全文获取类型
收费全文 | 570篇 |
免费 | 12篇 |
国内免费 | 54篇 |
专业分类
636篇 |
出版年
2022年 | 6篇 |
2021年 | 5篇 |
2020年 | 9篇 |
2019年 | 4篇 |
2016年 | 8篇 |
2015年 | 4篇 |
2014年 | 9篇 |
2013年 | 27篇 |
2012年 | 29篇 |
2011年 | 23篇 |
2010年 | 32篇 |
2009年 | 36篇 |
2008年 | 33篇 |
2007年 | 19篇 |
2006年 | 23篇 |
2005年 | 23篇 |
2004年 | 12篇 |
2003年 | 7篇 |
2002年 | 4篇 |
2001年 | 16篇 |
2000年 | 5篇 |
1998年 | 19篇 |
1997年 | 10篇 |
1996年 | 5篇 |
1995年 | 8篇 |
1994年 | 8篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1985年 | 8篇 |
1984年 | 4篇 |
1982年 | 3篇 |
1980年 | 3篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1973年 | 3篇 |
1959年 | 8篇 |
1958年 | 16篇 |
1957年 | 13篇 |
1956年 | 25篇 |
1955年 | 14篇 |
1954年 | 10篇 |
1953年 | 20篇 |
1952年 | 13篇 |
1951年 | 15篇 |
1950年 | 14篇 |
排序方式: 共有636条查询结果,搜索用时 0 毫秒
101.
102.
103.
VALRIE LE MAIRE ALAIN HERNVANN HERV LE MARECHAL OHVANESSE G. EKINDJIAN CHRISTIAN AUSSEL 《Cell biology international》1997,21(7):455-460
Given the importance of interleukin-1 in both rheumatic diseases and the modulation of cell metabolic activities, we studied the action of this cytokine on the neutral amino acid transport A system on rheumatoid synovial cells. In these cells IL-1 (1ng/ml) induced amino transport stimulation from 5min to 5h. This effect was obtained only after a starvation period. No concentration-related effect was found for IL-1-stimulated MeAIB uptake, and the IL-1-mediated MeAIB uptake stimulation is independent of protein synthesis. Neosynthesis or post-translational maturation of protein transport is a prerequisite for obtaining this effect. In conclusion, rheumatoid synovial cells exhibit a higher sensitivity for IL-1 than osteoarthritic ones, probably related to their intense metabolic activity. 相似文献
104.
应越南国家植物保护研究院的邀请 ,受我国科技部的委派 ,我们于 2 0 0 1年 1 1~ 1 2月赴越进行“小菜蛾化学信息素的分离鉴定及应用研究”。河内地处热带 ,光照充足 ,雨量充沛 ,气候湿润 ,郊区拥有数百平方公里的蔬菜基地 ,种植着各式各样的蔬菜 ,长势旺盛 ,所产各类蔬菜主要用于出口 ,但虫害较重。在进行小菜蛾PlutellaxylostellaL .化学信息素研究[1] 的同时 ,我们对主要蔬菜品种上的昆虫群落的组成及优势种昆虫进行了考查和分析。1 材料与方法选取 1 0多种蔬菜作为调查对象 ,每种蔬菜样地面积≥ 6 6 6× 2m2 ,以五点取样法选取 5个样… 相似文献
105.
P. HENRY§ G. LE LAY J. GOUDET A. GUISAN . JAHODOVÁ†‡ G. BESNARD¶ 《Molecular ecology》2009,18(13):2819-2831
The giant hogweed ( Heracleum mantegazzianum ) has successfully invaded 19 European countries as well as parts of North America. It has become a problematic species due to its ability to displace native flora and to cause public health hazards. Applying population genetics to species invasion can help reconstruct invasion history and may promote more efficient management practice. We thus analysed levels of genetic variation and population genetic structure of H. mantegazzianum in an invaded area of the western Swiss Alps as well as in its native range (the Caucasus), using eight nuclear microsatellite loci together with plastid DNA markers and sequences. On both nuclear and plastid genomes, native populations exhibited significantly higher levels of genetic diversity compared to invasive populations, confirming an important founder event during the invasion process. Invasive populations were also significantly more differentiated than native populations. Bayesian clustering analysis identified five clusters in the native range that corresponded to geographically and ecologically separated groups. In the invaded range, 10 clusters occurred. Unlike native populations, invasive clusters were characterized by a mosaic pattern in the landscape, possibly caused by anthropogenic dispersal of the species via roads and direct collection for ornamental purposes. Lastly, our analyses revealed four main divergent groups in the western Swiss Alps, likely as a consequence of multiple independent establishments of H. mantegazzianum . 相似文献
106.
JEFF A. JOHNSON† RUTH E. TINGAY‡ MELANIE CULVER§ FRANK HAILER¶ MICHÈLE L. CLARKE†† DAVID P. MINDELL‡‡ 《Molecular ecology》2009,18(1):54-63
The critically endangered Madagascar fish-eagle ( Haliaeetus vociferoides ) is considered to be one of the rarest birds of prey globally and at significant risk of extinction. In the most recent census, only 222 adult individuals were recorded with an estimated total breeding population of no more than 100–120 pairs. Here, levels of Madagascar fish-eagle population genetic diversity based on 47 microsatellite loci were compared with its sister species, the African fish-eagle ( Haliaeetus vocifer ), and 16 of these loci were also characterized in the white-tailed eagle ( Haliaeetus albicilla ) and the bald eagle ( Haliaeetus leucocephalus ). Overall, extremely low genetic diversity was observed in the Madagascar fish-eagle compared to other surveyed Haliaeetus species. Determining whether this low diversity is the result of a recent bottleneck or a more historic event has important implications for their conservation. Using a Bayesian coalescent-based method, we show that Madagascar fish-eagles have maintained a small effective population size for hundreds to thousands of years and that its low level of neutral genetic diversity is not the result of a recent bottleneck. Therefore, efforts made to prevent Madagascar fish-eagle extinction should place high priority on maintenance of habitat requirements and reducing direct and indirect human persecution. Given the current rate of deforestation in Madagascar, we further recommend that the population be expanded to occupy a larger geographical distribution. This will help the population persist when exposed to stochastic factors (e.g. climate and disease) that may threaten a species consisting of only 200 adult individuals while inhabiting a rapidly changing landscape. 相似文献
107.
马鹿茸血酶解肽体内免疫功能及抗氧化功能关系的研究 总被引:1,自引:0,他引:1
本文分别选用由木瓜蛋白酶水解天山马鹿茸血获得的肽Ⅰ、肽Ⅱ以及原血为受试样品,研究天山马鹿茸血及其酶解肽对小鼠免疫功能和抗氧化功能的影响,其中肽Ⅰ、肽ⅡDH分别为18.1%、12.2%时,清除OH·能力最强,清除率为50.8%。分别测定了脏器指数,脾细胞增殖实验,血清中溶血素和抗体生成细胞的含量以及小鼠血清总抗氧化能力、SOD活力和MDA含量。结果表明:与对照组相比较,肽Ⅱ组能极显著提高小鼠体液和细胞免疫功能,加强小鼠的抗氧化功能(P〈0.01或P〈0.05)。此外,具有较强抗氧化活性的肽显示出了很强的免疫活性(P〈0.05)。 相似文献
108.
MARIE-AGNÈS TRAVERS OLIVIER BASUYAUX‡ NELLY LE GOÏC† SYLVAIN HUCHETTE JEAN-LOUIS NICOLAS§ MARCEL KOKEN† CHRISTINE PAILLARD† 《Global Change Biology》2009,15(6):1365-1376
Since 1998, Haliotis tuberculata mass mortalities have been occurring regularly in wild abalone populations in France during their reproductive period and in conjunction with seawater summer temperature maxima and Vibrio harveyi presence. To confirm the importance of bacterial exposure, temperature and reproductive status on abalone susceptibility, experimental infections via bath exposure were performed using abalone ranging from immature to reproductively mature. Ripe abalone were more susceptible to the bacterium than immature specimens ( P <0.001), and a difference of only 1 °C in temperature had a highly significant impact on the mortalities ( P <0.001). The natural mortalities that were surveyed during summer 2007 confirmed that recent epidemic losses of European abalone appeared in conjunction with host reproductive stress, elevated temperatures and presence of the pathogen V. harveyi . In view of the elevation of the mean summer temperatures observed in Brittany and Normandy over the last 25 years, this temperature-dependent vibriosis represents a new case of emerging disease associated with global warming. 相似文献
109.
梨分子遗传图谱构建及生长性状的QTL分析 总被引:11,自引:1,他引:10
利用鸭梨和京白梨杂交得到的F1(145株)实生苗为作图群体,通过对AFLP和SSR两种分子标记的遗传连锁分析,应用Joinmap 3.0作图软件,368个AFLP标记、34个SSR标记构建了分属18个连锁群的梨分子遗传连锁图谱,各连锁群的LOD值在4.0~7.0范围之间,图谱总长度覆盖梨基因组1395.9cM,平均图距为3.8cM.采用区间作图法,对该群体与生长性状相关的调查数据进行QTL分析,检测到与新梢生长量、新梢茎粗、节间长度、节间数量、树干径、树高及皮孔密度7个农艺性状连锁的QTL位点35个,其中主效QTL位点11个(LOD≥3.5).与生长性状相关的农艺性状QTL位点多集中在LG16连锁群上. 相似文献
110.
从海栖热袍菌中克隆出编码热稳定性的纤维素酶基因,以热激载体pHsh为表达质粒,构建重组质粒phsh—Ceff4,并转化至大肠杆菌中进行表达。基因表达产物通过热处理和离子交换层析,重组酶纯度达电泳纯。对纯化的重组酶酶学性质研究表明,最适反应温度85℃,最适反应pH4.6,pH4.5—6.0之间酶的相对酶活在80%以上。Co^2+对酶活性有促进作用,Ca^2+、Mg^2+、Zn^2+不影响酶活性,而Cu^2+、Ni^2+、Mn^2+对酶活性有抑制作用。 相似文献