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   333篇
  免费   25篇
林业   5篇
农学   1篇
基础科学   1篇
  41篇
综合类   56篇
农作物   8篇
水产渔业   4篇
畜牧兽医   230篇
园艺   2篇
植物保护   10篇
  2021年   3篇
  2020年   5篇
  2018年   11篇
  2017年   7篇
  2016年   8篇
  2015年   5篇
  2014年   9篇
  2013年   12篇
  2012年   10篇
  2011年   13篇
  2010年   12篇
  2009年   5篇
  2008年   11篇
  2007年   7篇
  2006年   18篇
  2005年   13篇
  2004年   15篇
  2003年   11篇
  2002年   9篇
  2001年   5篇
  2000年   7篇
  1999年   5篇
  1998年   6篇
  1997年   6篇
  1996年   3篇
  1995年   3篇
  1994年   5篇
  1992年   3篇
  1991年   5篇
  1990年   5篇
  1989年   7篇
  1988年   5篇
  1987年   5篇
  1986年   6篇
  1985年   7篇
  1984年   7篇
  1982年   3篇
  1981年   3篇
  1976年   3篇
  1975年   4篇
  1974年   4篇
  1973年   4篇
  1972年   7篇
  1971年   6篇
  1970年   5篇
  1968年   5篇
  1967年   6篇
  1966年   5篇
  1963年   4篇
  1954年   2篇
排序方式: 共有358条查询结果,搜索用时 19 毫秒
91.
92.
93.
Four trials, three in the United States and one in South Africa, were conducted to evaluate the potential value of a novel self-medicating applicator in the passive control of gastrointestinal nematodes in cattle and deer, and of files and ticks on cattle using oil-based treatments. The results of the trials demonstrated that this applicator is an effective and practical device for the passive treatment of both deer and cattle for trichostrongyle infections using the endectocide, moxidectin (Cydectin. Fort Dodge Animal Health, USA), of cattle for hom fly (Haemotobia irritans) infestations using the insecticide, cyfluthrin (CyLence, Bayer AG, Germany) and of cattle for tick infestations (in particular Amblyomma hebraeum and Rhipicephalus appendiculatus) using the acaricides deltamethrin and amitraz (Delete All, Intervet, South Africa).  相似文献   
94.
Epitopes on the α‐gliadins are known to give rise to immune responses that may lead to the development of celiac disease in genetically predisposed individuals. The reduction of epitope levels in wheat‐based products would likely benefit this group of consumers and also consumers with non‐celiac gluten sensitivity. Conventional breeding of wheats with lowered epitope levels will take time, but in this study we show for the first time that milling technology can be used to produce flour mill streams that are depleted in α‐20 gliadin epitopes. Fifteen mill streams from two New Zealand wheat cultivars, Sapphire (a biscuit wheat) and Monad (a bread wheat), were tested with reversed‐phase HPLC and an α‐20 gliadin epitope ELISA kit. The level of α‐20 epitope measured in Sapphire gliadins was significantly less than that found in Monad gliadins, even taking into account differences in total protein content. For both cultivars, compared with the straight‐run flour, the break flours had similar or significantly higher proportions of α‐20 epitope per unit of protein, whereas most of the reduction streams had significantly lower proportions of α‐20 epitope per unit of protein. Theoretically, combining selected (mainly reduction) flour streams may produce flour with ∼75% of the epitope content of the straight‐run flour.  相似文献   
95.
Interest in indicus–taurus cattle has been increasing, as these animals are likely to present the best characteristics of Zebu and European bovine breeds. The aim of this study was to compare the embryo production of indicus–taurus donors with high vs low antral follicle counts obtained by ovum pickup/in vitro production (OPU/IVP) and superovulation (SOV)/embryo collection. Braford females at weaning age (3/8 Nelore × 5/8 Hereford, n = 137, 9 ± 1 month old) were subjected to six serial ovarian ultrasonographs and were assigned to two groups according to the number of antral follicles ≥3 mm as follows: G‐High antral follicular count (AFC, n = 20, mean ≥40 follicles) and G‐Low AFC (n = 20, mean ≤10 follicles). When the females (n = 40) reached 24 months of age, they were subjected to both OPU/IVP and SOV/embryo collection. The average number of follicles remained highly stable throughout all of the ultrasound evaluations (range 0.90–0.92). The mean number of COCs recovered (36.90 ± 13.68 vs 5.80 ± 3.40) was higher (p < 0.05) for females with high AFC, resulting in higher (p < 0.05) numbers of total embryos among females with high vs low AFC (6.10 ± 4.51 vs 0.55 ± 0.83). The mean number of embryos per collection was also higher (p < 0.05) for G‐High vs G‐Low (6.95 ± 5.34 vs 1.9 ± 2.13). We conclude that a single ultrasound performed at pre‐pubertal ages to count antral follicles can be used as a predictor of embryo production following IVP and SOV/embryo collection in indicus–taurus females.  相似文献   
96.
Echolocation in bats: signal processing of echoes for target range   总被引:6,自引:0,他引:6  
Echolocating bats Eptesicus fuscus and Phyllostomus hastatus can discriminate between the nearer and farther of two targets. Their errors in discrimination are predicted accurately by the autocorrelation functions of their sonar cries. These bats behave as though they have an ideal sonar system which cross correlates the transmitted cry with the returning echo to extract targetrange information.  相似文献   
97.
The Voyager 2 photopolarimeter was reprogrammed prior to the August 1981 Saturn encounter to perform orthogonal-polarization, two-color measurements on Saturn, Titan, and the rings. Saturn's atmosphere has ultraviolet limb brightening in the mid-latitudes and pronounced polar darkening north of 65 degrees N. Titan's opaque atmosphere shows strong positive polarization at all phase angles (2.7 degrees to 154 degrees ), and no single-size spherical particle model appears to fit the data. A single radial stellar occultation of the darkened, shadowed rings indicated a ring thickness of less than 200 meters at several locations and clear evidence for density waves caused by satellite resonances. Multiple, very narrow strands of material were found in the Encke division and within the brightest single strand of the F ring.  相似文献   
98.
Target structure and echo spectral discrimination by echolocating bats   总被引:1,自引:0,他引:1  
Echolocating bats can use sonar to discriminate among targets which reflect echoes differing in spectral distribution of energy but not in overall intensity. They can detect differences smaller than 1 millimeter in fine target structure. Bats may be capable of classifying targets from echo spectral signatures and might thus be able to distinguish among flying insect prey by sonar.  相似文献   
99.
Measurement of urinary metanephrines in spot samples is used for the diagnosis of canine pheochromocytoma (PC). We describe a simple analytical method based on liquid chromatography tandem mass spectrometry (LC-MS/MS) for measuring free metanephrine (MN) and normetanephrine (NMN) in spot urine samples. Using the developed method, we evaluated the stability of urinary free-MN and free-NMN at various storing conditions. In addition, we assessed the feasibility of urinary free-MN and -NMN measurement for diagnosing PC. Urine samples were mixed with stable isotope internal standards and thereafter purified by ultrafiltration. The purified samples were analyzed by LC-MS/MS in the multiple reaction monitoring mode after separation on a multimode octa decyl silyl column. The coefficient of variation of free-MN and -NMN measurement was 7.6% and 5.5%, respectively. The linearity range was 0.5–10 µg/l for both analytes. Degradation was less than 10% for both analytes under any of the storage conditions. The median free-NMN ratio to creatinine of 9 PC dogs (595, range 144–47,961) was significantly higher (P<0.05) than that of 13 dogs with hypercortisolism (125, range 52–224) or 15 healthy dogs (85, range 50–117). The developed method is simple and may not require acidification of spot urine. The results of this preliminary retrospective study suggest that the measurement of urinary free metanephrines is a promising tool for diagnosing canine PC.  相似文献   
100.
A laboratory incubation experiment was conducted to study the effect of NH 4 + fixation/defixation on the added N interaction (ANI) in three Illinois Mollisols fertilized with 100 or 200 mg N kg-1 soil. A positive ANI was observed in all three soils, which was greater at the higher rate of applied N. However, very little exchange was observed between applied 15NH 4 + and the native clay-fixed NH 4 + , and the ANI observed were attributed largely to microbial immobilization-mineralization. The results suggested that variations in the NH 4 + fixation capacity of soils will not have a significant bearing on the interpretation of data obtained from studies of the ANI.  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