全文获取类型
收费全文 | 466篇 |
免费 | 44篇 |
国内免费 | 655篇 |
出版年
2022年 | 1篇 |
2021年 | 9篇 |
2020年 | 3篇 |
2019年 | 7篇 |
2018年 | 21篇 |
2017年 | 14篇 |
2016年 | 7篇 |
2015年 | 33篇 |
2014年 | 73篇 |
2013年 | 76篇 |
2012年 | 5篇 |
2011年 | 3篇 |
2010年 | 8篇 |
2009年 | 17篇 |
2008年 | 108篇 |
2007年 | 58篇 |
2006年 | 23篇 |
2005年 | 122篇 |
2004年 | 66篇 |
2003年 | 6篇 |
2002年 | 23篇 |
2001年 | 52篇 |
2000年 | 15篇 |
1999年 | 52篇 |
1998年 | 49篇 |
1997年 | 40篇 |
1996年 | 48篇 |
1995年 | 56篇 |
1994年 | 27篇 |
1993年 | 32篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1985年 | 2篇 |
1980年 | 1篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1964年 | 2篇 |
1959年 | 6篇 |
1958年 | 11篇 |
1957年 | 11篇 |
1956年 | 9篇 |
1955年 | 7篇 |
1954年 | 13篇 |
1953年 | 5篇 |
1952年 | 13篇 |
1951年 | 7篇 |
1950年 | 6篇 |
1949年 | 4篇 |
1948年 | 6篇 |
排序方式: 共有1165条查询结果,搜索用时 31 毫秒
101.
Jun-Huan ZHANG Wei-Dong HUANG Yue-Ping LIU Qiu-Hong PAN 《植物学报(英文版)》2005,47(8):959-970
Leaves from annual young grape plants (Vitis vinifera L. cv. Jingxiu) were used as experimental materials. The ultrastructural characteristics of mesophyll cells in chilling-treated plants after heat acclimation (HA) and in heat-treated plants after cold acclimation (CA) were observed and compared using transmission electron microscopy. The results showed that slight injury appeared in the ultrastructure of mesophyll cells after either HA (38℃ for 10 h) or CA (8℃ for 2.5 d), but the tolerance to subsequent extreme temperature stress was remarkably improved by HA or CA pretreatment. The increases in membrane permeability and malondialdehyde concentration under chilling (0℃) or heat (45℃) stress were markedly inhibited by HA or CA pretreatment. The mesophyll cells of plants not pretreated with HA were markedly damaged following chilling stress. The chloroplasts appeared irregular in shape, the arrangement of the stroma lamellae was disordered, and no starch granules were present. The cristae of the mitochondria were disrupted and became empty. The nucleus became irregular in shape and the nuclear membrane was digested. In contrast, the mesophyll cells of HA-pretreated plants maintained an intact ultrastructure under chilling stress. The mesophyll cells of control plants were also severely damaged under heat stress. The chloroplast became round in shape, the stroma lamellae became swollen, and the contents of vacuoles formed clumps. In the case of mitochondria of control plants subjected to heat stress, the outer envelope was digested and the cristae were disrupted and became many small vesicles. Compared with cellular organelles in control plants, those in CA plant cells always maintained an integrated state during whole heat stress, except for the chloroplasts, which became round in shape after 10 h heat stress. From these data, we suggest that the stability of mesophyll cells under chilling stress can be increased by HA pretreatment. Similarly, CA pretreatment can protect chloroplasts, mitochondria, and the nucleus against subsequent heat stress; thus, the thermoresistance of grape seedlings was improved. The results obtained in the present study are the first, to our knowledge, to offered cytological evidence of cross-adaptation to temperature stresses in grape plants. 相似文献
102.
Population dynamics of the oriental fruit fly, Bactrocera dorsalis (Diptera: Tephritidae) in the Kunming area,southwestern China 总被引:5,自引:0,他引:5
HUI YE JIAN-HONG LIU 《Insect Science》2005,12(5):387-392
Population dynamics of Bactrocera dorsalis Hendel (Diptera: Tephritidae) were studied through pheromone trapping over 4 years (1997, 1999, 2000, 2003) in the Kunming region, a high plateau area in southwestern China. B. dorsalis immigrates from southern Yunnan to Kunming each year, and occurs during early May through November. Annual trap captures recorded an increase in the B. dorsalis populations from May to July, when they peaked in abundance, and a decline until November. No flies were detected from November to April. The fruit flies had two generations. There was considerable overlapping due to the continuous arrival of immigrating flies during the summer months. Annual capture rates were significantly related to numbers of flies caught in July when peak captures were recorded; whereas the peak captures, in turn, positively depended on numbers of flies recorded in May, the first month of fly appearance in the current year. It suggested that the annual population abundance was mainly dependent on the size of the initial emigrating population. A daily average temperature of 18℃ was probably the threshold temperature required for the flies to undertake long-range dispersal, which partially explained the start of the fly in May each year on this high plateau. Under field conditions, the fruit flies can withstand 13℃ as a daily average temperature. No flies were recorded in any of the study years at a daily temperature colder than 10 ℃. 相似文献
103.
Mapping of a Wheat Resistance Gene to Yellow Mosaic Disease by Amplified Fragment Length Polymorphism and Simple Sequence Repeat Markers 总被引:3,自引:0,他引:3
Wei-Hua LIU Huan NIE Zhen-Tian HE Xiu-Lan CHEN Yue-Peng HAN Jin-Rong WANG Xin LI Cheng-Gui HAN Jia-Lin YU 《植物学报(英文版)》2005,47(9):1133-1139
Wheat (Triticum aestivum L.) yellow mosaic virus (WYMV) is transmitted by a fungal vector through soil and causes serious wheat yield losses due to yellow mosaic disease, with yellow-streaked leaves and stunted plants. In the present study, the amplified fragment length polymorphisms (AFLP) and simple sequence repeat (SSR) were used to identify the molecular linkages with the resistance gene against WYMV. Bulked segregant analysis was performed with an F2 population derived from the cross of cultivar Ningmai 9 (resistant) × cultivar Yangmai 10 (susceptible). By screening among the resistant or susceptible parents, the F2 pools and the individuals in the F2 population with 64 combined selective AFLP primers (EcoRI/MseI) or 290 reported SSR primers, a polymorphic DNA segment (approximately 120 bp) was amplified using the primer pair E2/M5, and an SSR marker (approximately 180 bp) was located on wheat chromosome 2A using the primer Xgwm328. Analysis with MAPMAKER/Exp Version 3.0b (Whitehead institute for Biomedical Research, Cambridge, MA, USA) indicated that these two markers were dominantly associated with the resistance gene at distances of 5.4 cM or 17.6 cM, respectively. The resistance gene to WYMV derived from Ningmai 9, is temporarily named YmNM, and was mapped to wheat chromosome 2A. 相似文献
104.
血管中白细胞等的粘附、聚集问题能够影响微循环的血流速度,是损伤血管内皮细胞乃至形成血栓的主要因素之一。在内毒素注射大白鼠的随机、对照实验中,发现电磁水能够减轻内毒素所致的炎症刺激,并能够降低白、红细胞和血小板的粘附、聚集,能降低白细胞的渗出,能提高红细胞的电泳率,能抑制血流速度的减慢和能够减轻血管内皮细胞的损伤。t检验,差异显著(P<0.01)以及差异明显(P<0.05)。揭示电磁水能够提高血细胞和血管内皮细胞的表面负电荷密度,并可以减轻外因(如,内毒素)对体内细胞和血管的损伤。说明电磁水能够改善微循环,维系正常血流和防止血栓形成。 相似文献
105.
Li YANG Jiang CHEN Catherine C. Y. CHANG Xin-Ying YANG Zhen-Zhen WANG Ta-Yuan CHANG and Bo-Liang LI* State Key Laboratory of Molecular Biology Institute of Biochemistry Cell Biology Shanghai Institutes for Biological Sciences the Chinese Academy of Sciences Shanghai China Department of Biochemistry Dartmouth Medical School Hanover NH USA 《Acta biochimica et biophysica Sinica》2004,(4)
Acyl-coenzyme A:cholesterol acyltransferase (ACAT)is an integral membrane protein, which is mainly locatedin rough endoplasmic reticulum (ER), and is responsiblefor catalyzing the intracellular formation of cholesterylester from cholesterol and long-chain fatty acyl-coenzymeA [1,2]. Human ACAT1 cDNA K1 was firstly cloned andfunctionally expressed in 1993 [3]. Further studies withspecific anti-ACAT1 antibody (DM10) illustrated that onemajor 50 kD ACAT1 protein was expressed in various… 相似文献
106.
张更谦 王艳 张艳霞 徐晓莉 邢小平 王英元 贠克明ZHANG Geng-Qian WANG Yan ZHANG Yan-Xia XU Xiao-Li XING Xiao-Ping WANG Ying-Yuan YUN Ke-Ming 《遗传》2004,26(3):0-297
为了应用更多的Y染色体特异性STR基因座以用于法医学和人类遗传学研究,本文用PCR结合PAGE技术检测128例山西汉族无关男性DYS605等位基因分布状况。结果显示:山西地区汉族男性DYS605基因座观察到22,21,20,19,18共5个等位基因,基因频率分别为0.0156;0.1797;0.4531;0.2891;0.0625。等位基因20和19之间的电泳距离在非变性胶上非常接近,要有足够的电泳距离才能区分。测序表明该基因座包括3个串联重复区,其中一个为可变重复区。20例女性DNA未发现扩增产物。Abstract: We study the polymorphism at DYS605 ,a new tetranucleotide Y-STR locus,in a Chinese Han population of Shanxi to meet the need of more genetic markers in forensic practice and genetic analysis. DNA were extracted from 128 unrelated male venous blood, and amplified using GDB primers. PCR products were detected using non-denaturing polyacrylamide gel electrophoresis and silver staining. Five alleles named 22,21,20,19,18 were observed with frequency of 0.0156;0.1797;0.4531;0.2891;0.0625. PCR products were not found in female DNA. Using a long enough gel for a long electrophoresis time is strongly encouraged because the rung between allele 20 and allele19 is smaller than expected. Allele sequences show that the repetitive units of DYS605 were composed with the variant units and non-variant units. 相似文献
107.
此文介绍了一种非同位素简单快速的反向Northern 筛选方法。采用非同位素法标记探针,操作简便,不涉及污染环境。在杂交过程中采用三次校正,结果可靠,重复性好。该方法能有效地,高通量地验证差异表达基因。Abstract: In this paper, a simple, rapid and safe method of Reverse Northern was introduced. A non-radioactive labeling system was used to label the probe. During the process, the quality of probe was normalized three times to rule out the possibility of false results. Samples were dotted as microarray and were hybridized effectively. The method is effective and expected to be widely used in laboratories. 相似文献
108.
王吉振 储明星 王爱国 李宁 傅金恋 谢芳 陈国宏WANG Ji-Zhen CHU Ming-Xing WANG Ai-Guo LI Ning FU Jin-Lian XIE Fang CHEN Guo-Hong 《遗传》2004,26(5):637-647
分析了4个微卫星基因座BM143、OarHH35、OarAE101、BMS2508在7个绵羊群体(小尾寒羊、湖羊、乌珠穆沁羊、萨福克羊、多赛特羊、夏洛来羊、多赛特公羊×小尾寒羊母羊F1代杂种羊)286只绵羊中的遗传多态性。结果表明,这4个微卫星标记在7个绵羊群体中的等位基因数分别为9、11、14和9,其多态信息含量/有效等位基因数/杂合度分别为0.7073/3.7231/0.7314、0.8267/6.4399/0.8447、0.5743/2.5178/0.6028、0.6172/3.0712/0.6744,其中OarHH35的遗传变异最大,OarAE101最小。7个绵羊群体中小尾寒羊的遗传变异最大,湖羊的最小。基于Nei氏DA距离和DS标准遗传距离,采用UPGMA方法构建了系统发生树。该发生树将中国地方品种(小尾寒羊、乌珠穆沁羊、湖羊)和法国的夏洛来羊归为一类,将F1杂种羊、英国品种(萨福克羊和多赛特羊)归为另一类。绵羊微卫星基因分型技术为检查品种(群体)之间的遗传关系提供了一个有用的工具。
Abstract:The genetic polymorphisms of four microsatellite loci BM143,OarHH35,OarAE101,and BMS2508 were analyzed in 286 sheep of seven sheep populations (Small Tail Han sheep, Hu sheep, Ujumqin sheep, Suffolk sheep, Dorset sheep, Charolais sheep, F1 of Dorset♂ × Small Tail Han sheep♀). The numbers of alleles for BM143,OarHH35,OarAE101,and BMS2508 are 9, 11, 14 and 9 in seven sheep populations, respectively. The polymorphism information content/number of effective alleles/ heterozygosity of BM143,OarHH35,OarAE101 and BMS2508 were 0.7073/3.7231/0.7314, 0.8267/6.4399/0.8447,0.5743/2.5178/0.6028,0.6172/3.0712/0.6744
in 286 sheep, respectively. The results revealed the greatest genetic variation at OarHH35 locus and the lowest at OarAE101, the greatest genetic variation in Small Tail Han sheep and the lowest in Hu sheep among seven sheep populations. In the unweighted pair group method with arithmetic mean (UPGMA) dendrograms based on Nei's DA distance and Nei's DS standard genetic distance, the Chinese native breeds (Small Tail Han sheep, Ujumqin sheep, Hu sheep) were grouped together, then with Charolais sheep. The F1 crossbred sheep, and the two British native sheep (Suffolk sheep, Dorset sheep) also clustered together. Microsatellite genotyping in sheep provided a useful tool for examining the genetic relationships among breeds(populations). 相似文献
109.
Identification of binding epitope of a monoclonal antibody (Z12) against human TNF-α using computer modeling and deletion mutant technique 总被引:1,自引:1,他引:0
ZHANG Wei FENG Jiannan & SHEN Beifen Beijing Basic Medical Institute Beijing China 《中国科学:生命科学英文版》2004,(3)
Humantumornecrosisfactor-a(hTNF-a)isanunglycosylated,pleiotropiccytokinewithnumerousbiologicaleffectsincludingcytotoxicandproinflam-matoryactivities[1].Asrevealedbytheresearchwithmurinemodel,hTNF-playedakeyroleinmanydis-easessuchasrheumatoidarthritis,multiplesclerosisandinflammatoryboweldisease[2],andtherefore,be-cameausefultargetoftherapyforthediseases.Neu-tralizingmonoclonalantibody(mAb)againsthTNF-,asanagentblockinghTNF-activity,hasbeenusedfortherapyofthosediseasesabove[3,4].ThemAb,de… 相似文献
110.
ZHENG Junfang LIU Guirong ZHU Wanfu ZHOU Yuguang & LIU Shulin . Department of Microbiology School of Basic Medical Sciences Peking University Beijing China . Department of Microbiology Infectious Diseases University of Calgary Calgary ABTN N Canada . Institute of Microbiology Chinese Academy of Sciences Beijing China 《中国科学:生命科学英文版》2004,47(3):268-278
Rhizobiaareagriculturallyandenvironmentallyimportantbacteria.Theirsymbiosiswithleguminousplantsisresponsibleformostoftheatmosphericni-trogenfixedonland.Classificationofthesebacteriabasedontheirnaturalrelationshipswillpromotetheirapplication.Thisresearchemploysanewphylogeneticmethod,i.e.,revelationandcomparisonofgenomestructure,tocategorizerhizobia.Phylogenyisthestudyoftheevolutionaryrelationshipsamongorgan-isms[1].Currentlyphylogeneticrelationshipsamongrhizobiaaremostlyinferredfromcomparisons… 相似文献