全文获取类型
收费全文 | 6295篇 |
免费 | 511篇 |
国内免费 | 2篇 |
专业分类
6808篇 |
出版年
2022年 | 46篇 |
2021年 | 71篇 |
2020年 | 35篇 |
2019年 | 69篇 |
2018年 | 62篇 |
2017年 | 86篇 |
2016年 | 145篇 |
2015年 | 197篇 |
2014年 | 243篇 |
2013年 | 370篇 |
2012年 | 394篇 |
2011年 | 402篇 |
2010年 | 283篇 |
2009年 | 299篇 |
2008年 | 396篇 |
2007年 | 411篇 |
2006年 | 396篇 |
2005年 | 387篇 |
2004年 | 390篇 |
2003年 | 412篇 |
2002年 | 384篇 |
2001年 | 70篇 |
2000年 | 52篇 |
1999年 | 86篇 |
1998年 | 130篇 |
1997年 | 86篇 |
1996年 | 72篇 |
1995年 | 84篇 |
1994年 | 64篇 |
1993年 | 57篇 |
1992年 | 65篇 |
1991年 | 52篇 |
1990年 | 39篇 |
1989年 | 34篇 |
1988年 | 33篇 |
1987年 | 22篇 |
1986年 | 22篇 |
1985年 | 27篇 |
1984年 | 37篇 |
1983年 | 16篇 |
1982年 | 33篇 |
1981年 | 28篇 |
1980年 | 33篇 |
1979年 | 30篇 |
1978年 | 19篇 |
1977年 | 20篇 |
1976年 | 19篇 |
1975年 | 18篇 |
1974年 | 15篇 |
1972年 | 15篇 |
排序方式: 共有6808条查询结果,搜索用时 15 毫秒
61.
Alain Dejean Arthur Compin Maurice Leponce Frédéric Azémar Camille Bonhomme Stanislas Talaga Laurent Pelozuelo Yann Hénaut Bruno Corbara 《Comptes rendus biologies》2018,341(3):200-207
In an inundated Mexican forest, 89 out of 92 myrmecophytic tank bromeliads (Aechmea bracteata) housed an associated ant colony: 13 sheltered Azteca serica, 43 Dolichoderus bispinosus, and 33 Neoponera villosa. Ant presence has a positive impact on the diversity of the aquatic macroinvertebrate communities (n = 30 bromeliads studied). A Principal Component Analysis (PCA) showed that the presence and the species of ant are not correlated to bromeliad size, quantity of water, number of wells, filtered organic matter or incident radiation. The PCA and a generalized linear model showed that the presence of Azteca serica differed from the presence of the other two ant species or no ants in its effects on the aquatic invertebrate community (more predators). Therefore, both ant presence and species of ant affect the composition of the aquatic macroinvertebrate communities in the tanks of A. bracteata, likely due to ant deposition of feces and other waste in these tanks. 相似文献
62.
Marie-Odile Parat Marie-Jeanne Richard Marie Th r se Leccia Pierre Amblard Alain Favier Jean Claude B ani 《Free radical research》1995,23(4):339-351
Reactive oxygen species (ROS) are involved in the mechanism of photoaging and carcinogenesis. Skin is endowed with antioxidant enzymes including superoxide dismutases (SOD): cytosolic copper zinc SOD and mitochondrial manganese SOD. The aim of our study was to estimate the protective effect of manganese against oxidative injury on cultured human skin fibroblasts. Dithranol, hydrogen peroxide and UV-A radiation (375 nm) were employed as oxidative stressors. The supply of manganese chloride produced an increase in cellular content of this element up to 24 fold without concomitant elevation of MnSOD activity. Nevertheless, manganese protects cells against two of the three ROS generating systems assessed, namely hydrogen peroxyde and UV-A. This protective effect depends on the concentration of manganese in the medium, 0.1 mM and 0.2 mM protect against UVA cytotoxicity, only 0.2 mM protects against H2O2 cytotoxicity. 相似文献
63.
Application of silica aerogel encapsulated lipases in the synthesis of biodiesel by transesterification reactions 总被引:1,自引:0,他引:1
Olivier Oraire Paulette Buisson Alain C. Pierre 《Journal of Molecular Catalysis .B, Enzymatic》2006,42(3-4):106-113
Two types of commercial lipases preparations, one from Burkholderia cepacia, the other one from Candida antartica, were encapsulated in silica aerogels reinforced with silica quartz fibre felt and dried by the CO2 supercritical technique. These immobilized biocatalysts were applied in biodiesel synthesis by transesterification of sunflower seed oil with methyl acetate. They were found to be efficient even with mixtures of both substrates without any solvent addition. The aerogel encapsulation technique made it possible to maintain the enzymes in a dispersion state similar to the dispersion prevailing in an aqueous solution, even for further use in organic hydrophobic media. In transesterification in excess iso-octane, the two lipases encapsulated in aerogels made from 40% MTMS, were found to have activities relatively close to each other and comparable with commercial Novozyme 435. On the other in transesterification with mixture of oil and methyl acetate without any solvent, the kinetics were severely limited by substrate diffusion inside the aerogels. This was particularly true with the C. antartica, so that the corresponding aerogel encapsulated enzyme was much less active than commercial Novozyme 435, although it improved after a few tests. 相似文献
64.
65.
Aline Frville Bndicte Gnangnon Annie Z. Tremp Caroline De Witte Katia Cailliau Alain Martoriati El Moukthar Aliouat Priyanka Fernandes Cerina Chhuon Olivier Silvie Sabrina Marion Ida Chiara Guerrera Johannes T. Dessens Christine Pierrot Jamal Khalife 《Open biology》2022,12(8)
Protein phosphatase 1 (PP1) is a key enzyme for Plasmodium development. However, the detailed mechanisms underlying its regulation remain to be deciphered. Here, we report the functional characterization of the Plasmodium berghei leucine-rich repeat protein 1 (PbLRR1), an orthologue of SDS22, one of the most ancient and conserved PP1 interactors. Our study shows that PbLRR1 is expressed during intra-erythrocytic development of the parasite, and up to the zygote stage in mosquitoes. PbLRR1 can be found in complex with PbPP1 in both asexual and sexual stages and inhibits its phosphatase activity. Genetic analysis demonstrates that PbLRR1 depletion adversely affects the development of oocysts. PbLRR1 interactome analysis associated with phospho-proteomics studies identifies several novel putative PbLRR1/PbPP1 partners. Some of these partners have previously been characterized as essential for the parasite sexual development. Interestingly, and for the first time, Inhibitor 3 (I3), a well-known and direct interactant of Plasmodium PP1, was found to be drastically hypophosphorylated in PbLRR1-depleted parasites. These data, along with the detection of I3 with PP1 in the LRR1 interactome, strongly suggest that the phosphorylation status of PbI3 is under the control of the PP1–LRR1 complex and could contribute (in)directly to oocyst development. This study provides new insights into previously unrecognized PbPP1 fine regulation of Plasmodium oocyst development through its interaction with PbLRR1. 相似文献
66.
Sabrina I?igo Astrid Nagels Durand Andrés Ritter Sabine Le Gall Martin Termathe Roland Klassen Takayuki Tohge Barbara De Coninck Jelle Van Leene Rebecca De Clercq Bruno P.A. Cammue Alisdair R. Fernie Kris Gevaert Geert De Jaeger Sebastian A. Leidel Raffael Schaffrath Mieke Van Lijsebettens Laurens Pauwels Alain Goossens 《Plant physiology》2016,172(2):858-873
67.
Thi Thuy Duong Michel Coste Agnès Feurtet-Mazel Dinh Kim Dang Caroline Gold Young Seuk Park Alain Boudou 《Hydrobiologia》2006,563(1):201-216
The effects of urban pollution from Hanoi city on the benthic diatom communities of the Nhue–Tolich river system were studied
during the 2003 dry season. Benthic diatoms were allowed to grow on glass slides suspended in the water flow for 4 weeks.
To reveal the relationship between water quality and diatom communities, Canonical correspondence analysis (CCA) was used
on data concerning relative abundances of diatom species and environmental variables. Two diatom indices, IPS and DAIpo, were
applied to evaluate water quality in the three rivers. A total of 291 diatom taxa were found in the Red, Nhue and Tolich Rivers.
These were mainly cosmopolitan taxa, with some tropical, subtropical and endemic taxa. The most abundant taxa at the Red site
were Aulacoseira granulata, Achnanthidium minutissimum, Encyonema minutum, Navicula recens and other halophilous taxa such as Nitzschia kurzii, Seminavis strigosa, Entomoneis paludosa, Bacillaria paradoxa. Diatom assemblages at the Tolich site consisted mainly of Nitzschia umbonata, Nitzschia palea and Eolimna minima. Diatom density ranged from 660 to 30,000 cells/cm2. Environmental variables and diatom assemblage composition at all sites were significantly correlated. Two diatom indices
gave similar results and indicate the Tolich River with the lowest values as a highly polluted site. 相似文献
68.
69.
Mauro C Vito P Mellone S Pacifico F Chariot A Formisano S Leonardi A 《Biochemical and biophysical research communications》2003,309(1):84-90
Nuclear factor kappaB (NF-kappaB) plays a pivotal role in numerous cellular processes, including stress response, inflammation, and protection from apoptosis. Therefore, the activity of NF-kappaB needs to be tightly regulated. We have previously identified a novel gene, named CIKS (connection to IkappaB-kinase and SAPK), able to bind the regulatory sub-unit NEMO/IKKgamma and to activate NF-kappaB. Here, we demonstrate that CIKS forms homo-oligomers, interacts with NEMO/IKKgamma, and is recruited to the IKK-complex upon cell stimulation. In addition, we identified the regions of CIKS responsible for these functions. We found that the ability of CIKS to oligomerize, and to be recruited to the IKK-complex is not sufficient to activate the NF-kappaB. In fact, a deletion mutant of CIKS able to oligomerize, to interact with NEMO/IKKgamma, and to be recruited to the IKK-complex does not activate NF-kappaB, suggesting that CIKS needs a second level of regulation to efficiently activate NF-kappaB. 相似文献
70.
Bettler E Imberty A Priem B Chazalet V Heyraud A Joziasse DH Geremia RA 《Biochemical and biophysical research communications》2003,302(3):620-624
The synthesis of sufficient amounts of oligosaccharides is the bottleneck for the study of their biological function and their possible use as drug. As an alternative for chemical synthesis, we propose to use Escherichia coli as a "living factory." We have addressed the production of the Galp alpha(1-3)Galp beta(1-4)GlcNAc epitope, the major porcine antigen responsible for xenograft rejection. An E. coli strain was generated which simultaneously expresses NodC (to provide the chitin-pentaose acceptor), beta(1-4) galactosyltransferase LgtB, and bovine alpha(1-3) galactosyltransferase GstA. This strain produced 0.68 g/L of the heptasaccharide Galp alpha(1-3)Galp beta(1-4)(GlcNAc)(5), which harbours the xenoantigen at its non-reducing end, establishing the feasibility of this approach. 相似文献