全文获取类型
收费全文 | 8852篇 |
免费 | 554篇 |
国内免费 | 50篇 |
专业分类
林业 | 550篇 |
农学 | 438篇 |
基础科学 | 78篇 |
1589篇 | |
综合类 | 639篇 |
农作物 | 461篇 |
水产渔业 | 650篇 |
畜牧兽医 | 4113篇 |
园艺 | 126篇 |
植物保护 | 812篇 |
出版年
2023年 | 81篇 |
2022年 | 148篇 |
2021年 | 265篇 |
2020年 | 264篇 |
2019年 | 325篇 |
2018年 | 292篇 |
2017年 | 310篇 |
2016年 | 322篇 |
2015年 | 233篇 |
2014年 | 317篇 |
2013年 | 498篇 |
2012年 | 503篇 |
2011年 | 555篇 |
2010年 | 278篇 |
2009年 | 314篇 |
2008年 | 458篇 |
2007年 | 440篇 |
2006年 | 394篇 |
2005年 | 371篇 |
2004年 | 345篇 |
2003年 | 306篇 |
2002年 | 348篇 |
2001年 | 240篇 |
2000年 | 242篇 |
1999年 | 204篇 |
1998年 | 59篇 |
1997年 | 58篇 |
1996年 | 55篇 |
1995年 | 51篇 |
1994年 | 38篇 |
1993年 | 38篇 |
1992年 | 80篇 |
1991年 | 53篇 |
1990年 | 61篇 |
1989年 | 66篇 |
1988年 | 62篇 |
1987年 | 51篇 |
1986年 | 46篇 |
1985年 | 58篇 |
1984年 | 38篇 |
1983年 | 43篇 |
1982年 | 30篇 |
1980年 | 24篇 |
1979年 | 37篇 |
1978年 | 22篇 |
1977年 | 21篇 |
1974年 | 23篇 |
1973年 | 25篇 |
1972年 | 24篇 |
1970年 | 26篇 |
排序方式: 共有9456条查询结果,搜索用时 15 毫秒
171.
Waardplanten van het aardappel-YN-virus 总被引:1,自引:0,他引:1
172.
173.
174.
Reche MP Jiménez PA Alvarez F García de los Rios JE Rojas AM de Pedro P 《Journal of veterinary medicine. B, Infectious diseases and veterinary public health》2003,50(1):42-44
A total of 595 faecal samples from raptorial birds, either captive or free-living, residing in GREFA Wildlife Hospital were bacteriologically examined using various selective media and an Automated Diagnostic Assay System for Salmonella detection. Serotype and phage type of the strains identified as Salmonella was determined. In the captive group, of the 285 samples examined, 21 (7.36%) were positive for Salmonella. Serotyping revealed that most of the individuals were infected by Salmonella serotype Havana. This result suggested that there could be a source of contamination in the Hospital although it could not be established. In the wild free-living group, over 310 samples examined (4.19%) were positive for Salmonella. The Salmonella isolates showed a major variety of serotypes: Enteritidis, Adelaide, Brandenburg, Newport, Typhimurium, Hadar, Saintpaul and Virchow. Most of them are similar to those commonly described in isolates from human and domestic animals. These results indicate that wild birds could be involved in the dissemination of Salmonella in humans or domestic animals or vice versa. 相似文献
175.
甘肃省泾川县三元杂交肉牛生长发育的研究报告 总被引:1,自引:1,他引:0
本研究测定并对比研究了德秦黄、德利黄、德西黄、利西黄、利秦黄等三元杂交牛及二元杂交牛初生 ,3月龄、6月龄、1 2月龄、1 8月龄的生长发育指标 ,结果表明 :三元杂交牛比二次杂交牛体尺、体重均有较大幅度的增长、初步筛选出适宜泾川养殖习惯的较佳杂交组合。在农户饲养条件下 ,三元杂交初生重 38kg,比二元杂交牛提高 1 2 .8%~ 5 6.6% ;1 8月龄母牛体重 377.8kg,提高 1 5 .2 %~94.1 % ;1日龄~ 1 8月龄日增重 5 2 8.2 g,增长 9.2 %~ 68.7% ;管围提高幅度为 2 4 .1 %~ 32 .3% ;臀围为 1 .7%~ 32 .3% ;体高为 2 .9%~ 1 5 3% ,体斜长为 5 .5 %~ 1 3.9% ,胸围为 1 1 .4%~ 2 0 .5 %。尻长为 5 .1 %~ 1 1 .8% ,腰角宽为 0~ 2 1 .4% ,髋宽为 0~ 3%。适宜的杂交组合为德秦黄、德利黄、德西黄。三元杂交牛 6~ 1 2月龄生长发育受阻 ,主要是饲料营养水平低所致 ,建议从 2月龄开始用优质饲草和配和配合饲料 ,1 8月龄体重达到 40 0 kg以上 ,再经 3个月育肥 ,2 1月龄达到体重 5 0 0 kg的出栏标准。 相似文献
176.
de Laforcade AM Freeman LM Shaw SP Brooks MB Rozanski EA Rush JE 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2003,17(5):674-679
Sepsis is a frequent source of morbidity and mortality in critically ill patients. The goal of this case control study was to measure hemostatic changes in dogs with naturally occurring sepsis. Blood was collected within 24 hours of admission from 20 dogs that fulfilled the criteria for sepsis. Sepsis was defined as histologic or microbiological confirmation of infection and 2 or more of the following criteria: hypo- or hyperthermia, tachycardia, tachypnea, or leukopenia, leukocytosis, or > 3% bands. Culture and sensitivities were performed on appropriate samples from all septic dogs. Twenty-eight control dogs were enrolled on the basis of normal results of physical examination, CBC, serum biochemistry, and coagulation profile. Plasma samples were analyzed for prothrombin time (PT), partial thromboplastin time (PTT), fibrin(ogen) degradation products (FDP), D-dimer (DD) concentrations, antithrombin (AT) activity, and protein C (PC) activity. Data were compared between groups by chi-square or independent t-tests. PC (P < .001) and AT (P < .001) activities were significantly lower in dogs with sepsis compared to controls. Dogs with sepsis had significantly higher PT (P = .007), PTT (P = .005), D-dimer (P = .005), and FDP (P = .001) compared to controls. Platelet counts were not significantly different between groups. Ten of the 20 septic dogs (50%) died, but no association was identified between any of the measured variables and outcome. These findings are consistent with previous studies in animals with experimentally induced disease and in clinical studies of humans. On the basis of these results, further investigation of the role of AT and PC in canine sepsis is warranted. 相似文献
177.
de Laforcade AM Freeman LM Rush JE 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2003,17(3):315-318
The purpose of this study was to determine whether nitric oxide (NO) concentrations are high in dogs with chronic valvular disease (CVD) and dilated cardiomyopathy (DCM) compared to healthy controls and to determine whether NO concentrations are correlated with type of cardiac disease, disease severity, medical therapy, or serum tumor necrosis factor (TNF) and interleukin-1 (IL-1). Blood was collected from 32 dogs with DCM, from 10 dogs with CVD, and from 10 healthy controls. Indirect determination of NO concentrations was performed by a commercial photoabsorbance assay that uses a Greiss reagent to measure the concentration of nitrite and nitrate (NN), end products of NO metabolism. TNF and IL-1 activities were measured by bioassay. Mean NN concentrations were significantly higher in dogs with heart disease (median, 4.57 microM; range, 0.00-31.05 microM) than in controls (median, 0.00 microM; range, 0.00-6.16 microM; P = .04). NN concentrations in dogs with cardiac disease were not correlated with type or severity of cardiac disease, medication type, or TNF and IL-1 concentrations. NN concentrations were inversely correlated with fractional shortening. The results of this study suggest that metabolites of NO are increased in some dogs with cardiac disease, but these increases appear to be independent of disease severity, TNF and IL-1 concentrations, and type of pharmacologic intervention. 相似文献
178.
The combined occurrence of ocular pigment deposition and glaucoma has been described in Cairn Terriers. Recently, this condition was also observed in two other breeds: the Boxer (two cases) and the Labrador Retriever (one case). Six dogs were referred to the Ophthalmology section of the Department of Clinical Sciences of Companion Animals and to a private referral clinic because of glaucoma or blindness in one or both eyes. In five cases ophthalmic examination showed pigment depositions in the sclera around the entire circumference of the perilimbal zone. Eight enucleated eyes (four eyes of two Cairn Terriers, three eyes of two Boxers and one eye of a Labrador Retriever) were examined microscopically. All eyes showed the same findings: an extensive infiltration of large melanin-containing cells with an eccentric nucleus, located in the iris, ciliary body, retina, choroids and sclera. Transmission electron microscopy of two of the examined eyes revealed that the morphology of most of these cells was consistent with melanophages. While reports in the veterinary literature concerning this condition are limited the cells concerned have been described to be melanocytes. Further research is needed to conclusively identify the cell type. As described in the present report, the histologic and transmission electron microscopic findings suggest a different etiology of the ocular pigment deposition and glaucoma compared with the pigment dispersal syndrome in humans. 相似文献
179.
Daminet S Croubels S Duchateau L Debunne A van Geffen C Hoybergs Y van Bree H de Rick A 《Veterinary journal (London, England : 1997)》2003,166(3):224-232
Many factors including drugs can influence thyroid function in humans, rats and dogs. Studies in humans report significant effects of non-steroidal anti-inflammatory agents (NSAIDs) on thyroid function tests, which can lead to misinterpretation of the results and inappropriate therapeutic decisions. As NSAIDs are used more and more frequently in dogs, it is important to know to what extent they can influence results. Eighteen spayed female beagle dogs were randomly assigned to three treatment sequences in a 3 x 3 crossover study design with treatments consisting of acetylsalicylic acid (ASA) (25 mg/kg BW q 12 h), ketoprofen (Keto) (1 mg/kg BW q 24 h) or placebo administered for a 1-week period with a 3-week washout period between treatment periods. Blood samples for determination of total thyroxine (TT4), free thyroxine (FT4), total triiodothyronine (TT3), thyrotropin (TSH), reverse triiodothyronine (rT3), Keto and ASA concentrations were taken during each treatment period on days 0, 1, 3 and 7. During the washout period samples were taken weekly. A significant decrease in TT4 was observed as soon as 24 h after ASA administration, whereas the decrease in TT3 was less pronounced and differed significantly from the placebo only after 1 week of administration. No significant effects were found for free T4 and TSH with ASA administration. No significant effects on thyroid results were found following Keto administration. The results indicate that TT4 can be markedly decreased by ASA therapy and until the results of further studies are available, thyroid function test results should be interpreted cautiously in dogs on NSAIDs therapy. 相似文献
180.
de Chambrier A 《Folia parasitologica》2003,50(2):121-127
Type material of the proteocephalidean cestodes Manaosia bracodemoca Woodland, 1935 and Paramonticellia itaipuensis Pavanelli et Rego, 1991 (both monotypic genera) as well as recently collected material of the latter species are redescribed. A close similarity between both species was observed: the shape of scoleces is identical, both possess a globular scolex with hidden suckers, a well-developed circular, horseshoe-shaped musculature surrounding suckers; the measurements of both taxa are also similar (scolex, suckers, young proglottides). Both cestodes possess a medullary ovary crossing the dorsal muscle layer and ending in the dorsal cortex, the testes are in the dorsal cortex and the cortical vitellarium is laterally situated. Both species parasitize the same fish host. Therefore Paramonticellia is considered a junior synonym of Manaosia and Paramonticellia itaipuensis becomes a junior synonym of Manaosia bracodemoca. An emended diagnosis of Manaosia, which is a monotypic genus, is provided. 相似文献