全文获取类型
收费全文 | 643篇 |
免费 | 23篇 |
国内免费 | 46篇 |
专业分类
712篇 |
出版年
2022年 | 5篇 |
2021年 | 5篇 |
2020年 | 11篇 |
2019年 | 6篇 |
2016年 | 10篇 |
2015年 | 9篇 |
2014年 | 13篇 |
2013年 | 29篇 |
2012年 | 35篇 |
2011年 | 29篇 |
2010年 | 34篇 |
2009年 | 36篇 |
2008年 | 36篇 |
2007年 | 24篇 |
2006年 | 23篇 |
2005年 | 28篇 |
2004年 | 14篇 |
2003年 | 11篇 |
2002年 | 5篇 |
2001年 | 15篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1998年 | 19篇 |
1997年 | 12篇 |
1996年 | 7篇 |
1995年 | 8篇 |
1994年 | 9篇 |
1993年 | 5篇 |
1992年 | 7篇 |
1991年 | 8篇 |
1989年 | 8篇 |
1988年 | 9篇 |
1987年 | 6篇 |
1985年 | 11篇 |
1984年 | 7篇 |
1982年 | 5篇 |
1980年 | 4篇 |
1979年 | 8篇 |
1977年 | 7篇 |
1976年 | 4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712条查询结果,搜索用时 15 毫秒
71.
植物在对抗昆虫的长期进化过程中形成了自我防御机制,能够产生特异的抗性蛋白来应对昆虫的取食。该文用机械损伤模拟害虫取食,研究和 对比了油菜(Brassica napus cv. Westar)在机械损伤前后可溶性总蛋白的含量变化并试图通过蛋白质组学技术来检测可能发生变化的蛋白质。 蛋白质定量检测发现,同一植株同一叶片损伤前后可溶性总蛋白含量差异显著,损伤后蛋白表达量增高。 蛋白质双向凝胶电泳及其差异显示分 析损伤前后的蛋白质组,表明有8个蛋白质点发生明显的上调或下调。选择其中2个差异蛋白点经过MALDI-TOF质谱鉴定,它们分别是Rubisco小 亚基前体、果糖-1,6-二磷酸醛缩酶和粪卟啉-3-氧化酶,这些蛋白质可能在油菜叶片应答机械损伤过程中对维持植物的生理功能起到重要作用 。 相似文献
72.
Proteolytic activity in anther extracts of fertile and cytoplasmic male sterile petunia 总被引:1,自引:0,他引:1 下载免费PDF全文
Proteolytic activity is compared in anther extracts from Petunia parodii fertile and cytoplasmic male sterile lines. It is characterized relative to developmental stage of the anthers, effect of variable incubation times, pH of isolation buffers, and degradation of marker proteins. In fertile anthers, proteolytic activity increases at the end of microsporogenesis and peaks early in microgametogenesis. Degradation is most severe in extracts of fertile anthers and in high molecular weight proteins and reaches its maximum within 20 minutes. Degradation of marker proteins is greatest at pH 5.6 to 8.0 in fertile anther extracts and is eliminated under strong acid conditions (pH 2.8 to 4.0) in both fertile and cytoplasmic male sterile anther extracts. Marker proteins degrade more severely in extracts of fertile anthers; however, the order of substrate sensitivity—myosin > phosphorylase b > bovine serum albumin and ovalbumin > β-galactosidase—is the same in extracts from fertile and cytoplasmic male sterile anthers. 相似文献
73.
本研究采用毛细管电泳技术,构建并优化了荧光标记复合PCR同时扩增多个微卫星位点。主要过程为:首先根据设计所扩增微卫星位点的期望长度,将9个微卫星位点分成两组,5个位点用FAM(蓝色)标记,4个位点用HEX(绿色)标记;两种荧光类型分组优化,用琼脂糖胶电泳检测。其次,荧光标记的复合PCR扩增8个中华绒螯蟹样品的9个微卫星位点,采用ABI3730xl毛细管电泳检测,以ROX500(红色)为长度标准物,结果经Genemapper3.5软件 分析,检测结果表明毛细管电泳检测荧光标记复合PCR产物不仅精确读取微卫星位点的长度(分辨率高达1bp),还能区分微卫星位点复制时滑链所引起的“回声斑”;调整各微卫星位点引物比列使所有位点扩增强弱均匀。最后,逐一检测复合PCR基本参数(dNTP浓度、 PCR程序和模版DNA用量)对复合PCR产物的影响,优化PCR。结果表明通过毛细管电泳检测荧光标记复合PCR产物来读取微卫星位点的基因型具有精确性、高效性和稳定性。 相似文献
74.
S. LUYSSAERT I. INGLIMA M. JUNG A. D. RICHARDSON M. REICHSTEIN D. PAPALE S. L. PIAO E. ‐D. SCHULZE L. WINGATE G. MATTEUCCI L. ARAGAO M. AUBINET C. BEER C. BERNHOFER K. G. BLACK D. BONAL J. ‐M. BONNEFOND J. CHAMBERS P. CIAIS B. COOK K. J. DAVIS A. J. DOLMAN B. GIELEN M. GOULDEN J. GRACE A. GRANIER A. GRELLE T. GRIFFIS T. GRÜNWALD G. GUIDOLOTTI P. J. HANSON R. HARDING D. Y. HOLLINGER L. R. HUTYRA P. KOLARI B. KRUIJT W. KUTSCH F. LAGERGREN T. LAURILA B. E. LAW G. LE MAIRE A. LINDROTH D. LOUSTAU Y. MALHI J. MATEUS M. MIGLIAVACCA L. MISSON L. MONTAGNANI J. MONCRIEFF E. MOORS J. W. MUNGER E. NIKINMAA S. V. OLLINGER G. PITA C. REBMANN O. ROUPSARD N. SAIGUSA M. J. SANZ G. SEUFERT C. SIERRA M. ‐L. SMITH J. TANG R. VALENTINI T. VESALA I. A. JANSSENS 《Global Change Biology》2007,13(12):2509-2537
Terrestrial ecosystems sequester 2.1 Pg of atmospheric carbon annually. A large amount of the terrestrial sink is realized by forests. However, considerable uncertainties remain regarding the fate of this carbon over both short and long timescales. Relevant data to address these uncertainties are being collected at many sites around the world, but syntheses of these data are still sparse. To facilitate future synthesis activities, we have assembled a comprehensive global database for forest ecosystems, which includes carbon budget variables (fluxes and stocks), ecosystem traits (e.g. leaf area index, age), as well as ancillary site information such as management regime, climate, and soil characteristics. This publicly available database can be used to quantify global, regional or biome‐specific carbon budgets; to re‐examine established relationships; to test emerging hypotheses about ecosystem functioning [e.g. a constant net ecosystem production (NEP) to gross primary production (GPP) ratio]; and as benchmarks for model evaluations. In this paper, we present the first analysis of this database. We discuss the climatic influences on GPP, net primary production (NPP) and NEP and present the CO2 balances for boreal, temperate, and tropical forest biomes based on micrometeorological, ecophysiological, and biometric flux and inventory estimates. Globally, GPP of forests benefited from higher temperatures and precipitation whereas NPP saturated above either a threshold of 1500 mm precipitation or a mean annual temperature of 10 °C. The global pattern in NEP was insensitive to climate and is hypothesized to be mainly determined by nonclimatic conditions such as successional stage, management, site history, and site disturbance. In all biomes, closing the CO2 balance required the introduction of substantial biome‐specific closure terms. Nonclosure was taken as an indication that respiratory processes, advection, and non‐CO2 carbon fluxes are not presently being adequately accounted for. 相似文献
75.
Possible existence of large-scale brood sex-ratio manipulation in Eurasian Oystercatchers 总被引:1,自引:0,他引:1
S. E. A. LE V. DIT DURELL† 《Functional ecology》2006,20(3):486-490
76.
目的研究乳酸菌结合小鼠派伊尔结(PP)的性质,确定乳酸菌黏附小鼠PP的影响因子。方法测定10株荧光标记的乳酸菌对PP组织切片黏附性,分析细菌表面疏水性和酵母、红细胞凝集性与黏附性的关系。结果凝集酵母、红细胞能力强的乳酸菌,PP黏附性强。除嗜酸乳杆菌(L.acidophilm)外,其他9株乳酸菌的表面疏水性与凝集酵母、红细胞的能力呈显著的负相关性(r=-0.60和r=-0.53,P〈0.05)。L.acidophilm黏附PP的能力最强。L.acidophilm黏附PP能力和红细胞凝集性均可被D(+)-甘露糖、D(+)-半乳糖抑制。结论乳酸菌黏附PP的能力受疏水性和表面特异性凝集素的影响。L.acidophilm表面D(+)-甘露糖、D(+)-半乳糖特异性凝集素可能参与黏附PP的过程。 相似文献
77.
78.
79.
SARAH E.A. LE V. DIT DURELL JOHN D. GOSS-CUSTARD RALPH T. CLARKE & SELWYN McGRORTY 《Ibis》2000,142(1):132-138
80.
Prevost, I. and Le PageDegivry, M. Th. 1985. Changesin absicisic acid content in axis and cotyledons of developingPhaseolus vulgaris embryos and their physiological consequences.J.exp. Bot. 36: 19001905.Changes in abscisic acid (ABA)content with time were measured in embryonic axes and in cotyledonsof Phaseolus vulgaris embryos using a radioimmunoassay.During embryogenesis, a similar pattern was observed in bothtissues: ABA increased to a maximum 29 d after an thesis, followedby a decrease as the seed matured. The level of ABA in the cotyledonswas always much higher than that in the axes. In in vitro cultures,the duration of the lag phase before germination of isolatedembryonic axes increased with ABA content. The presence of cotyledonsalways lengthened the lag phase; longer lag phases were associatedwith greater concentrations of ABA in the cotyledons. Moreoverthe presence of cotyledons stimulated the growth of seedlings. Key words: ABA distribution, embryo maturation, axis and embryo germinability 相似文献