全文获取类型
收费全文 | 939篇 |
免费 | 78篇 |
专业分类
林业 | 106篇 |
农学 | 22篇 |
基础科学 | 3篇 |
203篇 | |
综合类 | 7篇 |
农作物 | 58篇 |
水产渔业 | 58篇 |
畜牧兽医 | 466篇 |
园艺 | 15篇 |
植物保护 | 79篇 |
出版年
2023年 | 3篇 |
2022年 | 7篇 |
2021年 | 23篇 |
2020年 | 22篇 |
2019年 | 21篇 |
2018年 | 58篇 |
2017年 | 57篇 |
2016年 | 60篇 |
2015年 | 38篇 |
2014年 | 41篇 |
2013年 | 47篇 |
2012年 | 64篇 |
2011年 | 79篇 |
2010年 | 57篇 |
2009年 | 19篇 |
2008年 | 33篇 |
2007年 | 43篇 |
2006年 | 30篇 |
2005年 | 34篇 |
2004年 | 43篇 |
2003年 | 31篇 |
2002年 | 42篇 |
2001年 | 16篇 |
2000年 | 12篇 |
1999年 | 15篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1995年 | 8篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 7篇 |
1990年 | 8篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 8篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1977年 | 4篇 |
1976年 | 11篇 |
1975年 | 2篇 |
1972年 | 2篇 |
1967年 | 1篇 |
1966年 | 2篇 |
1965年 | 1篇 |
排序方式: 共有1017条查询结果,搜索用时 62 毫秒
121.
Sapierzyński R Malicka E Bielecki W Krawiec M Osińska B Sendecka H Sobczak-Filipiak M 《Polish journal of veterinary sciences》2007,10(2):97-103
The aim of the study was to estimate the prevalence and localization of different tumors in the urogenital system in dogs and cats in relation to sex, age and breed of animals. The study was performed on tumors or tissue specimens from tumors of the urinary and genital system obtained during surgery from dogs and cats submitted to the Division of Pathological Anatomy, Department of Clinical Sciences Agricultural University of Warsaw from 1998 to 2005. Most tumors of the urogenital system recognized in the present study derived from dogs (94.20%, 130 cases), and only a few cases were obtained from cats (5.79%). Occurrence and localization of urogenital system tumors in present review is similar to findings reported by other authors. Testicular tumors in males, ovarian lesions in females and urinary bladder tumors in both sexes were most commonly recognized. Older dogs were most often affected, animals with nonmalignant tumors were a bit younger than those with malignant lesions. Any obvious breed predilections were found, but terriers were at increased risk for development of transitional cell carcinoma of the urinary bladder and mixed breed and German shepherd for development of testicular neoplasms. 相似文献
122.
Sapierzyński R 《Polish journal of veterinary sciences》2007,10(1):43-46
Peliosis hepatis (PH) is a rare condition characterized by dilatation of hepatic sinusoids and the presence of blood-filled spaces within the liver. The disease occurs mainly in subjects exposed to toxic substances or estrogens, and is often asymptomatic. A 9 year-old pekingese female dog was sent to Division of Pathology for autopsy because of sudden death of unclear cause. Autopsy revealed severe hydroperitoneum (1500 ml of transsudate), dilatation of heart ventricles, passive hyperemia of lungs, spleen and kidneys. The liver was enlarged, with slightly wrinkled surface, with many red spots, of different size and shape. Microscopic examination of the liver revealed the presence of areas with severe dilatation of hepatic sinusoids, and multiple cystic spaces filled with blood. Some of these spaces were lined with endothelium and other were not. Spaces were different in shape and size and were localized in the areas between dilated sinusoids. Based on the macroscopic and microscopic examination, the liver lesions were identified as severe hepatic sinusoidal dilatation with formation of peliosis hepatis-like structures. 相似文献
123.
The paper describes current views on the use of osteochondral autografts and allografts in the treatment of articular cartilage lesions in animals. It presents surgical techniques of grafting and the biological features of osteochondral auto- and allografts, and their effect on the recipient's cartilage. 相似文献
124.
125.
Combined effects of water temperature and daily food availability period on the growth and survival of tench (Tinca tinca) larvae
下载免费PDF全文
![点击此处可从《Aquaculture Research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A 16‐day experiment was designed to find the best combination of water temperature (27, 30, 33°C) and daily duration of food availability (12, 18, 24 h) for larval tench (Tinca tinca) growth and survival. Larvae with an initial mean size of 5.7 mm total length (TL) and 0.7 mg wet body weight (BW) were stocked at 15 L?1. Larvae were fed in excess with live Artemia nauplii with the period of food availability lasting 12, 18 or 24 h daily. The largest final larval size was recorded at 27 and 30°C in groups fed for 24 h a day (17.7 and 17.9 mm TL, 76.1 and 77.7 mg BW, respectively). The combination of the highest temperature and the longest daily food availability was the only set of conditions under which final larval survival was affected (95.4% survival; 98.7–99.9% under all other conditions). The combination of water temperature of about 28.6°C and continuous food availability is recommended as the optimum combination for rearing T. tinca larvae under controlled conditions. Providing continuous food supply to fish larvae under aquaculture conditions was also advantageous in helping to mitigate the effects of slower growth relative to developmental progress, which can occur at high water temperatures. However, should one wish to limit the daily feeding period to 12 h per day, the use of a water temperature between 27.4 and 27.9°C would be the best solution. 相似文献
126.
127.
Joanna Pajdak‐Czaus Aleksandra Platt‐Samoraj Wojciech Szweda Andrzej Krzysztof Siwicki Elbieta Terech‐Majewska 《Aquaculture Research》2019,50(11):3083-3096
Yersinia ruckeri (Y. ruckeri) can cause mortalities that are contributing to substantial economic losses in the rainbow trout (Oncorhynchus mykiss) aquaculture sector. Because of its most characteristic clinical signs, the disease in rainbow trout caused by this pathogen is called enteric redmouth disease. Although it is considered to affect mainly salmonids, there are reports in the available literature of isolating this bacterium from other fish species, both clinically healthy and diseased. The aim of this study was to analyse the available data concerning yersiniosis in non‐salmonid fish. The analysed data indicate that Y. ruckeri is a threat not only to rainbow trout. Some of the affected species have high commercial importance and mortalities may contribute to high economic losses. The disease symptoms may not be specific and can be different from those characteristic for enteric redmouth in trout, which may lead to misdiagnosis. Collected information indicates that infection with Y. ruckeri should be taken into account in the diagnostic procedures not only in salmonids. 相似文献
128.
Maciej Zalewski Barbara Bis Mazgorzata apiska Piotr Frankiewicz Wojciech Puchalski 《水产资源保护:海洋与淡水生态系统》1998,8(2):287-307
1. The effect of riparian ecotone functional complexity and stream hydraulics on an upland river ecosystem has been analysed. 2. The amount of nutrients retained by bottom sediment was lowest on a sandy substrate (range: 26–104 mg m−2 P-PO4) and highest in wetland bays (range: 558–5368 mg m−2 P-PO4). A stream bed covered by Berula erecta had about three times higher retentive nutrient capacity ( x̄ = 584 mg m−2 day−1) than did a sandy substrate( x̄ = 205 mg m−2 day−1). 3. The amount of allochthonous organic matter (CPOM) deposited on the stream bed decreased with current velocity. The trophic potential of CPOM, measured as total protein, was significantly correlated with the amount of deposited CPOM (r = 0.863; p<0.00001) and depended on stream order. 4. Both invertebrate and fish biomass in the upland river were significantly correlated with calcium/bicarbonate (benthos: r = 0.858; p<0.006; fish: r = 0.918; p<0.001). 5. Fish biomass, diversity and species richness were highest in pools, lower in riffles and lowest in the run/transition zone. 6. Macroinvertebrate biomass was highest at an intermediate riparian ecotone complexity with an adequate supply of organic matter and incident light. Fish biomass followed the same trend, being lowest in heavily shaded areas and in open channels without riparian vegetation (range: 1–4.5 g m−2), but highest in ecotones of intermediate complexity (range: 1.6–92.8 g m−2). The ‘cascading effect’ of invertebrate density depletion, which was inversely related to fish biomass, was observed seasonally. 7. The above results indicate that riparian ecotone structure and the heterogeneity of the stream channel may regulate biodiversity, productivity and nutrient retention in the fluvial corridor. These quantitative data help to create alternative scenarios for sustainable river basin management. © 1998 John Wiley & Sons, Ltd. 相似文献
129.
Paweł Nicia Romualda Bejger Paweł Zadrożny Maria Sterzyńska 《Journal of Soils and Sediments》2018,18(8):2770-2776
Purpose
The objective of this study was to determine the impact of restoration processes on the selected soil properties and organic matter transformation of mountain fens under the Caltho-Alnetum community in the Babiogórski National Park in Outer Flysch Carpathians.Materials and methods
Restoration processes were conducted on three degraded mountain fens in the Babiogórski National Park in Outer Flysch Carpathians, Poland. The degradation degree of soils was the criterion for the selection of habitats for further studies. To determine the influence of restoration processes on mountain fen soil properties and organic matter transformation, samples were collected in 2011 and 2013. The soil samples were assayed for pH, base cation concentration, hydrolytic acidity, organic carbon and total nitrogen content, total exchangeable base cation concentration, cation exchange capacity, and base saturation. Organic matter fractions were extracted by IHSS method. Quantitative and qualitative study of organic matter was based on fraction composition analysis and the ratio of humic acid carbon to fulvic acid carbon. The research results were statistically verified.Results and discussion
Based on morphological and chemical properties, the studied mountain fen soils can be classified as Sapric Dranic Eutric Histosols and Sapric Dranic Dystric Histosols according to WRB guidelines (2015). Before restoration processes, the mountain fen soils subjected to a different water regime showed various contents of total nitrogen and organic carbon. The decreasing of the groundwater level was reflected in pH, calcium ion content, exchangeable base cation concentration, and base saturation. The increase of the groundwater level had influence on chemical properties of mountain fen soils such as pH, total exchangeable base cation concentration, hydrolytic acidity, cation exchange capacity, and base saturation. Three-year restoration processes did not cause significant changes in the composition of humic substance fractions.Conclusions
Mountain fens under Caltho-Alnetum community are priority habitats in Babiogórski National Park in Outer Flysch Carpathians, Poland. These habitats responded to restoration processes in varying degrees depending on the extent of their degradation. The least degraded mountain fen was characterized by a short response time on the restoration processes. The reaction of higher degraded habitats was weaker.130.
Piotr Hulisz Przemysław Charzyński Andrzej Greinert 《Journal of Soils and Sediments》2018,18(2):358-372