全文获取类型
收费全文 | 3019篇 |
免费 | 189篇 |
国内免费 | 316篇 |
专业分类
林业 | 124篇 |
农学 | 326篇 |
基础科学 | 40篇 |
403篇 | |
综合类 | 1151篇 |
农作物 | 279篇 |
水产渔业 | 176篇 |
畜牧兽医 | 589篇 |
园艺 | 237篇 |
植物保护 | 199篇 |
出版年
2024年 | 6篇 |
2023年 | 40篇 |
2022年 | 79篇 |
2021年 | 95篇 |
2020年 | 86篇 |
2019年 | 130篇 |
2018年 | 87篇 |
2017年 | 166篇 |
2016年 | 178篇 |
2015年 | 145篇 |
2014年 | 158篇 |
2013年 | 213篇 |
2012年 | 249篇 |
2011年 | 251篇 |
2010年 | 183篇 |
2009年 | 180篇 |
2008年 | 166篇 |
2007年 | 180篇 |
2006年 | 141篇 |
2005年 | 96篇 |
2004年 | 104篇 |
2003年 | 75篇 |
2002年 | 68篇 |
2001年 | 61篇 |
2000年 | 63篇 |
1999年 | 43篇 |
1998年 | 37篇 |
1997年 | 32篇 |
1996年 | 32篇 |
1995年 | 28篇 |
1994年 | 21篇 |
1993年 | 19篇 |
1992年 | 22篇 |
1991年 | 11篇 |
1990年 | 15篇 |
1989年 | 17篇 |
1988年 | 8篇 |
1987年 | 9篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1955年 | 1篇 |
排序方式: 共有3524条查询结果,搜索用时 31 毫秒
1.
Cuticular protein gene LmACP8 is involved in wing morphogenesis in the migratory locust,Locusta migratoria 下载免费PDF全文
Cuticular proteins(CPs) are major components of the insect cuticle-associated organs such as integument and wings, although the importance of CPs for wing development and function in hemimetabolous insects remains understudied. In the present study, a wing cuticular protein LmACP8 was identified from Locusta migratoria, which belongs to the RR-2 subfamily of cuticular protein RR consensus(CPR) chitin-binding proteins. LmACP8 was mainly expressed in the wing pads and showed high expression levels before ecdysis of third-, fourth-, and fifth-instar nymphs, with its encoded protein located in the procuticle of wing pads and adult wings. Depletion of LmACP8 by RNA interference markedly reduced the amount of its protein, which consequently caused abnormal wing morphogenesis in the transition from nymph to adult of L. migratoria. We further demonstrated that the abnormal morphogenesis was caused by severe damage of the endocuticle in the wings. LmACP8 was suppressed by 20-hydroxyecdysone(20 E) in vivo, however, its expression was significantly up-regulated after knocking down the hormone receptor gene LmHR39. Thus, the LmACP8 that is negatively regulated by the LmHR39-mediated 20 E signaling pathway is involved in wing development during the nymph to adult transition. 相似文献
2.
Replacing Soybean Meal with Alternative Protein Sources in Diets for Pond‐raised Hybrid Catfish, ♀ Ictalurus punctatus × ♂ Ictalurus furcatus 下载免费PDF全文
Menghe H. Li Brian G. Bosworth Penelope M. Lucas 《Journal of the World Aquaculture Society》2018,49(4):755-760
The present study investigated the replacement of soybean meal with combinations of two or three alternative protein sources in diets for pond‐raised hybrid catfish, ♀ Ictalurus punctatus × ♂ Ictalurus furcatus. Alternative protein sources evaluated included cottonseed meal, distillers dried grains with solubles (DDGS), peanut meal, and porcine meat and bone meal (PMBM). Hybrid catfish fingerlings with a mean initial weight of 35 g/fish were stocked into 25 earthen ponds (0.04 ha) at a density of 14,826 fish/ha. Fish were fed once daily to apparent satiation for 166 d. No significant differences were observed for total diet fed, net yield, weight gain, survival, carcass yield, fillet yield, or fillet proximate composition among dietary treatments. Results show soybean meal may be completely replaced by combinations of cottonseed meal and one or two other alternative protein sources including DDGS, peanut meal, and PMBM in the diet without markedly affecting production and processing characteristics and fillet proximate composition of pond‐raised hybrid catfish. These alternative diets may be used during foodfish production when prices are favorable. 相似文献
3.
4.
经过蛋白质着色动力学的研究,发现蛋白质着色的行为遵循数学模型Y=aX^b。在pH2-6范围内,蛋白质上染料随染溶pH的下降而上升,在15-30℃温度范围内,蛋白质上染率随温度上升略有提高,当温度超过30℃时,蛋白质上染率逐渐下降。染浴中添加稀土对蛋白质有较强的促染效果,其实质是染浴中蛋白质首先对稀土高价阳离子进行结合,再通过高价阳离子对色素进吸附。 相似文献
5.
青海血蜱不同发育阶段蛋白分析 总被引:2,自引:0,他引:2
考虑到不同发育阶段蛋白多肽及抗原特性方面的差异,本实验利用SDS-PAGE和Westernblotting对青海血蜱的卵、幼蜱、若蜱、成蜱的蛋白进行了分析。SDS-PAGE结果显示,卵出现了7条主带,幼蜱出现了16条主带,若蜱出现了14条主带,成蜱出现了12条主带。它们的蛋白多肽在数量、含量和分子量上存在差异,共同带只有4条,但相邻发育阶段之间的共同带较多。用感染羊血清和免疫羊血清作免疫印迹时,感染羊血清在分子量5.6万处有明显的反应带,免疫羊血清在分子量9.7万处有明显的反应带。 相似文献
6.
DENG Zhi-rui ZHANG Rong-xian 《水稻科学》2004,11(1)
Two japonica rice varieties, Wuyujing 3 and 97-7, were used to study the changes in contents of soluble protein, free amino acids and endopeptidase activity during photosynthetic declination. The content of soluble protein in flag leaf of cv.Wuyujing 3 was higher than that of cv. 97-7, but decreased rapidly in Wuyujing 3. Free amino acids in flag leaf and the thirteenth leaf of Wuyujing 3 started to increase 10 days before the turning point of photosynthetic declination (TPPD), while it occurred just 1-2 days before TPPD in the flag leaf and the thirteenth leaf of 97-7. During reversible phase of photosynthetic declination,endopeptidase activity remained at a low level and increased slightly only in the later part of this phase. Then it rose up rapidly at irreversible decline phase and reached a very high level. For Wuyujing 3, the change in endopeptidase activity in the thirteenth leaf was parallel to that in flag leaf. However, for 97-7, the rapid increase of endopeptidase activity in the thirteenth leaf started later than that of flag leaf. The results implied that the rate of protein breakdown and conversion to transportable nitrogen in leaves of 97-7 was slower than that in leaves of Wuyujing 3 during photosynthetic declination and it led to relatively lower seed setting rate and fully filling grains rate in 97-7. This may be one of the important reasons why 97-7 could not bring the high yield potentiality into play and the findings may be taken into consideration while breeding for high potential varieties in future. 相似文献
7.
A field experiment was conducted to find out the critical physiological stages of irrigation schedules inducing better growth, physiological efficiency and seed yield potential of berseem ( Trifolium alexandrinum L., Var. S-99-1). For this purpose eight irrigation treatments were made comprised of four treatments of three irrigation (W1 , W2 , W3 and W4 ), three treatments of four irrigation (W5 , W7 and W8 ) and one treatment of five irrigation (W6 ) at various physiological stages i. e. regeneration, flower initiation, full bloom, seed initiation and advance seed development stage.
Thus based on the experimental results the physiological role of watering in berseem seed production could be discussed as:
With-holding of irrigation either at regeneration or at full bloom stage developed potential water stress in plants as indicated by high proline content of irrigation treatments — W4 , W1 and W7 ; and further brought out disturbance on the formation of carotene, synthesis of water soluble sugar and translocation of sugar towards reproductive organs during grain development stage. These stresses adversely affected the plant growth and flowering behaviour. The irrigation at seed initiation stage increased the seed yield. Continuous irrigation did not appear to be useful. Thus it can be concluded that irrigation at three critical physiological stages i. e. regeneration, full bloom and seed initiation was found to be essential for obtaining potential seed yield of berseem. 相似文献
Thus based on the experimental results the physiological role of watering in berseem seed production could be discussed as:
With-holding of irrigation either at regeneration or at full bloom stage developed potential water stress in plants as indicated by high proline content of irrigation treatments — W
8.
土壤水溶性盐的含量与组成随制备浸出液的水土比例不同而异,对含石膏的盐渍土测定结果的影响尤为显著。为了正确反映田间水溶性盐的实际状况,作者进行了三种不同水土比例制备浸出液的对比试验。结果表明,适宜水土比为1:1,其测出的盐分含量与饱和泥浆法按近,且操作简便、快速,在我国一般土化分析实验室均可采用。 相似文献
9.
甘肃滩羊血红蛋白(Hb)及红细胞蛋白质(Ep)多态性的研究 总被引:6,自引:3,他引:3
运用聚丙烯酰胺凝胶电泳技术(PAGE)对甘肃滩羊产区皋兰、景泰及靖远3县285只滩羊的血红蛋白(Hb)基因座、红细胞蛋白质-1(Ep-1)和红细胞蛋白质-2(Ep-2)基因座多态性进行了检测,结果发现甘肃滩羊Hb基因座存在3种基因型HbAA、HbAB、HbBB,它们受HbA和HbB两个共显性等位基因控制,其中HbB和HbBB在3个群体中均占优势;本研究未在Ep-1和Ep-2基因座上检测到多态性,它们均呈现单态。 相似文献
10.
Baker RJ Valli VE 《Veterinary clinical pathology / American Society for Veterinary Clinical Pathology》1986,15(4):20-25
A review of the current literature available on feline serum proteins is presented. Early studies concentrated on comparative aspects of species variations in the electrophoretic pattern. The feline electrophoretogram was divided into five basic regions: albumin, alpha-1, alpha-2, beta and gamma. Different subdivisions of these areas were recognized depending on the support medium used. Current papers have compared the relative migration distances of each globulin peak to the migration of albumin. This "Rf" value enables reliable peak identification. To date, no data exists identifying the individual proteins responsible for the peaks in the alpha and beta regions. The only feline globulin to be studied is haptolobin; however its precise location on the electrophoretic strip was not identified. 相似文献