全文获取类型
收费全文 | 649篇 |
免费 | 52篇 |
出版年
2022年 | 5篇 |
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 10篇 |
2017年 | 7篇 |
2016年 | 6篇 |
2015年 | 14篇 |
2014年 | 16篇 |
2013年 | 37篇 |
2012年 | 29篇 |
2011年 | 25篇 |
2010年 | 26篇 |
2009年 | 26篇 |
2008年 | 25篇 |
2007年 | 26篇 |
2006年 | 30篇 |
2005年 | 25篇 |
2004年 | 37篇 |
2003年 | 20篇 |
2002年 | 35篇 |
2001年 | 25篇 |
2000年 | 25篇 |
1999年 | 19篇 |
1998年 | 13篇 |
1997年 | 12篇 |
1996年 | 4篇 |
1995年 | 11篇 |
1994年 | 7篇 |
1993年 | 9篇 |
1992年 | 11篇 |
1991年 | 11篇 |
1990年 | 22篇 |
1989年 | 10篇 |
1988年 | 13篇 |
1987年 | 5篇 |
1986年 | 10篇 |
1985年 | 7篇 |
1984年 | 8篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 8篇 |
1979年 | 5篇 |
1976年 | 3篇 |
1974年 | 5篇 |
1972年 | 5篇 |
1970年 | 4篇 |
1967年 | 2篇 |
1966年 | 7篇 |
1922年 | 2篇 |
排序方式: 共有701条查询结果,搜索用时 109 毫秒
661.
Transforming growth factor-alpha (TGFA) has been proposed as a candidate gene in the etiology of nonsyndromic cleft lip with or without cleft palate (NS-CL/P) and of nonsyndromic cleft palate only (NS-CPO). Biologic support for a role of TGFA arises from its presence at high levels in the epithelial tissue of the medial edge of the palatal shelves at the time of shelf fusion in mice. Genetic support for the role of TGFA in clefting comes from the reported association of TGFA alleles with human NS-CPO and NS-CL/P. In this study we report the sequence and structure of human genomic TGFA and the search for causal TGFA mutations in 250 individuals with NS-CL/P or NS-CPO by conformational analysis of the coding sequence, splice junctions, and a portion of the 3' untranslated region strongly homologous between human and mouse. We confirm that human TGFA is composed of six exons and here report several new sequence substitutions and their frequencies. Five variants in conserved segments may represent rare causes for clefting in humans and provide support for the role of TGFA in facial morphogenesis. 相似文献
662.
A marking-and-recapture study of a population of overwintered adults of Epilachna sparsa orientalis was carried out in a small farm containing potatoes and egg-plants. The experiment involved a single release and five recapture samplings during May–June. The data were analysed byLeslie's re-recapture method. Assumption of randomness of sampling proved to be well satisfied. Survival rate of the overwintered adult population was maintained as high as 90 per cent per week or more until early June, and then it declined rapidly towards the end of June. Initially overwintered adults exclusively lived on potato plants, but half of the population alive in mid June migrated to nearby egg-plants. Emigration out of the experimental field, however, seemed not to be occurring. Recapture data of marked individuals in the potato field indicate that majority of the individuals stayed within a radius of 3 m, at least for 2 weeks. Similar data taken from another field also suggest that their mobility was far restricted as compared with random movement within the field. Some comparisons were made between the population behaviours of overwintered adults of E. sparsa orientalis and E. vigintioctomaculata. 相似文献
663.
664.
Chiyoko Tokunaga 《Genetics》1970,66(4):653-661
665.
666.
Reaction of DL-1,3-dimethylthymine epoxide (1) with aniline gave (2A) and (3A). Isomerization of (2A) provided (3A), (4) and (5). Reaction of (1) with L-amino acid ethyl ester afforded four optically active diastereomers. 相似文献
667.
Effect of nucleosides both on induction of antiviral state in chick embryo cells (CEC) or rabbit kidney cells (RK13) and on interferon production in RK13 or mouse fibroblast cells (L cells) by polyriboinosinic-polyribocytidylic acid (poly I.poly C) was studied. Addition of inosine or a fifty-fifty mixture of inosine and uridine at a final concentration of 0.1 mM to 10 mM to a growth medium enhanced development of antiviral state in CEC. The nucleoside effect was also observed in RK13 at 0.1 mM but not at a concentration higher than 1 mM. Interferon production in RK13 by superinduction (sequential treatment with metabolic inhibitors after exposure to poly I.poly C) was enhanced 1.5- to 4.0-fold by addition of the nucleoside mixture to the growth medium. When RK13 was pretreated with 10 units per ml of interferon and then superinduced by inhibitors, the enhancing effect of nucleosides on interferon production was not observed. Interferon production in L cells was potentiated a little by addition of 1 mM of the nucleoside mixture to the growth medium. The effect of nucleoside was not observed when the nucleosides were added after exposure to poly I.poly C. The nucleoside effect may be applicable for production of high titered interferon. 相似文献
668.
Embryonic development of Zoraptera with special reference to external morphology,and its phylogenetic implications (Insecta)
下载免费PDF全文
![点击此处可从《Journal of morphology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yuta Mashimo Rolf G. Beutel Romano Dallai Chow‐Yang Lee Ryuichiro Machida 《Journal of morphology》2014,275(3):295-312
The embryonic development of Zorotypus caudelli Karny (Zoraptera) is described with the main focus on its external features. A small heart‐shaped embryo is formed on the dorsal side of the egg by the fusion of paired blastoderm regions with higher cellular density. The orientation of its anteroposterior axis is opposed to that of the egg. This unusual condition shows the potential autapomorphy of Zoraptera. The embryo extends along the egg surface and after reaching its full length, it migrates into the yolk. After developing there for a period of time, it reappears on the surface, accompanied by a reversion of its anteroposterior axis, finally taking its position on the ventral side of the egg. The definitive dorsal closure completes, and the prelarva hatches after perforating the chorion with very long egg tooth formed on the embryonic cuticle. Embryological data suggest the placement of Zoraptera among the “lower neopteran” or polyneopteran lineage: features supporting this are embryo formation by the fusion of paired regions with higher cellular density and blastokinesis accompanied by full elongation of the embryo on the egg surface. The extraordinarily long egg tooth has potential synapomorphy with Embioptera or Eukinolabia (= Embioptera + Phasmatodea). Together with the results from our previous studies on the egg structure, male reproductive system and spermatozoa, the close affinity of Zoraptera with Eukinolabia appears likely, that is, a clade Zoraptera + (Embioptera + Phasmatodea). J. Morphol. 275:295–312, 2014. © 2013 Wiley Periodicals, Inc. 相似文献
669.
670.