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排序方式: 共有727条查询结果,搜索用时 31 毫秒
721.
Moritz Bernhardt Lukas Lätsch Boris Le Guennic Christophe Copéret 《Helvetica chimica acta》2023,106(11):e202300130
Industrial data storage application based on single-molecule magnets (SMMs) necessitates not only strong magnetic remanence at high temperatures but also requires the implementation of SMMs into a solid material to increase their durability and addressability. While the understanding of the relationship between the local structure of the metal and the resulting magnetic behavior is well understood in molecular systems, it remains challenging to establish a similar understanding for magnetic materials, especially for isolated lanthanide sites on surfaces. For instance, dispersed Dy(III) ions on silica prepared via surface organometallic chemistry exhibit slow magnetic relaxation at low temperatures, but the origin of these properties remains unclear. In this work, we modelled ten neutral complexes with coordination numbers (CN) between three and six ([Dy(OSiF3)3(O(SiF3)2)CN-3]) representing possible surface sites for dispersed Dy(III) ions and investigated their SMM potential via ab initio CASSCF/RASSI-SO calculations. Detailed analysis of the data shows the strong influence of the spatial position of the anionic ligands while the neutral ligands only play a minor role for the magnetic properties. In particular, a T-shape like orientation of the anionic ligands is predicted to exhibit good SMM properties making it a promising targeted coordination environment for molecular and surface-based SMMs. 相似文献
722.
723.
724.
Christoph Hahn Moritz Rauschenbach Holger Frey 《Angewandte Chemie (International ed. in English)》2023,62(28):e202302907
We report the first anionic polymerization of 1-vinylcyclohexene (VCH). This structure may be considered as an intermediate between dienes and styrene. The polymerization of this cyclic 1,2-disubstituted 1,3-diene proceeded quantitatively in cyclohexane at 25 °C with sec-butyllithium as an initiator. The obtained polymers have well-controlled molecular weights in the range of 5 to 142 kg mol−1, controlled by the molar ratio of monomer and initiator, with narrow molecular weight distributions (Đ<1.07–1.20). In situ 1H NMR kinetic characterization revealed a weak gradient structure for the copolymers of styrene and VCH, (rSty=2.55, rVCH=0.39). P(VCH) obtained in cyclohexane with sec-BuLi as an initiator showed both 1,4- and 3,4-incorporation mode (ratio: 64 : 36). It was demonstrated that the microstructure of the resulting P(VCH) can be altered by the addition of a modifier (THF), resulting in increasing 3,4-microstructure (up to 78 %) and elevated glass-transition temperature up to 89 °C. Thus, the monomer VCH polymerizes carbanionically like a diene, however leading to rigid polymers with high glass transition temperature, which provides interesting options for combination with other dienes to well-defined polymer architectures and materials. 相似文献
725.
Johannes Schlecht Bernd Moritz Steffen Kiessig Christian Neusüß 《Electrophoresis》2023,44(5-6):540-548
Imaged capillary isoelectric focusing (iCIEF) has emerged as an important technique for therapeutic monoclonal antibody (mAb) charge heterogeneity analysis in the biopharmaceutical context, providing imaged detection and quantitation by UV without a mobilization step. Besides quantitation, the characterization of separated charge variants ideally directly by online electrospray ionization–mass spectrometry (ESI–MS) is crucial to ensure product quality, safety, and efficacy. Straightforward direct iCIEF–MS coupling combining high separation efficiency and quantitative results of iCIEF with the characterization power of MS enables deep characterization of mAb charge variants. A short technical setup and optimized methodical parameters (30 nl/min mobilization rate, 2%–4% ampholyte concentration, 0.5–2 mg/ml sample concentration) allow successful mAb charge variant peak assignment from iCIEF to MS. Despite a loss of separation resolution during the transfer, separated intact mAb charge variants, including deamidation as well as major and minor glycoforms even from low abundant charge variants, could be characterized by online ESI–MS with high precision. The presented setup provides a large potential for mAb charge heterogeneity characterization in biopharmaceutical applications. 相似文献
726.
Kathrin Kunowa Sebastian Schmidt-Lehr Werner Pauer Hans-Ulrich Moritz Christian Schwede 《Macromolecular Symposia》2007,259(1):32-41
Summary: In this article particular attention is paid to processes of mixing fluids with different viscosities relevant for polymerization where the reaction is fast and mixing is the limiting factor. Apart from this, mixing fluids with different viscosities is still one of the challenging tasks in industrial chemistry. Therefore, the characterization of mixing elements is another important topic. Two different multiple chemical reactions, based on the principle of competitive-parallel reactions, were used and compared to investigate (micro)mixing efficiency in polymerization reactors. The well-known Villermaux-Dushman reaction and the third Bourne reaction were applied. The observed product distribution represents the quantity of segregation of the fluid which gives in turn information about the dependency on certain parameters like type and speed of stirrer, dosing period, feed position, and the viscosity of the fluid. The results from semibatch and continuous stirred tank reactors and two different stirrers, Rushton and INTERMIG® impeller, are discussed. 相似文献
727.
Sabine Beuermann Michael Buback Moritz Gadermann Michael Jürgens Fabian Günzler 《Macromolecular Symposia》2004,206(1):229-240
Free-radical terpolymerizations of styrene, methyl methacrylate, and glycidyl methacrylate were carried out in a tubular reactor in the presence of 20 wt.% CO2 at temperatures between 120 and 180°C and pressures of 300 and 350 bar. The number average molecular weights, MN, were mostly between 2000 and 3000 g·mol−1 and polydispersity indices around 2. In part of the experiments molecular weights were controlled by n-dodecyl mercaptan serving as the chain-transfer agent. PREDICI modeling indicates that the targeted molecular weights of MN∼2500 g·mol−1 and polydispersities around 2 may also be reached by using an initiator cocktail, a mixture of two initiators with significantly different decomposition rate coefficients. The predictions are confirmed experimentally. 相似文献