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71.
Stavros?LalasEmail author Vassilis?Dourtoglou 《Journal of the American Oil Chemists' Society》2003,80(6):579-583
The effect of using a rosemary extract on the stability of oil used for frying potato chips has been evaluated. Sliced potatoes
were fried intermittently in soybean oil containing a natural extract from rosemary. The conditions used for frying were 185°C
for 90 s. Two separate experiments, with and without replenishment of oil, were carried out. Oil samples were taken each day,
not only from the frying pans but also by extraction with hexane from the chips. Changes in the induction period of the oil
samples (Rancimat method) were determined. The induction period decreased as frying progressed. The reduction in the induction
period was higher in the oil free of rosemary extract, and the chips were much darker in color. The oil containing the extract
showed greater antioxidant activity, and reduced darkening and rancidity of the oil. Potato chips fried in the oil with added
rosemary extract were more acceptable than chips fried in oil containing no extract until the last frying. The free radical
scavenging activity of rosemary extract in comparison to other natural antioxidants was also determined by the reduction of
O2
.- in a hypoxanthine/xanthine oxidase system. 相似文献
72.
Immobilization of new Mn(salen) complex over MCM-41 and its activity in asymmetric epoxidation of styrene 总被引:3,自引:0,他引:3
New tetradentate chelates of bis-Schiff bases were synthesized and then these chiral salen ligands were immobilized over mesoporous
MCM-41 by using the ion-exchange method. The efficiency of the chiral catalyst was examined in the asymmetric epoxidation
of styrene. Chiral Mn(salen) complexes immobilized onto mesoporous MCM-41 were stable during the reaction without any leaching
and exhibited relatively high enantioselectivity for epoxidation as compared with homogeneous complexes.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
73.
Response of generalist and specialist insects to qualitative allelochemical variation 总被引:7,自引:0,他引:7
We examined the effects of a set of four biosynthetically related iridoid glycosides, aucubin, catalpol, loganin, and asperuloside, on larvae of a generalist,Lymantria dispar (Lymantriidae), the gypsy moth, and an adapted specialist, the buckeye,Junonia coenia (Nymphalidae). In general,L. dispar grew and survived significantly less well on artificial diets containing iridoid glycoside, compared to a control diet without iridoid glycosides. In choice tests, previous exposure to a diet containing iridoid glycosides caused larvae subsequently to prefer iridoid glycoside-containing diets even though they were detrimental to growth and survival. In contrast,J coenia larvae grew and survived better on diets with aucubin and catalpol, the two iridoid glycosides found in the host plantPlantago lanceolata (Plantaginaceae), than on diets with no iridoid glycoside or with loganin and asperuloside. The results of choice tests of diets with and without iridoid glycosides and between diets with different iridoid glycosides reflected these differences as well. These results are discussed in terms of (1) differences between generalists and specialists in their response to qualitative variation in plant allelochemical content, (2) the induction of feeding preferences, and (3) the evolution of qualitative allelochemical variation as a plant defense. 相似文献
74.
This paper deals with the design of a nonlinear observer for sensorless induction motor control. Based upon the circle criterion approach, a nonlinear observer is designed to estimate pertinent but unmeasurable state variables of the considered induction machine for sensorless control purpose. The observer gain matrices are computed as a solution of linear matrix inequalities(LMI) that ensure the stability conditions of the state observer error dynamics in the sense of Lyapunov concepts. Measured and estimated state variables can be exploited to perform a state feedback control of the machine system. The simulation results are presented to illustrate the effectiveness of the proposed approach for nonlinear observer design. 相似文献
75.
三元不对称有机磷杀虫剂的良好药效已为人们所熟悉 ,而Profenofos的合成已有报导 ,他们采用了先合成s -正丙基硫代磷酰二氯〔1〕的合成路线。作者以三氯硫磷为起始原料 ,经过与无水乙醇反应生成O -乙基硫代磷酰二氯〔4〕,然后将其依次与 2 ,4 -二氯苯酚钠、氢氧化钠及溴代正丙烷 (加入催化量的苄基三乙基氯化铵BTEAC)反应 ,据软硬酸碱理论〔2〕,满意地得到了与预期符合的产物 (由红外光谱图中出现 p =0而证实 ) ,即O -乙基 -O -2 ,4 -二氯苯基 -s -正丙基硫醇代磷酸酯 (Ⅰ )杀虫剂 ,该化合物与Profenofos(Ⅱ… 相似文献
76.
77.
无轴承异步电机具有非线性、多变量和强耦合的特点,要实现电机稳定悬浮和旋转运行,必须对其进行非线性动态解耦控制。为了克服逆系统方法精确建模难的局限性,采用基于最小二乘支持向量机(LS-SVM)α阶逆系统方法对无轴承异步电机进行动态解耦控制的研究。首先利用最小二乘支持向量机辨识出无轴承异步电机的逆模型,然后将它串联在原系统前,将无轴承异步电机解耦成四个独立的伪线性子系统-2个径向位移子系统、一个速度子系统和一个磁链子系统。为保证鲁棒性能,最后对解耦后的系统采用非线性内模控制策略。研究表明,LS-SVMα阶逆系统方法能够实现无轴承异步电机径向悬浮力和旋转力之间的动态解耦控制,控制系统具有良好的静态和动态性能。 相似文献
78.
Chemical analysis of volatiles emitted by Pinus svlvestris after induction by insect oviposition 总被引:1,自引:0,他引:1
Gas chromatography – mass spectrometry analyses of the headspace volatiles of Scots pine (Pinus sylvestris) induced by egg deposition of the sawfly Diprion pini were conducted. The odor blend of systemically oviposition-induced pine twigs, attractive for the eulophid egg parasitoid Chrysonotomyia ruforum, was compared to volatiles released by damaged pine twigs (control) that are not attractive for the parasitoid. The mechanical damage inflicted to the control twigs mimicked the damage by a sawfly female prior to egg deposition. The odor blend released by oviposition-induced pine twigs consisted of numerous mono- and sesquiterpenes, which all were also present in the headspace of the artificially damaged control twigs. A quantitative comparison of the volatiles from oviposition-induced twigs and controls revealed that only the amounts of (E)--farnesene were significantly higher in the volatile blend of the oviposition-induced twigs. Volatiles from pine twigs treated with jasmonic acid (JA) also attract the egg parasitoid. No qualitative differences were detected when comparing the composition of the headspace of JA-treated pine twigs with the volatile blend of untreated control twigs. JA-treated pine twigs released significantly higher amounts of (E)--farnesene. However, the JA treatment induced a significant increase of the amount of further terpenoid components. The release of terpenoids by pine after wounding, egg deposition, and JA treatment is discussed with special respect to (E)--farnesene. 相似文献
79.
ZHOU HaiQiang JU Ping YANG Hui & SUN Ran Electrical Engineering School HoHai University Nanjing China Henan Power Dispatching & Communication Center Zhengzhou 《中国科学:信息科学(英文版)》2010,(4)
The existing equivalent methods usually only deal with static load models and neglect the dynamic characteristics of loads such as induction motors.This paper presents a dynamic equivalent method which considers motor dynamics.At first,the clustering criterion of motor loads is given.The motors with similar dynamic characteristics are classified into one group.Then,reduction of motors in the same group is carried out.Finally,parameters of the equivalent motor are calculated and the equivalent system is thus... 相似文献
80.
In order to investigate Joule heating power, a three-dimensional finite element model (FEM) was developed to predict Joule
heating power in the channels of double-loop inductor. The simulated results were compared with experimental data from low
load trials for a 400 kW inductor. The results, such as power factor and Joule heating power, show reasonable correlation
with experimental data, and Joule heating rate reaches the maximum at the corners and the minimum at the centre of the cross-section
area. With increasing relative permeability of iron core, length of coils, current frequency and resistivity of metal melt,
the power factor and Joule heating power change. It is concluded that current frequency, the resistivity and length of the
coil play a critical role in determining the power factor and Joule heating power, whereas relative permeability of the magnetic
core shows no significant influence on them. 相似文献