全文获取类型
收费全文 | 12888篇 |
免费 | 574篇 |
国内免费 | 2401篇 |
专业分类
林业 | 237篇 |
农学 | 2133篇 |
基础科学 | 835篇 |
1998篇 | |
综合类 | 6743篇 |
农作物 | 2026篇 |
水产渔业 | 175篇 |
畜牧兽医 | 521篇 |
园艺 | 224篇 |
植物保护 | 971篇 |
出版年
2024年 | 109篇 |
2023年 | 270篇 |
2022年 | 489篇 |
2021年 | 516篇 |
2020年 | 585篇 |
2019年 | 602篇 |
2018年 | 500篇 |
2017年 | 631篇 |
2016年 | 759篇 |
2015年 | 621篇 |
2014年 | 758篇 |
2013年 | 741篇 |
2012年 | 1002篇 |
2011年 | 970篇 |
2010年 | 766篇 |
2009年 | 795篇 |
2008年 | 676篇 |
2007年 | 791篇 |
2006年 | 614篇 |
2005年 | 536篇 |
2004年 | 408篇 |
2003年 | 339篇 |
2002年 | 306篇 |
2001年 | 299篇 |
2000年 | 303篇 |
1999年 | 220篇 |
1998年 | 171篇 |
1997年 | 157篇 |
1996年 | 141篇 |
1995年 | 148篇 |
1994年 | 112篇 |
1993年 | 112篇 |
1992年 | 88篇 |
1991年 | 56篇 |
1990年 | 67篇 |
1989年 | 63篇 |
1988年 | 33篇 |
1987年 | 27篇 |
1986年 | 14篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1982年 | 2篇 |
1981年 | 12篇 |
1980年 | 3篇 |
1979年 | 7篇 |
1978年 | 8篇 |
1976年 | 5篇 |
1974年 | 1篇 |
1962年 | 12篇 |
1955年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
991.
Dynamics of the accumulation of total ash and zinc, and their relationships with total dry matter, crude proteins and phytic acid during maize grain maturation were investigated. The investigation was carried out on normal maize hybrids grown under the same topographical and agrotechnical conditions over two consecutive vegetation years.
The amount of total ash, expressed on fresh and dry matter bases, changed significantly (P = 0.05 and P = 0.01) during grain maturation depending on maturity stage and variety. The dynamics of the accumulation of ash in fresh grain matter during maturation as well as the ash amount in dry matter of mature grains were significantly affected by environmental conditions.
The accumulation of zinc in fresh matter of developing grain was significantly affected (P = 0.05 and P = 0.01) by the degree of grain maturity and by variety, and correlates significantly (P = 0.001) and positively with the deposition of total dry matter, crude proteins as well as with phytic acid in both vegetation years.
The molar ratio of phytic acid and zinc increased significantly during grain maturation indicating a possible decrease of zinc availability. 相似文献
The amount of total ash, expressed on fresh and dry matter bases, changed significantly (P = 0.05 and P = 0.01) during grain maturation depending on maturity stage and variety. The dynamics of the accumulation of ash in fresh grain matter during maturation as well as the ash amount in dry matter of mature grains were significantly affected by environmental conditions.
The accumulation of zinc in fresh matter of developing grain was significantly affected (P = 0.05 and P = 0.01) by the degree of grain maturity and by variety, and correlates significantly (P = 0.001) and positively with the deposition of total dry matter, crude proteins as well as with phytic acid in both vegetation years.
The molar ratio of phytic acid and zinc increased significantly during grain maturation indicating a possible decrease of zinc availability. 相似文献
992.
^60Co—γ射线诱发的籼型温敏核不育水稻叶色突变系变异分析 总被引:8,自引:0,他引:8
^60Co-γ射线诱发的8个灿温敏核不育系水稻叶色突变系可分为三种类型,即叶色突变高温表达型、低温表达型及温钝型。 相似文献
993.
本文首次报道了一个新的陆地棉三体(Ftr-6)的发现,并对其形态,减数分裂中期I染色体构型进行了研究,同时,通过其与一套易位系杂交F1花粉母期细胞染色体构型的细胞学检测,证明Ftr-6可能是第19染色体的三体。 相似文献
994.
灌水方式对轻度盐化土壤玉米生长及土壤水分的影响 总被引:4,自引:0,他引:4
以盆栽玉米为研究对象研究了直接浇灌、滴灌、微润灌等3种灌水方式下玉米的生长、叶绿素含量和光合速率、蒸腾速率等生理生态指标及土壤水分垂直分布的特征,结果表明:灌水方式对玉米生理生态指标有较大影响,苗期滴灌玉米生长较快,拔节前期,微润灌条件下玉米生长最为迅速,滴灌次之,直接浇灌生长最慢;滴灌条件下叶绿素含量最高,拔节期需水旺季时微润灌叶绿素含量最低.三种灌水方式对玉米光合速率的影响为:微润灌<滴灌<直接浇灌.土壤水分特征表明:微润灌稳定后土壤水分主要分布在10~ 30 cm土层,滴灌主要分布在10~ 40 cm土层;苗期、拔节期灌水后取样测定的土壤含水率表明,作物根系层内微润灌与滴灌均大于直接浇灌时的土壤含水率. 相似文献
995.
M. Meeks S. C. Murray S. Hague D. Hays A. M. H. Ibrahim 《Journal of Agronomy and Crop Science》2012,198(3):161-172
Drought stress is thought to promote epicuticular wax accumulation on maize leaves, which reduces plant water loss. We evaluated 62 maize inbred lines and their hybrid testcross progeny for epicuticular wax accumulation on flag leaves at flowering under full and limited irrigation regimes. Extracted wax was measured as a percentage of wax weight to leaf weight (WLW) and leaf area (WLA). Eleven genotypes had above average WLW as both inbred lines and hybrid testcrosses. Thirteen genotypes had above average WLA as either inbred lines or hybrid testcrosses. The drought treatment did not significantly alter WLW or WLA. Heritability of WLW was 0.17 (inbred lines) and 0.58 (hybrid testcrosses). Heritability of WLA was 0.41 (inbred lines) and 0.59 (hybrid testcrosses), suggesting it is a better trait than WLW for epicuticular wax screening. Correlations (r) between inbred lines and their testcross progeny were 0.44 and 0.18, for WLW and WLA, respectively. Heritability of grain weight per ear and plot yield was highest in hybrid testcrosses, with no correlation between inbred and hybrid germplasm. It is not warranted to evaluate epicuticular wax accumulation as the sole drought tolerance mechanism. However, it may be a good secondary trait to observe in relation to grain yield production in hybrids tested under water‐limiting conditions. 相似文献
996.
吉林省特用玉米现状、趋势及生产基地布局研究 总被引:6,自引:0,他引:6
简析了吉林省特用玉米生产现状及发展趋势,并根据依靠市场、因地制宜、行政区完整、可持续发展的布局原则,将吉林省特用玉米种植基地分为5个大区,提出建设特用玉米生产基地的保障措施。 相似文献
997.
选用7种不同细胞质源滇型不育系与滇一型保持系及恢复系各5个材料进行杂交,对70个杂交组合的剑叶穗颈夹角、剑叶长宽比、株高、穗长及穗总粒数这5个性状进行分析。试验结果表明,滇型杂交水稻在剑叶长宽比、株高、穗长及穗总粒数等性状的表现主要受不育系母本的影响,在组配滇型杂交稻时考虑不育系多项农艺性状的表现显得尤为重要。 相似文献
998.
小麦-中间偃麦草二体异代换系山农0095的选育及其鉴定 总被引:6,自引:0,他引:6
利用小麦品种烟农15与中间偃麦草直接杂交,以烟农15为回交亲本对其杂种F1回交2次,再经自交3次,从BC2F4中选出种质系山农0095。利用形态学、细胞学、种子醇溶蛋白酸性聚丙烯酰胺凝胶电泳(A-PAGE)、RAPD和GISH等方法对其进行鉴定。结果表明,山农0095平均株高78 cm,穗长17.3 cm,穗粒数74个,旗叶长36.3 cm,旗叶宽3.03 cm,茎秆粗壮,多花多实,繁茂性好;其根尖细胞染色体数目为2n=42,花粉母细胞减数分裂中期Ⅰ(PMC MⅠ)染色体构型为2n=21Ⅱ;它与烟农15的杂种F1 在减数分裂中期Ⅰ的大多数花粉母细胞能观察到2个单价体,平均染色体构型为2n=20.08Ⅱ+1.84Ⅰ。A-PAGE鉴定结果表明,山农0095在β区出现一条中间偃麦草的特异带;从180个RAPD引物中筛选出一个特异引物S186(5?-GAT ACC TCGG-3?),能够在山农0095中扩增出一条约900 bp中间偃麦草的特异带,标记为S186900;以中间偃麦草基因组DNA为标记探针、中国春基因组DNA为封阻的原位杂交结果进一步表明,山农0095的42条染色体中含有2条完整的中间偃麦草染色体,是小麦-中间偃麦草的二体异代换系。 相似文献
999.
超甜玉米单交种"吉甜6号"选育报告 总被引:2,自引:4,他引:2
超甜玉米品种"吉甜6号"是吉林农业大学以自选系"吉898"为母本、"吉908"为父本杂交育成的甜玉米单交种.1996-1998年吉林省专用型玉米品种区域试验平均鲜果穗产量为13 337.8 kg/hm2,比对照品种"吉甜3号"增产9.7%.1997-1998年吉林省生产试验平均鲜果穗产量为12 401.5 kg/hm2,比对照品种"吉甜3号"增产5.5%,2000-2001年国家东北、华北地区鲜食玉米品种区域试验平均鲜果穗产量13 196.3 kg/hm2.鲜籽粒含糖量18.73%,籽粒皮薄、甜而脆,有香味,口感好,品质优.高抗大斑病、弯孢菌叶斑病、丝黑穗病,抗灰斑病和玉米螟,中抗茎腐病.适宜在河北、山西、辽宁、吉林、新疆、黑龙江、内蒙等地区种植.于2003年通过国家农作物品种审定委员会审定. 相似文献
1000.
L. R. Salado‐Navarro T. R. Sinclair M. Morandini 《Journal of Agronomy and Crop Science》2013,199(1):57-65
Abstract Estimates of soil evaporation and available soil water of no‐tillage fields under farm conditions are important to assess soil water status at sowing of rainfed grain crops. The objective of this study was to predict stored soil water of no‐tillage fields during the fallow periods following soybean (Glycine max (L.) Merr.) and maize (Zea mays L.) crops by accounting for decreased soil evaporation as a result of the residues left on the soil surface. Three simple phenomenological models were used to simulate stored soil water under field conditions at seven locations in Argentina. Two models calculated decreased soil evaporation based on crop residue mass, and the third assumed a constant fractional decrease in bare soil evaporation. All models gave good estimates of soil water content during the fallow periods following a soybean crop. In cases with large quantities of maize residue, however, the models resulted in more water retention in the soil than observed as a consequence of underprediction of soil evaporation. These results indicate that full benefit of crop residue was not being achieved in these fields, probably due to a failure to finely chop and uniformly distribute the crop material on the soil surface. 相似文献