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   269篇
  免费   93篇
  国内免费   2篇
林业   1篇
  4篇
综合类   21篇
农作物   4篇
水产渔业   31篇
畜牧兽医   295篇
园艺   4篇
植物保护   4篇
  2023年   4篇
  2021年   3篇
  2020年   12篇
  2019年   6篇
  2018年   11篇
  2017年   7篇
  2016年   14篇
  2015年   7篇
  2014年   17篇
  2013年   22篇
  2012年   6篇
  2011年   7篇
  2010年   12篇
  2009年   15篇
  2008年   5篇
  2007年   6篇
  2006年   8篇
  2005年   5篇
  2004年   6篇
  2003年   9篇
  2002年   5篇
  2001年   4篇
  2000年   5篇
  1999年   7篇
  1998年   17篇
  1997年   14篇
  1996年   12篇
  1995年   10篇
  1994年   3篇
  1993年   6篇
  1992年   8篇
  1991年   9篇
  1990年   7篇
  1989年   11篇
  1988年   6篇
  1987年   5篇
  1986年   4篇
  1985年   5篇
  1984年   5篇
  1983年   2篇
  1982年   2篇
  1980年   6篇
  1979年   6篇
  1978年   3篇
  1977年   2篇
  1976年   3篇
  1975年   4篇
  1974年   5篇
  1973年   3篇
  1940年   1篇
排序方式: 共有364条查询结果,搜索用时 15 毫秒
111.
The use of Piromen, a polysaccharide complex of Pseudomonas aeroginosa, has been investigated in 21 calves by a test of marrow granulocyte reserves. The maximal increase in peripheral granulocytes (ΔG) was determined following multiple intravenous and sub-cutaneous injections of Piromen at various time intervals and was correlated with the mature marrow granulocytes on bone marrow smear differentials. Five ug Piromen per kg body weight, by the subcutaneous route, was found to give a mean ΔG of 5200/mm3, very similar to the ΔG of 5300/mm3 obtained in man with 0.1 ug/kg intravenous Piromen injections. Clinical effects in calves were minimal with the subcutaneous route as compared to the response following intravenous Piromen injections.  相似文献   
112.
The pathogenesis of early prepatent Fascioloides magna infection was investigated in seven fawns (Odocoileus virginianus) given 500 metacercariae and examined at one, two, three, five, eight, 12 and 13 weeks postinoculation. Blood samples were taken from eight inoculated deer every two weeks up to 16 weeks postinoculation. Eosinophilia with a mild transitory anemia were the main clincopathological features. Postmortem examination at two weeks postinoculation revealed extensive migration of immature flukes. Subcapsular tracks in the liver, nodules on the blind sacs of the rumen, as well as retroperitoneal granulomas on flanks and necrotic tracks on the diaphragm were found. Evidence of penetration of flukes into the lung was found at two weeks postinoculation and there was early granuloma formation at three weeks postinoculation. Flukes migrating into tissues other than the liver were destroyed in large granulomas, although remnants of degenerating parasites were not found. At eight weeks postinoculation, widespread granuloma formation characterized the infection with this lesion present in nodes along the gastrointestinal tract, in the mesentery, flanks, psoas muscles, diaphragm, between the ribs and in the lungs. By 12 weeks postinoculation subcapsular tracks were observed in the liver.  相似文献   
113.
Safety evaluations of two thermotolerant filamentous fungi, Cephalosporium eichhorniae 152 (C. 152) and Rhizopus chinensis 180 (R. 180), grown on a sugar-salts medium were carried out through feeding the biomases to rats at 20% or 40% dietary levels for 90 days. There was a control group fed soybean meal. Weight gain and feed consumption for rats fed 20% C. 152 were equal to those for the control animals, but were depressed in the other three groups, especially the rats fed R. 180. All animals appeared normal and healthy except that transient alopecia was found for a short duration in the fungi-treated rats in the initial period. The cause of this lesion is not clear. At the end of the feeding trial, clinical determinations of constituents in blood and urine samples were conducted. The animals were autopsied and weights for four organs were taken. Histopathological examinations for 26 different tissues were carried out. Mild changes were found in both C. 152 and R. 180-treated rats but most of the these were not considered to be related to treatment.  相似文献   
114.
115.
AIMS: To investigate the cause of an outbreak of ovine abortion in 1996 in a flock of 300 two-tooth (rising 2-year-old) ewes vaccinated against Campylobacter fetus fetus infection and to subsequently characterise the strain of C. fetus fetus isolated from aborted foetuses. METHODS: Standard bacteriological methods were used to identify C. fetus fetus isolates which were then antigenically typed and subjected to pulsed-field gel electrophoresis (PFGE) and compared to the vaccine strain. RESULTS: C. fetus fetus was identified as the causal agent of the abortions despite the ewes having been vaccinated before ram introduction and at the time of ram removal. Four isolates cultured from aborted material were indistinguishable when compared using antigenic typing and PFGE, but all differed from the vaccine strain. CONCLUSIONS: Within the limitations of the available typing systems, it is proposed that PFGE may be a useful tool to establish the distribution and strain variation of C. fetus fetus. CLINICAL RELEVANCE: This field case indicates the need for further study of non-vaccine C. fetus fetus strains which cause abortion in vaccinated ewes, and of the importance of these strains to the New Zealand sheep industry.  相似文献   
116.
117.
118.
Apoptosis in the testis is required to ensure an efficient spermatogenesis. However, sometimes, defective germ cells that are marked for elimination during this process escape elimination in the testes, giving rise to ejaculates with increased percentages of abnormal and apoptotic spermatozoa and a high percentage of apoptotic bodies. Apoptosis markers in the ejaculate have been associated with low fertility, either in animals or humans. Therefore, the goal of this study was to investigate whether fresh equine semen contains apoptotic bodies [initially named Merocyanine 540 (M540) bodies] and to study the relationship between the quantity of these bodies and cell concentration, the volume of ejaculate, viability and motility. Moreover, we also studied whether the presence apoptotic bodies in fresh semen was related to the resistance of the stallion spermatozoa to being incubated at 37°C or being frozen and thawed. Fresh equine semen was stained with fluorescent dyes such as M540 and Annexin‐V. Active Caspase 3 was studied in fresh semen through Western blotting and immunofluorescence with a specific antibody. Sperm kinematics was assessed in fresh, incubated and thawed samples using computer‐assisted semen analysis, and viability was evaluated with the LIVE/DEAD Sperm Viability Kit. Overall, our results demonstrate for the first time the presence of apoptotic bodies in equine semen. The quantity of apoptotic bodies was highly variable among stallions and was positively correlated with Caspase 3 activity in fresh samples and negatively correlated with the viability and motility of stallion spermatozoa after the cryopreservation process.  相似文献   
119.
Semen from a Western Finncattle bull exhibiting a highly polymorphic spermiogram was processed by colloid centrifugation using Androcoll‐B, a species‐specific silane‐coated silica colloid. In the first experiment, Single Layer Centrifugation (SLC) was used to identify which density colloids were needed to separate different cell populations. Colloids of the two chosen densities were then used in a density gradient resulting in two sperm subpopulations, one containing nearly all normally sized spermatozoa and the other enriched for the macrocephalic spermatozoa. Microcephalic spermatozoa did not appear in either of the selected subpopulations. Using a combination of SLC and DGC with this species‐specific colloid, it was possible to separate the spermatozoa into different subpopulations, that is, a subpopulation containing nearly all normally sized spermatozoa, and another one enriched for the macrocephalic spermatozoa. Thus, colloid centrifugation could be used to select sufficient normal spermatozoa from a highly polymorphic ejaculate for AI, if desired.  相似文献   
120.
This study was performed to evaluate plasma concentrations of anti‐Mullerian hormone (AMH) and the ovarian antral follicle population (AFP) in different genetic groups. Cyclic heifers (13 Bubalus bubalis [Murrah]; 15 Bos taurus [Holstein] and 10 Bos indicus [Gyr]) were maintained under the same management and were synchronized with two doses of 150 μg IM d‐cloprostenol administered 14 days apart. After the second d‐cloprostenol treatment, heifers had their ovaries scanned daily by ultrasound to define the day of ovulation. On the same day, the AFP was determined and a plasma sample was collected to measure AMH. Murrah heifers had less AFP (25.6 ± 2.1 follicles; p = 0.01) and plasma AMH concentration (0.18 ± 0.03 ng/ml; p < 0.001) than Gyr (60.0 ± 12.2 follicles and 0.60 ± 0.12 ng/ml of AMH); however, data were similar when compared to Holstein (35.9 ± 6.8 follicles and 0.24 ± 0.06 ng/ml of AMH) heifers. Regardless of genetic background, there was a positive relationship between the AFP and plasmatic AMH concentration (Murrah [r = 0.62; p < 0.01], Holstein [r = 0.66; p < 0.001] and Gyr [r = 0.88; p < 0.001]). Also, when heifers were classified according to high‐ or low‐AMH concentration based on the average within each genetic group, high‐AMH heifers had greater (p < 0.0001) AFP than low‐AMH heifers. In conclusion, both Murrah and Holstein heifers presented lower plasma AMH concentration and AFP when compared to Gyr.  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