全文获取类型
收费全文 | 188834篇 |
免费 | 10392篇 |
国内免费 | 108篇 |
专业分类
林业 | 7722篇 |
农学 | 6014篇 |
基础科学 | 1321篇 |
22531篇 | |
综合类 | 33233篇 |
农作物 | 7054篇 |
水产渔业 | 9534篇 |
畜牧兽医 | 96352篇 |
园艺 | 2373篇 |
植物保护 | 13200篇 |
出版年
2018年 | 2450篇 |
2017年 | 2651篇 |
2016年 | 2502篇 |
2015年 | 2191篇 |
2014年 | 2703篇 |
2013年 | 7004篇 |
2012年 | 5000篇 |
2011年 | 6192篇 |
2010年 | 4017篇 |
2009年 | 4091篇 |
2008年 | 6217篇 |
2007年 | 5847篇 |
2006年 | 5702篇 |
2005年 | 5282篇 |
2004年 | 5254篇 |
2003年 | 5241篇 |
2002年 | 5075篇 |
2001年 | 5969篇 |
2000年 | 5775篇 |
1999年 | 4733篇 |
1998年 | 2016篇 |
1997年 | 1980篇 |
1996年 | 1888篇 |
1995年 | 2234篇 |
1994年 | 2099篇 |
1993年 | 2014篇 |
1992年 | 3979篇 |
1991年 | 4156篇 |
1990年 | 4260篇 |
1989年 | 4142篇 |
1988年 | 3844篇 |
1987年 | 3860篇 |
1986年 | 3984篇 |
1985年 | 3821篇 |
1984年 | 3252篇 |
1983年 | 2894篇 |
1982年 | 1970篇 |
1981年 | 1847篇 |
1980年 | 1821篇 |
1979年 | 2943篇 |
1978年 | 2437篇 |
1977年 | 2103篇 |
1976年 | 1919篇 |
1975年 | 2024篇 |
1974年 | 2565篇 |
1973年 | 2621篇 |
1972年 | 2565篇 |
1971年 | 2339篇 |
1970年 | 2208篇 |
1969年 | 2096篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
151.
Y Sugawara K Hirasawa M Takeda J S Han K Doi 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》1991,53(3):463-468
One-month-old Syrian hamsters of the APA and Std: golden strains were inoculated intraperitoneally with 10(5) PFU/head of the D variant of encephalomyocarditis (EMC) virus and examined virologically and pathologically up to 7 days after inoculation. APA hamsters developed apparent hyperglycemia due to pancreatic islet cell damage while Std:golden hamsters did not. Hamsters of both strains showed clear histopathologic changes in the testis with prominent viral replication as well as in the brain, heart and exocrine pancreas. The susceptibility to EMC virus-infection was higher in males than in females and in APA than in Std: golden hamsters. 相似文献
152.
An ammonium sulfate fraction of Taenia hydatigena cyst fluid (ThFAS) was further fractionated by hydrophobic interaction chromatography, using alkylagarose and omega-amino alkylagarose columns, in an effort to isolate and purify a specific diagnostic antigen in the ThFAS preparation. The less than 12 kDa antigen was found to have an affinity for immobilized alkanes with chain length of six carbons or greater. The antigen was recovered in an ethylene glycol eluate from a hexylagarose column then analyzed by Western blot; it reacted with bovine and human cysticercosis infection sera and with specific monoclonal antibodies but not with control sera or fascioliasis infection sera. When the eluate was used as coating antigen in a plate ELISA assay no false positive reactions were seen in sera from cattle infected with Fasciola hepatica; false positive reactions were observed for the unfractionated ThFAS antigen preparation. 相似文献
153.
Thyroid scintigraphy in small animals 总被引:1,自引:0,他引:1
154.
155.
156.
157.
In the domestic pig, a circadian rhythm of plasma cortisol occurs, with greatest concentrations in the morning and lowest concentrations in the afternoon. However, photic entrainment of the rhythms of ACTH and melatonin in pigs have not been defined clearly. This experiment was designed to evaluate free-running rhythms of ACTH, cortisol and melatonin in pigs housed in constant light (LL) and constant darkness (DD). Twelve crossbred barrows, maintained under ambient photoperiod, were catheterized and tethered individually in two environmentally controlled rooms, one with LL and the other with DD. For animals in LL, fluorescent lights provided 202 +/- 15 (mean +/- standard deviation) lux of light at 65 cm above the floors. Incandescent nightlights equipped with 7 watt red bulbs provided 7 +/- 2 lux and were illuminated continuously in both rooms. Pigs were given at least 14 d exposure to LL and DD, then samples of plasma and serum were obtained at hourly intervals for 48 hr. Plasma was assayed for ACTH, and serum for cortisol and melatonin. Periodograms were constructed to analyze the data. For this type of analysis, a statistic, Qp, is calculated, and circadian periodicity is suggested if maximum Qp (Qp max) occurs at or near 24 hr. The period of the free-running rhythms (tau) at Qp max for ACTH, cortisol and melatonin for pigs in LL (23.80 +/- .01, 23.78 +/- .01, and 23.21 +/- .02 hr, respectively) did not differ significantly from those for pigs in DD (23.39 +/- .01, 23.20 +/- .01, and 22.55 +/- .02 hr, respectively).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
158.
J Sherrill T Schock J L Dunn D J St Aubin V V Burnley S E Poet 《Journal of zoo and wildlife medicine》2001,32(1):17-24
Humoral immune responses of black-footed penguins (Spheniscus demersus) to DNA-mediated immunization with a beta-galactosidase reporter gene expression plasmid were evaluated. Six male and 6 female adult penguins received either test plasmid, pCMV-beta, containing the beta-galactosidase gene or control plasmid, pCI, lacking a gene for expression. Three birds from each group were used previously in a diluent control group and given one injection of sterile saline. All samples were screened for anti-beta-galactosidase antibodies by indirect enzyme-linked immunosorbent assay with anti-chicken immunoglobulin G as secondary antibody. Antibodies to beta-galactosidase were detected in the sera of pCMV-beta-inoculated penguins, with a peak response on day 21. Antibody titers of the test plasmid group versus both control groups on days 21, 28, and 42 differed significantly. These results demonstrate that black-footed penguins can be safely transfected with the gene encoding beta-galactosidase and will mount a humoral response against the in vivo-expressed protein. Knowledge from this initial study can be applied to the development of DNA-mediated vaccines against specific infectious diseases of penguins. 相似文献
159.
C. P. Verschueren P. J. Selman J. J. M. de Vijlder J. A. Mol 《Domestic animal endocrinology》1991,8(4):509-519
Canine thyroglobulin (cTg) has been isolated and purified. It has similar electrophoretic patterns as Tg from other mammalian species. The main fraction had a MW of 660,000, whereas also fractions of a MW of approximately 1,300,000 (dimer) and 330,000 (subunit) were present. The iodine content was 0.8 to 1.0 % (w/w). cTg did not cross-react with antibodies against human Tg to a degree that would allow the use of a radioimmunoassay for human Tg for the determination of cTg in serum or plasma. Therefore a polyclonal antiserum was raised against cTg and a homologous radioimmunoassay was developed, which was sensitive (0.4 μg/l) and specific (cross-reactivity in cTg assay of human Tg, goat Tg, T4, T3, and DIT < 0.01 %).
Plasma Tg levels in normal dogs of both sexes and aged 3–15 years amounted to 192 ± 73 μg/l (mean ± SD, n=30). There was no relation between plasma Tg and T4 levels. 相似文献
160.