全文获取类型
收费全文 | 530篇 |
免费 | 45篇 |
国内免费 | 87篇 |
出版年
2024年 | 3篇 |
2023年 | 8篇 |
2022年 | 10篇 |
2021年 | 22篇 |
2020年 | 16篇 |
2019年 | 18篇 |
2018年 | 7篇 |
2017年 | 13篇 |
2016年 | 11篇 |
2015年 | 10篇 |
2014年 | 20篇 |
2013年 | 25篇 |
2012年 | 17篇 |
2011年 | 31篇 |
2010年 | 15篇 |
2009年 | 19篇 |
2008年 | 27篇 |
2007年 | 23篇 |
2006年 | 33篇 |
2005年 | 30篇 |
2004年 | 20篇 |
2003年 | 23篇 |
2002年 | 14篇 |
2001年 | 22篇 |
2000年 | 19篇 |
1999年 | 22篇 |
1998年 | 20篇 |
1997年 | 18篇 |
1996年 | 14篇 |
1995年 | 31篇 |
1994年 | 14篇 |
1993年 | 8篇 |
1992年 | 17篇 |
1991年 | 5篇 |
1990年 | 8篇 |
1989年 | 14篇 |
1988年 | 7篇 |
1987年 | 10篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有662条查询结果,搜索用时 15 毫秒
1.
The results of a detailed analysis of 100 supernumerary limbs generated by 180° ipsilateral rotation (on the same limb stump) of regeneration blastemas is presented. The limbs were analyzed in terms of their position of origin, frequency, cartilage structure by Victoria blue staining, and muscle structure by serial sections. Single, double, or triple supernumeraries can be produced at no unique position of origin, although the posterodorsal quadrant was preferred. Four classes of supernumerary limbs were generated by such operations—normal; double dorsal or double ventral; part normal/part mirror imaged; part normal/part inverted in approximately equal frequencies. After amputation of these supernumeraries the same muscle patterns are faithfully regenerated. A hypothesis to explain the production of these abnormal limbs is proposed based on the observed phenomenon of fusion of supernumerary blastemata, but their regenerative behaviour presents problems for current models of pattern formation. Similar results have been obtained with developing limb buds and the relation between development and regeneration is discussed. 相似文献
2.
A. G. Manganaris F. H. Alston 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1987,74(1):154-161
Summary Four zones of enzymatic activity for glutamate oxaloacetate transaminase (GOT) were found in apple tissue. A dimeric gene, GOT-1, determining the fastest migrating zone, was identified. Six alleles were found, including a near null allelle which produced detectable heterodimeric bands but not homodimeric bands. A marked deficit or absence of certain geno-types in all backcrosses and in some crosses between unrelated varieties was attributed to the close linkage (r=0.02±0.005) of GOT-1 with the incompatibility S locus. GOT-1 was also closely linked with the isocitrate dehydrogenase locus IDH-1 (0.03±0.01). Proposed incompatibility genotypes for four cultivars, and the linked GOT-1 alleles are Cox: S
1
b/S
2
d, Idared: S
3
a/S
4
c, Fiesta: S
3
a/S
2
d and Kent: S
3
a/S
1
b.The results reported in this paper are part of a PhD Thesis by the first author 相似文献
3.
Silver ions inhibit the ethylene-stimulated production of ripening-related mRNAs in tomato 总被引:4,自引:1,他引:3
Abstract. Silver ions effectively inhibited both the initiation and the continuation of tomato ( Lyeopersicon esculentum Mill) ripening. Studies of protein synthesis in vivo showed that application of 2 mol m−3 silver thiosulphate to mature green fruit prevented the appearance of several novel proteins associated with ripening, including the softening enzyme polygalacturonase. However, total protein synthesis, as judged by the incorporation of [35 S] methionine into proteins, continued unabated after silver treatment. Ripening was also arrested when silver was supplied after ripening had begun. The accumulation of several ripening-related mRNAs, including that for polygalacturonase, was studied by translation in vitro and using cDNA clones as hybridization probes. Silver was shown to prevent the appearance of polygalaturonase mRNA when supplied to mature green fruit and to cause a rapid reduction in the concentration of mRNA for polygalacturonase and other ripening-related proteins when supplied after ripening had begun. It is proposed that silver exerts its effects due to interaction with the ethylene perception mechanism. The results suggest that perception of ethylene is vital not only for the initiation of ripening but also for the continued expression of genes required for ripening. 相似文献
4.
鹅掌楸种子和胚胎发育的研究 总被引:23,自引:0,他引:23
应用控制授粉、软 X-射线法、常规石蜡制片法和荧光检测等手段,研究了鹅掌楸(Lirio-dendron chinense(Hemsl.)Sarg.胚胎发育和控制授粉与结籽率的相关性。控制授粉后2小时花粉萌发,6小时萌发率最高,柱头可授期持续30小时左右。花粉管借助于柱头毛之间的分泌物进入柱头沟,经花柱沟、珠孔塞和珠心冠原进入胚囊,行珠孔受精。授粉后2周,胚乳为2至3细胞厚的狭组织;第6周,胚乳充满胚囊腔,珠心随之解体殆尽;第7到8周,球形胚、心形胚发生;第14到16周,子叶形成;第22周种子或熟,胚乳丰富。单株自然授粉结籽率不足1%。控制授粉后,单个聚合果的最高结籽率可达39%,9个聚合果的平均结籽率为17.7%。 相似文献
5.
D. M. O'Malley R. P. Guries E. V. Nordheim 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1986,72(4):530-535
Summary Estimates of recombination frequency among enzyme loci of pitch pine revealed two new linkages, Mdh3:Pgm2 (=0.01) and Pep1:Mdh4 (=0.38), and confirmed two previously established linkages. Tighter linkage (=0.30) was ruled out for nearly all gene pairs examined. In general, the Bayesian approach used in this study to test for linkage performed better than alternative methods.This work was supported by the School of Natural Resources, College of Agricultural and Life Sciences, University of Wisconsin, Madison, WI, and by McIntyre-Stennis, project no. 142-C385 相似文献
6.
M. Maden 《Developmental biology》1983,98(2):409-416
Previous experiments in which vitamin A has been administered to developing or regenerating limbs have shown that different limb axes are affected. In regenerating axolotl limbs, serial reduplications in the proximodistal axis are produced. In the developing chick limb bud, mirror-imaged reduplications in the anteroposterior axis are produced. Results reported here on Rana temporaria limb buds reveal that vitamin A causes both effects to occur. That is, limbs are both serially reduplicated in the proximodistal axis and mirror imaged in the anteroposterior axis. Time and concentration effects are explored and the significance of these results for our current understanding of axial organisation in limbs is discussed. 相似文献
7.
8.
羊草草地枯枝落叶中N,P,K变化动态 总被引:7,自引:2,他引:5
羊草草地枯枝落叶中N、P、K变化动态郭继勋,祝廷成(东北师范大学国家草地生态工程实验室,长春130024)DynamicsofN,PandKinlittersonAneurolopidiumchinensegrassland.¥GuoJixunand... 相似文献
9.
10.
本实验合并应用枸杞有效成份和大蒜有效成份,作用于U_14腹水型宫颈癌小鼠,腹腔注射第四天,发现一般状况改善,取腹水观察,癌细胞破损,DNA、RNA荧光染色强度减弱,有大量白细胞和巨噬细胞围绕;流式细胞分析G_1期细胞堆积,超微结构显示胞质中线粒体肿胀,嵴破坏甚至中空,粗面内质网扩大、脱颗粒,肯定了其作用的效果。此因枸杞有效成分活化巨噬细胞与肿瘤细胞紧密结合而起到溶瘤作用,与大蒜有效成分直接杀伤而作用维持短暂结合起来,可大大提高抗癌作用。 相似文献