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921.
Asbjörn M. Svardal Dr. Ian F. Pryme Helge Dalen 《Molecular and cellular biochemistry》1981,34(3):165-175
Summary The endoplasmic reticulum (ER) of MPC-11 cells released as vesicles upon cell disruption by nitrogen cavitation was separated
from the bulk of mitochondria, lysosomes and plasma membranes by a low speed centrifugation. The ER membranes were fractionated
on discontinuous sucrose gradients into heavy rough (HR), light rough (LR) and smooth (S) membranes. The morphology of subcellular
fractions was studied by electron microscopy and the ER membranes were shown to be virtually free of contaminating organelles.
The S fraction was easily distinguishable because of the lack of ribosomes but there were no apparent morphological differences
between the HR and LR fractions. Of total activity in the microsomal subfractions, 70% of the UDPase and 67% of the 5′-nucleotidase
activity was associated with the S fraction. Polysomes were present in the HR, LR and nuclear-associated ER fractions but
not in the S fraction. The HR and LR fractions did not appear to be contaminated to any great extent with free polysomes.
RNA/protein and RNA/phospholipid ratios of the HR fraction were higher than those of the LR fraction, indicating a greater
density of ribosomes in the former fraction. These ratios were much lower in the S fraction reflecting the low ribosome content. 相似文献
922.
923.
Helge Tolleshaug Trond Berg Kari Holte 《Biochimica et Biophysica Acta (BBA)/General Subjects》1982,714(1):114-121
The effects of local anesthetics, including procaine and dibucaine, and some related amine compounds, such as dansyl-cadaverine, were studied with respect to their effects on the uptake and degradation of asialo-glycoproteins in isolated hepatocytes 0.5 mM of either dibucaine or dansyl-cadaverine reduced the rates of uptake to 18–19% of control values; other amines were less effective. Dibucaine and dansyl-cadaverine both acted by reducing the surface binding capacity of the cells as well as by reducing the rate of internalization of surface-bound asialo-glycoprotein. All of the compounds that affected the uptake, including dansyl-cadaverine, also reduced the rate of degradation. This effect could be studied separately from their effect on uptake. The concentrations that were required in order to reduce degradation were, in general, 0.5-0.25 of those which caused a reduction in the uptake. Even though dibucaine, lidocaine and dansyl-cadaverine were found to accumulate in the lysosomes, it was concluded from studies with isopycnic centrifugation in sucrose gradients that all three compounds inhibited the rate of transfer of endocytosed protein from endocytic vesicles to lysosomes. This effect could be due to a reduced rate of fusion between endocytic vesicles and lysosomes. 相似文献
924.
Question: Can vegetation relevé databases be used to analyse species losses and gains in specific vegetation types in Germany over time? Does the type of response (increase or decline in relative frequency) conform to observed large‐scale environmental trends in the last decades? Location: Germany. Exploring the German Vegetation Reference Database Halle (GVRD) that was established for forest and grassland vegetation within the framework of German Biodiversity Exploratories. Methods: Use of generalized linear models (GLMs) for testing changes in temporal frequency of plant taxa in a semi‐dry grassland data set (Mesobromion) and a beech forest data set (Fagion). Data were either aggregated by year, decade or by a balanced re‐sampling approach. Interpretation of the observed changes was based on species traits. Results: In both data sets significant temporal changes were observed, although the frequency of the majority of species remained unchanged. In both data sets, species with a temporal increase in frequency had higher Ellenberg N and F indicator values, compared to species that decreased, thus indicating effects of widespread atmospheric nitrogen deposition. In the forest data set, the observed increase in recruitment of deciduous trees pointed to a change in management, while trends in the grassland data set suggested use abandonment, as seen in an increased frequency of woody species. Conclusion: We demonstrate that vegetation databases represent very valuable resources for analysis of temporal changes in species frequencies. GLMs proved their value in detecting these trends, as also shown by the interpretability of model results with species traits. In contrast, the method of aggregation or re‐sampling had little influence on the general outcome of analyses. 相似文献
925.
Tim A Sch?ner Sebastian W Fuchs Christian Sch?nau Helge B Bode 《Microbial biotechnology》2014,7(3):232-241
Bacteria from the Bacteroidetes phylum are known producers of the chemotaxonomic relevant flexirubins. These orange pigments comprise a non-isoprenoid aryl-polyene carboxylic acid esterified with a dialkylresorcinol. Herein, we report a gene cluster from Chitinophaga pinensis encoding the biosynthesis of the polyene moiety and the biochemical characterization of a tyrosine ammonia-lyase and a 4-coumarate-CoA ligase responsible for the initiation of the polyene biosynthesis. Additionally, the flexirubin of C. pinensis was characterized by a combination of feeding experiments, high-performance liquid chromatography tandem mass spectrometry and matrix-assisted laser desorption/ionization mass spectrometry. 相似文献
926.
Aim To test whether species groups (i.e. assemblages of species co‐occurring in nature) that are statistically derived at one scale (broad, medium, or fine scale) can be transferred to another scale, and to identify the driving forces that determine species groups at the various scales. Location Northern Bohemia (Czech Republic, central Europe) in the Je?tědský h?bet mountain range and its neighbourhood. Methods Three data sets were sampled: a floristic data set at the broad scale, another floristic data set at the intermediate scale, and a vegetation data set at the habitat scale. First, in each data set, species groups were produced by the COCKTAIL algorithm, which ensures maximized joint occurrence in the data set using a fidelity coefficient. Corresponding species groups were produced in the individual data sets by employing the same species for starting the algorithm. Second, the species groups formed in one data set, i.e. at a particular scale, were applied crosswise to the other data sets, i.e. to the other scales. Correspondence of a species group formed at a particular scale with a species group at another scale was determined. Third, to highlight the driving factors for the distribution of the plant species groups at each scale, canonical correspondence analysis was carried out. Results Twelve species groups were used to analyse the transferability of the groups across the three scales, but only six of them were found to be common to all scales. Correspondence of species groups derived from the finest scale with those derived at the broadest scale was, on average, higher than in the opposite direction. Forest (tree layer) cover, altitude and bedrock type explained most of the variability in canonical correspondence analysis across all scales. Main conclusions Transferability of species groups distinguished at a fine scale to broader scales is better than it is in the opposite direction. Therefore, a possible application of the results is to use species groups to predict the potential occurrence of missing species in broad‐scale floristic surveys from fine‐scale vegetation‐plot data. 相似文献
927.
The lymphatic system is important for body fluid balance as well as immunological surveillance. Due to the identification of new molecular markers during the last decade, there has been a recent dramatic increase in our knowledge on the molecular mechanisms involved in lymphatic vessel growth (lymphangiogenesis) and lymphatic function. Here we review data showing that although it is often overlooked, the extracellular matrix plays an important role in the generation of new lymphatic vessels as a response to physiological and pathological stimuli. Extracellular matrix-lymphatic interactions as well as biophysical characteristics of the stroma have consequences for tumor formation, growth and metastasis. During the recent years, anti-lymphangiogenesis has emerged as an additional therapeutic modality to the clinically applied anti-angiogenesis strategy. Oppositely, enhancement of lymphangiogenesis in situations of lymph accumulation is seen as a promising strategy to a set of conditions where few therapeutic avenues are available. Knowledge on the interaction between the extracellular matrix and the lymphatics may enhance our understanding of the underlying mechanisms and may ultimately lead to better therapies for conditions where reduced or increased lymphatic function is the therapeutic target. 相似文献
928.
Helge G. Gyllenberg Mats Gyllenberg Timo Koski Tatu Lund Jiri Schindler 《Quantitative Microbiology》1999,1(2):157-170
We discuss the taxonomy of Enterobacteriaceae in the light of classification by minimization of stochastic complexity (SC). A classification which minimizes SC is optimal from the point of view of information theory. It was found that the SC-minimizing classification of a large database of strains of Enterobacteriaceae resulted in structures which correspond well to the conclusions of experts on the taxonomy of Enterobacteriaceae. The approach based on minimization of SC can therefore be considered as useful in bacterial taxonomy. 相似文献
929.
Summary Based upon a material comprising human foetuses cytochemical studies of a widespread type of cell were carried out. Apart from amoeboid mobility the cell is characterized by pinocytotic and phagocytotic activity.In early development stages these cells are seen intravascularly and penetrating the vessels. Later they are seen in connection with the formation of the vascular epiphyseal cartilaginous canals and in the vitreous body, the synovial joints and dental anlage. Furthermore these cells are seen at the removal of the epithelial cells of the dental lamina and the junctional epithelium in the two palatine processes. The cells concerned are seen also in the deep periosteal layer at the centre of the diaphysis synchronously with the vaseularization of the periosteum and prior to the periosteal invasion. Based upon morphology and cytochemistry the theory is advanced that these cells form the chondroclasts and the multinucleated osteoclasts. By contrast, the diaphysial osteoblasts are derived from invading pre-osteoblasts from the cambium-layer of the periosteum.These cells are also seen along the basal surface of the neural apparatus and invading the brain vesicles.On the basis of morphology and cytochemistry the cell type is designated a histiocyte and its origin is traced back to primitive leucocytes.This work has been supported by grants from the Danish State Research Foundation, the Rask-Ørsted Foundation and The Association for the Aid of the Crippled Children, New York. 相似文献
930.
Robert Huber Helge Meggers Karl-Heinz Baumann Maureen E. Raymo Rüdiger Henrich 《Palaeogeography, Palaeoclimatology, Palaeoecology》2000,160(3-4):193-212
We present measurements of the maximum diameter of the planktonic foraminifer Neogloboquadrina pachyderma sin. from six sediment cores (Ocean Drilling Program sites 643, 644, 907, 909, 985 and 987) from the Norwegian–Greenland Sea. Our data show a distinct net increase in mean shell size of N. pachyderma sin. at all sites during the last 1.3 Ma, with largest shell sizes reached after 0.4 Ma. External factors such as glacial–interglacial variability and carbonate dissolution alone cannot account for the observed variation in mean shell size of N. pachyderma sin. We consider the observed shell size increase to mirror an evolutionary trend towards better adaptation of N. pachyderma sin. to the cold water environment after 1.1–1.0 Ma. Probably, the Mid Pleistocene climate shift and the associated change of amplitude and frequency of glacial–interglacial fluctuations have triggered the evolution of this planktonic foraminifer. Oxygen and carbon stable isotope analyses of different shell size classes indicate that the observed shell size increase could not be explained by the functional concept that larger shells promote increasing sinking velocities during gametogenesis. For paleoceanographic reconstructions, the evolutionary adaptation of Neogloboquadrina pachyderma sin. to the cold water habitat has significant implications. Carbonate sedimentation in highest latitudes is highly dependent on the presence of this species. In the Norwegian–Greenland Sea, carbonate-poor intervals before 1.1 Ma are, therefore, not necessarily related to severe glacial conditions. They are probably attributed to the absence of this not yet polar-adapted species. Further, transfer function and modern analog techniques used for the reconstruction of surface water conditions in high latitudes could, therefore, contain a large range of errors if they were applied to samples older than 1.1–1.0 Myrs. 相似文献