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991.
P. Berrebi M. M. Kraiem † I. Doadrio ‡ S. El Gharbi § G. Cattaneo-Berrebi 《Journal of fish biology》1995,47(5):850-864
Enzyme electrophoresis on horizontal starch gel was carried out on 356 barbel individuals. The sampling comprised 278 individuals of the species Barbus callensis from 10 rivers in Tunisia. The other individuals belonged to reference species (outgroups) from France and Morocco. An ecological study was also carried out on Tunisian rivers. The results show a clear differentiation of the two samples from northwestern Tunisia, which was only partly correlated with ecological characteristics of the rivers they inhabit. There is no genetic cline, but rather a discontinuity between populations in the northwestern-most watershed and all the other Tunisian populations. This differentiation probably has a paleohistoric origin not only related to adaptation to ecological conditions but also to difficulties in colonizing the watersheds. The results do not indicate clearly a colonization direction for the genus Barbus in North Africa. Analysis of the Algerian populations would appear to be indispensable. Lastly, in contrast with the usual taxonomy, Morocco and Tunisia are populated by two closely related species, but B. callensis should remain the name of the Tunisian species, which was the first to be described in the small El Kebir basin, a river that flows from Tunisia to Algeria. 相似文献
992.
993.
The plasmid plP1066, harboured by a methicillin-resistant Staphylococcus aureus strain isolated in France, carries genes specifying β-lactamase. This plasmid undergoes numerous rearrangements. One of these was an insertion, between the genes binR and sin encoding resolvases, of a 16 kb element which displayed the characteristic features of a transposon. This putative transposon, named Tn 5404 , carried genes encoding proteins involved in its transposition, as well as a resolution system, which were indistinguishable from those of the S. aureus transposon Tn 552 . These were: p480 encoding a probable transposase, p271 encoding a putative ATP-binding protein, binL encoding a resolvase, and a resolution site, resL . In addition, Tn 5404 carried aminoglycoside-resistance genes ( aphA, str ) and the insertion sequence IS 1181 . Tn 5404 contained at its termini 116 bp imperfect inverted repeats, similar to those of Tn 552 , and was flanked by 6 bp direct repeats. Insertion of Tn 5404 close to resR and to the structural and regulatory β-lactamase genes ( blaZ, blal, blaR1 ) of plP1066, generated a 3.5 kb invertible segment flanked by inversely repeated resolution sites ( resR, resL ). This invertible segment, which carried p480 , p271 and binL , generated Tn 552 or Tn 5404 , depending on its orientation. Thus, these two transposons share their transposition and resolution systems. 相似文献
994.
Kidney medulla cells of mammals have to cope with large changes in environmental osmolarity, a challenge most other mammalian cells never have to experience. In these last cells, application of osmotic shocks induces dramatic modifications in chromatin organization. The present paper reports on the changes of medulla cell chromatin in situ, in rat kidney slices submitted to osmotic challenges and in vitro, on preparations of extracted chromatin submitted to changes in environmental ion concentrations. Our results show that the chromatin of kidney medulla cells: (1) does not behave differently from the other mammalian chromatins when submitted in situ or in vitro to osmotic challenges; (2) presents in vitro physico-chemical characteristics similar to those of the other mammalian chromatins; and (3) is protected in vitro, as the other mammalian chromatins, from the disrupting effects of increases in inorganic ion concentrations by different compensatory organic solutes. The ability of kidney medulla cells to adapt to large increases in osmolarity could thus be related to a rapid control of the level of such compounds rather than to some rather specific, intrinsic molecular adaptations of macromolecules. 相似文献
995.
The building up of the two types of reaction centers, PS II and PS II, was investigated during the greening of Euglena gracilis Z cells in resting medium. The maximal values in the proportion of PS II centers (55%) and in the oxygen evolved per chlorophyll were reached at the outbreak of greening, when accumulation of galactolipids (MGDG and DGDG) rich in unsaturated fatty acids occurred, and when anionic lipids (SQDG and PG) emerged. As the greening progressed, the chlorophyll accumulation corresponded to a secondary enrichment in PS II centers, which built up more rapidly than PS II centers; correlatively, a general saturation of the fatty acids constitutive of all lipid classes took place.Abbreviations DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea
- DGDG
digalactosyldiacylglycerol
- FAME
Tatty acid methyl esters
- HEPES
acide (N-[2-hydroxyethyl]piperazine-N-[2-ethane sulfonic]
- MGDG
monogalactosyldiacylglycerol
- PC
phosphatidylcholine
- PE
phosphatidylethanolamine
- PG
phosphatidylglycerol
- PQ
plastoquinone
- PS I
Photosystem I
- PS II
Photosystem II
- QA
primary quinone electron acceptor of PS II
- QB
secondary quinone electron acceptor of PS II
- SQDG
sulfoquinovosyldiacylglycerol 相似文献
996.
Accumulation of cadmium, lead and strontium, and a role of calcium oxalate in water hyacinth tolerance 总被引:2,自引:0,他引:2
Eichhornia crassipes plants brought from the River Nile were cultured in jars containing river water supplemented with various
concentrations of Cd, Pb, and Sr (0 to 100 μg cm-3), added simultaneously. Treatment continued for 20 d during which each
cultivation solution was being replaced with fresh one every 3 d. The growth of Eichhornia was drastically retarded at heavy
metal concentrations higher than 15 μg cm-3. At concentrations 15 or 25 μg cm-3, the accumulation of Cd and Pb to levels several
times higher than those in control plants was found. More than 50 % of the uptaken metals were retained by roots alone. Leaves
and leaf petiols received around 30 and 20 % of the accumulated metals, respectively. X-ray microanalysis indicated the presence
of the three heavy metals in Ca oxalate crystals. Content of metals in the crystals increased progressively over time of exposure
in a way similar to those in whole plant tissues. These results suggest a possible role for Ca oxalate crystalization in toxic
heavy metal deposition and thus tolerance by Eichhornia.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
997.
N Srairi-Abid P Mansuelle T Mejri H Karoui H Rochat F Sampieri M El Ayeb 《European journal of biochemistry》2000,267(17):5614-5620
Two toxin-like proteins (AahTL1 and AahTL3) were purified from the venom of the scorpion Androctonus australis Hector (Aah). AahTL1 and AahTL3 are the first non toxic proteins cross-reacting with AahI toxins group which indicates that these proteins can be used as a model of vaccins. In order to study structure-function relationships, their complete amino-acid sequences (66 residues) were determined, by automated Edman degradation. They show more than 50% of similarity with both AahI and AahIII antimammal toxins. Three-dimensional structural models of AahTL1 and AahTL3 constructed by homology suggest that the two proteins are structurally similar to antimammal scorpion alpha-toxins specific to voltage dependent Na+ channels. The models showed also that amino-acid changes between potent Aah toxins and both AahTL1 and AahTL3 disrupt the electrostatic potential gradient at their surface preventing their interaction with the receptor, which may explain their non toxicity. 相似文献
998.
The invasive brown seaweed Sargassum muticum as new resource for alginate in Morocco: Spectroscopic and rheological characterization 下载免费PDF全文
Samir El Atouani Fouad Bentiss Abdeltif Reani Rachid Zrid Zahira Belattmania Leonel Pereira Abdelhadi Mortadi Omar Cherkaoui Brahim Sabour 《Phycological Research》2016,64(3):185-193
The Japanese brown seaweed Sargassum muticum, recently invaded several shorelines worldwide including the Atlantic coast of Morocco with large well‐established populations. Within the framework of a sustainable strategy to control this invasive seaweed, we report on extraction yield, spectroscopic characterization and rheological properties of alginate, a commercially valuable colloid, from harvested biomass of S. muticum. Extraction yield was about 25.6% on dry weight basis. Infrared spectroscopy analysis shows that the obtained Fourier transform infrared spectra of the extracted biopolymer exhibit strong similarities with that of the commercial alginate. Furthermore, Proton nuclear magnetic resonance spectroscopy revealed that S. muticum alginate has almost equal amounts of β‐D‐mannuronic acid (M; 49%) and α‐L‐guluronic acid (G; 51%) with an M/G ratio of 1.04 and a high content of heteropolymeric MG GM diads suggesting a sequence distribution of an alternated polymer type. Rheological measurements were performed at different sodium alginate concentrations, temperatures and shear rates. The hydrocolloid exhibited pseudoplastic behavior and showed shear thinning, particularly at high solution concentration and low temperature which is consistent with the rheological behavior reported for commercial alginates. Considering the abundance of S. muticum in the Northwestern Atlantic coast of Morocco and the quality of the extracted hydrogel, this invasive species could be considered as a potential source of alginates. 相似文献
999.
1000.
Current concepts concerning the social behavior of microorganisms inhabiting the human gastrointestinal (GI) tract and their role in the formation of integrated supracellular structures and in intercellular communication in the host–microbiota system are reviewed. The analysis of the literature data and of the results obtained by the authors indicates an important role of neuromediators (biogenic amines, amino acids, peptides, and nitric oxide) in intra- and interspecies microbial communication, as well as in the microbiota–host dialogue. The role of this dialogue for human health, its effect on the human psyche and social behavior, and the possibility of construction of probiotic preparations with a target-oriented neurochemical effect are discussed. 相似文献