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91.
制备了一个苯甲酰腙化合物N'-(2-羟基-5-甲氧基苯甲基)-4-二甲氨基苯甲酰肼(H2L)。利用H2L、乙酰氧肟酸(HAHA)和VO(acac)2在甲醇中反应得到了配合物[VOL(AHA)]。通过元素分析、红外和紫外光谱,以及单晶X-射线衍射对H2L和其配合物进行了表征。苯甲酰腙配体作为二价阴离子,利用其酚羟基氧原子、亚胺基氮原子、以及烯醇氧原子与V原子进行配位。乙酰氧肟酸配体利用其羰基氧原子和去质子化的羟基氧原子进行配位。配合物中的V原子为八面体配位构型。测试了H2L、HAHA和钒配合物的脲酶抑制活性。在浓度为100μmol·L-1时,钒配合物对幽门螺旋杆菌脲酶的抑制率为63%,其IC50值为45μmol·L-1。还利用分子对接技术研究了配合物分子与脲酶的作用方式。 相似文献
92.
Pressure assisted capillary electrophoresis in capillaries with internal diameters of 10 μm was found possible without significant penalty in terms of separation efficiency and sensitivity when using contactless conductivity detection. A sequential injection analysis manifold consisting of a syringe pump and valves was used to impose a hydrodynamic flow in the separation of some inorganic as well as organic cations. It is demonstrated that the approach may be used to optimize analysis time by superimposing a hydrodynamic flow parallel to the electrokinetic motion. It is also possible to improve the separation by using the forced flow to maintain the analytes in the capillary, and thus the separation field, for longer times. The use of the syringe pump allows flexible and precise control of the pressure, so that it is possible to impose pressure steps during the separation. The use of this was demonstrated for the speeding up of late peaks, or forcing repeated passage of the sample plug through the capillary in order to increase separation. 相似文献
93.
A HPLC-detector has been designed which employs light-emitting diodes in the deep-UV-range below 300 nm as wavelength specific radiation sources and special UV-photodiodes for measuring the signal. A monochromator is therefore not needed. The design features a beam splitter and a reference photodiode, precision mechanics for adjustment of the light beams and electronics for stabilization of the LED-current. The processing of the photodiode currents is carried out with a high performance log-ratio amplifier which allows direct absorbance measurements. The optical and electronic performance of the detector was characterised and high precision over several absorbance units was obtained. Testing of analytical separation methods in isocratic as well as gradient modes employing UV-detection at 255 and 280 nm showed a very similar performance to a commercial photodiode-array detector used in the fixed wavelength mode in terms of linearity, precision and detection limits. The chief advantages of the new device are small size, low power consumption, and low cost. 相似文献
94.
Li X Shew CY Liu Y Pynn R Liu E Herwig KW Smith GS Robertson JL Chen WR 《The Journal of chemical physics》2011,134(9):094504
Spin-echo small angle neutron scattering (SESANS) provides a new experimental tool for structural investigation. Due to the action of spin-echo encoding, SESANS measures a spatial correlation function in real space, as opposed to the structure factor S(Q), I(Q), in momentum (Q) space measured by conventional small angle neutron scattering. To establish the usefulness of SESANS in structural characterization, particularly for interacting colloidal suspensions, we have previously conducted a theoretical study of the SESANS correlation functions for model systems consisting of particles with uniform density profiles [X. Li, C.-Y. Shew, Y. Liu, R. Pynn, E. Liu, K. W. Herwig, G. S. Smith, J. L. Robertson, and W.-R. Chen J. Chem. Phys. 132, 174509 (2010)]. Within the same framework, we explore in the present paper the prospect of using SESANS to investigate the structural characteristics of colloidal systems consisting of particles with nonuniform intraparticle mass distribution. As an example, a Gaussian model of interacting soft colloids is used to investigate the manifestation of structural softness in a SESANS measurement. The exploration shows a characteristically different SESANS correlation function for interacting soft colloids, in comparison to that of a uniform hard sphere system. The difference arises from the Abel transform imbedded in the mathematical formalism bridging the SESANS spectra and the spatial autocorrelation function. 相似文献
95.
Priority queueing systems come natural when customers with diversified delay requirements have to wait to get service. The
customers that cannot tolerate but small delays get service priority over customers which are less delay-sensitive. In this
contribution, we analyze a discrete-time two-class preemptive repeat identical priority queue with infinite buffer space and
generally distributed service times. Newly arriving high-priority customers interrupt the on-going service of a low-priority
customer. After all high-priority customers have left the system, the interrupted service of the low-priority customer has
to be repeated completely. By means of a probability generating functions approach, we analyze the system content and the
delay of both types of customers. Performance measures (such as means and variances) are calculated and the impact of the
priority scheduling is discussed by means of some numerical examples. 相似文献
96.
Dielectric measurements on samples consisting of banana-shaped molecules with a polymorphism I/SmCPA/B7 have been performed for the first time. The dielectric increment for the reorientation of the molecules about the long axis, and the corresponding relaxation time, surprisingly decrease at the SmCPA/B7 transition. This effect is discussed in terms of the undulated structure which partially destroys the ferroelectric short range order. Decreasing temperature gives an even stronger hindrance for this reorientation and could explain controversial results obtained in the B7 phases of different samples. At lower temperatures a further mesophase was detected. This was additionally observed by calorimetric and atomic force microscopy methods. 相似文献
97.
98.
We consider a queueing system with disruptive and non-disruptive server interruptions. Both disruptive and non-disruptive interruptions may start when there is a customer in service. The customer repeats its service after a disruptive interruption, and continues its service after a non-disruptive interruption. Using a transform approach, we obtain various performance measures such as the moments of the queue content and waiting times. We illustrate our approach by means of some numerical examples. 相似文献
99.
M. Fischer H.-J. Güntherodt E. Hauser H.U. Künzl M. Liard R. Müller 《Physics letters. A》1975,55(7):423-425
The electrical resistivity, the Hall coefficient and the magnetic susceptibility of amorphous alloys (Metglass 2826A, Allied Chemical) have been measured above room temperature. The experimental data show strong similarities with liquid alloys. 相似文献
100.
The absolute differential cross sections for the elastic scattering of 0.511 MeV gamma rays were measured in the angular range 0.5? to 10? for the elements withZ=72 toZ=92. The experimental method, employing annihilation radiation in coincidence, permits the investigation at very small momentum transfer. In general the results obtained are in very good agreement with the predictionZ 2 r 0 2 for the differential Rayleigh cross section atθ=0? and with the form factor theory, using Hartree-Fock-Slater wave functions, for the investigated angular range. However, for the elements lead, bismuth and thorium we found marked deviations from the form factor predictions, occurring at very small scattering angles. This is attributed to an outer atomic charge distribution different from the other investigated elements, which is also indicated by considerably greater metallic radii. Also effects due to the crystalline structure cannot be excluded. — Further, an elastic, resonance-like andZ-dependent scattering effect by bound electrons is discussed which is due to the formation of an intermediate, bound positronium state by electron-positron pairs. 相似文献