全文获取类型
收费全文 | 3566篇 |
免费 | 259篇 |
国内免费 | 5篇 |
专业分类
3830篇 |
出版年
2023年 | 22篇 |
2022年 | 44篇 |
2021年 | 56篇 |
2020年 | 52篇 |
2019年 | 52篇 |
2018年 | 59篇 |
2017年 | 53篇 |
2016年 | 91篇 |
2015年 | 165篇 |
2014年 | 203篇 |
2013年 | 268篇 |
2012年 | 280篇 |
2011年 | 260篇 |
2010年 | 186篇 |
2009年 | 150篇 |
2008年 | 238篇 |
2007年 | 231篇 |
2006年 | 174篇 |
2005年 | 179篇 |
2004年 | 192篇 |
2003年 | 181篇 |
2002年 | 132篇 |
2001年 | 39篇 |
2000年 | 16篇 |
1999年 | 35篇 |
1998年 | 41篇 |
1997年 | 28篇 |
1996年 | 29篇 |
1995年 | 29篇 |
1994年 | 28篇 |
1993年 | 18篇 |
1992年 | 23篇 |
1991年 | 21篇 |
1990年 | 20篇 |
1989年 | 25篇 |
1988年 | 16篇 |
1987年 | 20篇 |
1986年 | 13篇 |
1985年 | 12篇 |
1984年 | 18篇 |
1983年 | 11篇 |
1982年 | 10篇 |
1981年 | 9篇 |
1980年 | 13篇 |
1979年 | 6篇 |
1978年 | 10篇 |
1976年 | 9篇 |
1975年 | 9篇 |
1974年 | 10篇 |
1973年 | 6篇 |
排序方式: 共有3830条查询结果,搜索用时 15 毫秒
71.
72.
Anita Herle 《Ethnos》2013,78(2):253-274
Preparations for a centenary exhibition to mark the 1898 Cambridge Anthropological Expedition to the Torres Strait incorporated cross-cultural collaborative work, reflecting the changing roles of museums as sites for contact and research combining curatorial expertise and indigenous knowledge. Specific objects in the collections of the University of Cambridge Museum of Archaeology and Anthropology continue to be active intermediaries in the relationship between museum staff and Torres Strait Islanders and the museum itself has become an important field site. This paper provides an ethnography of the process of creating the exhibition and explores different ways that many of the objects displayed have resonance for Islanders today. 相似文献
73.
Allison Lange Milo B. Fasken Murray Stewart Anita H. Corbett 《Traffic (Copenhagen, Denmark)》2020,21(10):622-635
The importin α/β transport machinery mediates the nuclear import of cargo proteins that bear a classical nuclear localization sequence (cNLS). These cargo proteins are linked to the major nuclear protein import factor, importin‐β, by the importin‐α adapter, after which cargo/carrier complexes enter the nucleus through nuclear pores. In the nucleus, cargo is released by the action of RanGTP and the nuclear pore protein Nup2, after which the importins are recycled to the cytoplasm for further transport cycles. The nuclear export of importin‐α is mediated by Cse1/CAS. Here, we exploit structures of functionally important complexes to identify residues that are critical for these interactions and provide insight into how cycles of protein import and recycling of importin‐α occur in vivo using a Saccharomyces cerevisiae model. We examine how these molecular interactions impact protein localization, cargo import, function and complex formation. We show that reversing the charge of key residues in importin‐α (Arg44) or Cse1 (Asp220) results in loss of function of the respective proteins and impairs complex formation both in vitro and in vivo. To extend these results, we show that basic residues in the Nup2 N‐terminus are required for both Nup2 interaction with importin‐α and Nup2 function. These results provide a more comprehensive mechanistic model of how Cse1, RanGTP and Nup2 function in concert to mediate cNLS‐cargo release in the nucleus. 相似文献
74.
Max Mallen‐Cooper Matthew A. Bowker Anita J. Antoninka David J. Eldridge 《Restoration Ecology》2020,28(Z2):S56-S66
Biocrusts are multifunctional communities that are increasingly being used to restore degraded or damaged ecosystems. Concurrently, restoration science is shifting away from the use of purely structural metrics, such as relative abundance, to more functional approaches. Although biocrust restoration technology is advancing, there is a lack of readily available information on how to monitor biocrust functioning and set appropriate restoration goals. We therefore compiled a selection of 22 functional indicators that can be used to monitor biocrust functions, such as CO2 exchange as an indicator of productivity or soil aggregate stability as a proxy for erosion resistance. We describe the functional importance of each indicator and the available protocols with which it may be measured. The majority of indicators can be measured as a functional trait of species by using patches of biocrust or cultures that contain only one species. Practitioners wishing to track the multifunctionality of an entire biocrust community would be advised to choose one indicator from each broad functional group (erosion resistance, nutrient accumulation, productivity, energy balance, hydrology), whereas a targeted approach would be more appropriate for projects with a key function of interest. Because predisturbance data are rarely available for biocrust functions, restoration goals can be based on a closely analogous site, literature values, or an expert elicitation process. Finally, we advocate for the establishment of a global trait database for biocrusts, which would reduce the damage resulting from repeated sampling, and provide a wealth of future research opportunities. 相似文献
75.
Colin Tucker Anita Antoninka Natalie Day Boris Poff Sasha Reed 《Restoration Ecology》2020,28(Z2):S9-S16
Biocrusts' functional importance and vulnerability to disturbance have motivated consistent interest in biocrust restoration, as well as a recent increase in research to cultivate biocrusts in laboratory and greenhouse settings for use in ecological restoration. As part of a sustainable approach to developing biocrust restoration, we argue that a complementary step is to improve and accelerate methods for salvaging biocrusts that would otherwise be destroyed in a forthcoming disturbance. The increasing rate and scale of disturbance pressures in drylands where biocrusts flourish means that the supply of salvageable biocrust and demand for that material in restoration greatly exceed the present cultivable supply. In this article we describe the state of knowledge for biocrust salvage, present a simple set of steps for conducting a salvage harvest, discuss risks and benefits when considering using salvage, and suggest future research directions to facilitate scaling up biocrust restoration using salvaged material. A focus on the use of salvaged biocrust as a restoration source may prove an important step to improve ecological restoration in notoriously difficult to restore dryland ecosystems. 相似文献
76.
Lauri Nikkanen Anita Santana Snchez Maria Ermakova Matthias Rgner Laurent Cournac Yagut Allahverdiyeva 《The Plant journal : for cell and molecular biology》2020,103(4):1460-1476
In oxygenic photosynthetic organisms, excluding angiosperms, flavodiiron proteins (FDPs) catalyze light‐dependent reduction of O2 to H2O. This alleviates electron pressure on the photosynthetic apparatus and protects it from photodamage. In Synechocystis sp. PCC 6803, four FDP isoforms function as hetero‐oligomers of Flv1 and Flv3 and/or Flv2 and Flv4. An alternative electron transport pathway mediated by the NAD(P)H dehydrogenase‐like complex (NDH‐1) also contributes to redox hemostasis and the photoprotection of photosynthesis. Four NDH‐1 types have been characterized in cyanobacteria: NDH‐11 and NDH‐12, which function in respiration; and NDH‐13 and NDH‐14, which function in CO2 uptake. All four types are involved in cyclic electron transport. Along with single FDP mutants (?flv1 and Δflv3) and the double NDH‐1 mutants (?d1d2, which is deficient in NDH‐11,2 and ?d3d4, which is deficient in NDH‐13,4), we studied triple mutants lacking one of Flv1 or Flv3, and NDH‐11,2 or NDH‐13,4. We show that the presence of either Flv1/3 or NDH‐11,2, but not NDH‐13,4, is indispensable for survival during changes in growth conditions from high CO2/moderate light to low CO2/high light. Our results show functional redundancy between FDPs and NDH‐11,2 under the studied conditions. We suggest that ferredoxin probably functions as a primary electron donor to both Flv1/3 and NDH‐11,2, allowing their functions to be dynamically coordinated for efficient oxidation of photosystem I and for photoprotection under variable CO2 and light availability. 相似文献
77.
Joaquín Gomis-Fons Hubert Schwarz Liang Zhang Niklas Andersson Bernt Nilsson Andreas Castan Anita Solbrand Joanne Stevenson Véronique Chotteau 《Biotechnology progress》2020,36(4):e2995
A continuous integrated bioprocess available from the earliest stages of process development allows for an easier, more efficient and faster development and characterization of an integrated process as well as production of small-scale drug candidates. The process presented in this article is a proof-of-concept of a continuous end-to-end monoclonal antibody production platform at a very small scale based on a 200 ml alternating tangential flow filtration perfusion bioreactor, integrated with the purification process with a model-based design and control. The downstream process, consisting of a periodic twin-column protein A capture, a virus inactivation, a CEX column and an AEX column, was compactly implemented in a single chromatography system, with a purification time of less than 4 hr. Monoclonal antibodies were produced for 17 days in a high cell density perfusion culture of CHO cells with titers up to 1.0 mg/ml. A digital twin of the downstream process was created by modelling all the chromatography steps. These models were used for real-time decision making by the implementation of control strategies to automatize and optimize the operation of the process. A consistent glycosylation pattern of the purified product was ensured by the steady state operation of the process. Regarding the removal of impurities, at least a 4-log reduction in the HCP levels was achieved. The recovery yield was up to 60%, and a maximum productivity of 0.8 mg/ml/day of purified product was obtained. 相似文献
78.
Lucy E. Ridding Adrian C. Newton Sally A. Keith Robin M. Walls Anita Diaz Richard F. Pywell James M. Bullock 《Ecography》2021,44(1):33-43
The extinction debt, delayed species extinctions following landscape degradation, is a widely discussed concept. But a consensus about the prevalence of extinctions debts is hindered by a multiplicity of methods and a lack of comparisons among habitats. We applied three contrasting species–area relationship methods to test for plant community extinction debts in three habitats which had different degradation histories over the last century: calcareous grassland, heathland and woodland. These methods differ in their data requirements, with the first two using information on past and current habitat area alongside current species richness, whilst the last method also requires data on past species richness. The most data‐intensive, and hence arguably most reliable method, identified extinction debts across all habitats for specialist species, whilst the other methods did not. All methods detected an extinction debt in calcareous grassland, which had undergone the most severe degradation. We conclude that some methods failed to detect an extinction debt, particularly in habitats that have undergone moderate degradation. Data on past species numbers are required for the most reliable method; as such data are rare, extinction debts may be under‐reported. 相似文献
79.
Amino Acids - Solid-phase synthesis of cyclic, branched or side-chain-modified peptides typically involves introduction of a residue carrying a temporary side-chain protecting group that undergoes... 相似文献