全文获取类型
收费全文 | 5519篇 |
免费 | 248篇 |
国内免费 | 4篇 |
专业分类
林业 | 423篇 |
农学 | 183篇 |
基础科学 | 35篇 |
1101篇 | |
综合类 | 877篇 |
农作物 | 231篇 |
水产渔业 | 344篇 |
畜牧兽医 | 2002篇 |
园艺 | 176篇 |
植物保护 | 399篇 |
出版年
2023年 | 33篇 |
2022年 | 54篇 |
2021年 | 84篇 |
2020年 | 135篇 |
2019年 | 126篇 |
2018年 | 135篇 |
2017年 | 121篇 |
2016年 | 130篇 |
2015年 | 110篇 |
2014年 | 131篇 |
2013年 | 259篇 |
2012年 | 303篇 |
2011年 | 382篇 |
2010年 | 220篇 |
2009年 | 168篇 |
2008年 | 310篇 |
2007年 | 317篇 |
2006年 | 291篇 |
2005年 | 289篇 |
2004年 | 264篇 |
2003年 | 271篇 |
2002年 | 256篇 |
2001年 | 64篇 |
2000年 | 71篇 |
1999年 | 82篇 |
1998年 | 56篇 |
1997年 | 53篇 |
1996年 | 54篇 |
1995年 | 39篇 |
1994年 | 47篇 |
1993年 | 49篇 |
1992年 | 39篇 |
1991年 | 46篇 |
1990年 | 46篇 |
1989年 | 42篇 |
1988年 | 38篇 |
1987年 | 39篇 |
1986年 | 54篇 |
1985年 | 32篇 |
1984年 | 43篇 |
1983年 | 35篇 |
1982年 | 36篇 |
1981年 | 27篇 |
1980年 | 20篇 |
1979年 | 23篇 |
1978年 | 27篇 |
1977年 | 26篇 |
1975年 | 20篇 |
1973年 | 24篇 |
1972年 | 20篇 |
排序方式: 共有5771条查询结果,搜索用时 0 毫秒
41.
42.
43.
Carrie A. Davis Reza Seddighi Sherry K. Cox Xiaocun Sun Christine M. Egger Thomas J. Doherty 《Veterinary anaesthesia and analgesia》2017,44(4):727-737
Objective
To determine the effect of fentanyl on the induction dose of propofol and minimum infusion rate required to prevent movement in response to noxious stimulation (MIRNM) in dogs.Study design
Crossover experimental design.Animals
Six healthy, adult intact male Beagle dogs, mean ± standard deviation 12.6 ± 0.4 kg.Methods
Dogs were administered 0.9% saline (treatment P), fentanyl (5 μg kg?1) (treatment PLDF) or fentanyl (10 μg kg?1) (treatment PHDF) intravenously over 5 minutes. Five minutes later, anesthesia was induced with propofol (2 mg kg?1, followed by 1 mg kg?1 every 15 seconds to achieve intubation) and maintained for 90 minutes by constant rate infusions (CRIs) of propofol alone or with fentanyl: P, propofol (0.5 mg kg?1 minute?1); PLDF, propofol (0.35 mg kg?1 minute?1) and fentanyl (0.1 μg kg?1 minute?1); PHDF, propofol (0.3 mg kg?1 minute?1) and fentanyl (0.2 μg kg?1 minute?1). Propofol CRI was increased or decreased based on the response to stimulation (50 V, 50 Hz, 10 mA), with 20 minutes between adjustments. Data were analyzed using a mixed-model anova and presented as mean ± standard error.Results
ropofol induction doses were 6.16 ± 0.31, 3.67 ± 0.21 and 3.33 ± 0.42 mg kg?1 for P, PLDF and PHDF, respectively. Doses for PLDF and PHDF were significantly decreased from P (p < 0.05) but not different between treatments. Propofol MIRNM was 0.60 ± 0.04, 0.29 ± 0.02 and 0.22 ± 0.02 mg kg?1 minute?1 for P, PLDF and PHDF, respectively. MIRNM in PLDF and PHDF was significantly decreased from P. MIRNM in PLDF and PHDF were not different, but their respective percent decreases of 51 ± 3 and 63 ± 2% differed (p = 0.035).Conclusions and clinical relevance
Fentanyl, at the doses studied, caused statistically significant and clinically important decreases in the propofol induction dose and MIRNM. 相似文献44.
Jessica D Lightsey Sentiel A Rommel Alexander M Costidis Thomas D Pitchford 《Journal of zoo and wildlife medicine》2006,37(3):262-275
Between 1993 and 2003, 713 (24%) of 2,940 dead Florida manatees (Trichechus manatus latirostris) recovered from Florida waters and examined were killed by watercraft-induced trauma. It was determined that this mortality was the result of watercraft trauma because the external wound patterns and the internal lesions seen during gross necropsy are recognizable and diagnostic. This study documents the methods used in determining watercraft-related mortality during gross necropsy and explains why these findings are diagnostic. Watercraft can inflict sharp- and blunt-force trauma to manatees, and both types of trauma can lead to mortality. This mortality may be a direct result of the sharp and blunt forces or from the chronic effects resulting from either force. In cases in which death is caused by a chronic wound-related complication, the original incident is usually considered to be the cause of death. Once a cause of death is determined, it is recorded in an extensive database and is used by Federal and state managers in developing strategies for the conservation of the manatee. Common sequelae to watercraft-induced trauma include skin lesions, torn muscles, fractured and luxated bones, lacerated internal organs, hemothorax, pneumothorax, pyothorax, hydrothorax, abdominal hemorrhage and ascites, and pyoperitoneum. 相似文献
45.
46.
Jack PJ Amos-Ritchie RN Reverter A Palacios G Quan PL Jabado O Briese T Lipkin WI Boyle DB 《Veterinary microbiology》2009,133(1-2):145-153
Definitive diagnosis of vesicular or vesicular-like lesions in livestock animals presents challenges both for veterinary clinicians and diagnostic laboratories. It is often impossible to diagnose the causative disease agent on a clinical basis alone and difficult to collect ample vesicular epithelium samples. Due to restrictions of time and sample size, once laboratory tests have ruled out foot-and-mouth disease, vesicular stomatitis and swine vesicular disease a definitive diagnosis may remain elusive. With the ability to test a small quantity of sample for a large number of pathogens simultaneously, DNA microarrays represent a potential solution to this problem. This study describes the application of a long oligonucleotide microarray assay to the identification of viruses known to cause vesicular or vesicular-like lesions in livestock animals. Eighteen virus isolates from cell culture were successfully identified to genus level, including representatives of each foot-and-mouth disease virus serotype, two species of vesicular stomatitis virus (VSV), swine vesicular disease virus, vesicular exanthema of swine virus (VESV), bovine herpesvirus 1, orf virus, pseudocowpox virus, bluetongue virus serotype 1 and bovine viral diarrhoea virus 1. VSV and VESV were also identified in vesicular epithelium samples, with varying levels of sensitivity. The results indicate that with further development this microarray assay could be a valuable tool for the diagnosis of vesicular and vesicular-like diseases. 相似文献
47.
48.
Baker DL Finco-Kent DL Reagan WJ Conklyn MJ Kawabata TT 《Veterinary clinical pathology / American Society for Veterinary Clinical Pathology》2008,37(1):42-48
BACKGROUND: Guidelines published by the Food and Drug Administration and Center for Human Medicinal Products describe the need to assess immunotoxic effects in nonclinical studies that evaluate drug toxicity, including the use of immunophenotyping to measure immunotoxicity. We are not aware of previous studies, however, that have validated methods for immunophenotyping peripheral blood lymphocyte subsets in whole blood samples from cynomolgus monkeys. OBJECTIVE: The purpose of this study was to optimize and validate a flow cytometric assay for immunophenotyping lymphocytes in the peripheral blood of cynomolgus monkeys. METHODS: A series of prevalidation experiments were done to determine optimal reagents, volumes, timing, and other procedural details of the flow cytometric assay. Using the optimized method, we then determined precision, interindividual variation, laboratory-to-laboratory variability, and sample stability. Stabilized human blood was used as a positive control for staining, processing, and analysis. The percentage and number of pan-T cells (CD3+), T-helper cells (CD3+4+), T cytotoxic/suppressor cells (CD3+8+), natural killer cells (CD3-16+), and B-cells (CD3-20+) were determined in 146 male and 140 female, clinically healthy monkeys and reference intervals were calculated. RESULTS: By doing 4-color staining with a lyse-wash method, intra- and interassay precision were <5% for all lymphocyte subsets. Variability between technicians and laboratories was minimal (CVs<3%). Samples were stable for up to 24 hours after staining and fixing. CONCLUSIONS: The validated method is extremely robust and can be performed under good laboratory practice conditions to support nonclinical studies. Reference intervals for lymphocyte subsets were similar to those previously reported. 相似文献
49.
Vervenne RA Jones SL van Soolingen D van der Laan T Andersen P Heidt PJ Thomas AW Langermans JA 《Veterinary immunology and immunopathology》2004,101(1-2):61-71
To examine the effect of recombinant bovine interferon-gamma (rbIFN-gamma) on cattle persistently infected with bovine leukemia virus (BLV), BLV-infected cattle were inoculated intraperitoneally with IFN-gamma. All cattle were febrile after inoculation with IFN-gamma and then recovered within 48 h. Flow cytometric analysis showed that the numbers of CD4+ and CD8+ T cells were decreased for 2-3 days and then their numbers were recovered. The number of gammadelta T cells increased after the fever. In contrast, the number of IgM+ lymphocytes remained low for about 1 week. Moreover, the numbers of syncytia produced by peripheral blood lymphocytes decreased and remained low compared to that before IFN-gamma administration. These results suggest that IFN-gamma induces the up-regulation of gammadelta T cells, decreases the number of IgM+ lymphocytes and suppresses the growth of BLV in BLV-infected cattle in vivo. 相似文献
50.
Thomas J Inzana Gretchen E Glindemann Gerald Snider Susan Gardner Lisa Crofton Barbara Byrne Joseph Harper 《Journal of veterinary diagnostic investigation》2004,16(5):374-381
Francisella tularensis type A is the primary cause of tularemia in animals and humans in North America. The majority of research on F. tularensis has been done with the attenuated live vaccine strain (LVS), which is a type B, but very few wild-type F. tularensis strains have been characterized. A gram-negative coccobacillus that was isolated in pure culture from the lungs of a cat that died after being lost for 5 days was received for identification at the Virginia-Maryland Regional College of Veterinary Medicine Teaching hospital. The isolate (strain TI0902) was not identified (or was misidentified) by commercial identification systems; however, it was identified as F. tularensis subspecies tularensis (type A) by sequencing a portion of the 16S ribosomal RNA gene. Furthermore, repetitive extragenic palindromic sequences-polymerase chain reaction amplified a 4-kb DNA fragment from TI0902 that was characteristic of F. tularensis type A but not type B. The electrophoretic profile of the lipopolysaccharide of strain TI0902 was identical to that of the LVS by Western blotting with antiserum to LVS. The protein-enriched outer membrane of strain TI0902 contained 6-8 proteins, which were similar in molecular size to those from the LVS. Electron microscopy of negatively stained and alcian blue-stained LVS and TI0902 cells showed that both strains were coccobacillary in shape and may be encapsulated. However, after mouse challenge, the TI0902 strain was clearly more virulent than the LVS strain. Results of this study indicate that the genotype and phenotype of wild-type F. tularensis type A strain TI0902 is similar, but not identical, to that of the LVS strain. Further studies will help determine whether pathogenesis and host-pathogen interactions are also similar between the 2 strains. 相似文献