全文获取类型
收费全文 | 36987篇 |
免费 | 16648篇 |
国内免费 | 26篇 |
出版年
2022年 | 171篇 |
2021年 | 550篇 |
2020年 | 2257篇 |
2019年 | 3792篇 |
2018年 | 3930篇 |
2017年 | 4172篇 |
2016年 | 4248篇 |
2015年 | 4341篇 |
2014年 | 3980篇 |
2013年 | 4565篇 |
2012年 | 2370篇 |
2011年 | 2040篇 |
2010年 | 3340篇 |
2009年 | 2056篇 |
2008年 | 1176篇 |
2007年 | 740篇 |
2006年 | 712篇 |
2005年 | 686篇 |
2004年 | 669篇 |
2003年 | 628篇 |
2002年 | 643篇 |
2001年 | 528篇 |
2000年 | 457篇 |
1999年 | 373篇 |
1998年 | 143篇 |
1997年 | 151篇 |
1996年 | 124篇 |
1995年 | 161篇 |
1994年 | 133篇 |
1993年 | 138篇 |
1992年 | 172篇 |
1991年 | 177篇 |
1990年 | 185篇 |
1989年 | 202篇 |
1988年 | 178篇 |
1987年 | 171篇 |
1986年 | 151篇 |
1985年 | 161篇 |
1984年 | 146篇 |
1983年 | 131篇 |
1982年 | 151篇 |
1981年 | 166篇 |
1980年 | 139篇 |
1979年 | 152篇 |
1978年 | 118篇 |
1977年 | 88篇 |
1975年 | 91篇 |
1974年 | 84篇 |
1973年 | 94篇 |
1972年 | 87篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
T. RIGOT M. VERCAUTEREN DRUBBEL J.‐C. DELÉCOLLE M. GILBERT 《Medical and veterinary entomology》2013,27(1):29-38
The spatial epidemiology of Bluetongue virus (BTV) at the landscape level relates to the fine‐scale distribution and dispersal capacities of its vectors, midges belonging to the genus Culicoides Latreille (Diptera: Ceratopogonidae). Although many previous researches have carried out Culicoides sampling on farms, little is known of the fine‐scale distribution of Culicoides in the landscape immediately surrounding farms. The aim of this study was to gain a better understanding of Culicoides populations at increasing distances from typical dairy farms in north‐west Europe, through the use of eight Onderstepoort‐type black‐light traps positioned along linear transects departing from farms, going through pastures and entering woodlands. A total of 16 902 Culicoides were collected in autumn 2008 and spring 2009. The majority were females, of which more than 97% were recognized as potential vectors. In pastures, we found decreasing numbers of female Culicoides as a function of the distance to the farm. This pattern was modelled by leptokurtic models, with parameters depending on season and species. By contrast, the low number of male Culicoides caught were homogeneously distributed along the transects. When transects entered woodlands, we found a higher abundance of Culicoides than expected considering the distance of the sampling sites to the farm, although this varied according to species. 相似文献
102.
103.
104.
105.
106.
107.
Distinct effects of climate warming on populations of silver fir (Abies alba) across Europe
下载免费PDF全文
![点击此处可从《Journal of Biogeography》网站下载免费的PDF全文](/ch/ext_images/free.gif)
108.
Lower Miocene siliciclastic sediments of the Vöckla Schichten and Atzbacher Sande, Austria, contain a shallow-water trace-fossil assemblage of the Cruziana ichnofacies includingSkolithos isp.,Planolites ? beverleyensis, Ophiomorpha annulata, O.nodosa, Rosselia socialis, Cylindrichnus concentricus, Scolicia isp., andBichordites monastiriensis. The ichnogenusRosselia and the ichnospeciesRosselia socialis are revised. Analysis ofScolicia isp. andB. monastiriensis provides new information about their morphology and ichnotaxonomy. 相似文献
109.
Carles Grau Romuald Ginhoux Alejandro Riera Thanh Lam Nguyen Hubert Chauvat Michel Berg Julià L. Amengual Alvaro Pascual-Leone Giulio Ruffini 《PloS one》2014,9(8)
Human sensory and motor systems provide the natural means for the exchange of information between individuals, and, hence, the basis for human civilization. The recent development of brain-computer interfaces (BCI) has provided an important element for the creation of brain-to-brain communication systems, and precise brain stimulation techniques are now available for the realization of non-invasive computer-brain interfaces (CBI). These technologies, BCI and CBI, can be combined to realize the vision of non-invasive, computer-mediated brain-to-brain (B2B) communication between subjects (hyperinteraction). Here we demonstrate the conscious transmission of information between human brains through the intact scalp and without intervention of motor or peripheral sensory systems. Pseudo-random binary streams encoding words were transmitted between the minds of emitter and receiver subjects separated by great distances, representing the realization of the first human brain-to-brain interface. In a series of experiments, we established internet-mediated B2B communication by combining a BCI based on voluntary motor imagery-controlled electroencephalographic (EEG) changes with a CBI inducing the conscious perception of phosphenes (light flashes) through neuronavigated, robotized transcranial magnetic stimulation (TMS), with special care taken to block sensory (tactile, visual or auditory) cues. Our results provide a critical proof-of-principle demonstration for the development of conscious B2B communication technologies. More fully developed, related implementations will open new research venues in cognitive, social and clinical neuroscience and the scientific study of consciousness. We envision that hyperinteraction technologies will eventually have a profound impact on the social structure of our civilization and raise important ethical issues. 相似文献
110.
Integrated species delimitation and conservation implications of an endangered weevil Pachyrhynchus sonani (Coleoptera: Curculionidae) in Green and Orchid Islands of Taiwan
下载免费PDF全文
![点击此处可从《Systematic Entomology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
YEN‐TING CHEN HUI‐YUN TSENG MING‐LUEN JENG YONG‐CHAO SU WEN‐SAN HUANG CHUNG‐PING LIN 《Systematic Entomology》2017,42(4):796-813
Oceanic islands are productive habitats for generating new species and high endemism, which is primarily due to their geographical isolation, smaller population sizes and local adaptation. However, the short divergence times and subtle morphological or ecological divergence of insular organisms may obscure species identity, so the cryptic endemism on islands may be underestimated. The endangered weevil Pachyrhynchus sonani Kôno (Coleoptera: Curculionidae: Entiminae: Pachyrhynchini) is endemic to Green Island and Orchid Island of the Taiwan‐Luzon Archipelago and displays widespread variation in coloration and host range, thus raising questions regarding its species boundaries and degree of cryptic diversity. We tested the species boundaries of P. sonani using an integrated approach that combined morphological (body size and shape, genital shape, coloration and cuticular scale), genetic (four genes and restriction site‐associated DNA sequencing, RAD‐seq) and ecological (host range and distribution) diversity. The results indicated that all the morphological datasets for male P. sonani, except for the colour spectrum, reveal overlapping but statistically significant differences between islands. In contrast, the morphology of the female P. sonani showed minimum divergence between island populations. The populations of P. sonani on the two islands were significantly different in their host ranges, and the genetic clustering and phylogenies of P. sonani established two valid evolutionary species. Integrated species delimitation combining morphological, molecular and ecological characters supported two distinct species of P. sonani from Green Island and Orchid Island. The Green Island population was described as P. jitanasaius sp.n. Chen & Lin, and it is recommended that its threatened conservation status be recognized. Our findings suggest that the inter‐island speciation of endemic organisms inhabiting both islands may be more common than previously thought, and they highlight the possibility that the cryptic diversity of small oceanic islands may still be largely underestimated. 相似文献