全文获取类型
收费全文 | 4039篇 |
免费 | 203篇 |
国内免费 | 2篇 |
专业分类
林业 | 285篇 |
农学 | 150篇 |
基础科学 | 14篇 |
1060篇 | |
综合类 | 196篇 |
农作物 | 323篇 |
水产渔业 | 440篇 |
畜牧兽医 | 1386篇 |
园艺 | 85篇 |
植物保护 | 305篇 |
出版年
2024年 | 2篇 |
2023年 | 38篇 |
2022年 | 76篇 |
2021年 | 171篇 |
2020年 | 161篇 |
2019年 | 205篇 |
2018年 | 157篇 |
2017年 | 168篇 |
2016年 | 156篇 |
2015年 | 124篇 |
2014年 | 184篇 |
2013年 | 270篇 |
2012年 | 331篇 |
2011年 | 318篇 |
2010年 | 190篇 |
2009年 | 164篇 |
2008年 | 271篇 |
2007年 | 284篇 |
2006年 | 186篇 |
2005年 | 157篇 |
2004年 | 140篇 |
2003年 | 131篇 |
2002年 | 131篇 |
2001年 | 21篇 |
2000年 | 20篇 |
1999年 | 19篇 |
1998年 | 14篇 |
1997年 | 13篇 |
1996年 | 10篇 |
1995年 | 10篇 |
1994年 | 11篇 |
1993年 | 9篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 10篇 |
1989年 | 11篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 10篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1980年 | 3篇 |
1977年 | 3篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1969年 | 3篇 |
1966年 | 4篇 |
1955年 | 2篇 |
排序方式: 共有4244条查询结果,搜索用时 15 毫秒
991.
Thaís Castelo-Branco Maria Madalena Pessoa Guerra Roberta Soares Silvio Peixoto 《Aquaculture International》2018,26(3):913-920
Vitrification is a fast freezing method with promising results for penaeids sperm cryopreservation. This study evaluated the efficiency of three cryoprotectant solutions for sperm vitrification and artificial insemination with cryopreserved spermatophores of Litopenaeus vannamei. The cryoprotectant solutions tested were 30% methanol, 2% soy lecithin, and 30% methanol?+?2% soy lecithin. Fully mature females were artificially inseminated with vitrified and fresh spermatophores as a control group. The vitrification method was efficient in maintaining high rates of sperm survival and membrane integrity. Although the egg fertilization was successfully attained by artificial insemination with cryopreserved spermatophores, low hatching rates suggested that possible DNA fragmentation of sperm cells should be further investigated. This is the first report of artificial insemination using vitrified sperm in penaeids. 相似文献
992.
Zalacain A Ordoudi SA Díaz-Plaza EM Carmona M Blázquez I Tsimidou MZ Alonso GL 《Journal of agricultural and food chemistry》2005,53(24):9337-9341
Near-infrared reflectance spectroscopy has been applied for the first time to saffron spice to determine the chemical composition and geographical origin of 111 samples from the there main producers' countries: Iran, Greece, and Spain. The validation procedures with the results obtained by UV-vis and HPLC-DAD measurements demonstrated that this technique is appropriate to determine the following parameters: moisture and volatile content, coloring strength, (250 nm), and (330 nm), established on the ISO 3632 Technical Specification Normative and used to certify saffron quality in the international market. Also, it can be used to estimate the content of the five main crocetin glycosides, the compounds responsible for saffron color, the best correlations being for trans-crocetin di-(beta-D-gentibiosyl) ester (R2= 0.93), trans-crocetin (beta-D-glucosyl)-(beta-D-gentibiosyl) (R2= 0.94), and picrocrocin (R2= 0.92), the compound accepted as responsible for saffron bitterness. Finally, a discriminant analysis among the three geographical origins reveals that Iranian samples are the most different, whereas Greek and Spanish samples are more similar. All of these results reveal that NIRS spectroscopy has an enormous potential for its application to saffron quality control as the results are obtained in 2 min and without any sample manipulation. 相似文献
993.
Lídia M Matsubara MV MSc Valéria N L S Oliva† MV PhD Daniela T Gabas MV MSc Guillermo C V Oliveira MV & Maria L Cassetari‡ MSc 《Veterinary anaesthesia and analgesia》2009,36(5):407-413
Objective To investigate the effects of a low-dose constant rate infusion (LCRI; 50 μg kg−1 minute−1 ) and high-dose CRI (HCRI; 200 μg kg−1 minute−1 ) lidocaine on arterial blood pressure and on the minimum alveolar concentration (MAC) of sevoflurane (Sevo), in dogs.
Study design Prospective, randomized experimental design.
Animals Eight healthy adult spayed female dogs, weighing 16.0 ± 2.1 kg.
Methods Each dog was anesthetized with sevoflurane in oxygen and mechanically ventilated, on three separate occasions 7 days apart. Following a 40-minute equilibration period, a 0.1-mL kg−1 saline loading dose or lidocaine (2 mg kg−1 intravenously) was administered over 3 minutes, followed by saline CRI or lidocaine LCRI or HCRI. The sevoflurane MAC was determined using a tail clamp. Heart rate (HR), blood pressure and plasma concentration of lidocaine were measured. All values are expressed as mean ± SD.
Results The MAC of Sevo was 2.30 ± 0.19%. The LCRI reduced MAC by 15% to 1.95 ± 0.23% and HCRI by 37% to 1.45 ± 0.21%. Diastolic and mean pressure increased with HCRI. Lidocaine plasma concentration was 0.84 ± 0.18 for LCRI and 1.89 ± 0.37 μg mL−1 for HCRI. Seventy-five percent of HCRI dogs vomited during recovery.
Conclusion and clinical relevance Lidocaine infusions dose dependently decreased the MAC of Sevo, did not induce clinically significant changes in HR or arterial blood pressure, but vomiting was common during recovery in HCRI. 相似文献
Study design Prospective, randomized experimental design.
Animals Eight healthy adult spayed female dogs, weighing 16.0 ± 2.1 kg.
Methods Each dog was anesthetized with sevoflurane in oxygen and mechanically ventilated, on three separate occasions 7 days apart. Following a 40-minute equilibration period, a 0.1-mL kg
Results The MAC of Sevo was 2.30 ± 0.19%. The LCRI reduced MAC by 15% to 1.95 ± 0.23% and HCRI by 37% to 1.45 ± 0.21%. Diastolic and mean pressure increased with HCRI. Lidocaine plasma concentration was 0.84 ± 0.18 for LCRI and 1.89 ± 0.37 μg mL
Conclusion and clinical relevance Lidocaine infusions dose dependently decreased the MAC of Sevo, did not induce clinically significant changes in HR or arterial blood pressure, but vomiting was common during recovery in HCRI. 相似文献
994.
Ferrini AM Mannoni V Carpico G Pellegrini GE 《Journal of agricultural and food chemistry》2008,56(3):784-788
A novel application of a hybrid biosensor is here employed as an analytical method for the detection and presumptive identification of beta-lactam residues in milk. The method is based on measurements of carbon dioxide (CO2), the production of which is related to the microbial growth of the test microorganism Bacillus stearothermophilus var. calidolactis. The presence of beta-lactams in milk inhibits microbial growth and, consequently, the CO2 production rate. The analysis is based on the variation of CO2 between a milk sample spiked with beta-lactams and a twin milk sample containing beta-lactams plus a broad spectrum beta-lactamase, using an electrochemical device of biosensor. A blank milk sample is included as control. The result is obtained starting from the first 120 min. Moreover, the ability to recognize all of the beta-lactams speeds the total time of analysis when chemical identification and quantification are required. The analytical method appears to be adequate for milk control for qualitative screening purposes, complying with the requirements stated in Decision 2002/657/EC. 相似文献
995.
Mohammad T. Ridha Md Arshad Hossain Ismail S. Azad Maria Saburova 《Aquaculture Research》2020,51(10):4225-4237
This study compared the effect of three sources of carbohydrates: sugar, wheat and malt flours, on water quality, water consumption, bacterial load, growth and flesh quality of Nile tilapia. Adults (120.6 ± 0.64 g) were stocked in 1.2‐m3 fibreglass tanks at a rate of 25 fish/m3. Carbohydrates were added to the biofloc tanks at a C:N ratio of 20:1. Water flow in the non‐biofloc control tanks was adjusted to 0.6 L/day. The 105‐day experiment was conducted in triplicates. Results showed that biofloc treatments (BFT) with zero water exchange had significantly higher mean total ammonia, nitrites, nitrates, alkalinity, total suspended solids and lower pH than the control treatment. The sugar BFT had the highest floc volume. Growth parameters and feed conversion ratio did not differ significantly among treatments. However, tilapia in the malt flour and control treatments had close values. Gross fish yield was higher (p < .05) in the control than the BFT treatments. Water consumption/kg tilapia produced in the control was 42 times higher than the BFT groups. Protozoa dominated the biofloc biota, and wheat flour was the best in harbouring higher bacterial populations in the gut. Protein content and ∑n‐3 fatty acids were highest in the wheat flour biofloc, while malt flour biofloc had the highest lipids. The sugar biofloc had the highest n‐3/n‐6 ratio. Tilapia muscles in the malt flour and control treatments had the highest protein and lipid contents respectively. Tilapia muscles in the wheat flour BFT had the highest ∑n‐3 fatty acids and n‐3/n‐6 ratio. It can be concluded that farming tilapia in BFT using malt or wheat flours as carbon sources is more economical in saving great amount of water with minimal discharge of pollutants without affecting tilapia growth or flesh quality. 相似文献
996.
Anna Maria Bencze?R?r?Email author Bente?Ruyter Jon?Skorve Rolf?K.?Berge Karl-Erik?Slinning 《Aquaculture International》2005,13(3):217-231
Atlantic salmon (Salmo salar) was grown in sea cages from 700 g to a market size of 3.2 kg on diets containing either 29% Peruvian high polyunsaturated fatty acids (PUFA) fish oil (FO) or 29% soybean oil (SO) as oil source. Chemical analyses and a triangular consumer test were performed on fresh muscle, while colour, texture and liquid holding capacity (LHC) analyses were performed on both fresh muscle, frozen muscle (stored for 3 months) and smoked salmon. The growth and chemical composition of flesh was not affected by the dietary treatment. The muscle fatty acid (FA) profile was reflected by the dietary oil source, and the amount of malondialdehyde (MDA) was threefold higher in the salmon fed FO than SO. Muscle pigment concentration was significantly different (p < 0.01) with 7.9 mg kg–1 for FO and 5.6 mg kg–1 for SO fed salmon, respectively. This result was also significantly (p < 0.05) reflected in the difference between the instrumentally measured colour of fresh, frozen and smoked muscle, and visual impressions of fresh and frozen muscle. Gaping, texture and liquid holding capacity was not affected by the dietary treatment, and the consumer panel did not detect any differences between the dietary groups. SO can be used as a dietary oil source in the grow-out phase of salmon production without sacrificing product quality in terms of texture, liquid holding capacity and consumer preference. However, a total substitution of high PUFA fish oil by SO in diets for salmon grown to market size, affects muscle colour and the FA profile significantly. (p < 0.05). 相似文献
997.
998.
Marta De Biaggi Dario Donno Maria Gabriella Mellano Isidoro Riondato Ernest N. Rakotoniaina Gabriele L. Beccaro 《Plant foods for human nutrition (Dordrecht, Netherlands)》2018,73(2):89-94
Interest in new sources of anti-inflammatory and antioxidant compounds has recently become a major research issue, with the cornelian cherry (Cornus mas L.) receiving particular attention for its significant amounts of phenolic compounds and vitamins, which exhibit a wide range of biological and pharmacological properties. This study was aimed at increasing knowledge regarding the cornelian cherry in Italy through the analysis of biologically active substances in the locally available genotype “Chieri”. Spectrophotometric methods were applied to evaluate antioxidant activity, total anthocyanin content and total polyphenolic content. Identification and quantification of the main phytochemical compounds (polyphenols, monoterpenes, organic acids and vitamin C) was performed via high performance liquid chromatography coupled to a diode array detector. C. mas extracts showed high levels of total soluble solids and low acidity. High amounts of phenolic secondary metabolites were observed, with particular reference to anthocyanins (134.71 mgC3G/100 gFW), which confer remarkable nutraceutical properties to the analysed samples. These results highlight the potential of C. mas fruits as a good source of natural antioxidants, suggesting their use as a functional food. Future studies should focus on identifying other specific phytochemical compounds and the genetic traits of local varieties in order to improve cornelian cherry cultivars for food and medicine production. 相似文献
999.
da Silva Fialho L Guimarães VM de Barros EG Moreira MA Dos Santos Dias LA de Almeida Oliveira MG José IC de Rezende ST 《Plant foods for human nutrition (Dordrecht, Netherlands)》2006,61(2):87-89
Common beans have a high nutritional value, but contain galactooligosaccharides (GO), which cause flatulence and intestinal discomfort in humans. The biochemical composition of ten bean cultivars was determined to select those of high protein and low GO contents. The cultivars varied in carbohydrate (47.02-60.17%), GO (3.12-5.71%), protein (22.17-33.50%), lipid (1.13-1.81%), moisture (11.42-12.93%) and ash contents (4.08-5.61%). 'Mexico 222' presented the highest alpha-galactosidase activity. Protein and GO contents were positively correlated. 'Perry Marrow' combined high protein and low GO concentrations, indicating it can be used in improvement programs aiming at high-quality cultivars for human consumption. 相似文献
1000.
Tsiailanis Antonios D. Chatzigiannis Christos M. Papaemmanouil Christina D. Chatziathanasiadou Maria V. Chaloulos Panagiotis Riba Isabel Mullard Graham Wiczkowski Wiesław Koutinas Apostolos Mandala Ioanna Tzakos Andreas G. 《Plant foods for human nutrition (Dordrecht, Netherlands)》2022,77(2):198-205
Plant Foods for Human Nutrition - Replacing synthetic dyes with natural pigments has gained great attention over the past years in the food industry, due to the increased alertness of consumers for... 相似文献