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171.
Hugh A. L. Henry Mehdi Abedi Concepción L. Alados Karen H. Beard Lauchlan H. Fraser Anke Jentsch Juergen Kreyling Andrew Kulmatiski Eric G. Lamb Wei Sun Mathew R. Vankoughnett Susanna Venn Christiane Werner Ilka Beil Irmgard Blindow Sven Dahlke Maren Dubbert Alexandra Effinger Heath W. Garris Maite Gartzia Tobias Gebauer Mohammed A. S. Arfin Khan Andrey V. Malyshev John Morgan Charles Nock Janelle P. Paulson Yolanda Pueyo Holly J. Stover Xuechen Yang 《Ecosystems》2018,21(7):1432-1444
Reduced precipitation treatments often are used in field experiments to explore the effects of drought on plant productivity and species composition. However, in seasonally snow-covered regions reduced precipitation also reduces snow cover, which can increase soil frost depth, decrease minimum soil temperatures and increase soil freeze–thaw cycles. Therefore, in addition to the effects of reduced precipitation on plants via drought, freezing damage to overwintering plant tissues at or below the soil surface could further affect plant productivity and relative species abundances during the growing season. We examined the effects of both reduced rainfall (via rain-out shelters) and reduced snow cover (via snow removal) at 13 sites globally (primarily grasslands) within the framework of the International Drought Experiment, a coordinated distributed experiment. Plant cover was estimated at the species level, and aboveground biomass was quantified at the functional group level. Among sites, we observed a negative correlation between the snow removal effect on minimum soil temperature and plant biomass production the next growing season. Three sites exhibited significant rain-out shelter effects on plant productivity, but there was no correlation among sites between the rain-out shelter effect on minimum soil moisture and plant biomass. There was no interaction between snow removal and rain-out shelters for plant biomass, although these two factors only exhibited significant effects simultaneously for a single site. Overall, our results reveal that reduced snowfall, when it decreases minimum soil temperatures, can be an important component of the total effect of reduced precipitation on plant productivity. 相似文献
172.
Fe(III) as an electron acceptor for H2 oxidation in thermophilic anaerobic enrichment cultures from geothermal areas 总被引:1,自引:0,他引:1
Alexander I. Slobodkin Juergen Wiegel 《Extremophiles : life under extreme conditions》1997,1(2):106-109
Six sustainable enrichment cultures of thermophilic H2-oxidizing microorganisms utilizing Fe(III) as an electron acceptor were obtained from geothermally heated environments located
on two continents (America, Eurasia) and on islands in the Northern (Iceland) and Southern (Fiji) hemispheres, demonstrating
the wide distribution of these microorganisms. The main products of amorphic Fe(III) oxide reduction were magnetite and siderite.
The observed temperature range for Fe(III) reduction in growing cultures was from 55°C to 87°C, extending the known limits
for growth of Fe(III)-reducing microorganisms producing extracellular magnetite to nearly 90°C.
Received: August 13, 1996 / Accepted: January 17, 1997 相似文献
173.
Thomas A. Kuemmel Juergen Thiele Achim H. Blaeser Claudia Wickenhauser Stephan E. Baldus Robert Fischer 《Journal of molecular histology》1997,29(9):695-705
This study was performed to obtain a better insight into the glycosylation pattern of human CD34+ haematopoietic stem
cells and lymphocytes from peripheral blood using an ultrastructural post-embedding technique. Lectins applied were
derived from Canavalia ensiformis (Con A), Triticum vulgare (WGA), Lycopersicon esculentum (LEA), Limulus polyphemus
(LPA), Ulex europaeus-I (UEA-I), Bauhinia purpurea (BPA), Glycine max (SBA), Helix pomatia (HPA), Arachis hypogaea (PNA)
and Erythrina cristagalli (ECA). Our results showed almost identical staining patterns with both CD34+ cells and mature
lymphocytes from peripheral blood. Con A displayed a prominent reactivity with the nuclear envelope and a weak
staining of the plasma membrane. As demonstrated by an elaborate lectin double-labelling technique, WGA revealed an
opposite staining pattern. Following neuraminidase treatment of sections, BPA, PNA and SBA exhibited a prominent
staining of the plasma membrane in CD34+ cells and lymphocytes as well. Membrane reactivity with HPA was restricted
to the majority of lymphocytes, presumably T-lymphocytes. Infrequently occurring dense cytoplasmic (lysosomal) bodies
were reactive with a variety of lectins, and a weak diffuse nuclear labelling was observable with LPA, UEA-I, WGA and
Con A. It is tempting to speculate that carbohydrate moieties on plasma membranes may be involved in the complex
mechanisms characterizing cell-to-cell interactions (adhesion) and particularly in the so-called phenomenon of homing.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
174.
Eugene Y.D. Chua Vinod K. Vogirala Oviya Inian Andrew S.W. Wong Lars Nordenski?ld Juergen M. Plitzko Radostin Danev Sara Sandin 《Nucleic acids research》2016,44(17):8013-8019
The Volta phase plate is a recently developed electron cryo-microscopy (cryo-EM) device that enables contrast enhancement of biological samples. Here we have evaluated the potential of combining phase-plate imaging and single particle analysis to determine the structure of a small protein–DNA complex. To test the method, we made use of a 200 kDa Nucleosome Core Particle (NCP) reconstituted with 601 DNA for which a high-resolution X-ray crystal structure is known. We find that the phase plate provides a significant contrast enhancement that permits individual NCPs and DNA to be clearly identified in amorphous ice. The refined structure from 26,060 particles has an overall resolution of 3.9 Å and the density map exhibits structural features consistent with the estimated resolution, including clear density for amino acid side chains and DNA features such as the phosphate backbone. Our results demonstrate that phase-plate cryo-EM promises to become an important method to determine novel near-atomic resolution structures of small and challenging samples, such as nucleosomes in complex with nucleosome-binding factors. 相似文献
175.
D I Smith R Mangrulker R Geist J Gilbert K Kinsman H Drabkin W Golembieski 《Genomics》1989,4(4):453-459
We have generated chromosome 3-specific recombinant libraries in both lambda and cosmid cloning vectors starting with somatic cell hybrids (hamster/human) containing either an intact chromosome 3 or a chromosome 3 with an interstitial deletion removing 75% of long-arm sequences. The libraries contained between 2 X 10(5) and 5 X 10(6) independent recombinants. Approximately 2% of the recombinants in these libraries contain inserts of human DNA. These were identified by hybridizing the recombinants to radioactively labeled total human DNA. Over 2500 recombinants containing human DNA were isolated from these various libraries and DNA was prepared from each of them. This represents 80,000 kb of cloned chromosome 3 sequences. One-third of the DNAs were digested with EcoRI or HindIII, and fragments free of repetitive sequences were radioactively labeled using random hexanucleotide primers and tested as unique sequence hybridization probes. Over 6500 of the fragments were tested and of these 758 were unique sequence probes with minimal or no background hybridization. Their hybridization only to chromosome 3 was verified. These probes, which were derived from 452 independent recombinants, should provide an effective saturation of human chromosome 3. 相似文献
176.
177.
Organisms present in methanogenic freshwater lake sediments from the vicinity of Athens, Georgia, were adapted to mineralize
2,4-dichlorophenol. Repeated addition of 0.5 to 2.7 mmol/liter of phenol, and later of 0.5–6.2 mmol/liter p-hydroxybenzoate
(p-OHB), to such enrichments led to the conversion of p-OHB to phenol at a rate of up to 100 mmol p-OHB per liter per day.
Subsequently, a spore-forming, obligately anaerobic bacterium, strain JW/Z-1, was isolated which transformed p-OHB to phenol
and 3,4-dihydroxybenzoate (3,4-OHB) to catechol (1,2-dihydroxybenzene) stoichiometrically without further metabolism of the
phenols. The strain did not transform benzoate, 4-chlorophenol, 2,4-dichlorophenol, 4-chlorobenzoate, o- and m-hydroxybenzoate,
2,4- and 3,5-dihydroxybenzoate, 2,3,4- and 3,4,5-trihydroxybenzoate, or 4-aminobenzoate. Yeast extract was required for growth
of strain JW/Z-1 and only high concentrations of casein hydrolysate or tryptone could substitute it, to some extent. Except
for sodium acetate, and some amino acids together with a 20-fold increased concentration of vitamins, no single carbohydrate
or defined organic compound has been found to support growth of this strain in the presence (or in the absence) of 0.2 to
0.5% (w/v) yeast extract. The fermentation products during growth on yeast extract indicated that the metabolism of amino
acid degradation was the major source for growth. The decarboxylating activity was inducible by p-OHB for the decarboxylation
of p-OHB, and at a lower rate for 3,4-OHB, and by 3,4-OHB only for 3,4-OHB, suggesting that two different enzyme systems exist.
The addition of the aromatic amino acids phenol or benzoate did not induce the decarboxylation activity in cultures growing
with yeast extract. Growth was observed at temperatures ranging from 12–41°C (Topt, 33–34°C) and at pH-values ranging from 6.0–10.0 (pHopt, 7.2–8.2). The shortest doubling time observed for strain JW/Z-1 was 3.2 hours. 相似文献
178.
Emilio García‐Rosell Cstor Guisande Luis Gonzlez‐Vilas Jacinto Gonzlez‐Dacosta Juergen Heine Elisa Prez‐Costas Jorge M. Lobo 《Ecography》2019,42(9):1613-1622
Species distribution models (SDMs) are broadly used to predict species distributions from available presence data. However, SDMs results have been criticized for several reasons mainly related to two basic characteristics of most SDMs: 1) general lack of reliable species absence information, 2) the frequent use of an arbitrary geographical extent (GE) or accessible area of the species. These impediments have motivated us to generate a procedure called niche of occurrence (NOO). NOO provides the probable distribution of species (realized niche) relying solely on partial information about presence of species. It operates within a natural geographical extent delimited by available observations and avoids using misleading thresholds to obtain binary presence–absence estimations when the species prevalence is unknown. In this study the main characteristics of NOO are presented, comparing its performance with other recognized and more complex SDMs by using virtual species to avoid the omnipresent error sources of real data sets. 相似文献
179.
180.
Helen M. Berman Paul D. Adams Alexandre A. Bonvin Stephen K. Burley Bridget Carragher Wah Chiu Frank DiMaio Thomas E. Ferrin Margaret J. Gabanyi Thomas D. Goddard Patrick R. Griffin Juergen Haas Christian A. Hanke Jeffrey C. Hoch Gerhard Hummer Genji Kurisu Catherine L. Lawson Alexander Leitner Andrej Sali 《Structure (London, England : 1993)》2019,27(12):1745-1759