全文获取类型
收费全文 | 2428篇 |
免费 | 167篇 |
国内免费 | 2篇 |
专业分类
2597篇 |
出版年
2023年 | 11篇 |
2022年 | 27篇 |
2021年 | 49篇 |
2020年 | 44篇 |
2019年 | 51篇 |
2018年 | 58篇 |
2017年 | 45篇 |
2016年 | 75篇 |
2015年 | 104篇 |
2014年 | 91篇 |
2013年 | 176篇 |
2012年 | 182篇 |
2011年 | 209篇 |
2010年 | 134篇 |
2009年 | 116篇 |
2008年 | 162篇 |
2007年 | 167篇 |
2006年 | 137篇 |
2005年 | 137篇 |
2004年 | 121篇 |
2003年 | 93篇 |
2002年 | 99篇 |
2001年 | 15篇 |
2000年 | 12篇 |
1999年 | 13篇 |
1998年 | 18篇 |
1997年 | 18篇 |
1996年 | 8篇 |
1995年 | 8篇 |
1994年 | 8篇 |
1993年 | 16篇 |
1992年 | 12篇 |
1991年 | 7篇 |
1990年 | 19篇 |
1989年 | 14篇 |
1988年 | 7篇 |
1987年 | 11篇 |
1986年 | 9篇 |
1985年 | 11篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 10篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1978年 | 10篇 |
1975年 | 6篇 |
1974年 | 4篇 |
1973年 | 9篇 |
1972年 | 5篇 |
排序方式: 共有2597条查询结果,搜索用时 15 毫秒
71.
de Arruda Hélida Lídia Sousa dos Santos Juliana Ferrão Oliveira Albuquerque Ulysses Paulino Ramos Marcelo Alves 《Economic botany》2019,73(1):1-12
Economic Botany - We aim to evaluate whether socioeconomic factors influence the knowledge, use, preference, and consumption of firewood in a rural community in Northeast Brazil. We conducted... 相似文献
72.
Campos Juliana Loureiro Almeida de Lima Araújo Elcida Gaoue Orou G. Albuquerque Ulysses Paulino 《Economic botany》2019,73(2):187-199
Economic Botany - Socioeconomic Factors and Cultural Changes Explain the Knowledge and Use of Ouricuri Palm (Syagrus coronata) by the Fulni–ô Indigenous People of Northeast... 相似文献
73.
Hadiseh Dadras Sergey Boryshpolets Amin Golpour Tomas Policar Miroslav Blecha Borys Dzyuba 《Journal of fish biology》2019,95(4):1137-1144
Several factors regulating activation of spermatozoon motility in Eurasian burbot, Lota lota, including osmolality, calcium (Ca2+) ions, and temperature were investigated. Spermatozoon motility in Eurasian burbot, Lota lota was assessed at 4 and 30°C in seminal fluid, isotonic media (with and without Ca2+) and hypotonic media (with and without Ca2+). Spermatozoa were spontaneously activated in seminal fluid at 20°C and the maximum motility was recorded at 30°C, which is out of the spawning temperature range, indicating that no risk of activation occurs during routine semen handling in artificial insemination. Initiation of spermatozoon motility in L. lota is mediated by Ca2+ and sensitivity to Ca2+ is dependent on temperature. 相似文献
74.
Giorgio Perin Alessandra Bellan Andrea Bernardi Fabrizio Bezzo Tomas Morosinotto 《Physiologia plantarum》2019,166(1):380-391
The massive increase in carbon dioxide concentration in the atmosphere driven by human activities is causing huge negative consequences and new sustainable sources of energy, food and materials are highly needed. Algae are unicellular photosynthetic microorganisms that can provide a highly strategic contribution to this challenge as alternative source of biomass to complement crops cultivation. Algae industrial cultures are commonly limited by light availability, and biomass accumulation is strongly dependent on their photon‐to‐biomass conversion efficiency. Investigation of algae photosynthetic metabolism is thus strategic for the generation of more efficient strains with higher productivity. Algae are cultivated at industrial scale in conditions highly different from the natural niches they adapted to and strains development efforts must fully consider the seminal influence on productivity of regulatory mechanism of photosynthesis as well as of cultivation parameters like cells concentration, light distribution in the culture, mixing, nutrients and carbon dioxide availability. In this review we will focus in particular on how mathematical models can account for the complex influence of all environmental parameters and can be exploited for development of improved algae strains. 相似文献
75.
76.
Tomas Urbina Jean-Rmi Lavillegrand Marc Garnier Arsene Mekinian Jerome Pacanowski Nathalie Mario Guillaume Dumas Geoffroy Hariri Antoine Pilon Lucie Darrivre Muriel Fartoukh Bertrand Guidet Eric Maury Judith Leblanc Yannick Chantran Olivier Fain Karine Lacombe Guillaume Voiriot Hafid Ait-Oufella 《Innate immunity》2022,28(1):3
Little is known about the immuno-inflammatory response to Tocilizumab and its association with outcome in critically-ill SARS-CoV2 pneumonia. In this multicenter retrospective cohort of SARS-CoV-2 patients admitted to three intensive care units between March and April 2020, we matched on gender and SAPS II 21 Tocilizumab-treated patients to 42 non-treated patients. Need for mechanical ventilation was 76% versus 79%. IL-6, C-reactive protein, and fibrinogen had been collected within the first days of admission (T1), 3 d (T2) and 7 d (T3) later. Tocilizumab-treated patients had persistently higher IL-6 plasma levels and persistently lower C-Reactive protein and fibrinogen levels. Among Tocilizumab-treated patients, baseline levels of inflammatory biomarkers were not different according to outcome. Conversely, C-reactive protein and fibrinogen decrease was delayed in non-survivors. C-Reactive protein decreased at T1 in survivors (45 [30–98] vs 170 [69–204] mg/l, P < 0.001) but only at T2 in non-survivors (37 [13–74] vs 277 [235–288], P = 0.03). Fibrinogen decreased at T2 in survivors (4.11 [3.58–4.69] vs 614 [5.61–7.85] g/l, P = 0.005) but not in non-survivors (4.79 [4.12–7.58] vs 7.24 [6.22–9.24] g/l, P = 0.125). Tocilizumab treatment was thus associated with a persistent both increase in plasma IL-6, and decrease in C-reactive protein and fibrinogen. Among Tocilizumab-treated patients, the decrease in inflammatory biomarkers was delayed in non-survivors. 相似文献
77.
Gene-targeted mice lacking the Trex1 (DNase III) 3'-->5' DNA exonuclease develop inflammatory myocarditis 下载免费PDF全文
Morita M Stamp G Robins P Dulic A Rosewell I Hrivnak G Daly G Lindahl T Barnes DE 《Molecular and cellular biology》2004,24(15):6719-6727
TREX1, originally designated DNase III, was isolated as a major nuclear DNA-specific 3'-->5' exonuclease that is widely distributed in both proliferating and nonproliferating mammalian tissues. The cognate cDNA shows homology to the editing subunit of the Escherichia coli replicative DNA polymerase III holoenzyme and encodes an exonuclease which was able to serve a DNA-editing function in vitro, promoting rejoining of a 3' mismatched residue in a reconstituted DNA base excision repair system. Here we report the generation of gene-targeted Trex1(-/-) mice. The null mice are viable and do not show the increase in spontaneous mutation frequency or cancer incidence that would be predicted if Trex1 served an obligatory role of editing mismatched 3' termini generated during DNA repair or DNA replication in vivo. Unexpectedly, Trex1(-/-) mice exhibit a dramatically reduced survival and develop inflammatory myocarditis leading to progressive, often dilated, cardiomyopathy and circulatory failure. 相似文献
78.
79.
RNAs that localize to the vegetal cortex of Xenopus oocytes are involved in early embryonic patterning and cell fate specification. Two mechanistically distinct pathways lead to RNA enrichment at the vegetal cortex: the early and the late. While several candidate proteins that seem to operate in the late localization pathway have been identified, proteins involved in the early pathway remain to be identified. In this study, we report on the isolation of a novel vegetally localized RNA in Xenopus oocytes that makes use of the early pathway and encodes a protein with a conserved but functionally uncharacterized NIF-motif. The localization signal of XNIF was mapped to a 300-nucleotide region in the 5'-UTR, which is able to mediate both accumulation to the mitochondrial cloud in stage I oocytes, as well as vegetal transport in later stage oocytes. The XNIF-LE contains 16 copies of the previously defined CAC-containing signal motifs for RNA localization. A critical number of such repeats seems to be required for accumulation in the mitochondrial cloud along the early pathway, but additional repeats seem to be required for localization along the late pathway. Cross-linking experiments identify two novel proteins of 62 and 64 kDa that interact with the XNIF-LE but not with the Vg1-LE that operates in the late pathway. Conversely, at least two of the previously identified VgRBPs, Vg1RBP1 and Prrp, also bind to the XNIF-LE. Thus, overlapping, but not identical, protein machineries mediate vegetal RNA localization along early and late pathways in Xenopus oocytes. 相似文献
80.
Two experiments examined time/concentration trading for the detection of carbon dioxide, an irritant with little or no odor. Experiment 1 employed the nasal lateralization method: subjects attempted to determine which nostril received carbon dioxide and which received pure air when presented simultaneously. Experiment 2 employed a temporal, two-alternative, forced-choice, detection paradigm with monorhinal stimulation. In both experiments, stimulus duration was varied at a number of fixed concentrations to determine the shortest, detectable pulse. Under both conditions, threshold pulse duration decreased as stimulus concentration increased. Power functions with exponents of less than negative one described the data quite well: More than a twofold increase in duration was needed to compensate for a twofold decrease in concentration. Thus, for carbon dioxide, the nasal trigeminal system functions as an imperfect integrator at threshold-level. 相似文献