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51.
Three-dimensional gas exchange pathways in pome fruit characterized by synchrotron x-ray computed tomography 总被引:4,自引:0,他引:4
Verboven P Kerckhofs G Mebatsion HK Ho QT Temst K Wevers M Cloetens P Nicolaï BM 《Plant physiology》2008,147(2):518-527
Our understanding of the gas exchange mechanisms in plant organs critically depends on insights in the three-dimensional (3-D) structural arrangement of cells and voids. Using synchrotron radiation x-ray tomography, we obtained for the first time high-contrast 3-D absorption images of in vivo fruit tissues of high moisture content at 1.4-microm resolution and 3-D phase contrast images of cell assemblies at a resolution as low as 0.7 microm, enabling visualization of individual cell morphology, cell walls, and entire void networks that were previously unknown. Intercellular spaces were always clear of water. The apple (Malus domestica) cortex contains considerably larger parenchyma cells and voids than pear (Pyrus communis) parenchyma. Voids in apple often are larger than the surrounding cells and some cells are not connected to void spaces. The main voids in apple stretch hundreds of micrometers but are disconnected. Voids in pear cortex tissue are always smaller than parenchyma cells, but each cell is surrounded by a tight and continuous network of voids, except near brachyssclereid groups. Vascular and dermal tissues were also measured. The visualized network architecture was consistent over different picking dates and shelf life. The differences in void fraction (5.1% for pear cortex and 23.0% for apple cortex) and in gas network architecture helps explain the ability of tissues to facilitate or impede gas exchange. Structural changes and anisotropy of tissues may eventually lead to physiological disorders. A combined tomography and internal gas analysis during growth are needed to make progress on the understanding of void formation in fruit. 相似文献
52.
Penski N Härtle S Rubbenstroth D Krohmann C Ruggli N Schusser B Pfann M Reuter A Gohrbandt S Hundt J Veits J Breithaupt A Kochs G Stech J Summerfield A Vahlenkamp T Kaspers B Staeheli P 《Journal of virology》2011,85(15):7730-7741
From infection studies with cultured chicken cells and experimental mammalian hosts, it is well known that influenza viruses use the nonstructural protein 1 (NS1) to suppress the synthesis of interferon (IFN). However, our current knowledge regarding the in vivo role of virus-encoded NS1 in chickens is much more limited. Here, we report that highly pathogenic avian influenza viruses of subtypes H5N1 and H7N7 lacking fully functional NS1 genes were attenuated in 5-week-old chickens. Surprisingly, in diseased birds infected with NS1 mutants, the IFN levels were not higher than in diseased birds infected with wild-type virus, suggesting that NS1 cannot suppress IFN gene expression in at least one cell population of infected chickens that produces large amounts of the cytokine in vivo. To address the question of why influenza viruses are highly pathogenic in chickens although they strongly activate the innate immune system, we determined whether recombinant chicken alpha interferon (IFN-α) can inhibit the growth of highly pathogenic avian influenza viruses in cultured chicken cells and whether it can ameliorate virus-induced disease in 5-week-old birds. We found that IFN treatment failed to confer substantial protection against challenge with highly pathogenic viruses, although it was effective against viruses with low pathogenic potential. Taken together, our data demonstrate that preventing the synthesis of IFN is not the primary role of the viral NS1 protein during infection of chickens. Our results further suggest that virus-induced IFN does not contribute substantially to resistance of chickens against highly pathogenic influenza viruses. 相似文献
53.
54.
Weiyu Yu Nicola A. Wardrop Robert E. S. Bain Yanzhao Lin Ce Zhang Jim A. Wright 《PloS one》2016,11(3)
Following the recent expiry of the United Nations’ 2015 Millennium Development Goals (MDGs), new international development agenda covering 2030 water, sanitation and hygiene (WASH) targets have been proposed, which imply new demands on data sources for monitoring relevant progress. This study evaluates drinking-water and sanitation classification systems from national census questionnaire content, based upon the most recent international policy changes, to examine national population census’s ability to capture drinking-water and sanitation availability, safety, accessibility, and sustainability. In total, 247 censuses from 83 low income and lower-middle income countries were assessed using a scoring system, intended to assess harmonised water supply and sanitation classification systems for each census relative to the typology needed to monitor the proposed post-2015 indicators of WASH targets. The results signal a lack of international harmonisation and standardisation in census categorisation systems, especially concerning safety, accessibility, and sustainability of services in current census content. This suggests further refinements and harmonisation of future census content may be necessary to reflect ambitions for post-2015 monitoring. 相似文献
55.
Identification of suitable endogenous control genes for microRNA gene expression analysis in human breast cancer 总被引:2,自引:0,他引:2
Pamela A Davoren Roisin E McNeill Aoife J Lowery Michael J Kerin Nicola Miller 《BMC molecular biology》2008,9(1):76
The discovery of microRNAs (miRNAs) added an extra level of intricacy to the already complex system regulating gene expression.
These single-stranded RNA molecules, 18–25 nucleotides in length, negatively regulate gene expression through translational
inhibition or mRNA cleavage. The discovery that aberrant expression of specific miRNAs contributes to human disease has fueled
much interest in profiling the expression of these molecules. Real-time quantitative PCR (RQ-PCR) is a sensitive and reproducible
gene expression quantitation technique which is now being used to profile miRNA expression in cells and tissues. To correct
for systematic variables such as amount of starting template, RNA quality and enzymatic efficiencies, RQ-PCR data is commonly
normalised to an endogenous control (EC) gene, which ideally, is stably-expressed across the test sample set. A universal
endogenous control suitable for every tissue type, treatment and disease stage has not been identified and is unlikely to
exist, so, to avoid introducing further error in the quantification of expression data it is necessary that candidate ECs
be validated in the samples of interest. While ECs have been validated for quantification of mRNA expression in various experimental
settings, to date there is no report of the validation of miRNA ECs for expression profiling in breast tissue. In this study,
the expression of five miRNA genes (let-7a, miR-10b, miR-16, miR-21 and miR-26b) and three small nucleolar RNA genes (RNU19, RNU48 and Z30) was examined across malignant, benign and normal breast tissues to determine the most appropriate normalisation strategy.
This is the first study to identify reliable ECs for analysis of miRNA by RQ-PCR in human breast tissue. 相似文献
56.
George A. Wudiri Suzanne M. Pritchard Hong Li Jin Liu Hector C. Aguilar Stacey D. Gilk Anthony V. Nicola 《Journal of virology》2014,88(23):13918-13922
Herpes simplex virus 1 (HSV-1) required cholesterol or desmosterol for virion-induced membrane fusion. HSV successfully entered DHCR24−/− cells, which lack a desmosterol-to-cholesterol conversion enzyme, indicating that entry can occur independently of cholesterol. Depletion of desmosterol from these cells resulted in diminished HSV-1 entry, suggesting a general sterol requirement for HSV-1 entry and that desmosterol can operate in virus entry. Cholesterol functioned more effectively than desmosterol, suggesting that the hydrocarbon tail of cholesterol influences viral entry. 相似文献
57.
Vronique Roig-Zamboni Sarah Barelier Robert Dixon Nicola F. Galley Amani Ghanem Quoc Phong Nguyen Hloize Cahuzac Bartomiej Salamaga Peter J. Davis Yves Bourne Stphane Mesnage Florence Vincent 《The Journal of biological chemistry》2022,298(5)
The cleavage of septal peptidoglycan at the end of cell division facilitates the separation of the two daughter cells. The hydrolases involved in this process (called autolysins) are potentially lethal enzymes that can cause cell death; their activity, therefore, must be tightly controlled during cell growth. In Enterococcus faecalis, the N-acetylglucosaminidase AtlA plays a predominant role in cell separation. atlA mutants form long cell chains and are significantly less virulent in the zebrafish model of infection. The attenuated virulence of atlA mutants is underpinned by a limited dissemination of bacterial chains in the host organism and a more efficient uptake by phagocytes that clear the infection. AtlA has structural homologs in other important pathogens, such as Listeria monocytogenes and Salmonella typhimurium, and therefore represents an attractive model to design new inhibitors of bacterial pathogenesis. Here, we provide a 1.45 Å crystal structure of the E. faecalis AtlA catalytic domain that reveals a closed conformation of a conserved β-hairpin and a complex network of hydrogen bonds that bring two catalytic residues to the ideal distance for an inverting mechanism. Based on the model of the AtlA–substrate complex, we identify key residues critical for substrate recognition and septum cleavage during bacterial growth. We propose that this work will provide useful information for the rational design of specific inhibitors targeting this enterococcal virulence factor and its orthologs in other pathogens. 相似文献
58.
Magdalena Brzezowska Francesca Bernardi Nicola Gaggelli Gianni Valensin 《Journal of inorganic biochemistry》2010,104(2):193-198
Teicoplanin, a member of the “last chance” antibiotic family has a similar structure and the same mechanism of action as parent drug vancomycin, which is proved to be an effective binder of Cu(II) ions. However, the potentiometric and spectroscopic studies (UV-visible, CD, NMR) have shown that the modification of the N-terminal structure of the peptide backbone in teicoplanin affects considerably the binding ability towards Cu(II) ions. While vancomycin forms almost instantly the stable 3 N complex species involving the N-terminal and two amide nitrogen donors, in case of teicoplanin only two nitrogen donors derived from the N-terminal amino group and adjacent peptide bond are coordinated to Cu(II) ion within the whole pH range studied. The major factor influencing the binding mode is most likely the structure of the N-terminus of the peptide unit in the antibiotic ligand. 相似文献
59.
The effective dose-50 (ED-50) for halothane anesthesia was studied in 45 male Mongolian gerbils at age 12 weeks. Close control of circadian variation and animal temperature was maintained. Regression analysis for the percent of animals moving in response to a standard stimulus revealed an ED-50 of 1.32 volumes %, a concentration that approximates the ED-50 of the rat. 相似文献
60.