首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   119篇
  免费   8篇
  2022年   2篇
  2021年   2篇
  2020年   3篇
  2019年   1篇
  2018年   3篇
  2016年   1篇
  2015年   5篇
  2014年   6篇
  2013年   8篇
  2012年   31篇
  2011年   6篇
  2010年   7篇
  2009年   3篇
  2008年   5篇
  2007年   4篇
  2005年   2篇
  2004年   3篇
  2003年   1篇
  2001年   1篇
  2000年   1篇
  1999年   2篇
  1997年   4篇
  1996年   2篇
  1995年   1篇
  1990年   1篇
  1989年   1篇
  1987年   2篇
  1986年   3篇
  1984年   2篇
  1983年   1篇
  1981年   1篇
  1980年   1篇
  1979年   3篇
  1975年   1篇
  1974年   2篇
  1972年   2篇
  1969年   1篇
  1967年   1篇
  1966年   1篇
排序方式: 共有127条查询结果,搜索用时 31 毫秒
1.
Plantlets were regenerated from Alstroemeria Alsaan rhizome tips cultured in vitro on solid and liquid media based on Murashige and Skoog salt formulation. The quality of the cultures was superior when intact rather than longitudinally sliced rhizome tips were used as explants and when a temperature of 8°C rather than 22°C was used at the initiation stage. More roots were produced on rhizome tips containing a rhizome apical meristem than on rhizome sections lacking such a meristem. Most (90%) of the rooted plantlets were successfully acclimatized and developed into true-to-type flowering plants.  相似文献   
2.
The ability of a single injection of killed, intact bacteria to effect an increase in the proliferative rate of hemopoietic stem cells was studied. The total numbers of colony forming units in bone marrow, spleen and peripheral blood as well as the proportion of CFU in cycle was assessed. Splenic CFU were observed to rise exponentially due initially to in situ proliferation and later to proliferation in bone marrow with migration via the blood to the spleen. The results are discussed in the light of current concepts of stem cell regulation.  相似文献   
3.
The seeding efficiency of colony-forming cells from normal, regenerating and velocity-sedimented cycling and non-cycling narrow preparations was compared. Colony-forming cells in cycle were found to exhibit a 50% reduction in splenic seeding when compared to normal marrow or sedimented non-cycling cells. The results of this study indicate that the spleen colony assay underestimates the total number of colony-forming cells by a fraction which is directly related to the number of cells in cycle.  相似文献   
4.
目的:研究大鼠脑缺血/再灌注过程中血流量及与脑组织水含量变化的趋势。方法:选取5只成年SD雄性大鼠(n=5),参照改良Zea-Longa线栓法制备大鼠大脑中动脉缺血/再灌注模型,2 h后拔出线栓。利用PeriCam PSI血流灌注成像系统实时监测大鼠在缺血前及缺血5 min、30 min、1 h、2 h、再灌注5 min、30 min、1 h、2 h、4 h、6 h及24 h的血流灌注量,记录在ROI(感兴趣区)测量的数值。再选取15只成年SD雄性大鼠,分为Control组、缺血2 h、再灌注30 min、4 h及24 h组(n=3)。正常组不做任何处理,实验组按上述线栓法制备MCAO模型。取新鲜脑组织用干湿重法测定其左、右半球的水含量。结果:栓塞时缺血侧血流量逐渐下降,缺血2 h下降最低(P<0.05);再灌注早期血流量恢复较大(P<0.05),30 min时显著下降(P<0.05),4 h明显上升(P<0.05),24 h再次上升(P<0.05)但低于缺血前血流量(P>0.05)。脑组织水含量测量,缺血2 h组和再灌注30 min组与正常组无明显差异(P>0.05);再灌4 h组和再灌24 h组明显增高(P<0.05),且再灌24 h组明显高于再灌4 h组(P<0.05)。结论:大鼠脑缺血/再灌注过程中血流量和脑组织中水含量的变化存在一定的规律,且脑组织中水含量与再灌注过程中血流量的变化有一定关系。  相似文献   
5.
Human disturbance from tourism and other non-consumptive activities in protected areas may be stressful to wildlife. Animals may move away in space or time to avoid human interaction. For species of particular conservation concern, such as Baird's tapirs (Tapirus bairdii) and jaguars (Panthera onca), a better understanding of how they respond to different levels and types of disturbance is needed in order to manage human visitation to parks in ways that minimize negative outcomes for wildlife. We describe the overlap in activity patterns of tapirs, jaguars, and humans at logged and unlogged sites and at places with low versus high human visitation using camera survey data from protected areas of NW Belize, 2013–2016. Tapirs were nocturnal in all study sites, with > 80% of all tapir detections occurring between 1900 hr and 0500 hr. Their activity patterns were not different in unlogged versus logged sites and did not change with increased human traffic. Jaguars were cathemeral across sites but had more nocturnal activity at the site with the most human impact. Activity pattern overlap between tapirs and jaguars did not differ significantly between logged and unlogged sites, nor between areas with low and high human activity. Human traffic increased from 2013 to 2016 at most of the study locations. In conclusion, this camera trap dataset suggests that non-consumptive human disturbance does not alter the activity patterns of tapirs and jaguars in protected areas lacking hunting pressure.  相似文献   
6.
Abstract

Archaeosomes composed of archaeal total polar lipids (TPL) or semi-synthetic analog vesicles have been used as vaccine adjuvants and delivery systems in animal models for many years. Typically administered by intramuscular or subcutaneous injections, archaeosomes can induce robust, long-lasting humoral and cell-mediated immune responses against entrapped antigens and provide protection in murine models of infectious disease and cancer. Herein, we evaluated various archaeosomes for transdermal delivery, since this route may help eliminate needle-stick injuries and needle re-use, and therefore increase patient compliance. Archaeosomes composed of TPL from different archaea (Halobacterium salinarum, Methanobrevibacter smithii, Haloferax volcanii) and various semi-synthetic glycolipid combinations were evaluated for their ability to diffuse across the skin barrier using an ex vivo pig skin model and the results were compared to conventional synthetic ester liposomes. Physicochemical characteristics were determined for selected formulations including vesicle size, size distribution, zeta potential, fluidity, antigen (ovalbumin) incorporation efficiency and release. Archaeosomes, in particular those composed of M. smithii TPL or the synthetic glycolipid sulfated S-lactosylarchaeol (SLA) mixed with uncharged glycolipid lactosyl archaeol (LA), appeared to be effective carriers for ovalbumin, achieving much better antigen distribution and vesicle accumulation in the skin epidermis than conventional liposomes. The enhanced skin permeation of archaeosomes may be attributed to their chemical structure and physicochemical properties such as particle size, surface charge, stability, and fluidity of their lipid bilayer.  相似文献   
7.
The effects of cage fish farming on physico-chemical and bacteriological water quality in Lake Volta, Ghana, were investigated in 2013–2014. Farmed and unfarmed (control) areas of the lake were selected for monitoring. Nutrients, temperature, dissolved oxygen, conductivity, turbidity, pH, total coliforms, Pseudomonas and Vibrio spp. in the water were monitored monthly. Analyses of the water samples were carried out according to standard procedures. Physico-chemical quality of the water in both farm and control sites were within ranges typical of minimally impacted water and did not vary significantly between the two contrasting sites. The bacteriological analysis, however, revealed contamination of the lake water by fish farming. The bacterial counts at the farmed sites were significantly higher (p < 0.05) than those of the control sites, with figures at the farmed sites ranging from 132 to 1 708 cfu 100 ml?1 for total coliforms, 514 to 5 170 cfu 100 ml?1 Pseudomonas spp. and 14 to 516 cfu 100 ml?1 for Vibrio spp. The results suggested that cage fish farming has increased bacterial loads in the lake water, but has had minimal impact on its physico-chemical quality.  相似文献   
8.
This paper presents the work conducted on the chemical constituents of some common and widely distributed halophyte taxa from Cyprus with the aim that these studies will help in the evaluation of halophytes for different economical purposes. The plant species of Crithmum maritimum L., Limbarda crithmoides (L.) Dumort, Atriplex portulacoides L., Salsola kali L., Atriplex halimus L., Limonium oleifolium Mill., L. meyeri (Boiss.) Kuntze; and Tetraena alba (L.f.) Beier & Thulin were collected in the middle of July. The shoot tissue and leaf samples were collected from the natural habitats and left for drying under air circulation followed by placing them in oven at 60 °C for 96 hours. The material was crushed using mortar and pestle and subjected to an analysis of macro- and micro-nutrients and biochemical compounds. K+/Na+ in the leaf tissues of the dicot species showed relatively high values depicting their behavior as Na+ includes but very low Cl- levels were recorded. Out of the species investigated here in 4 TFAA content was rather high. Values ranging from 0.5% to 1% dry weight were exhibited in one species. However, only 3 species showed very low TFAA values. Later may be due to low nitrogen availability in their environment. The phenetic analyses of eight halophyte species performed on the data matrix using Ntsys-pc program version 2.1 revealed that, cluster analysis of the overall results obtained here leads to 2 clusters. This discrimination appears to be as a result of their different abilities to accumulate either proline or glycine betaine.  相似文献   
9.
Halieutopsis bathyoreos Bradbury, 1988 (Lophiiformes: Ogcocephalidae), previously described only on the basis of the holotype (62.6mm in standard length) from the central North Pacific, is redescribed on the basis of the holotype and six additional specimens (41.2–68.7mm in standard length) collected from the western South Pacific, off Papua New Guinea, and the western North Pacific, including the Japanese Archipelago. Halieutopsis bathyoreos is distinguished from its congeners by having a shelflike rostrum extending anteriorly well beyond the mouth, a dorsal escal lobe slightly bisected ventrally, an illicial cavity square in outline and completely visible in ventral view, and lacking tubercles on the ventral surface of the disk. The following characters are newly added to the diagnoses of this species: rostrum width 21–29% of head length, tubercles on the dorsal surface of the disk about half the diameter of those on the lateral margin, and 13–15 large lateral-line scales on the tail.  相似文献   
10.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号