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1.
Antoine Sioufi Françoise Pommier 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1980,181(2):161-168
A method for the determination of benzoic acid down to concentrations of 10 ng/ml in plasma or urine is described. After addition of an internal standard, benzoic acid is extracted at acid pH into diethyl ether. Both compounds are derivatized with pentafluorobenzyl bromide. The derivatives are determined by gas chromatography using a 43Ni electron-capture detector. Hippuric acid is hydrolysed in plasma and urine and total benzoic acid is determined by the same technique. 相似文献
2.
Summary A DNA fragment containing the cya gene region of Erwinia chrysanthemi, B374 was cloned in vivo and transferred into cells of E. coli using a plasmid pULB113 derived from RP4 followed by subcloning in vitro into the vector pBR322. The cya gene encodes a 95 kDal protein that complemented E. coli cya mutants. Apparently, cya genes truncated at the 3 end could still produce proteins complementing cya-defective strains, thus showing that adenylate cyclase truncated at its carboxy-terminal end could synthesise cAMP. A protein of unknown function (40 kDal) is encoded by a gene that is transcribed divergently from the control region of the adenylate cyclase gene. 相似文献
3.
Summary A method based on BrdU incorporation for analyzing in detail the kinetics of the cell cycle is described. The S phase has been subdivided into five subphases, each recognizable by their BrdU incorporation pattern at metaphase. The method can be useful for the study of abnormal cell cycles, and may have particular application in mutagenesis studies concerning the various subphases of the S phase, without using synchronization techniques. An application of the method is described, showing that -irradiation, during the course of the S phase, leads to a lack of cells which were in early S phase at the time of irradiation. This finding can be related either to a higher lethality at this stage of the cell cycle or to a delay in completion of DNA replication after irradiation.Hoider of a C.E.C. scholarship 相似文献
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5.
Forage abundance, forage quality, and social factors are key elements of the foraging ecology of wild herbivores. For non-ruminant
equids, forage-limited environments are likely to impose severe constraints on their foraging behaviour. We used a multi-scale
approach to study foraging behaviour in kiang (Equus kiang), a wild equid inhabiting the high-altitude rangelands of the Tibetan Plateau. Using behavioural observations and vegetation
sampling, we first assessed how patterns of plant abundance and quality affected (i) the instantaneous forage intake rate
(fine scale) and (ii) the proportion of time spent foraging (coarse scale) across seasons. We also tested whether foraging
behaviour differed among group types, between sex in adults, and between females of different reproductive status. At a fine
scale, intake rate increased linearly with bite size and increased following a type II curvilinear function with biomass on
feeding sites. Forage intake rate also increased linearly with plant quality. Male and female kiangs had similar intake rates.
Likewise, gravid and lactating females had similar intake rates as barren and non-lactating females. At a coarse scale, kiangs
spent longer time feeding in mesic than in xeric habitats, and spent more time feeding in early summer and fall than in late
summer. Groups of adults with foals spent less time feeding than male groups and groups of adults without foals. Our findings
suggest that kiangs use flexible foraging behaviours in relation to seasonal variations of vegetation quality and abundance,
a likely outcome of the extreme seasonal conditions encountered on the Tibetan Plateau. 相似文献
6.
7.
Caspase-1 activation by Salmonella 总被引:7,自引:0,他引:7
Salmonella is an interesting example of how the selective pressure of host environments has led to the evolution of sophisticated bacterial virulence mechanisms. This microbe exploits the first-line of defence, the macrophage, as a crucial tool in the initiation of disease. After invasion of intestinal macrophages, a virulence protein secreted by Salmonella specifically induces apoptotic cell death by activating the cysteine protease caspase-1. The pro-apoptotic capability is necessary for successful pathogenesis. The study of mechanisms by which Salmonella induces programmed cell death offers new insights into how pathogens cause disease and into general mechanisms of activation of the innate immune system. 相似文献
8.
Giraud A Arous S De Paepe M Gaboriau-Routhiau V Bambou JC Rakotobe S Lindner AB Taddei F Cerf-Bensussan N 《PLoS genetics》2008,4(1):e2
While pleiotropic adaptive mutations are thought to be central for evolution, little is known on the downstream molecular effects allowing adaptation to complex ecologically relevant environments. Here we show that Escherichia coli MG1655 adapts rapidly to the intestine of germ-free mice by single point mutations in EnvZ/OmpR two-component signal transduction system, which controls more than 100 genes. The selective advantage conferred by the mutations that modulate EnvZ/OmpR activities was the result of their independent and additive effects on flagellin expression and permeability. These results obtained in vivo thus suggest that global regulators may have evolved to coordinate activities that need to be fine-tuned simultaneously during adaptation to complex environments and that mutations in such regulators permit adjustment of the boundaries of physiological adaptation when switching between two very distinct environments. 相似文献
9.
New virulence-activated and virulence-repressed genes identified by systematic gene inactivation and generation of transcriptional fusions in Bordetella pertussis 下载免费PDF全文
Antoine R Alonso S Raze D Coutte L Lesjean S Willery E Locht C Jacob-Dubuisson F 《Journal of bacteriology》2000,182(20):5902-5905
10.
Thermocouple arrays were deployed on two deep-sea hydrothermal vents at Guaymas Basin (27 degrees 0.5'N, 111 degrees 24.5'W) in order to measure in situ temperatures at which microorganisms colonize the associated mineral deposits. Intact sections of three structures that formed around the arrays were collected after 4 and 72 day deployments (named BM4, BM72 and TS72). Archaeal diversity associated with discreet subsamples collected across each deposit was determined by polymerase chain reaction amplification of 16S rRNA genes. Spatial differences in archaeal diversity were observed in all deposits and appeared related to in situ temperature. In BM4, no 16S rRNA genes were detected beyond about 1.5 cm within the sample (> 200 degrees C). Phylotypes detected on the outside of this deposit belong to taxonomic groups containing mesophiles and (hyper)thermophiles, whereas only putative hyperthermophiles were detected 1.5 cm inside the structure (approximately 110 degrees C). In contrast, the more moderate thermal gradient recorded across TS72 was associated with a deeper colonization (2-3 cm inside the deposit) of putative hyperthermophilic phylotypes. Although our study does not provide a precise assessment of the highest temperature for the existence of microbial habitats inside the deposits, archaeal 16S rRNA genes were detected directly next to thermocouples that measured 110 degrees C (Methanocaldococcus spp. in BM4) and 116 degrees C (Desulfurococcaceae in TS72). The successive array deployments conducted at the Broken Mushroom (BM) site also revealed compositional differences in archaeal communities associated with immature (BM4) and mature chimneys (BM72) formed by the same fluids. These differences suggest a temporal transition in the primary carbon sources used by the archaeal communities, with potential CO(2)/H(2) methanogens prevalent in BM4 being replaced by possible methylotroph or acetoclastic methanogens and heterotrophs in BM72. This study is the first direct assessment of in situ conditions experienced by microorganisms inhabiting actively forming hydrothermal deposits at different stages of structure development. 相似文献