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921.
Distinct apoptotic phenotypes induced by radiation and ceramide in both p53-wild-type and p53-mutated lymphoblastoid cells 总被引:1,自引:0,他引:1
Shi YQ Wuergler FE Blattmann H Crompton NE 《Radiation and environmental biophysics》2001,40(4):301-308
The tumour suppressor gene p53 and the intracellular signalling molecule ceramide have both been shown to play crucial roles
in the induction of apoptosis by ionising radiation. In this study we examined whether p53 and ceramide are involved in independent
signal pathways, inducing different types of apoptosis. TK6 (p53wt/wt) and WTK1 (p53mut/mut) lymphoblastoid cells were treated with ionising radiation or N-acetyl-d-sphingosine (C2-ceramide). Flow cytometry and fluorescence microscopy studies were performed to characterise the time kinetics and morphological
features of induced apoptosis. Ceramide- and radiation-induced apoptotic cells display characteristic differences in morphology
and DNA staining and ceramide-induced apoptosis is expressed much faster than radiation-induced apoptosis. Radiation-induced
apoptosis is p53-dependent and ceramide-induced apoptosis is p53-independent. The p53 pathway and the ceramide pathway are
two independent signal pathways leading to distinct types of apoptosis. Since p53 is very often dysfunctional in tumour cells,
modifying the ceramide pathway is a promising strategy to increase tumour sensitivity to radiation and other anticancer agents.
Received: 19 April 2001 / Accepted: 15 October 2001 相似文献
922.
A primer set was designed for the specific detection of methanotrophic bacteria in forest soils by PCR. The primer sequences
were derived from highly conservative regions of the pmoA gene, encoding the α-subunit of the particulate methane monooxygenase present in all methanotrophs. In control experiments
with genomic DNA from a collection of different type I, II, and X methanotrophs, it could be demonstrated that the new primers
were specific for members of the genera Methylosinus, Methylocystis, Methylomonas, Methylobacter, and Methylococcus. To test the suitability of the new primers for the detection of particulate methane monooxygenase (pMMO) containing methanotrophs
in environmental samples we used DNA extracts from an acid spruce forest soil. For simple and rapid purification of the DNA
extracts, the samples were separated by electrophoresis on a low-melting-point agarose gel. This allowed us to efficiently
separate the DNA from coextracted humic acids. The DNA from the melted agarose gel was ready for use in PCR reactions. In
PCR reactions with DNA from the Ah soil layer, products of the correct size were amplified by PCR by use of the new primers.
By sequencing of cloned PCR products, it could be confirmed that the PCR products represented partial sequences with strong
similarity to the pmoA gene. The sequence was most related to the pmoA sequence of a type II methanotroph strain isolated from the Ah layer of the investigated soils.
Received: 1 September 2000 / Accepted: 2 October 2000 相似文献
923.
Glycoproteins, as a class of biomolecules, exhibit much more heterogeneous structures than non-glycosylated proteins. They present a challenging area of research. Model glycoproteins with well-defined protein and carbohydrate structures are helpful in the search for high-resolution methods for the separation of glycoproteins. Neoglycoproteins, maltose-modified chymotrypsin and lactose-modified chymotrypsin, were synthesised by modifying chymotrypsin with maltose and lactose, respectively, using the reductive amination method. Boronate chromatography was applied to isolate the neoglycoproteins from non-glycosylated substances. The use of Tris–HCl as a shielding reagent during the boronate chromatography proved to be efficient in eliminating unwanted interactions between the boronate ligand and the peptide backbone of chymotrypsin. The retention time of neoglycoproteins on the boronate column was increased with increasing the degree of modification. 相似文献
924.
In this technical note we describe the setup and application of automated sample preparation and usage of flow-through NMR equipment for the characterization of ligand binding on proteins. In addition, we focus on the perspectives of automated analysis of 2D HSQC spectra to identify changes in patterns indicative for ligand binding or changes of sample conditions. In this context we discuss a combination of statistical and non-statistical data analysis. 相似文献
925.
Phenology in central Europe – differences and trends of spring phenophases in urban and rural areas 总被引:5,自引:0,他引:5
Roetzer T Wittenzeller M Haeckel H Nekovar J 《International journal of biometeorology》2000,44(2):60-66
In order to examine the impacts of both large-scale and small-scale climate changes (urban climate effect) on the development
of plants, long-term observations of four spring phenophases from ten central European regions (Hamburg, Berlin, Cologne,
Frankfurt, Munich, Prague, Vienna, Zurich, Basle and Chur) were analysed. The objective of this study was to identify and
compare the differences in the starting dates of the pre-spring phenophases, the beginning of flowering of the snowdrop (Galanthus nivalis) and forsythia (Forsythia sp.), and of the full-spring phenophases, the beginning of flowering of the sweet cherry (Prunus avium) and apple (Malus domestica), in urban and rural areas. The results indicate that, despite regional differences, in nearly all cases the species studied
flower earlier in urbanised areas than in the corresponding rural areas. The forcing in urban areas was about 4 days for the
pre-spring phenophases and about 2 days for the full-spring phenophases. The analysis of trends for the period from 1951 to
1995 showed tendencies towards an earlier flowering in all regions, but only 22% were significant at the 5% level. The trends
for the period from 1980 to 1995 were much stronger for all regions and phases: the pre-spring phenophases on average became
earlier by 13.9 days/decade in the urban areas and 15.3 days/decade in the rural areas, while the full-spring phenophases
were 6.7 days earlier/decade in the urban areas and 9.1 days/decade earlier in the rural areas. Thus rural areas showed a
higher trend towards an earlier flowering than did urban areas for the period from 1980 to 1995. However, these trends, especially
for the pre-spring phenophases, turned out to be extremely variable.
Received: 21 October 1999 / Revised: 5 April 2000 / Accepted: 25 April 2000 相似文献
926.
927.
Noninvasive and/or nondestructive techniques are capable of providing more macro- or microstructural information about bone than standard bone densitometry. Although the latter provides important information about osteoporotic fracture risk, numerous studies indicate that bone strength is only partially explained by bone mineral density. Quantitative assessment of macro- and microstructural features may improve our ability to estimate bone strength. The methods available for quantitatively assessing macrostructure include (besides conventional radiographs) quantitative computed tomography (QCT) and volumetric quantitative computed tomography (vQCT). Methods for assessing microstructure of trabecular bone noninvasively and/or nondestructively include high-resolution computed tomography (hrCT), micro-computed tomography (muCT), high-resolution magnetic resonance (hrMR), and micromagnetic resonance (muMR). vQCT, hrCT and hrMR are generally applicable in vivo; muCT and muMR are principally applicable in vitro. Although considerable progress has been made in the noninvasive and/or nondestructive imaging of the macro- and microstructure of bone, considerable challenges and dilemmas remain. From a technical perspective, the balance between spatial resolution versus sampling size, or between signal-to-noise versus radiation dose or acquisition time, needs further consideration, as do the trade-offs between the complexity and expense of equipment and the availability and accessibility of the methods. The relative merits of in vitro imaging and its ultrahigh resolution but invasiveness versus those of in vivo imaging and its modest resolution but noninvasiveness also deserve careful attention. From a clinical perspective, the challenges for bone imaging include balancing the relative advantages of simple bone densitometry against the more complex architectural features of bone or, similarly, the deeper research requirements against the broader clinical needs. The considerable potential biological differences between the peripheral appendicular skeleton and the central axial skeleton have to be addressed further. Finally, the relative merits of these sophisticated imaging techniques have to be weighed with respect to their applications as diagnostic procedures requiring high accuracy or reliability on one hand and their monitoring applications requiring high precision or reproducibility on the other. 相似文献
928.
Detection of apoptosis in tissue sections 总被引:17,自引:0,他引:17
During the last few years, detection of apoptosis has evolved from a predominantly morphological basis to the use of ever more specific techniques. The methods widely used to visualize DNA fragmentation in tissue sections are now supplemented by a variety of specific antisera against components of the cell death pathways. Essential requirements for apoptosis detection techniques include high sensitivity for apoptotic cells, the ability to differentiate between apoptotic and necrotic cell death and other forms of DNA damage, and the distinction between different stages of the cell death process. In this overview, we will focus on recent technical advances in apoptosis detection covering improvements of in situ DNA fragmentation techniques, as well as pointing out some of the new tools available for the detection of apoptotic cells in tissue. 相似文献
929.
930.
Different sublines of Jurkat cells respond with varying susceptibility of internucleosomal DNA degradation to different mediators of apoptosis 总被引:2,自引:0,他引:2
The ability of two different Jurkat sublines, termed standard and JM, to form DNA ladders was investigated after various apoptotic stimuli. Exposure to a broad spectrum of drugs interfering with signal transduction or cellular metabolism revealed distinct differences between both Jurkat sublines with regard to the pattern of DNA degradation. In standard Jurkat cells, internucleosomal DNA cleavage occurred only after treatment with the protein kinase inhibitor staurosporine. In contrast, the JM subline responded with internucleosomal DNA fragmentation to exposure to gemcitabine, cycloheximide or staurosporine. All drugs induced the formation of DNA fragments of about 50 kb in both sublines, as revealed by pulse field electrophoresis, except H2O2, which caused unspecific DNA degradation. The staurosporine-induced DNA ladder formation was accompanied by an increase in caspase-3 activity in both lines which, however, was considerably lower in Jurkat JM cells after gemcitabine or cycloheximide exposure. When the analysis of internucleosomal DNA degradation was carried out after mycoplasma infection, both Jurkat lines responded with DNA ladder formation after exposure to all drugs used (here only shown for the standard subline). Employing the zymogram technique, nuclease activities of 47 kDa and 54 kDa were detected in culture supernatants, cell homogenates and nuclear extracts only when mycoplasma-infected, whereas the samples obtained from mycoplasma-free sublines were nuclease-negative using this technique, indicating that these endonucleases were of mycoplasmal origin. After drug exposure, the mycoplasmal nucleases must have gained access to the cytoplasm and nuclei of their host cells by an unknown mechanism. 相似文献