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21.
Summary Heating by microwave irradiation (microwaving) is a controllable way to accelerate most processes of diffusion and many chemical reactions occurring in histoprocessing and histochemistry. Consequently, microwaving can be particularly time-saving. However, apart from desirable accelerations, unwanted diffusions and reactions may also occur. These can generate artefacts such as extraction of tissue components, chemical alterations of cellular content, and decomposition of thermally labile staining reagents. Artefacts may arise at all stages of histoprocessing, from fixation, through embedding, to staining. Whereas all artefacts result from heating, some specifically involve microwave ovens; e.g. irregular heating due to inhomogeneities in the microwave field, and ageing of the magnetron.Microwaving can involve certain hazards. Most of them also arise in conventional ovens, but a few are unique to microwave ovens; for example, aqueous contents heating faster than glass containers, and sparking due to labels written in pencil. The trouble-shooting of microwave procedures requires an understanding of the nature of the heating process and of the procedure in question. In order to achieve this, the development and application of trouble-shooting charts for commonly used procedures is both recommended and illustrated. 相似文献
22.
Summary Mutual correction of co-cultivated fibroblasts from patients with Hunter's and Hurler's syndrome could be inhibited by either fructose 1-phosphate or mannose 6-phosphate. In the presence of fructose 1-phosphate a 50% mixture of fibroblasts from a patient with Hunter's syndrome and a normal homozygous individual showed an increased35S-sulphate incorporation into acid mucopolysaccharides. When fibroblast cultures from one obligate and two possible carriers of Hunter's syndrome were tested for35S-sulphate incorporation, the cultures showed either twice the normal35S-sulphate incorporation into acid mucopolysaccharides in the presence of fructose 1-phosphate or an abnormally high incorporation in the presence as well as in the absence of the sugar phosphate. 相似文献
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Using mouse thymocytes, mitogen-induced [3H]thymidine incorporation was compared with a recently developed flow-cytometric technique, based on acridine orange staining of cells, which differentiates the G0 and G1 phase of thymocytes. PHA induces a transient but considerable G0-G1 shift without any substantial proliferation. On the other hand, crude supernatants derived from Con A-stimulated human peripheral blood mononuclear cells induce only a minor G0-G1 shift and no proliferation. However, PHA in the presence of this supernatant induced an increased [3H]thymidine uptake in thymocytes and a shift from G1 to S. These results support the current hypothesis that a factor present in Con A-activated supernatants in conjunction with PHA stimulation indeed facilitates the entrance of G1 cells into the S phase. The flow-cytometric technique might be used in the study of the interaction of endogenous mediators with exogenous mitogenic agents in activating lymphocytes to proceed through the initial G0-G1 phases of the cell cycle. 相似文献
24.
A Honig B Flemming U Rauhut D Roloff R B?ge P Matthiess J Walther 《Acta biologica et medica Germanica》1975,34(6):1025-1036
The carotid chemoreceptors of narcotized, vagotomized and spontaneously breathing hydropenic cats in hypertonic mannite diuresis were stimulated by perfusion with venous blood penic cats in hypertonic mannite diuresis were stimulated by perfusion with venous blood for 70 min. Elevation of blood pressure at the innervated kidneys was prevented by an automatically controlled balloon located within the aorta. Stimulation of the chemoreceptors intensified respiration and raised the arterial systemic pressure. With the renal arteries at constant pressure, the effective renal plasma flow and the glomerular filtration rate significantly declined. The filtration fraction remained unchanged. The absolute urinary and sodium excretion did not change significantly, whereas the fractional time-volume, fractional sodium excretion, and the fractional osmotic excretion significantly increased. The fractional tubular reabsorption of osmotically free water was significantly enhanced. These reactions subsided during subsequent perfusion of the glomerula carotici with arterial blood. The results suggest that tubular sodium reabsorption is inhibited by stimulation of the carotid chemoreceptors, although re-adjustment of renal perfusion and filtrate volume cannot be excluded. 相似文献
25.
Based on the high-resolution X-ray crystallographic structure of phospholipase C from Bacillus cereus, the orientation of the phosphatidylcholine substrate in the active site of the enzyme is proposed. The proposal is based on extensive calculations using the GRID program and molecular mechanics geometry relaxations. The substrate model has been constructed by successively placing phosphate, choline and diacylglycerol moieties in the positions indicated from GRID calculations. On the basis of the resulting orientation of a complete phosphatidylcholine molecule, we propose a mechanism for the hydrolysis of the substrate. 相似文献
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Nils Offen Johannes Flemming Hares Kamawal Ruhel Ahmad Wanja Wolber Christian Geis Holm Zaehres Hans R Sch?ler Hannelore Ehrenreich Albrecht M Müller Anna-Leena Sirén 《Molecular medicine (Cambridge, Mass.)》2013,19(1):399-408
Induced cell fate changes by reprogramming of somatic cells offers an efficient strategy to generate autologous pluripotent stem (iPS) cells from any adult cell type. The potential of iPS cells to differentiate into various cell types is well established, however the efficiency to produce functional neurons from iPS cells remains modest. Here, we generated panneural progenitor cells (pNPCs) from mouse iPS cells and investigated the effect of the neurotrophic growth factor erythropoietin (EPO) on their survival, proliferation and neurodifferentiation. Under neural differentiation conditions, iPS-derived pNPCs gave rise to microtubule-associated protein-2 positive neuronlike cells (34% to 43%) and platelet-derived growth factor receptor positive oligodendrocytelike cells (21% to 25%) while less than 1% of the cells expressed the astrocytic marker glial fibrillary acidic protein. Neuronlike cells generated action potentials and developed active presynaptic terminals. The pNPCs expressed EPO receptor (EPOR) mRNA and displayed functional EPOR signaling. In proliferating cultures, EPO (0.1–3 U/mL) slightly improved pNPC survival but reduced cell proliferation and neurosphere formation in a concentration-dependent manner. In differentiating cultures EPO facilitated neurodifferentiation as assessed by the increased number of β-III-tubulin positive neurons. Our results show that EPO inhibits iPS pNPC self-renewal and promotes neurogenesis. 相似文献
30.
Jessica K. van Frankenhuyzen Jack T. Trevors Cecily A. Flemming Hung Lee Marc B. Habash 《Journal of industrial microbiology & biotechnology》2013,40(11):1251-1261
Biosolids result from treatment of sewage sludge to meet jurisdictional standards, including pathogen reduction. Once government regulations are met, materials can be applied to agricultural lands. Culture-based methods are used to enumerate pathogen indicator microorganisms but may underestimate cell densities, which is partly due to bacteria existing in a viable but non-culturable physiological state. Viable indicators can also be quantified by real-time polymerase chain reaction (qPCR) used with propidium monoazide (PMA), a dye that inhibits amplification of DNA found extracellularly or in dead cells. The objectives of this study were to test an optimized PMA-qPCR method for viable pathogen detection in wastewater solids and to validate it by comparing results to data obtained by conventional plating. Reporter genes from genetically marked Pseudomonas sp. UG14Lr and Agrobacterium tumefaciens 542 cells were spiked into samples of primary sludge, and anaerobically digested and Lystek-treated biosolids as cell-free DNA, dead cells, viable cells, and mixtures of live and dead cells, followed by DNA extraction with and without PMA, and qPCR. The protocol was then used for Escherichia coli quantification in the three matrices, and results compared to plate counts. PMA-qPCR selectively detected viable cells, while inhibiting signals from cell-free DNA and DNA found in membrane-compromised cells. PMA-qPCR detected 0.5–1 log unit more viable E. coli cells in both primary solids and dewatered biosolids than plate counts. No viable E. coli was found in Lystek-treated biosolids. These data suggest PMA-qPCR may more accurately estimate pathogen cell numbers than traditional culture methods. 相似文献