全文获取类型
收费全文 | 1700篇 |
免费 | 121篇 |
专业分类
林业 | 112篇 |
农学 | 48篇 |
基础科学 | 19篇 |
518篇 | |
综合类 | 67篇 |
农作物 | 103篇 |
水产渔业 | 204篇 |
畜牧兽医 | 568篇 |
园艺 | 47篇 |
植物保护 | 135篇 |
出版年
2023年 | 16篇 |
2022年 | 26篇 |
2021年 | 67篇 |
2020年 | 65篇 |
2019年 | 85篇 |
2018年 | 65篇 |
2017年 | 67篇 |
2016年 | 80篇 |
2015年 | 55篇 |
2014年 | 78篇 |
2013年 | 105篇 |
2012年 | 127篇 |
2011年 | 121篇 |
2010年 | 78篇 |
2009年 | 67篇 |
2008年 | 110篇 |
2007年 | 111篇 |
2006年 | 89篇 |
2005年 | 100篇 |
2004年 | 84篇 |
2003年 | 69篇 |
2002年 | 50篇 |
2001年 | 16篇 |
2000年 | 14篇 |
1999年 | 8篇 |
1998年 | 8篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 8篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1968年 | 2篇 |
1963年 | 1篇 |
1944年 | 1篇 |
1939年 | 1篇 |
排序方式: 共有1821条查询结果,搜索用时 15 毫秒
41.
Concepta McManus Helder Louvandini Rosilene Gugel Luiz Cláudio Bastos Sasaki Eliandra Bianchini Francisco Ernesto Moreno Bernal Samuel Rezende Paiva Tiago Prado Paim 《Tropical animal health and production》2011,43(1):121-126
The objective of this study was to evaluate and compare physical parameters in groups of sheep with different phenotypic characteristics
in the Centre-west region of Brazil. Five groups of sheep, with nine animals per group, were selected, three groups of Santa
Inês animals with different coat colours (white, brown and black), one group with crossbred animals (Santa Inês × Bergamasca)
and one group with animals of the Bergamasca breed. The following traits were evaluated: coat thickness, number and length
of hair, pigmentation level in the coat and the skin as well as the percentage area of sweats glands in the skin tissue, carried
out by histological analysis. The number of hairs and the area of sweats glands were not significantly different between the
evaluated groups. The Bergamasca breed showed low pigmentation of the skin and long hairs. The levels of pigmentation of the
hair and of the skin were highly correlated. Between the Santa Inês groups, the group with white hair showed the better parameters
for heat adaptation, while the brown hair group showed the lower heat adaptation when compared with another hair breed groups. 相似文献
42.
José Climent Maria Regina Chambel Marta Pardos Francisco Lario Pedro Villar-Salvador 《European Journal of Forest Research》2011,130(5):841-850
Rooting space is considered as a resource in plants, but comparative studies on the biomass allocation plasticity in response
to rooting volume (RV) are rare. We compared responses in growth, biomass allocation and ontogenetic heteroblasty in nine
hard pine species of contrasted ecology. Seedlings were cultivated in containers of 0.2, 0.5, 1.0, 2.8 and 7 L for two growing
seasons (425 days). Reduction in RV caused a reduction in plant absolute and relative growth rate and biomass allocated to
stems but it increased biomass allocated to roots. RV affected to a lesser extent and in a less consistent direction allocation
to leaves. Species that grew faster (higher relative growth rate) had a steeper decrease in growth with the reduction in RV.
Ontogenetic heteroblasty, evaluated as the proportion of secondary needles in the needle biomass, showed highly different
plasticity patterns in response to RV. Decrease in RV caused negligible or no change either in the most ontogenetically delayed
Mediterranean pines or in the most ontogenetically advanced pines, the mesic Pinus sylvestris and P. uncinata. By contrast, ontogenetically intermediate species showed steep reaction norms in response to reduction in RV. While P. pinaster and P. brutia showed marked rejuvenation, P. nigra accelerated the development of adult foliage. 相似文献
43.
Araújo CL Bezerra IW Oliveira AS Moura FT Macedo LL Gomes CE Barbosa AE Macedo FP Souza TM Franco OL Bloch-J C Sales MP 《Journal of agricultural and food chemistry》2005,53(11):4381-4387
A proteinaceous inhibitor with high activity against trypsin-like serine proteinases was purified from seeds of the tamarind tree (Tamarindus indica) by gel filtration on Shephacryl S-200 followed by a reverse-phase HPLC Vidac C18 TP. The inhibitor, called the tamarind trypsin inhibitor (TTI), showed a Mr of 21.42 kDa by mass spectrometry analysis. TTI was a noncompetitive inhibitor with a Ki value of 1.7 x 10(-9) M. In vitro bioinsecticidal activity against insect digestive enzymes from different orders showed that TTI had remarkable activity against enzymes from coleopteran, Anthonomus grandis (29.6%), Zabrotes subfasciatus (51.6%), Callosobruchus maculatus (86.7%), Rhyzopertha dominica(88.2%), and lepidopteron, Plodia interpuncptella (26.7%), Alabama argillacea (53.8%), and Spodoptera frugiperda (75.5%). Also, digestive enzymes from Diptera, Ceratitis capitata (fruit fly), were inhibited (52.9%). In vivo bioinsecticidal assays toward C. capitata and C. maculatus larvae were developed. The concentration of TTI (w/w) in the artificial seed necessary to cause 50% mortality (LD50) of larvae was 3.6%, and that to reduce mass larvae by 50.0% (ED50) was 3.2%. Furthermore, the mass C. capitata larvae were affected at 53.2% and produced approximately 34% mortality at a level of 4.0% (w/w) of TTI incorporated in artificial diets. 相似文献
44.
Torregrosa F Cortés C Esteve MJ Frígola A 《Journal of agricultural and food chemistry》2005,53(24):9519-9525
Liquid chromatography (LC) was the method of choice for quantification of carotenoids (including geometrical isomers) to evaluate the effects of high-intensity pulsed electric field (HIPEF), a nonthermal preservation method, with different parameters (electric field intensities and treatment times), on an orange-carrot juice mixture (80:20, v/v). In parallel, a conventional heat treatment (98 degrees C, 21 s) was applied to the juice. HIPEF processing generally caused a significant increase in the concentrations of the carotenoids identified as treatment time increased. HIPEF treatment at 25 and 30 kV/cm provided a vitamin A concentration higher than that found in the pasteurized juice. 相似文献
45.
Phosphatidylethanolamine (PE), phosphatidylcholine (PC), lysine (Lys), and mixtures of them were tested for antioxidative activity in refined olive oil by the Rancimat method to investigate the role of the chemical reactions produced in the Rancimat vessel on the induction periods (IPs) obtained. PE and Lys, but not PC, increased the IPs of the oil when tested alone. In addition, PE/Lys and PC/Lys mixtures, but not PC/PE mixtures, exhibited a synergistic effect. All these results can be understood considering the in situ formation of oxidized lipid/amino compound reaction products with antioxidative activities. Thus, the formation of pyrroles could be detected after derivatization with p-(dimethylamino)benzaldehyde, and some of these compounds could be unambiguously identified by GC-MS after their conversion into volatile derivatives. In addition, the formed products contributed to the color developed, and a correlation was observed between the Rancimat IPs obtained and the yellowness index of the oxidized oils recovered from the Rancimat. Furthermore, the differences observed in the antioxidative activities of PE, PC, Lys, and their mixtures could be explained according to the lipophility and hydrophility of the oxidized lipid/amino compound reaction products formed. All these results suggest that chemical reactions are being produced in the Rancimat vessel and the Rancimat IPs obtained are a consequence of the antioxidative activities of the products formed in these reactions. Furthermore, Rancimat may be a valuable tool for testing antioxidative activities of antioxidants produced during food processing if favorable conditions for antioxidant formation are employed. 相似文献
46.
Santaclara FJ Espiñeira M Cabado AG Aldasoro A Gonzalez-Lavín N Vieites JM 《Journal of agricultural and food chemistry》2006,54(22):8461-8470
Legislation regarding the labeling of processed products is an important issue in the protection of consumer rights. This labeling is especially important in products that cannot be identified on the basis of their morphological characters, because these are removed from the animal in the transformation process. The goal of this study was the identification of mussel species using Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) and Forensically Informative Nucleotide Sequencing (FINS) methodologies. The molecular marker selected was 18S rDNA (nuclear small-subunit rDNA gene), which allows identification at the genus level and at the species level in some cases. The genera included in this study were Mytilus, Perna, Aulacomya, Semimytilus, Brachidontes, Choromytilus, and Perumytilus. Different markers were used for genetic identification at the species level. To identify the species included in the genus Perna and Choromytilus, a fragment of ITS 1 (Internal Transcribed Spacer 1) was amplified by multiplex PCR and digested with restrictases. The species of Mytilus were identified by length polymorphism and RFLP of the polyphenolic adhesive protein gene. This methodology was validated with products manufactured in the authors' pilot plant and applied to commercial samples. Therefore, this sequential method can be completely or partially used to determine the mussel genus or species present in any food product. 相似文献
47.
Sotelo A Argote RM Moreno RI Flores NI Diaz M 《Journal of agricultural and food chemistry》2003,51(9):2821-2825
The nutritive and toxicological values of the dry seeds, germinated seeds, and string beans of Erythrina americana were studied using raw and boiled samples. Raw germinated seeds had a higher protein content and lower fiber content than dry seeds. The whole string bean had lower protein content and higher fiber content. However, the seeds of the green pod showed the same protein concentration as the dry seeds (dry basis). Boiling and elimination of broth was beneficial in diminishing the alkaloid concentration in all the samples. The trypsin inhibitors, lectins, and tannins were also diminished as was expected. The raw string bean showed the lowest LD(50). Although the total essential amino acids content of the boiled germinated seeds was increased, the quality of protein, protein efficiency ratio (PER), was lower than in boiled dry seeds, and in these, the PER was similar to the control (casein). The present results suggest that for the protein quality and low alkaloid content, the boiled dry seeds and string beans could be used for animal feeding. It could be interesting to test the raw string beans in ruminants since in this stage E. americana showed the lowest toxicity. 相似文献
48.
Siani AC Tappin MR Ramos MF Mazzei JL Ramos MC De Aquino Neto FR Frighetto N 《Journal of agricultural and food chemistry》2002,50(12):3518-3521
A new chemotype of the aromatic Verbenaceae species Lippia alba Mill. N. E. Br. from southeastern Brazil has recently been shown to have a high content of linalool in the leaf essential oil. Vegetative propagation of this chemotype was conducted at six different locations in Brazil, and the variation of the content and the optical purity of linalool in the oils were verified. Yields (0.6-0.9%, hydrodistillation), chemical composition, linalool content, and optical purity of the oils from all the plants were compared, using GC-FID, GC-MS, chiral chromatography, and retention index calculation. No plant exceeded the matrix in linalool content (46.5 to 90.7%), and the chemical profile of the oils was the same for all the samples. Purification of linalool to a content close to 100% was effected by vacuum distillation of the crude oil. Chiral analysis showed exclusively the presence of S-linalool in all the crude oils and in the distilled samples. 相似文献
49.
Urolithins, ellagic acid-derived metabolites produced by human colonic microflora, exhibit estrogenic and antiestrogenic activities 总被引:2,自引:0,他引:2
Larrosa M González-Sarrías A García-Conesa MT Tomás-Barberán FA Espín JC 《Journal of agricultural and food chemistry》2006,54(5):1611-1620
Urolithins A and B (hydroxy-6H-dibenzo[b,d]pyran-6-one derivatives) are colonic microflora metabolites recently proposed as biomarkers of human exposure to dietary ellagic acid derivatives. Molecular models suggest that urolithins could display estrogenic and/or antiestrogenic activity. To this purpose, both urolithins and other known phytoestrogens (genistein, daidzein, resveratrol, and enterolactone) were assayed to evaluate the capacity to induce cell proliferation on the estrogen-sensitive human breast cancer MCF-7 cells as well as the ability to bind to alpha- and beta-estrogen receptors. Both urolithins A and B showed estrogenic activity in a dose-dependent manner even at high concentrations (40 microM), without antiproliferative or toxic effects, whereas the other phytoestrogens inhibited cell proliferation at high concentrations. Overall, urolithins showed weaker estrogenic activity than the other phytoestrogens. However, both urolithins displayed slightly higher antiestrogenic activity (antagonized the growth promotion effect of 17-beta-estradiol in a dose-dependent manner) than the other phytoestrogens. The IC(50) values for the ERalpha and ERbeta binding assays were 0.4 and 0.75 microM for urolithin A; 20 and 11 microM for urolithin B; 3 and 0.02 for genistein; and 2.3 and 1 for daidzein, respectively; no binding was detected for resveratrol and enterolactone. Urolithins A and B entered into MCF-7 cells and were metabolized to yield mainly urolithin-sulfate derivatives. These results, together with previous studies regarding absorption and metabolism of dietary ellagitannins and ellagic acid in humans, suggest that the gut microflora metabolites urolithins are potential endocrine-disrupting molecules, which could resemble other described "enterophytoestrogens" (microflora-derived metabolites with estrogenic/antiestrogenic activity). Further research is warranted to evaluate the possible role of ellagitannins and ellagic acid as dietary "pro-phytoestrogens". 相似文献
50.
Cortés C Torregrosa F Esteve MJ Frígola A 《Journal of agricultural and food chemistry》2006,54(17):6247-6254
A comparative study was made of the evolution and modification of various carotenoids and vitamin A in untreated orange juice, pasteurized orange juice (90 degrees C, 20 s), and orange juice processed with high-intensity pulsed electric fields (HIPEF) (30 kV/cm, 100 micros), during 7 weeks of storage at 2 and 10 degrees C. The concentration of total carotenoids in the untreated juice decreased by 12.6% when the juice was pasteurized, whereas the decrease was only 6.7% when the juice was treated with HIPEF. Vitamin A was greatest in the untreated orange juice, followed by orange juice treated with HIPEF (decrease of 7.52%) and, last, pasteurized orange juice (decrease of 15.62%). The decrease in the concentrations of total carotenoids and vitamin A during storage in refrigeration was greater in the untreated orange juice and the pasteurized juice than in the juice treated with HIPEF. During storage at 10 degrees C, auroxanthin formed in the untreated juice and in the juice treated with HIPEF. This carotenoid is a degradation product of violaxanthin. The concentration of antheraxanthin decreased during storage, and it was converted into mutatoxanthin, except in the untreated and pasteurized orange juices stored at 2 degrees C. 相似文献