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941.
Falko Wachholz Jan Gimsa Heiko Duwensee Harald Grabow Peter Gründler Gerd‐Uwe Flechsig 《Electroanalysis》2007,19(5):535-540
We describe a novel instrument and electrical circuit for sensitive electrochemical measurements at simultaneous direct electrode heating. The new measuring principle can be applied to working electrodes of various designs featuring two end contacts. In our experiments, the contacts were connected to a 100 kHz AC heating power supply and the potentiostat via the new inductor bridge circuit. A compact heating‐generator housing contains all components necessary for sine wave generation as well as amplification and transformation of the heating power. The new arrangement yields high temperature cyclovoltammetric signals for the [Fe(CN)6]3?/4? redox system with a noise level superior to the earlier symmetrically branched wire electrode designs. Noise and disturbances are dramatically suppressed especially for high resistance electrodes such as glassy carbon electrodes. Without a center contact, the working electrode design is greatly simplified. This opens new opportunities for the design of a great variety of heated electrodes that may be arranged in arrays or consist of materials with relatively high resistivity such as carbon and conducting polymers. 相似文献
942.
碳笼烯C_(60)及C_(70)等的发现启示人们去探索合成更多的新型封闭型碳烯化合物,可以设想,由六元碳环构成的石墨层平面可以卷成顶和底为p元环、侧面为紧接着顶底的p个五元环、中间k层p个六元环围成的碳管笼烯C_n(n=2p(k+2)),其结构见图1。笼烯的每个C原子都与3个相邻的C原子成键,并有一个与笼面垂直的单电子占据轨道,可以相互作用构成笼面共轭大π键。我们在 相似文献
943.
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945.
分析了聚酯纤维机织物在背后有空气层时的吸声频谱规律以及测试时材料对管内驻波的影响。将传统吸声材料的Zwikker和Costen理论、毛细管吸声理论、微穿孔板吸声理论以及穿孔板共振吸声理论应用于材料特性分析,发现Zwikker和Costen理论可以定性的给出与实测情况相吻合的材料吸声系数随频率的变化规律。穿孔板共振吸声理论可以推导出与实测情况很接近的材料第一吸声峰值频率。另外,毛细管吸声理论和微穿孔板吸声理论不适合于背后有空气层时聚酯纤维织物的吸声情况。 相似文献
946.
In this paper a large class of multivariate densities and frequency functions, including the multivariate Poisson distribution and the compound multivariate Poisson distribution, are shown to have the decreasing in transposition property introduced by Hollander, Proschan, and Sethuraman (1977, Ann. Statist.5, 722–733). Sample applications in ecology and reliability are given; other applications to cumulation of damage and component down times are mentioned, but are not presented in detail. 相似文献
947.
Masakazu Kobayashi Takuya Honda Atsushi Kanzawa 《Plasma Chemistry and Plasma Processing》1984,4(1):43-57
The momentum and energy transfer phenomena with large temperature difference were investigated experimentally and theoretically, using an argon atmospheric thermal plasma. The plasma was generated by an arc discharge, 4–6 kW, and flowed into a water-cooled copper tube for static pressure measurements and into a copper block with the same size hole (8 mm i.d.) for measuring heat fluxes using a transient method. The argon flow rate was 2.77–8.31×10–4 kg/s. The static pressure of the plasma flow shows a different variation from that of an ordinary flow and does not decrease monotonically. The axial distributions of the numerical calculations are in fair agreement with those of the experiments, and it is concluded that the contributions of recombination and of physical properties play important roles in the behavior of the confined thermal plasma flow. 相似文献
948.
建立用气袋法收集整册印刷品释放的挥发性有机化合物,热解析-气相色谱法检测总挥发性有机化合物(TVOC)的方法。将印刷品样品置入充满高纯氮气的密封PVF采样袋中,在35℃下放置12 h后,用采样器串联Tenax-TA采样管和采样袋,让袋内气体通过采样管,样品释放出的有机化合物被吸附到采样管的吸附剂上。用热解析-气相色谱法测试采样管中挥发性有机化合物的含量,其中苯、甲苯、邻二甲苯、间二甲苯、对二甲苯、乙苯、乙酸丁酯、苯乙烯和正十一烷按外标法定量,其它物质按甲苯标准曲线定量。该方法的加标回收率为74.4%~91.1%,测定结果的相对标准偏差不大于10%(n=9)。该方法的样品采集更贴近印刷品的实际生活场景,可以为评价印刷品挥发性有机物释放对人体健康的影响提供数据基础,为相关评价提供新思路。 相似文献
949.
The method of absolute calibration of the TALIF signal of atomic nitrogen by NO titration in the afterglow of a flow tube reactor has been analyzed using TALIF and emission spectroscopy. An increase in production of atomic nitrogen at titration beginning and an asymmetric parabolic curve for emission of NObands have been observed. Of three possible explanations of these effects the model of wall recombination was favored: it led to fitted wall recombination coefficients referring to wall loss factors, which where in the same dimension as literature values and was able to simulate a hysteresis effect, which has been observed experimentally. According to the observations the titration end point cannot be used to determine the atomic nitrogen density in the afterglow before any NO has been added into the system as the titer produces part of this density itself. But for absolute calibration purposes referring to the wall recombination model the linear decrease of the TALIF signal with increasing titer concentration can still be used as straight line of calibration. Only a correction of the calibration factor by a factor of 0.59 for 5 mbar titrations has to be taken into account as the titer shows wall interaction not only in a catalytic way, but is partly consumed. 相似文献
950.
The paper reports the results of an experimental study on pressure drop during horizontal flow boiling of refrigerants R22, R507, R404A, R134a, R407C and R410A. The test section is a smooth, horizontal, stainless steel tube (6 mm I.D., 6 m length) uniformly heated by Joule effect. The experimental tests are carried out at an almost constant evaporating pressure of 7.0 bar varying the mass flow rate in the range 280–1,080 kg/m2 s. The experimental comparison clearly shown that the pressure drop of R22 is significantly higher as compared to all the other fluids. The results are compared against well-known pressure drop prediction methods. The available correlations can be used for both pure fluids and mixtures with no corrective factors, provided the mixture properties are evaluated at local compositions. The Chawla friction correlation is the best-fitting of our experimental data in combination with the heterogeneous momentum pressure drop model on the basis of the Rouhani-Axelsson void fraction correlation. 相似文献