全文获取类型
收费全文 | 8051篇 |
免费 | 424篇 |
专业分类
林业 | 1130篇 |
农学 | 264篇 |
基础科学 | 40篇 |
1540篇 | |
综合类 | 670篇 |
农作物 | 259篇 |
水产渔业 | 282篇 |
畜牧兽医 | 3419篇 |
园艺 | 168篇 |
植物保护 | 703篇 |
出版年
2023年 | 44篇 |
2022年 | 51篇 |
2021年 | 107篇 |
2020年 | 117篇 |
2019年 | 83篇 |
2018年 | 230篇 |
2017年 | 218篇 |
2016年 | 187篇 |
2015年 | 181篇 |
2014年 | 205篇 |
2013年 | 525篇 |
2012年 | 443篇 |
2011年 | 481篇 |
2010年 | 252篇 |
2009年 | 217篇 |
2008年 | 415篇 |
2007年 | 440篇 |
2006年 | 397篇 |
2005年 | 372篇 |
2004年 | 338篇 |
2003年 | 350篇 |
2002年 | 297篇 |
2001年 | 247篇 |
2000年 | 248篇 |
1999年 | 162篇 |
1998年 | 54篇 |
1997年 | 54篇 |
1996年 | 61篇 |
1995年 | 85篇 |
1994年 | 55篇 |
1993年 | 41篇 |
1992年 | 51篇 |
1991年 | 66篇 |
1990年 | 66篇 |
1989年 | 55篇 |
1988年 | 58篇 |
1987年 | 38篇 |
1986年 | 54篇 |
1985年 | 54篇 |
1984年 | 50篇 |
1983年 | 37篇 |
1980年 | 45篇 |
1977年 | 28篇 |
1976年 | 25篇 |
1973年 | 29篇 |
1971年 | 28篇 |
1970年 | 25篇 |
1969年 | 26篇 |
1968年 | 28篇 |
1966年 | 25篇 |
排序方式: 共有8475条查询结果,搜索用时 31 毫秒
11.
G Breves R Zitnan B Schr?der C Winckler H Hagemeister K Failing J Voigt 《Archives of Animal Nutrition》2002,56(5):371-377
In a previous study we found a positive correlation between early weaning in calves and morphological parameters which were indicative of ruminal development, i.e. the length and width of the papillae. The objective of the present study was to determine to what extent this observation could be reflected by modulations of absorptive and secretory functions of the rumen mucosa. For this purpose the short-circuit currents (Isc) as a measure of electrogenic net ion fluxes and the transepithelial conductances (G(T)) as a measure of the overall tissue permeability were measured in vitro applying the Ussing-chamber technique. Simultaneously, the unidirectional flux rates of sodium and chloride across rumen wall epithelia were determined in the absence of electrochemical gradients. Under these conditions, significant positive net flux rates (Jnet) clearly indicate active mechanisms for electrolyte absorption. For the experiments 12 male Holstein calves 7 d of age were assigned to three groups of 4 animals each: milk group (I, slaughtered after 6 weeks of age), late weaning group (II, slaughtered after 9 weeks of age) and early weaning group (II, weaned after 6 weeks of age and slaughtered after 9 weeks of age). Whereas G(T) values remained unaffected by different age and feeding, Isc values were significantly affected by early weaning but were not influenced by age. Irrespective of weaning time active absorption of Na+ tended to be higher by about 60% in 9 weeks old animals. Active absorption of chloride was significantly increased in milk fed 9 weeke old calves and this effect was further stimulated by early weaning. In conclusion, the data show an increasing active Na+ absorption with age in calf rumen that could not be influenced by early weaning. Similarly, active Cl- absorption was initially increased during postnatal development and this effect could be stimulated further by early weaning. 相似文献
12.
Kyungmin Han Inge Geurden Paul Van der Meeren Sungchul C. Bai Patrick Sorgeloos 《Journal of the World Aquaculture Society》2005,36(2):196-202
The present study examined the distribution of particle sizes in two experimental standardized lipid emulsions (distributed by ICES, International Council for the Exploration of the Sea) as a function of the preparation method (hand shaking or ultrasonic blending) and as a function of storage time. A 24-h enrichment trial compared the incorporated HUFA levels in the nauplii of Artemia franciscana .
The emulsion droplets in the 50% HUFA emulsion (ICES 50, ethyl ester based) were much smaller than in the 30% HUFA emulsion (ICES 30, triacylglycerol-based) in which 90% of the droplets had a diameter below 12.3 μm as compared to 1.3 pn in ICES 50. The blending method highly affected particle sizes. High-shear blending instead of the classical hand shaking of the emulsion of both ICES 30 and 50 reduced the mean particle size from 5.06 to 1.07 μm and from 0.38 to 0.11 μm, respectively. The particle size distributions remained stable during the 1-wk storage, suggesting the absence of agglomeration or bacterial development. The fatty acid composition of 24-h enriched Artemia reflected differences in the HUFA profile of the emulsions, but was independent of observed differences in the size of the particles. 相似文献
The emulsion droplets in the 50% HUFA emulsion (ICES 50, ethyl ester based) were much smaller than in the 30% HUFA emulsion (ICES 30, triacylglycerol-based) in which 90% of the droplets had a diameter below 12.3 μm as compared to 1.3 pn in ICES 50. The blending method highly affected particle sizes. High-shear blending instead of the classical hand shaking of the emulsion of both ICES 30 and 50 reduced the mean particle size from 5.06 to 1.07 μm and from 0.38 to 0.11 μm, respectively. The particle size distributions remained stable during the 1-wk storage, suggesting the absence of agglomeration or bacterial development. The fatty acid composition of 24-h enriched Artemia reflected differences in the HUFA profile of the emulsions, but was independent of observed differences in the size of the particles. 相似文献
13.
R J Slappendel I van der Gaag J J van Nes T S van den Ingh R P Happé 《The Veterinary quarterly》1991,13(1):30-40
A newly recognised disease, which we have given the provisional name of familial stomatocytosis-hypertrophic gastritis (FSHG), is described in two families of dogs of the Drentse partrijshond breed. The affected dogs consisted of 3 females and 5 males, 3 to 19 (mean 9.5) months of age at admission. The main clinical problems were diarrhoea, icterus, and ataxia and paresis of the pelvic limbs. Laboratory evaluation revealed abnormal red cell shape (stomatocytosis), increased osmotic fragility, haemolytic anaemia, and increased liver enzymes and serum bilirubin. Gastroscopic and histopathologic examination of the gastric mucosa revealed hypertrophic gastritis resembling Ménétrier's disease in man. Histologic findings in the liver were suggestive of progressive liver disease. Cysts were found in the kidneys of the five oldest patients. Electroneurography in 2 dogs revealed polyneuropathy. In the parents of 2 patients (sister and brother), there were no clinical or laboratory abnormalities. An autosomal recessive hereditary defect of lipid metabolism is suspected. 相似文献
14.
Alteration of nitrogen metabolism by alpha-ketoglutarate administration in growing lambs fed high nonprotein nitrogen-containing diets 总被引:1,自引:0,他引:1
Two completely randomized design experiments were conducted, using either 10, 38-kg (Exp. 1) or 10, 26-kg (Exp. 2) Hampshire x Western wether lambs, to study the effects of alpha-ketoglutarate (AKG) administration on N metabolism. Lambs were fed 890 and 885 g DM/d in Exp. 1 and 2, respectively, of corn-cottonseed hull basal diets with urea added to attain CP levels of 10.6 and 10.5% in Exp. 1 and 2, respectively. Experiments consisted of 10 d of adaptation followed by 7 d of infusion and excreta collection. Lambs were infused continuously either i.v. (Exp. 1) or abomasally (Exp. 2) with control solutions (CON) or solutions containing 41.3 g AKG/d (AKG). In Exp. 1, fecal and urinary N excretion and N retention were not affected (P greater than .10) by treatment. Compared to CON in Exp. 2, AKG infusion increased (P less than .10) fecal N output (6.6 vs 5.9 g N/d) but did not affect (P greater than .10) the amount of N retained (4.4 vs 3.5 g N/d). Compared to CON, AKG increased (P less than .10) urinary NH3 N excretion in Exp. 1. Serum urea N was lower (P greater than .10) for AKG than for CON in Exp. 1 but was not affected (P greater than .10) by treatment in Exp. 2. In Exp. 1, AKG appeared to reduce activities of several serum enzymes that function in amino N metabolism. In Exp. 1, compared to CON, AKG decreased (P less than .10) aspartate but increased (P less than .10) asparagine in serum.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
15.
16.
Dr. G. Götze 《Journal of pest science》1929,5(6):73-75
Ohne Zusammenfassung 相似文献
17.
Ohne Zusammenfassung 相似文献
18.
19.
20.
The histological appearance of peroral gastric biopsies in clinically healthy and vomiting dogs. 总被引:1,自引:1,他引:0
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)
I van der Gaag 《Canadian journal of veterinary research》1988,52(1):67-74
A survey of the histology of gastric biopsies in 501 dogs, consisting of 19 clinically healthy dogs and 482 vomiting dogs is presented. Whole stomachs of four young clinically healthy laboratory dogs were used as controls. Eleven percent of forceps biopsies were unsuitable for examination; all suction biopsies were of good quality. Slight to severe gastritis was found in 168 vomiting dogs (35%), whereas five dogs (26%) of the clinically healthy group showed a mainly slight gastritis. Superficial and diffuse gastritis were the most prominent findings in the 168 dogs with gastritis. A single type of gastritis was found in 114 dogs, a combination of different types in 54 dogs. Gastric atrophy was seen in 23 (5%) vomiting dogs and in three (15%) clinically healthy dogs, atrophy with a slight to severe fibrosis in 21 (4%) vomiting dogs, and in 84 (17%) vomiting dogs and two (11%) healthy dogs, gastric fibrosis was present. Carcinomas were seen in 26 vomiting dogs, of which 17 also had gastritis. A differential diagnosis of granulomatous gastritis/carcinoma had to be made in one case. Seven dogs showed a lymphosarcoma, and in six other dogs a differential diagnosis of lymphosarcoma and/or gastritis was made. One adenomatous polyp was seen. In one clinically healthy dog an adenomyoma was diagnosed. Ulceration was found in 24 dogs, but only five of these lacked other lesions. Other biopsy findings were pseudopyloric metaplasia, hyperplasia, cysts, calcification and edema. Some dogs showed "antralization". 相似文献