全文获取类型
收费全文 | 836篇 |
免费 | 55篇 |
国内免费 | 81篇 |
专业分类
林业 | 29篇 |
农学 | 38篇 |
基础科学 | 2篇 |
37篇 | |
综合类 | 270篇 |
农作物 | 14篇 |
水产渔业 | 226篇 |
畜牧兽医 | 305篇 |
园艺 | 37篇 |
植物保护 | 14篇 |
出版年
2024年 | 3篇 |
2023年 | 10篇 |
2022年 | 15篇 |
2021年 | 24篇 |
2020年 | 37篇 |
2019年 | 29篇 |
2018年 | 17篇 |
2017年 | 17篇 |
2016年 | 25篇 |
2015年 | 31篇 |
2014年 | 25篇 |
2013年 | 42篇 |
2012年 | 51篇 |
2011年 | 49篇 |
2010年 | 37篇 |
2009年 | 35篇 |
2008年 | 56篇 |
2007年 | 63篇 |
2006年 | 49篇 |
2005年 | 38篇 |
2004年 | 38篇 |
2003年 | 27篇 |
2002年 | 34篇 |
2001年 | 29篇 |
2000年 | 24篇 |
1999年 | 18篇 |
1998年 | 10篇 |
1997年 | 17篇 |
1996年 | 14篇 |
1995年 | 17篇 |
1994年 | 14篇 |
1993年 | 14篇 |
1992年 | 11篇 |
1991年 | 10篇 |
1990年 | 8篇 |
1989年 | 14篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 8篇 |
1983年 | 2篇 |
1956年 | 1篇 |
排序方式: 共有972条查询结果,搜索用时 15 毫秒
101.
激素和多胺对苦瓜性别分化的影响 总被引:29,自引:2,他引:27
研究了GA3(赤霉素)和CCC(矮壮素)处理下株洲长白苦瓜植株,从苗龄8~70天茎尖内源激素的变化。结果表明,第一雌花形成与茎尖内源GA3含量增高有关。开花盛期,茎尖内源IAA含量下降越小,ZT含量下降越大,植株的雌花数和♀/♂越大。分析表明,雌、雄花中内源多胺(cad)含量都明显高于无性组织,可能与性别分化有关,内源亚精胺(spd)含量变化可能与雌花的发生和发育有关,内源腐胺(put)含量的上升可能与雄花的分化有关 相似文献
102.
P. Lonergan 《Acta veterinaria Scandinavica》1994,35(4):307
Development of mammalian embryos in vitro is functionally and temporally inferior to embryo development as it occurs inside the female reproductive tract. The deficiencies of cultured embryos range from slow cleavage rates to complete developmental arrests or blocks, occurring at particular stages in many species. A variety of approaches have been used to overcome the blocks, including most extensively the coculture of preimplantation embryos with various somatic cells. However, even with coculture, development of embryos in vitro is still not equivalent to that in vivo. In most laboratories, only 25–40% of inseminated oocytes develop into morulae and blastocysts in spite of numerous variations on the basic technique. A better understanding of the factors governing embryonic growth is required before we can hope to achieve results comparable with those occurring in vivo. 相似文献
103.
毛叶秋海棠的杂交遗传特性 总被引:1,自引:0,他引:1
采用毛叶秋海棠与云南野生秋海棠, 以及国外毛叶秋海棠的园艺品种进行正反交试验, 观测各杂交F1 代群体叶片斑纹、茎的类型、植株抗寒能力等主要性状的表现及其遗传特性; 通过F1 代自交, 对F2 代群体叶片斑纹的观测统计, 研究银绿斑性状的分离规律。试验结果表明: 毛叶秋海棠银绿斑与无斑是一对相对性状, 银绿斑对无斑是显性, 无斑对银绿斑是隐性, 其遗传杂交符合孟德尔的分离规律; B . rex ×B . longialata F1 代植株银绿斑性状的持续表现受光照强度的影响较大, 生长2 年后需要增加约2000 lx 的光照才能保持原有的银绿斑色彩; 毛叶秋海棠根状茎性状的遗传特性极为稳定, 遗传保持率90 %; 杂交F1 代在抗寒性方面表现了明显的杂种优势。 相似文献
104.
The changes in the amounts of dry matter, total nitrogen and methionine during maturation of normal maize hybrids grown under the same topographical and agrotechnical conditions on two consecutive vegetation years were examined.
Total nitrogen was determined by Kjeldahl's method and methionine spectrophotometrically from papain hydrolysate by the method of McCarthy and Sullivan. Analysis of variance was applied to assess the significance of the changes in particular components during grain maturation.
A significant increase (p = 0.01) in amounts of the all investigated components in original grain matter up until a late stage of dough maturity in both vegetation years was determined. The increase was mostly expressed by the end of milky maturity. The correlation between these components during maturation is positive and highly significant (p = 0.001). The methionine content in dry matter attained in stage of milky maturation the value being characteristic for mature grain. On a total-proteins basis, the methionine content is significantly the least (p = 0.01) at the early stage of milky maturation and increases up until dough maturity reaching a value that does not significantly differ from the value in full maturity of grain. 相似文献
Total nitrogen was determined by Kjeldahl's method and methionine spectrophotometrically from papain hydrolysate by the method of McCarthy and Sullivan. Analysis of variance was applied to assess the significance of the changes in particular components during grain maturation.
A significant increase (p = 0.01) in amounts of the all investigated components in original grain matter up until a late stage of dough maturity in both vegetation years was determined. The increase was mostly expressed by the end of milky maturity. The correlation between these components during maturation is positive and highly significant (p = 0.001). The methionine content in dry matter attained in stage of milky maturation the value being characteristic for mature grain. On a total-proteins basis, the methionine content is significantly the least (p = 0.01) at the early stage of milky maturation and increases up until dough maturity reaching a value that does not significantly differ from the value in full maturity of grain. 相似文献
105.
第二信使因子对牛卵母细胞体外成熟的影响 总被引:6,自引:1,他引:5
本研究旨在确定第二信使因子对牛卵母细胞体外成熟的影响,并探讨通过添加双丁酰cAMP及其激活剂、延长成熟时间,以提高卵母细胞胞质成熟质量的可行性。成熟液添加0.1mmol/L的dbcCMP对牛卵母细胞成熟后的囊胚发育率有促进作用(46.5%比38.5%,P〈0.08)。当成熟培养时间为22h时,0.1mmol/L的dbcAMP或dbcGMP对卵母细胞的分裂率、囊胚发育率及其囊胚的孵化率均无明显影响( 相似文献
106.
Theymoli Balasubramanian S. Sadasivam 《Plant foods for human nutrition (Dordrecht, Netherlands)》1987,37(1):41-46
The okra seeds of variety Pusa sawani were analysed for protein, non-protein nitrogen, total free amino acids, lysine, and tryptophan from the 7th day to the 42nd day after flowering. Starch, total sugars and oil percent were also estimated in these seeds. During the early stages of maturation, the soluble components (non-protein nitrogen, free amino acids and total sugars) were found in higher quantities than in the later stages. Protein, oil and starch contents increased gradually from day 7 to day 42. The rate of accumulation of oil was found to be at the highest level between 21–28 days after flowering, while the rate of protein deposition was greatest between days 35–42. Inditiation of seed maturation seems to start 21 days after flowering in okra seeds. 相似文献
107.
108.
Kiyotaka Gotoh Seishi Akino Takako Kiyoshi Shigeo Naito 《Journal of General Plant Pathology》2005,71(1):29-32
The sexual preferences of Japanese isolates of Phytophthora infestans were determined by mating on agar, in broth, or in plants. The influence of their sexual preference was confirmed in the host tissues. Three wild-type isolates and a -glucuronidase (GUS) transformant were co-cultured to identify the origin of antheridia and oogonia. Japanese A1 isolate had a unique sexual preference compared with foreign isolates. It produced self-fertile oospores with about 40% of total gametangia but tended to form antheridia on V-8 agar medium. In addition, oospores were formed in plants, but their sexual preference could not be reflected in vitro. 相似文献
109.
母猪性周期和妊娠期中外周血T细胞及其亚群的观察 总被引:3,自引:0,他引:3
用酸性α-萘酯酶(ANAE)组化反应标记外周血T细胞。与间情期相比,总T细胞的比率及其两个亚群(辅助性T细胞和抑制性T细胞)的比率在发情前期无明显变化;在发情期和妊娠期,总T细胞的比率显著降低(P<0.05),其中,辅助性T细胞亚群的比率显著降低(P<0.01),而抑制性T细胞亚群的比率显著升高(P<0.01)。表明在发情期和妊娠期,母猪的细胞免疫水平显著地低于间情期。 相似文献
110.
猪子宫内膜肥大细胞消涨规律初探 总被引:14,自引:0,他引:14
雌性小型猪15头,分为二月龄、间情期、民情前期、发情期、妊娠期等六组。颈动脉放血处死,取子宫组织,经甲苯胺改良法和免疫组化法染色,观察肥大细胞的动态变化。子宫内膜肥大细胞的数量随个体的生长而增加。在发情周期中肥大细胞的数量呈规律性的变化:在民情前期一时性地剧增,至发情期陡然降至显著低于间情期的水平,在妊娠期也维持低于间情期的水平。本实验的结果提示,子宫内膜肥大细胞的数量可能反映子宫局部的免疫水平。 相似文献