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   215篇
  免费   12篇
  国内免费   5篇
林业   11篇
农学   2篇
基础科学   2篇
  46篇
综合类   49篇
农作物   26篇
水产渔业   22篇
畜牧兽医   61篇
园艺   1篇
植物保护   12篇
  2024年   1篇
  2023年   3篇
  2022年   13篇
  2021年   11篇
  2020年   2篇
  2019年   7篇
  2018年   3篇
  2017年   6篇
  2016年   7篇
  2015年   4篇
  2014年   8篇
  2013年   5篇
  2012年   15篇
  2011年   13篇
  2010年   11篇
  2009年   6篇
  2008年   11篇
  2007年   12篇
  2006年   7篇
  2005年   6篇
  2004年   9篇
  2003年   5篇
  2002年   9篇
  2001年   9篇
  2000年   2篇
  1999年   6篇
  1998年   1篇
  1997年   4篇
  1996年   4篇
  1995年   3篇
  1994年   1篇
  1993年   3篇
  1992年   3篇
  1991年   1篇
  1990年   2篇
  1988年   2篇
  1987年   4篇
  1986年   1篇
  1985年   1篇
  1982年   1篇
  1979年   2篇
  1975年   1篇
  1973年   2篇
  1972年   1篇
  1971年   1篇
  1967年   1篇
  1964年   1篇
  1963年   1篇
排序方式: 共有232条查询结果,搜索用时 78 毫秒
51.
Neutrophil gelatinase‐associated lipocalin (NGAL) is a new biomarker for renal injury. It is also involved in tumorigenesis of different human cancer types. The oncogenic role of NGAL is related to its molecular forms, and heterodimer formation with matrix metalloproteinase 9 (MMP9) promotes human breast cancer (HBC) invasion and metastasis. To date, the levels of NGAL and NGAL/MMP9 complex have not yet been explored in canine mammary tumours (CMTs). Hence, this study aimed to investigate whether NGAL and its molecular forms could be the biomarker for CMT diagnosis. To this end, expression profile of NGAL and MMP9 in mammary epithelial cells as well as in urine samples were detected. By immunohistochemistry staining, NGAL was expressed at variable levels. Unlike HBC, a significant reduction in NGAL expression was demonstrated in benign and malignant CMTs as compared with normal controls. Additionally, NGAL expression was significantly reduced in dogs with metastatic CMTs. By contrast, the mean score of MMP9 expression in ascending order was normal groups, benign, and malignant CMTs. Interestingly, analysis of the molecular form revealed the NGAL/MMP9 complex presents in most mammary tissues and urine of dogs with benign or malignant CMTs, whereas the complex was absent in samples from dogs without CMTs. In conclusion, NGAL and MMP9 are ubiquitously expressed in canine mammary epithelial cells in normal and cancerous status. However, the NGAL/MMP9 complex exclusively presents in mammary tissues and urine of dogs with tumours.  相似文献   
52.
不同密度杉木林分生物量结构与土壤肥力差异研究   总被引:19,自引:0,他引:19  
林开敏  俞新妥 《林业科学》1996,32(5):385-391
对29年生五种造林密度生物量结构及土壤肥力进行了全面研究,结果表明:平均单株及其各器官生物量随密度增加呈递减趋势;单位面积不同密度的杉木林分生物量及其生产力基本趋于一致;各种密度单位面积现存枯枝落叶量随密度增加而增加,而林下植被生长及其生物量则相反;五种密度林分土壤自然含水量、最大持水量和毛管持水量基本上以2805株/hm2和3750株/hm2较大;土壤非毛管孔隙度,毛管孔隙度和总孔隙度均随密度增加而增大;土壤有机质、全N、全P、水解N和速效P的含量随密度增加而下降;而速效钾含量变化规律性不明显。因此,杉木初植密度尽量控制在2805—3750株/hm2之间,以利于杉木产量提高和地力维护。  相似文献   
53.
杉木人工林林下植物对土壤肥力的影响   总被引:12,自引:0,他引:12  
在29 a不同密度杉木林分内,对不同林下植物覆盖度和生物量梯度与土壤肥力的关系进行研究,研究结果表明杉木林下植物的平均高、总覆盖度和生物量均随杉木林分密度的增加呈现明显的递减趋势;林下植物对土壤水分和孔隙状况有一定程度的改善作用,但0~20 cm和20~40cm土层的有机质、全N、全P、水解N和速效P的含量基本上呈现出随林下植物覆盖度的增加而增加的趋势,并且以O~20cm尤为明显,这说明林下植物具有促进营养元素在地表富集的作用.因此,保护和恢复林下植物对杉木林地力的维护具有重要的意义.  相似文献   
54.
Alpha-chaconine, isolated from Solanum tuberosum Linn., is a naturally occurring steroidal glycoalkaloid in potato sprouts. Some reports demonstrated that alpha-chaconine had various anticarcinogenic properties. The aim of this study is to investigate the inhibitory effect of alpha-chaconine on lung adenocarcinoma cell metastasis in vitro. We chose the highly metastatic A549 cells, which were treated with various concentrations of alpha-chaconine to clarify the potential of inhibiting A549 cells invasion and migration. Data showed that alpha-chaconine inhibited A549 cell invasion/migration according to wound healing assay and Boyden chamber assay. Our results also showed that alpha-chaconine could inhibit phosphorylation of c-Jun N-terminal kinase (JNK) and Akt, whereas it did not affected phosphorylation of extracellular signal regulating kinase (ERK) and p38. In addition, alpha-chaconine significantly decreased the nuclear level of nuclear factor kappa B (NF-kappaB) and the binding ability of NF-kappaB. These results suggested that alpha-chaconine inhibited A549 cell metastasis by a reduction of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) activities involving suppression of phosphoinositide 3-kinase/Akt/NF-kappaB (PI3K/Akt/NF-kappaB) signaling pathway. Inhibiting metastasis by alpha-chaconine might offer a pivotal mechanism for its effective chemotherapeutic action.  相似文献   
55.
Intestinal helminth and protozoan infection in the quarantined dogs in Taiwan were examined using fecal examination between January to December, 2004. Of the 376 dogs imported from 11 countries, 63 (16.8%) were found to be infected with at least one species of intestinal parasite. The parasites detected were oocysts of Isospora canis and eggs of Toxocara canis, Trichuris vulpis and hookworms. Of the 63 infected dogs, 11 were found to have a mixed infection of two different species of parasites. This paper illustrates that parasites are transmitted from one country to another through the transport of animals. Moreover, there is also a possibility of parasitic infection among quarantined dogs as well as the zoonotic potential for quarantine officers during the quarantine period.  相似文献   
56.
The purpose of this study was to evaluate the effects of dietary Chinese medicinal herbs (CMH) supplementation composed of Panax ginseng, Dioscoreaceae opposite, Atractylodes macrocephala, Glycyrrhiza uralensis, Ziziphus jujube and Platycodon grandiflorum, on the performance, intestinal tract morphology and immune activity in weanling pigs. Two hundred and forty weaned pigs were assigned randomly to four dietary groups including the negative control (basal diet), 0.1% CMH, 0.3% CMH and 0.114% antibiotic (Chlortetracycline calcium Complex, Sulfathiazole and Procaine Penicillin G) supplementation groups for a 28-day feeding trial. Results indicated that both CMH supplementation groups had a better gain and feed/gain than control group (CT) during the first 2 weeks of the experimental period. The 0.3% CMH had a significant decrease in the diarrhoea score in first 10 days of experimental period when compared with other groups. The CMH supplementation groups had a higher villous height, increased lactobacilli counts in digesta of ileum and decreased coliform counts in colon compared with CT. The immune activities of polymorphonuclear leucocytes (PMNs), including the respiratory burst and Salmonella-killing ability, were significantly enhanced in CMH supplementation groups at day 7 of experiment period. The CMH and antibiotic supplementations increased the nutrient digestibility such as dietary dry matter, crude protein and gross energy in weanling pigs. In conclusion, the dietary CMH supplementation improved intestinal morphology and immune activities of PMNs, thus giving rise to nutrient digestibility and reduce diarrhoea frequency in weanling pigs.  相似文献   
57.
Objective – To compare cardiac output (CO) measured by use of lithium dilution (LiDCO) and ultrasound velocity dilution (UDCO) in conditions of high, intermediate, and low CO in anesthetized foals.
Design – Original prospective study.
Setting – University teaching hospital.
Animals – Six foals 1–3 days of age (38–45 kg).
Interventions – Neonatal foals were anesthetized and instrumented to measure direct blood pressure, heart rate, arterial blood gases, and CO. The CO was measured by use of LiDCO and UDCO techniques. Measurements were obtained from each foal at baseline and during low, intermediate, and high CO states. Measurements were converted to cardiac index (cardiac index=CO/body weight) values for statistical analysis. Agreement between the 2 methods was determined using Bland and Altman analysis and concordance correlation coefficients.
Measurements and Main Results – LiDCO determinations of CO ranged between 4.0 and 14.0 L/min resulting in cardiac index ranging between 75.5 and 310 mL/kg/min. There was no significant effect of blood pressure variation on bias or relative bias ( P =0.62 and 0.93, respectively). The mean bias and relative bias of UDCO (±SD) compared with LiDCO were −20.1±39.2 mL/kg/min and −7.7±23.4%, respectively. Concordance correlation coefficient between LiDCO and UDCO was 0.833.
Conclusions – When compared with LiDCO, the UDCO technique has acceptable clinical utility for measuring CO in healthy anesthetized newborn foals.  相似文献   
58.
A dog that was referred to the University of Florida Veterinary Medical Center was discovered to have a bamboo skewer within the right atrium and right ventricle, traversing the tricuspid valve. The skewer was ingested approximately four months prior to referral and was partially removed via gastrotomy. The presenting complaint at the time of referral included coagulopathy, anemia and leukocytosis. A linear, hyperechoic structure was identified in the right heart during an echocardiogram. The foreign body was suspected to be a portion of the skewer that the patient had previously ingested. Cardiopulmonary bypass was performed and the foreign body was removed successfully. Complications following surgery included the development of tricuspid valve and ventricular wall thrombi, atrial flutter and amiodarone toxicity. Many indications have been described in the veterinary literature for cardiopulmonary bypass. However, to the best of the authors' knowledge, successful removal of an intracardiac foreign body with cardiopulmonary bypass has not been reported in a veterinary patient. This represents a new indication for cardiopulmonary bypass in veterinary medicine.  相似文献   
59.
An increase of 11–31% of dry mycelial mass was observed along with a slight decrease (5–10%) in aflatoxin Bi production in 5-day-old aflatoxigenicAspergillus spp. submerged cultures containing either 0.5 ml or 1.0 ml clarified neem oil (CNO) in 0.1 % Triton solution. Fungal growth and aflatoxin B1 production were also determined in potato-dextrose-agar petri plate cultures inoculated with aflatoxigenicAspergillus spp. containing an atmosphere of volatiles emitted from 0.25 ml, 0.5 ml, and 1.0 ml CNO added to the plates. After 5 days’ incubation, fungal radial growth was reduced by 7–29% and aflatoxin B1 production by 0–67%. GC/MS analysis of the head space volatiles of the CNO indicated that the reduction of fungal growth and aflatoxin B1 was probably due to low molecular weight hydrocarbons, aldehydes, alcohols, and sulfur compounds emitted at 30°C in the dry culture. These results suggest that volatiles emitted from CNO at 30° C in plate cultures were more fungistatic and consequently inhibited aflatoxin production more than neem oil added in liquid cultures.  相似文献   
60.
Our aim was to evaluate the inspection of arriving passengers for the illegal transport of animal products through the international airport into Taiwan. Passenger-violation data were retrieved from the Bureau of Animal and Plant Health Inspection and Quarantine (BAPHIQ) in Taiwan. Monte Carlo simulations with 5000 iterations were applied to estimate the predicted violation numbers considering factors such as passenger's nationality/ethnicity, sex, and monthly statistics of violations. The results showed that Chinese-related passengers and passengers from South East Asian countries have a relatively higher potential risk for incurring violations during the period from Christmas to Chinese Lunar New Year. Most monthly estimated violation risks are significantly higher than observed violation risks in 2001 and 2002, except April, July, and August. Due to the low sensitivity of the current detection system (reflected by the higher estimated violation risks and a two-fold detection increase after the implementation of an inspection service using detector dogs), we recommend additional preventive measures be taken.  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