全文获取类型
收费全文 | 20422篇 |
免费 | 4047篇 |
国内免费 | 1153篇 |
专业分类
林业 | 1533篇 |
农学 | 2234篇 |
基础科学 | 975篇 |
3641篇 | |
综合类 | 3303篇 |
农作物 | 1321篇 |
水产渔业 | 3213篇 |
畜牧兽医 | 6876篇 |
园艺 | 450篇 |
植物保护 | 2076篇 |
出版年
2024年 | 32篇 |
2023年 | 141篇 |
2022年 | 363篇 |
2021年 | 756篇 |
2020年 | 902篇 |
2019年 | 1452篇 |
2018年 | 1267篇 |
2017年 | 1427篇 |
2016年 | 1383篇 |
2015年 | 1364篇 |
2014年 | 1424篇 |
2013年 | 1724篇 |
2012年 | 1485篇 |
2011年 | 1499篇 |
2010年 | 1465篇 |
2009年 | 1049篇 |
2008年 | 1024篇 |
2007年 | 940篇 |
2006年 | 905篇 |
2005年 | 836篇 |
2004年 | 559篇 |
2003年 | 486篇 |
2002年 | 429篇 |
2001年 | 404篇 |
2000年 | 402篇 |
1999年 | 259篇 |
1998年 | 221篇 |
1997年 | 196篇 |
1996年 | 201篇 |
1995年 | 165篇 |
1994年 | 136篇 |
1993年 | 128篇 |
1992年 | 110篇 |
1991年 | 76篇 |
1990年 | 94篇 |
1989年 | 70篇 |
1988年 | 50篇 |
1987年 | 28篇 |
1986年 | 30篇 |
1985年 | 12篇 |
1984年 | 13篇 |
1983年 | 11篇 |
1982年 | 12篇 |
1980年 | 6篇 |
1978年 | 17篇 |
1977年 | 9篇 |
1975年 | 7篇 |
1974年 | 8篇 |
1972年 | 6篇 |
1970年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
921.
A. Valencakova‐Agyagosova Z. Frischova Z. Sevcikova J. Hajurka J. Lepej I. Szakallova G. Kredatusova V. Nagy V. Ledecky 《Veterinary and comparative oncology》2014,12(3):205-214
The aim of this work was to determine levels of carcinoembryonic antigen (CEA) and cancer antigen (CA 15‐3) in the blood serum of 45 bitches. A modified procedure was used to determine the CEA and CA 15‐3 markers with the human kits using the radioimmunoassay method. Samples collected from extirpated tumour of mammary glands were histologically processed and classified as per WHO guidelines. The average age of animals with tumour was 10.00 ± 2.2 years; for healthy bitches average age was 4.2 ± 3.2 years. Values of CEA and CA 15‐3 were considered positive, if they exceeded 0.23 ng mL?1 and 7 IU mL?1, respectively. Average levels of CEA in the tumour group were 0.25 ± 0.06 versus 0.20 ± 0.03 in healthy bitches (P = 0.0001). The average CA 15‐3 value in bitches with tumour was 8.58 ± 1.27 versus 5.14 ± 1.34 in healthy animals (P < 0.0001). 相似文献
922.
923.
924.
Juliana Abranches Soares Almeida Yanhong Liu Minho Song Jeong Jae Lee H Rex Gaskins Carol Wolfgang Maddox Orlando Osuna James Eugene Pettigrew 《畜牧与生物技术杂志(英文版)》2014,(2):173-180
An experiment was conducted to determine how an E. coil challenge and dietary clays affect the intestinal barrier of pigs. Two groups of 32 pigs (initial BW: 6.9 ± 1.0 kg) were distributed in a 2 x 4 factorial arrangement of a randomized complete block design (2 challenge treatments: sham or E. coil, and 4 dietary treatments: control, 0.3% smectite A, 0.3% smectite B and 0.3% zeolite), with 8 replicates total. Diarrhea score, growth performance, goblet cell size and number, bacterial translocation from intestinal lumen to lymph nodes, intestinal morphology, and relative amounts of sulfo and sialo mucins were measured. The E. coli challenge reduced performance, increased goblet cell size and number in the ileum, increased bacterial translocation from the intestinal lumen to the lymph nodes, and increased ileal crypt depth. One of the clays (smectite A) tended to increase goblet cell size in ileum, which may indicate enhanced protection. In conclusion, E. coli infection degrades intestinal barrier integrity but smectite A may enhance it. 相似文献
925.
H. Bair‐Brake T. Bell A. Higgins N. Bailey M. Duda S. Shapiro H. E. Eves N. Marano G. Galland 《Zoonoses and public health》2014,61(2):97-104
Bushmeat, defined as meat derived from wild animals, is a potential source of zoonotic pathogens. Bushmeat from restricted animals is illegal to import into the United States under US federal regulations. We reviewed US Centers for Disease Control and Prevention (CDC) port of entry surveillance records from September 2005 through December 2010 and conducted focus group studies to describe trends in and reasons for bushmeat importation into the United States. In total, 543 confiscated bushmeat items were recorded. Half of the confiscated bushmeat items identified were rodents. Africa was the most frequent continent of origin. Seasonality was evident, with bushmeat confiscations peaking in late spring to early summer. Four times more bushmeat was confiscated during an enhanced surveillance period in June 2010 compared with the same period in previous years, suggesting that routine surveillance underestimated the amount of bushmeat detected at US Ports of Entry. Focus groups held in three major US cities revealed that bushmeat importation is a multifaceted issue. Longstanding cultural practices of hunting and eating bushmeat make it difficult for consumers to acknowledge potential health and ecologic risks. Also, US merchants selling African goods, including bushmeat, in their stores have caused confusion among importers as to whether importation is truly illegal. Enhancing routine surveillance for bushmeat and consistent enforcement of penalties at all ports of entry, along with health education aimed at bushmeat importers, might be useful to deter illegal importation. 相似文献
926.
Rogelio AGUILAR‐AGUILAR Andrés MARTÍNEZ‐AQUINO Héctor ESPINOSA‐PÉREZ Gerardo PÉREZ‐PONCE DE LEÓN 《Integrative zoology》2014,9(3):328-339
As part of an ongoing inventory of the helminth parasites of freshwater fishes in Mexico, 570 individual fish were collected between Apr 2008 and Oct 2011 in 26 localities along the Cuatro Ciénegas region in Coahuila State, northern Mexico. Seventeen species of hosts, mostly corresponding to Nearctic freshwater elements, were studied. A total of 8324 individual worms were collected during this survey, representing 25 species of helminths, of which 9 were digeneans, 3 monogeneans, 3 acanthocephalans, 9 nematodes and 1 cestode. Most of the records in this checklist represent new host or locality records. The information provided in this checklist may be helpful for our understanding of the biodiversity and historical biogeography of this host–parasite system, because in the Cuatro Ciénegas region occur a Nearctic freshwater fish fauna, along with Neotropical and endemic elements, and from a biogeographical point of view, this may represent a transitional area. 相似文献
927.
W. R. B. Sylvester V. Amadi R. Pinckney C. N. L. Macpherson J. S. McKibben R. Bruhl‐Day R. Johnson H. Hariharan 《Zoonoses and public health》2014,61(6):436-441
Cloacal swabs from 62 green iguanas (Iguana iguana), including 47 wild and 15 domestic ones from five parishes of Grenada, were sampled during a 4‐month period of January to April 2013 and examined by enrichment and selective culture for the presence of Salmonella spp. Fifty‐five per cent of the animals were positive, and eight serovars of Salmonella were isolated. The most common serovar was Rubislaw (58.8%), a serovar found recently in many cane toads in Grenada, followed by Oranienburg (14.7%), a serovar that has been causing serious human disease outbreaks in Japan. Serovar IV:48:g,z51:‐ (formerly, S. Marina) highly invasive and known for serious infections in children in the United States, constituted 11.8% of the isolates, all of them being from domestic green iguanas. Salmonella Newport, a serovar recently found in a blue land crab in Grenada, comprised 11.8% of the isolates from the green iguanas. The remaining four less frequent serovars included S. Javiana and S. Glostrup. Antimicrobial susceptibility tests conducted by a disc diffusion method against amoxicillin–clavulanic acid, ampicillin, cefotaxime, ceftazidime, ciprofloxacin, enrofloxacin, gentamicin, nalidixic acid, streptomycin, tetracycline and trimethoprim–sulfamethoxazole showed that drug resistance is minimal, with intermediate susceptibility, mainly to streptomycin, tetracycline and cefotaxime. This is the first report of isolation and antimicrobial susceptibilities of various Salmonella serovars from wild and domestic green iguanas in Grenada, West Indies. 相似文献
928.
R. E. Luna‐Gierke K. Wymore J. Sadlowski P. Clogher R. W. Gierke M. Tobin‐D'Angelo A. Palmer C. Medus C. Nicholson S. McGuire H. Martin K. Garman P. M. Griffin R. K. Mody 《Zoonoses and public health》2014,61(7):492-498
We describe multiple‐aetiology infections involving non‐O157 Shiga toxin‐producing Escherichia coli (STEC) identified through laboratory‐based surveillance in nine FoodNet sites from 2001 to 2010. A multiple‐aetiology infection (MEI) was defined as isolation of non‐O157 STEC and laboratory evidence of any of the other nine pathogens under surveillance or isolation of >1 non‐O157 STEC serogroup from the same person within a 7‐day period. We compared exposures of patients with MEI during 2001–2010 with those of patients with single‐aetiology non‐O157 STEC infections (SEI) during 2008–2009 and with those of the FoodNet population from a survey conducted during 2006–2007. In total, 1870 non‐O157 STEC infections were reported; 68 (3.6%) were MEI; 60 included pathogens other than non‐O157 STEC; and eight involved >1 serogroup of non‐O157 STEC. Of the 68 MEI, 21 (31%) were part of six outbreaks. STEC O111 was isolated in 44% of all MEI. Of patients with MEI, 50% had contact with farm animals compared with 29% (P < 0.01) of persons with SEI; this difference was driven by infections involving STEC O111. More patients with non‐outbreak‐associated MEI reported drinking well water (62%) than respondents in a population survey (19%) (P < 0.01). Drinking well water and having contact with animals may be important exposures for MEI, especially those involving STEC O111. 相似文献
929.
C. Burri F. Vial M.‐P. Ryser‐Degiorgis H. Schwermer K. Darling M. Reist N. Wu O. Beerli J. Schöning M. Cavassini A. Waldvogel 《Zoonoses and public health》2014,61(8):537-544
Hepatitis E is considered an emerging human viral disease in industrialized countries. Studies from Switzerland report a human seroprevalence of hepatitis E virus (HEV) of 2.6–21%, a range lower than in adjacent European countries. The aim of this study was to determine whether HEV seroprevalence in domestic pigs and wild boars is also lower in Switzerland and whether it is increasing and thus indicating that this zoonotic viral infection is emerging. Serum samples collected from 2,001 pigs in 2006 and 2011 and from 303 wild boars from 2008 to 2012 were analysed by ELISA for the presence of HEV‐specific antibodies. Overall HEV seroprevalence was 58.1% in domestic pigs and 12.5% in wild boars. Prevalence in domestic pigs was significantly higher in 2006 than in 2011. In conclusion, HEV seroprevalence in domestic pigs and wild boars in Switzerland is comparable with the seroprevalence in other countries and not increasing. Therefore, prevalence of HEV in humans must be related to other factors than prevalence in pigs or wild boars. 相似文献
930.
T. D. Procter D. L. Pearl R. L. Finley E. K. Leonard N. Janecko R. J. Reid‐Smith J. S. Weese A. S. Peregrine J. M. Sargeant 《Zoonoses and public health》2014,61(3):208-218
An estimated 6 million pet dogs live in Canadian households with the potential to transmit zoonotic pathogens to humans. Dogs have been identified as carriers of Salmonella, Giardia and Campylobacter spp., particularly Campylobacter upsaliensis, but little is known about the prevalence and risk factors for these pathogens in pet dogs that visit dog parks. This study examined the prevalence of these organisms in the faeces of dogs visiting dog parks in three cities in south‐western Ontario, as well as risk factors for shedding Campylobacter spp. and C. upsaliensis. From May to August 2009, canine faecal samples were collected at ten dog parks in the cities of Guelph and Kitchener‐Waterloo, Ontario, Canada. Owners were asked to complete a questionnaire related to pet characteristics and management factors including age, diet and activities in which the dog participates. Faecal samples were collected from 251 dogs, and 189 questionnaires were completed. Salmonella, Giardia and Campylobacter spp. were present in 1.2%, 6.4% and 43.0% of faecal samples, respectively. Of the Campylobacter spp. detected, 86.1% were C. upsaliensis, 13% were C. jejuni and 0.9% were C. coli. Statistically significant sparing factors associated with the shedding of Campylobacter spp. included the feeding of a commercial dry diet and the dog's exposure to compost. Age of dog had a quadratic effect, with young dogs and senior dogs having an increased probability of shedding Campylobacter spp. compared with adult dogs. The only statistically significant risk factor for shedding C. upsaliensis was outdoor water access including lakes and ditches, while dogs >1 year old were at a lower risk than young dogs. Understanding the pet‐related risk factors for Campylobacter spp. and C. upsaliensis shedding in dogs may help in the development of awareness and management strategies to potentially reduce the risk of transmitting this pathogen from dogs to humans. 相似文献