全文获取类型
收费全文 | 501篇 |
免费 | 32篇 |
专业分类
林业 | 68篇 |
农学 | 15篇 |
101篇 | |
综合类 | 21篇 |
农作物 | 39篇 |
水产渔业 | 29篇 |
畜牧兽医 | 185篇 |
园艺 | 21篇 |
植物保护 | 54篇 |
出版年
2023年 | 3篇 |
2021年 | 5篇 |
2020年 | 6篇 |
2019年 | 8篇 |
2018年 | 38篇 |
2017年 | 22篇 |
2016年 | 33篇 |
2015年 | 15篇 |
2014年 | 26篇 |
2013年 | 24篇 |
2012年 | 35篇 |
2011年 | 50篇 |
2010年 | 20篇 |
2009年 | 16篇 |
2008年 | 26篇 |
2007年 | 28篇 |
2006年 | 27篇 |
2005年 | 26篇 |
2004年 | 14篇 |
2003年 | 18篇 |
2002年 | 15篇 |
2001年 | 8篇 |
2000年 | 9篇 |
1999年 | 7篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1993年 | 3篇 |
1990年 | 2篇 |
1987年 | 2篇 |
1985年 | 3篇 |
1980年 | 2篇 |
1977年 | 2篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1970年 | 2篇 |
1969年 | 2篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1966年 | 2篇 |
1965年 | 2篇 |
1963年 | 2篇 |
1958年 | 1篇 |
1957年 | 1篇 |
1956年 | 1篇 |
1932年 | 1篇 |
1926年 | 2篇 |
1918年 | 2篇 |
排序方式: 共有533条查询结果,搜索用时 15 毫秒
511.
Cerný D Lekić N Váňová K Muchová L Hořínek A Kmoníčková E Zídek Z Kameníková L Farghali H 《Fitoterapia》2011,82(5):786-791
This work studied a relationship between HO-1/CO system and lipid peroxidation with consequent effects on liver functions and NOS-2. We focused on curcumin pretreatment in rat toxic model of d-galactosamine and lipopolysaccharide. Hepatocyte viability, lipid peroxidation, antioxidant status, ALT and AST were evaluated. HO-1 and NOS-2 expressions and respective enzyme activity were determined. Curcumin caused decreases in ALT and AST levels as well as in lipid peroxidation. Furthermore, curcumin pretreatment increased liver HO-1 (2.4-fold, p = 0.001), but reduced NOS-2 (4.1-fold, p = 0.01) expressions. In conclusion, the tuning of CO/NO pathways is important in shedding light on curcumin's cytoprotective effects in this model. 相似文献
512.
Essential oil, isolated by hydrodistillation from Chenopodium botrys aerial parts, expressed significant bactericidal and fungicidal activity against selected strains of microorganisms. 相似文献
513.
The antioxidative potential of Achillea alexandri-regis has been studied by measuring the influence of herb extracts on hydroxyl and superoxide radicals' quantity in different in vitro systems. The ethyl acetate extract exhibited hydroxyl radical scavenging activity in all tested biological system (liver homogenate, hemolyzed blood, serum and postmitochondrial liver fraction), whereas butanol extract reduced hydroxyl radicals significantly only in the postmitochondrial liver fraction. Both extracts showed superoxide radical scavenging effect only in hemolyzed blood. 相似文献
514.
Kodama K Takigawa M Horvatić M Berthier C Kageyama H Ueda Y Miyahara S Becca F Mila F 《Science (New York, N.Y.)》2002,298(5592):395-399
We report the observation of magnetic superstructure in a magnetization plateau state of SrCu2(BO3)2, a frustrated quasi-two-dimensional quantum spin system. The Cu and B nuclear magnetic resonance (NMR) spectra at 35 millikelvin indicate an apparently discontinuous phase transition from uniform magnetization to a modulated superstructure near 27 tesla, above which a magnetization plateau at 1/8 of the full saturation has been observed. Comparison of the Cu NMR spectrum and the theoretical analysis of a Heisenberg spin model demonstrates the crystallization of itinerant triplets in the plateau phase within a large rhomboid unit cell (16 spins per layer) showing oscillations of the spin polarization. Thus, we are now in possession of an interesting model system to study a localization transition of strongly interacting quantum particles. 相似文献
515.
Dr B. O. Eggum J. Dumanović D. Misević M. Denić 《Plant foods for human nutrition (Dordrecht, Netherlands)》1985,35(2):165-174
Grain yield, chemical composition, protein quality and digestible energy were measured for 18 maize varieties (opaque-2, high oil, waxy hybrids, normal hybrids) cultivated in Yugoslavia. Protein quality assessment was based on amino acid composition, and true protein digestibility, biological value, net protein utilization and utilizable protein as determined in nitrogen balance experiments with rats. The protein concentration in dry matter varied from 8.63–18.81% while the fat concentration varied from 4.45–16.13%. There were only minor differences in ash and crude fibre, while starch and sugar varied inversely to fat and protein concentration. Lysine levels were approximately 30% higher for the opaque-2 varieties compared with normal maize, while leucine levels were about 30% lower. Yields were extremely high for all varieties with the highest value being 10.3 tonnes/ha. Due to the high yields, protein production/ha was high in range of 822–977 kg. This resulted in high yields of amino acids/ha. Protein utilization was very high in the opaque-2 varieties, which had the highest lysine contents. The biological values were close to 80 in these varieties, whereas they were only 60–65 in the normal maize varieties. 相似文献
516.
Bošković-Rakočević Ljiljana Milivojević Jelena Milošević Tomo Paunović Gorica 《Water, air, and soil pollution》2014,225(11):1-13
There are multiple stressors derived from urbanizations that result in frequent disturbances on streams and rivers reducing water quality and threatens aquatic biota. P-glycoprotein (P-gp)-mediated multixenobiotic resistance (MXR) is a defence mechanism analogous to multidrug resistance (MDR), which has been demonstrated in several aquatic organisms. This system protects cells against the entry and the accumulation of xenobiotics and has been proposed as a biomarker for pollution assessment. We conducted a study in a post-urban reach of Esquel stream (Chubut Province) downstream a wastewater treatment plant, in order to assess the presence and activity of MXR in five freshwater macroinvertebrate species (Helobdella michaelseni, Helobdella simplex, Patagoniobdella variabilis, Hyalella curvispina and Chironomus riparius). We measured the accumulation of the model P-gp substrate rhodamine B (RB) in organisms previously exposed to pollution. Our results described the activity of the MXR system in the three species of leeches suggesting their suitability as the in vivo biomonitoring. We also identified a dependence of the transporter activity with the development stage in H. simplex, highlighting the importance of using organisms of similar size classes since it may affect observed results. Finally, we concluded that benthic freshwater macroinvertebrates possess different species-specific levels of MXR activity possibly influencing their natural distribution as well as their survival. 相似文献
517.
In a study of the parasitoid complex of the locust leaf miner Phyllonorycter robiniella (Clemens, 1859), 23 species of its parasitoids were recorded at 18 localities in Serbia. The parasitoid species included 2 species of the family Braconidae, 1 of the family Eupelmidae, and 20 of the family Eulophidae. The recorded species of parasitoids are polyphagous; in addition to Ph. robiniella, they also develop on other species of leaf miners as primary; primary and secondary; or primary, secondary, and tertiary parasitoids. Among the recorded species of parasitoids, the most significant were the species Pholetesor bicolor, Pholetesor nanus, Sympiesis sericeicornis, Sympiesis acalle, Minotetrastichus frontalis, Pediobius saulius, and Baryscapus nigroviolaceus. The parasitoids were found to have a strong effect on the abundance of Ph. robiniella because they reduced more than 50% of its larvae and pupae in the majority of study samples. 相似文献
518.
Velhner M Mitevski D Potkonjak D Stojanović D Kovačević M Petrović T Aleksić-Kovačević S 《Acta veterinaria Hungarica》2010,58(4):499-509
The biological properties of an infectious bursal disease (IBD) virus isolated from bursas collected during an outbreak in a village chicken flock in Macedonia are described. The mortality rate was 50%. Two viruses coexisted in the bursas of infected chickens (IBDVwt and IBDVtc). The virus termed IBDVtc grows on chicken embryo fibroblast (CEF) cells from the first passage. Specific pathogen free chickens inoculated with IBDVtc at passage level 4 did not develop any clinical signs of disease. Some discrete bleeding on the leg muscles was seen and the bursa of Fabricius revealed pathological lesions similar to those caused by classical strains. However, the bursa recovered quickly (bursa lesion score 2) by 14 days post infection (PI). We also found evidence of bursal repopulation by means of perinuclear antigen staining. Strong CD3 influx was evident at 4 days PI, and at 33 days PI the CD3+ cell finding was comparable to the control. The mean antibody titre was 9.2 log 2 at 14 days PI. The amino acid composition of VP2 in IBDVwt (222 Ala, 242 Ile, 253 Gln, 256 Ile, 279 Asp, 284 Ala, 294 Ile and 299 Ser) is described. The same sequence was found in IBDVtc, except for two point mutations, at Gln253→His and Ala284→Thr. Such amino acid substitution is responsible for partial attenuation and the ability of the strain to replicate in cell culture. None of the commercial vaccine viruses has a similar arrangement of amino acids in the variable domain of IBDV. This strongly suggests that IBDVtc originates from a very virulent strain. To the best of our knowledge, this is the first report of a concomitant infection of chickens with highly pathogenic IBDV and its mutant counterpart. 相似文献
519.
Ivana M. Lalić Miloš Miljković Milica Labudović-Borović Nataša Milić Novica M. Milićević 《Anatomia, histologia, embryologia》2020,49(4):433-439
Metallophilic macrophages (MMs) are a distinct cell type of the rodent thymus. Our previous research has focused on the morphological characteristics of MMs, as well as on the molecular mechanisms involved in the development and tissue positioning of these cells. However, the postnatal development of MMs has not been sufficiently studied. In the present study, we investigated the positioning of MMs in the rat thymus between postnatal day 0 (P0) and P30. On P0, MMs were evenly distributed all over the thymic tissue—that is, the cortex, cortico-medullary zone and medulla. From P0 to P15, the number of MMs in the thymic cortex significantly decreased, and after P15, this number did not change. Thus, the present study shows that on P15, MMs almost completely disappear from the thymic cortex and show their adult position in the cortico-medullary zone and in the medulla. 相似文献
520.
Nickolas G. Kavallieratos Christos G. Athanassiou George J. Stathas Željko Tomanović 《Phytoparasitica》2002,30(4):365-377
Samples were collected from southern Greece during 1996–2000 in order to investigate the presence of parasitoids onAphis gossypii Glover infesting several citrus species. The species of aphidiines found to have a significantly different preference forA. gossypii wereAphidius colemani Viereck,Aphidius matricariae Haliday,Diaeretiella rapae (M’Intosh),Ephedrus persicae Froggat,Lysiphlebus testaceipes (Cresson),Binodoxys acalephae (Marshall) andBinodoxys angelicae (Haliday). In another sampling experiment, the relative abundance of aphidiine parasitoids on aphids infesting orange and
tangerine trees was studied in southern Greece (Nea Kios) in 1996 and 1997.A. gossypii constituted the largest part of the aphid population and was the only species parasitized.B. angelicae andA. colemani were the most abundant parasitoid species. The parasitization rate differed among the parasitoid species.B. angelicae had the highest colonization rate in centrally located and large host (A. gossypii) groups, whereasA. colemani was found in more isolated and relatively small host groups. The percentage of parasitism byB. angelicae was high mainly in large host groups, whenB. angelicae was the only parasitoid present. However, in cases of coexistence ofB. angelicae withA. colemani with hyperparasitoids, in the same sampling unit, the percentage of parasitism was relatively low.
http://www.phytoparasitica.org 相似文献