全文获取类型
收费全文 | 22536篇 |
免费 | 398篇 |
国内免费 | 210篇 |
专业分类
林业 | 3955篇 |
农学 | 1711篇 |
基础科学 | 205篇 |
3849篇 | |
综合类 | 1593篇 |
农作物 | 2482篇 |
水产渔业 | 2265篇 |
畜牧兽医 | 3438篇 |
园艺 | 1242篇 |
植物保护 | 2404篇 |
出版年
2023年 | 42篇 |
2022年 | 57篇 |
2021年 | 121篇 |
2020年 | 111篇 |
2019年 | 123篇 |
2018年 | 2867篇 |
2017年 | 2838篇 |
2016年 | 1362篇 |
2015年 | 215篇 |
2014年 | 212篇 |
2013年 | 299篇 |
2012年 | 1102篇 |
2011年 | 2460篇 |
2010年 | 2364篇 |
2009年 | 1489篇 |
2008年 | 1648篇 |
2007年 | 1918篇 |
2006年 | 330篇 |
2005年 | 375篇 |
2004年 | 343篇 |
2003年 | 445篇 |
2002年 | 424篇 |
2001年 | 346篇 |
2000年 | 238篇 |
1999年 | 155篇 |
1998年 | 49篇 |
1997年 | 47篇 |
1996年 | 38篇 |
1995年 | 50篇 |
1994年 | 46篇 |
1993年 | 57篇 |
1992年 | 55篇 |
1991年 | 42篇 |
1990年 | 60篇 |
1989年 | 56篇 |
1988年 | 48篇 |
1987年 | 41篇 |
1986年 | 33篇 |
1985年 | 38篇 |
1984年 | 54篇 |
1983年 | 30篇 |
1982年 | 28篇 |
1980年 | 24篇 |
1979年 | 29篇 |
1978年 | 29篇 |
1977年 | 34篇 |
1975年 | 27篇 |
1974年 | 37篇 |
1972年 | 31篇 |
1971年 | 41篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
221.
222.
X. Mao N.K. Kadri J.R. Thomasen D.J. De Koning G. Sahana B. Guldbrandtsen 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2016,133(3):207-218
Decreased calving performance not only directly impacts the economic efficiency of dairy cattle farming but also influences public concern for animal welfare. Previous studies have revealed a QTL on Bos taurus autosome (BTA) 18 that has a large effect on calving traits in Holstein cattle. In this study, fine mapping of this QTL was performed using imputed high‐density SNP chip (HD) genotypes followed by imputed next‐generation sequencing (NGS) variants. BTA18 was scanned for seven direct calving traits in 6113 bulls with imputed HD genotypes. SNP rs136283363 (BTA18: 57 548 213) was consistently the most significantly associated SNP across all seven traits [e.g. p‐value = 2.04 × 10?59 for birth index (BI)]. To finely map the QTL region and to explore pleiotropic effects, we studied NGS variants within the targeted region (BTA18: 57 321 450–57 625 355) for associations with direct calving traits and with three conformation traits. Significant variants were prioritized, and their biological relevance to the traits was interpreted. Considering their functional relationships with direct calving traits, SIGLEC12, CD33 and CEACAM18 were proposed as candidate genes. In addition, pleiotropic effects of this QTL region on direct calving traits and conformation traits were observed. However, the extent of linkage disequilibrium combined with the lack of complete annotation and potential errors in the Bos taurus genome assembly hampered our efforts to pinpoint the causal mutation. 相似文献
223.
De Marco MA Campitelli L Foni E Raffini E Barigazzi G Delogu M Guberti V Di Trani L Tollis M Donatelli I 《Veterinary microbiology》2004,98(3-4):197-208
We report the results of a 6-year serological and virological monitoring performed in ducks and coots in Italy, in order to assess the degree of influenza A virus circulation in these birds during wintering. A total of 1039 sera collected from 1992 to 1998 was screened by a double antibody sandwich blocking ELISA (NP-ELISA): seroprevalence of antibodies to influenza A viruses was significantly higher in ducks compared to coots (52.2% vs. 7.1%, respectively). The hemagglutination-inhibition (HI) assay, performed on NP-ELISA positive sera, showed that 16.9% of these duck sera and 33.3% of these coot sera had antibodies to at least one influenza virus HA subtype: ducks showed HI antibodies against most of the HA subtypes, except for the H3, H4, H7, and H12; coots were seropositive to the H3 and H10 subtypes, only. From 1993 to 1998, 22 virus strains were obtained from 802 cloacal swabs, with an overall virus isolation frequency of 2.7%. Viruses belonging to the H1N1 subtype were by far the most commonly circulating strains (18/22) and were isolated mainly from ducks (17/18). The remaining viruses were representative of the H10N8, H5N2 and H3N8 subtypes. Our data indicate some differences between influenza A virus circulation in sympatric ducks and coots and a significant antigenic diversity between some reference strains and viruses recently isolated in Italy. 相似文献
224.
Histomoniasis or blackhead is a disease of gallinaceous birds, caused by the protozoon Histomonas meleagridis. Since traditional diagnostics for the detection of this disease are complex and far less sensitive than molecular tools, a PCR would provide a more rapid and sensitive alternative. However, intestinal material and droppings, which are preferably used in epidemiological studies of histomoniasis, often contain PCR inhibitory substances. To detect these false negative results, the use of an internal amplification control is essential. Nevertheless, the recently developed PCR tests lack this internal control. Therefore, a new PCR assay with H. meleagridis specific primers was developed which does include an internal amplification control. The diagnostic value of the PCR assay was evaluated in comparison to three other conventional H. meleagridis specific PCR tests (HIS5, HM1 and HM2). None of the organ samples originating from uninfected turkeys, showed positive PCR results in any of the tests. Among the lesion-positive, inhibition-free samples, 95.4% were positive by our PCR assay, while only 50, 66.7 and 83.3% of the lesion-positive organs tested positive by the HM1, the HIS5 and the HM2 PCR respectively. In conclusion, our PCR offers the use of the internal control to detect false negative results and an increased sensitivity, and thus should be useful for routine diagnosis of H. meleagridis in poultry. 相似文献
225.
De Martino L Marfe G Consalvo MI Di Stefano C Pagnini U Sinibaldi-Salimei P 《Veterinary microbiology》2007,123(1-3):210-216
Viruses have evolved different strategies to interfere with apoptotic pathways in order to halt cellular responses to infection. One previous study showed that transient transfection of bovine herpesvirus type-1 (BHV-1) UL14 protein is efficient in protecting Madin Darby kidney (MDBK) and human chronic myelogenous leukemia (K562) cells from sorbitol-induced apoptosis. This protein corresponds to a putative protein of BHV-1, which shares aminoacid sequence with a part of the peptide-binding domain conserved in human heat shock protein (HSP70) family. The pBK-CMV-UL14 plasmid transfected MDBK cells treated with sorbitol did not show caspase-3 and caspase-9 activation with respect to non-transfected MDBK cells (UL14 negative). Furthermore, we report that the expression of the full length sequence of BHV-1 UL14 is evident after 7 h of infection of BHV-1 on MDBK cells which were then treated with sorbitol. These results indicate that UL14 gene product has important implications to enhance cell survival in response to apoptotic stimuli. 相似文献
226.
227.
Booker CW Abutarbush SM Schunicht OC Jim GK Perrett T Wildman BK Guichon PT Pittman TJ Jones C Pollock CM 《Veterinary therapeutics : research in applied veterinary medicine》2007,8(3):183-200
The purpose of this study was to determine the efficacy and cost-effectiveness of tulathromycin (DRAX) versus tilmicosin (MIC) or oxytetracycline (TET) as a metaphylactic antimicrobial in feedlot calves. Calves that received DRAX had significantly (P<.05) lower initial undifferentiated fever (UF) treatment and relapse rates; lower overall chronicity, overall mortality, and cause-specific mortality rates; higher average daily gains; and improved quality grades. However, calves that received DRAX also had poorer (P<.05) yield grades compared with calves that received MIC or TET and worse feed conversion compared with calves that received MIC. Net advantages in the DRAX group were 3.79CanDollars/animal and 16.96CanDollars/animal compared with the MIC and TET groups, respectively. Based on these results, DRAX is a more efficacious and cost-effective metaphylactic antimicrobial than MIC or TET in feedlot calves at ultra-high risk of developing UF. In addition, this study presents a comparison between two methods ("deads out" and "deads in") of calculating feedlot performance variables. 相似文献
228.
Troan BV Perelygina L Patrusheva I Wettere AJ Hilliard JK Loomis MR Voe RS 《Journal of the American Veterinary Medical Association》2007,231(12):1878-1883
CASE DESCRIPTION: A 6.5-year-old female eastern black and white colobus monkey (Colobus guereza) was evaluated after acute onset of ataxia and inappetence. CLINICAL FINDINGS: The monkey was ataxic and lethargic, but no other abnormalities were detected via physical examination, radiography, or clinicopathologic analyses. During the next 2 days, the monkey's clinical condition deteriorated, and its WBC count decreased dramatically. Cytologic examination of a CSF sample revealed marked lymphohistiocytic inflammation. TREATMENT AND OUTCOME: Despite supportive care, the monkey became apneic; after 20 hours of mechanical ventilation, fatal cardiac arrest occurred. At necropsy, numerous petechiae were detected within the white matter tracts of the brain; microscopic lesions of multifocal necrosis and hemorrhage with intranuclear inclusions identified in the brain and adrenal glands were consistent with an acute herpesvirus infection. A specific diagnosis of herpesvirus papio-2 (HVP-2) infection was made on the basis of results of serologic testing; PCR assay of tissue specimens; live virus isolation from the lungs; and immunohistochemical identification of the virus within brain, spinal cord, and adrenal gland lesions. Via phylogenetic tree analysis, the colobus HVP-2 isolate was grouped with neuroinvasive strains of the virus. The virus was most likely transmitted to the colobus monkey through toys shared with a nearby colony of baboons (the natural host of HVP-2). CLINICAL RELEVANCE: To the authors' knowledge, this is the first reported case of natural transmission of HVP-2 to a nonhost species. Infection with HVP-2 should be a differential diagnosis for acute encephalopathy in primate monkeys and humans, particularly following exposure to baboons. 相似文献
229.
M. P. Reche P. A. Jimnez F. Alvarez J. E. García de los Ríos A. M. Rojas P. De Pedro 《Zoonoses and 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
230.
Shafarin MS Zamri-Saad M Khairani BS Saharee AA 《Tropical animal health and production》2008,40(5):335-340
This report describes the proliferation and transmission patterns of Pasteurella multocida B:2 among stressful goats, created through dexamethasone injections. Thirty seven clinically healthy adult goats were divided
into three groups consisted of 15 goats in group A, 11 goats in group B and the remaining 11 in group C. At the start of the
study, all goats of group A were exposed intranasally to 1.97 × 1010 CFU/ml of live P. multocida B:2. Dexamethasone was immediately administered intramuscularly for 3 consecutive days at a dosage rate of 1 mg/kg. The exposed
goats were observed for signs of HS for a period of 1 month. At the end of the 1-month period, 11 goats from group B were
introduced into and commingled with the surviving goats of group A before all goats from both groups were immediately injected
intramuscularly with dexamethasone for 3 consecutive days. The treatment with dexamethasone was then carried out at monthly
interval throughout the 3-month study period. Goats of group C were kept separately as negative control. Three surviving goats
from each group were killed at 2-week interval for a complete post-mortem examination. Two (13%) goats of group A were killed
within 24 hours after intranasal exposure to P. multocida B:2 while another two (13%) goats from the same group were killed on day 40, approximately 10 days after the second dexamethasone
injection. All four goats showed signs and lesions typical of haemorrhagic septicaemia. Bacteraemia was detected in 3 goats
of group A that were having rectal temperature higher than 41°C. The P. multocida B:2 isolation pattern was closely associated with dexamethasone injections when significantly (p < 0.05) higher rate of isolations
from both groups were observed after each dexamethasone injection. Transmission of P. multocida B:2 from goats of group A to group B was successful when P. multocida B:2 was isolated from goats of group B for a period of 28 days. There was a strong correlation between dexamethasone injections,
rate of bacterial isolation and serum cortisol level. The IgG level showed an increasing trend 2 weeks after exposure to P. multocida B:2 and remained high throughout the study period. 相似文献