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991.
Reaction of Ph3GeLi with [Et4N][HFe3(CO)11] affords the new carbonylferrate salt [Et4N][Ph3GeFe(CO)4] and the same reaction provides an alternative route to the known silicon and tin analogs. Protonation of [Et4N][Ph3GeFe(CO)4] with HCl in ether-THF forms the air-sensitive, thermally rather unstable cis-Ph3GeFeH(CO)4. The latter protonates chloride ions in dichloromethane. 相似文献
992.
Pulse radiolysis of tetrahydrofuran (THF) and solutions of NaAIH4 in THF shows the formation of solvated electrons (e?s), their conversion to Na+-e?s) ion-pairs and ultimately the alkali metal anion (Na?). 相似文献
993.
T. Wanjun L. Yuwen Z. Hen W. Zhiyong W. Cunxin 《Journal of Thermal Analysis and Calorimetry》2003,74(1):309-315
A new approximate formula for temperature integral is proposed. The linear dependence of the new fomula on x has been established. Combining this linear dependence and integration-by-parts, new equation for the evaluation of kinetic
parameters has been obtained from the above dependence. The validity of this equation has been tested with data from numerical
calculating. And its deviation from the values calculated by Simpson's numerical integrating was discussed. Compared with
several published approximate formulae, this new one is much superior to all other approximations and is the most suitable
solution for the evaluation of kinetic parameters from TG experiments.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
994.
J. Bublitz A. Christophersen W. Schade 《Fresenius' Journal of Analytical Chemistry》1996,355(5-6):684-686
Time-resolved laser-induced fluorescence spectroscopy and fiber optics are applied for the detection of aromatic hydrocarbons in oil contaminated water and soil samples. Time-integrated data accumulation of fluorescence intensities in an early and in a late time window with respect to the exciting laser pulse simplifies the method in such a way that it becomes very attractive for practical applications. For ultraviolet laser excitation at 337 nm and recording fluorescence signals at 400 nm, typical detection limits of the present set-up are 0.5 mg engine oil/L in water and 5 mg engine oil/kg in soil. A discrimination between BTXE-aromatics and PAHs in oil polluted soil or water samples is possible, when more than one laser wavelength in the ultraviolet is used for the excitation. The possibilities for a thermal discrimination between different aromatics are also discussed. 相似文献
995.
B. Delakowitz G. Meinrath W. Spiegel 《Journal of Radioanalytical and Nuclear Chemistry》1996,213(2):109-125
A comparative review of mineral-specific radionuclide sorption databases created for performance assessment and reported in both the open literature and grey literature (e.g. technical reports) has in part shown poor quality of documentation describing the database selection procedures. Inadeguate information is available on the chemical species of the radionuclide under consideration and the laboratory conditions for determining Kd-values. Sorption data derived from literature are neither comparable nor generally applicable due to the wide range in the composition of the aqueous and the solid phases applied in migration experiments. Subsequently, standardized characterization and determination procedures are needed. To improve the reliability of a mathematical model for the prediction of radionuclide sorption on cementitious and ash-type binder materials, determination of mineral-specific sorption coefficients is indispensable. 相似文献
996.
Summary The use of non-segmented flow, post-column reaction detection is evaluated for use with miniaturized HPLC. Non-segmented open-tubular reactors with internal diameters 0.1 mm to 0.25 mm and packed-bed reactors with internal diameters of 1 mm, filled with 5 and 10 m particles are evaluated theoretically and experimentally with respect to band broadening and pressure drop characteristics. An integrated system consisting of miniaturized HPLC (1 mm i. d.) columns and compatible hardware is described. An example of the separation of catecholamines is given. 相似文献
997.
W.W. Wendlandt 《Thermochimica Acta》1977,21(2):291-294
A convenient AC electrical conductivity apparatus is described. The sample, which is in the form of a pressed disk, is placed between two platinum plates located in a small cylindrical furnace. A 1–10V, 100 Hz potential is applied to the sample and the resulting current, in μA, is recorded on an X-Y recorder as a function of temperature. An EC curve of the dehydration of BaCl2 - 2H2O to BaCl2 - H2O is presented to illustrate the operation of the apparatus. 相似文献
998.
Three new titrants have been evaluated for the precipitation titration of perchlorate: cetylpyridinum chloride (CPC), cetyltrimethylammonium chloride (CETAC), and benzyldimethyltetradecylammonium chloride (BDTAC). CETAC yielded the highest precision and largest potentiometric break, closely followed by CPC. BDTAC produced considerably lower precision and smaller breaks. Fluoroborate was similarly determined with CPC and CETAC. Again CETAC yielded the highest precision and largest potentiometric break. Titrations were monitored with a fluoroborate ion-selective indicator electrode and a double-junction reference electrode. The perchlorate and nitrate ISEs may also be used for monitoring the emf. Both titrants are considerably less expensive than equivalent amounts of the commonly used tetraphenylarsonium chloride titrant. 相似文献
999.
The problem of collinear scattering of an atom from a homonuclear diatomic molecule is formulated in terms of a first-order nonlinear matrix differential equation for the variable coefficient of reflection. For a homonuclear molecule when the target Hamiltonian is invariant under the parity transformation, only transitions between even states or odd states are possible. This selection rule reduces the number of open or closed channels that contribute to the reflection and transmission coefficients. But for numerical calculation, under the conditions of the problem, one can approximate the target Hamiltonian by the Hamiltonian of a displaced harmonic oscillator. In this approximation, the reflectional symmetry of the Hamiltonian is not preserved and transitions between any two levels of the target are possible. To simplify the problem further, the interaction between the projectile and the target is assumed to be a sum of two Gaussian terms. For this combination of the potentials the many-channel interaction can be expressed analytically. By fitting the Lennard–Jones potential with a sum of two Gaussian potentials and solving the matrix differential equation, transition probabilities are obtained for the He? H2 collision. The numerical results are compared with the results found by Secrest and Johnson, and by Clark and Dickinson. 相似文献
1000.
The potential of a charge distribution due to a lattice of point charges may be evaluated by the classical multipole expansion method. The leading terms in the resultant expressions are just those used in some of our previous calculations [1–3]. In addition, for cases where the leading terms vanish because of the effect of orthogonality of the basis functions upon the Mulliken expansion (this being especially serious in the case of a one-centre charge distribution), we have derived the first nonvanishing term, involving |r|. In other cases it may be necessary to proceed to still higher multipole terms before a non-zero contribution is obtained. The entire procedure is formulated in such a way that it can be easily applied to LCAO-MO calculations for polyatomic ions in ionic lattices. 相似文献