首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   768篇
  免费   16篇
  国内免费   35篇
林业   68篇
农学   46篇
基础科学   52篇
  75篇
综合类   139篇
农作物   93篇
水产渔业   120篇
畜牧兽医   120篇
园艺   56篇
植物保护   50篇
  2023年   3篇
  2022年   8篇
  2021年   13篇
  2020年   8篇
  2019年   9篇
  2018年   6篇
  2017年   18篇
  2016年   20篇
  2015年   23篇
  2014年   28篇
  2013年   22篇
  2012年   36篇
  2011年   57篇
  2010年   41篇
  2009年   40篇
  2008年   34篇
  2007年   41篇
  2006年   21篇
  2005年   26篇
  2004年   29篇
  2003年   26篇
  2002年   20篇
  2001年   19篇
  2000年   50篇
  1999年   28篇
  1998年   19篇
  1997年   22篇
  1996年   15篇
  1995年   24篇
  1994年   11篇
  1993年   10篇
  1992年   10篇
  1991年   12篇
  1990年   8篇
  1989年   11篇
  1988年   2篇
  1987年   8篇
  1986年   5篇
  1985年   3篇
  1984年   4篇
  1983年   2篇
  1982年   4篇
  1981年   4篇
  1980年   4篇
  1979年   6篇
  1978年   2篇
  1977年   2篇
  1955年   4篇
  1944年   1篇
排序方式: 共有819条查询结果,搜索用时 15 毫秒
21.
湘椒6号是由湖南地方良种伏地尖中选出的自交系F81-1-2从北方引进的甜椒品种经6代单株选择而成L24-1自交系配制而成的一代杂各。该品种植株生长势强,耐寒、耐湿,果实粗牛角形,果色深绿,微辣,商品性好。从定值致收获35 ̄45天,667m^2产鲜椒3000kg。田间表现抗病毒病、疮痂病。  相似文献   
22.
This study aimed at elucidating SS-bonds of HMW-gliadins (HGL) from wheat with the focus on terminators of glutenin polymerisation. HGL from wheat flour extracts non-treated or treated with the S-alkylation reagent N-ethylmaleinimide (NEMI) were compared. HGL from wheat flour Akteur were isolated, hydrolysed with thermolysin and the resulting peptides pre-separated by gel permeation chromatography and analysed by liquid chromatography/mass-spectrometry using alternating electron transfer dissociation/collision-induced dissociation. Altogether, 22 and 28 SS-peptides from samples without and with NEMI treatment, respectively, were identified. Twenty-six peptides included standard SS-bonds of α- and γ-gliadins, high-molecular-weight and low-molecular-weight glutenin subunits. Eleven SS-bonds were identified for the first time. Fifteen peptides unique to HGL contained cysteine residues from gliadins with an odd number of cysteines (ω5-, α- and γ-gliadins). Thus, gliadins with an odd number of cysteines, glutathione and cysteine had acted as terminators of glutenin polymerisation. Decisive differences between samples without and with NEMI treatment were not obvious showing that the termination of polymerisation was already completed in the flour. The two HGL samples, however, were different in the majority of ten peptides that included disulphide-linked low-molecular-weight (LMW) thiols such as glutathione and cysteine with the former being enriched in the non-treated HGL-sample.  相似文献   
23.
入世后我国果业发展的形势及对策   总被引:2,自引:0,他引:2  
针对我国加入世界贸易组织(WTO)的新形势及加入WTO后我国果业面临的机遇和挑战,分析了中国果树生产与出口在世界果业中的地位,剖析了中国果树业发展中存在的主要矛盾和问题,提出了转变思想观念,调整产品结构及经营模式和开拓国际市场等入世对策,以求中国果业能够更加健康稳定地向前发展。  相似文献   
24.
牛卵巢的保存与卵巢内卵母细胞采集的研究   总被引:10,自引:0,他引:10  
利用屠宰牛的卵巢,研究了卵巢内(Interior Ovary,IO)卵母细胞的回收方法与影响IO卵母细胞回收数量的因素,以及卵巢保存方法对卵母细胞体外受精后卵裂率与体外发育能力的影响.结果表明抽吸采取表面卵泡卵母细胞以后,用间隔1.6 mm的4个刀片平行排列构成的切割刀,纵横切割秦川牛卵泡期卵巢,其卵母细胞回收数量最高.两次回收平均每个卵巢可获得26.45个A、B级可用卵,较单纯抽吸采卵(5.15个)提高了约4倍.刀距增宽或缩小都会降低卵母细胞的回收数量.牛品种不同对IO卵母细胞的回收数量有显著影响,以中国荷斯坦牛最多(34.25个/卵巢),秦川牛次之(21.75个/卵巢),山丹牛最少(8.25个/卵巢).牛繁殖状态不同对IO卵母细胞的回收数量有显著影响,以卵泡期最多(21.75个/卵巢),黄体期和妊娠期次之(分别为11.75、10.75个/卵巢),老龄退化期最少(4.25个/卵巢).回收的IO卵母细胞直径和透明带外径分别达(126.9±9.98) μm和(151.85±10.39) μm,均较表面卵母细胞(分别为136.05±6.09 μm和160.80 μm±4.23 μm)要小的多(P<0.01).卵巢保存温度25~29℃与30~37℃对IO卵母细胞体外受精后卵裂率与6~8细胞胚发育率无显著影响(P>0.05),但保存时间则有显著影响,超过6 h会显著降低卵裂率和6~8细胞胚发育率(P<0.05).  相似文献   
25.
26.
Gene expression in black tiger prawns (Penaeus monodon) was studied following intra-muscular injection of CMV08124j38/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">Gal plasmid into the second abdominal segment. We used an in situ staining technique to detect 08124j38/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-gal expression in one- and three-month-old injected prawns. We found that only one of the three-month-old prawns expressed the marker gene (2 days after injection), and the site of expression was confined to the sixth abdominal segment away from the injection site. We repeated the experiment on a new batch of three-month-old prawns, but using fluorometric determination technique. This time we found that 08124j38/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-gal expression was detected (6/42) at the site of injection after 2, 7, and 14 days. In two other test samples, transgene expression was detected in the sixth abdominal segment only, further confirming the possibility of injected DNA dispersal. The results of the study also suggest that direct gene transfer is a feasible technique in black tiger prawns.  相似文献   
27.
Out of a total of 224 bovine eye secretions, 126 Moraxella bovis and 64 Neisseria ovis strains were isolated. The pathogenesis and histological lesions caused by Neisseria ovis have been studied on the eyes of three calves naturally affected with IBK, using electron microscopy.

Neisseria ovis caused in 1013;12 weeks old calves acute, transient and mostly benign serous conjunctivitis with only slight affection of the cornea. More rarely erosions and even ulceration of the cornea have been observed.

Moraxella bovis and Neisseria ovis strains proved nearly unanimously sensitive in vitro to chloramphenicol, neomycin, oxytetracyclin, nitrofurantoin, erythromycin and cefoperazone. Other antibiotics and chemotherapeutics inhibited the growth of these agents only partly or were ineffective.

Experimental therapy has been carried out using a single i.m. injection of Terramycin/LA inj. (Pfizer) in a dose of 20 mg/kg body mass, repeated if necessary after 72013;96 h. This formulation proved more effective and practical than treatments used earlier.  相似文献   

28.
N-methyl-D, L-aspartate (NMA) elicited secretion of growth hormone (GH)-releasing hormone from both the hypothalamic-preoptic area and the median eminence that were collected from boars. We suggest that the previously described increase in GH secretion that follows peripheral treatment of swine with NMA is attributable, at least in part, to NMA-stimulated secretion of GH-releasing hormone from the central nervous system.  相似文献   
29.
Cereal eyespot fungi Tapesia acuformis and Tapesia yallundae are closely related species which show different behaviours upon treatment with sterol 140">-demethylase inhibitors (DMIs). T. acuformis is naturally resistant to DMIs belonging to the triazole family and susceptible to the imidazole ones, whilst T. yallundae is sensitive to both inhibitors. Cloning of the target enzyme gene, CYP51, from the two species revealed an important polymorphism between them. Further sequencing of CYP51 from sixteen T. acuformis and eleven T. yallundae strains with different phenotypes with regards to resistance to DMIs confirmed that at least eleven variations are species related. Among them, a conserved phenylalanine residue at position 180, found both in T. yallundae and in all known CYP51 proteins from filamentous fungi and yeast, was replaced in T. acuformis by a leucine. Therefore, a leucine at 180 could be possibly involved in natural resistance of T. acuformis to triazoles. Other mutations were observed in some resistant strains, sometimes simultaneously, but in contrast to what was reported for other filamentous fungi, where a mutation at the 136 position of the CYP51 gene product seemed to correlate with resistance to DMIs, we did not find a clear relationship between a given mutation and a particular phenotype. This result suggests that resistance to DMIs could have a polygenic nature in Tapesia. We took advantage of species-related variations to develop a PCR-based assay allowing rapid and easy discrimination between field strains of the two species.  相似文献   
30.
The pro- and anti-inflammatory cytokines create a network of interactions between cells that lead to both stimulatory and inhibitory responses that maintain an effective homeostatic regulation. The anti-inflammatory cytokines are a family of peptides that modulate the pro-inflammatory cytokine response. Cytokines act in concert with non-cytokine mediators, such as prostaglandin E2, glucocorticosteroids, lipocortins, and catecholamines. This review highlights new developments in our understanding of the pathophysiology of inflammation and gives an example of a more recent approach to the modulation of acute systemic inflammatory disorders: activation of 0">2-adrenergic receptors on macrophages. In this respect the potent 0">2-adrenergic agonist clenbuterol seems of therapeutic interest.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号