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   291篇
  免费   13篇
  国内免费   1篇
林业   38篇
农学   5篇
  34篇
综合类   16篇
农作物   5篇
水产渔业   45篇
畜牧兽医   144篇
园艺   1篇
植物保护   17篇
  2022年   1篇
  2021年   6篇
  2020年   8篇
  2019年   4篇
  2018年   5篇
  2017年   4篇
  2016年   3篇
  2015年   9篇
  2014年   11篇
  2013年   7篇
  2012年   13篇
  2011年   18篇
  2010年   7篇
  2009年   14篇
  2008年   19篇
  2007年   19篇
  2006年   19篇
  2005年   17篇
  2004年   11篇
  2003年   11篇
  2002年   19篇
  2001年   13篇
  2000年   11篇
  1999年   12篇
  1998年   5篇
  1997年   3篇
  1996年   3篇
  1994年   1篇
  1992年   2篇
  1991年   7篇
  1990年   3篇
  1989年   2篇
  1988年   6篇
  1987年   3篇
  1986年   1篇
  1985年   4篇
  1984年   1篇
  1982年   1篇
  1980年   1篇
  1977年   1篇
排序方式: 共有305条查询结果,搜索用时 890 毫秒
81.
A female stillborn Holstein calf with shortened cervical and thoracic regions, protrusion of the tongue, and bilateral symmetric flexural contraction of the anterior limbs was delivered on gestation day 281. Multiple hemivertebrae, fused and misshaped vertebrae, synostosis and scoliosis of cervical, thoracic and lumbar vertebral column were found in the affected calf by radiographic and computed tomographic (CT) analysis. Ten pairs of ribs were present and the sternum consisted of 9 sternebrae. Multiple morphologic abnormalities including fusion, malformation, and displacement, were found in the ribs and sternum. Cardiac anomalies, including atrial septal defect and hypertrophy of right ventricle, were observed. DNA-polymerase chain reaction (PCR) analysis demonstrated that amplified product from the liver DNA of the affected calf had identical pattern to that associated with complex vertebral malformation (CVM) of Holstein calves and that her dam was a heterozygous carrier of CVM. The affected calf was diagnosed as having CVM based on the DNA-PCR results and the characteristic findings, and was recorded as a first documentation of CVM confirmed in a Holstein calf in Japan.  相似文献   
82.
The effects of rice blast fungicides known to inhibit melanisation or penetration on the adhesion of Pyricularia oryzae to the leaf surface of barley were investigated. Adhering appressoria were counted after shaking inoculated leaves vigorously with water. On untreated leaves, appressoria began to adhere at the time when appressorial melanisation was initiated. The number of adhering appressoria then increased gradually, and most were melanised. On chlobenthiazone-treated leaves, appressoria were not melanised and were easily detached from the surface. Similar results were obtained with tricyclazole. However, after treatment with tetrachlorophthalide or pentachlorobenzyl alcohol, which are also known to prevent penetration of P. oryzae, melanised appressoria still remained after shaking in water. It is suggested that appressorial melanisation in P. oryzae is involved in appressorial adhesion. The antipenetrant action of the melanin biosynthesis inhibitors chlobenthiazone and tricyclazole may be ascribed to the lack of adhesive intensity necessary to support the mechanical shearing of the cuticle of rice plants.  相似文献   
83.
The development of a layout plan for a new plant with the aid of genetic algorithms was studied to place the machines so that the plant floor was effectively utilized and the operation would not be impeded. Genetic algorithms are search algorithms based on the mechanics of natural evolution and natural genetics to solve problems in engineering fields. Simulation with the aid of genetic algorithms was undertaken step by step. The first seven hundred strings (chromosomes) were generated at random to organize an initial population. Each string consisted of 40 bits (genes), which represented characteristics of machines (x- andy-coordinates and inlet and outlet formations of materials on machines) in the binary coding. Then the simulation was undertaken by repeating selection, crossover, reproduction, and mutation of strings until all strings were saturated with the highest evaluation (fitness of chromosomes to environments in the case of creatures). Under some limitations, an acceptable layout plan of the modeled plant involving four wood-processing machines was obtained according to evaluation indices.Part III of this series appeared inMokuzai Gakkaishi 37: 702–710, 1991.Part of this report was presented at the 47th annual meeting of the Japan Wood Research Society, Kocht, April 1997  相似文献   
84.
The thermal diffusivity, specific heat, and thermal conductivity of 13 species of wood were measured by means of the laser flash method to investigate the thermal properties of wood during the heating process. The temperature ranged from room temperature to 270°C in air or under vacuum. The thermal diffusivity varied little during the heating process up to 240°C. The values in air were larger than those under vacuum. There was a linear relation between the specific heat and the ambient temperature, and the specific heat under vacuum was larger than that in air at high temperature. The thermal conductivity increased with density and the ambient temperature. To discuss the effects of the atmospheric conditions on the thermal constants of wood, a theoretical model of thermal conductivity was proposed and its validity examined, where the wood was assumed to be a uniformly distributed material composed of cell walls and air.Part of this paper was presented at the 47th annual meeting of Japan Wood Research Society at Kochi, April 1997  相似文献   
85.
A method for measuring the viscoelastic properties of wood under high temperature and high pressure steam was developed using a testing machine with a built-in autoclave. A newly developed load cell capable of resisting a steam pressure of 16kgf/cm2 and a temperature of 200°C was installed in the autoclave. This load cell could be used to determine precisely the loads while steaming at temperatures from 100°C to 200°C. In addition to load-detection problems, it was necessary to avoid the nonuniform thermal degradation of wood during the measurement process under steaming at high temperatures. This nonuniform degradation could be minimized by shortening the time required for the wood to attain thermal equilibrium using specimens conditioned to the fiber saturation point. According to this method, a stress relaxation curve for sugi (Cryptomeria japonica D. Don) wood being compressed while steaming at 180°C was obtained. The stress was seen to decrease rapidly with time, reaching almost zero at 3000s.  相似文献   
86.
Two groups of red sea bream (average body weight 85 g) were fed to satiation fish meal (FM) or FM‐free soy protein concentrate (SPC)‐based diet (FM‐sat and SPC groups respectively). A third group (FM‐pair) was fed the same amount of FM as of SPC fed to SPC‐sat group for 6 weeks. Growth rate of SPC group was significantly slower than of FM‐sat and FM‐pair groups (p < 0.05). Feed conversion ratios of FM‐sat and FM‐pair groups were similar and were better than that of SPC group (p < 0.05). Visceral fat somatic index of SPC group was significantly lower than of the other groups (p < 0.05), while that of the latter two groups were similar. Plasma triglyceride of FM‐sat and FM‐pair groups was similar and lower than the level of SPC group (p < 0.05). Trypsin activity in hepatopancreas of SPC group was significantly lower than that of other groups (p < 0.05). We suggest a low growth of SPC group was not simply related to low‐feed intake. Feeding of a FM‐free SPC‐based diet may reduce lipid accumulation and consequently lead to low‐growth performance, in red sea bream.  相似文献   
87.
88.
A series of novel 6-(1,2,4-triazol-4-yl) chromone and -1-thiochromone (benzo[b]thiazin-4-one) derivatives was obtained by cyclisation via thiosemicarbazides which were prepared by reaction of hydrazines and the corresponding isothiocyanates. Their fungicidal activity was evaluated against the rice blast fungus Pyricularia oryzae. Of this series, 2,5,8-trimethyl-6-(1-propyl-5-thioxo-3-trifluoromethyl-1,2,4-triazol-4-yl) chromone, 6-(1-butyl-5-thioxo-3-trifluoromethyl-1,2,4-triazol-4-yl)-2,5,8-trimethylchromone, 6-(1-hexyl-3-methyl-5-thioxo-1,2,4-triazol-4-yl)-2,5,8-trimethylchromone and 6-(1-allyl-5-thioxo-3-trifluoromethyl-1,2,4-triazol-4-yl)-2,5,8-trimethylchromone were highly active (pEC50>6·0). Structure–activity relationship studies using the capacity factor k′ as a hydrophobicity index suggested that the log k′ optimum for 2,5,8-trimethyl-chromone and -1-thiochromone derivatives was around 1·0, equivalent to a log Pow value of c. 4·4. © 1998 SCI  相似文献   
89.
An enzyme-linked immunosorbent assay was developed for the determination of canine beta2-microglobulin (beta2-m) in plasma and urine. The detectable sensitivity for pure canine beta2-m was 0.05 microg/l and the analytical range was 0.1 to 50 microg/l. The mean analytical recovery when pure canine beta2-m was added to normal plasma was 101.9%. The mean analytical recovery in the urine was 102.1%. The intra-day variation coefficient was 3.1% in plasma, 4.3% in serum and 1.9% in urine. No difference was found between the concentration of beta2-m in plasma and serum (n=17). The concentration of beta2-m in the plasma of normal dogs was 1.82 +/- 0.57 mg/l (n=31). The mean excretion in 24 hr urine collected from normal dogs was 17.6 +/- 9.2 microg/l, 0.22 +/- 0.12 microg/kg of body weight or 14.2 +/- 9.4 microg/g of urine creatinine. The beta2-m creatinine index of random urine samples was 23.5 +/- 16.6 microg/g (n=26). There was a close correlation between the beta2-m creatinine index of 24 hr urine samples and that of random urine samples (r=0.872).  相似文献   
90.
Recently, we demonstrated the presence of IL-1 beta in the colostral whey from dairy cows. Here, authors examined oral transmission of colostral IL-1 beta and its immunological effects on the neonatal calves. Biotin-labeled recombinant bovine (rb) IL-1 beta was administered orally to newborn calves and monitored in the serum. The results disclosed the passive transfer of colostral cytokines via the oral route, and a potent increase in white blood cell (WBC) count was observed in all calves administered with rbIL-1 beta. Oral administration of IL-1 beta significantly increased the proliferation of peripheral blood mononuclear cells (PBMCs) stimulated with concanavalin A, and the O(2)(-) production of stimulates neutrophils in newborn calves. These results suggest that the oral administration of IL-1 beta has an immunostimulatory activity in the newborn calf.  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