全文获取类型
收费全文 | 2245篇 |
免费 | 173篇 |
出版年
2023年 | 12篇 |
2022年 | 16篇 |
2021年 | 27篇 |
2020年 | 11篇 |
2019年 | 30篇 |
2018年 | 32篇 |
2017年 | 25篇 |
2016年 | 62篇 |
2015年 | 85篇 |
2014年 | 90篇 |
2013年 | 137篇 |
2012年 | 155篇 |
2011年 | 173篇 |
2010年 | 115篇 |
2009年 | 94篇 |
2008年 | 140篇 |
2007年 | 133篇 |
2006年 | 122篇 |
2005年 | 95篇 |
2004年 | 115篇 |
2003年 | 99篇 |
2002年 | 91篇 |
2001年 | 13篇 |
2000年 | 21篇 |
1999年 | 31篇 |
1998年 | 33篇 |
1997年 | 20篇 |
1996年 | 31篇 |
1995年 | 20篇 |
1994年 | 25篇 |
1993年 | 12篇 |
1992年 | 28篇 |
1991年 | 18篇 |
1990年 | 19篇 |
1989年 | 11篇 |
1988年 | 11篇 |
1987年 | 14篇 |
1986年 | 13篇 |
1985年 | 17篇 |
1984年 | 15篇 |
1983年 | 13篇 |
1982年 | 24篇 |
1981年 | 23篇 |
1980年 | 13篇 |
1979年 | 18篇 |
1978年 | 9篇 |
1977年 | 9篇 |
1976年 | 10篇 |
1974年 | 8篇 |
1973年 | 10篇 |
排序方式: 共有2418条查询结果,搜索用时 31 毫秒
61.
62.
63.
Mendoza Beltran Angelica Scheel Claus Nordstrøm Fitton Nuala Schmidt Jannick Kløverpris Jesper Hedal 《The International Journal of Life Cycle Assessment》2021,26(8):1570-1585
The International Journal of Life Cycle Assessment - To estimate life cycle impacts from introducing the yield-enhancing inoculant containing the nitrogen-fixing bacterium Bradyrhizobium japonicum... 相似文献
64.
Anthi Katsiarimpa Kamila Kalinowska Franziska Anzenberger Corina Weis Maya Ostertag Chie Tsutsumi Claus Schwechheimer Frédéric Brunner Ralph Hückelhoven Erika Isono 《The Plant cell》2013,25(6):2236-2252
In eukaryotes, posttranslational modification by ubiquitin regulates the activity and stability of many proteins and thus influences a variety of developmental processes as well as environmental responses. Ubiquitination also plays a critical role in intracellular trafficking by serving as a signal for endocytosis. We have previously shown that the Arabidopsis thaliana ASSOCIATED MOLECULE WITH THE SH3 DOMAIN OF STAM3 (AMSH3) is a deubiquitinating enzyme (DUB) that interacts with ENDOSOMAL COMPLEX REQUIRED FOR TRANSPORT-III (ESCRT-III) and is essential for intracellular transport and vacuole biogenesis. However, physiological functions of AMSH3 in the context of its ESCRT-III interaction are not well understood due to the severe seedling lethal phenotype of its null mutant. In this article, we show that Arabidopsis AMSH1, an AMSH3-related DUB, interacts with the ESCRT-III subunit VACUOLAR PROTEIN SORTING2.1 (VPS2.1) and that impairment of both AMSH1 and VPS2.1 causes early senescence and hypersensitivity to artificial carbon starvation in the dark similar to previously reported autophagy mutants. Consistent with this, both mutants accumulate autophagosome markers and accumulate less autophagic bodies in the vacuole. Taken together, our results demonstrate that AMSH1 and the ESCRT-III-subunit VPS2.1 are important for autophagic degradation and autophagy-mediated physiological processes. 相似文献
65.
Omera B. Matoo Anna V. Ivanina Claus Ullstad Elia Beniash Inna M. Sokolova 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2013,164(4):545-553
Marine bivalves such as the hard shell clams Mercenaria mercenaria and eastern oysters Crassostrea virginica are affected by multiple stressors, including fluctuations in temperature and CO2 levels in estuaries, and these stresses are expected to be exacerbated by ongoing global climate change. Hypercapnia (elevated CO2 levels) and temperature stress can affect survival, growth and development of marine bivalves, but the cellular mechanisms of these effects are not yet fully understood. In this study, we investigated whether oxidative stress is implicated in cellular responses to elevated temperature and CO2 levels in marine bivalves. We measured the whole-organism standard metabolic rate (SMR), total antioxidant capacity (TAOC), and levels of oxidative stress biomarkers in the muscle tissues of clams and oysters exposed to different temperatures (22 and 27 °C) and CO2 levels (the present day conditions of ~ 400 ppm CO2 and 800 ppm CO2 predicted by a consensus business-as-usual IPCC emission scenario for the year 2100). SMR was significantly higher and the antioxidant capacity was lower in oysters than in clams. Aerobic metabolism was largely temperature-independent in these two species in the studied temperature range (22–27 °C). However, the combined exposure to elevated temperature and hypercapnia led to elevated SMR in clams indicating elevated costs of basal maintenance. No persistent oxidative stress signal (measured by the levels of protein carbonyls, and protein conjugates with malondialdehyde and 4-hydroxynonenal) was observed during the long-term exposure to moderate warming (+ 5 °C) and hypercapnia (~ 800 ppm CO2). This indicates that long-term exposure to moderately elevated CO2 and temperature minimally affects the cellular redox status in these bivalve species and that the earlier observed negative physiological effects of elevated CO2 and temperature must be explained by other cellular mechanisms. 相似文献
66.
While physicists regularly use mathematical equations to describe natural phenomena, mathematical modeling of biological systems is still not well established and is hampered by communication barriers between experimental and theoretical biologists. In a recent study we developed a mathematical model of zinc uptake and radial transport in Arabidopsis thaliana roots. By refraining from writing many equations in the main text and confining the derivation of formulas to a supplemental file, we attempted to reach both experimentalists and theoreticians likewise. Here, we give a short summary of our results on the accumulation pattern of zinc and the importance of transporter regulation, water flow and geometry. For a better understanding of the dynamics of adaptation to changes in external conditions, we plead for more detailed and frequent measurements. As a new aspect, we analyzed the effect of buffering. Simulations indicate that it dampens oscillations and may therefore play a key role in zinc homeostasis. 相似文献
67.
The formation of the complex network architecture of neural systems is subject to multiple structural and functional constraints. Two obvious but apparently contradictory constraints are low wiring cost and high processing efficiency, characterized by short overall wiring length and a small average number of processing steps, respectively. Growing evidence shows that neural networks are results from a trade-off between physical cost and functional value of the topology. However, the relationship between these competing constraints and complex topology is not well understood quantitatively. We explored this relationship systematically by reconstructing two known neural networks, Macaque cortical connectivity and C. elegans neuronal connections, from combinatory optimization of wiring cost and processing efficiency constraints, using a control parameter , and comparing the reconstructed networks to the real networks. We found that in both neural systems, the reconstructed networks derived from the two constraints can reveal some important relations between the spatial layout of nodes and the topological connectivity, and match several properties of the real networks. The reconstructed and real networks had a similar modular organization in a broad range of , resulting from spatial clustering of network nodes. Hubs emerged due to the competition of the two constraints, and their positions were close to, and partly coincided, with the real hubs in a range of values. The degree of nodes was correlated with the density of nodes in their spatial neighborhood in both reconstructed and real networks. Generally, the rebuilt network matched a significant portion of real links, especially short-distant ones. These findings provide clear evidence to support the hypothesis of trade-off between multiple constraints on brain networks. The two constraints of wiring cost and processing efficiency, however, cannot explain all salient features in the real networks. The discrepancy suggests that there are further relevant factors that are not yet captured here. 相似文献
68.
Quan-Xiang Wei Rainer Claus Thomas Hielscher Daniel Mertens Aparna Raval Christopher C. Oakes Stephan M. Tanner Albert de la Chapelle John C. Byrd Stephan Stilgenbauer Christoph Plass 《PloS one》2013,8(1)
We previously reported a rare germline variant (c.1-6531) that resulted in allele–specific expression (ASE) of death-associated protein kinase 1 (DAPK1) and predisposition to chronic lymphocytic leukemia (CLL). We investigated a cohort of CLL patients lacking this mutation for the presence of ASE of DAPK1. We developed a novel strategy that combines single-nucleotide primer extension (SNuPE) with MALDI-TOF mass spectrometry, and detected germline DAPK1 ASE in 17 out of 120 (14.2%) CLL patients associated with a trend towards younger age at diagnosis. ASE was absent in 63 healthy controls. Germline cells of CLL patients with ASE showed increased levels of DNA methylation in the promoter region, however, neither genetic nor further epigenetic aberrations could be identified in the DAPK1 5′ upstream regulatory region, within distinct exons or in the 3′-UTR. We identified B-lymphoid malignancy related cell line models harboring allelic imbalance and found that allele-specific methylation in DAPK1 is associated with ASE. Our data indicate that ASE at the DAPK1 gene locus is a recurrent event, mediated by epigenetic mechanisms and potentially predisposing to CLL. 相似文献
69.
Brain metastases (BM) occur in 20% to 40% of patients with cancer and result in significant morbidity and poor survival. The main therapeutic options include surgery, whole brain radiotherapy, stereotactic radiosurgery and chemotherapy. Although significant progress has been made in diagnostic and therapeutic methods, the prognosis in these patients remains poor. Furthermore, the poor penetrability of chemotherapy agents through the blood brain barrier (BBB) continues to pose a challenge in the management of this disease. Preclinical evidence suggests that new targeted treatments can improve local tumor control but our clinical experience with these agents remains limited. In addition, several clinical studies with these novel agents have produced disappointing results. This review will examine the knowledge of targeted therapies in BM. The preclinical and clinical evidence of their use in BM induced by breast cancer, non-small cell lung cancer and melanoma will be presented. In addition, we will discuss the role of antiangiogenic and radiosensitising agents in the treatment of BM and the current strategies available to increase BBB permeability. A better understanding of the mechanism of action of these agents will help us to identify the best targets for testing in future clinical studies. 相似文献
70.
Nathaniel Edward Bennett Saidu Imad Abu Asali Brigitte Czepukojc Berthold Seitz Claus Jacob Mathias Montenarh 《Biochimica et Biophysica Acta (BBA)/General Subjects》2013