全文获取类型
收费全文 | 3605篇 |
免费 | 356篇 |
国内免费 | 180篇 |
专业分类
林业 | 113篇 |
农学 | 178篇 |
基础科学 | 16篇 |
625篇 | |
综合类 | 824篇 |
农作物 | 400篇 |
水产渔业 | 762篇 |
畜牧兽医 | 1030篇 |
园艺 | 119篇 |
植物保护 | 74篇 |
出版年
2024年 | 38篇 |
2023年 | 34篇 |
2022年 | 108篇 |
2021年 | 150篇 |
2020年 | 124篇 |
2019年 | 174篇 |
2018年 | 138篇 |
2017年 | 205篇 |
2016年 | 170篇 |
2015年 | 141篇 |
2014年 | 158篇 |
2013年 | 308篇 |
2012年 | 248篇 |
2011年 | 240篇 |
2010年 | 175篇 |
2009年 | 186篇 |
2008年 | 166篇 |
2007年 | 196篇 |
2006年 | 150篇 |
2005年 | 105篇 |
2004年 | 102篇 |
2003年 | 99篇 |
2002年 | 70篇 |
2001年 | 80篇 |
2000年 | 68篇 |
1999年 | 62篇 |
1998年 | 49篇 |
1997年 | 50篇 |
1996年 | 50篇 |
1995年 | 40篇 |
1994年 | 36篇 |
1993年 | 46篇 |
1992年 | 27篇 |
1991年 | 18篇 |
1990年 | 25篇 |
1989年 | 28篇 |
1988年 | 15篇 |
1987年 | 24篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 7篇 |
1983年 | 2篇 |
1981年 | 4篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1973年 | 5篇 |
1956年 | 2篇 |
1955年 | 4篇 |
排序方式: 共有4141条查询结果,搜索用时 0 毫秒
1.
RICHARD G. HARVEY 《Veterinary dermatology》1993,4(4):175-179
Abstract— The physiology of essential fatty acid metabolism in the cat is reviewed. Emphasis is placed on those aspects of the n:6 and n:3 fatty acids, their metabolites and interactions, which relate primarily to the skin. The functional roles, if known, of the fatty acids are discussed. Recent clinical research into the use of essential fatty acid supplements in the management of feline dermatoses is presented. Current indications for the therapeutic supplementation with essential fatty acids are summarised. 相似文献
2.
D. Roy Davies 《Euphytica》1976,25(1):717-724
Summary A cellulose acetate electrophoretic technique has been used to characterise the storage proteins present in pea seeds in order to try and determine the proportions of proteins present which are enriched in sulphur amino-acids. Some of the eight varieties examined were shown to differ in their proportions of the various storage proteins. When the proteins were separated and estimated quantitatively and also characterised by their sub-unit composition, it was shown that cellulose acetate electrophoresis of crude protein extracts or of whole globulins did not give the degree of resolution required. The procedures which have to be undertaken in order to obtain this information are considered, and the difficulties of incorporating them into a plant breeding programme discussed. 相似文献
3.
Characteristically the metabolism of microbial nitrogen (N) compounds in ruminants involves the degradation of dietary N and synthesis of microbial protein (MP), compounds including a small amount of peptides and free amino acids, which may account for 75–85% of total N and the remainder are nucleic acids (NA: DNA and RNA). Generally rumen microbes contain 10–25% NA‐N of the total N while 70–80% is in the form of RNA. This paper describes the degradation and synthesis of NA in the rumen and their fate in the lower digestive tracts. Their physiological and nutritional significance in different types of ruminant animals is also discussed. The research works on NA metabolism in ruminants has been mainly on metabolism of purines after rumen microbial digestion and absorption in the lower gut. Subsequently, the fate of absorbed purines has been intensively investigated to assess the extent of MP synthesis in the rumen. The method for predicting ruminal synthesized MP and subsequently digested MP has been proposed using urinary purine derivative (PD) excretion in sheep and cattle fed on ordinary feed. The latter approach has now been adopted for calculation of protein supply in some feeding standards, although there are still difficulties in predicting representative samples of rumen microbes, and also uncertainties in variations of non‐renal and endogenous purine losses. 相似文献
4.
Teck-Chwen LOH Fang-Ling LAW Yong-Meng GOH Hooi-Ling FOO Idrus ZULKIFLI 《Animal Science Journal》2009,80(1):27-33
This study was conducted to investigate the effects of feeding fermented fish (FF) to layers on laying performance, and polyunsaturated fatty acid and cholesterol levels in eggs and plasma. A total of 96, 13-week-old Babcock B380 pullets were used in this study. They were randomly assigned to four numerically equal groups with eight replicates per treatment, three birds per replicate. All the birds were housed in individual cages. The dietary treatments were: Control diet, without FF; FF3 diet containing 3% (w/w) FF, FF6 diet containing 6% (w/w) FF and FF9 diet containing 9% (w/w) FF. The study was carried out for 16 weeks inclusive of two weeks of adjustment. Weekly feed intake and egg production were recorded. Blood plasma cholesterol and fatty acid profiles were assayed at the end of the experiment. FF did not enhance ( P > 0.05) egg mass but ( P < 0.05) decreased egg weight slightly. However, egg yolk cholesterol and plasma cholesterol concentrations were reduced ( P < 0.05) by FF. The n-6:n-3 fatty acids ratio in the egg yolk (Control = 7.9, FF9 = 6.2) and plasma (Control = 10.6, FF9 = 6.2) were decreased by feeding FF. Moreover, FF was able to increase ( P < 0.05) the docosahexaenoic acid (DHA) concentrations in egg yolk and plasma. In conclusion, this study demonstrated that FF increased DHA and reduced egg yolk cholesterol in poultry eggs. 相似文献
5.
Kirsten Büsing Mohamed Elhensheri Kristin Entzian Udo Meyer Annette Zeyner 《Research in veterinary science》2014
Humic acids are used to prophylactically treat intestinal diseases in a wide number of species, yet the mechanism of action remains unknown. The general assumption has been that humic acids act locally; however studies using young piglets show orally supplemented humic acids can penetrate the intestinal wall, and thus potentially act systemically. The objective of this study was to determine if humic acids could also cross the intestinal barrier in adult pigs and be detected in other organs. Adult minipigs (>18 months old) orally received either 1 g humic acids/kg body weight (verum, n = 3) or placebo (control, n = 3), for 2 weeks. At the end of the feeding period tissue samples were harvested from the intestine, various glands and organs. Unstained tissue samples were examined by light microscopy for the presence of humic acid particles. No humic acid particles were detected in any of the unstained tissues from verum or control pigs. 相似文献
6.
Arai T. Hashimoto K. Muzutani H. Kawabata T. Sako T. Washizu T. 《Veterinary research communications》1999,23(4):203-209
The plasma concentrations of fructose, glucose, free fatty acids (FFA) and triglycerides (TG) were measured in dogs and cats. Changes in these concentrations were investigated in dogs by an intravenous fructose tolerance test (IVFTT) at a dose of 0.1 g/kg body weight. Fructose concentrations in the plasma of dogs were significantly higher than those of cats. There was no significant difference in plasma glucose concentrations between dogs and cats. Plasma FFA concentrations decreased and TG concentrations increased after feeding in both dogs and cats. During the IVFTT, the plasma fructose concentrations in the dogs increased rapidly to a peak by 2 min and then decreased to half of the peak by 5 min after the administration of fructose. Administration of fructose resulted in an increase in the plasma TG concentrations and reduced plasma FFA concentrations in the dogs. Only 4% of the administered fructose was detected in the urine of dogs following IVFTT. Plasma fructose was considered to be rapidly absorbed and metabolized in both dogs and cats. However, as with glucose metabolism, there appear to be some differences in fructose metabolism between dogs and cats. 相似文献
7.
用排空强饲法对粉浆蛋白粉的常规成分、代谢能及氨基酸利用率进行了测定。结果表明:粉浆蛋白粉干物质中含有粗蛋白质78.4%;代谢能为15.86MJ/kg;赖氨酸5.03%;蛋氨酸0.39%;胱氨酸1.30%;异亮氨酸3.25%;亮氨酸6.92%;精氨酸6.68%:酪氨酸2.34%;苯丙氨酸3.78%:组氨酸1.75%。这些必需氨基酸利用率分别为:92.0%、81.7%、85.2%、90.2%、92.9%、92.4%、90.5%、90.5%和92.1%。其氨基酸利用率介于豆饼与鱼粉之间,是一种值得开发的蛋白质饲料资源。 相似文献
8.
G. Benzoni F. Foresti I. L. Archetti G. Coceva A. Guyonvarch L. Alborali 《Journal of animal physiology and animal nutrition》2013,97(5):996-1005
The transfer of passive immunity from sows to piglets is important and it is the first immune protection of the new born piglet. Improving sows immunity by adding immuno‐stimulating product in sows diet can positively affect colostrum composition and transfer of immune molecules to piglets. The aim of the current study is to evaluate the benefit of a different solution, made of specific fatty acids from marine origin that have been used in human medicine for decades, for sows and piglets. Two trials were conducted in commercial farm, involving 240 sows at different periods of the year. Sows were divided in a control group, without supplementation, and a test group, supplemented with the feed additive from the 90th day of gestation to weaning. Sows body condition, piglets viability and growth were recorded. Milk immunoglobulin content was measured, as well as Aujeszky antibodies in sows and piglets blood as marker of specific immunity, and blood bactericidal activity, complement activity and lysozyme as markers of non specific immunity. No effect of the product was observed on piglets zootechnical criteria and specific immunity parameters but significant improvement of piglet non specific immunity, was observed. No difference was observed neither in the piglets blood PRRSV and PCV2 antibodies and viruses nor in Aujeszky antibodies. Blood complement activity seems to be an accurate indicator of immuno‐stimulating additive efficiency. Giving alkyl‐glycerol fatty acids to sows in late gestation and lactation can improve the passive immunity transfer to piglets. 相似文献
9.
以甘肃天祝地区3个牧场所产的白牦牛乳为研究对象,采用气相色谱-质谱联用检测方法,测定3个牧场所产白牦牛乳中脂肪酸含量,比较在枯草期、枯草末期、返青期、青草期4个时期及不同胎次的白牦牛所产牦牛乳中脂肪酸的构成及含量.结果表明:3个牧场白牦牛乳中乳脂肪酸含量差异不显著(P>0.05);1~5胎次母白牦牛乳中脂肪酸含量差异不显著(P>0.05).枯草期、枯草末期、返青期、青草期4个时期白牦牛乳中饱和脂肪酸(SFA)、不饱和脂肪酸(USFA)含量比值分别为1.86、1.75、1.62、1.32.随着气温的升高及牧草的成熟,白牦牛乳中饱和脂肪酸含量逐渐降低,而不饱和脂肪酸的含量逐渐升高. 相似文献
10.
Monika Sobczuk-Szul Magdalena Mochol Zenon Nogalski Paulina Pogorzelska-Przybyłek 《Animal Science Journal》2021,92(1):e13516
This study was designed to compare the fatty acid profiles of four types of fat depots from bulls, steers, and heifers. All animals were Polish Holstein-Friesian and Limousin crossbreds fattened semi-intensively—silage at libitum and concentrate in the amount corresponding to 30% of their net energy requirements. The fatty acid profile in intramuscular, intermuscular, and external and internal fat was determined. The intramuscular fat of bulls was most abundant in total PUFAs and n-6 PUFAs, and functional fatty acids C 18:2, C 20:4, and C 22:5 in comparison with steers and heifers. Regardless of sex category, intramuscular and external fat were characterized by higher levels of UFAs and a more desirable MUFA/SFA ratio than the remaining fat types. It should also be noted that external fat was more abundant in CLA than other fat types, and that the highest CLA content was found in bull fat, compared with the remaining sex categories of cattle. 相似文献