全文获取类型
收费全文 | 4126篇 |
免费 | 332篇 |
国内免费 | 2篇 |
专业分类
4460篇 |
出版年
2023年 | 24篇 |
2022年 | 59篇 |
2021年 | 108篇 |
2020年 | 56篇 |
2019年 | 74篇 |
2018年 | 116篇 |
2017年 | 84篇 |
2016年 | 151篇 |
2015年 | 198篇 |
2014年 | 246篇 |
2013年 | 320篇 |
2012年 | 390篇 |
2011年 | 334篇 |
2010年 | 223篇 |
2009年 | 180篇 |
2008年 | 243篇 |
2007年 | 212篇 |
2006年 | 194篇 |
2005年 | 184篇 |
2004年 | 171篇 |
2003年 | 148篇 |
2002年 | 138篇 |
2001年 | 25篇 |
2000年 | 27篇 |
1999年 | 34篇 |
1998年 | 45篇 |
1997年 | 17篇 |
1996年 | 22篇 |
1995年 | 18篇 |
1994年 | 21篇 |
1993年 | 17篇 |
1992年 | 19篇 |
1991年 | 14篇 |
1990年 | 22篇 |
1989年 | 18篇 |
1988年 | 15篇 |
1987年 | 15篇 |
1985年 | 11篇 |
1984年 | 25篇 |
1983年 | 14篇 |
1982年 | 17篇 |
1981年 | 16篇 |
1980年 | 18篇 |
1979年 | 17篇 |
1978年 | 16篇 |
1977年 | 8篇 |
1974年 | 7篇 |
1973年 | 7篇 |
1964年 | 7篇 |
1962年 | 7篇 |
排序方式: 共有4460条查询结果,搜索用时 15 毫秒
71.
Sander A.B. Weelink Wim van Doesburg Flávia Talarico Saia W. Irene C. Rijpstra Wilfred F.M. Röling Hauke Smidt & Alfons J.M. Stams 《FEMS microbiology ecology》2009,70(3):243-253
A bacterium (strain G5G6) that grows anaerobically with toluene was isolated from a polluted aquifer (Banisveld, the Netherlands). The bacterium uses Fe(III), Mn(IV) and nitrate as terminal electron acceptors for growth on aromatic compounds. The bacterium does not grow on sugars, lactate or acetate. Phylogenetic analysis of the 16S rRNA gene sequence indicated that strain G5G6 belonged to the Betaproteobacteria . Its closest, but only distantly related, cultured relative is Sterolibacterium denitrificans Chol-1ST (94.6% similarity of the 16S rRNA genes), a cholesterol-oxidizing, denitrifying bacterium. Strain G5G6 possesses the benzylsuccinate synthase A ( bssA ) gene encoding the α-subunit of Bss, which catalyzes the first step in anaerobic toluene degradation. The deduced BssA amino acid sequence is closely related to those of Azoarcus and Thauera species, which also belong to the Betaproteobacteria . Strain G5G6 is the first toluene-degrading, iron-reducing bacterium that does not belong to the Geobacteraceae within the Deltaproteobacteria . Based on phylogenetic and physiological comparison, strain G5G6 could not be assigned to a described species. Therefore, strain G5G6 (DSMZ 19032T =JCM 14632T ) is a novel taxon of the Betaproteobacteria . We propose the name Georgfuchsia toluolica gen. nov., sp. nov. 相似文献
72.
B.C. Okeke A. Paterson J.E. Smith Irene A. Watson-Craik 《Letters in applied microbiology》1994,19(4):284-287
Ligninolytic activities in strains of Lentinula edodes were related to pentachlorophenol biotransformation in sterile soil and activities in L. lepideus. Strains of L. edodes secreting laccase and manganese peroxidase activities also metabolized pentachlorophenol (PCP) significantly ( P < 0.05). Strains of L. lepideus showed neither enzymic activities nor xenobiotic breakdown. Lentinula edodes strains inhibited by PCP at 5 mg 1-1 in agar, tolerated 200 mg kg-1 in soil. Strain LE2 metabolized more PCP in nitrogen-sufficient than nitrogen-limited culture: the reverse was observed with Phanerochaete chrysosporium BKM 1767. Relationships between ligninolytic activities and pentachlorophenol breakdown in L. edodes indicated a suitability for soil bioremediation treatments. 相似文献
73.
Catherine M. Hall Nigel A. Adams J. Stuart Bradley Kate A. Bryant Alisa A. Davis Christopher R. Dickman Tsumugi Fujita Shinichi Kobayashi Christopher A. Lepczyk E. Anne McBride Kenneth H. Pollock Irene M. Styles Yolanda van Heezik Ferian Wang Michael C. Calver 《PloS one》2016,11(4)
International differences in practices and attitudes regarding pet cats'' interactions with wildlife were assessed by surveying citizens from at least two cities in Australia, New Zealand, the UK, the USA, China and Japan. Predictions tested were: (i) cat owners would agree less than non-cat owners that cats might threaten wildlife, (ii) cat owners value wildlife less than non-cat owners, (iii) cat owners are less accepting of cat legislation/restrictions than non-owners, and (iv) respondents from regions with high endemic biodiversity (Australia, New Zealand, China and the USA state of Hawaii) would be most concerned about pet cats threatening wildlife. Everywhere non-owners were more likely than owners to agree that pet cats killing wildlife were a problem in cities, towns and rural areas. Agreement amongst non-owners was highest in Australia (95%) and New Zealand (78%) and lowest in the UK (38%). Irrespective of ownership, over 85% of respondents from all countries except China (65%) valued wildlife in cities, towns and rural areas. Non-owners advocated cat legislation more strongly than owners except in Japan. Australian non-owners were the most supportive (88%), followed by Chinese non-owners (80%) and Japanese owners (79.5%). The UK was least supportive (non-owners 43%, owners 25%). Many Australian (62%), New Zealand (51%) and Chinese owners (42%) agreed that pet cats killing wildlife in cities, towns and rural areas was a problem, while Hawaiian owners were similar to the mainland USA (20%). Thus high endemic biodiversity might contribute to attitudes in some, but not all, countries. Husbandry practices varied internationally, with predation highest where fewer cats were confined. Although the risk of wildlife population declines caused by pet cats justifies precautionary action, campaigns based on wildlife protection are unlikely to succeed outside Australia or New Zealand. Restrictions on roaming protect wildlife and benefit cat welfare, so welfare is a better rationale. 相似文献
74.
Acceleration of cyanobacterial dominance in north temperate‐subarctic lakes during the Anthropocene 下载免费PDF全文
Zofia E. Taranu Irene Gregory‐Eaves Peter R. Leavitt Lynda Bunting Teresa Buchaca Jordi Catalan Isabelle Domaizon Piero Guilizzoni Andrea Lami Suzanne McGowan Heather Moorhouse Giuseppe Morabito Frances R. Pick Mark A. Stevenson Patrick L. Thompson Rolf D. Vinebrooke 《Ecology letters》2015,18(4):375-384
Increases in atmospheric temperature and nutrients from land are thought to be promoting the expansion of harmful cyanobacteria in lakes worldwide, yet to date there has been no quantitative synthesis of long‐term trends. To test whether cyanobacteria have increased in abundance over the past ~ 200 years and evaluate the relative influence of potential causal mechanisms, we synthesised 108 highly resolved sedimentary time series and 18 decadal‐scale monitoring records from north temperate‐subarctic lakes. We demonstrate that: (1) cyanobacteria have increased significantly since c. 1800 ce , (2) they have increased disproportionately relative to other phytoplankton, and (3) cyanobacteria increased more rapidly post c. 1945 ce . Variation among lakes in the rates of increase was explained best by nutrient concentration (phosphorus and nitrogen), and temperature was of secondary importance. Although cyanobacterial biomass has declined in some managed lakes with reduced nutrient influx, the larger spatio‐temporal scale of sedimentary records show continued increases in cyanobacteria throughout the north temperate‐subarctic regions. 相似文献
75.
Collecting and storing biological material from wild animals in a way that does not deteriorate DNA quality for subsequent analyses is instrumental for research in ecology and evolution. Our aims were to gather reports on the effectiveness of methods commonly used by researchers for the field collection and long‐term storage of blood samples and DNA extracts from wild birds. Personal experiences were collected with an online survey targeted specifically at researchers sampling wild birds. Many researchers experienced problems with blood sample storage but not with DNA extract storage. Storage issues generated problems with obtaining adequate DNA quality and sufficient DNA quantity for the targeted molecular analyses but were not related to season of blood sampling, access to equipment, transporting samples, temperature, and method of blood storage. Final DNA quality and quantity were also not affected by storage time before DNA extraction or the methods used to extract DNA. We discuss practical aspects of field collection and storage and provide some general recommendations, with a list of pros and cons of different preservation methods of avian blood samples and DNA extracts. 相似文献
76.
Gregor Buch Andreas Schulz Irene Schmidtmann Konstantin Strauch Philipp S. Wild 《Biometrical journal. Biometrische Zeitschrift》2024,66(2):2300063
Variable selection is usually performed to increase interpretability, as sparser models are easier to understand than full models. However, a focus on sparsity is not always suitable, for example, when features are related due to contextual similarities or high correlations. Here, it may be more appropriate to identify groups and their predictive members, a task that can be accomplished with bi-level selection procedures. To investigate whether such techniques lead to increased interpretability, group exponential LASSO (GEL), sparse group LASSO (SGL), composite minimax concave penalty (cMCP), and least absolute shrinkage, and selection operator (LASSO) as reference methods were used to select predictors in time-to-event, regression, and classification tasks in bootstrap samples from a cohort of 1001 patients. Different groupings based on prior knowledge, correlation structure, and random assignment were compared in terms of selection relevance, group consistency, and collinearity tolerance. The results show that bi-level selection methods are superior to LASSO in all criteria. The cMCP demonstrated superiority in selection relevance, while SGL was convincing in group consistency. An all-round capacity was achieved by GEL: the approach jointly selected correlated and content-related predictors while maintaining high selection relevance. This method seems recommendable when variables are grouped, and interpretation is of primary interest. 相似文献
77.
78.
79.
Loss of functional residual capacity in poliomyelitis 总被引:1,自引:0,他引:1
80.