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101.
Anne van den Wittenboer Thomas Schmidt Pia Müller Marion B. Ansorge-Schumacher Lasse Greiner Dr. 《Biotechnology journal》2009,4(1):44-50
Biphasic reaction media are extending the scope of technical biocatalysis. Thorough investigation of the factors affecting catalyst performance under these conditions is of key importance for the successful implementation of catalytic processes. Here, we present a reactor setup suitable for comprehensive systematic characterization and optimization of biocatalyzed reactions in biphasic systems with distinct phases. It is distinguished by small volumes allowing reproducible experimentation with minimum amounts of solvent and catalyst. The interfacial area is kept constant and independent stirring of both phases is allowed in order to minimize superimposing effects. Evaporation of low-volatile organic solvents is prevented by use of airtight construction. The broad applicability of this mini-reactor is demonstrated with regard to determination of mass transfer, enzyme productivity, and enzyme stability in both batch and continuous mode. 相似文献
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106.
Greiner C Hiemke C Bader W Haen E 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2007,848(2):391-394
We established a method for automated quantitative analysis of (es-)citalopram and desmethyl(es-)citalopram in serum using column-switching high performance liquid chromatography (HPLC). For sample clean-up serum was injected onto a LiChrospher CN 20 microm precolumn using 8% acetonitrile in deionized water. Drugs were eluted by back-flush flow onto the analytical column (LiChrospher CN 5 microm) at a flow rate of 1.5 ml/min with phosphate buffer 8 mmol/l pH 6.4/acetonitrile (50/50, v/v). Haloperidol was used as internal standard. Analytes were detected by ultraviolet spectrophotometry at 210 nm. Detection limit of (es-)citalopram was 6 ng/ml. The method was found to be suitable for therapeutic drug monitoring of patients treated with citalopram or escitalopram. 相似文献
107.
Using a combination of High-Performance Ion Chromatography analysis and kinetic studies, the pathway of myo-inositol hexakisphosphate dephosphorylation by a phytase from a Malaysian waste-water bacterium was established. The data
demonstrate that the phytase preferably dephosphorylates myo-inositol hexakisphosphate in a stereospecific way by sequential removal of phosphate groups via D-I(1,2,3,4,5)P5, D-I(2,3,4,5)P4, D-I(2,3,4)P3, D-I(2,3)P2 to finally I(2)P. It was estimated that more than 90% of phytate hydrolysis occurs via D-I(1,2,3,4,5)P5. Thus, the phytase from the Malaysian waste-water bacterium has to be considered a 6-phytase (E.C. 3.1.3.26). A second pathway
of minor importance could be proposed which is in accordance with the results obtained from analysis of the dephosphorylation
products formed by the action of the phytase under investigation on myo-inositol hexakisphosphate. It proceeds via D/L-I(1,2,4,5,6)P5, D/L-I(1,2,4,5)P4, D/L-I(1,2,4)P3, D/L-I(2,4)P2 to finally I(2)P. 相似文献
108.
Humanized mice in translational biomedical research 总被引:1,自引:0,他引:1
The culmination of decades of research on humanized mice is leading to advances in our understanding of human haematopoiesis, innate and adaptive immunity, autoimmunity, infectious diseases, cancer biology and regenerative medicine. In this Review, we discuss the development of these new generations of humanized mice, how they will facilitate translational research in several biomedical disciplines and approaches to overcome the remaining limitations of these models. 相似文献
109.
Efficient and Stable TiO2:Pt–Cu(In,Ga)Se2 Composite Photoelectrodes for Visible Light Driven Hydrogen Evolution 下载免费PDF全文
Anahita Azarpira Michael Lublow Alexander Steigert Peter Bogdanoff Dieter Greiner Christian A. Kaufmann Martin Krüger Ullrich Gernert Roel van de Krol Anna Fischer Thomas Schedel‐Niedrig 《Liver Transplantation》2015,5(12)
Novel thin film composite photocathodes based on device‐grade Cu(In,Ga)Se2 chalcopyrite thin film absorbers and transparent conductive oxide Pt‐implemented TiO2 layers on top are presented for an efficient and stable solar‐driven hydrogen evolution. Thin films of phase‐pure anatase TiO2 are implemented with varying Pt‐concentrations in order to optimize simultaneously i) conductivity of the films, ii) electrocatalytic activity, and iii) light‐guidance toward the chalcopyrite. Thereby, high incident‐photon‐to‐current‐efficiencies of more than 80% can be achieved over the full visible light range. In acidic electrolyte (pH 0.3), the most efficient Pt‐implemented TiO2–Cu(In,Ga)Se2 composite electrodes reveal i) photocurrent densities up to 38 mA cm?2 in the saturation region (?0.4 V RHE, reversible hydrogen electrode), ii) 15 mA cm?2 at the thermodynamic potential for H2‐evolution (0 V RHE), and iii) an anodic onset potential shift for the hydrogen evolution (+0.23 V RHE). It is shown that the gradual increase of the Pt‐concentration within the TiO2 layers passes through an efficiency‐ and stability‐maximum of the device (5 vol% of Pt precursor solution). At this maximum, optimized light‐incoupling into the device‐grade chalcopyrite light‐absorber as well as electron conductance properties within the surface layer are achieved while no degradation are observed over more than 24 h of operation. 相似文献
110.
Wintermantel TM Campbell RE Porteous R Bock D Gröne HJ Todman MG Korach KS Greiner E Pérez CA Schütz G Herbison AE 《Neuron》2006,52(2):271-280
The mechanisms through which estrogen regulates gonadotropin-releasing hormone (GnRH) neurons to control mammalian ovulation are unknown. We found that estrogen positive feedback to generate the preovulatory gonadotropin surge was normal in estrogen receptor beta knockout (ERbeta) mutant mice, but absent in ERalpha mutant mice. An ERalpha-selective compound was sufficient to generate positive feedback in wild-type mice. As GnRH neurons do not express ERalpha, estrogen positive feedback upon GnRH neurons must be indirect in nature. To establish the cell type responsible, we generated a neuron-specific ERalpha mutant mouse line. These mice failed to exhibit estrogen positive feedback, demonstrating that neurons expressing ERalpha are critical. We then used a GnRH neuron-specific Pseudorabies virus (PRV) tracing approach to show that the ERalpha-expressing neurons innervating GnRH neurons are located within rostral periventricular regions of the hypothalamus. These studies demonstrate that ovulation is driven by estrogen actions upon ERalpha-expressing neuronal afferents to GnRH neurons. 相似文献