全文获取类型
收费全文 | 255篇 |
免费 | 21篇 |
国内免费 | 14篇 |
专业分类
290篇 |
出版年
2023年 | 3篇 |
2022年 | 6篇 |
2021年 | 10篇 |
2020年 | 9篇 |
2019年 | 17篇 |
2018年 | 16篇 |
2017年 | 15篇 |
2016年 | 11篇 |
2015年 | 15篇 |
2014年 | 14篇 |
2013年 | 43篇 |
2012年 | 18篇 |
2011年 | 13篇 |
2010年 | 14篇 |
2009年 | 9篇 |
2008年 | 13篇 |
2007年 | 11篇 |
2006年 | 5篇 |
2005年 | 4篇 |
2004年 | 3篇 |
2003年 | 6篇 |
2002年 | 1篇 |
2001年 | 2篇 |
2000年 | 4篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1987年 | 1篇 |
1985年 | 3篇 |
1984年 | 3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 |
排序方式: 共有290条查询结果,搜索用时 0 毫秒
51.
M. B. V. Bell A. N. Radford R. A. Smith A. M. Thompson A. R. Ridley 《Proceedings. Biological sciences / The Royal Society》2010,277(1698):3223-3228
Wherever individuals perform cooperative behaviours, each should be selected to adjust their own current contributions in relation to the likely future contributions of their collaborators. Here, we use the sentinel system of pied babblers (Turdoides bicolor) to show that individuals anticipate contributions by group mates, adjusting their own contribution in response to information about internal state broadcast by others. Specifically, we show that (i) short-term changes in state influence contributions to a cooperative behaviour, (ii) individuals communicate short-term changes in state, and (iii) individuals use information about the state of group mates to adjust their own investment in sentinel behaviour. Our results demonstrate that individual decisions about contributions to a cooperative effort can be influenced by information about the likely future contribution of others. We suggest that similar pre-emptive adjustments based on information obtained from collaborators will be a common feature of cooperative behaviour, and may play an important role in the development of complex communication in social species. 相似文献
52.
53.
54.
55.
Rune Blomhoff Per Helgerud Svein Dueland Trond Berg Jan I. Pedersen Kaare R. Norum Christian A. Drevon 《生物化学与生物物理学报:生物膜》1984,772(2):109-116
The lymphatic absorption and transport of retinol and vitamin D-3 from rat intestine has been studied. When rats were cannulated in the intestinal lymph duct and given an intraduodenal bolus of [3H]retinol and 14C-labelled vitamin D-3, 14C-labeled vitamin D-3 appeared later in the intestinal lymph than [3H]retinol and the rate of absorption of vitamin D-3 was still maximal at a time when that of retinol had declined. Both vitamins were absorbed via the lymphatic route in association with chylomicrons. Almost all the retinol was esterified, while vitamin D-3 appeared in the chylomicrons as free vitamin D-3. In vitro incubations and in vivo studies using hepatectomized and normal rats showed that the retinyl ester was a relatively nonexchangeable component of the chylomicrons and their remnants. Hence, all the vitamin A followed the remnants in their clearance from plasma. In contrast, significant amounts of vitamin D-3 were transferred from the chylomicrons to other plasma fractions. Therefore, only a fraction of this vitamin may be removed in association with the chylomicron remnants. 相似文献
56.
57.
40年前于1979年,在苏州召开的中国古生物学会第三届全国会员代表大会暨第12次学术年会盛况空前,在中国古生物学发展史上具有非常重要的意义。它标志着中国古生物学研究步入发展的新阶段,优秀成果大量涌现、学术交流频繁;此后的数年里学会活动空前活跃、会员人数大幅增加,从此学会活动正规化;中国古生物学界重新回到国际大家庭,对外交流频繁。 相似文献
58.
稻飞虱:国际视野下的中国问题 总被引:1,自引:0,他引:1
稻飞虱对日本水稻的危害已有数百年历史,日本人对稻飞虱的研究也超过了一个世纪,而国际水稻研究所(IRRI)在热带稻区为治理稻飞虱也已努力了近40年。本文综述了日本、国际水稻研究所(IRRI)对稻飞虱的研究与治理,提出了我国稻飞虱研究的发展方向。作者认为,稻飞虱的问题首先是个国际问题,我们的虫源在境外,因此必须走出国门掌握一手虫情;同时需要逐步扩大国际合作,尽早转变思路,以国际眼光研究和解决中国的飞虱问题。 相似文献
59.
Plant cell wall is the most abundant substrate for bioethanol production, and plants also represent a key resource for glycoside hydrolase (GH). To exploit efficient way for bioethanol production with lower cellulase loading, the potential of plant GH for lignocellulose bioconversion was evaluated. The GH activity for cell wall proteins (CWPs) was detected from fresh corn stover (FCS), and the synergism of which with Trichoderma reesei cellulase was also observed. The properties for the GH of FCS make it a promising enzyme additive for lignocellulose biodegradation. To make use of the plant GH, novel technology for hydrolysis and ethanol fermentation was developed with corn stover as substrate. Taking steam-exploded corn stover as substrate for hydrolysis and ethanol fermentation, compared with T. reesei cellulase loaded alone, the final glucose and ethanol accumulation increased by 60% and 63% respectively with GH of FCS as an addition. 相似文献
60.
迄今科学界尚无形成系统的国际科学合作理论,也鲜有就环境科学国际合作进行理论研究。首次从全球资源配置的角度来看待环境科学国际合作。通过国际合作,环境科学在内在科学动力和外在社会动力的驱动下,促使全球科学资源和社会资源向有利于环境学科自身发展的方向流动和积聚。其中,配置科学资源遵循"最优要素选择原则",配置社会资源遵循"最小省力原则",两种内在动力和两个调节手段共同构成了环境科学国际合作的理论机制。 相似文献