全文获取类型
收费全文 | 107篇 |
免费 | 24篇 |
国内免费 | 113篇 |
专业分类
244篇 |
出版年
2023年 | 2篇 |
2022年 | 2篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 3篇 |
2018年 | 4篇 |
2017年 | 3篇 |
2016年 | 1篇 |
2015年 | 6篇 |
2014年 | 21篇 |
2013年 | 14篇 |
2012年 | 4篇 |
2011年 | 2篇 |
2010年 | 4篇 |
2009年 | 6篇 |
2008年 | 17篇 |
2007年 | 10篇 |
2006年 | 5篇 |
2005年 | 27篇 |
2004年 | 11篇 |
2003年 | 1篇 |
2002年 | 4篇 |
2001年 | 13篇 |
2000年 | 1篇 |
1999年 | 18篇 |
1998年 | 8篇 |
1997年 | 7篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 3篇 |
1993年 | 11篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1959年 | 1篇 |
1958年 | 4篇 |
1957年 | 1篇 |
1956年 | 2篇 |
1955年 | 1篇 |
1954年 | 2篇 |
1953年 | 1篇 |
1952年 | 2篇 |
排序方式: 共有244条查询结果,搜索用时 15 毫秒
21.
INTRODUCTIONThe material dealt with in this paper came from the upper part of the Wu-tsun shale near Liuchingyu.The village is located on the right bank of Yukiang,about 12 km.to the north of Yungchun city.The Wutsun shale consists mainlyof shales and sandstones with a bed of argillaceous limestone in the upper partvarying from a few to 15 meters thick.The bryozoans occur in the uppermostpart of the formation,where the rock contains high iron contents.They are 相似文献
22.
YANG TSUN-YI 《古生物学报》1959,(6):492-498
INTRODUCTIONThis paper deals with all the fossil molluscs collected respectively by Dr.P.Li's party in1956 and Dr.T.H.Yin's party in 1957 of the Institute of Geology,Academia Sinica.Pre-liminary reports regarding the discovery of the Ordovician in the Paiyangho region has been madeby Li,and Yang(1957),and Li,Hsieh and Ho(1958),while the writer had twice reported 相似文献
23.
四部体小麦“简阳矮兰麦”与黑麦可杂交性及其在六倍体水平上的遗传特性 总被引:3,自引:2,他引:3
刘登才 彭正松 颜济 杨俊良 郑有良LIU Deng-cai PENG Zheng-song YAN Ji YANG Jun-Liang ZHENG You-liang 《遗传》1998,20(6):26-29
中国六倍体普通小麦地方品种有一个比较独特的特征-存在丰富的高亲和性材料。因此,研究中国四倍体小麦的亲和性问题具有特殊的意义。“简阳矮兰麦”是来源于四川省的一个四倍体小麦地方品种,它与黑麦有高的可杂交性,其杂交结实率达60%。遗传分析表明,“简阳矮兰麦”与黑麦的高可杂交性是受2-3对隐性基因所控制,但3对基因的可能性更大。而且,这些隐性基因的作用在合成六倍体小麦后仍能比较完全的表达。通过与六倍体普通小麦相比较,结果表明四倍体小麦的可杂交性系统与六倍体小麦的可杂交性系统的作用方式是类似的。Abstract:It is a special characteristic that many Chinese common wheat landraces showed a high crossability with rye.Thus,it is important that elucidate the genetic control of the crossability of Chinese tetraploid wheat with rye.Triticum turgidum cv.Jianyangailanmai native to Sichuan,China has high crossability with rye,up to 60%.In this study,it is indicated that the crossability of Jianyangailanmai with rve is controlled by two or more probably three recessive genes,which was almost totally expressed in the hexaploid wheat level.The operation of these recessive genes influencing crossability with rye was similar to that of hexaploid common wheat. 相似文献
24.
DENG XIANG YANG ZHI MING WEI HAI LONG AN Institute of Plant Physiology Ecology Shanghai Institutes for Biological Sciences Chinese Academy Sciences Shanghai China 《Cell research》2001,(2)
INTRODUCTIONArachiS hypogaea L., Peanut or groundnut, isan importal commercial crop worldwide. It provides an excellellt source of protein and other nutrients. Its production and quality can be severelyimpacted under stressful growing conditions such ascdriate factors, pests and diseajses. Genetic engineering provides a prospective way to reduce certainproblems by transferring individual genes for pestresistance or other traits into elite germplasm of acultiVated species. Thansgenic pea… 相似文献
25.
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
26.
Vigilance behavior is considered as an effective strategy for prey species to detect predators.An individual benefits from living in a group by reducing the time spent being vigilant without affecting the probability of detecting a predator.However,the mechanism producing a decrease in vigilance with increasing group size is unclear.Many models of vigilance assume that group members scan independently of one another.Yet in recent studies,the other 2 patterns of vigilance,coordination and synchronization,were reported in some species.In 2 summers(2018 and 2019),we studied the group-size effect on vigilance and foraging of Tibetan wild ass in Chang Tang Nature Reserve of Tibet.We also tested whether individuals scan the environment independently,tend to coordinate their scans,or tend to synchronize their vigilance.The results showed that individuals decreased the time spent on vigilance with increasing group size,while increased the time spent foraging.Group members scanned the environment at the same time more frequently and there was a positive correlation between group members'behaviors,indicating that Tibetan wild asses tend to synchronize their vigilance. 相似文献
27.
DUAN AiPing NING LiMin LI Chao HOU YaFei YANG NaNa SUN LiZhou LI GenXi 《中国科学:生命科学英文版》2013,56(4):293-297
Hepatitis C virus (HCV), a positive single-stranded RNA virus, is a major cause of liver disease in humans. Herein we report a novel strategy to inhibit the reproduction and translation of HCV using a short RNA, named an Additional RNA, to activate the endonuclease activity of Argonaute 2 (Ago2). In the presence of the Additional RNA, the HCV genome RNA has the requisite 12 nucleotides of base-pairing with microRNA-122. This activates the endonuclease activity of Ago2, resulting in cleavage and release of the HCV genome RNA from Ago2 and microRNA-122. The free HCV genome RNA would be susceptible to intracellular degradation, effectively inhibiting its reproduction and translation. This study presents a new method to inhibit HCV that may hold great potential for HCV treatment in the future. 相似文献
28.
Individual’s phenotypic traits are the results of adaptation to ecological conditions.Therefore,different selection pressures caused by heterogeneous environments may result in phenotypic difference,especially for individuals in different geographical populations.Here,we illustrated for the first time to use social network analysis(SNA)for examining whether geographical proximity predicts the similarity patterns in call characteristics among populations of an anuran species.We recorded calls from 150 male dorsal-striped opposite-fingered treefrogs(Chiromantis doriae)at 11 populations in Hainan Province and one population in Guangdong Province in China's Mainland,and we measured eight acoustic variables for each male.Mantel test didn’t show a correlation between geographical proximity and the similarity in call characteristics among populations.In addition,we failed to find correlations between a population’s eigenvector centrality and the distance to its nearest neighbor,nor between the coefficient of variation of similarity in call characteristics of a population and the average distance to all other populations.Nevertheless,three acoustic clusters were identified by the Girvan-Newman algorithm,and clustering was partially associated with geography.Furthermore,the most central populations were included in the same cluster,but the top betweenness populations were located within different clusters,suggesting that centrality populations are not necessary bridging between clusters.These results demonstrate the potential usefulness of the SNA toolbox and indicate that SNA helps to uncover the patterns that often overlooked in other analytical methods.By using SNA in frog’s call studies,researchers could further uncover the potential relationship in call characteristics between geographical populations,further reveal the effects of ecological factors on call characteristics,and probably enhance our understanding of the adaptive evolution of acoustic signals. 相似文献
29.
30.
ZHANG Dian YUAN Bingxiang DENG Xiuling YANG Guangde HE Langchong ZHANG Youyi & HAN Qide . School of Medicine Xi''''an Jiaotong University Xi''''an China . College of pharmacy Xi''''an Jiaotong University Xi''''an China . Third Hospital Beijing University Beijing China 《中国科学:生命科学英文版》2004,(4)
Copyright by Science in China Press 2004 The a1-AR is present in many tissues including heart, blood vessels, liver, brain, kidney, prostate and spleen. In these tissues, the a1-AR mediates a variety of physiological effects such as neurotransmission, vasoconstriction, cardiacinotropy, chronotropy and glycogenolysis[1]. In 1986, Morrow and Greese pro-posed that a1-AR should be subclassified into two subtypes. Later this hypothesis was proved by Q.D Han in 1987. He not only verified a1-A… 相似文献