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   144篇
  免费   5篇
林业   2篇
  27篇
综合类   14篇
农作物   3篇
水产渔业   10篇
畜牧兽医   86篇
园艺   1篇
植物保护   6篇
  2021年   2篇
  2020年   1篇
  2019年   1篇
  2018年   1篇
  2016年   1篇
  2015年   1篇
  2014年   3篇
  2013年   9篇
  2012年   10篇
  2011年   4篇
  2010年   3篇
  2009年   6篇
  2008年   2篇
  2007年   6篇
  2006年   3篇
  2005年   3篇
  2004年   10篇
  2003年   5篇
  2002年   8篇
  2001年   6篇
  2000年   6篇
  1999年   1篇
  1998年   1篇
  1997年   4篇
  1996年   2篇
  1995年   1篇
  1994年   2篇
  1993年   3篇
  1991年   2篇
  1990年   1篇
  1989年   3篇
  1988年   1篇
  1986年   1篇
  1985年   2篇
  1984年   1篇
  1982年   1篇
  1980年   3篇
  1978年   2篇
  1977年   2篇
  1975年   3篇
  1974年   3篇
  1973年   2篇
  1971年   2篇
  1970年   3篇
  1969年   1篇
  1968年   3篇
  1958年   3篇
  1957年   2篇
  1934年   1篇
  1931年   1篇
排序方式: 共有149条查询结果,搜索用时 46 毫秒
51.
52.
53.
54.
BackgroundThe normal vertebral anatomy of Korean raccoon dogs and their variants require research attention as a prerequisite for identifying pathologies and anomalies.ObjectivesThis retrospective study aimed at describing the vertebral formula and congenital vertebral anomalies in Korean raccoon dogs (Nyctereutes procyonoides koreensis).MethodsRadiographs of 82 raccoon dogs (42 males, 40 females) acquired from May 2013 to June 2020 in the Gangwon Wildlife Medical Rescue Center were reviewed to evaluate the cervical, thoracic, and lumbar vertebrae of the spine.ResultsNormal morphology of all vertebrae was observed in 50 of the 82 raccoon dogs, and the vertebral formula was cervical 7, thoracic 13, and lumbar 7. Congenital vertebral anomalies were found in 32 raccoon dogs: transitional vertebrae (TV) in 31 and block vertebrae in 2. Two raccoon dogs had 2 types of vertebral anomalies: one had TV and block vertebra, and the other had 2 types of TV. Twenty-nine raccoon dogs had thoracolumbar TV (TTV) and 3 had lumbosacral TV. TTV was morphologically classified into 4 different types: unilateral extra-rib in 5 raccoon dogs, bilateral extra-ribs in 14, bilateral elongated transverse processes in 4, and an asymmetric mixed formation of extra-rib with elongated transverse process in 6.ConclusionsThis study showed that TTV is common in Korean raccoon dogs, and that the vertebral formula is relatively diverse. The bilateral extra-ribs type TTV is the most common variant, which is almost similar to normal rib to be confused the radiographic evaluation.  相似文献   
55.
Nucleotide sequence and expression of an AIDS-associated retrovirus (ARV-2)   总被引:139,自引:0,他引:139  
The nucleotide sequence of molecular clones of DNA from a retrovirus, ARV-2, associated with the acquired immune deficiency syndrome (AIDS) was determined. Proviral DNA of ARV-2 (9737 base pairs) has long terminal repeat structures (636 base pairs) and long open reading frames encoding gag (506 codons), pol (1003 codons), and env (863 codons) genes. Two additional open reading frames were identified. Significant amino acid homology with several other retroviruses was noted in the predicted product of gag and pol, but ARV-2 was as closely related to murine and avian retroviruses as it was to human T-cell leukemia viruses (HTLV-I and HTLV-II). By means of an SV-40 vector in transfected simian cells, the cloned gag and env genes of ARV-2 were shown to express viral proteins.  相似文献   
56.
N E Kohl  C E Gee  F W Alt 《Science (New York, N.Y.)》1984,226(4680):1335-1337
In neuroblastoma lines in which the N-myc gene is present as a single copy, the expression of N-myc as messenger RNA is increased relative to that in nonneuroblastoma cell lines and tumors. The increase of expression in neuroblastomas with amplified N-myc genes is the result of (i) an increase in the absolute amount of expression of each N-myc gene and (ii) an increase in the copy number of the N-myc gene. A second gene--which is amplified in many of the same lines as N-myc--is expressed to about the same degree in most human cell lines and primary tumors regardless of origin (when normalized to gene copy number). Thus, a change in the regulation of N-myc expression in neuroblastomas and certain other tumors results in greatly increased expression of each N-myc gene copy.  相似文献   
57.
Bradycardia associated with diving in the harbor seal has been dissociated from the arterial constrictor response by intracardiac pacing. Development of arterial constriction does not depend upon the development of bradycardia. During pacing, arterial constriction continues in the absence of bradycardia. Increases in heart rate to values greater than 120 beats per minute during a dive produce a progressive decrease in mean aortic pressure, which suggests that one major function of bradycardia is to reduce cardiac output, thus matching left ventricular output to the restricted vascular bed and decreased venous return associated with diving.  相似文献   
58.
Pyrethroids are a class of insecticides that are becoming increasingly popular in agricultural and home use applications. Sensitive assays for pyrethroid insecticides in complex matrices are difficult with both instrumental and immunochemical methods. Environmental analysis of the pyrethroids by immunoassay requires either knowing which pyrethroids contaminate the source or the use of nonspecific antibodies with cross-reactivities to a class of compounds. We describe an alternative method that converts the type II pyrethroids to a common chemical product, 3-phenoxybenzoic acid (3-PBA), prior to analysis. This method is much more sensitive than detecting the parent compound, and it is much easier to detect a single compound rather than an entire class of compounds. This is useful in screening for pyrethroids as a class or in situations where a single type of pyrethroid is used. We demonstrated this technique in both citrus oils and environmental water samples with conversion rates of the pyrethroid to 3-PBA that range from 45 to 75% and methods that require no extraction steps for either the immunoassay or the liquid chromatography-tandem mass spectrometry (LC-MS/MS) techniques. Limits of detection for this technique applied to orange oil are 5 nM, 2 μM, and 0.8 μM when detected by LC-MS/MS, gas chromatography-mass spectrometry, and immunoassay, respectively. The limit of detection for pyrethroids in water when detected by immunoassay was 2 nM.  相似文献   
59.
Esterases play a crucial role in industrial chemical synthesis, maintaining normal physiological metabolism and detoxifying exogenous ester-containing toxicants. To meet the rapidly increasing industrial need for all kinds of esterases, especially enantioselective esterases used to generate highly pure chiral compounds, general substrates are necessary for rapid screening, monitoring, purification, and characterization. In this study, general fluorescent substrates including phenolic derivatives and alpha-cyanoesters were evaluated for sensitivity in detecting esterases in buffer systems. Results with two different esterases and different incubation times suggested that the alpha-cyanoesters examined were significantly more sensitive at detecting esterases than the corresponding tested phenolic derivatives. More importantly, alpha-cyanoesters, containing a secondary alcohol, possess at least one chiral center; thus, they are tools to screen for enantioselective hydrolysis. Results indicated that the enantioselectivity of esterases toward general alpha-cyanoesters strongly depended on the esterase and the substrate, but the majority of esterases examined preferred S-isomers to their corresponding R-enantiomers. Most appealing was the very high enantioselectivity displayed in cytosolic esterases of the house fly. The potential utility of such esterases is discussed. In addition, the use of alpha-cyanoesters as chiral fluorescent substrates was demonstrated for monitoring in enantioselective esterases.  相似文献   
60.
As some chlorophenols present in wood shavings have been shown to be microbiologically methylated to form anisoles, which have caused taint in broiler chickens, the anisoles from a number of phenols used in formulations of broiler house disinfectants were prepared. The sensory properties of these compounds were investigated in order to determine their potential for producing taint. None of these anisoles were found to be likely to cause taint if formed within the broiler house.  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