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901.
N Matsunami B Smith L Ballard M W Lensch M Robertson H Albertsen C O Hanemann H W Müller T D Bird R White 《Nature genetics》1992,1(3):176-179
Charcot-Marie-Tooth disease 1A (CMT1A) is a hereditary demyelinating peripheral neuropathy, associated with a DNA duplication on chromosome 17p11.2. A related disorder in the mouse, trembler (Tr), maps to mouse chromosome 11 which has syntenic homology to human chromosome 17p. Recently, the peripheral myelin protein-22 (pmp-22) gene was identified as the likely Tr locus. We have constructed a partial yeast artificial chromosome contig spanning the CMT1A gene region and mapped the PMP-22 gene to the duplicated region. These observations further implicate PMP-22 as a candidate gene for CMT1A, and suggest that over-expression of this gene may be one mechanism that produces the CMT1A phenotype. 相似文献
902.
Site-directed mutagenesis reveals role of mobile arginine residue in lactate dehydrogenase catalysis 总被引:6,自引:0,他引:6
The binding of substrates to lactate dehydrogenases induces a marked rearrangement of the protein structure in which a 'loop' of polypeptide (residues 98-110) closes over the active site of the enzyme. In this rearrangement, arginine 109 (a basic residue conserved in all known lactate dehydrogenase sequences and in the homologous malate dehydrogenases) moves 0.8 nm from a position in the solvent to one in the active site where its guanidinium group resides within hydrogen bonding distance of both the reactive carbonyl of pyruvate and imidazole ring of the catalytic histidine 195 (see Fig. 1). Whilst this feature of the enzyme has been commented upon previously, the function of this mobile arginine residue during catalysis has not been tested experimentally. The advent of protein engineering has now enabled us to define the role of this basic residue by substituting it with the neutral glutamine. Transient kinetic and equilibrium studies of the mutant enzyme indicate that arginine 109 enhances the polarization of the pyruvate carbonyl group in the ground state and stabilizes the transition state. The gross active-site structure of the enzyme is not altered by the mutation since an alternative catalytic function of the enzyme (rate of addition of sulphite to NAD+), which does not require hydride transfer, is insensitive to the arginine----glutamine substitution. 相似文献
903.
J. F. Hofert T. N. Mahowald N. A. Mahowald M. L. Heidrick 《Cellular and molecular life sciences : CMLS》1988,44(1):37-38
Summary To determine if thymic macrophages have insulin receptors, alternate sections of rat thymus were stained with FITC-insulin and examined for nonspecific esterase (ANAE) activity. Cells showing a diffuse ANAE staining pattern also bound FITC-insulin. These cells were concentrated in the cortico-medullary border and increased in number following administration of cortisol. Thymic macrophages may be insulin-dependent and therefore could be malfunctional in diabetes. 相似文献
904.
N A Bersinger 《Experientia》1984,40(9):1022-1024
Purified pregnancy associated plasma protein A (PAPP-A) can be effectively bound to polystyrene microtitre plates. This immobilized antigen competes with the added serum PAPP-A of unknown concentration for the limited amount of peroxidase-labeled monospecific anti-PAPP-A antibody incubated simultaneously. The sensitivity is 0.1 WHO unit/ml and non-specific binding is 1.0%. 相似文献
905.
J W Sixbey E H Vesterinen J G Nedrud N Raab-Traub L A Walton J S Pagano 《Nature》1983,306(5942):480-483
Epstein-Barr virus (EBV), a member of the herpes group of viruses and the aetiological agent of infectious mononucleosis, is usually thought of as a lymphotrophic virus with the ability to transform B lymphocytes. So the association of EBV with nasopharyngeal carcinoma is puzzling, especially given the lack of success of attempts to infect epithelial cells with EBV in culture and the apparent lack of EBV receptors on epithelial cells. Circumvention of the apparent requirement for membrane receptors by techniques of transfection, microinjection and receptor transplantation has clearly demonstrated that there is no inherent barrier to EBV replication in nonlymphoid cells, including epithelial cell types. Our ability routinely to detect EBV DNA by in situ hybridization in epithelial cells of the oropharynx from persons with acute infectious mononucleosis suggests that, in vivo, EBV regularly gains access to and replicates lytically in epithelial cells. We report here in vitro evidence for direct infection by EBV and replication of the virus in cultured normal human epithelial cells. 相似文献
906.
Cystic kidneys from the mutant CPK strain of C57BL/6J mice were cultured in serum-free organ culture. During 120 h of incubation in chemically-defined medium, CPK cystic tubular changes underwent complete regression. Environmental factors regulate the expression of genetically determined polycystic kidney disease in this model. 相似文献
907.
908.
Plasmids of the same Inc groups in Enterobacteria before and after the medical use of antibiotics 总被引:8,自引:0,他引:8
Conjugative plasmids were common in enterobacteria isolated before the medical use of antibiotics. Plasmid F of Escherichia coli K-12 was one example and we identified others in over 20% of a collection of strains isolated between 1917 and 1954, the Murray collection. In the past 25 years, conjugative plasmids encoding antibiotic resistances have become common in bacteria of the same genera as those of the Murray Collection--Salmonella, Shigella, Klebsiella, Proteus, Escherichia. The present study was made to show whether the 'pre-antibiotic' plasmids belonged to the same groups, as defined by incompatibility tests (Inc groups), as modern R plasmids. Of 84 such plasmids established in E. coli K-12, none with antibiotic resistance determinants, 65 belonged to the same groups as present resistance (R) plasmids. Thus the remarkable way in which medically important bacteria have acquired antibiotic resistance in the past 25 years seems to have been by the insertion of new genes into existing plasmids rather than by the spread of previously rare plasmids. 相似文献
909.
Influence of the enteric surface coat on the unidirectional flux of acetamide across the wall of rat small intestine 总被引:1,自引:0,他引:1
In vivo treatment of the jejunal mucosa with glycosidic enzymes seems to remove the enteric surface coat of the enterocyte. As a consequence, the mucosa-to-serosa unidirectional flux of acetamide increases remarkably. The glycocalyx probably represents a barrier to the diffusion of small hydrosoluble solutes. 相似文献
910.
Kurokawa Y. Takahashi M. Hayashi Y. Ohno Y. Takamura N. 《Cellular and molecular life sciences : CMLS》1983,39(12):1404-1407
Cellular and Molecular Life Sciences - Glandular stomachs of fetal and newborn Wistar rats were transplanted s.c. after treatment in vitro with N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) at... 相似文献