全文获取类型
收费全文 | 451篇 |
免费 | 28篇 |
专业分类
林业 | 22篇 |
农学 | 15篇 |
基础科学 | 6篇 |
141篇 | |
综合类 | 27篇 |
农作物 | 21篇 |
水产渔业 | 32篇 |
畜牧兽医 | 157篇 |
园艺 | 16篇 |
植物保护 | 42篇 |
出版年
2023年 | 7篇 |
2022年 | 8篇 |
2021年 | 9篇 |
2020年 | 15篇 |
2019年 | 21篇 |
2018年 | 18篇 |
2017年 | 19篇 |
2016年 | 23篇 |
2015年 | 15篇 |
2014年 | 15篇 |
2013年 | 22篇 |
2012年 | 34篇 |
2011年 | 31篇 |
2010年 | 21篇 |
2009年 | 20篇 |
2008年 | 32篇 |
2007年 | 25篇 |
2006年 | 28篇 |
2005年 | 34篇 |
2004年 | 25篇 |
2003年 | 17篇 |
2002年 | 14篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
排序方式: 共有479条查询结果,搜索用时 15 毫秒
1.
Sydney Mukaratirwa Claudio Petterino Alys Bradley 《Journal of toxicologic pathology》2015,28(3):177-180
A single mass was found on the left submandibular salivary gland at necropsy of a 15-month-old male commercially bred laboratory Beagle dog from a control dose group from a repeat toxicity study. Microscopically, the mass was composed of a well-demarcated area of coagulative necrosis surrounded and separated from the normal salivary gland tissue by a thick fibrovascular capsule. Necrosis was admixed with areas of hemorrhage, fibrin, edema, fibrinoid necrosis of the vascular tunica media, and thrombosis of small and large vessels. Within the necrotic tissue, there was marked ductal hyperplasia, and squamous metaplasia of duct and acinar epithelium. The mass was diagnosed as necrotizing sialometaplasia of the submandibular gland. Hyperplastic ductal elements and squamous metaplasia can be mistaken microscopically with squamous cell carcinoma. Therefore, pathologists should be aware of this lesion as to avoid errors in the diagnosis of this benign pathologic condition. 相似文献
2.
Survival and Growth Improvement of Palm Ruff,Seriolella violacea,Larvae Fed Artemia Nauplii Enriched with an Experimental Emulsion 下载免费PDF全文
Adens González Alfonso Silva Gonzalo Gajardo Claudio Martínez 《Journal of the World Aquaculture Society》2017,48(2):268-279
The palm ruff, Seriolella violacea (Cojinoba), is a potential new species for Chilean aquaculture. To approach Cojinoba larviculture, an experimental Artemia enrichment emulsion, containing docosahexaenoic acid (DHA)/eicosapentaenoic acid (EPA) = 2.5, supplemented with vitamin E, astaxanthin, and β‐glucan, was evaluated in both Artemia and Cojinoba larvae, 30–50 d.a.h. This study tested an experimental enrichment emulsion versus a commercial emulsion, with an integral approach of multicompound emulsions. After 23 h enrichment, experimental emulsion (EE)‐enriched nauplii reached DHA and EPA concentrations of 23.8 and 18.7 mg/g dry weight (dwt), respectively, while in Cojinoba larvae they were 18.4 and 19.7 mg/g dwt. Control emulsion (CE)‐enriched nauplii exhibited lower DHA and EPA (6.1 and 7.7 mg/g dwt), while only DHA decreased in the control larvae (12.6 mg/g dwt). Vitamin E was higher in EE‐enriched nauplii (29.2 mg/100 g dwt) than in the control (8.4 mg/100 g dwt). Larvae fed EE‐enriched Artemia exhibited 8% increase in survival and 19% in growth compared with the control. Astaxanthin was detected only in larvae fed EE‐enriched nauplii. The tumor necrosis factor‐α concentration was not significantly different between larvae fed EE‐ and CE‐enriched nauplii. EE looks promising as an Artemia enrichment and experimental diet to assess palm ruff larval requirements, and has a positive impact on fish larvae performance. 相似文献
3.
José AlvesJr Marcos V. Folegatti Larry R. Parsons Wije Bandaranayake Claudio R. da Silva Tonny J. A. da Silva Luís F. S. M. Campeche 《Irrigation Science》2007,25(4):419-428
The expansion of permanent trickle irrigation systems in Sao Paulo (Brazil) citrus has changed the focus of irrigation scheduling
from determining irrigation timing to quantifying irrigation amounts. The water requirements of citrus orchards are difficult
to estimate, since they are influenced by heterogeneous factors such as age, planting density and irrigation system. In this
study, we estimated the water requirements of young ‘Tahiti’ lime orchards, considering the independent contributions from
soil evaporation and crop transpiration by splitting the crop coefficient (Kc = ETc/ETo) into two separate coefficients; Ke,
a soil evaporation coefficient and Kcb, a crop transpiration coefficient. Hence, the water requirement in young ‘Tahiti’ lime
(ETy) is ETy = (Ke + Kcb) · ETo, where ETo is the reference crop evapotranspiration. Mature tree water requirement (ETm) is ETm = Kcb · ETo, assuming no soil water evaporation. Two lysimeters were used; one was 1.6 m in diameter and 0.7 m deep, and
the other was 2.7 m in diameter and 0.8-m deep. The first one was used to calculate evaporation and the second one was used
for transpiration. ETo was estimated by the Penman–Monteith method (FAO-56). The measurements were conducted during a period
between August 2002 and April 2005 in Piracicaba, Sao Paulo state, Brazil. The lysimeters were installed at the center of
a 1.0-ha plot planted with ‘Tahiti’ lime trees grafted on ‘Swingle’ citrumelo rootstock. The trees were 1-year old at planting,
spaced 7 × 4 m, and were irrigated by a drip irrigation system. During the study period, Kc varied between 0.6 and 1.22, and
Kcb varied between 0.4 and 1.0. The results suggested that for young lime trees, the volume of water per tree calculated by
Ke + Kcb is about 80% higher than the volume calculated using Kc. For mature trees, the volume of water per tree calculated
using just Kcb can be 10% less than using Kc. The independent influence of soil evaporation and transpiration is important to better understand the water consumption of
young lime trees during growth compared to mature lime trees. 相似文献
4.
5.
The objectives of this study were to optimize RAPD and AFLP techniques in B. catharticus, and to determine the genetic variability of populations and commercial prairie grass cultivars with the aforementioned molecular
markers. Two populations with contrasting morphological characteristics were evaluated from individual and bulked DNA samples
using RAPD markers. Both analyses showed a similar information about inter population variability. Each accession was sampled
by a single leaf bulk of 10 plants. Accession similarities were established with 276 RAPD and 714 AFLP bands using Jaccard
similarity coefficient. The dendrogram of the accessions using RAPD markers showed that they shared high similarity values
(>94%). A similar result was obtained with AFLP markers (similarity values >98%), revealing a narrow genetic basis in the
analyzed accessions. Consequently, molecular characterization of germplasm should be considered in addition to morphological
criteria, to choose the parental genotypes for breeding programs of this forage crop. The AFLP technique was more efficient
to detect DNA polymorphism in our experiments and unique fingerprints were detected for all the accessions. RAPD is a simple
and non expensive technique, suitable to estimate genetic similarity.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
6.
Summary The invasive potential of a species can be assessed by propagule pressure, which measures the chances for propagules of a
species to find a suitable habitat for establishment and reproduction. Seeds, fruits, and vegetative structures that contribute
to the propagule pressure are morphologically, physiologically and genetically different from one another, thus each kind
should have a specific way of contributing to a successful invasion. In this paper we review plant traits that contribute
to the propagule pressure. Seed production provides an estimate of the potential multiplication rate of the weed. However,
it is gap-sensing mechanisms of seeds based on dormancy termination and germination requirements, which significantly contribute
to the naturalization and invasion processes assuring a successful seedling establishment in environments of high competition.
Dispersal of propagules reduces competition, mating with a sibling, and subsequent inbreeding depression, and increases colonization
opportunities and range of expansion. Some of those benefits can be achieved in a population by existence of dormancy mechanisms
and thus, the existence of a seed bank. Finally, vegetative propagation may ensure expansion of local populations when seedling
establishment is low. Broadening the scope of traits that are considered in the breeding programs aimed at commercial production
of plant propagules, to include those related to propagule pressure, is essential for adequate evaluation of invasive potential. 相似文献
7.
8.
Claudio E. Rafanelli Gianna L. Petriconi Henry M. Papee 《Water, air, and soil pollution》1979,12(3):283-294
Our earlier research on the photochlorination of some organics suspended in solutions of aqueous Cl? codissolved with anionic NO x ? is extended to systems comprising either bromides or iodides, and NO 3 ? . It is found that the bromide-containing systems follow, under both artificial UV and sunlight, overall reaction patterns quite similar to those of chlorides although the rate term which stands for the bromination of organics is larger and directly proportional to light intensities. Solutions containing iodides also follow a similar overall pattern but the first rate term is now proportional to the square of light intensity. However, they react liberating detectable amounts of iodine which thereafter attack the hydrocarbon. This excess of elementary iodine is thus found to be either dissolved in or adsorbed by the organic; it furthermore also dissolves and becomes complexed in the aqueous phase. 相似文献
9.
Cefarelli G D'Abrosca B Fiorentino A Izzo A Mastellone C Pacifico S Piscopo V 《Journal of agricultural and food chemistry》2006,54(3):803-809
Forty-three secondary metabolites were isolated and characterized from cv. Annurca apple fruit, an apple variety cultivated in the south of Italy. This apple cultivar undergoes a typical reddening treatment after collection. All of the compounds were characterized on the basis of their spectroscopic data. The compounds were tested for their radical-scavenging and antioxidant activities by measuring their capacity to scavenge DPPH* (2,2'-diphenyl-1-picrylhydrazyl radical), H2O2, and NO (nitric oxide) and to inhibit the formation of methyl linoleate conjugated diene hydroperoxides or TBARS (thiobarbituric acid reactive species). 相似文献
10.