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991.
David T Martin Marc J Quod Christopher J Gore Edward F Coyle 《Journal of applied physiology》2005,99(4):1628-9; author reply 1629
This case describes the physiological maturation from ages 21 to 28 yr of the bicyclist who has now become the six-time consecutive Grand Champion of the Tour de France, at ages 27-32 yr. Maximal oxygen uptake (Vo(2max)) in the trained state remained at approximately 6 l/min, lean body weight remained at approximately 70 kg, and maximal heart rate declined from 207 to 200 beats/min. Blood lactate threshold was typical of competitive cyclists in that it occurred at 76-85% Vo(2max), yet maximal blood lactate concentration was remarkably low in the trained state. It appears that an 8% improvement in muscular efficiency and thus power production when cycling at a given oxygen uptake (Vo(2)) is the characteristic that improved most as this athlete matured from ages 21 to 28 yr. It is noteworthy that at age 25 yr, this champion developed advanced cancer, requiring surgeries and chemotherapy. During the months leading up to each of his Tour de France victories, he reduced body weight and body fat by 4-7 kg (i.e., approximately 7%). Therefore, over the 7-yr period, an improvement in muscular efficiency and reduced body fat contributed equally to a remarkable 18% improvement in his steady-state power per kilogram body weight when cycling at a given Vo(2) (e.g., 5 l/min). It is hypothesized that the improved muscular efficiency probably reflects changes in muscle myosin type stimulated from years of training intensely for 3-6 h on most days. 相似文献
992.
Recent comparative studies have shown that, in many instances, the genetic network underlying the development of distinct organ systems is similar in invertebrate and vertebrate organisms. Genetically well-characterized, simple invertebrate model systems, such as Caenorhabditis elegans and Drosophila melanogaster, can thus provide useful insight for understanding more complex organ systems in vertebrates. Here, we summarize recent progress in the genetic analysis of tracheal development in Drosophila and compare the results to studies aimed at a better understanding of lung development in mouse and man. Clearly, both striking similarities and important differences are apparent, but it might still be too early to conclude whether the former or the latter prevail. 相似文献
993.
Endocrine regulation of energy metabolism by the skeleton 总被引:23,自引:0,他引:23
Lee NK Sowa H Hinoi E Ferron M Ahn JD Confavreux C Dacquin R Mee PJ McKee MD Jung DY Zhang Z Kim JK Mauvais-Jarvis F Ducy P Karsenty G 《Cell》2007,130(3):456-469
The regulation of bone remodeling by an adipocyte-derived hormone implies that bone may exert a feedback control of energy homeostasis. To test this hypothesis we looked for genes expressed in osteoblasts, encoding signaling molecules and affecting energy metabolism. We show here that mice lacking the protein tyrosine phosphatase OST-PTP are hypoglycemic and are protected from obesity and glucose intolerance because of an increase in beta-cell proliferation, insulin secretion, and insulin sensitivity. In contrast, mice lacking the osteoblast-secreted molecule osteocalcin display decreased beta-cell proliferation, glucose intolerance, and insulin resistance. Removing one Osteocalcin allele from OST-PTP-deficient mice corrects their metabolic phenotype. Ex vivo, osteocalcin can stimulate CyclinD1 and Insulin expression in beta-cells and Adiponectin, an insulin-sensitizing adipokine, in adipocytes; in vivo osteocalcin can improve glucose tolerance. By revealing that the skeleton exerts an endocrine regulation of sugar homeostasis this study expands the biological importance of this organ and our understanding of energy metabolism. 相似文献
994.
Diouf D Samba-Mbaye R Lesueur D Ba AT Dreyfus B de Lajudie P Neyra M 《Microbial ecology》2007,54(3):553-566
The occurrence and the distribution of rhizobial populations naturally associated to Acacia seyal Del. were characterized in 42 soils from Senegal. The diversity of rhizobial genotypes, as characterized by polymerase chain
reaction restriction fragment length polymorphism (RFLP) analysis of 16S–23S rDNA, performed on DNA extracted from 138 nodules
resulted in 15 clusters. Results indicated the widespread occurrence of compatible rhizobia associated to A. seyal in various ecogeographic areas. However, the clustering of rhizobial populations based on intergenic spacer (IGS) RFLP profiles
did not reflect their geographic origin. Four genera were discriminated on the basis of 16S rRNA gene sequences of the strains
representative for the IGS-RFLP profiles. The majority of rhizobia associated to A. seyal were affiliated to Mesorhizobium and Sinorhizobium 64 and 29%, respectively, of the different IGS-RFLP profiles. Our results demonstrate the coexistence inside the nodule of
plant-pathogenic non-N2-fixing Agrobacterium and Burkholderia strains, which induced the formation of ineffective nodules, with symbiotic rhizobia. Nodulation was recorded in saline soils
and/or at low pH values or in alkaline soils, suggesting adaptability of natural rhizobial populations to major ecological
environmental stress and their ability to establish symbiotic associations within these soil environments. These results contribute
to the progressing research efforts to uncover the biodiversity of rhizobia and to improve nitrogen fixation in agroforestry
systems in sub-Saharan Africa. 相似文献
995.
Diversity, activity, and abundance of sulfate-reducing bacteria in saline and hypersaline soda lakes
Foti M Sorokin DY Lomans B Mussman M Zacharova EE Pimenov NV Kuenen JG Muyzer G 《Applied and environmental microbiology》2007,73(7):2093-2100
Soda lakes are naturally occurring highly alkaline and saline environments. Although the sulfur cycle is one of the most active element cycles in these lakes, little is known about the sulfate-reducing bacteria (SRB). In this study we investigated the diversity, activity, and abundance of SRB in sediment samples and enrichment cultures from a range of (hyper)saline soda lakes of the Kulunda Steppe in southeastern Siberia in Russia. For this purpose, a polyphasic approach was used, including denaturing gradient gel electrophoresis of dsr gene fragments, sulfate reduction rate measurements, serial dilutions, and quantitative real-time PCR (qPCR). Comparative sequence analysis revealed the presence of several novel clusters of SRB, mostly affiliated with members of the order Desulfovibrionales and family Desulfobacteraceae. We detected sulfate reducers and observed substantial sulfate reducing rates (between 12 and 423 micromol/dm(3) day(-1)) for most lakes, even at a salinity of 475 g/liter. Enrichments were obtained at salt saturating conditions (4 M Na(+)), using H(2) or volatile fatty acids as electron donors, and an extremely halophilic SRB, strain ASO3-1, was isolated. Furthermore, a high dsr gene copy number of 10(8) cells per ml was detected in a hypersaline lake by qPCR. Our results indicate the presence of diverse and active SRB communities in these extreme ecosystems. 相似文献
996.
Melles DC van Leeuwen WB Snijders SV Horst-Kreft D Peeters JK Verbrugh HA van Belkum A 《Journal of microbiological methods》2007,69(2):371-375
We compared multilocus sequence typing (MLST), pulsed-field gel electrophoresis (PFGE), and amplified fragment length polymorphism (AFLP) for typing of Staphylococcus aureus and show that the methods yield similar results, although with differences in resolving power and reproducibility. Epidemiological conditions should determine which is the optimal typing method to be used. 相似文献
997.
Rho GTPase-activating bacterial toxins: from bacterial virulence regulation to eukaryotic cell biology 总被引:1,自引:0,他引:1
Studies on the interactions of bacterial pathogens with their host have provided an invaluable source of information on the major functions of eukaryotic and prokaryotic cell biology. In addition, this expanding field of research, known as cellular microbiology, has revealed fascinating examples of trans-kingdom functional interplay. Bacterial factors actually exploit eukaryotic cell machineries using refined molecular strategies to promote invasion and proliferation within their host. Here, we review a family of bacterial toxins that modulate their activity in eukaryotic cells by activating Rho GTPases and exploiting the ubiquitin/proteasome machineries. This family, found in human and animal pathogenic Gram-negative bacteria, encompasses the cytotoxic necrotizing factors (CNFs) from Escherichia coli and Yersinia species as well as dermonecrotic toxins from Bordetella species. We survey the genetics, biochemistry, molecular and cellular biology of these bacterial factors from the standpoint of the CNF1 toxin, the paradigm of Rho GTPase-activating toxins produced by urinary tract infections causing pathogenic Escherichia coli. Because it reveals important connections between bacterial invasion and the host inflammatory response, the mode of action of CNF1 and its related Rho GTPase-targetting toxins addresses major issues of basic and medical research and constitutes a privileged experimental model for host-pathogen interaction. 相似文献
998.
Hahnke K Jacobsen M Gruetzkau A Gruen JR Koch M Emoto M Meyer TF Walduck A Kaufmann SH Mollenkopf HJ 《Journal of biotechnology》2007,128(1):1-13
Microarrays have rapidly become an indispensable tool for gene analysis. Microarray experiments can be cost prohibitive, however, largely due to the price of the arrays themselves. Whilst different methods for stripping filter arrays on membranes have been established, only very few protocols are published for thermal and chemical stripping of microarrays on glass. Most of these protocols for stripping microarrays on glass were developed in combination with specific surface chemistry and different coatings for covalently immobilizing presynthesized DNA in a deposition process. We have developed a method for stripping commercial in situ microarrays using a multi-step procedure. We present a method that uses mild chemical degradation complemented by enzymatic treatment. We took advantage of the differences in biochemical properties of covalently linked DNA oligonucleotides on in situ synthesized microarrays and the antisense cRNA hybridization probes. The success of stripping protocols for microarrays on glass was critically dependent on the type of arrays, the nature of sample used for hybridization, as well as hybridization and washing conditions. The protocol employs alkali hydrolysis of the cRNA, several enzymatic degradation steps using RNAses and Proteinase K, combined with appropriate washing steps. Stripped arrays were rehybridized using the same protocols as for new microarrays. The stripping method was validated with microarrays from different suppliers and rehybridization of stripped in situ arrays yielded comparable results to hybridizations done on unused, new arrays with no significant loss in precision or accuracy. We show that stripping of commercial in situ arrays is feasible and that reuse of stripped arrays gave similar results compared to unused ones. This was true even for biological samples that show only slight differences in their expression profiles. Our analyses indicate that the stripping procedure does not significantly influence data quality derived from post-primary hybridizations. The method is robust, easy to perform, inexpensive, and results after reuse are of comparable accuracy to new arrays. 相似文献
999.
Koen Gillis Johan Gielis Hilde Peeters Emmy Dhooghe Jan Oprins 《Plant Cell, Tissue and Organ Culture》2007,91(2):115-123
A reliable protocol for mass propagation via somatic embryogenesis in mature bamboos has been established using pseudospikelets
of Bambusa balcooa. Fourty percent of the explants gave rise to multiple regenerants within 4 months. This conversion rate is sufficiently high
to use the process in commercial mass production. Further, shoot apical meristems can also be used as primary explants without
lost of efficiency.
Regenerated plants were uniform and identical to the mother plant and to plants obtained by axillary branching with respect
to growth characteristics and morphology. Furthermore, epigenetic changes could not be detected by Methylation Sensitive AFLP
(MSAP). During the complete process no changes in ploidy level could be observed.
The process allows for a cost reduction for this tropical bamboo for forestry of up to 57% compared to micropropagation via
axillary branching. For the first time, a reliable process based on somatic embryogenesis has been developed that is well
suited for commercial micropropagation of elite mature bamboos. 相似文献
1000.
Marc Ereshefsky 《Biology & philosophy》2007,22(5):659-674
This article takes up the project of studying psychological categories as homologies. Ethologists have numerous theoretical
ideas concerning the phylogeny and ontogeny of behavioral homologies. They also have well-developed operational methods for
testing behavioral homologies. Many of these theoretical ideas and operational criteria can be applied to psychological homologies.
This paper suggests that insights from ethology should be incorporated in adaptationist and functionalist approaches to psychology.
Doing so would strengthen those approaches. 相似文献