全文获取类型
收费全文 | 109篇 |
免费 | 8篇 |
专业分类
117篇 |
出版年
2021年 | 1篇 |
2017年 | 3篇 |
2016年 | 2篇 |
2015年 | 6篇 |
2014年 | 8篇 |
2013年 | 2篇 |
2012年 | 6篇 |
2011年 | 5篇 |
2010年 | 12篇 |
2009年 | 8篇 |
2008年 | 6篇 |
2007年 | 2篇 |
2006年 | 7篇 |
2005年 | 5篇 |
2004年 | 5篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2001年 | 2篇 |
2000年 | 4篇 |
1999年 | 3篇 |
1998年 | 6篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1987年 | 1篇 |
1977年 | 2篇 |
1973年 | 1篇 |
1962年 | 1篇 |
1955年 | 1篇 |
1952年 | 1篇 |
1948年 | 1篇 |
1947年 | 1篇 |
排序方式: 共有117条查询结果,搜索用时 15 毫秒
91.
Besides their important contribution to global biodiversity, mangroves provide many services. Nevertheless, due to an increase of human activities and to climate change, in less than 20 years these ecosystems have lost one fifth of their global surface area. In response to this decrease, mangrove reforestation incentives have spread throughout the world. The scientific and societal legitimacy of reforestation actions still remain in question. Focusing on two case studies, the Saloum Delta and Lower Casamance, Senegal, our methodology was mainly based on the analysis of environmental narratives and discourses between 2009 and 2013, and on reforestation campaigns conducted by NGOs. We highlight the complexity of the system of values associated with the mangroves, as well as the positive and negative interactions between the services. Even although the reforestation campaigns were generally successful in terms of reforested surfaces and international visibility, they were poor in terms of biological and cultural diversities and led to spatial injustice. Moreover, the extensive reforestation with a unique mangrove species, Rhizophora mangle, was perceived as means of ‘green grabbing’, and the simultaneous buying of carbon tax by industrial conglomerates induced disempowerment of the local communities. More integrated research programmes must be developed towards the extensive knowledge of the mangroves. 相似文献
92.
Barry A Pepers Menno H Schut Rolf HAM Vossen Gert-Jan B van Ommen Johan T den Dunnen Willeke MC van Roon-Mom 《BMC biotechnology》2009,9(1):50-6
Background
Methodologies like phage display selection, in vitro mutagenesis and the determination of allelic expression differences include steps where large numbers of clones need to be compared and characterised. In the current study we show that high-resolution melt curve analysis (HRMA) is a simple, cost-saving tool to quickly study clonal variation without prior nucleotide sequence knowledge. 相似文献93.
Victoria Cavaliere Daniela L Papademetrio Mario Lorenzetti Pamela Valva María Victoria Preciado Patricia Gargallo Irene Larripa Mariela B Monreal María Laura Pardo Silvia E Hajos Guillermo AC Blanco élida MC álvarez 《Translational oncology》2009,2(1):46-58
Chemotherapy aims to limit proliferation and induce apoptotic cell death in tumor cells. Owing to blockade of signaling pathways involved in cell survival and proliferation, nuclear factor κB (NF-κB) inhibitors can induce apoptosis in a number of hematological malignancies. The efficacy of conventional chemotherapeutic drugs, such as vincristine (VCR) and doxorubicine (DOX), may be enhanced with combined therapy based on NF-κB modulation. In this study, we evaluated the effect of caffeic acid phenylethyl ester (CAPE) and MG-132, two nonspecific NF-κB inhibitors, and conventional chemotherapeutics drugs DOX and VCR on cell proliferation and apoptosis induction on a lymphoblastoid B-cell line, PL104, established and characterized in our laboratory. CAPE and MG-132 treatment showed a strong antiproliferative effect accompanied by clear cell cycle deregulation and apoptosis induction. Doxorubicine and VCR showed antiproliferative effects similar to those of CAPE and MG-132, although the latter drugs showed an apoptotic rate two-fold higher than DOX and VCR. None of the four compounds showed cytotoxic effect on peripheral mononuclear cells from healthy volunteers. CAPE- and MG-132-treated bone marrow cells from patients with myeloid and lymphoid leukemias showed 69% (P < .001) and 25% decrease (P < .01) in cell proliferation and 42% and 34% (P < .01) apoptosis induction, respectively. Overall, our results indicate that CAPE and MG-132 had a strong and selective apoptotic effect on tumor cells that may be useful in future treatment of hematological neoplasias. 相似文献
94.
Serruys P Grines C Stone G Garcia E Kiemeney F Morice M Sousa J Hamm C Costantini C Probst P Rutsch W Penn I Fernandez-Aviles F Vandormael M Bartorelli A Bilodeau L Eijgelshoven M 《International journal of cardiovascular interventions》1998,1(1):19-27
Preliminary experience with primary stenting in myocardial infarction has suggested a greater benefit in clinical outcome than has been obtained with direct balloon angioplasty. However, subacute thrombosis (SAT) remains a limitation for this new mode of therapy. In the BENESTENT II Pilot and main trials, the incidence of SAT with the heparin-coated Palmaz-Schatz stent was only 0.15%. Therefore, as a preamble to a large randomized trial, the feasibility and safety of the use of the Heparin-Coated Palmaz-Schatz trade mark Stent in Acute Myocardial Infarction (AMI) was tested in 101 patients enrolled between April and September 1996 in 18 clinical centres. In 101 stent-eligible AMI patients, as dictated by protocol, a heparin-coated stent was implanted. The primary objectives were to determine the in-hospital incidence of major adverse cardiac events (MACE: death, MI, target lesion revascularization) and bleeding complications, while the secondary objectives were the procedural success rate and the MACE, the restenosis and reocclusion rates at 6.5 months. Stent implantation (n 3 129 stents) was successful in 97 patients of the 101 who were included in this trial. During their hospital stay, two patients died and no patient experienced re-infarction, ischaemia prompting re-PTCA or CABG. Four patients suffered a bleeding complication, three major and one minor, of whom three required surgical repair. At 210 days follow-up, 81% of the patients were event free. At 6.5 months restenosis was documented in 18% of the 88 patients who underwent follow-up angiography, including three total occlusions. The results, both with respect to QCA and the occurrence of MACE, compare favourably with studies using elective stenting in both stable and unstable angina patients. As a result of this pilot study, a large randomized trial comparing direct balloon angioplasty with direct stenting in 900 patients with AMI was initiated in December 1996. 相似文献
95.
Nucleotide sequence of the D-loop region of the sperm whale (Physeter macrocephalus) mitochondrial genome 总被引:4,自引:0,他引:4
We have amplified, by the polymerase chain reaction, and have sequenced the
D-loop region of the mitochondrial DNA from the sperm whale (Physeter
macrocephalus). The sperm whale D-loop was aligned with D- loop sequences
from four other cetaceans (Commerson's dolphin, orca, fin whale, and minke
whale) and an out-group (cow). This alignment showed the sperm whale
sequence to be larger than that of other cetaceans. In addition, some
sequence blocks were highly conserved among all six species, suggesting
roles in the functioning of mitochondrial DNA. Other blocks that were
previously reported to be well conserved among cetaceans showed little
sequence conservation with the sperm whale D-loop, which argues against the
functional importance of these sequence blocks in cetaceans.
相似文献
96.
Many experiments show that serotonin (5-HT) controls thyroidal function at hypothalamic level, inhibiting the TRH secretion. The majority of experiments are done in an acute way, consisting of a single serotonin dose injected intraperitoneally (ip) or intracerebroventricularly (ic) with the effect registered after a short time (usually 1 h) as in normal environmental conditions similar to the TSH stimulation test, that consists of transfer of the experimental animals from 30°C to 4°C for 30 min, thus inducing stimulation of the hypothalamus-hypophysis-thyroid axis. The aim of the present research was to study the correlation between 5-HT and the thyroidal function, measuring plasmatic thyroid hormone levels in rats ip treated in chronic (injected daily for 10 days with different doses of 5-HT), and in acute way (after 1 h from a single 2.0 mg/kg bw 5-HT dose) in normal environmental conditions to evidence the serotonin site action activity outside the blood-brain barrier. The results of the chronic experiment show an inhibitory effect of 5-HT, on T3 and T4 plasmatic level, only when it is injected at medium doses (0.2 and 0.4 mg/kg bw for T3, and 0.2 for T4), while the results of the acute experiment do not evidence any modification. These results show that in normal environmental conditions the outside 5-HT site action is active only when the 5-HT is injected chronically at defined doses, probably for a down-regulation phenomenon. 相似文献
97.
98.
99.
Green olives of two different varieties were picked on various dates in August and September from a grove in N. Greece. After a cold storage, they were dipped into, 0, 0.1, 1, and 5% solutions of streptomycin sulphate in tap water plus a spreader-wetter. Oviposition by females of Dacus oleae (Gmelin) preceded or followed the treatment. The percentage of fruit in which larvae could not reach full size within 2 weeks at 25°C was used as a measure of the inhibition of development.Inhibition of larval growth occurred at the 1 and 5% concentrations, and varied with the time between treatment and oviposition. It was low 2 days before oviposition, increased to c. 50% a day or a few hours before, reached a maximum of c. 80% a few hours or a day after, returned to c. 50% 2 days after, and dropped to practically zero 3, 4 and 6 days after oviposition.The results of artificial transfer of eggs and larvae from treated to untreated fruit and vice versa, indicate that streptomycin did not exert its inhibitory effect via the fruit juice ingested by the larva. One possibility would be by contact with the egg and perhaps also the neonate larva at hatching.
Résumé Des olives vertes, de deux variétés différentes, ont été ramassées en août et septembre 1971 dans une olivette de la Grèce du Nord, puis mises au frigidaire jusqu'au jour de chaque expérience.Le traitement consistait en une immersion instantanée des fruits dans des solutions aqueuses de sulfate de streptomycine auxquelles était ajoutée une substance mouillante-dispersante.L'oviposition a eu lieu soit le même jour, soit quelques jours avant ou après le traitement à la streptomycine. L'influence du traitement sur le développement larvaire est exprimé par le pourcentage des olives dans lesquelles les larves n'ont pas pu achever leur développement larvaire dans un délai de deux semaines à environ 25°.Les concentrations à 1 et 5% se sont révélées inhibitrices du développement larvaire, et le degré d'inhibition varie selon le temps écoulé entre le traitement et l'oviposition. L'inhibition est faible lorsque le traitement est appliqué 2 jours avant l'oviposition; elle augmente ensuite pour atteindre environ 50% quand il intervient un jour ou quelques heures avant la ponte. L'inhibition maximum, environ 80%, se produit quand le traitement se place quelques heures ou un jour après la ponte; elle s'abaisse pour devenir presque nulle quand il est retardé 3, 4, et 6 jours après l'oviposition.Des ufs et des larves ont été extraits des olives non traitées et introduits artificiellement dans des olives traitées et vice versa. Le pourcentage des individus qui ont achevé leur développement larvaire indique que la streptomycine n'exerce pas son effet inhibiteur par l'intermédiaire du jus d'olive ingéré par la larve. Une possibilité serait qu'elle agisse par contact avec l'uf et peut-être aussi avec la larve nouveau-née au moment de son éclosion.相似文献
100.
Kwok WK Picioreanu C Ong SL van Loosdrecht MC Ng WJ Heijnen JJ 《Biotechnology and bioengineering》1998,58(4):400-407
The influence of process conditions (substrate loading rate and detachment force) on the structure of biofilms grown on basalt particles in a Biofilm Airlift Suspension (BAS) reactor was studied. The structure of the biofilms (density, surface shape, and thickness) and microbial characteristics (biomass yield) were investigated at substrate loading rates of 5, 10, 15, and 20 kg COD/m3. day with basalt concentrations of 60 g/L, 150 g/L, and 250 g/L. The basalt concentration determines the number of biofilm particles in steady state, which is the main determining factor for the biofilm detachment in these systems. In total, 12 experimental runs were performed. A high biofilm density (up to 67 g/L) and a high biomass concentration was observed at high detachment forces. The higher biomass content is associated with a lower biomass substrate loading rate and therefore with a lower biomass yield (from 0.4 down to 0.12 gbiomass/gacetate). Contrary to general beliefs, the observed biomass detachment decreased with increasing detachment force. In addition, smoother (fewer protuberances), denser and thinner compact biofilms were obtained when the biomass surface production rate decreased and/or the detachment force increased. These observations confirmed a hypothesis, postulated earlier by Van Loosdrecht et al. (1995b), that the balance between biofilm substrate surface loading (proportional to biomass surface production rate, when biomass yield is constant) and detachment force determines the biofilm structure. When detachment forces are relatively high only a patchy biofilm will develop, whereas at low detachment forces, the biofilm becomes highly heterogeneous with many pores and protuberances. With the right balance, smooth, dense and stable biofilms can be obtained. Copyright 1998 John Wiley & Sons, Inc. 相似文献