全文获取类型
收费全文 | 6612篇 |
免费 | 309篇 |
国内免费 | 4篇 |
专业分类
林业 | 441篇 |
农学 | 193篇 |
基础科学 | 40篇 |
1166篇 | |
综合类 | 1378篇 |
农作物 | 240篇 |
水产渔业 | 391篇 |
畜牧兽医 | 2461篇 |
园艺 | 184篇 |
植物保护 | 431篇 |
出版年
2022年 | 55篇 |
2021年 | 87篇 |
2020年 | 139篇 |
2019年 | 132篇 |
2018年 | 141篇 |
2017年 | 127篇 |
2016年 | 138篇 |
2015年 | 116篇 |
2014年 | 140篇 |
2013年 | 280篇 |
2012年 | 322篇 |
2011年 | 424篇 |
2010年 | 240篇 |
2009年 | 182篇 |
2008年 | 338篇 |
2007年 | 336篇 |
2006年 | 303篇 |
2005年 | 312篇 |
2004年 | 288篇 |
2003年 | 292篇 |
2002年 | 273篇 |
2001年 | 80篇 |
2000年 | 87篇 |
1999年 | 104篇 |
1998年 | 65篇 |
1997年 | 59篇 |
1996年 | 56篇 |
1995年 | 45篇 |
1994年 | 53篇 |
1993年 | 54篇 |
1992年 | 54篇 |
1991年 | 66篇 |
1990年 | 67篇 |
1989年 | 56篇 |
1988年 | 45篇 |
1987年 | 51篇 |
1986年 | 75篇 |
1984年 | 53篇 |
1983年 | 48篇 |
1980年 | 59篇 |
1979年 | 71篇 |
1978年 | 79篇 |
1977年 | 72篇 |
1976年 | 53篇 |
1975年 | 50篇 |
1974年 | 50篇 |
1973年 | 60篇 |
1970年 | 59篇 |
1968年 | 47篇 |
1966年 | 61篇 |
排序方式: 共有6925条查询结果,搜索用时 781 毫秒
751.
R B Grieve L T Glickman A K Bater M Mika-Grieve C B Thomas G J Patronek 《American journal of veterinary research》1986,47(2):329-332
A total of 174 dogs from an area hyperenzootic for Dirofilaria immitis were grouped into 4 age categories and necropsied; information was obtained on adult D immitis infections and on the presence of microfilariae. Serum samples from these dogs were examined by an enzyme-linked immunosorbent assay (ELISA) for antibody to adult D immitis and by an indirect fluorescent antibody test (IFAT) for antibody to microfilarial surface antigens. In dogs less than or equal to 5 months of age, necropsy demonstrated no evidence of infection; however, positive serologic results indicated that some of these dogs had prepatent infections. The percentage of dogs with ELISA titers (positive) increased with age, as did the percentage of dogs with adult D immitis infections. The IFAT results were positive in some dogs in each age category. Sera from all 29 dogs with occult infections were positive by ELISA. Sera from 6 of 20 dogs with occult dual-sex heartworm infections and 1 of 9 dogs with occult single-sex heartworm infections were positive by IFAT. For diagnosing occult dirofilariasis, the ELISA had a positive predictive value which increased with age of the dog to a maximum of 65.0% in dogs greater than or equal to 12 months of age; ELISA had a negative predictive value of 100% in all age groups. In contrast, positive and negative predictive values for the IFAT decreased with age of the dog to 60% and 37.5%, respectively, in dogs greater than or equal to 12 months of age. 相似文献
752.
Immune responses to Mycoplasma bovis vaccination and experimental infection in the bovine mammary gland.
下载免费PDF全文
![点击此处可从《Canadian journal of veterinary research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
J T Boothby C E Schore D E Jasper B I Osburn C B Thomas 《Canadian journal of veterinary research》1988,52(3):355-359
This study characterized the immune responses in four vaccinated and four control cows in response to vaccination and experimental intramammary inoculation with Mycoplasma bovis. Specific antibody responses occurred in serum and milk in response to vaccination and experimental infection. Lymphocytes from peripheral blood, but not from the mammary gland of vaccinated cows had increased responsiveness to mitogens. No lymphocytes tested were responsive to M. bovis antigen. Both vaccination and experimental infection resulted in skin test reactivity. These results imply that vaccination results in immune responses which may alter the course of experimental M. bovis mastitis, but may contribute to cellular inflammation. 相似文献
753.
Carter LJ 《Science (New York, N.Y.)》1970,170(3959):718-719
754.
Thin-layer agarose isoelectric focusing: an improved technique for determining sheep hemoglobin type
An improved technique for rapid screening of sheep flocks for hemoglobin (Hb) type is presented. This technique, isoelectric focusing (IEF) on thin-layer agarose gels is simple, rapid, inexpensive and is suitable for screening large numbers of sheep for Hb type. With this technique, up to 100 sheep blood samples can be prepared, tested and interpreted within 2 h after samples are drawn. The new technique was shown to provide better resolution than polyacrylamide gel electrophoresis (PAGE) and was able to resolve samples in which the Hb had become partially degraded. These same samples could not be resolved by PAGE. The use of a special electroendosmosis-free grade of agarose provided resolution essentially equal to polyacrylamide as a matrix for IEF. The advantages are that the casting of the agarose gels is considerably easier, the focusing of samples is more rapid, staining and destaining times are greatly reduced and hazards from potential neurotoxicity of acrylamide are eliminated. Blood from 138 ewes at the Oregon State University Sheep Center was examined by the new agarose IEF technique to determine and demonstrate its usefulness for screening. No difficulty was encountered with interpretation of any of the samples. Frequencies of the HbA and B alleles were similar to those found in earlier studies when polyacrylamide tube gel electrophoresis was used. The observed frequencies were also similar to those expected with the population in Hardy-Weinberg equilibrium. 相似文献
755.
Bacterial overgrowth associated with a naturally occurring enteropathy in the German shepherd dog 总被引:2,自引:0,他引:2
Quantitative and qualitative bacteriological studies were performed on duodenal juice from 19 dogs with chronic small intestinal disease. Bacterial overgrowth was demonstrated in seven German shepherd dogs with minimal histological but specific biochemical abnormalities in the jejunal mucosa. Most frequently this overgrowth comprised bacteria of the normal flora, particularly Escherichia coli and enterococci, but these were occasionally accompanied by bacteria rarely present in the proximal small intestine of the normal dog, particularly Clostridium species. In most cases this overgrowth was associated with raised serum folate and reduced serum vitamin B12 concentrations, a finding consistent with the capacity of many enteric bacteria to synthesise folate and bind vitamin B12. 相似文献
756.
757.
The effect of vaccination on mycoplasmal infection and the cellular inflammatory response was evaluated in 4 vaccinated and 4 control cows experimentally challenged in 2 of 4 quarters with live Mycoplasma bovis. In unchallenged quarters during the first three weeks after experimental challenge exposure, 6 of 8 quarters on control cows, and 7 of 8 quarters on vaccinated cows became infected with low numbers (10(2)-10(4) cfu/ml) of M bovis. During the same period all challenge-infused quarters on both control and vaccinated animals became infected with high numbers (10(9) cfu/ml) of M bovis. Thereafter, all quarters on vaccinated cows became culture-negative for M bovis, while 2 of 8 unchallenged quarters, and 4 of 8 challenged quarters on 3 of 4 control cows remained infected. A cellular inflammatory response as measured by the California Mastitis Test accompanied the experimental infection in proportion to the infection level except in challenged quarters on vaccinated cows after the first three weeks post challenge in which the cellular inflammatory response remained high despite the advent of negative M bovis culture results. This study indicates that the course of experimental M bovis mastitis can be affected by vaccination, and that vaccination results in an adverse cellular inflammatory response in challenged quarters. 相似文献
758.
R A Oellermann P Carter M J Marx 《The Onderstepoort journal of veterinary research》1976,43(4):185-188
The IgM and IgG response of mice to sheep erythrocytes (SRBC) and bluetongue virus (BTV) was determined by means of haemolytic plaque assays. Maximum primary IgM response to SRBC occurred after 4 days but declined rapidly to 4% of the maximum by Day 9. A lag period of about 2 days was observed in the appearance of IgG haemolytic plaque-forming cells (PFC) but they reached a maximum after 6-9 days. Secondary immunization resulted in the stimulation particularly of IgG PFC and from Day 6 onwards IgG predominated in the immunological response. The IgM response to BTV was remarkably similar to that observed when SRBC were used as antigen. IgG PFC, however, appeared within a day of the IgM, reaching a peak on Days 4-5. From then onwards, IgG PFC predominated in the response. At BTV concentrations of up to 10 mug per mouse, the virulent strain of BTV type 3 produced the weakest response. At higher antigen concentrations there was very little difference in the response to the serotypes tested, although the virulent strain of BTV type 4 tended to produce the strongest response. 相似文献
759.
N-Methyl-N'-nitro-N-nitrosoguanidine was used in a modified and improved procedure to obtain streptomycin-dependent mutants of type A Pasteurella multocida and type 1 Pasteurella haemolytica. The relative virulence of these mutants was determined by mouse inoculation with and without streptomycin. 相似文献
760.
J E Thomas 《Journal of the American Veterinary Medical Association》1979,174(7):705-707
Sterilized and unsterilized catheters were passed into the urinary bladders of 9 clinically normal adult male dogs once daily for 5 consecutive days, and the dogs were examined for up to 30 days to determine whether urinary tract infections developed. Two dogs that were catheterized with clean unsterilized catheters (1 clinically normal dog and 1 dog given immunosuppressant drugs) developed persistent cystitis and pyelonephritis due to infection with Proteus sp. One dog given immunosuppressant drugs developed a mixed bacterial infection (Proteus sp and Escherichia coli) that resolved without treatment between 22 and 30 days later. 相似文献