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991.
Invasions by introduced ant species can be ecologically destructive and affect a wide range of taxa, particularly native ants. Invasive ant species often numerically dominate ant communities and outperform native ant species in effective resource acquisition. Here, we describe interactions between the invasive ant Anoplolepis gracilipes (Smith) and resident ant species in disturbed habitats in NE Borneo. We measured interference competition abilities of A. gracilipes by performing arena bioassays between two A. gracilipes colonies and seven local ant species, and measured its effective resource competition at baits within supercolonies and at supercolony boundaries. Furthermore, we compared ant species diversity and composition at baits among (A) core areas of A. gracilipes supercolonies, (B) supercolony boundaries and (C) outside supercolonies. Anoplolepis gracilipes was behaviorally dominant over most ant species except Oecophylla smaragdina. Within supercolonies, A. gracilipes discovered all food baits first, and monopolized the vast majority throughout the course of the experiment. At supercolony boundaries, A. gracilipes discovered baits later than resident ant species, but subsequently monopolized half of the baits. Furthermore, the activity and diversity of the ant community within A. gracilipes supercolonies was lower than at its boundaries and outside supercolonies, and the ant communities differed significantly between infested and noninfested areas. Our study supports the hypothesis that successful establishment of A. gracilipes in anthropogenically disturbed habitats may negatively affect resident ant communities through high levels of direct interspecific aggression and almost complete monopolization of resources within high‐density supercolonies. 相似文献
992.
993.
Tetsuya Shiga Heike Althen Miriam Cornella Katarzyna Zarnowiec Hirooki Yabe Carles Escera 《PloS one》2015,10(9)
The mismatch negativity (MMN) provides a correlate of automatic auditory discrimination in human auditory cortex that is elicited in response to violation of any acoustic regularity. Recently, deviance-related responses were found at much earlier cortical processing stages as reflected by the middle latency response (MLR) of the auditory evoked potential, and even at the level of the auditory brainstem as reflected by the frequency following response (FFR). However, no study has reported deviance-related responses in the FFR, MLR and long latency response (LLR) concurrently in a single recording protocol. Amplitude-modulated (AM) sounds were presented to healthy human participants in a frequency oddball paradigm to investigate deviance-related responses along the auditory hierarchy in the ranges of FFR, MLR and LLR. AM frequency deviants modulated the FFR, the Na and Nb components of the MLR, and the LLR eliciting the MMN. These findings demonstrate that it is possible to elicit deviance-related responses at three different levels (FFR, MLR and LLR) in one single recording protocol, highlight the involvement of the whole auditory hierarchy in deviance detection and have implications for cognitive and clinical auditory neuroscience. Moreover, the present protocol provides a new research tool into clinical neuroscience so that the functional integrity of the auditory novelty system can now be tested as a whole in a range of clinical populations where the MMN was previously shown to be defective. 相似文献
994.
Annika Wiebring Heike Helmholz Ilka Sötje Stephan Lassen Andreas Prange Henry Tiemann 《Marine biotechnology (New York, N.Y.)》2010,12(3):308-317
Jellyfish have an increasing impact on marine ecology. Cnidocysts bearing stinging cells afford, amongst others, prey capture
and defence. Several different types of stinging capsules are found in one species and they are supposed to have specific
functions, e.g. paralysing prey or adhering to it. Due to these assumed different roles of the capsules, it is suggested that
toxins, which are contained in the capsules, differ in composition. Analysis of distinct types of nematocysts requires an
appropriate method for the separation of the different types. Mixtures of types of nematocysts were obtained of two species
of jellyfish, Aurelia aurita and Cyanea lamarckii, by maceration of the tissue. These mixtures were treated with a method called laser microdissection and pressure catapulting
(LMPC). Optimized maceration methods, which were firstly introduced as a method for this purpose, in conjunction with optimized
LMPC parameters lead to sufficient amounts of separated capsules of individual types for subsequent mass-spectrometric analyses.
In case of A. aurita, the resulting mass spectra had some constituents in common, whereas in the overall pattern, the two distinct nematocyst
types differed. 相似文献
995.
Heike Lindner Sharon A. Kessler Lena M. Müller Hiroko Shimosato-Asano Aurélien Boisson-Dernier Ueli Grossniklaus 《PLoS biology》2015,13(4)
Pollen tube (PT) reception in flowering plants describes the crosstalk between the male and female gametophytes upon PT arrival at the synergid cells of the ovule. It leads to PT growth arrest, rupture, and sperm cell release, and is thus essential to ensure double fertilization. Here, we describe TURAN (TUN) and EVAN (EVN), two novel members of the PT reception pathway that is mediated by the FERONIA (FER) receptor-like kinase (RLK). Like fer, mutations in these two genes lead to PT overgrowth inside the female gametophyte (FG) without PT rupture. Mapping by next-generation sequencing, cytological analysis of reporter genes, and biochemical assays of glycoproteins in RNAi knockdown mutants revealed both genes to be involved in protein N-glycosylation in the endoplasmic reticulum (ER). TUN encodes a uridine diphosphate (UDP)-glycosyltransferase superfamily protein and EVN a dolichol kinase. In addition to their common role during PT reception in the synergids, both genes have distinct functions in the pollen: whereas EVN is essential for pollen development, TUN is required for PT growth and integrity by affecting the stability of the pollen-specific FER homologs ANXUR1 (ANX1) and ANX2. ANX1- and ANX2-YFP reporters are not expressed in tun pollen grains, but ANX1-YFP is degraded via the ER-associated degradation (ERAD) pathway, likely underlying the anx1/2-like premature PT rupture phenotype of tun mutants. Thus, as in animal sperm–egg interactions, protein glycosylation is essential for the interaction between the female and male gametophytes during PT reception to ensure fertilization and successful reproduction. 相似文献
996.
Heike Kampe Claudia Dziallas Hans-Peter Grossart Norbert Kamjunke 《Microbial ecology》2010,60(3):618-627
As extreme environmental conditions strongly affect bacterial community composition (BCC), we examined whether differences
in pH—even at low pH—and in iron and sulfate concentrations lead to changes in BCC of acidic mining lakes. Thereby, we tested
the following hypotheses: (1) diversity of the bacterial community in acidic lakes decreases with reducing pH, (2) BCC differs
between epilimnion and hypolimnion, and (3) BCC in extremely acidic environments does not vary much over time. Therefore,
we investigated the BCC of three acidic lakes with different pH values (2.3, 2.7, and 3.2) by denaturing gradient gel electrophoresis
(DGGE) and subsequent sequencing of DGGE bands as well as catalyzed reporter deposition-FISH (CARD-FISH). BCC did not significantly
vary among the studied lakes nor differ much between water layers. In contrast, BCC significantly changed over time, which
is contradictory to our hypotheses. Bacterial communities were dominated by Alpha-, Beta-, and Gammaproteobacteria, whereas
Actino- and Acidobacteria rarely occurred. Cell numbers of both free and attached bacteria were positively related to DOC
concentration. Overall, low pH and extreme chemical conditions of the studied lakes led to similar assemblages of bacteria
with pronounced temporal differences. This notion indicates that temporal changes in environmental conditions including food
web structure also affect unique communities of bacteria thriving at low pH. 相似文献
997.
Hoffmann K Daum G Köster M Kulicke WM Meyer-Rammes H Bisping B Meinhardt F 《Applied and environmental microbiology》2010,76(24):8211-8221
By targeted deletion of the polyglutamate operon (pga) in Bacillus licheniformis F11, a derivative form, F11.1 (Δpga), was obtained that, along with lacking polyglutamate (PGA) formation, displayed enhanced proteolytic activities. The phenotypic properties were maintained in a strain in which the chiBA operon was additionally deleted: F11.4 (ΔchiBA Δpga). These genetically modified strains, carrying the Δpga deletion either alone (F11.1) or together with the ΔchiBA (F11.4) deletion, were used in fermentations (20-liter scale) aiming at the deproteinization of shrimp shells in order to obtain long-chain chitin. After chemical deacetylation, the resulting chitosan samples were analyzed by nuclear magnetic resonance spectroscopy, size exclusion chromatography, and viscometry and compared to a chitosan preparation that was produced in parallel by chemical methods by a commercial chitosan supplier (GSRmbH). Though faint lipid impurities were present in the fermented polysaccharides, the viscosity of the material produced with the double-deletion mutant F11.4 (Δpga ΔchiBA) was higher than that of the chemically produced and commercially available samples (Cognis GmbH). Thus, enhanced proteolytic activities and a lack of chitinase activity render the double mutant F11.4 a powerful tool for the production of long-chain chitosan. 相似文献
998.
Kurt Schmidt Margit Rehn Heike Stessel Gerald Wölkart Bernd Mayer 《Free radical biology & medicine》2010,48(1):145-152
Several cardiovascular disorders, including atherosclerosis and tolerance to the antianginal drug nitroglycerin (GTN), may be associated with the generation of superoxide anions, which react with nitric oxide (NO) to yield peroxynitrite. According to a widely held view, oxidation of tetrahydrobiopterin (BH4) by peroxynitrite causes uncoupling of endothelial NO synthase (eNOS), resulting in reduced NO bioavailability and endothelial dysfunction under conditions of oxidative stress. In this study we determined the levels of reduced biopterins and endothelial function in cultured cells exposed to peroxynitrite and GTN as well as in blood vessels isolated from GTN-tolerant guinea pigs and rats. BH4 was rapidly oxidized by peroxynitrite and 3-morpholino sydnonimine (SIN-1) in buffer, but this was prevented by glutathione and not observed in endothelial cells exposed to SIN-1 or GTN. Prolonged treatment of the cells with 0.1 mM GTN caused slow NG-nitro-l-arginine-sensitive formation of reactive oxygen species without affecting eNOS activity. Endothelial function and BH4/BH2 levels were identical in blood vessels of control and GTN-tolerant animals. Our results suggest that peroxynitrite-triggered BH4 oxidation does not occur in endothelial cells or GTN-exposed blood vessels. GTN seems to trigger minor eNOS uncoupling that is unrelated to BH4 depletion and without observable consequence on eNOS function. 相似文献
999.
Christian Griebler Heide Stein Claudia Kellermann Sven Berkhoff Heike Brielmann Susanne Schmidt Drazenka Selesi Christian Steube Andreas Fuchs Hans Jürgen Hahn 《Ecological Engineering》2010,36(9):1174-1190
Environmental policy and in particular the European water legislation, in the framework of the EU Groundwater Directive, has started to consider groundwater not only as a resource but as a living ecosystem. A precondition for comprehensive groundwater protection is thus the assessment of the biological and ecological state. The assessment of ecosystems requires consideration of ecological criteria, which so far are not available for groundwater systems. In the framework of a national project, the German Federal Environment Agency (UBA) supports a consortium of scientists and stakeholders from water boards and regional environmental authorities to develop a first concept for an ecological assessment scheme for groundwater ecosystems. The attempts towards an integrative concept include the following steps: (i) selection of appropriate biological and ecological parameters, (ii) typology of groundwater ecosystems, (iii) derivation of a reference status (Leitbild) and natural background values for biological variables, (iv) identification of potential bioindicators and definition of threshold values, and (v) development of an assessment model. These proposed steps are discussed on the basis of a data set from two groundwater landscapes in Southern Germany. Investigations considered three different spatial units, i.e. the habitat unit at the local scale, and the aquifer type unit as well as the landscape unit at the regional scale. Fauna as well as bacterial communities could provide valuable ecological information on the ecosystems status. The paper reviews ‘state of the art’ knowledge and evaluates the near future perspectives for the development and implementation of groundwater ecosystems assessment programmes. 相似文献
1000.