全文获取类型
收费全文 | 5827篇 |
免费 | 489篇 |
出版年
2023年 | 18篇 |
2022年 | 27篇 |
2021年 | 102篇 |
2020年 | 59篇 |
2019年 | 84篇 |
2018年 | 93篇 |
2017年 | 105篇 |
2016年 | 126篇 |
2015年 | 245篇 |
2014年 | 273篇 |
2013年 | 401篇 |
2012年 | 466篇 |
2011年 | 457篇 |
2010年 | 326篇 |
2009年 | 274篇 |
2008年 | 393篇 |
2007年 | 398篇 |
2006年 | 375篇 |
2005年 | 331篇 |
2004年 | 322篇 |
2003年 | 280篇 |
2002年 | 296篇 |
2001年 | 75篇 |
2000年 | 72篇 |
1999年 | 64篇 |
1998年 | 68篇 |
1997年 | 48篇 |
1996年 | 37篇 |
1995年 | 35篇 |
1994年 | 26篇 |
1993年 | 22篇 |
1992年 | 37篇 |
1991年 | 25篇 |
1990年 | 30篇 |
1989年 | 23篇 |
1988年 | 35篇 |
1987年 | 22篇 |
1986年 | 16篇 |
1985年 | 18篇 |
1984年 | 17篇 |
1983年 | 15篇 |
1982年 | 15篇 |
1981年 | 11篇 |
1979年 | 11篇 |
1978年 | 13篇 |
1977年 | 12篇 |
1975年 | 10篇 |
1974年 | 10篇 |
1973年 | 12篇 |
1966年 | 8篇 |
排序方式: 共有6316条查询结果,搜索用时 93 毫秒
991.
992.
993.
Revision of Corallinaceae (Corallinales,Rhodophyta): recognizing Dawsoniolithon gen. nov., Parvicellularium gen. nov. and Chamberlainoideae subfam. nov. containing Chamberlainium gen. nov. and Pneophyllum 下载免费PDF全文
Annalisa Caragnano Alexandra Foetisch Gavin W. Maneveldt Laurent Millet Li‐Chia Liu Showe‐Mei Lin Graziella Rodondi Claude E. Payri 《Journal of phycology》2018,54(3):391-409
A multi‐gene (SSU, LSU, psbA, and COI) molecular phylogeny of the family Corallinaceae (excluding the subfamilies Lithophylloideae and Corallinoideae) showed a paraphyletic grouping of six monophyletic clades. Pneophyllum and Spongites were reassessed and recircumscribed using DNA sequence data integrated with morpho‐anatomical comparisons of type material and recently collected specimens. We propose Chamberlainoideae subfam. nov., including the type genus Chamberlainium gen. nov., with C. tumidum comb. nov. as the generitype, and Pneophyllum. Chamberlainium is established to include several taxa previously ascribed to Spongites, the generitype of which currently resides in Neogoniolithoideae. Additionally we propose two new genera, Dawsoniolithon gen. nov. (Metagoniolithoideae), with D. conicum comb. nov. as the generitype and Parvicellularium gen. nov. (subfamily incertae sedis), with P. leonardi sp. nov. as the generitype. Chamberlainoideae has no diagnostic morpho‐anatomical features that enable one to assign specimens to it without DNA sequence data, and it is the first subfamily to possess both Type 1 (Chamberlainium) and Type 2 (Pneophyllum) tetra/bisporangial conceptacle roof development. Two characters distinguish Chamberlainium from Spongites: tetra/biasporangial conceptacle chamber diameter (<300 μm in Chamberlainium vs. >300 μm in Spongites) and tetra/bisporangial conceptacle roof thickness (<8 cells in Chamberlainium vs. >8 cells in Spongites). Two characters also distinguish Pneophyllum from Dawsoniolithon: tetra/bisporangial conceptacle roof thickness (<8 cells in Pneophyllum vs. >8 cells in Dawsoniolithon) and thallus construction (dimerous in Pneophyllum vs. monomerous in Dawsoniolithon). 相似文献
994.
The Neotropical genus Menevia Schaus, 1928 is revised to include 18 species, 11 of which are new. Two species, Menevia
ostia
comb. n. and Menevia
parostia
comb. n. are transferred from Pamea Walker, 1855 to Menevia. Four species-groups are diagnosed for the first time based on external characters and male genitalia morphology. The following new species are described: Menevia
rosea
sp. n., Menevia
torvamessoria
sp. n., Menevia
magna
sp. n., Menevia
menapia
sp. n., Menevia
mielkei
sp. n., Menevia
australis
sp. n., Menevia
vulgaris
sp. n., Menevia
franclemonti
sp. n., Menevia
vulgaricula
sp. n., Menevia
cordillera
sp. n., and Menevia
delphinus
sp. n.. A neotype is designated for Mimallo
plagiata Walker, 1855, which has since been placed in Menevia. Mimallo
saturata Walker, 1855 is interpreted to be a nomen dubium. 相似文献
995.
Methodological improvements now allow routine analyses of highly degraded DNA samples as found in museum specimens. Using these methods could be useful in studying such groups as rodents of the genus Gerbillus for which i) the taxonomy is still highly debated, ii) collection of fresh specimens may prove difficult. Here we address precise taxonomic questions using a small portion of the cytochrome b gene obtained from 45 dry skin/skull museum samples (from 1913 to 1974) originating from two African and three Asian countries. The specimens were labelled Gerbillus
gerbillus, Gerbillus
andersoni, Gerbillus
nanus, Gerbillus
amoenus, Gerbillus
perpallidus and Gerbillus
pyramidum, and molecular results mostly confirmed these assignations. The close relationship between Gerbillus
nanus (Asian origin) and Gerbillus
amoenus (African origin) confirmed that they represent vicariant sibling species which differentiated in allopatry on either side of the Red Sea. In the closely related Gerbillus
perpallidus and Gerbillus
pyramidum, specimens considered as belonging to one Gerbillus
pyramidum subspecies (Gerbillus
pyramidum
floweri) appeared closer to Gerbillus
perpallidus suggesting that they (Gerbillus
pyramidum
floweri and Gerbillus
perpallidus) may represent a unique species, distributed on both sides of the Nile River, for which the correct name should be Gerbillus
floweri. Furthermore, the three other Gerbillus
pyramidum subspecies grouped together with no apparent genetic structure suggesting that they may not yet represent genetically differentiated lineages. This study confirms the importance of using these methods on museum samples, which can open new perspectives in this particular group as well as in other groups of interest. 相似文献
996.
Human activities and climate variability drive fast‐paced change across the world's estuarine–coastal ecosystems 下载免费PDF全文
James E. Cloern Paulo C. Abreu Jacob Carstensen Laurent Chauvaud Ragnar Elmgren Jacques Grall Holly Greening John Olov Roger Johansson Mati Kahru Edward T. Sherwood Jie Xu Kedong Yin 《Global Change Biology》2016,22(2):513-529
Time series of environmental measurements are essential for detecting, measuring and understanding changes in the Earth system and its biological communities. Observational series have accumulated over the past 2–5 decades from measurements across the world's estuaries, bays, lagoons, inland seas and shelf waters influenced by runoff. We synthesize information contained in these time series to develop a global view of changes occurring in marine systems influenced by connectivity to land. Our review is organized around four themes: (i) human activities as drivers of change; (ii) variability of the climate system as a driver of change; (iii) successes, disappointments and challenges of managing change at the sea‐land interface; and (iv) discoveries made from observations over time. Multidecadal time series reveal that many of the world's estuarine–coastal ecosystems are in a continuing state of change, and the pace of change is faster than we could have imagined a decade ago. Some have been transformed into novel ecosystems with habitats, biogeochemistry and biological communities outside the natural range of variability. Change takes many forms including linear and nonlinear trends, abrupt state changes and oscillations. The challenge of managing change is daunting in the coastal zone where diverse human pressures are concentrated and intersect with different responses to climate variability over land and over ocean basins. The pace of change in estuarine–coastal ecosystems will likely accelerate as the human population and economies continue to grow and as global climate change accelerates. Wise stewardship of the resources upon which we depend is critically dependent upon a continuing flow of information from observations to measure, understand and anticipate future changes along the world's coastlines. 相似文献
997.
Comparing concentration‐based (AOT40) and stomatal uptake (PODY) metrics for ozone risk assessment to European forests 下载免费PDF全文
Alessandro Anav Alessandra De Marco Chiara Proietti Andrea Alessandri Alessandro Dell'Aquila Irene Cionni Pierre Friedlingstein Dmitry Khvorostyanov Laurent Menut Elena Paoletti Pierre Sicard Stephen Sitch Marcello Vitale 《Global Change Biology》2016,22(4):1608-1627
Tropospheric ozone (O3) produces harmful effects to forests and crops, leading to a reduction of land carbon assimilation that, consequently, influences the land sink and the crop yield production. To assess the potential negative O3 impacts to vegetation, the European Union uses the Accumulated Ozone over Threshold of 40 ppb (AOT40). This index has been chosen for its simplicity and flexibility in handling different ecosystems as well as for its linear relationships with yield or biomass loss. However, AOT40 does not give any information on the physiological O3 uptake into the leaves since it does not include any environmental constraints to O3 uptake through stomata. Therefore, an index based on stomatal O3 uptake (i.e. PODY), which describes the amount of O3 entering into the leaves, would be more appropriate. Specifically, the PODY metric considers the effects of multiple climatic factors, vegetation characteristics and local and phenological inputs rather than the only atmospheric O3 concentration. For this reason, the use of PODY in the O3 risk assessment for vegetation is becoming recommended. We compare different potential O3 risk assessments based on two methodologies (i.e. AOT40 and stomatal O3 uptake) using a framework of mesoscale models that produces hourly meteorological and O3 data at high spatial resolution (12 km) over Europe for the time period 2000–2005. Results indicate a remarkable spatial and temporal inconsistency between the two indices, suggesting that a new definition of European legislative standard is needed in the near future. Besides, our risk assessment based on AOT40 shows a good consistency compared to both in‐situ data and other model‐based datasets. Conversely, risk assessment based on stomatal O3 uptake shows different spatial patterns compared to other model‐based datasets. This strong inconsistency can be likely related to a different vegetation cover and its associated parameterizations. 相似文献
998.
999.
Fabiana Dal Pozzo Bénédicte Renaville Ludovic Martinelle Robert Renaville Christine Thys Fran?ois Smeets Nathalie Kirschvink Fabien Grégoire Laurent Delooz Guy Czaplicki Claude Saegerman 《Applied and environmental microbiology》2016,82(1):81-86
The genotypic characterization of Coxiella burnetii provides useful information about the strains circulating at the farm, region, or country level and may be used to identify the source of infection for animals and humans. The aim of the present study was to investigate the strains of C. burnetii circulating in caprine and bovine Belgian farms using a single nucleotide polymorphism (SNP) technique. Direct genotyping was applied to different samples (bulk tank milk, individual milk, vaginal swab, fetal product, and air sample). Besides the well-known SNP genotypes, unreported ones were found in bovine and caprine samples, increasing the variability of the strains found in the two species in Belgium. Moreover, multiple genotypes were detected contemporarily in caprine farms at different years of sampling and by using different samples. Interestingly, certain SNP genotypes were detected in both bovine and caprine samples, raising the question of interspecies transmission of the pathogen. 相似文献
1000.
Georges St. Laurent Yuri Vyatkin Denis Antonets Maxim Ri Yao Qi Olga Saik Dmitry Shtokalo Michiel?J.L. de?Hoon Hideya Kawaji Masayoshi Itoh Timo Lassmann Erik Arner Alistair R.R. Forrest The FANTOM consortium Estelle Nicolas Timothy A. McCaffrey Piero Carninci Yoshihide Hayashizaki Claes Wahlestedt Philipp Kapranov 《Nucleic acids research》2016,44(7):3233-3252