全文获取类型
收费全文 | 2250篇 |
免费 | 351篇 |
国内免费 | 148篇 |
专业分类
林业 | 44篇 |
农学 | 56篇 |
基础科学 | 8篇 |
47篇 | |
综合类 | 612篇 |
农作物 | 48篇 |
水产渔业 | 263篇 |
畜牧兽医 | 1433篇 |
园艺 | 110篇 |
植物保护 | 128篇 |
出版年
2024年 | 9篇 |
2023年 | 41篇 |
2022年 | 54篇 |
2021年 | 75篇 |
2020年 | 99篇 |
2019年 | 152篇 |
2018年 | 89篇 |
2017年 | 143篇 |
2016年 | 153篇 |
2015年 | 99篇 |
2014年 | 128篇 |
2013年 | 132篇 |
2012年 | 169篇 |
2011年 | 170篇 |
2010年 | 134篇 |
2009年 | 146篇 |
2008年 | 120篇 |
2007年 | 128篇 |
2006年 | 107篇 |
2005年 | 99篇 |
2004年 | 79篇 |
2003年 | 78篇 |
2002年 | 51篇 |
2001年 | 67篇 |
2000年 | 40篇 |
1999年 | 36篇 |
1998年 | 29篇 |
1997年 | 21篇 |
1996年 | 15篇 |
1995年 | 19篇 |
1994年 | 17篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1956年 | 2篇 |
排序方式: 共有2749条查询结果,搜索用时 31 毫秒
11.
12.
Jezie A. Acorda DVM Magr Haruo Yamada DVM DVSc Seyed Mehdi Ghamsari DVM 《Veterinary radiology & ultrasound》1994,35(3):196-200
Ultrasonography of the liver was performed in 200 Holstein-Friesian dairy cattle using a 3.5 MHz transducer with a linear array electronic scanner. Liver samples were taken, processed and examined microscopically and the fat occupying rate was calculated. The hepatic ultrasonograms were evaluated according to the presence of bright pattern, dark pattern, deep attenuation, vascular blurring and blurring of edges. Of the 200 animals, 96 had a normal liver, 63 had hydropic degeneration of the liver, 37 had fatty infiltration of the liver, 3 had liver dystrophy and I had hepatic amyloidosis, diagnosed through histopathological examination. Amyloidosis was characterized by bright pattern and blurring of edges. Liver dystrophy had higher percentages of bright pattern and blurring of edges than normal liver. Hydropic degeneration had higher percentages of dark pattern and blurring of edges than normal liver. Fatty infiltration had higher percentages of bright pattern, deep attenuation, vascular blurring and blurring of edges than normal liver. The present results suggest that different ultrasonographic patterns can be observed in various diffuse hepatocellular disorders in dairy cattle 相似文献
13.
研究结果表明,无论是香菇生料菌砖栽培,还是金针菇熟料袋栽,菌种世代的多少对产量均无明显的影响,这可能是由于菌种通过无性繁殖,遗传性变异甚小之故;研究结果还表明,金针菇菌丝生长的速度似乎有随着菌种工代的增多而加快的趋势,这窨是由于低代菌种自琼脂培养基移接天以杂本屑,棉籽壳等为主要原料的粗质培养基上的时间较短,适应酶的活性较弱,分解,利用高分子化合物的能力较差,故菌丝生长速度较为缓慢?还是由于其他原因 相似文献
14.
Acquired resistance triggered by elicitins in tobacco and other plants 总被引:17,自引:0,他引:17
Philippe Bonnet Eva Bourdon Michel Ponchet Jean -Pierre Blein Pierre Ricci 《European journal of plant pathology / European Foundation for Plant Pathology》1996,102(2):181-192
Elicitins are a family of proteins excreted byPhytophthora spp. They exhibit high sequence homology but large net charge differences. They induce necrosis in tobacco plants which then become resistant to the tobacco pathogenPhytophthora parasitica var.nicotianae. In stem-treated plants, resistance was not restricted to the site of elicitin application, but could be demonstrated by petiole inoculation at all levels on the stem. Resistance was already maximum after two days and lasted for at least two weeks. It was effective not only towardsP. p. var.nicotianae infection, but also against the unrelated pathogenSclerotinia sclerotiorum. In contrast to dichloroisonicotinic acid, an artificial inducer of systemic acquired resistance, which was increasingly effective with doses ranging from 0.25 to 5mole per plant, the basic elicitin cryptogein exhibited a threshold effect, inducing near total resistance and extensive leaf necrosis above 0.1 nmole per plant. Between 1 and 5 nmole, acidic elicitins (capsicein and parasiticein) protected tobacco plants with hardly any necrotic symptom. Elicitins exhibited similar effects in various tobacco cultivars andNicotiana species, although with quantitative differences, but induced neither necrosis nor protection in other SolanaceÆ (tomato, petunia and pepper). Among 24 additional species tested belonging to 18 botanical families, only some BrassicaceÆ, noticeably rape, exhibited symptoms in response to elicitins, in a cultivar-specific manner. Elicitins appear to be natural specific triggers for systemic acquired resistance and provide a tool for unraveling the mechanisms leading to its establishment.Abbreviations AR
acquired resistance
- HR
hypersensitive response
- INA
2,6-dichloroisonicotinic acid
- Ppn
Phytophthora parasitica var.nicotianae
- SAR
systemic acquired resistance 相似文献
15.
Latimer KS Bounous DI Colatos C Carmichael KP Howerth EW 《Veterinary clinical pathology / American Society for Veterinary Clinical Pathology》1996,25(1):23-26
Extreme eosinophilia with disseminated eosinophilic granulomatous disease is described in a 4-year-old Arabian mare. Clinical signs included weight loss, coughing, jugular distention, and ventral edema. Cutaneous lesions were not observed. Eosinophilic inflammation was observed in cytologic specimens from the respiratory tract, body cavities, and lymph nodes. At necropsy, a 20-cm diameter intrathoracic mass was observed. Smaller nodules were present in the lymph nodes, liver, spleen, adrenal glands, pancreas, and skeletal muscle. Histologically, these masses and nodules were characterized by infiltrates of eosinophils, macrophages, and multinucleated giant cells, reactive fibroplasia; and multifocal eosinophilic coagula. Microscopically, mild eosinophilic infiltrates were observed in sections of stomach, small intestine, colon, and pleura; however, gross lesions were not observed in these tissues at necropsy. The etiology of the extreme eosinophilia and disseminated eosinophilic granulomatous disease in this horse was not determined. 相似文献
16.
塔里木河流域生态环境恶化的水文效应 总被引:12,自引:9,他引:12
塔里木河是我国最大的内陆河。 4条源流出山口多年平均天然径流量 2 2 4 .9× 10 8m3 (195 7~ 2 0 0 1年 )。在全球变暖的大背景下 ,塔里木河流域山区气候出现变暖增湿的趋势 ,2 0世纪 90年代径流量达 2 4 1.9× 10 8m3 ,增幅 7.6 %。由于源流区人类开发利用水资源的影响 ,使得补给塔里木河干流的水量不断减少 ,水文条件改变 ,造成干流上、中游段耗水严重 ,导致下游生态与环境急剧退化。自 2 0 0 0年以来 ,实施的从开都河—博斯腾湖向下游绿色走廊应急输水 ,已使下游生态环境开始恢复生机。 相似文献
17.
AIM:To explore the serum levels of certain adhesion molecules and its significance in acute coronary syndrome(ACS). METHODS:The subjects included 40 patients with acute myocardial infarction(AMI) and 40 patients with unstable angina pectoris (UAP). Among the 80 patients, 60 patients accepted a follow-up 4 months. At the same time we selected 40 controls from people who attended a routine health check in the university. Serum levels of E-selectin, sICAM-1, sVCAM-1 were measured by ELISA.RESULTS:Serum levels of E-selectin, sICAM-1, sVCAM-1 were significantly higher in the ACS group(AMI or UAP) than in the control group. Four months later, the levels of E-selectin, sICAM-1 became significantly lower in the follow-up group than in the ACS group, while sVCAM-1 showed no significant difference. CONCLUSION:Serum levels of E-selectin, sICAM-1 may have certain diagnostic value for ACS, and can be a useful marker reflecting the stability of the disease. 相似文献
18.
A polymerase chain reaction (PCR)-based method was developed to detect DNA of Fusarium solani f. sp. glycines , the cause of soybean sudden death syndrome. Two pairs of primers, Fsg1/Fsg2 designed from the mitochondrial small subunit ribosomal RNA gene, and FsgEF1/FsgEF2 designed from the translation elongation factor 1-α gene, produced PCR products of 438 and 237 bp, respectively. Primer specificity was tested with DNA from 82 F. solani f. sp. glycines , 55 F. solani non-SDS isolates, 43 isolates of 17 soybean fungal pathogens and the oomycete Phytophthora sojae , and soybean. The sensitivity of primer Fsg1/Fsg2 was 10 pg while that of FsgEF1/FsgEF2 was 1 ng when using F. solani f. sp. glycines total genomic DNA or down to 103 macroconidia g−1 soil. Nested PCR increased the sensitivity of the PCR assay 1000-fold to 10 fg using primers Fsg1/Fsg2, and 1 pg using primers FsgEF1/FsgEF2. F. solani f. sp. glycines DNA was detected in field-grown soybean roots and soil by PCR using either single pairs of primers or the combination of two pairs of primers. The occurrence of F. solani f. sp. glycines was determined using nested PCR for 47 soil samples collected from soybean fields in 20 counties of Illinois in 1999. F. solani f. sp. glycines was detected in soil samples from all five Illinois Agricultural Statistic Districts including 100, 89, 50, 92 and 50% of the samples from East, Central, North-east and West Districts, respectively. 相似文献
19.
AIM: To explore the variation of blood biochemistry and arterial blood gas of patients with systemic inflammatory response syndrome (SIRS) in the early time after trauma and improve the diagnosis and first aid. METHODS: Eighty-eight patients with trauma from August 2003 to February 2004 were divided into two groups by their AIS-ISS90 score. The data of temperature, pulse, respiratory rate, white blood cell counts, Hb, blood glucose and arterial blood gas (PaO2, PaCO2, HCO3-, AG) were collected and compared with each group by statistic methods. RESULTS: Of the 88 patients, 49 underwent SIRS, 12 in light trauma group (ISS≥16) and 37 in severe trauma group (ISS<16). Compared with light trauma group, the data of pulse, respiratory rate, white blood cell counts, blood glucose, AG and rate of SIRS of severe trauma group were higher, PaO2 and HCO3- were lower and the cases of PaCO2>45 mmHg or <35 mmHg were more (P<0.01). The data of temperature and Hb had not significant difference between two groups (P>0.05). 13 patients had MODS in severe trauma group and 2 died while none had MODS or died in light trauma group. CONCLUSION: Application of AIS-ISS90 and SIRS-related blood biochemistry and arterial blood gas is beneficial for the diagnosis and treatment of patients in the early time after trauma. 相似文献
20.
AIM: To study the effect of propolis on the expression of CD54 and activation of NF-κB p65 in lung tissue of acute lung injury (ALI) rats. METHODS: 40 male Wistar rats were divided into 5 groups: normal control, model control, dectancyl group, water soluble derivative of propolis (WSP) group and ethanol extracted propolis (EEP) group. ALI animal model was performed by oleic acid and LPS twice attack. The pathologic slice was observed with light microscope and the NF-κB p65 activity and CD54 expression were tested by immunohistochemistry (SABC and SP). RESULTS: Both EEP and WSP antagonized the lung edema, decreased the inflammation and inhibited the expression of CD54 and activation of NF-κB p65. CONCLUSION: The increase in the expression of CD54 and the activation of NF-κB p65 in the lung tissues of ALI were involved in the formation of ALI. Propolis ameliorated the lung damage, which maybe related to the inhibition of CD54 expression and NF-κB p65 activation. 相似文献