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   174篇
  免费   17篇
林业   9篇
农学   2篇
  31篇
综合类   30篇
水产渔业   22篇
畜牧兽医   91篇
植物保护   6篇
  2020年   3篇
  2019年   5篇
  2018年   3篇
  2017年   8篇
  2016年   5篇
  2015年   3篇
  2014年   4篇
  2013年   17篇
  2012年   5篇
  2011年   7篇
  2010年   3篇
  2009年   3篇
  2007年   5篇
  2006年   4篇
  2005年   7篇
  2004年   5篇
  2003年   5篇
  2002年   2篇
  2001年   3篇
  2000年   3篇
  1999年   2篇
  1998年   2篇
  1995年   2篇
  1994年   2篇
  1992年   4篇
  1991年   4篇
  1990年   5篇
  1989年   2篇
  1988年   2篇
  1987年   2篇
  1985年   3篇
  1983年   2篇
  1978年   3篇
  1975年   2篇
  1974年   2篇
  1973年   2篇
  1972年   5篇
  1970年   11篇
  1969年   3篇
  1968年   3篇
  1967年   3篇
  1966年   3篇
  1965年   2篇
  1951年   1篇
  1940年   1篇
  1938年   1篇
  1937年   3篇
  1936年   2篇
  1935年   1篇
  1934年   1篇
排序方式: 共有191条查询结果,搜索用时 46 毫秒
101.
The anadromous allis shad Alosa alosa has suffered dramatic population declines throughout Europe and is currently considered as endangered throughout its entire distribution range. In order to reestablish allis shad in the River Rhine, which formerly housed one of the largest and most important populations, an EU‐LIFE Project ‘The re‐introduction of allis shad in the Rhine system’ was started in 2007. In course of the LIFE+ Projects, allis shad larvae bred from genitor fish of the Gironde–Garonne–Dordogne population in France were reared in a pilot ex situ stock plant pilot facility in Aßlar, Germany. At an age of 1–2 months, about 100% of these fish developed approximately 0.5‐ to 0.8‐cm large, fluid‐filled, transparent cysts in conjunction with the upper jaw. The performed microbiological, virological, parasitological and histological examinations did not detect any infectious agents. Possible causative agents are discussed with regard to environmental factors and the nutrition of larvae. In conclusion, the observed malformations are considered a sign for a severe health problem and therefore a risk for the successful breeding of allis shad in aquaculture.  相似文献   
102.
Koi herpesvirus (KHV) causes KHV disease (KHVD). The virus is highly contagious in carp or koi and can induce a high mortality. Latency and, in some cases, a lack of signs presents a challenge for virus detection. Appropriate immunological detection methods for anti‐KHV antibodies have not yet been fully validated for KHV. Therefore, it was developed and validated an enzyme‐linked immunosorbent assay (ELISA) to detect KHV antibodies. The assay was optimized with respect to plates, buffers, antigens and assay conditions. It demonstrated high diagnostic and analytical sensitivity and specificity and was particularly useful at the pond or farm levels. Considering the scale of the carp and koi industry worldwide, this assay represents an important practical tool for the indirect detection of KHV, also in the absence of clinical signs.  相似文献   
103.
A novel permanently growing brain cell line from koi (Cyprinus carpio L.) (KB cell line) was established, and its suitability for detection of koi herpesvirus (KHV) was demonstrated in this study. The KB cell line was optimally maintained at 27°C in Leibovitz's L‐15 medium supplemented with 10% foetal bovine serum (FBS). It was subcultured more than 100 times, and chromosome analysis revealed that 51.54% of KB cells at passage 80 maintained the abnormal diploid chromosome number 2n = 96 while the modal chromosome number was 2n = 100. The cell line was cryopreserved in liquid nitrogen at ?196°C and was recovered from storage after 1 year with good cell viability and vitality. The results of virus isolation demonstrated that KB cells were susceptible to KHV, which was shown by the presence of an obvious cytopathic effect and abundant virus particles. The viral titres of KHV in KB reached 105.73TCID50/0.1 ml within 7 days. Immunofluorescence and Western blot assays confirmed that KB replicated KHV. The newly established KB cell line will serve as a useful tool to elucidate KHV disease (KHVD) pathogenesis.  相似文献   
104.
Purified and concentrated preparations of virus from liver extracts of infected rabbits contain virus specific components with sedimentation coefficients of about 175, 110 and sometimes 133S and more slow units. Full and empty virus particles with a diameter of about 34 nm were shown electron microscopically in the corresponding 175 and 110S fractions of the sucrose density gradient. The average of buoyant density of the 175, 133, 110S and more slow units are 1.36, 1.32 and 1.31 g/ml respectively. The extinction coefficient E260 nm is 4.3 +/- 0.7 cm2/mg. The RNA content is 17 +/- 4%. SDS-PAGE shows a "65" kD protein as a single or major component. Beside smaller polypeptides with lower intensities, the 67 kD polypeptide reacts positively in the Western blot with polyclonal antibodies of rabbits. The molecular weight of the virus is 15 +/- 4 x 10(6)D. The pH stability of the 175S unit was also tested.  相似文献   
105.
The brain extracellular matrix (ECM) has attracted growing interest due to its highly regulated spatiotemporal expression during development and maturation of central nervous system. The present study deals with the post-natal appearance and transformation into adult distribution patterns of the ECM components related to proteoglycans (PGs) and glycoproteins (GPs) in the retrosplenial cortex (RSC) of albino rats at birth (P0), 1 week (P1), P2, P3, P4, P5, P6, P7 and P8. The differentiating PGs and GPs components of the ECM were shown to make their appearance as early as 1–2 weeks post-natally. At this developmental stage, these components of the ECM appeared in association with some neurons and glia cells or diffusely localized at the neutrophill. Interestingly, Golgi complexes of labelled neurons were usually stained with lectin VVA or WFA, and this labelling dramatically disappeared on reaching P4. During P2–3, the pericoated neuronal cells underwent a progressive increment in number, and presented an inside-out pattern of migration and differentiation (toward the V-II cortical layers). On reaching P4, most of the coated neurons appeared distributed into the cortical layer IV and II. At a later stage (P5–8), the overall density and intensity of labelled neurons progressively increased and apparently reached the adult stage of development. They also displayed the usual differential labelling characteristics, after using the cationic iron colloid/lectin staining, for the first time at this juncture. The present findings indicated that the perineuronal ECM components are significantly correlated with age and suggest a possible developmental or biological significance including promotion of migration, as well as functional maturation of the retrosplenial neurons.  相似文献   
106.
The aim of this study was to document the expression and localization of VEGF system comprising of VEGF isoforms (VEGF 120, VEGF 164 and VEGF 188) and their receptors (VEGFR1 and VEGFR2) in buffalo corpus luteum (CL) obtained from different stages of the oestrous cycle. Real‐time RT‐PCR (qPCR), Western blot and immunohistochemistry were applied to investigate mRNA expression, protein expression and localization of examined factors. In general, all the components of VEGF system (the VEGF isoforms and their receptors) were found in the water buffalo CL during the oestrous cycle. The mRNA as well as protein expression of VEGF system was highest during the early and mid‐luteal phase, which later steadily decreased (p < 0.05) after day 10 to reach the lowest level in regressed CL. As demonstrated by immunohistochemistry, VEGF protein was localized predominantly in luteal cells; however, VEGFR1 and VEGFR2 were localized in luteal cells as well as in endothelial cells. In conclusion, the dynamics of expression and localization of VEGF system in buffalo corpora lutea during the luteal phase were demonstrated in this study, indicating the possible role of VEGF system in the regulation of luteal angiogenesis and proliferation of luteal as well as endothelial cells through their non‐angiogenic function.  相似文献   
107.
108.
Tryptophan-N-glucoside in fruits and fruit juices   总被引:1,自引:0,他引:1  
In extracts prepared from various fruits as well as in fruit juices a single tryptophan glycoconjugate was detected by HPLC-MS analysis. Product ion spectra demonstrated the N-glycosidic linkage of a hexose moiety to the indole nitrogen. For structure elucidation, the novel tryptophan glycoside was isolated from pear juice and identified as N(1)-(beta-D-glucopyranosyl-(4)C(1))-L-tryptophan by (1)H, HH-COSY and (13)C NMR spectroscopy. Finally, we disclosed the biosynthetic origin of the novel tryptophan metabolite by demonstrating the enzymatic glycosylation of deuterium-labeled tryptophan, which was applied to pear fruit.  相似文献   
109.
110.
Zusammenfassung Isolierte Embryonen von Weizen, Roggen, Hafer und Mais wachsen unter sterilen Bedingungen auf anorganischem Nährmedium zu schwächlichen, aber (im Licht) lebensfähigen Keimlingen heran. Embryonen von Gerste sind dagegen auch im Licht nur bei Zusatz von Glucose zum Nährmedium entwicklungsfähig. Das in verschiedenen Fällen beobachtete geringere Wachstum der Koleoptilen im Dunkeln gegenüber den Lichtkulturen ist wahrscheinlich auf Kohlenhydrat-Mangel zurückzuführen, der im Licht durch einsetzende Photosynthese ausgeglichen wird. Licht wirkt fördernd auf das Wurzelwachstum. Für Embryonen von Sommer- und Winterroggen auf Glucose-Medium im Dunkeln liegt das Wachstumsoptimum übereinstimmend bei 18 °C; bei niedrigeren oder höheren Temperaturen bestehen dagegen Unterschiede. Eine Vorquellung der Karyopsen vor der Exstirpation der Embryonen fördert deren Entwicklung; offenbar treten während der ersten Stunden der Quellung wachstumsfördernde Substanzen aus dem Endosperm über, wobei es sich nicht um Kohlenhydrate handelt.
Summary Isolated embryos of wheat, rye, oats, and maize cultivated under sterile conditions on inorganic nutrient grow up to weakly but (in light) viable seedlings. Embryos of barley, however, develop even in light only after addition of glucose to the nutrient. Depressed growth of coleoptiles in the dark as observed in different cases in comparison with light cultures probably is due to a lack of carbohydrates, which is compensated in light by photosynthesis. Light promotes root growth. In the dark, upon glucose medium, optimum growth in embryos of spring and winter rye is reached conformably at 18 °C, but differences were found at lower and higher temperatures. Presoaking of caryopses before exstirpation of embryos stimulates their development; obviously during the first hours of soaking growth-promoting substances (but not carbohydrates) pass over from the endosperm.

am ¶rt;au , , , ( ) . . , , , , , , . . 18 °C , ; . ; - , .
  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