全文获取类型
收费全文 | 1492篇 |
免费 | 133篇 |
专业分类
林业 | 173篇 |
农学 | 47篇 |
基础科学 | 2篇 |
369篇 | |
综合类 | 7篇 |
农作物 | 92篇 |
水产渔业 | 101篇 |
畜牧兽医 | 685篇 |
园艺 | 27篇 |
植物保护 | 122篇 |
出版年
2023年 | 11篇 |
2022年 | 14篇 |
2021年 | 40篇 |
2020年 | 43篇 |
2019年 | 40篇 |
2018年 | 105篇 |
2017年 | 98篇 |
2016年 | 104篇 |
2015年 | 65篇 |
2014年 | 70篇 |
2013年 | 93篇 |
2012年 | 107篇 |
2011年 | 121篇 |
2010年 | 78篇 |
2009年 | 30篇 |
2008年 | 56篇 |
2007年 | 66篇 |
2006年 | 42篇 |
2005年 | 54篇 |
2004年 | 53篇 |
2003年 | 48篇 |
2002年 | 51篇 |
2001年 | 24篇 |
2000年 | 18篇 |
1999年 | 25篇 |
1998年 | 7篇 |
1997年 | 7篇 |
1996年 | 7篇 |
1995年 | 11篇 |
1994年 | 5篇 |
1993年 | 8篇 |
1992年 | 6篇 |
1991年 | 8篇 |
1990年 | 9篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 9篇 |
1985年 | 6篇 |
1984年 | 9篇 |
1983年 | 4篇 |
1982年 | 10篇 |
1981年 | 8篇 |
1977年 | 7篇 |
1976年 | 14篇 |
1975年 | 2篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1968年 | 2篇 |
1966年 | 2篇 |
排序方式: 共有1625条查询结果,搜索用时 31 毫秒
61.
K. Bieniarz P. Epler W. Popek R. Billard M. Sokołowska 《Fish physiology and biochemistry》1986,2(1-4):109-114
Effects of pimozide (Pim) and [(D-Ala6, Pro9-NEt) LHRH] (LRH-Aa) on common carp oocytes maturation and ovulationin vivo under laboratory and commercial fisheries farm conditions were investigated.Although injections of Pim and LRH-Aa at the doses of 10 mg and 50 µg/kg body weight respectively, did not increase mGtH levels (66.7–155.8 mg/ml) as much as injections of carp pituitary extract (chh) (382.1 ng/ml), induced GtH levels were high enough to induce ovulation. Changes in the ovary caused by Pim and LRH-Aa were similar to those induced by chh, and Pim injected together with LRH-Aa in a single injection gave the same results concerning ovulation induction as when they were applied separately at 6h interval. 相似文献
62.
Radioimmunology was used to determine leptin and ghrelin levels in sow colostrum and milk in relation to those in sow and neonatal pig blood plasma and to the body weight of piglets during the first week of lactation. The highest concentration of leptin was found in colostrum on the second day of lactation (69.3 ± 6.3 ng/mL). Leptin concentrations in sow plasma were significantly lower than in colostrum/milk (2.19 ± 0.9 ng/mL, P = 0.7692) and were stable in the first 7 days of lactation. Total and active ghrelin concentrations in colostrum/milk were stable in the measured time points (6734 ± 261 pg/mL, P = 0.3397; 831 ± 242 pg/mL, P = 0.3988, respectively). Total ghrelin concentrations in sow plasma were lower than in colostrum/milk. These results indicate that pigs follow a unique species‐specific pattern of leptin and ghrelin synthesis, release and existence, and that the mammary gland is an important source of leptin and ghrelin contained in colostrum/milk. 相似文献
63.
In this study, we have determined serum neopterin levels in female dogs with primary malignant mammary tumours. The study involved 50 female dogs which had a malignant mammary tumours removed surgically (32 animals with carcinoma, 12 animals with sarcoma and 6 animals with carcinosarcoma) and 10 clinically healthy female dogs. Serum neopterin levels were determined using a commercial ELISA kit. The mean neopterin levels were lower in the malignant tumour groups than in healthy animals but differences were statistically significant only in carcinoma and sarcoma groups. The decrease of neopterin levels in animals with malignant mammary tumours may suggest their decreased cellular immunity. Moreover, it might indicate that decreased activity of cellular mechanisms of the anti‐neoplastic response is one of the factors associated with the development and course of malignant mammary tumours in female dogs; however, further studies are necessary. 相似文献
64.
Rafa??KamińskiEmail author Micha??Korwin-Kossakowski Jan?Kusznierz Leszek?Myszkowski L. Andrzej?Stanny Jacek?Wolnicki 《Aquaculture International》2005,13(5):479-486
Three commercial starters (Carp Starter, Uni Starter and Perla Plus) and one non-commercial, with frozen Chironomidae larvae as a reference diet, were evaluated for the intensive rearing of juvenile lake minnow Eupallasella perenurus, a cyprinid fish that is critically endangered in Poland. The growth, condition, survival, body deformities, and chemical body composition were studied. The 90-day laboratory experiment was performed at 22 °C with fish that were initially 24.6 mm (mean total lenth (TL)) and 0.11 g (mean body weight (BW)). Satisfactory fish growth was attained with all of the diets; however, the largest (p ≤ 0.05) final size (48.5 mm TL, 1.55 g BW) and the lowest condition coefficient (K = 1.34) were noted in fish fed the non-commercial starter. The final survival rates were very high (97.5–100%). Skeletal deformities (in 74 to 92% fish) were recorded exclusively in fish fed commercial starters. All commercial starters resulted in considerably higher lipid content and lower ash content than did the non-commercial starter and the reference diet. This suggests that both these factors might be responsible for body deformities. The present results proved that only the non-commercial starter is suitable for juvenile E. perenurus rearing under controlled condition, and that none of the commercial starters can be recommended. 相似文献
65.
Kevin D. Friedland Michelle Bachman Andrew Davies Romain Frelat M. Conor McManus Ryan Morse Bradley A. Pickens Szymon Smoliński Kisei Tanaka 《水产资源保护:海洋与淡水生态系统》2021,31(6):1482-1498
- Species distribution models for marine organisms are increasingly used for a range of applications, including spatial planning, conservation, and fisheries management. These models have been constructed using a variety of mathematical forms and drawing on both physical and biological independent variables; however, what might be called first-generation models have mainly followed the form of linear models, or smoothing splines, informed by data collected in the context of fish surveys.
- The performance of different classes of variables were tested in a series of species occurrence models built with machine learning methods, specifically evaluating the potential contribution of lower trophic level data. Random forest models were fitted based on the classification of the absence/presence for fish and macroinvertebrates surveyed on the US Northeast Continental Shelf.
- The potential variables included physical, primary production, secondary production, and terrain variables. For accepted model fits, six variable importance measures were computed, which collectively showed that physical and secondary production variables make the greatest contribution across all models. In contrast, terrain variables made the least contribution to these models.
- Multivariable analyses that account for all performance measures reinforce the role of water depth and temperature in defining species presence and absence; however, chlorophyll concentration and some specific zooplankton taxa, such as Metridia lucens and Paracalanus parvus, also make important contributions with strong seasonal variations.
- Our results suggest that lower trophic level variables, if available, are valuable in the creation of species distribution models for marine organisms.
66.
Sławomir Wróbel 《American Journal of Potato Research》2014,91(6):706-713
The impact of a dozen mixtures of the most commonly applied aphicides: Mospilan 20 SP (acetamiprid), Pirimor 500 (pirimicarb) and Karate Zeon 050 CS (lambda-cyhalothrin), combined with the mineral oil Sunspray 850 EC, was researched in field conditions to assess their effectiveness in limiting potato tuber PVY, PVM and PLRV infection. In spite of the greatest reduction in the number of aphids occurring following application of Mospilan 20 SP, this treatment was not as effective in limiting PVY infection as, for example, applying Sunspray 850 EC mineral oil. Mineral oil, when used on its own or in a mixture with Pirimor 500 WG, was found to be the most effective measure for limiting PVY infection (the incidence of tubers infested with PVY was reduced by 64 % relative to control, i.e. no protection). A slightly weaker effect was observed in the case of a combination of the mineral oil with full doses of Karate Zeon 050 CS with a half of a dose of Mospilan 20 SP insecticide, however only for protection against PVY. A similar trend was observed for PVM even though a significant difference was only observed for Sunspray 850EC?+?Pirimor 500WG. In conclusion, the application of insecticide mixtures with mineral oil in protecting against PVY infection is not always as effective as the application of the oil itself only. Addition of the insecticide may sometimes improve the efficacy of protection, however, due to the extra costs involved, not always does it have to be economical. 相似文献
67.
Joanna Sobczyk Piotr Frączek Michał Obarzanowski Julio M. del Hoyo-Meléndez Łukasz Bratasz 《Wood Science and Technology》2014,48(5):981-994
Consolidation treatments are commonly employed in museum conservation studios for treating biologically deteriorated wooden cultural heritage objects. Impregnation using either a solvent/resin or a polymerizing system is an example of such an intervention, which is often difficult to describe in terms of its behavior within the object’s structure. A new simple method has been devised to evaluate the effectiveness of these impregnation treatments in terms of spatial distribution of consolidant solution. A combination of digital radiography and imaging analysis has permitted to evaluate the degree of penetration of a consolidant and to determine its location within the artifact by studying the X-ray images taken before, during, and after treatment. The adequacy of polymer solutions or their effectiveness as wood consolidants is properties which are often difficult to investigate due to limited visual access to the interior of the object. The proposed method provides an alternative way of studying these parameters through analysis of X-ray attenuation recorded on two images: taken before and after the conservation treatment. The resulting image is then converted into a two-dimensional map of consolidation agent within the object using a straightforward calibration procedure. 相似文献
68.
Anna Lisek Danuta Kucharska Agnieszka Głowacka Elżbieta Rozpara 《The Journal of Horticultural Science and Biotechnology》2017,92(5):484-492
The sour cherry is known to exhibit the phenomenon of gametophytic self-incompatibility which prevents self-fertilization. In sour cherry, besides self-incompatible cultivars, there often occur self-compatible cultivars. This is due to the occurrence of natural mutations of the S-RNase or SFB genes and, consequently, loss of functionality of S-alleles. Here we present the results of the identification of S-haplotypes of 21 cultivars of sour cherry from various regions of Europe. The analyses were performed using methods based on the amplification of intron I and intron II of the S-RNase gene and fragments specific to the individual alleles of the S-RNase or SFB genes. The tested cultivars were found to contain 15 S-haplotypes: S1, S1?, S4, S6, S6m, S6m2, S9, S12, S13, S13?, S26, S35, S36a, S36b, and S36b2. The most frequently occurring S-haplotypes were S13? (61.9%), S36a (57.1%), and S26 (47.6%). On the basis of the results, 17 of the 21 cultivars were deduced to be self-compatible. The results will be of use in the production of sour cherry fruit by facilitating the selection of suitable pollinating cultivars. The results are also expected to be useful in the breeding of new cultivars of sour cherry when selecting genotypes for crosses. 相似文献
69.
In earlier in vitro experiments opioids affected steroidogenesis in porcine luteal and granulosa cells. The present studies were undertaken to examine the effects of FK 33-824 (opioid agonist) alone or in combination with LH, PRL or naloxone (NAL, opioid antagonist) on steroidogenesis in cultured porcine theca cells. Moreover, we have tested beta-endorphin-like immunoreactivity (beta-END-LI) concentrations in culture media under control conditions and following treatments of theca cells with LH, PRL, progesterone (P4), oestradiol (E2) or testosterone (T). FK 33-824 and NAL significantly increased P4 release by theca cells and inhibited stimulatory effect of LH on this steroid output. PRL-induced P4 secretion from the cells was blunted only by FK 33-824. Secretion of androstenedione (A4) and T was essentially elevated in the presence of FK 33-824 and this potentiation of both androgen release was completely abolished by PRL. NAL blocked stimulatory effect of the opioid agonist only in case of T. Secretion of oestradiol and oestrone was completely free from the influence of both the opioid agonist and antagonist. Pig theca cells were able to produce beta-END-LI but none of tested hormones (LH, PRL, P4, E2 and T alone or in combination) significantly affected this production. In conclusion, these data indicate that porcine theca cells may produce beta-END-LI and change their steroidogenesis in response to opioid peptides. 相似文献
70.
van den Borne JJ Weström BR Kruszewska D Botermans JA Svendsen J Woliński J Pierzynowski SG 《Journal of animal science》2007,85(2):404-412
The objective of this study was to quantify and compare the effects of sow's milk and 2 milk replacer diets (containing clotting or non-clotting protein sources) on exocrine pancreatic secretion, plasma cholecystokinin, and immunoreactive cationic trypsin in pigs. In addition, the relationship between exocrine pancreatic secretion and growth in milk-fed pigs was studied. In a changeover experiment, 9 chronically catheterized pigs of 6.6 +/- 0.19 kg of BW were studied for 3 wk. Pigs were assigned to each of 3 diets. Exocrine pancreatic secretion was measured from the third to the seventh day on each diet. The protein content and trypsin activity of the pancreatic juice were measured. Blood samples were taken at 10 min before and after milk ingestion and were analyzed for cholecystokinin and immunoreactive cationic trypsin. Pancreatic protein and trypsin secretion did not differ between pigs fed sow's milk and those fed milk replacer, but the volume secreted was less for the pigs fed sow's milk (0.75 vs. 1.03 mL x kg(-1) x h(-1); P < 0.01). A postprandial response to milk intake was not observed. The 2 milk replacer diets did not affect exocrine pancreatic secretion differently. The average exocrine pancreatic secretion (volume, 0.94 mL x kg(-1) x h(-1); protein, 4.28 mg x kg(-1) x h(-1); trypsin, 1.65 U x kg(-1) x h(-1)) was intermediate between literature values for suckling and weaned pigs. Plasma cholecystokinin was elevated (approximately 18 pmol x L(-1)) and showed low correlations with the pancreatic secretion traits. Plasma immunoreactive cationic trypsin was not significantly related to any of the pancreatic secretion traits and should therefore not be used as an indicator for exocrine pancreatic function in milk-fed pigs. Exocrine pancreatic secretion varied substantially among individual pigs (protein, 0.22 to 13.98 mg x kg(-1) x h(-1)). Pancreatic protein and trypsin secretion showed a positive, nonlinear relationship with performance traits. It was concluded that neither specific sow's milk ingredients nor the protein source are responsible for a low pancreatic protein secretion in suckling pigs. Exocrine pancreatic secretion was positively correlated with ADG in pigs at an identical milk intake. 相似文献