantly with mixing effect, as did straw length diversity when weighted with weed pressure. The grain yields of most mixtures were more stable across environments than their component varieties when accounting also for the general response to environmental productivity. Hence, most mixtures adapted slightly better to environmental productivity and were less sensitive to environmental stress than their component varieties. We conclude that the efficacy of variety mixtures may be enhanced by mixing relatively high-yielding varieties differing in responsiveness to environmental productivity. 相似文献
110.
Janusz Kloskowski 《Aquaculture International》2011,19(6):1151-1164
Sustainable development of common carp Cyprinus carpio pond fisheries in Europe postulates their multifunctional use, integrating exploitation of aquaculture resources with recreational
services and maintenance of high levels of local biodiversity. Age classes of farmed carp are grown separately and pond ecosystems
may be differently affected by different ontogenetic stages of fish. To examine these relationships, a study was conducted
on spring and summer diet of carp, invertebrate abundance and community structure, and water quality characteristics in ponds
stocked with three carp age classes in SE Poland. With the exception of young-of-the-year fish in spring, benthic dipterans
prevailed in the diets of all carp age classes and their consumption increased from spring to summer. Zooplankton featured
in the diet of carp only in spring. Medium- and large-sized cladocerans predominated among microcrustaceans found in the guts
of one- and two-year-old carp. Consequently, in summer, total biomass of medium- and large-sized cladoceran grazers was substantially
lower in ponds stocked with older-age fish than in ponds used for production of 1-summer-old fingerlings. The relatively sparse
submerged vegetation cover and low water transparency in ponds with older fish stocks compared to ponds with young-of-the-year
carp indicate a transition to a turbid water state mediated by a trophic cascade mechanism in the presence of older-age fish.
Densities of water-column macroinvertebrates decreased with the age of carp in the ponds. These results suggest that non-aquaculture
use of carp ponds should be diversified according to their environmental quality. Fingerling rearing ponds are more suitable
for environmentally friendly multifunctional use than ponds with older stocks. 相似文献