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   79篇
  免费   4篇
  国内免费   1篇
林业   4篇
农学   2篇
  2篇
综合类   9篇
水产渔业   6篇
畜牧兽医   50篇
园艺   4篇
植物保护   7篇
  2020年   1篇
  2018年   3篇
  2017年   3篇
  2016年   2篇
  2013年   4篇
  2012年   5篇
  2011年   2篇
  2010年   3篇
  2009年   4篇
  2008年   6篇
  2007年   5篇
  2006年   8篇
  2005年   1篇
  2004年   9篇
  2003年   3篇
  2002年   5篇
  2001年   3篇
  2000年   2篇
  1999年   2篇
  1996年   1篇
  1995年   1篇
  1994年   1篇
  1992年   1篇
  1991年   2篇
  1990年   2篇
  1989年   2篇
  1988年   1篇
  1969年   1篇
  1966年   1篇
排序方式: 共有84条查询结果,搜索用时 31 毫秒
1.
Yield management is important subject in modern grape growing and winter pruning and cluster thinning treatments were used for yield control. Standard cluster thinning is generally labor intensive and expensive method and grape growers try to new methods, which are alternative to cluster thinning for reducing berry set. The goal of the present research was to investigate the effects of chemical thinning treatments such as ethephon (ETH), gibberellic acid (GA3), naphthalene acetic acid (NAA) and non-chemical thinning treatments such as early leaf removal (ELR) and standard cluster thinning (SCT) on decreasing grape yield and enhancing berry composition of cv. Shiraz. In this study, percentages of berry set of cv. Shiraz were decreased by both chemical and non-chemical thinning treatments compared to Control. The results from these two different thinning methods shown certainly significant differences in berry composition of cv. Shiraz. Eventually, the best results in improved quality characteristics of cv. Shiraz were obtained from ELR treatment and treatments of ELR, ETH, GA3, NAA and SCT successively resulted in considerable enhancements in quality attributes of cv. Shiraz.  相似文献   
2.
The weight of internal organs (swimbladder, kidney, liver, spleen) in relation to the body weight was studied in common carp fingerlings divided into three groups on the basis of swimbladder appearance and microscopic examination of the kidney. The fish had been collected from different Hungarian fish farms at the time when swimbladder inflammation (SBI) usually occurs (in July and August). The first group comprised fish with severe signs of SBI and massive renal sphaerosporosis, the second group consisted of fish with milder swimbladder changes and/or kidney infection by a low number of Sphaerospora renicola, while the third group was constituted by infection-free common carp fry. Statistical analysis of swimbladder, kidney, liver and spleen weight in relation to the body weight revealed that in the infected groups the internal organs were substantially enlarged. This suggests that in common carp fry with SBI the swimbladder changes are accompanied by reno-, hepato- and splenomegaly.  相似文献   
3.
Besides the well-known O157:H7 clone causing enterohaemorrhagic colitis and haemolytic uraemic syndrome in Europe, Japan and North America, the number of Escherichia coli isolates with non-motile (NM) phenotype has considerably increased. We supposed that spontaneous antibiotic resistance mutation could cause this phenotypic change. To model our hypothesis we isolated rifampicin--(Rif) and ampicillin--(Amp) resistant mutants from E. coli O157:H7 prototype strains 7785 and EDL933. Among Rifr mutants we could isolate strains with no or reduced motility, while the Ampr mutants became hypermotile. The biochemical profile of the mutants had not changed but phage sensitivity and generation time of the mutants were altered. Among the representative strains we did not find polymorphism with Southern blot analysis and no polymorphism was found in the fliC gene of the mutants. The described characteristics have proven to be stable. In a mice virulence assay by intravenous infections the virulence of the derivatives was also found to be changed. In summary, we found that the antibiotic-resistant phenotype in E. coli O157:H7 was coexpressed with several other phenotypic changes including motility and virulence. It can be assumed that expression of the involved phenotypes may be under the influence of a common regulatory cascade. Further work is needed to identify the components and mechanism of this regulatory system.  相似文献   
4.
Left ventricular systolic function was assessed in 12 healthy dogs with equilibrium radionuclide ventriculography. The results of the analysis were compared to traditional echocardiographic measurements. Left ventricular internal dimensions and volume were measured at the time of end-systole and end-diastole. Ejection fraction--one of the most informative parameters of cardiac function--was calculated in each animal. Values (e.g. EDD, ESD, EDV, ESV) measured by the scintigraphic method were significantly (Student's t-test, p < 0.05) higher than the data obtained by echocardiography. Ejection fraction (EF) was the only parameter that did not differ significantly when comparing the two imaging techniques. The difference between the results of parallel measurements was in inverse ratio to the size of the heart.  相似文献   
5.
Myxobolus pseudodispar (Gorbunova) is a common parasite of the muscle of roach, Rutilus rutilus L., whereas its actinosporean development occurs in two oligochaete alternate hosts. This paper reports the complete developmental cycle of this parasite in the oligochaete alternate host Tubifex tubifex and the roach. In laboratory experiments, parasite-free T. tubifex specimens were infected by myxospores of M. pseudodispar collected from roach in Lake Balaton. Parasite-free roach fingerlings were infected with floating triactinospores (TAMs) released from oligochaetes on day 69 after challenge. Young plasmodia and spores in roach were first recorded on day 80 post-exposure (p.e.). Myxospores collected from experimentally infected roach initiated a new development in T. tubifex and the resulting TAMs infected roach. No infection of roach resulted from feeding oligochaetes containing mature triactinospores.  相似文献   
6.
The spectrum of water vapor is of fundamental importance for a variety of processes, including the absorption and retention of sunlight in Earth's atmosphere. Therefore, there has long been an urgent need for a robust and accurate predictive model for this spectrum. In our work on the high-resolution spectrum of water, we report first-principles calculations that approach experimental accuracy. To achieve this, we performed exceptionally large electronic structure calculations and considered a variety of effects, including quantum electrodynamics, which have routinely been neglected in studies of small many-electron molecules. The high accuracy of the resulting ab initio procedure is demonstrated for the main isotopomers of water.  相似文献   
7.
The acid-base status of 58 calves (all in normal anterior presentation) was determined from venous blood samples before the onset of traction and immediately after vaginal delivery. Calves were assigned to one of three groups according to their blood pH value: group 1 - normal, pH greater than 7.2; group 2 - acidotic, pH 7.2 to 7.0; group 3 - severely acidotic, pH less than 7.0. Before the onset of traction (i.e. during the 30 minutes following the appearance and rupture of the membranes), 43 calves (74.1%) had normal acid-base values, 14 (24.1%) had slight acidosis, and only 1 (1.7%) had severe acidosis. At birth the three groups of calves showed the following distribution: 23 (39.7%) were normal, 29 (50%) had slight acidosis, and 6 (10.3%) had severe acidosis. Seven calves (12.1%) died during birth or within 48 hours after birth; 2 were normal shortly before birth, 4 were acidotic shortly before birth, and 1 was severely acidotic even before the onset of traction. Traction was significantly longer for cows that delivered severely acidotic calves compared to cows in the other two groups.  相似文献   
8.
Altered nursing or nutrition before artificial insemination (AI) can be used as a doe biostimulant to improve lactating rabbits reproduction. The timing of a shift from free to a 3-day controlled nursing to AI or the nursing method at fast-refeeding can affect the efficacy of these stimulations. In an earlier study the effects of a 3-day controlled nursing on days 8, 9 and 10 or in controlled nursing rabbits, the impact of a 24-h fast with 48–50 h re-feeding were investigated. This follow-up work tested a 3-day biostimulation with controlled nursing on days 9, 10 and 11. Another aim was to assess the same doe fast-refeeding but now in free-nursing rabbits. Pannon White does (n=480) were artificially inseminated 11 days post-partum. Control (C) does nursed freely. Rabbits simulating local farm practice (F) had controlled nursing until day 14 using a metal-plate as separation and then free nursing to weaning (day 35). In biostimulations with altered nursing, there was a shift from free to a 3-day controlled nursing (days 9–11) with a wire-mesh separation (BW), a metal-plate insertion (BM) or nest-tray removal (BN) and return to free nursing on day 12 until weaning. The C, F, BW, BM and BN does were fed ad libitum. At biostimulation with fast-refeeding (BF), the free-nursing does were subjected to a 24 h water-only fast between days 8 and 9 and a 48–50 h ad libitum re-feeding before AI. Doe reproduction and growth of the current litter were differently affected by the treatments. In the C, F, BW, BM, BN and BF does, sexual receptivity was 83, 90, 68, 80, 74 and 85% (P=0.05), the kindling rate was 79, 76, 74, 89, 68, 70% (P=0.05), the number of kits born alive was 7.9, 8.0, 8.8, 9.1, 7.9, 6.8 (P=0.005), kit weight at weaning 982, 991, 953, 986, 955, 964 g (P=0.012) and at 70 days of age 2383, 2407, 2220, 2350, 2279, 2382 g, respectively (P=0.001). Among biostimulations with altered nursing, the 3-day controlled nursing with a metal-plate separation (BM) can be advised for the practice because only this method was efficient in this (days 9–11) and previous (days 8–10) studies. There appears to be an interaction between doe nursing and feeding, since the same fast led to different production of free-nursing does compared to those in a previous work that nursed controlled.  相似文献   
9.
Little information is known about infection, replication and transmission of porcine circovirus type 2 (PCV2) in species other than swine. Two sets of animal experiments were carried out to investigate the susceptibility of mice to PCV2 and to study their possible role in maintaining and transmitting the virus. In the first experiment 14 mice were inoculated with PCV2 by the intraperitoneal route with 5 x 10(2) TCID50 of the PCV2-ROM strain (Cadar et al., 2007). In a second experiment 24 mice were divided into two groups (A and B); mice in Group A (n = 18) were inoculated orally with 1 x 10(5) TCID50 PCV2-ROM and mice in Group B (n = 6) were left uninoculated until day 12 post inoculation (p.i.), when they were mixed with Group A. The animals were sacrificed at intervals for postmortem investigation and virus genome detection by polymerase chain reaction (PCR). The PCR results indicated that PCV2 could replicate in mice infected intraperitoneally or by the oral route, and that the virus can be transmitted directly from mouse to mouse.  相似文献   
10.
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