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961.
Jon Telling Ken Voglesonger Chelsea N. Sutcliffe Georges Lacrampe-Couloume Elizabeth Edwards Barbara Sherwood Lollar 《Geomicrobiology journal》2018,35(2):108-119
Precambrian Shield rocks host the oldest fracture fluids on Earth, with residence times up to a billion years or more. Water–rock reactions in these fracture systems over geological time have produced highly saline fluids, which can contain millimolar concentrations of H2. Mixing of these ancient Precambrian fluids with meteoric or palaeo-meteoric water can occur through tectonic fracturing, providing microbial inocula and redox couples to fuel blooms of subsurface growth. Here, we present geochemical and microbiological data from a series of borehole fluids of varying ionic strength (0.6–6.4 M) from the Thompson Mine (Manitoba) within the Canadian Precambrian Shield. Thermodynamic calculations demonstrate sufficient energy for H2-based catabolic reactions across the entire range of ionic strengths during mixing of high ionic strength fracture fluids with meteoric water, although microbial H2 consumption and cultivable H2-utilizing microbes were only detected in fluids of ≤1.9 M ionic strength. This pattern of microbial H2 utilization can be explained by the higher potential bioenergetic cost of organic osmolyte synthesis at increasing ionic strengths. We propose that further research into the bioenergetics of osmolyte regulation in halophiles is warranted to better constrain the habitability zones of hydrogenotrophic ecosystems in both terrestrial subsurface, including potential future radioactive waste disposal sites, and other planetary body crustal environments, including Mars. 相似文献
962.
Counsell Chelsie W. W. Donahue Megan J. Edwards Kyle F. Franklin Erik C. Hixon Mark A. 《Coral reefs (Online)》2018,37(3):827-840
Coral Reefs - Most of the diversity on coral reefs is in the cryptofauna, the hidden organisms that inhabit the interstitial spaces of corals and other habitat-forming benthos. However, little is... 相似文献
963.
Hindered transport of macromolecules in isolated glomeruli. II. Convection and pressure effects in basement membrane. 下载免费PDF全文
The filtration rates for water and a polydisperse mixture of Ficoll across films of isolated glomerular basement membrane (GBM) were measured to characterize convective transport across this part of the glomerular capillary wall. Glomeruli were isolated from rat kidneys and the cells were removed by detergent lysis, leaving a preparation containing almost pure GBM that could be consolidated into a layer at the base of a small ultrafiltration cell. A Ficoll mixture with Stokes-Einstein radii ranging from about 2.0 to 7.0 nm was labeled with fluorescein, providing a set of rigid, spherical test macromolecules with little molecular charge. Filtration experiments were performed at two physiologically relevant hydraulic pressure differences (delta P), 35 and 60 mmHg. The sieving coefficient (filtrate-to-retentate concentration ratio) for a given size of Ficoll tended to be larger at 35 than at 60 mmHg, the changes being greater for the smaller molecules. The Darcy permeability also varied inversely with pressure, averaging 1.48 +/- 0.10 nm2 at 35 mmHg and 0.82 +/- 0.07 nm2 at 60 mmHg. Both effects could be explained most simply by postulating that the intrinsic permeability properties of the GBM change in response to compression. The sieving data were consistent with linear declines in the hindrance factors for convection and diffusion with increasing pressure, and correlations were derived to relate those hindrance factors to molecular size and delta P. Comparisons with previous Ficoll sieving data for rats in vivo suggest that the GBM is less size-restrictive than the cell layers, but that its contribution to the overall size selectivity of the barrier is not negligible. Theoretical predictions of the Darcy permeability based on a model in which the GBM is a random fibrous network consisting of two populations of fibers were in excellent agreement with the present data and with ultrastructural observations in the literature. 相似文献
964.
H. Emilie Yen Dianzhong Zhang Jeng-Horng Lin Gerald E. Edwards Maurice S. B. Ku 《Physiologia plantarum》1997,101(3):526-532
The halophyte Mesembryanthemum crystallinum (ice plant) has been suggested as a model for salt-tolerance in higher plants. To investigate salt-induced changes in polypeptide patterns at the cellular level, a light-grown callus of M. crystallinum with substantial chlorophyll content, was established and the effect of NaCl on the composition of phenol-extracted protein was examined by SDS- and 2D-polyacrylamide gel electrophoresis (PAGE). SDS-PAGE showed the accumulation of five polypeptides with estimated molecular masses of 40, 34, 32, 29 and 14 kDa was enhanced by the addition of 200 m M NaCl to the culture media. The addition of ABA (10 μ M ) or mannitol (400 m M ) did not elicit the same degree of accumulation of these salt-specific proteins. These polypeptides were classified into two groups according to their course of induction: early responsive (40, 34, 29 kDa) and late-responsive (32, 14 kDa) proteins. In addition, two polypeptides (20, 18 kDa) were transiently accumulated during salt treatment. Further separation of soluble proteins by 2-D gel electrophoresis, either isoelectric focusing (IEF) or non-equilibrium pH-gradient electrophoresis (NEPHGE) followed by SDS-PAGE, showed more alterations in accumulation of polypeptides by NaCl than 1-D gel electrophoresis. Overall, levels of more than 30% of basic polypeptides, detected by NEPHGE/SDS-PAGE, were altered by 200 m M NaCl treatment, while only 10% of neutral and acidic polypeptides, detected by IEF/SDS-PAGE, were changed. The enhanced expression of these proteins by salt in cultured cells is most likely related to the cellular responses to salinity, and not to the mechanism of CAM induction in this facultative halophyte. 相似文献
965.
Reproducibility testing of RAPD,AFLP and SSR markers in plants by a network of European laboratories 总被引:21,自引:0,他引:21
Jones C.J. Edwards K.J. Castaglione S. Winfield M.O. Sala F. van de Wiel C. Bredemeijer G. Vosman B. Matthes M. Daly A. Brettschneider R. Bettini P. Buiatti M. Maestri E. Malcevschi A. Marmiroli N. Aert R. Volckaert G. Rueda J. Linacero R. Vazquez A. Karp A. 《Molecular breeding : new strategies in plant improvement》1997,3(5):381-390
A number of PCR-based techniques can be used to detect polymorphisms in plants. For their wide-scale usage in germplasm characterisation and breeding it is important that these marker technologies can be exchanged between laboratories, which in turn requires that they can be standardised to yield reproducible results, so that direct collation and comparison of the data are possible. This article describes a network experiment involving several European laboratories, in which the reproducibility of three popular molecular marker techniques was examined: random-amplified fragment length polymorphism (RAPD), amplified fragment length polymorphism (AFLP) and sequence-tagged microsatellites (SSR). For each technique, an optimal system was chosen, which had been standardised and routinely used by one laboratory. This system (genetic screening package) was distributed to different participating laboratories in the network and the results obtained compared with those of the original sender. Different experiences were gained in this exchange experiment with the different techniques. RAPDs proved difficult to reproduce. For AFLPs, a single-band difference was observed in one track, whilst SSR alleles were amplified by all laboratories, but small differences in their sizing were obtained. 相似文献
966.
Detection, distribution and probable fate of Escherichia coli O157 from asymptomatic cattle on a dairy farm 总被引:2,自引:1,他引:1
J. Porter K. Mobbs C.A. Hart J.R. Saunders R.W. Pickup & C. Edwards 《Journal of applied microbiology》1997,83(3):297-306
The use of commercial anti- Escherichia coli O157-labelled magnetic beads was investigated to improve detection of E. coli O157 by immunomagnetic separation (IMS) from a range of environments on a dairy farm. Immunomagnetic separation proved effective for separation of target cells from laboratory mixtures and during stress in sterile and non-sterile pond water. The IMS procedure was possible with a range of samples (water, faeces, slurry, grass and soil). Non-specific binding of non-target bacterial cells proved problematic in a number of sample types. However, indigenous E. coli O157 cells were detected from samples with a high faecal load, and only with use of IMS. Data on the probable survival and spread of the organism around the farm environment are also discussed. 相似文献
967.
S H Battah C E Chee H Nakanishi S Gerscher A J MacRobert C Edwards 《Bioconjugate chemistry》2001,12(6):980-988
Using a convergent growth approach, a series of novel 5-aminolevulinic acid (ALA)-containing dendrimers have been synthesized. In these molecules, ALA residues are attached to the periphery by ester linkages, with amide bonds connecting the dendrons. Three first-generation dendrimers, bearing either 6 or 9 ALA residues, were synthesized by attachment of a tris(Boc-protected ALA)-containing wedge (1) to a di- or tripodent aromatic, or tripodent aliphatic core. Two second generation 18-ALA-containing dendrimers were also synthesized using a 3,3'-iminodipropionic acid spacer unit between wedge 1 and the aromatic core. These compounds differed only in the distance between the core and the linker unit. The Boc-protected dendrimers were deprotected using trifluoroacetic acid and isolated as their TFA salts. The potential of these ALA ester dendrimers as macromolecular prodrugs for photodynamic therapy has been demonstrated in the tumorigenic keratinocyte PAM 212 cell line. 相似文献
968.
AIMS: To measure the concentration of mRNAs transcribed from four genes involved in alginate production using real-time PCR. METHODS AND RESULTS: The mRNA concentrations in cells grown in normal and stress conditions were compared. A difference in the expression of algD, the key gene leading to overproduction of alginate, was detected between alginate-producing and non-alginate-producing strains grown under normal conditions. After growth on 3% ethanol (known to stimulate alginate production), but not after heat-shock, an increase in algD mRNA levels and a corresponding decrease in mucB (a regulatory gene) mRNA levels were detected in all strains. CONCLUSION: The quantitative results suggest that the mucB gene may have a role in recognition of stress conditions, and that having a disrupted mucA gene does not always result in a mucoid phenotype. SIGNIFICANCE AND IMPACT OF THE STUDY: Real-time PCR can be used to quantify mRNA and is a convenient method of analysing bacterial gene expression. 相似文献
969.
Tritrichomonas foetus was shown to undergo a regulatory volume increase (RVI) when it was subjected to hyperosmotic challenge, but there was no regulatory volume decrease after hypoosmotic challenge, as determined by using both light-scattering methods and measurement of intracellular water space to monitor cell volume. An investigation of T. foetus intracellular amino acids revealed a pool size (65 mM) that was similar to that of Trichomonas vaginalis but was considerably smaller than those of Giardia intestinalis and Crithidia luciliae. Changes in amino acid concentrations in response to hyperosmotic challenge were found to account for only 18% of the T. foetus RVI. The T. foetus intracellular sodium and potassium concentrations were determined to be 35 and 119 mM, respectively. The intracellular K+ concentration was found to increase considerably during exposure to hyperosmotic stress, and, assuming that there was a monovalent accompanying anion, this increase was estimated to account for 87% of the RVI. By using light scattering it was determined that the T. foetus RVI was enhanced by elevated external K+ concentrations and was inhibited when K+ and/or Cl− was absent from the medium. The results suggested that the well-documented Na+-K+-2Cl− cotransport system was responsible for the K+ influx activated during the RVI. However, inhibitors of Na+-K+-2Cl− cotransport in other systems, such as quinine, ouabain, furosemide, and bumetanide, had no effect on the RVI or K+ influx in T. foetus. 相似文献
970.
Laboratory culture studies on the euryhalinity of Bostrychia radicans Montagne and Caloglossa leprieurii (Montagne) J. Agardh from the mouth and head of the Mullica River estuary, New Jersey, revealed both species probably have ecotypes whose growth patterns correlate with the salinity regime of their habitat in nature. Significant growth differences of tetrasporelings were determined in response to four salinities (5, 15, 25, 35%c) even after acclimation periods of the tetrasporophytes from 6 mo–2 yr in laboratory culture. However, one isolate of Bostrychia and both isolates of Caloglossa also demonstrated some capability for physiological adaptation to salinity changes although this was less significant statistically than their ecotypic response. It thus appears that certain euryhaline algae may consist of ecotypes, each of which has some capacity for physiological adaptation to salinity variations. 相似文献