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71.
Glucose was oxidized in the presence of powdered TiO(2) photocatalysts synthesized by an ultrasound-promoted sol-gel method. The catalysts were more selective towards glucaric acid, gluconic acid and arabitol (total selectivity approx. 70%) than the most popular photocatalyst, Degussa P-25. The photocatalytic systems worked at mild reaction conditions: 30°C, atmospheric pressure and very short reaction time (e.g. 5 min). Such relatively good selectivity towards high-valued molecules are attributed to the physico-chemical properties (e.g. high specific surface area, nanostructured anatase phase, and visible light absorption) of novel TiO(2) materials and the reaction conditions. The TiO(2) photocatalysts have potential for water purification and energy production and for use in the pharmaceutical, food, perfume and fuel industries. 相似文献
72.
Yoko Kunimitsu Tetsuhiro Togo Yoshikazu Sampei Akihiro Kano Kinya Yasui 《Palaeogeography, Palaeoclimatology, Palaeoecology》2009,280(3-4):499-506
We investigated the origin of organic matter and paleoceanographic conditions of the embryo-bearing lowermost Cambrian Kuanchuanpu Formation in Shaanxi Province, China, in terms of sedimentary facies, fossil morphometry, and organic geochemistry, including biomarker compositions. The results indicated the abundance of algae and eukaryotic phytoplankton that fueled a diverse ecosystem including cnidarians and small shelly fossils. The water column contained enough oxygen to provide habitat for benthic cnidarians such as Olivooides. On the other hand, low pristane/phytane ratios, detection of squalane, and hopane composition indicate reductive conditions within the sediments, and that the redox front was likely near the water-sediment interface. Common occurrences of pyrite and barite indicate that redox reactions of sulfur species were activated at the water-sediment interface. Such circumstances and the high phosphate concentration in ambient water may recall the presence of sulfur-oxidizing bacteria that promoted the phosphatization of animal embryos, as suggested for in the Neoproterozoic Doushantuo Formation. Nitrogen was the limiting nutrient for primary productivity, and the high phosphate concentration in the ocean promoted the phosphatization of animal embryos at the reductive water–sediment interface. 相似文献
73.
R. V. Gorjunova 《Paleontological Journal》2009,43(1):69-77
A new family of the order Rhabdomesida, Medvedkellidae fam. nov., is described. This family consists of a new genus, Medvedkella gen. nov., comprising three species transferred from the genus Rhombopora Meek, 1872: the type species M. riasanensis (Schulga-Nesterenko, 1955), M. diaphragmata (Schulga-Nesterenko, 1955), and M. mariae (Dunaeva, 1961). The morphogenesis of the first two species is studied. For the first time axial zooecia are revealed in the suborder Golgdfussitrypina, which existed in parallel with the suborder Rhabdomesina of the order Rhabdomesida. A hypothesis that the new family evolved from the subfamily Nicklesoporinae Gorjunova, 1985 of the family Goldfussitrypidae, 1985 is proposed. Some questions of the ecological adaptation of these bryozoans in the Late Carboniferous marine basin of the East European Platform are discussed. 相似文献
74.
Paulina Ducka Ulrich Eckhard Esther Schönauer Stefan Kofler Gerhard Gottschalk Hans Brandstetter Dorota Nüss 《Applied microbiology and biotechnology》2009,83(6):1055-1065
Clostridial collagenases are foe and friend: on the one hand, these enzymes enable host infiltration and colonization by pathogenic clostridia, and on the other hand, they are valuable biotechnological tools due to their capacity to degrade various types of collagen and gelatine. However, the demand for high-grade preparations exceeds supply due to their pathogenic origin and the intricate purification of homogeneous isoforms. We present the establishment of an Escherichia coli expression system for a variety of constructs of collagenase G (ColG) and H (ColH) from Clostridium histolyticum and collagenase T (ColT) from Clostridium tetani, mimicking the isoforms in vivo. Based on a setup of five different expression strains and two expression vectors, 12 different constructs were expressed, and a flexible purification platform was established, consisting of various orthogonal chromatography steps adaptable to the individual needs of the respective variant. This fast, cost-effective, and easy-to-establish platform enabled us to obtain at least 10 mg of highly pure mono-isoformic protein per liter of culture, ideally suited for numerous sophisticated downstream applications. This production and purification platform paves the way for systematic screenings of recombinant collagenases to enlighten the biochemical function and to identify key residues and motifs in collagenolysis. 相似文献
75.
Management under uncertainty: guide-lines for incorporating connectivity into the protection of coral reefs 总被引:5,自引:4,他引:1
L. J. McCook G. R. Almany M. L. Berumen J. C. Day A. L. Green G. P. Jones J. M. Leis S. Planes G. R. Russ P. F. Sale S. R. Thorrold 《Coral reefs (Online)》2009,28(2):353-366
The global decline in coral reefs demands urgent management strategies to protect resilience. Protecting ecological connectivity,
within and among reefs, and between reefs and other ecosystems is critical to resilience. However, connectivity science is
not yet able to clearly identify the specific measures for effective protection of connectivity. This article aims to provide
a set of principles or practical guidelines that can be applied currently to protect connectivity. These ‘rules of thumb’
are based on current knowledge and expert opinion, and on the philosophy that, given the urgency, it is better to act with
incomplete knowledge than to wait for detailed understanding that may come too late. The principles, many of which are not
unique to connectivity, include: (1) allow margins of error in extent and nature of protection, as insurance against unforeseen
or incompletely understood threats or critical processes; (2) spread risks among areas; (3) aim for networks of protected
areas which are: (a) comprehensive and spread—protect all biotypes, habitats and processes, etc., to capture as many possible
connections, known and unknown; (b) adequate—maximise extent of protection for each habitat type, and for the entire region;
(c) representative—maximise likelihood of protecting the full range of processes and spatial requirements; (d) replicated—multiple
examples of biotypes or processes enhances risk spreading; (4) protect entire biological units where possible (e.g. whole
reefs), including buffers around core areas. Otherwise, choose bigger rather than smaller areas; (5) provide for connectivity
at a wide range of dispersal distances (within and between patches), emphasising distances <20–30 km; and (6) use a portfolio
of approaches, including but not limited to MPAs. Three case studies illustrating the application of these principles to coral
reef management in the Bohol Sea (Philippines), the Great Barrier Reef (Australia) and Kimbe Bay (Papua New Guinea) are described. 相似文献
76.
Dipl.-Geol. Fritz Neuweiler 《Facies》1993,29(1):231-249
The Middle Albian sequence from the western marginal area of the Vasco-Cantabrian Basin contains calcified microbialites in
different marine depositional environments, individually well defined by microstructure, lamina characteristics and mode of
formation. Microbialites may form the primary framework of reefs, which occur as composite stacks in mid to lower slope environments
or as isolated bodies in small intraplatform basins. In most areas microbialite reef growth was initiated below the photic
zone. Stratiform intercalations of microbialites and composite microbialite/foraminifer oncoids are restricted to well bedded
carbonate platform deposits (Urgonian). Three basis types of microbialites are recognized:
The results of geochemical analyses indicate a rock-buffered diagenetic system during early diagenetic and burial history
of microbialite reefs. Independent of microbialite type residual MgCO3-contents are in the range of 1.20 to 3.57 mole %, agreeing well with those from isopachous rim cements and indicating a high
Mg-calcite precursor of microbialite micrites. Stable isotope values (δ13C) are in the range of 3.13 to 3.80 (permil, vs PDB), close to the internal standard, the coralline spongeAcanthochaetetes (Albian species=2.93; Recent species=3.27) and comparable with inorganically precipitated Mg-calcite. 相似文献
(i) | Dense micritic/fenestral microbialites corresponding to laterally linked, stacked stromatolitic hemispheroids. The development and preservation of stromatolitic structure is a function of sediment supply and secondary obliteration by succesive boring activities. They were calcified in situ at the surface with irregularly curved linings of microcrystalline carbonate. Dense micritic/ fenestral microbialites, variously developed and preserved, are the main contributors to microbialite reefs. Microbialites form hard substrates bored by lithophagous pelecypods and boring sponges (Aka sp.). The main associated faunal elements include lithistid and coralline demosponges, hexactinellid sponges, encrusting foraminifera, brachiopods, polychaetes, and bryozoans. |
(ii) | Dense micritic/peloidal microbialites with subplanar, arhythmic lamination (binding habit). They were calcified in situ below the surface in conjunction with decaying organic matter. At large scale, they occur in shallow water, i.e. within the photic zone. They cover earlier microbialite reefs or occur on and in episodic deposits of coarse biodebris. At small scale they occur in protected microenvironments (e.g. intraparticle space, boring cavities). |
(iii) | Peloidal/in situ ooid microbialites with subplanar/ wavy lamination occur as small-scale stratiform intercalations in carbonate platform deposits, episodically revealing physical reworking. Other features are very similar to dense micritic/peloidal microbialites. |
77.
Summary The development of peculiar margin facies and abundant talus breccias within the Dolomia Principale inner platform is commonly
observed in the Lombardy Basin during the Norian. The organisms building these margins are mainly serpulids, benthic microbes,
subordinate porostomata and other encrusting forms; typical margin organisms, as sponges or corals, are extremely rare or
absent. The build-ups form narrow rims along the borders of tectonic-controlled intraplatform basins. Regional back-stepping
and progradation of the margin facies on the talus breccias produced by the erosion of the reef is commonly observed in the
uppermost Dolomia Principale depositional system. Widespread occurrence of serpulids and microbial margins in middle-late
Norian times is indicative of stressed environmental conditions—fluctuation of salinity and temperature on the inner platform
and in the intraplatform basins—controlled by palaeogeographic setting. Physical characteristics allowed the bloom of forms
able to develop in a wide range of environmental conditions, such as serpulids.
In the Late Norian, major input of fine-grained clastics is recorded; close to the Norian-Rhaetian boundary, carbonate ramps
were regionally restored. Locally, small serpulid and microbial bioconstructions still persist in the lowermost part of the
shaly succession, even if they are less abundant with respect to the Dolomia Principale. Patch-reefs generally do not build
a platform margin, but represent isolated mounds within shaly deposits. These build-ups occur on the edge of former structural
highs; the communities survived the environmental change responsible for the siliciclastic input and locally managed to produce
mounds during the deposition of the lower part of the upper depositional system (Riva di Solto Shale). 相似文献
78.
79.
Dr. Anna Climaco Prof. Dr. Maria Boni Dr. Alessandro Iannace Prof. Dr. Valeria Zamparelli 《Facies》1997,36(1):37-56
Summary The Upper Triassic carbonates of the area comprised between Maratea (Lucania) and Praia a Mare (Calabria) have been studied.
They have been grouped into six facies assemblages which, in turn, define two depositional systems.
The algal and bivalve dolomites represent typical peritidal platform sediments arranged in cyclical patterns formed as shoal
barrier and back-reef deposits periodically emerged and deformed in tepee structures.
The outer margin of the platform was colonised by peculiar bioconstructions dominated by microbialites and serpulids; little
sponges occur less frequently, whereas rare corals have been found only in some turbiditic beds.
Along the slope, in a distance that can be estimated in 5 or 6 km, the coarse breccias give way to coarse turbidites, then
finer turbidites and finally to dark, organic-rich micrites. Most of the floatstone and associated turbidites imply a fault-
controlled slope. The laminated texture and the high O.M. (Organic Matter) content of the latter facies quite obviously point
to a basin with poorly oxygenated bottom waters.
In the uppermost Triassic there is an indication of a regressive trend, evidenced by the progradation of the platform facies.
At that time a back-reef area was characterised by Megalodontid prairies alternated to areas of sandy bioclastic transport.
However, due to the poor biostratigraphic record and intense cataclasis, no definite evidence of a well-structured Rhaetian
platform margin with buildups and related basinal sediments exists.
These sedimentary and paleoecological features match well with those found in the intraplatform basins of the Dolomia Principale,
as well as with other coeval facies in Southern Apennines, Central Apennines, Southern Alps and in Southern Spain. Altogether,
this evidence suggests that in the Norian time both Southern Alps and Apennines experienced a very similar tectonic evolution
and comparable paleoceanographic conditions, characterised by the formation of numerous intraplatform throughs with restricted
circulation, the latter influencing the bottom conditions as well as the marginal communities. The margins of these restricted
basins, differently from the typical Dachstein reefs of the Upper Triassic Tethys, were dominated by microbial-serpulid communities. 相似文献
1) | a platform margin depositional system, comprising algae-bivalves-bearing dolomites (A1), Megalodontid-bearing limestones and dolomites (A2), dololutites and stromatolitic/bioclastic dolomites. (A3); |
2) | a slope to basin depositional system comprising: buildup-facies, talus breccia and coarse to fine doloarenites (B1), coarse to fine doloarenites and dark laminated dololutites (B2), dark laminated dololutites (B3). |
80.
Summary Reef facies, reef types and their biotic associations in the Maiella platform margin (central Italy) provide qualitative evidence
for a significant reef decline across the Cretaceous/Tertiary (K/T) boundary, and indicate two phases of reef recovery during
the Paleocene. Rudists dominated the reef community until the latest Cretaceous. A significant sea-level fall around the time
of the K/T boundary is documented by a truncation surface associated with emersion.
During sea-level highstands in the Danian to Early Thanetian and, more extensively, during the Late Thanetian, coral-algal
patch-reefs grew along the platform margin and top. Already in the Danian to Early Thanetian, the reef communities were more
diverse and the constructional types more evolved than previously known from this time. Differences between the Danian to
Early Thanetian coral association, the Late Thanetian association, and Late Cretaceous coral faunas may have ecological or
evolutionary causes.
Repeated emergence produced a complex diagenetic history in the Danian to Lower Thanetian limestones. All Paleocene reefs
were displaced by gravitative redeposition. Coral-algal reefs are less important in the Early to mid Eocene, when alveolinid
foraminifera dominated on the Maiella shelf. Reefs on the Maiella platform diversified and attained large sizes in the Late
Eocene to Early Oligocene, as known from other Mediterranean platforms.
The external controls on the Late Cretaceous to Oligocene evolution and demise of reef communities that are most easily demonstrated
with our data are sealevel fluctuations and climate change. We propose that the change in reef biota and reef types across
the K/T boundary and during the Early Tertiary were important causes of the parallel changes in platform growth style. 相似文献