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951.
To put it bluntly, synchrotrons and storage rings were originally not intended to become light sources for synchrotron radiation (SR). If particle physicists had not driven this development for their own needs, we would not yet have these sources available at their present level of sophistication. In 1964, when the then-6 GeV synchrotron DESY at the newly founded Hamburg institution of the same name started operating, SR was considered at best a nuisance. Accelerating an electron to 6 GeV was accompanied by a loss of 9.35 GeV on its way due to this radiation, and later, at 7.5 GeV, the loss amounted to 22.8 GeV. How could it then happen that today all of the DESY storage rings and linear accelerators are devoted to SR? 相似文献
952.
The reaction of 1,2-diselenolato-1,2-dicarba-closo-dodecaborane(12) dianion [1,2-(1,2-C2B10H10)Se2]2− with HBBr2–SMe2 affords the dimethyl sulfide adduct of 4,5-[1,2-dicarba-closo-dodecaborano(12)]-1,3-diselena-2-borolane in good yield. The molecular structure was determined by X-ray diffraction, and the solution-state structure was established by NMR spectroscopy (1H, 11B, 13C, 77Se NMR). 11B and 77Se chemical shifts were reproduced by DFT calculations. Attempts were made to abstract dimethyl sulfide, and the parent donor-free compound could be detected in solution. The reactivity of the title compound was studied towards pyridine, Me3SnF, [Pt(PPh3)2(C2H4)], tert-Bu-OH, AlMe3 and AlH3-N(Et)Me2 as well as a hydroborating reagent. 相似文献
953.
Broszat Melanie Welle Christoph Wojnowski Monika Ernst Helena Spangenberg Bernd 《平面色谱法杂志一现代薄层色谱法》2010,23(3):193-197
JPC – Journal of Planar Chromatography – Modern TLC - Thin-layer chromatography is a rapid and reliable working method for quantification of mycotoxins which is suitable for checking EC... 相似文献
954.
Dipl.‐Chem. Christian Belger Dipl.‐Chem. N. Matthias Neisius Prof. Dr. Bernd Plietker 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(40):12214-12220
By using a readily available, air‐ and moisture‐stable dihydrido–Ru complex, a variety of Z olefins are accessible under transfer‐hydrogenation conditions with formic acid as the hydrogen source in excellent yields and Z/E selectivities. 相似文献
955.
Said El‐Kurdi Abdal‐Azim Al‐Terkawi Bernd M. Schmidt Anton Dimitrov Dr. Konrad Seppelt Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(2):595-599
WF6 reacts with phosphines R3P forming 1:1 compounds. With R=P(CH3)3 the coordination around the tungsten atom is capped trigonal prismatic, with R=P(CH3)2C6H5 the coordination is capped octahedral, as established by single‐crystal structure determinations: [(CH3)3P? WF6]: a=752.5(21), b=945.7(24), c=629.8(18) pm. β=110.36(13)°, space group Cm, Z=2; [(CH3)2(C6H5)P? WF6]: a=762.2(2), b=1123.5(2), c=2647.5(6) pm, space group Pbca, Z=8. [(CF3CH2)2N? WF5] reacts smoothly with P(C6H5)3 forming known P(C6H5)3(F)2 and [(CF3CH2)2N? WF4? P(C6H5)3], a stable, green, molecular species, identified among other methods with an crystal structure determination: a=914.9(1), b=956.0(1), c=1449.8(2) pm, α=7.642(4), β=81.648(3), γ=81.519°, space group P$\bar 1$ , Z=2. 相似文献
956.
Francesca Tancini Dr. Thomas Gottschalk Dr. W. Bernd Schweizer Dr. François Diederich Prof. Dr. Enrico Dalcanale Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(26):7813-7819
The capability of resorcinarenes to bind anions within the alkyl feet at the lower rim has been exploited as the starting point for developing a new cavitand able to engulf contact ion pairs of primary ammonium salts in chlorinated solvents with association constants (Kass) in the range of 103–104 M ?1. Methylene bridges were introduced into the upper rim to freeze the resorcinarene in the cone conformation with the four Hdown protons converging in the lower pocket, thereby maximizing the CH–anion interactions responsible for the anion binding. Four additional phosphate moieties were introduced into the lower rim in close proximity to the anionic site to provide hydrogen‐bonding‐acceptor P?O groups and promote cation complexation at the bottom of the cavitand. The binding ability of the synthesized ligands was analyzed by 1H NMR spectroscopy and, when possible, by isothermal titration calorimetry (ITC); the data were in agreement when complementary techniques were used. 相似文献
957.
Yulia Krupskaya Alexey Alfonsov Anupama Parameswaran Vladislav Kataev Dr. Rüdiger Klingeler Dr. Gunther Steinfeld Norman Beyer Mathias Gressenbuch Berthold Kersting Prof. Dr. Bernd Büchner Prof. Dr. 《Chemphyschem》2010,11(9):1961-1970
The ability of bridging thiophenolate groups (RS?) to transmit magnetic exchange interactions between paramagnetic NiII ions is examined. Specific attention is paid to complexes with large Ni? SR? Ni angles. For this purpose, dinuclear [Ni2L1(μ‐OAc)?I2][I5] ( 2 ) and trinuclear [Ni3L2(OAc)2][BPh4]2 ( 3 ), where H2L1 and H2L2 represent 24‐membered macrocyclic amino‐thiophenol ligands, are prepared and fully characterized by IR‐ and UV/Vis spectroscopy, X‐ray crystallography, static magnetization M measurements and high‐field electron spin resonance (HF‐ESR). The dinuclear complex 2 has a central N3Ni2(μ‐S)2(μ‐OAc)Ni2N3 core with a mean Ni? S? Ni angle of 92°. The macrocycle L2 supports a trinuclear complex 3 , with distorted octahedral N2O2S2 and N2O3S coordination environments for one central and two terminal NiII ions, respectively. The Ni? S? Ni angles are at 132.8° and 133.5°. We find that the variation of the bond angles has a very strong impact on the magnetic properties of the Ni complexes. In the case of the Ni2‐complex, temperature T and magnetic field B dependencies of M reveal a ferromagnetic coupling J=?29 cm?1 between two NiII ions (H=JS1S2). HF‐ESR measurements yield a negative axial magnetic anisotropy (D<0) which implies a bistable (easy axis) magnetic ground state. In contrast, for the Ni3‐complex we find an appreciable antiferromagnetic coupling J′=97 cm?1 between the NiII ions and a positive axial magnetic anisotropy (D>0) which implies an easy plane situation. 相似文献
958.
It is shown that the end group parameter, which describes the influence of the end group on retention, can be determined in RP chromatography from two chromatograms of a nonfunctional and a monofunctional sample, if a sufficient number of peaks with the same number of repeat units in each sample can be reasonably resolved and identified. The same procedure can also be applied for pairs of di‐ and monofunctional polymers. End group parameters have been determined in three different mobile phases: acetonitrile–water, acetone–water and methanol–water of different compositions. The temperature dependence of the interaction parameter of the repeat unit and the end group parameter has been found to be different, which allows a fine‐tuning of retention. 相似文献
959.
Bernd Küstner Magdalena Gellner Max Schütz Friedrich Schöppler Alexander Marx Prof. Dr. Philipp Ströbel Prof. Dr. Patrick Adam Dr. Carsten Schmuck Prof. Dr. Sebastian Schlücker Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(11):1950-1953
In a glass house : Silica‐encapsulated self‐assembled monolayers (SAMs) on tunable gold/silver nanoshells were used as labels for surface‐enhanced Raman scattering (SERS). This concept combines the spectroscopic advantages arising from maximum surface coverage and uniform molecular orientation of the Raman reporter molecules within the complete monolayer together with the high chemical and mechanical stability of the glass shell.
960.
Many problems in engineering, physics or other disciplines require an integrated treatment of coupled fields. These problems are characterised by a dynamic interaction among two or more physically or computationally distinct components, where the undergoing mathematical model commonly consists of a system of coupled PDE. Considerable progress has been made in the development of appropriate computational schemes to solve such coupled PDE systems. These attempts have resulted in various monolithic and decoupled numerical solution approaches. Despite the unconditional stability offered by implicit monolithic solution strategies, their use is not always recommended. The reason mainly lies in the complexity of the resulting system of equations and the limited flexibility in choosing appropriate time integrators for individual components. This has motivated the elaboration of tailored decoupled solution schemes, which follow the idea of splitting the problem into several sub-problems. But selection of the way of splitting can have a direct influence on the stability of the resulting solution algorithm. This necessitates the stability analysis of such an algorithm. Here, we introduce a general framework for the stability analysis of decoupled solution schemes. The approach is then used to study the stability behaviour of established decoupling strategies applied to typical volume- and surface-coupled problems, namely, coupled problems of thermoelasticity, porous media dynamics and structure-structure interaction. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献