首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1490篇
  免费   74篇
  国内免费   1篇
林业   71篇
农学   40篇
基础科学   4篇
  285篇
综合类   116篇
农作物   71篇
水产渔业   102篇
畜牧兽医   727篇
园艺   32篇
植物保护   117篇
  2024年   4篇
  2023年   22篇
  2022年   24篇
  2021年   46篇
  2020年   33篇
  2019年   52篇
  2018年   43篇
  2017年   20篇
  2016年   37篇
  2015年   31篇
  2014年   58篇
  2013年   62篇
  2012年   114篇
  2011年   139篇
  2010年   70篇
  2009年   62篇
  2008年   105篇
  2007年   108篇
  2006年   90篇
  2005年   81篇
  2004年   66篇
  2003年   56篇
  2002年   65篇
  2001年   13篇
  2000年   13篇
  1999年   9篇
  1998年   8篇
  1997年   10篇
  1996年   16篇
  1995年   12篇
  1994年   9篇
  1993年   5篇
  1992年   5篇
  1991年   5篇
  1990年   3篇
  1989年   6篇
  1988年   3篇
  1986年   4篇
  1985年   4篇
  1984年   5篇
  1983年   5篇
  1982年   3篇
  1980年   3篇
  1978年   3篇
  1977年   6篇
  1975年   4篇
  1971年   2篇
  1970年   2篇
  1969年   4篇
  1966年   2篇
排序方式: 共有1565条查询结果,搜索用时 46 毫秒
51.
Canine infectious respiratory disease (CIRD) is a multi-factorial infection that affects many kennelled dogs despite the wide use of vaccination. Current vaccines aim to protect against viral agents and a single bacterial agent, Bordetella bronchiseptica. We sought to examine the role of streptococcal species in CIRD. The isolation and identification of streptococci in the lower respiratory tract of clinically healthy dogs and those with CIRD were used to correlate the presence of specific streptococcal species with respiratory disease. In this study we report that the presence of S. equi subsp. zooepidemicus is associated with increasing severity of disease in a population of kennelled dogs with endemic CIRD.  相似文献   
52.
53.
The jojoba, Simmondsia chinensis, is a characteristic desert plant native to the Sonoran desert. The jojoba meal after oil extraction is rich in protein. The major jojoba proteins were albumins (79%) and globulins (21%), which have similar amino acid compositions and also showed a labile thrombin-inhibitory activity. SDS-PAGE showed two major proteins at 50 kDa and 25 kDa both in the albumins and in the globulins. The 25 kDa protein has trypsin- and chymotrypsin-inhibitory activities. In vitro digestibility of the globulins and albumins resembled that of casein and soybean protein concentrates and was increased after heat treatment. The increased digestibility achieved by boiling may be attributed to inactivation of the protease inhibitors and denaturation of proteins.  相似文献   
54.
OBJECTIVE: To determine elemental composition of teeth with and without odontoclastic resorption lesions (ORL) in cats. SAMPLE POPULATION: Normal teeth from 22 cadaver cats and ORLaffected teeth from 21 cats admitted to the veterinary hospital for dental treatment. PROCEDURE: An electron microprobe was used to analyze weight percentages of calcium, phosphorus, fluorine, sodium, magnesium, sulfur, potassium, and iron in enamel, dentin, and cementum. RESULTS: Calcium and phosphorus were the most abundant elements. Fluorine, sodium, and magnesium combined were < 5% and sulfur, potassium, and iron combined were < 0.1% of total elemental composition. In enamel of normal teeth, a significant sex-by-jaw location interaction was seen in mean (+/- SD) phosphorus content, which was higher in mandibular teeth of females (1764+/-0.41%) but lower in mandibular teeth of males (16.71+/-0.83%). Mean iron content in dentin of normal teeth was significantly lower in mandibular teeth than maxillary teeth (0.014+/-0.005% vs 0.023+/-0.019%). Mean enamel sodium content was significantly higher (0.77+/-0.046% vs 0.74+/-0.025) and mean enamel iron content was significantly lower (0.017+/-0.008% vs 0.021+/-0.005%) in ORLaffected teeth, compared with normal teeth. In cementum, mean fluorine content was significantly lower (2.98%+/-0.27 vs 2.99+/-0.20%) and mean magnesium content was significantly lower (0.54+/-0.13% vs 0.60+/-0.13%) in ORL affected teeth, compared with normal teeth. CONCLUSIONS AND CLINICAL RELEVANCE: Results of our study establish baseline mineral content of enamel, dentin, and cementum for normal teeth in cats. Minimal differences in mineral content of enamel and cementum of normal and ORL-affected teeth were detected.  相似文献   
55.
56.
Antibodies directed toward gram-negative core antigens (GNCAs) have been demonstrated in many mammalian species but to date are unexamined in any avian species. An enzyme-linked immunosorbent assay with phenol-killed whole cell Escherichia coli J5 was used to assess the presence of serum antibodies directed toward GNCAs in chickens. The first experiment consisted of collecting blood samples from randomly selected hens at egg laying ranches in northern California. The ages ranged from several days of age to 77 wk of age. Birds were classified into age groups (hatchling [1 day-4 wk], pullet [4-18 wk], pullet cycle [18-60 wk], and postmolt [>60 wk]) and husbandry style for titer comparison. The geometric mean titer (GMT) for all adult hens regardless of age was 2147. The geometric mean titers were 220, 5691, 2304, and 1776 for hatchlings, pullets, pullet cycle hens, and postmolt hens, respectively. The age group titer trends were similar to those of humans rather than those of farm animals in that the highest titers occurred during "adolescence" (pullets) and titers decreased slightly with maturity. The GMTs were 2870 for hens housed intensively and 1872 for those housed extensively. The second experiment looked at the progression of GNCA titers within individual birds over a 1-yr period. Individual titers increased slightly throughout the study time of the second experiment.  相似文献   
57.
Topical vecuronium bromide (Norcuron) and combinations with atropine and phenylephrine, were evaluated as mydriatics in juvenile double-crested cormorants (Phalacrocorax auritus). Nine cormorants were treated with each of four protocols: 1% atropine; 4 mg/mL vecuronium bromide (total 0.16 mg/eye); atropine with vecuronium; and atropine, 2.5% phenylephrine, followed by vecuronium. Drugs were applied topically at 15-min intervals (0.01 mL/drop). Pupil diameter was measured manually every 15 min with a pupil gauge calibrated to the nearest 0.5 mm. No effect was observed with atropine alone. Average +/- SD peak pupil diameter for vecuronium, atropine/vecuronium, and atropine/phenylephrine/vecuronium were 5.4 +/- 1.1 mm, 5.7 +/- 0.8 mm and 6.2 +/- 0.4 mm, respectively; and duration of peak diameters were 38 +/- 28 min, 79 +/- 71 min and 103 +/- 58 min, respectively. The combined atropine, phenylephrine and vecuronium provided the most consistent dilation with larger average pupil size and longer average duration. No side-effects from vecuronium were observed in these birds.  相似文献   
58.
Cell cultures infected with BHV-1/F(syn), a recombinant bovine herpesvirus 1 (BHV-1) which expresses a synthetic open reading frame encoding the fusion (F) protein of the bovine respiratory syncytial virus (BRSV), showed a cytopathic effect (CPE) indistinguishable from that induced by wildtype BHV-1 although transient transfection experiments demonstrated that expression of the F protein leads to formation of large syncytia. Since it has been shown that glycoprotein M (gM) of pseudorabies virus inhibits BRSV F-induced syncytium formation in transient plasmid transfection experiments [Pseudorbies virus glycoprotein M inhibits membrane fusion. J. Virol. 74 (2000) 6760], the gM ORF of wtBHV-1 and BHV-1/F(syn) was interrupted. Infection of cell cultures with the resulting gM(-) mutant of BHV-1/F(syn) led to formation of syncytia, whereas the CPE in gM(-)BHV-1 infected cells was comparable to the CPE in wtBHV-1 infected cultures. Our results demonstrate that gM is not essential for BHV-1 replication in cell culture and that gM is involved in inhibition of the cell fusion activity of the BHV-1 expressed BRSV F protein.  相似文献   
59.
60.
A PCR assay was validated for the detection of Mycoplasma hyopneumoniae in porcine lung tissue. The detection limit of the assay was 0.18 colony-forming units/g of lung sample spiked with M. hyopneumoniae. In field validation, 426 pigs from 220 cases were examined for M. hyopneumoniae infection by M. hyopneumoniae PCR and a fluorescent antibody (FA) test. In total, 103 pig lungs (24.2%) were positive in the PCR test, and 69 pig lungs (16.2%) were positive in the FA test, among which, 62 pigs were positive for both PCR and FA test. Most of the PCR-positive but FA test-negative cases had lesions compatible with M. hyopneumoniae infection. With Bayesian modeling, the diagnostic sensitivity and specificity of the PCR were determined to be 97.3% and 93.0%, respectively.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号