全文获取类型
收费全文 | 92篇 |
免费 | 8篇 |
国内免费 | 4篇 |
专业分类
104篇 |
出版年
2022年 | 2篇 |
2019年 | 1篇 |
2018年 | 4篇 |
2017年 | 2篇 |
2016年 | 8篇 |
2015年 | 8篇 |
2014年 | 13篇 |
2013年 | 3篇 |
2012年 | 3篇 |
2011年 | 5篇 |
2010年 | 4篇 |
2009年 | 7篇 |
2008年 | 4篇 |
2006年 | 4篇 |
2005年 | 6篇 |
2004年 | 4篇 |
2002年 | 2篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 5篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1985年 | 1篇 |
1983年 | 4篇 |
1978年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有104条查询结果,搜索用时 15 毫秒
41.
Jan Willem Erisman Nelleke Domburg Wim de Vries Hans Kros Bronno de Haan Kaj Sanders 《中国科学:生命科学英文版》2005,48(Z2)
The Netherlands is "well known" for its nitrogen problems; it has one of the highest reactive nitrogen (Nr) emission densities in the world. It is a small country at the delta of several large European rivers. Ever since the industrial revolution, there has been a growing excess of nutrients and related emissions into the atmosphere (ammonia, nitrogen oxides and nitrous oxide) and into groundwater and surface water (nitrate), leading to a large range of cascading environmental impacts. Vehicular traffic, sewage and animal husbandry are the main sources of oxidized and reduced forms of Nr. This paper provides an overview of the origin and fate of nitrogen in the Netherlands, the various reported impacts of nitrogen, the Dutch and European policies to reduce nitrogen emissions and related impacts. In addition, ways are presented to go forward to potentially solve the problems in a European perspective. Solutions include the improvement of nitrogen efficiencies in different systems, technological options and education. 相似文献
42.
TJS Alves GS Cruz V Wanderley-Teixeira AAC Teixeira JV Oliveira AA Correia 《Biotechnic & histochemistry》2014,89(4):245-255
The fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), not only damages crops, but controlling its population also requires synthetic insecticides, which leads to selection of resistant populations and environmental contamination. Essential oils are an alternative for controlling this insect. There are few studies of the effects of these oils on the insect's reproductive system. We evaluated the effects of the long pepper, Piper hispidinervum, essential oil on the gonads of the armyworm and tested its possible influence on the fertility of this insect. Dosages of 30 and 50 mg/ml were tested in 3rd instar caterpillars using the leaf immersion method. Testes and ovarioles were collected, fixed with 10% formalin and embedded in Historesin. The sections were stained with toluidine blue and Mallory trichrome to detect connective tissue, periodic acid-Schiff to detect neutral carbohydrates, and bromophenol blue to detect proteins. We found that the long pepper essential oil affected negatively the spermatogenesis and altered the histochemistry of the ovarioles of S. frugiperda. The effects of long pepper oil suggest that it is a promising tool for controlling the armyworm pest. 相似文献
43.
44.
45.
AA Baiomy 《African Journal of Aquatic Science》2016,41(2):181-191
Fish health is affected by water pollution. Oreochromis niloticus collected during summer 2014 from El-Serw, a polluted site on the Nile River, were compared with fish from a reference site, El-Zamalek. Histopathological changes were detected in gill and liver tissue samples using light and electron microscopy. In addition, the degree of DNA damage was measured using the comet assay. To indicate the severity of water pollution at the two sites, physico-chemical properties and heavy metal concentrations were investigated. Gill damage, including lamellar cell hyperplasia and aneurysm, was observed in the fish samples from the polluted site. The livers of fish from the polluted area showed necrosis and an increase in melanomacrophage centres. Histochemical results confirmed a marked rise of gill mucopolysaccharides and a reduction of carbohydrate stored in hepatocytes. Electron microscopy revealed clear alterations in gill and liver tissue of fish from the polluted site. The comet assay showed highly significant DNA damage in tilapia collected from the polluted site, compared to those from the reference site. Histopathological biomarkers and the comet assay may therefore be sensitive indicators of exposure to mixtures of aquatic pollutants in Nile tilapia. 相似文献
46.
47.
Uwe Thissen Suzan Wopereis Sjoerd AA van den Berg Ivana Bobeldijk Robert Kleemann Teake Kooistra Ko Willems van Dijk Ben van Ommen Age K Smilde 《BMC bioinformatics》2009,10(1):52
Background
In the fields of life sciences, so-called designed studies are used for studying complex biological systems. The data derived from these studies comply with a study design aimed at generating relevant information while diminishing unwanted variation (noise). Knowledge about the study design can be used to decompose the total data into data blocks that are associated with specific effects. Subsequent statistical analysis can be improved by this decomposition if these are applied on selected combinations of effects. 相似文献48.
Dadkhah A Fatemi F Kazemnejad S Rasmi Y Ashrafi-Helan J Allameh A 《Molecular and cellular biochemistry》2006,281(1-2):145-152
Recently we reported that ferric reducing ability of plasma (FRAP) assay, as an index of total antioxidant activity, increases
in growing rats in response to high dose of vitamin K. In this study, it was found that acetaminophen (APAP) can cause elevation
in FRAP in suckling and adult rats. This study was initiated to assess the contribution of individual antioxidant factors
on elevation in FRAP. A surge in FRAP, 1 h after high dose APAP (250 or 450 mg/kg BW) administration was recorded in both
young as well as adults. Whereas, low dose drug (25 mg/kg) failed to alter FRAP in both the age groups. Time-course studies
show that drug-dependent elevation in FRAP begin rapidly, reaching a maximum at 1 h (> 500%). Increased FRAP was associated
with a marked increase (∼14-fold) in plasma bilirubin, 6 h after drug administration at 450 mg/kg only in suckling rats. Similarly,
APAP-related increase in superoxide dismutase activity in erythrocytes was limited to young rats of both the age groups. Other
factors measured during this period viz., plasma uric acid, bilirubin and total protein together with catalase activity of
erythrocytes remained unchanged in treated rats. Under these circumstances, APAP-related depletion in liver glutathione was
almost similar in both the age groups. During a 12 h study, the concentration of lipid peroxidation products, in liver of
treated groups remained within the levels of respective controls. The endpoint hepatotoxic effects of APAP was almost similar
in both the age groups, suggesting that like adults, immature rats can cope with toxic effects of APAP owing to their drug-dependent
induction in certain antioxidant factors. 相似文献
49.
D Lederoun P Vandewalle AA Brahim J Moreau PA Lalèyè 《African Journal of Aquatic Science》2016,41(2):151-160
Growth, mortality, recruitment and relative yield per recruit of Sarotherodon galilaeus galilaeus from Lakes Doukon and Togbadji were studied. Data on total length, total weight and sex were recorded on a monthly basis between January and December 2013 for S. g. galilaeus captured by local fishers. The estimated asymptotic lengths L∞ were 26.2 and 23.6?cm for Lakes Doukon and Togbadji, respectively, while the growth rate K was 0.73 in Lake Doukon and 0.87 in Lake Togbadji. Estimates of fishing mortality, 0.27 and 0.47 y?1 for Doukon and Togbadji, respectively, were low relative to natural mortality, 1.51 and 1.74 y?1, respectively. Sizes at first sexual maturity were 12.8 and 13.2?cm for females and males, respectively, in Lake Doukon, and 11.5 and 12.4?cm for females and males, respectively, in Lake Togbadji. The size at first capture was estimated at 13.3 and 12.7?cm for Lakes Doukon and Togbadji, respectively, which, in the light of the size at maturity estimates, indicates that fish spawn at least once before capture. The current exploitation rates of 0.15 for Lake Doukon and 0.21 for Lake Togbadji suggest that their stocks of S. g. galilaeus are not overexploited in either lake. 相似文献
50.
The XI International Rotifer Symposium was held during 11–18 March, 2006 at the National Autonomous University of Mexico Campus Iztacala located at the North Mexico City (Mexico). These triennial international meetings, first organized in Austria by Late Ruttner-Kolisko in September 1976, are gradually becoming the focal point of discussion and collaboration from rotifer workers across the world. The present XI symposium was attended by 125 participants from 20 nations. During this meeting, different themes of rotifer research from morphology to molecular biology were considered. In addition, there were four invited lectures and four workshops covering different themes of the symposium. During the last 30 years, rotifer research has witnessed gradual shift from the conventional morphological taxonomy to molecular and evolutionary systematics. While the basic rotifer ecological studies continue today, applied areas such as ecotoxicology and aquaculture have taken key roles in the recent meetings. The international rotifer meetings provide ample opportunities not only for exchange of ideas and recent research, but also for material and in establishing inter-personal relationships. Over the last 30 years, the number of participants attending the rotifer meetings has increased. 相似文献