全文获取类型
收费全文 | 11470篇 |
免费 | 802篇 |
国内免费 | 114篇 |
专业分类
林业 | 1045篇 |
农学 | 480篇 |
基础科学 | 95篇 |
2950篇 | |
综合类 | 486篇 |
农作物 | 621篇 |
水产渔业 | 1244篇 |
畜牧兽医 | 4247篇 |
园艺 | 203篇 |
植物保护 | 1015篇 |
出版年
2024年 | 18篇 |
2023年 | 93篇 |
2022年 | 160篇 |
2021年 | 295篇 |
2020年 | 316篇 |
2019年 | 295篇 |
2018年 | 530篇 |
2017年 | 544篇 |
2016年 | 537篇 |
2015年 | 421篇 |
2014年 | 481篇 |
2013年 | 750篇 |
2012年 | 912篇 |
2011年 | 849篇 |
2010年 | 539篇 |
2009年 | 450篇 |
2008年 | 626篇 |
2007年 | 633篇 |
2006年 | 520篇 |
2005年 | 516篇 |
2004年 | 433篇 |
2003年 | 399篇 |
2002年 | 317篇 |
2001年 | 230篇 |
2000年 | 236篇 |
1999年 | 205篇 |
1998年 | 57篇 |
1997年 | 59篇 |
1996年 | 40篇 |
1995年 | 38篇 |
1994年 | 23篇 |
1993年 | 23篇 |
1992年 | 60篇 |
1991年 | 45篇 |
1990年 | 51篇 |
1989年 | 53篇 |
1988年 | 42篇 |
1987年 | 43篇 |
1986年 | 49篇 |
1985年 | 53篇 |
1984年 | 40篇 |
1983年 | 35篇 |
1982年 | 20篇 |
1979年 | 34篇 |
1978年 | 31篇 |
1977年 | 28篇 |
1974年 | 26篇 |
1973年 | 45篇 |
1972年 | 32篇 |
1971年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
Martínez J Segura P García D Aduriz G Ibabe JC Peris B Corpa JM 《Veterinary journal (London, England : 1997)》2006,172(2):382-385
A seven-year-old female Indian python (Python molurus) weighing about 35kg was euthanased after several clinical episodes of stomatitis, pneumonia, ophthalmitis and dystocia over a period of four years. The animal had been maintained in a terrarium in a circus truck at an adequate temperature. During shows, however, the snake was considered to be exposed to stressful conditions for several hours at a time at low temperatures and with noise and bright lights. A post-mortem examination indicated ulcerative stomatitis, osteomyelitis, severe pneumonia and numerous granulomata and multifocal necrosis in stomach and spleen. Corynebacterium macginleyi was isolated in pure culture from the ulcerative stomatitis, and mixed with Stenotrophomonas maltophilia from the lungs and spleen. The findings indicated that the snake had died from a septicaemic process caused by C. macginleyi, probably originating from the stomatitis. The role of S. maltophilia as a secondary agent is discussed. The stress of the circus show and poor husbandry may have predisposed the animal to infection and septicaemia. This is the first report of C. macginleyi causing disease in a snake. 相似文献
33.
Martínez-Larrañaga MR Anadón A Fernandez-Cruz ML Díaz MJ Martinez MA Frejo MT Martínez M Tafur M 《Journal of veterinary pharmacology and therapeutics》2000,23(1):37-44
The potential cytotoxic effects of the compounds 8-quinolinol, chloramine-T and natamycin have been studied in isolated pig hepatocytes. The relative cytotoxicity of these compounds was evaluated on the basis of the leakage of cytosolic lactate dehydrogenase (LDH), 3-(4,5 dimethyl)thiazol-2-yl,-2,5-diphenyl tetrazolium bromide (MTT) reduction by mitochondrial dehydrogenases, uptake of neutral red (NR) by cytosolic lysosomes, glutathion (GSH) depletion and oxidized glutathion (GSSG) efflux after 24 h exposure. Evaluation of the 20%, 50% and 80% reduced absorbance data obtained from the parameters NR20, NR50, and NR80, and MTT20, MTT50 and MTT80 enabled us to rank these compounds in decreasing order of cytotoxicity: 8-quinolinol > natamycin > chloramine-T. Also for the parameters LDH and GSH, chloramine-T appears to be less cytotoxic than natamycin and 8-quinolinol. Our study demonstrated that pig hepatocytes may be a useful model for examining cytotoxic events of drugs to be used in pigs, therefore avoiding possible extrapolation problems due to species differences. 相似文献
34.
Inmaculada Moreno Julio Álvarez Nerea García Santiago de la Fuente Irene Martínez Eloy Marino Alfredo Toraño Joaquin Goyache Felipe Vilas Lucas Domínguez Mercedes Domínguez 《Veterinary parasitology》2014,199(3-4):264-267
An outbreak of human leishmaniosis was confirmed in the southwest of the province of Madrid, Spain, between July 2009 and December 2012. Incidence of Leishmania infection in dogs was unchanged in this period, prompting a search for alternative sylvatic infection reservoirs. We evaluated exposure to Leishmania in serum samples from animals in the area with an indirect immunofluorescence test (IFAT). Using promastigotes from six culture passages and a 1/25 threshold titer, we found anti-Leishmania infantum seroreactivity in 9.3% of cats (4 of 43), 45.7% of rabbits (16/35) and 74.1% of hares (63/85). Use of promastigotes from >10 in vitro passages resulted in a notably IFAT lower titer, suggesting antigenic changes during extended culture. Postmortem inspection of seropositive animals showed no clinical signs of infection. The results clearly suggest that asymptomatic hares were the main reservoir in the outbreak, and corroborate IFAT as a sensitive serological surveillance method to detect such cryptic Leishmania infections. 相似文献
35.
Luis A. Saavedra-Jiménez Rodolfo Ramírez-Valverde Rafael Núñez-Domínguez José G. García-Muñiz Nicolas Lopez-Villalobos Agustín Ruíz-Flores 《Tropical animal health and production》2013,45(7):1489-1494
The objective of this study was to determine the magnitude of genotype by climate interaction (GCI) in the national genetic evaluation for weaning (WW) and yearling (YW) weights of Mexican Braunvieh cattle. The numbers of performance records and animals in the pedigree were 12,364 and 25,173 for WW, and 7,991 and 18,072 for YW, respectively. Performance records were clustered based on climatological variables into: dry tropic (DT), wet tropic (WT), and temperate (TE) climates. Animal models were used to estimate genetic parameters and predict breeding values in each of the climates. Bivariate analyses were carried out for pairwise combinations of climates on each trait, considering the same trait in different climates as a different trait. Criteria to evaluate GCI were genetic correlations (r g), correlations between predicted breeding values (r BV), and frequencies of coincidence (FC) in the ranking of the top 25 sires. Results of comparisons between pairs of climates were variable, depending on specific cases. For WW, the r g, r BV, and FC ranged from ?0.36 to 0.84, ?0.60 to 0.97, and 0.16 to 0.92, respectively; whereas for YW, they fluctuated between 0.23 and 0.99, 0.33 and 1.00, and 0.60 and 1.00, respectively. For both traits, the results suggest absence of GCI between DT and TE; however, GCI was detected in the other pairs of climates, where WT was involved. To maximize genetic progress, the joint genetic evaluation should be performed only for animals with performance data in DT and TE, whereas a separated evaluation is suggested for animals with performance records generated under WT conditions. 相似文献
36.
I. García-Ispierto F. López-Gatius S. Almería J. Yániz P. Santolaria B. Serrano G. Bech-Sàbat C. Nogareda J. Sulon N.M. de Sousa J.F. Beckers 《Domestic animal endocrinology》2009
The aim of the present study was to investigate possible relationships between plasma concentrations of prolactin and the following factors throughout gestation in lactating dairy cows: photoperiod, season, milk production, Neospora caninum-seropositivity, twin pregnancy, and plasma concentrations of pregnancy associated glycoproteins-1 (PAG-1), progesterone and cortisol. Pregnancy was diagnosed by trans-rectal ultrasonography on Day 40 post-insemination and by palpation per rectum on Days 90, 120, 150, 180 and 210 or until abortion in aborting cows. Blood samples were collected from each animal immediately before each pregnancy diagnosis. The study population was comprised of 73 non-aborting (54 Neospora-seropositive cows) and 20 aborting cows (all Neospora-seropositive) cows. In non-aborting cows, GLM repeated measures of analysis of variance revealed that lactation number and days in milk had no effect on plasma prolactin concentrations throughout gestation, whereas high plasma prolactin concentrations were significantly associated with high plasma levels of cortisol and PAG-1, with Neospora-seropositivity, positive photoperiod (increasing day length), twin pregnancy, and with low plasma progesterone concentrations. An interaction among plasma prolactin, plasma cortisol and milk production was observed in that plasma prolactin concentrations differed significantly throughout gestation and were highest in high-producing cows with high cortisol levels. In Neospora-seropositive non-aborting versus aborting cows, mean prolactin concentrations failed to differ on Days 40, 90, 120, 150 and 180 of pregnancy, whereas prolactin values were significantly lower (P = 0.03) in aborting animals on Day 210 of pregnancy. Our results indicate that a positive photoperiod and Neospora-infection lead to increased plasma prolactin concentrations throughout gestation. Reduced prolactin concentrations detected in Neospora-seropositive aborting cows compared to non-aborting animals suggests a protective effect of prolactin in N. caninum infection. 相似文献
37.
C. Eckstein F. Guscetti M. Roos J. Martín de las Mulas B. Kaser‐Hotz C. Rohrer Bley 《Veterinary and comparative oncology》2009,7(1):54-68
We retrospectively evaluated predictive prognostic factors in 73 cats with vaccine‐associated sarcoma given postsurgical curative (n = 46, most with clean margins) or coarse fractionated radiotherapy (n = 27, most with either macroscopic disease or dirty margins). The former animals displayed a median survival of 43 months and a median progression free interval (PFI) of 37 months, the latter reached a median survival of 24 months and a median PFI of 10 months. In cats undergoing coarse fractionated therapy, factors predictive of a better outcome included lack of visible mass (n = 10) as opposed to macroscopic disease (n = 17, survival: 30 versus 7 months, P = 0.025; PFI: 20 versus 4 months, P = 0.01), adjuvant chemotherapy for gross disease (n = 5/17, survival: 29 versus 5 months, P = 0.04) and a smaller number of surgeries preceding radiation therapy (coeff = 0.41, P = 0.03). The Ki67 index was not predictive for survival. We concluded that postsurgical curative and coarse fractionated radiotherapy are effective legitimate options for managing vaccine‐associated sarcomas. 相似文献
38.
39.
Rosina Soler Pablo Luis Peri Héctor Bahamonde Verónica Gargaglione Sebastián Ormaechea Alejandro Huertas Herrera Laura Sánchez Jardón Cristian Lorenzo Guillermo Martínez Pastur 《Strength and Conditioning Journal》2018,71(5):637-645
In recent decades agroforestry has undergone significant development in Latin America. South America generates the most scientific research on the topic in the region. We conducted a comprehensive review and analysis of knowledge production for South American agroforestry that includes livestock grazing, known as agrosilvopastoralism (AS), examining how different sociopolitical factors such as sources of funding, institutional priorities, and international cooperation can bias the direction and objectives of scientific research. We assessed the major attributes of scientific publications on the topic (25 articles per country; overall n = 210) and the potential factors underlying the processes of research and development in the region. The tree component was the most studied, while the livestock component received less attention. Studies were mainly focused on the production of goods and services (monetary or nonmonetary approaches), except in Brazil, where conservation was the major study objective. Stakeholders were involved in more than half of the studies (60%), and they were mostly ranchers and local producers. More than half (70%) of the studies offered recommendations based on their results, and such recommendations were mostly concerned with the management of agrosilvopastoral system components. In general, studies were led just as often by local as foreign first authors and coauthored by more than three people as part of interinstitutional working groups. Brazil, Argentina, Colombia, and Chile had more frequent cooperation among institutions and countries but mainly used their own funding. In contrast, Bolivia, Ecuador, and Peru had almost 100% of their studies supported by foreign countries (North America and Europe). Countries with greater internal funding of research generated more long-term studies. Besides this, two clear trends were detected: 1) conservation and social aspects were mainly supported by sources from external countries led by foreign principal investigators, and 2) production issues were supported from sources within countries and supported high levels of cooperation among institutions. 相似文献
40.
Silvia Kohutova Michaela Paninarova Miša Škorič Vladimir Jekl Zdenek Knotek Karel Hauptman 《Journal of Exotic Pet Medicine》2018,27(1):41-45
A 3-year-old, 920 g intact female guinea pig presented with a 4-month history of nonpruritic hair loss on the ventral abdomen. The physical examination revealed flank and ventral abdominal alopecia, mucoid vulvar discharge, and abdominal distension. Bilateral rounded masses just caudal to the kidneys and structures consistent with enlarged uterine horns were detected on abdominal palpation. Abdominal ultrasound revealed bilateral ovarian cysts, thickened uterine horns, and multiple circular hypoechoic and anechoic structures in the uterine wall. The patient underwent ovariohysterectomy. Gross examination of the uterus revealed a piece of hay in the left uterine horn. A final diagnosis was hormonally active ovarian follicular cysts, cystic endometrial hyperplasia, and purulent bacterial endometritis caused by Escherichia coli, Fusobacterium nucleatum, and Arthrobacter spp. Cystic endometrial hyperplasia is infrequently reported in guinea pigs, and this report describes an associated bacterial endometritis and uterine foreign body with concurrent ovarian cysts. 相似文献