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801.
NbOCl3 was obtained from a reaction of NbCl5 and Nb2O5 at 260?C. Contrary to the literature data, NbOCl3 crystallizes in the non‐centrosymmetric space group P&4macr;21m as determined by single‐crystal and powder X‐ray diffraction data (crystal: a = b = 1089.59(6) pm, c = 394.79(2) pm, Z = 4, R1 = 0.0229, wR2 = 0.0459, powder: a = b = 1086.36(6) pm, c = 393.65(2) pm). The niobium atoms are surrounded by distorted octahedra built of four chlorine atoms and two oxygen atoms in trans positions. Two such octahedra are edge‐bridged through shared chlorine atoms, forming dimers. These units are linked to each other by apical oxygen atoms forming one‐dimensional Nb2Cl6O2 chains parallel [001]. Contrary to the literature data two different Nb‐O distances are obtained. 相似文献
802.
Production and Decomposition of (NH4)[BF4] and H3N‐BF3 (NH4)[BF4] is produced as single crystals during the reaction of elemental boron and NH4HF2 (B : NH4HF2 = 1 : 2) and NH4F (B : NH4F = 1 : 4), respectively, in sealed copper ampoules at 300 °C. The crystal structure (baryte type, orthorhombic, Pnma, Z = 4) was redetermined at ambient temperature (a = 909.73(18), b = 569.77(10), c = 729.47(11) pm, Rall = 0.0361) and at 140 K (a = 887.3(2), b = 574.59(12), c = 717.10(12) pm, Rall = 0.0321). Isolated (NH4)+ and [BF4]— tetrahedra are the important building units. The thermal behaviour of (NH4)[BF4] was investigated under inert (Ar, N2) and reactive conditions (NH3) with the aid of DTA/TG and DSC measurements and with in‐situ X‐ray powder diffraction as well. Finally, (NH4)[BF4] is decomposed yielding NH3 and BF3, BN is not produced under the current conditions. Colourless single crystals of H3N‐BF3 were prepared directly from the components NH3 and BF3. The crystal structure was determined anew at 293 and 170 K (orthorhombic, Pbca, Z = 8, a = 815.12(10), b = 805.91(14), c = 929.03(12) pm, Rall = 0.0367; a = 807.26(13), b = 800.48(10), c = 924.31(11) pm, Rall = 0.0292, T = 170 K). The crystal structure contains isolated molecules H3N‐BF3 in staggered conformation with a B‐N distance of 158 pm. The thermal behaviour of H3N‐BF3 was studied likewise. 相似文献
803.
804.
Ternary Halides of the A3MX6 Type. VIII On the Crystal Structure of Li3InCl6 Colorless single crystals of Li3InCl6 are obtained from a 3 : 1 molar mixture of LiCl and InCl3 via Bridgman‐type crystal growth. The crystal structure (monoclinic, C2/m, Z = 2, a = 643.2(3), b = 1109.3(3), c = 639.8(3) pm, β = 109.8(1)° R1 = 0.0549, wR2 = 0.1364 (all data) may be derived from the AlCl3‐type of structure as was previously also found for the bromides Li3MBr6 (M = Sm–Lu, Y) and iodides Li3MI6 (M = Er–Yb, Y). 相似文献
805.
Glen B. Deacon Alex Gitlits Gerd Zelesny Dirk Stellfeldt Gerd Meyer 《无机化学与普通化学杂志》1999,625(5):764-772
The complexes [K(H2O)2LnL2] (Ln = La or Nd; L = 1,2‐benzenedisulfonate) and [K(H2O)Yb(H2O)4L2] were initially isolated fortuitously from attempts to prepare the corresponding Ln2L3 complexes from Ln2O3 and H2L in water. Indeed the bulk products from these reactions have the composition Ln2L3. Subsequently, deliberate syntheses by reacting equimolar amounts of Ln2L3 with K2L in water gave the complexes in good yield. X‐ray crystal structures of [K(H2O)2LnL2] (Ln = La or Nd) showed the complexes to be isostructural with a two dimensional polymeric network structure in which LnL2 units are linked into chains crosslinked by potassium ions. Each Ln is nine coordinate with solely sulfonate oxygen donor atoms. Between adjacent lanthanoid ions there are three different types of sulfonate bridges and two examples of each. Most noteworthy is highly unsymmetrical bridging through μ‐η2‐sulfonate oxygen atoms. Consequently, one Ln–O bond is ca. 0.5 Å longer than the other eight. Potassium is nine‐coordinate with seven sulfonate oxygen atoms and two aqua ligands, and surprisingly <K–O(sulfonate)> is much longer than <K–O(H2O)>. Pairs of potassium ions are linked by two μ‐η2‐sulfonate oxygen atoms, which are unsymmetrically bridging. The structure of [K(H2O)Yb(H2O)4L2] comprises discrete tetranuclear units containing two independent ytterbium ions, each coordinated by four water molecules and two chelating (via seven membered rings) disulfonate ligands, and two potassium ions, each coordinated by six sulfonate oxygen atoms and a water molecule. For each potassium, four of the coordinated sulfonate oxygen atoms are from sulfonate ligands bonded to one ytterbium atom and two from sulfonate ligands attached to the other ytterbium atom. In contrast to the Nd and La complexes, <K–O(sulfonate)> is shorter than <K–O(H2O)>. 相似文献
806.
(NH4)2[Mo6Cl14] · H2O ( 1 ) was prepared from reactions of MoCl2 in ethanol with aqueous NH4Cl solution. It crystallizes in the monoclinic space group I2/a (no. 15), Z = 4 with a = 912.3(1), b = 1491.2(2), c = 1724.8(2) pm, β = 92.25(1)°; R1 = 0.023 (based on F values) and wR2 = 0.059 (based on F2 values), for all measured X‐ray reflections. The structure of the cluster anion can be given as [(Mo6Cl)Cl]2– (i = inner, a = outer ligands). Thermal stability studies show that 1 loses crystal water followed by the loss of NH4Cl above 350 °C to yield MoCl2. The water‐free compound (NH4)2[Mo6Cl14] ( 2 ) was synthesized by solid state reaction of MoCl2 and NH4Cl in a sealed quartz ampoule at 270 °C. No single‐crystals could be obtained. Decompositions of 1 and 2 under nitrogen and argon exhibited the loss of NH4Cl at about 350 °C. Decomposition under NH3 resulted in the formation of MoN and Mo2N at 540 °C and 720 °C, respectively. 相似文献
807.
Ca9Cl8(BC2)2 was obtained by solid state reaction of a mixture of CaCl2, Ca, B and C. The structure was solved by single crystal X-ray structure determination. Ca9Cl8(BC2)2 crystallizes in the orthorhombic space group Cmcm (No. 63, a = 1162.91(8) pm, b = 1341.59(10) pm and c = 1208.62(9) pm, Z = 4). The most striking element of the title compound is the bent BC25– unit that is surrounded by a bicapped trigonal prismatic arrangement of calcium ions. 相似文献
808.
Olaf Reckeweg Andreas Baumann Hermann A. Mayer Jochen Glaser H.-Jürgen Meyer 《无机化学与普通化学杂志》1999,625(10):1686-1692
On the Coexistence of Tetragonal and Monoclinic CaC2: Structural and Spectroscopic Studies on Alkaline Earth Metal Acetylides, MC2 (M = Ca, Sr, Ba) The alkaline earth acetylides CaC2, SrC2 and BaC2 can be considered to occur in three polymorphic structures each. The monoclinic low-temperature form, the tetragonal form, and the cubic high-temperature form. No deviation from axial symmetry is obtained for the C22– ions in the tetragonal structure determinations, as confirmed by X-ray single-crystal structures and 13C MAS NMR studies. The CaC2 samples prepared by us were always a mixture of monoclinic and tetragonal phase. Their Raman spectra exhibited two distinct C2 streching vibrations. Problems arising from the coexistence of these two phases for the interpretation of 13C MAS NMR spectra are discussed. 相似文献
809.
J. N. Colcy R. De Martino S. Meyer 《International Journal of Satellite Communications and Networking》1997,15(3):129-134
This paper presents the results obtained in computer simulations and laboratory measurements of interference caused by FM-TV signals to band limited quasi synchronous code division multiple access (BLQS-CDMA) signals. Certain parameters, such as frequency spacing between wanted and interfering carriers and type of modulating TV signal (75 per cent saturated colour bar or saturated red field), were varied during the measurements and simulations, in order to study their influence on the amount of interference suffered by the BLQS-CDMA signal. Computer simulations were validated by hardware measurements, in order to have available an in-house software tool for future analyses. Protection ratio (PR) masks have been obtained and show that BLQS-CDMA is well adapted to a VSAT network operating in an FM-TV interference environment. © 1997 John Wiley & Sons, Ltd. 相似文献
810.
Harry Westfahl Jr Sérgio A. Lordano Luiz Bernd C. Meyer Florian Meneau 《Journal of synchrotron radiation》2017,24(3):566-575
In this work the coherence properties of the synchrotron radiation beam from an X‐ray undulator in a fourth‐generation storage ring are analyzed. A slightly focused X‐ray beam is simulated using a wavefront propagation through a non‐redundant array of slits and the mutual coherence function is directly obtained and compared with the Gaussian–Schell approximation. The numerical wave propagation and the approximate analytical approaches are shown to agree qualitatively, and it is also shown that, when the coherent fraction is selected by a finite aperture before the focusing element, even achromatic focusing systems like total reflection mirrors become slightly chromatic. This effect is also well accounted for in the Gaussian–Schell model. The wavefront propagation simulation through the non‐redundant array was repeated with an imperfect mirror demonstrating that, although the wavefront is distorted, its coherent length is practically unchanged. 相似文献