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101.
Mycotoxins, toxic secondary metabolites of fungi are now recognised as major cause of food intoxications in Sub Saharan Africa
(SSA). Aflatoxins, the most important of the group have been implicated in acute aflatoxicoses, carcinogenicity, growth retardation,
neonatal jaundice and immunological suppression in SSA. The hot and humid tropical climate provides ideal condition for growth
of toxigenicAspergillus spp, making food contamination to be widespread in SSA, with maize and groundnuts being the most contaminated. The available
data suggests that cassava products (the most important African food) are not prone to aflatoxin contamination. Recent data
on ochratoxin A produced by species ofAspergillus on grains have indicated the necessity for it to be monitored in SSA. Fumonisins represent the most importantFusarium mycotoxins in SSA, and surveillance data indicate very high contamination rates of almost 100% in maize samples from West
Africa. Limited information exists on the occurrence of trichothecenes, while the data currently available suggest that zearalenone
contamination seems not to be a problem in SSA. The strategies under investigation to mitigate the mycotoxin problem in SSA
include education of the people on the danger of consuming mouldy foods, pre and post harvest management strategies with emphasis
on biological control, use of plant products to arrest fungal growth during storage, enterosorbent clay technology, and the
search for traditional techniques that could reduce/detoxify mycotoxins during food processing. 相似文献
102.
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105.
Gyrgy Vereb Lszl Mtyus Lszl Bene Gyrgy Panyi Zsolt Bacs Margit Balzs Jnos Matk Jnos Szllsi Rezs Gspr Sndor Damjanovich Robert E. Dale Carlo Pieri Marcel Ameloot 《Journal of molecular recognition : JMR》1995,8(4):237-246
Molecular recognition processes between cell surface elements are discussed with special reference to cell surface pattern formation of membrane-bound integral proteins. The existence, as detected by flow cytometric resonance energy transfer (Appendix), and significance of cell surface patterns involving the interleukin-2 receptor, the T-cell receptor–CD3 system, the intercellular adhesion molecule ICAM-1, and the major histocompatilibilty complex class I and II molecules in the plasma membrane of lymphocytes are described. The modulation of antigen presentation by transmembrane potential changes is discussed, and a general role of transmembrane potential changes, and therefore of icon channel activities, adduced as one of the major regulatory mechanisms of cell–cell communications. A general role in the mediation and regulation of intercellular interactions is suggested for cell-surface macromolecular patterns. The dynamic pattern of protein and lipid molecules in the plasma membrane is generated by the genetic code, but has a remarkable flexibility and may be one of the major instruments of accomodation and recognition processes at the cellular level. 相似文献
106.
Georg J. Seifert Peter Kanzler Artur da Câmara Machado Hermann Katinger Margit Laimer da Câmara Machado 《Plant cell reports》1995,14(11):679-683
To establish a protocol suited for the molecular characterization of root induction the influences of explant position, etiolation state and orientation as well as temperature and light intensity on root and callus formation were investigated. Depending on these factors stem discs of Malus incubated on indole-3-butyric acid containing medium and subsequently on hormone-free medium regenerated roots and callus of filamentous and smooth texture to a varying extent. Concentration and incubation duration of indole-3butyric acid strongly affected rooting and the production of smooth callus. Moreover smooth callus was profuse at the low light levels applied during rooting. Rooting efficiency decreased and filamentous callus increased between 19°C and 25°C. Explants close to the shoot apex displayed reduced rooting efficiency and profuse filamentous callus. There was a strong effect of explant orientation on root and filamentous callus formation.Abbrevations IBA
indole-3-butyric acid
- IAA
indole-3-acetic acid
- BA
6-benzylaminopurine
- MS
Murashigeand Skoog
- rts
roots
- rt
rooted
- rtd
rooted discs 相似文献
107.
Karl-Heinz Wrobel Daniela Bickel Richard Kujat Margit Schimmel 《Cell and tissue research》1995,279(2):249-259
We have used a cytochemical technique to investigate the distribution of acetylcholinesterase (AChE) activity in the deutocerebrum of the brain of the sphinx moth Manduca sexta. To distinguish between extra-and intracellular pools of the enzyme, some brains were treated prior to histochemical staining with echothiophate, an irreversible AChE inhibitor which penetrates cell membranes very slowly and, therefore, inhibits only extracellular AChE. In the antennal nerve, fascicles of presumably mechanosensory fibers show echothiophateinsensitive AChE activity. They bypass the antennal lobe and project to the antennal mechanosensory and motor center of the deutocerebrum. In the antennal lobe, fibers in the coarse neuropil, cell bodies in the lateral cell group, and all glomeruli exhibit AChE activity. In most ordinary glomeruli, echothiophate-sensitive AChE activity is concentrated in the outer cap regions, corresponding to the terminal arborizations of olfactory afferents. A previously unrecognized glomerulus in the ventro-median antennal lobe shows uniform and more intense AChE-specific staining that the other glomeruli. No AChE activity appeared to be associated with malespecific pheromone-sensitive afferents in the macro-glomerular complex. About 67 interneurons with somata in the lateral cell group of the antennal lobe show echo-thiophate-insensitive AChE activity. These neurous seem to be members of two types of antennal-lobe projection neurons with fibers passing through the outer-antenno-cerebral tract to the protocerebrum. AChE-stained arborizations of these neurons appear to invade all glomeruli, including three distinguishable subunits of the male-specific macroglomerular complex. In echothiophate-treated animals, the projections of one of these types of fiber form large terminals in the lateral horn of protocerebrum, which partly protrude into the adjacent glial cell layer. The results suggest that extracellularly accessible AChE is associated with ordinary olfactory receptor terminals but apparently not with pheromone-sensitive afferents. Intracellular AChE appears to be present in antennal mechanosensory fibers and in two types of olfactory projection neurons of the antennal lobe. The study provides further evidence for cholinergic neurotransmission of most antennal afferents. The AChE-containing interneurons might be cholinergic as well or use the enzyme for functions unrelated to hydrolysis of acetylcholine.Abbreviations
ACh
acetylcholine
-
AChE
acetylcholinesterase
-
AL
antennal lobe
-
AMMC
antennal mechanosensory and motor center
-
ChAT
choline acetyltransferase
-
IACT
inner antenno-cerebral tract
-
MGC
macroglomerular complex 相似文献
108.
Frischmuth Thomas Engel Margit Jeske Holger 《Molecular breeding : new strategies in plant improvement》1997,3(3):213-217
Beet curly top virus (BCTV) infection is associated with the de novo synthesis of a heterogeneous population of subgenomic viral DNAs. Nicotiana benthamiana plants transformed with a partial repeat of one such subgenomic DNA remained susceptible to infection but produced ameliorated symptoms when agroinoculated with BCTV. Symptom amelioration is associated with the mobilization of subgenomic DNA from the integrated copy. In an attempt to improve the resistance, N. benthamiana has been transformed with a partial repeat of a much smaller subgenomic DNA. However, transgenic plants showed almost no resistance although subgenomic DNA was mobilised from the host genome. To further understand the molecular basis of the interference phenomenon, we compared the ability of BCTV to replicate and accumulate in leaf discs derived from resistant and non-resistant transgenic plants. Both subgenomic DNAs were able to interfere with virus replication but only in case of resistant plants the DI DNA efficiently suppressed viral accumulation. 相似文献
109.
Fine Genetic Map of Mouse Chromosome 10 around the Polycystic Kidney Disease Gene,jcpk,and Ankyrin 3
Elizabeth C. Bryda Helen Ling Donald E. Rathbun Margit Burmeister Lorraine Flaherty 《Genomics》1996,35(3):425
A chlorambucil (CHL)-induced mutation of thejcpk(juvenile congenital polycystic kidney disease) gene causes a severe early onset polycystic kidney disease. In an intercross involvingMus musculus castaneus, jcpkwas precisely mapped 0.2 cM distal toD10Mit115and 0.8 cM proximal toD10Mit173.In addition, five genes,Cdc2a, Col6a1, Col6a2, Bcr,andAnk3were mapped in both thisjcpkintercross and a (BALB/c × CAST/Ei)F1× BALB/c backcross. All five genes were eliminated as possible candidates forjcpkbased on the mapping data. Thejcpkintercross allowed the orientation of theAnk3gene relative to the centromere to be determined.D10Mit115, D10Mit173, D10Mit199,andD10Mit200were separated genetically in this cross. The order and genetic distances of all markers and gene loci mapped in thejcpkintercross were consistent with those derived from the BALB/c backcross, indicating that the CHL-induced lesion has not generated any gross chromosomal abnormalities detectable in these studies. 相似文献
110.
System to study horizontal gene exchange among microorganisms without cultivation of recipients 总被引:9,自引:0,他引:9
Ribosomal RNA genes are characterized by highly conserved sequences and are present in multiple copies in most prokaryotic chromosomes. In principle, therefore, they might serve as sites for homologous recombination between unrelated microorganisms. Plasmids containing 23S ribosomal gene sequences, from different bacteria, which had been interrupted by insertion of a kanamycin-resistance gene, were used to transform Acinetobacter sp. DSM587 (former name: Acinetobacter calcoaceticus BD413-ivl10). In all cases, homologies between the 23S rRNA genes of phylogenetically distant bacteria and Acinetobac-ter sp. DSM587 were sufficient for replacement recombination events. The integration events, resulting in inactivation of any one of the seven rrn operons of Acinetobacter sp. DSM587, had no observable influence on cell growth. These results suggest the possibility of rRNA genes serving as natural vehicles for horizontal gene transfer. They also provide the basis of a novel strategy to analyse gene transfer without selection or cultivation of recipient cells. Because of the highly conserved structure of bacterial rrn operons, recombination events subsequent to gene transfer can be readily identified by polymerase chain reaction amplification of the recombinant sequence using a universal forward primer for the 16S rRNA gene and a reverse primer specific for the integrated marker gene. 相似文献