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991.
Jian-Tao Zhang Xiang-Li Liu Alfred Fahr Klaus D. Jandt 《Colloid and polymer science》2008,286(10):1209-1213
In this study, a new method was developed to prepare temperature-sensitive poly(N-isopropylacrylamide) microgels by free radical precipitation polymerization using siloxane coupling agent as the new crosslinker.
Ammonium persulfate acted as the initiator for the radical copolymerization as well as the catalyst for the hydrolysis/condensation
of the siloxane groups. The particle diameter and polydispersity of the microgels were measured by photon correlation spectroscopy
and the results display that the microgels are monodisperse. The microgels exhibit temperature sensitivity and the phase transition
temperature is approximately 31 °C. Furthermore, the diameter of the microgels changes upon heating and cooling processes.
These were observed to be reversible. The novel crosslinking method described herein is the condensation of siloxane groups,
which is totally different from the traditional double-vinyl crosslinkers. This innovative approach offers an alternative
path to prepare functional core–shell particles and inorganic/organic hybrid materials. 相似文献
992.
Alfred Karpfen Elisabeth Liedl Walter Snor Helmut Viernstein Petra Weiss-Greiler Peter Wolschann 《Monatshefte für Chemie / Chemical Monthly》2008,139(4):363-371
Conformations of α-, β-, and γ-CDs under anhydrous conditions in the gas phase were investigated by a density functional method, B3LYP/6-31G(d,p). These calculations resulted in several symmetric conformations with different energies. The lowest energy conformations contain two rings of homodromic hydrogen bonds and are referred to “one-gate-closed” conformations. Different orientations of hydrogen bonds lead to four minima. Other conformational minima were found for “open” conformations which correspond to some extent to experimentally determined structures. 相似文献
993.
Yan B Tao J Pang C Zheng Z Shen Z Huan CH Yu T 《Langmuir : the ACS journal of surfaces and colloids》2008,24(19):10569-10571
We describe a simple and robust approach to fabricating an alpha-Fe2O3 switchable surface. The hydrophobicity of alpha-Fe2O3 nanostructures was observed for the first time. A remarkable surface wettability transition can be easily achieved by ultraviolet (UV) illumination. The distinctive properties of surface defects are disclosed by X-ray photoelectron spectroscopy (XPS) analysis. The nanoscale adsorption and photocatalytic properties of Fe2+ defects account for the highly amphiphilic character of the surfaces. We believe that the experiment will further the molecular-scale understanding and manipulation of the wetting behavior on smart devices. 相似文献
994.
995.
996.
Meister A Drescher S Mey I Wahab M Graf G Garamus VM Hause G Mögel HJ Janshoff A Dobner B Blume A 《The journal of physical chemistry. B》2008,112(15):4506-4511
Bipolar phospholipids (bolalipids) represent an exciting class of amphiphilic molecules as they self-assemble in water to distinct structures of nanoscopic dimensions. Reported here are structural details of helical nanofibers, composed of achiral, symmetrical single-chain bolalipids with phosphocholine headgroups. These nanofibers are used as template for the fixation of gold nanoparticles (AuNPs) without prior functionalization. This realization of a metal array on bolalipid nanofibers is one of the rare examples of one-dimensional AuNP arrangements in solution. The loading and the heat of binding of AuNPs are determined applying transmission electron microscopy and isothermal titration calorimetry. 相似文献
997.
998.
We propose a reversed phase HPLC (RP-HPLC) with an alkaline-resistant silica-based stationary phase, XBridge Shield RP(18), for the determination of the lipophilicity of drugs with diverse chemical nature ranging from acidic to basic. A set of 40 model compounds with well-defined solvatochromic parameters was selected to allow a broad distribution of structural properties. The chromatographic results showed that the lipophilicity index log k(w) obtained with XBridge Shield RP(18) was well correlated with experimental log P(oct) values (r(2)=0.96). Linear solvation free-energy relationship (LSER) analyses revealed that the retention mechanism of the stationary phase and 1-octanol/water partitioning were controlled by almost the same balance of intermolecular forces (hydrophobicity as expressed by the van der Waals volume V(w), H-bond acceptor basicity beta, and dipolarity/polarizability pi*). The results showed that XBridge Shield RP(18) phase overcomes the shortcomings of the silica-based stationary phases, the application of which to lipophilicity measurements had been limited to neutral and acidic compounds. 相似文献
999.
Extended structure design with simple molybdenum oxide building blocks and urea as a directing agent
Veen SJ Roy S Filinchuk Y Chernyshov D Petukhov AV Versluijs-Helder M Broersma A Soulimani F Visser T Kegel WK 《Inorganic chemistry》2008,47(15):6863-6866
We report here a simple one-pot directed synthesis of an oxomolybdate urea composite in which elementary molybdenum oxide building blocks are linked together with the aid of urea. This type of directed material design resulted in large rod-like crystals of an inorganic-organic hybrid extended structure of {MoO 3(NH 2-CO-NH 2)} infinity consisting of right- and left-handed helical units. In the crystal structure urea acts both as a glue that links the inorganic molybdenum units into a helix and as a supramolecular linker for the stabilization of the crystal structure as a whole. This type of molecular topology resulted in an unexpectedly high thermal stability. 相似文献
1000.
After many unsuccessful efforts, the structure of solid CD4 III finally has been solved. In this paper, we examine if the known tunneling spectra are consistent with the orientational potentials at the two sites with different symmetries. To this end, we study the rotational kinetic energy of the molecules, construct appropriate pocket states for the tunneling problem, and set up a model potential. Approximate energy levels are obtained from the Ritz variational principle. The agreement between the experimentally determined tunneling frequencies and the calculations is rather good, corroborating the findings of the structural analysis. A continuation of this paper will deal with the partly deuterated methanes. 相似文献