全文获取类型
收费全文 | 22111篇 |
免费 | 1527篇 |
国内免费 | 9篇 |
出版年
2023年 | 126篇 |
2022年 | 317篇 |
2021年 | 582篇 |
2020年 | 353篇 |
2019年 | 471篇 |
2018年 | 595篇 |
2017年 | 480篇 |
2016年 | 815篇 |
2015年 | 1219篇 |
2014年 | 1351篇 |
2013年 | 1664篇 |
2012年 | 1956篇 |
2011年 | 1896篇 |
2010年 | 1178篇 |
2009年 | 1021篇 |
2008年 | 1378篇 |
2007年 | 1295篇 |
2006年 | 1184篇 |
2005年 | 1083篇 |
2004年 | 984篇 |
2003年 | 927篇 |
2002年 | 754篇 |
2001年 | 123篇 |
2000年 | 110篇 |
1999年 | 142篇 |
1998年 | 129篇 |
1997年 | 117篇 |
1996年 | 93篇 |
1995年 | 90篇 |
1994年 | 96篇 |
1993年 | 90篇 |
1992年 | 57篇 |
1991年 | 62篇 |
1990年 | 64篇 |
1989年 | 48篇 |
1988年 | 54篇 |
1987年 | 38篇 |
1986年 | 43篇 |
1985年 | 51篇 |
1984年 | 43篇 |
1983年 | 45篇 |
1982年 | 36篇 |
1981年 | 45篇 |
1980年 | 29篇 |
1979年 | 36篇 |
1978年 | 34篇 |
1977年 | 32篇 |
1976年 | 30篇 |
1975年 | 25篇 |
1973年 | 30篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Knudsen Rune Eloranta Antti P. Siwertsson Anna Paterson Rachel A. Power Michael Sandlund Odd Terje 《Hydrobiologia》2019,829(1):245-263
Hydrobiologia - Understanding the concordance between aquatic assemblages in ecological assessments and their responses to human-induced disturbances are fundamental steps toward achieving... 相似文献
992.
Moccetti Paolo Siwertsson Anna Kjær Runar Amundsen Per-Arne Præbel Kim Tamayo Ana-Maria Peris Power Michael Knudsen Rune 《Hydrobiologia》2019,829(1):281-290
Hydrobiologia - Lipid biomarkers in sediments, which are indicative of biological production, provide important information regarding the environmental conditions in and around lakes, and can be... 相似文献
993.
Magdalena Remisiewicz Zephné Bernitz Herman Bernitz Marc S. Burman Jacobus M.H. Raijmakers Johannes H.F.A. Raijmakers Les G. Underhill Anna Rostkowska Yahkat Barshep Sergej A. Soloviev Ilona Siwek 《Ibis》2019,161(4):824-838
Trade‐offs between moult and fuelling in migrant birds vary with migration distance and the environmental conditions they encounter. We compared wing moult and fuelling at the northern and southern ends of migration in two populations of adult Common Whitethroats Sylvia communis. The western population moults most remiges at the breeding grounds in Europe (e.g. Poland) and migrates 4000–5000 km to western Africa (e.g. Nigeria). The eastern population moults all remiges at the non‐breeding grounds and migrates 7000–10 000 km from western Asia (e.g. southwestern Siberia) to eastern and southern Africa. We tested the hypotheses that: (1) Whitethroats moult their wing feathers slowly in South Africa, where they face fewer time constraints than in Poland, and (2) fuelling is slower when it coincides with moulting (Poland, South Africa) than when it occurs alone (Siberia, Nigeria). We estimated moult timing of primaries, secondaries and tertials from moult records of Polish and South African Whitethroats ringed in 1987–2017 and determined fuelling patterns from the body mass of Whitethroats ringed in all four regions. The western population moulted wing feathers in Poland over 55 days (2 July–26 August) at a varying rate, up to 13 feathers simultaneously, but fuelled slowly until departure in August–mid‐September. In Nigeria, during the drier period of mid‐February–March they fuelled slowly, but the fuelling rate increased three‐fold in April–May after the rains before mid‐April–May departure. The eastern population did not moult in Siberia but fuelled three times faster before mid‐July–early August departure than did the western birds moulting in Poland. In South Africa, the Whitethroats moulted over 57 days (2 January–28 February) at a constant rate of up to nine feathers simultaneously and fuelled slowly from mid‐December until mid‐April–May departure. These results suggest the two populations use contrasting strategies to capitalize on food supplies before departure from breeding and non‐breeding grounds. 相似文献
994.
Egor E. Diakonov Anastasiia V. Selenina Alexey N. Tomilin Anna S. Tsimokha 《Biochemical and biophysical research communications》2019,508(2):368-373
The ubiquitin proteasome system is involved in the regulation of most basic intracellular processes, and deregulation of this system can results in certain kinds of human diseases. Proteolytic core this system, the 20S proteasome, has been found in physiological fluids of both healthy humans and patients suffering from a variety of inflammatory, autoimmune, and neoplastic diseases. The concentration of these extracellular proteasomes has been found to correlate with the diseased state, being of a prognostic significance. The transport mechanisms and functions of these proteasomes, however, are largely unclear. Previous studies revealed that the transport of extracellular proteasomes may occur via microvesicles and exosomes, which led to the hypothesis that extracellular proteasomes are implicated in cell-to-cell communication process. Here we show that microvesicles and exosomes, two major known types of intercellular vehicles, contain no detectable proteasomes. Moreover, neither affinity purified nor naturally released into conditioned medium by donor cells 20S proteasomes could penetrate recipient HeLa cells. Taken together, these results suggest that extracellular proteasomes are unlikely to be involved in the cell-to-cell communication and that their release by cells serve other biological purposes. 相似文献
995.
996.
Hope T. Beier Caleb C. Roth Joel N. Bixler Anna V. Sedelnikova Bennett L. Ibey 《Biophysical journal》2019,116(1):120-126
Direct observation of rapid membrane potential changes is critical to understand how complex neurological systems function. This knowledge is especially important when stimulation is achieved through an external stimulus meant to mimic a naturally occurring process. To enable exploration of this dynamic space, we developed an all-optical method for observing rapid changes in membrane potential at temporal resolutions of ~25 ns. By applying a single 600-ns electric pulse, we observed sub-microsecond, continuous membrane charging and discharging dynamics. Close agreement between the acquired results and an analytical membrane-charging model validates the utility of this technique. This tool will deepen our understanding of the role of membrane potential dynamics in the regulation of many biological and chemical processes within living systems. 相似文献
997.
Robin Legner Alexander Wirtz Tim Koza Till Tetzlaff Anna Nickisch-Hartfiel Martin Jaeger 《Biotechnology and bioengineering》2019,116(11):2874-2883
Compact 1H NMR and Raman spectrometers were used for real-time process monitoring of alcoholic fermentation in a continuous flow reactor. Yeast cells catalyzing the sucrose conversion were immobilized in alginate beads floating in the reactor. The spectrometers proved to be robust and could be easily attached to the reaction apparatus. As environmentally friendly analysis methods, 1H NMR and Raman spectroscopy were selected to match the resource- and energy-saving process. Analyses took only a few seconds to minutes compared to chromatographic procedures and were, therefore, suitable for real-time control realized as a feedback loop. Both compact spectrometers were successfully implemented online. Raman spectroscopy allowed for faster spectral acquisition and higher quantitative precision, NMR yielded more resolved signals thus higher specificity. By using the software Matlab for automated data loading and processing, relevant parameters such as the ethanol, glycerol, and sugar content could be easily obtained. The subsequent multivariate data analysis using partial linear least-squares regression type 2 enabled the quantitative monitoring of all reactants within a single model in real time. 相似文献
998.
Photoautotrophic organisms are promising hosts for biocatalytic oxyfunctionalizations because they supply reduction equivalents as well as O2 via photosynthetic water oxidation. Thus far, research on photosynthesis-driven bioprocesses mainly focuses on strain development and the proof of principle in small-scale biocatalytic reaction setups. This study investigates the long-term applicability of the previously developed cyanobacterial strain Synechocystis sp. PCC 6803_BGT harboring the alkane monooxygenase system AlkBGT catalyzing terminal alkyl group oxyfunctionalization. For the regiospecific ω-hydroxylation of nonanoic acid methyl ester (NAME), this biocatalyst showed light intensity-independent hydroxylation activity and substantial hydrolysis of NAME to nonanoic acid. Substrate mass transfer limitation, substrate hydrolysis, as well as reactant toxicity were overcome via in situ substrate supply by means of a two-liquid phase system. The application of diisononyl phthalate as organic carrier solvent enabled 1.7-fold increased initial specific activities (5.6 ± 0.1 U/gCDW) and 7.6-fold increased specific yields on biomass (3.8 ± 0.1 mmolH-NAME/gCDW) as compared with single aqueous phase biotransformations. Finally, the whole-cell biotransformation system was successfully scaled from glass tubes to a stirred-tank photobioreactor. This is the first study reporting the application of the two-liquid phase concept for efficient phototrophic whole-cell biocatalysis. 相似文献
999.
1000.
Mirella Georgouli Cecilia Herraiz Eva Crosas-Molist Bruce Fanshawe Oscar Maiques Anna Perdrix Pahini Pandya Irene Rodriguez-Hernandez Kristina M. Ilieva Gaia Cantelli Panagiotis Karagiannis Silvia Mele Hoyin Lam Debra H. Josephs Xavier Matias-Guiu Rosa M. Marti Frank O. Nestle Jose L. Orgaz Victoria Sanz-Moreno 《Cell》2019,176(4):757-774.e23