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   188篇
  免费   15篇
  国内免费   1篇
林业   4篇
农学   10篇
  24篇
综合类   10篇
农作物   57篇
水产渔业   8篇
畜牧兽医   80篇
园艺   2篇
植物保护   9篇
  2023年   2篇
  2022年   4篇
  2021年   12篇
  2020年   7篇
  2019年   6篇
  2018年   2篇
  2017年   6篇
  2016年   6篇
  2015年   12篇
  2014年   12篇
  2013年   17篇
  2012年   19篇
  2011年   19篇
  2010年   12篇
  2009年   7篇
  2008年   7篇
  2007年   12篇
  2006年   7篇
  2005年   8篇
  2004年   6篇
  2003年   4篇
  2002年   3篇
  2001年   4篇
  2000年   2篇
  1999年   2篇
  1997年   1篇
  1992年   1篇
  1990年   1篇
  1978年   1篇
  1972年   1篇
  1970年   1篇
排序方式: 共有204条查询结果,搜索用时 15 毫秒
151.
在检验过程中发现,关于粘稠液体的含量测定项下的取样方法不甚明了,实验操作过程产生的误差很大。因此笔者改进了取样方法,用相对密度折算或用内容量移液管量取,增加实验数据的准确度。  相似文献   
152.
The objectives of this study were to investigate the effects of polyvinyl alcohol (PVA) as a chemically defined compound in egg yolk (EY)‐free extender by determining the appropriate concentration of PVA and the effect of pH adjustment in EY‐free PVA extenders on dog spermatozoa. Spermatozoa (1 × 108 cells/ml) were frozen with EY‐free extenders supplemented with 0 (control), 0.025, 0.05, 0.1, 0.2 or 0.3 g/100 ml PVA. Sperm progressive motility (PM) was assessed immediately after thawing (IAT) and post‐thaw incubation (PTI), while viability, acrosome integrity and reactive oxygen species (ROS) levels were evaluated after PTI. Additionally, spermatozoa were frozen using EY‐free PVA extenders before pH adjustment (6.45) and after adjustment of pH (6.85). Viability, PM, ROS and gene expression (BCL2 and SMCP) were assessed. Supplementation with 0.05 g/100 ml or more PVA significantly increased PM compared to the control group in the IAT and PTI. Post‐thaw incubation significantly increased sperm motility in all groups. The acrosome integrity in all PVA groups was higher (p < .05) than the control without an effect on ROS and viability. Adjustment of the pH to 6.85 improved (p < .05) sperm PM compared to the non‐adjusted groups without affecting viability, ROS or expression of BCL2 and SMCP. We suggest that PVA supplementation in EY‐free Tris extenders can effectively protect dog spermatozoa during freezing and can maintain higher motility and acrosome integrity. Adjustment of pH in EY‐free PVA extenders can improve post‐thaw sperm motility. Therefore, PVA can be used as a compound in EY‐free extender for the cryopreservation of dog spermatozoa.  相似文献   
153.
Abdominal radiography is a standard diagnostic test for cats with suspected liver disease, however, absolute measurements of radiographic liver size can be affected by other factors such as positioning, radiographic technique, and obesity. This prospective and retrospective, analytical, cross‐sectional study evaluated the liver length/11th thoracic vertebral length (LL/T11) ratio as a method for minimizing these outside effects. In a prospectively recruited sample of 25 clinically healthy cats, measurements of radiographic LL/T11 ratio were compared with CT measurements of liver volume. Effects of radiographic technical factors (body posture, recumbency state, and beam center to LL/T11 ratio) and observer were also tested. In a retrospectively recruited sample of 324 cats with no evidence of liver disease, radiographic measurements of the LL/T11 ratio were performed using right lateral radiographs and compared among signalment groups (age, sex, body weight, and body condition score). There was a strong significant correlation between the LL/T11 ratio and CT liver volume (P < .001), and this ratio was not affected by radiographic technical factors. The reference value of the LL/T11 ratio was 4.22 ± 0.54 and the LL/T11 ratio did not differ among signalment groups. Findings supported the use of the LL/T11 ratio as a novel quantitative index of radiographic liver size in cats. Future studies in clinically affected cats are needed to further validate this method.  相似文献   
154.
Bovine tuberculosis (TB) is a major zoonosis that''s caused by Mycobacterium bovis (M. bovis). Being able to detect M. bovis is important to control bovine TB. We applied a molecular technique, the variable number tandem repeat (VNTR) typing method, to identify and distinguish the M. bovis isolates from Gyeonggi-do, Korea. From 2003 to 2004, 59 M. bovis clinical strains were isolated from dairy cattle in Gyeonggi-do, Korea, and these cattle had tuberculosis-like lesions. Twenty-four published MIRU-VNTR markers were applied to the M. bovis isolates and ten of them showed allelic diversity. The most discriminatory locus for the M. bovis isolates in Korea was QUB 3336 (h = 0.64). QUB 26 and MIRU 31 also showed high discriminative power (h = 0.35). The allelic diversity by the combination of all VNTR loci was 0.86. Six loci (MIRU 31, ETR-A and QUB-18, -26, -3232, -3336) displayed valuable allelic diversity. Twelve genotypes were identified from the 59 M. bovis isolates that originated from 20 cattle farms that were dispersed throughout the region of Gyenggi-do. Two genotypes [designation index (d.i.) = e, g] showed the highest prevalence (20% of the total farms). For the multiple outbreaks on three farms, two successive outbreaks were caused by the same genotype at two farms. Interestingly, the third outbreak at one farm was caused by both a new genotype and a previous genotype. In conclusion, this study suggests that MIRU-VNTR typing is useful to identify and distinguish the M. bovis isolates from Gyeonggi-do, Korea.  相似文献   
155.
Splenic hemangiosarcoma has morphological similarities to benign nodular hyperplasia. Computed tomography (CT) texture analysis can analyze the texture of images that the naive human eye cannot detect. Recently, there have been attempts to incorporate CT texture analysis with artificial intelligence in human medicine. This retrospective, analytical design study aimed to assess the feasibility of CT texture analysis in splenic masses and investigate predictive biomarkers of splenic hemangiosarcoma in dogs. Parameters for dogs with hemangiosarcoma and nodular hyperplasia were compared, and an independent parameter that could differentiate between them was selected. Discriminant analysis was performed to assess the ability to discriminate the two splenic masses and compare the relative importance of the parameters. A total of 23 dogs were sampled, including 16 splenic nodular hyperplasia and seven hemangiosarcoma. In each dog, total 38 radiomic parameters were extracted from first-, second-, and higher-order matrices. Thirteen parameters had significant differences between hemangiosarcoma and nodular hyperplasia. Skewness in the first-order matrix and GLRLM_LGRE and GLZLM_ZLNU in the second, higher-order matrix were determined as independent parameters. A discriminant equation consisting of skewness, GLZLM_LGZE, and GLZLM_ZLNU was derived, and the cross-validation verification result showed an accuracy of 95.7%. Skewness was the most influential parameter for the discrimination of the two masses. The study results supported using CT texture analysis to help differentiate hemangiosarcoma from nodular hyperplasia in dogs. This new diagnostic approach can be used for developing future machine learning-based texture analysis tools.  相似文献   
156.
Administration of immunosuppressive doses of glucocorticosteroids is the traditional primary treatment in necrotizing meningoencephalitis (NME) in dogs. However, response is variable and clinical signs often recur quickly with tapering dosage. Prognosis is poor and long-term therapy causes many complications. In the present study, we compared the long-term effects of combination (cyclosporine plus prednisolone) therapy with sole prednisolone therapy in management in dogs with NME. All NME cases in this study were examined with magnetic resonance imaging and cerebrospinal fluid analysis, and confirmed by histopathologic examination. The mean survival time of combination therapy group was 305.7 +/- 94.7 days. The mean survival time of sole prednisolone therapy group was 58.3 +/- 30.5 days. This case report demonstrates that combination treatment of cyclosporine with prednisolone is more effective in survival time than administration of only prednisolone in NME cases.  相似文献   
157.
The dispersion polymerization of styrene using a poly(4-vinylpyridine) (P4VP) macromolecular RAFT (macro-RAFT) agent as both a macro-initiator and a colloidal stabilizer under UV radiation was investigated for the first time. The P4VP macro-RAFT agent (M n,GPC=49,000 g/mol, PDI=1.14) was prepared by the RAFT polymerization of 4-vinylpyridine using 2-cyanoprop-2-yl dithiobenzoate as a chain transfer agent. The resulting polystyrene (PSt) particles had hairy P4VP chains, which could successfully immobilize very small Au nanoparticles on the surface of the PSt particles. It was found that hairy polymeric particles could be produced by photo-initiated dispersion polymerizations of vinyl monomers using macro-RAFT agents that are susceptible to UV radiation as both macro-initiators and colloidal stabilizers.  相似文献   
158.
Cereal seed storage proteins are encoded by complex multigene families and their subunit profiles are highly related to end-use qualities. Each fraction of albumin and hordein was extracted and its subunit profile was evaluated in related to malt and grain quality parameters. The purpose of this study was to provide selection criteria for high quality malting barley using grain and malt quality parameters and biochemical-genetic information. Grain and malt quality of 13 local adaptability test (LAT) lines were evaluated for malting process. A total of 16 germplasm accessions of high or low seed storage protein content were also evaluated for biochemicalgenetic analysis. The correlation coefficients among quality parameters were analyzed. Several important quality parameters in brewing process showed significant positive or negative correlations. Seed storage protein subunits of albumin and hordein of all tested lines and accessions were evaluated using 12% 1D SDS-PAGE. Scored data of protein subunit’s presence or absence was applied to Agglomerative Hierarchical Clustering (AHC) for statistical analysis and showed specific grouping patterns among tested lines. Clustered lines with subunit information were highly related with agricultural performance and grain and malt qualities. Based on the profiles of seed storage protein subunits, association of hordein subunit of 38, 43, and 65 kDa with high malt scored lines was found. The obtained results would provide improved selection criteria for high quality malting barley in the malting barley breeding program.  相似文献   
159.
Following the previous studies regarding blue and yellow dyes, a series of new red dyes having different length of alkyl substituents on the same chromophore were synthesized in order to dye unmodified polypropylene fiber. The affinity of the dyes onto unmodified polypropylene fiber was increased with the increase of the length of alkyl substituents. Therefore, the longest hexyl-substituted dye showed very deep shade of dyeing with K/S value of around 30 at maximum absorption wavelength. Within the range below 2 % o.w.f., the exhaustion (%) showed more than 80 %. The color fastnesses to washing, rubbing, and light of the dyeings were also improved greater for the dyes having longer alkyl substituents than the shorter ones. Since color hue of the dyes exhibited very strong red, they could be considered to be used as the primary red color dyes for unmodified polypropylene fibers.  相似文献   
160.
Clogging effects on nonwoven geotextile filters can reduce the drainage capacity of vertical drainage materials installed in clay deposits. The preceding clogging retention improvement can be increased if the nonwoven geotextile filter is treated by negative ion material in accordance to the knowledge that fine soil particle is negatively charged material. In this study, column tests were conducted to examine the effects of negative-ion treatment by using various types of ion-treated nonwoven geotextile filters. It was found that the negative ion treatment gave apparent increase of drainage capacity after long time as describe on this paper. Clogging effects of two nonwoven geotextile filters treated by negative ion (10 %; NI-10 and 20 %; NI-20) were compared to non-ion treated one (control) by long term filtration test. Finally, the highest drainage capacity was obtained by NI-20 followed by NI-10.  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