全文获取类型
收费全文 | 13201篇 |
免费 | 769篇 |
国内免费 | 2107篇 |
出版年
2024年 | 58篇 |
2023年 | 205篇 |
2022年 | 262篇 |
2021年 | 305篇 |
2020年 | 356篇 |
2019年 | 440篇 |
2018年 | 428篇 |
2017年 | 350篇 |
2016年 | 470篇 |
2015年 | 499篇 |
2014年 | 639篇 |
2013年 | 1011篇 |
2012年 | 747篇 |
2011年 | 745篇 |
2010年 | 504篇 |
2009年 | 657篇 |
2008年 | 714篇 |
2007年 | 722篇 |
2006年 | 654篇 |
2005年 | 574篇 |
2004年 | 543篇 |
2003年 | 534篇 |
2002年 | 524篇 |
2001年 | 387篇 |
2000年 | 364篇 |
1999年 | 333篇 |
1998年 | 303篇 |
1997年 | 269篇 |
1996年 | 297篇 |
1995年 | 311篇 |
1994年 | 225篇 |
1993年 | 177篇 |
1992年 | 177篇 |
1991年 | 165篇 |
1990年 | 180篇 |
1989年 | 136篇 |
1988年 | 54篇 |
1987年 | 40篇 |
1986年 | 42篇 |
1985年 | 53篇 |
1984年 | 54篇 |
1983年 | 39篇 |
1982年 | 64篇 |
1981年 | 61篇 |
1980年 | 106篇 |
1979年 | 119篇 |
1978年 | 65篇 |
1977年 | 43篇 |
1976年 | 19篇 |
1974年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
24.
Distinct effects of climate warming on populations of silver fir (Abies alba) across Europe 下载免费PDF全文
25.
Rolf Anker Ims 《Evolutionary ecology》1990,4(1):57-61
Summary Mate detection success of male grey-sided voles,Clethrionomys rufocanus, in relation to the spatial distribution of sexually receptive females was studied in an experimental island population. The spatiotemporal distribution of receptive females was controlled by containing females in small, mobile wire-mesh cages, whereas the response by free-ranging males was monitored by means of radiotelemetry. Males were on average more successful in finding oestrous females when females were spatially clumped than when females were spatially overdispersed. In addition, the variance (CV) in male mate detecting success was highest when females had an overdispersed spatial distribution. These results are consistent with predictions from a theoretical model (Ims, 1988b) analysing the effect of mate distribution on male mating success, and with empirical results on prey detection success of predators searching for prey. 相似文献
26.
27.
本文描述了发现于福建的冬青科冬青属2新种——泰宁冬青Ilex tainingensis G. S. He和南平冬青I. nanpingensis G. S. He,并分别说明两者与其他近缘种的区别要点。泰宁冬青与太平山冬青I. sugerokii Maxim.的区别在于前种小枝被毛,无棱槽,叶片宽卵圆形,花淡紫色,分核表面具细条纹,背后中部有一凹槽。南平冬青与拟榕叶冬青I. subficoidea S. Y. Hu区别在于前种果为椭圆形,较大,表面光滑无腺点,果梗长于1 cm,每分核上端有2尖角,均可以区别。 相似文献
28.
山西省异爪蝗属二新种(直翅目:网翅蝗科) 总被引:4,自引:0,他引:4
本文记述在晋南地区采到的异爪蝗属二新种,黑条异爪蝗Euchorthippus nigiliineatus sp.nov.及曲线异爪蝗Eochorthippus sinucarinatus sp.nov. 相似文献
29.
Loïc Pellissier Charlotte Ndiribe Anne Dubuis Jean‐Nicolas Pradervand Nicolas Salamin Antoine Guisan Sergio Rasmann 《Ecology letters》2013,16(5):600-608
Understanding drivers of biodiversity patterns is of prime importance in this era of severe environmental crisis. More diverse plant communities have been postulated to represent a larger functional trait‐space, more likely to sustain a diverse assembly of herbivore species. Here, we expand this hypothesis to integrate environmental, functional and phylogenetic variation of plant communities as factors explaining the diversity of lepidopteran assemblages along elevation gradients in the Swiss Western Alps. According to expectations, we found that the association between butterflies and their host plants is highly phylogenetically structured. Multiple regression analyses showed the combined effect of climate, functional traits and phylogenetic diversity in structuring butterfly communities. Furthermore, we provide the first evidence that plant phylogenetic beta diversity is the major driver explaining butterfly phylogenetic beta diversity. Along ecological gradients, the bottom up control of herbivore diversity is thus driven by phylogenetically structured turnover of plant traits as well as environmental variables. 相似文献
30.
Cynthia Nafula Wakhungu Isaiah Masinde Tabu O. Daniel Otaye Wafula Victor Wasike 《Archives Of Phytopathology And Plant Protection》2017,50(7-8):398-414
A study was carried out to determine Fusarium wilt distribution in Bambara nut farmers’ fields and its management using farm yard manure (FYM). Four villages in Busia County were purposively sampled for the study. The data generated were subjected to analysis of variance and treatment means separated by least significant difference test. Fusarium wilt incidence in the fields ranged from 14.63 to 43.56%. In the greenhouse, FYM reduced the disease incidence by 10.2% and severity by 9.5% on the black landrace and 1.9 and 12.8%, respectively, on the red landrace. In the field, FYM reduced disease incidence by 9.1% and severity by 6.9% on the black landrace and 10.4 and 10.4%, respectively, on the red landrace. Farm yard manure had the lowest area under disease progress curve irrespective of the landrace. The study confirmed the presence of the pathogen in the fields and the ability to manage the disease using FYM. 相似文献