全文获取类型
收费全文 | 958篇 |
免费 | 87篇 |
国内免费 | 9篇 |
专业分类
1054篇 |
出版年
2015年 | 19篇 |
2014年 | 16篇 |
2013年 | 27篇 |
2012年 | 23篇 |
2011年 | 27篇 |
2010年 | 24篇 |
2009年 | 27篇 |
2008年 | 29篇 |
2007年 | 26篇 |
2006年 | 25篇 |
2005年 | 13篇 |
2004年 | 19篇 |
2003年 | 15篇 |
2002年 | 13篇 |
2001年 | 21篇 |
2000年 | 13篇 |
1999年 | 22篇 |
1998年 | 12篇 |
1997年 | 12篇 |
1996年 | 16篇 |
1992年 | 20篇 |
1991年 | 18篇 |
1990年 | 10篇 |
1989年 | 16篇 |
1988年 | 15篇 |
1987年 | 18篇 |
1986年 | 10篇 |
1984年 | 9篇 |
1983年 | 14篇 |
1981年 | 12篇 |
1980年 | 9篇 |
1979年 | 17篇 |
1978年 | 12篇 |
1976年 | 11篇 |
1974年 | 14篇 |
1973年 | 14篇 |
1971年 | 10篇 |
1958年 | 23篇 |
1957年 | 27篇 |
1956年 | 27篇 |
1955年 | 22篇 |
1954年 | 22篇 |
1953年 | 13篇 |
1952年 | 13篇 |
1951年 | 10篇 |
1950年 | 9篇 |
1923年 | 11篇 |
1922年 | 14篇 |
1921年 | 12篇 |
1920年 | 14篇 |
排序方式: 共有1054条查询结果,搜索用时 15 毫秒
991.
992.
993.
Long‐proboscid brachyceran flies in Cretaceous amber (Diptera: Stratiomyomorpha: Zhangsolvidae) 下载免费PDF全文
ANTONIO ARILLO ENRIQUE PEÑALVER RICARDO PÉREZ‐DE LA FUENTE XAVIER DELCLÒS JULIA CRISCIONE PHILLIP M. BARDEN MARK L. RICCIO DAVID A. GRIMALDI 《Systematic Entomology》2015,40(1):242-267
The monophyletic family Zhangsolvidae comprises stout‐bodied brachyceran flies with a long proboscis and occurring only in the Cretaceous, originally known in shale from the Early Cretaceous Laiyang Formation (Fm.) in China (Zhangsolva Nagatomi & Yang), subsequently from limestones of the Early Cretaceous Crato Fm. of Brazil. Cratomyoides Wilkommen is synonymized with Cratomyia Mazzarolo & Amorim, both from the Crato Fm.; Cratomyiidae is synonymized with Zhangsolvidae. Two genera and three species of Zhangsolvidae are described: Buccinatormyia magnifica Arillo, Peñalver & Pérez‐de la Fuente, gen. et sp.n. and B. soplaensis Arillo, Peñalver & Pérez‐de la Fuente, sp.n. , in Albian amber from Las Peñosas Fm. in Spain; and Linguatormyia teletacta Grimaldi, gen. et sp.n. , in Upper Albian–Lower Cenomanian amber from Hukawng Valley in Myanmar. Buccinatormyia soplaensis and Linguatormyia teletacta are unique among all Brachycera, extant or extinct, by their remarkably long, flagellate antennae, about 1.6× the body length in the latter species. A phylogenetic analysis of 52 morphological characters for 35 taxa is presented, 11 taxa being Cretaceous species, which supports placement of the family within Stratiomyomorpha, although not to any particular family within the infraorder. This published work has been registered in Zoobank, http://zoobank.org/urn:lsid:zoobank.org:pub:F32CF887‐7C37‐45D5‐BD6B‐135FE9B729A7 . 相似文献
994.
J. M. Giebultowicz M. J. Loeb A. B. Borkovec 《Invertebrate reproduction & development.》2013,57(2):211-224
Summary Premeiotic spermatocysts from testes of Heliothis virescens larvae were cultured in vitro. These eupyrene cysts progressed through meiosis and elongation in a medium containing calf serum in the absence of ecdysteroids. However, they also required the presence of the testis sheaths. The spermatogenesis-promoting effect of testis sheaths was dose dependent and varied with the donor's age. The active material was extractable from the tissue and was heat stable. 相似文献
995.
996.
997.
998.
999.
G E Loeb 《Canadian journal of physiology and pharmacology》1981,59(7):627-635
Chronic recording techniques in freely walking cats have been used to sample unitary activity from most large myelinated afferent classes. Cutaneous mechanoreceptors are highly sensitive and generate regular activity patterns predictable from their modalities. Knee joint afferents can fire briskly midrange locomotory movements but appear to be influenced by factors other than joint angle. Golgi tendon organs generate activity consistent with sensitivity to active muscle tension. Muscle spindle afferents do not appear to conform to any single functional pattern for all muscles. It is suggested that degree and rate of stretch are sensed by spindles (possibly under dynamic fusimotor bias) in extensor muscles which normally undergo isometric or lengthening contractions whereas rapidly modulated static fusimotor activity is employed to preserve spindle activity during the rapidly shortening contractions of flexor muscles. Both patterns may be represented in different spindles of bifunctional, biarticular muscles such as rectus femoris and sartorius. 相似文献
1000.