全文获取类型
收费全文 | 4429篇 |
免费 | 66篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 54篇 |
综合类 | 1篇 |
化学工业 | 487篇 |
金属工艺 | 37篇 |
机械仪表 | 59篇 |
建筑科学 | 102篇 |
矿业工程 | 3篇 |
能源动力 | 48篇 |
轻工业 | 307篇 |
水利工程 | 19篇 |
石油天然气 | 12篇 |
无线电 | 408篇 |
一般工业技术 | 570篇 |
冶金工业 | 2120篇 |
原子能技术 | 20篇 |
自动化技术 | 249篇 |
出版年
2021年 | 35篇 |
2019年 | 22篇 |
2018年 | 30篇 |
2017年 | 37篇 |
2016年 | 27篇 |
2015年 | 29篇 |
2014年 | 42篇 |
2013年 | 144篇 |
2012年 | 75篇 |
2011年 | 114篇 |
2010年 | 80篇 |
2009年 | 74篇 |
2008年 | 89篇 |
2007年 | 100篇 |
2006年 | 97篇 |
2005年 | 87篇 |
2004年 | 82篇 |
2003年 | 88篇 |
2002年 | 82篇 |
2001年 | 77篇 |
2000年 | 89篇 |
1999年 | 97篇 |
1998年 | 614篇 |
1997年 | 380篇 |
1996年 | 241篇 |
1995年 | 168篇 |
1994年 | 125篇 |
1993年 | 169篇 |
1992年 | 55篇 |
1991年 | 45篇 |
1990年 | 64篇 |
1989年 | 77篇 |
1988年 | 71篇 |
1987年 | 51篇 |
1986年 | 58篇 |
1985年 | 54篇 |
1984年 | 29篇 |
1983年 | 40篇 |
1982年 | 42篇 |
1981年 | 49篇 |
1980年 | 48篇 |
1979年 | 30篇 |
1978年 | 27篇 |
1977年 | 92篇 |
1976年 | 178篇 |
1975年 | 27篇 |
1974年 | 20篇 |
1973年 | 17篇 |
1972年 | 18篇 |
1971年 | 13篇 |
排序方式: 共有4496条查询结果,搜索用时 31 毫秒
1.
2.
3.
Conducting poly(aniline‐co‐o‐anisidine) (PAS) films with different ratios of aniline units in the polymer chain were prepared by oxidative polymerization of different molar ratios of aniline and o‐anisidine in 1 M HCl using cyclic voltammetry. Due to the much higher reactivity of o‐anisidine, the structure and properties of PASs were found to be dominated by the o‐anisidine units. The polymerization of poly‐o‐anisidine and PASs followed zero‐order kinetics with respect to formation of the polymer (film thickness) and the autocatalytic polymerization of aniline was completely inhibited. In contrast to polyaniline, a decrease in the polymerization temperature was found to increase the amount of copolymer formed and its redox charge. The presence of aniline units in PASs led to a pronounced increase in the molecular weight and conductivity, and a decrease in the solubility in organic solvents. Repetitive charging/discharging cycles showed that PASs resist degradation more than polyaniline. Copyright © 2003 Society of Chemical Industry 相似文献
4.
Crosstalk between microstrip transmission lines 总被引:1,自引:0,他引:1
Hill D.A. Cavcey K.H. Johnk R.T. 《Electromagnetic Compatibility, IEEE Transactions on》1994,36(4):314-321
Methods for prediction of crosstalk between microstrip transmission lines are reviewed and simplified for the weak-coupling case. Classical coupled transmission line theory is used for uniform lines, and potential and induced EMF methods are used for crosstalk between nonuniform lines. It is shown that the potential method is equivalent to classical coupled transmission line theory for the case of uniform lines. An experiment was performed for uniform coupled microstrip lines for frequencies from 50 MHz to 5 GHz, and good agreement between theory and measurement was obtained for both near- and far-end crosstalk 相似文献
5.
D Galasko T Saitoh Y Xia LJ Thal R Katzman LR Hill L Hansen 《Canadian Metallurgical Quarterly》1994,44(10):1950-1951
We determined apolipoprotein E (ApoE) genotypes in 122 autopsied demented patients. The frequency of the ApoE epsilon 4 allele was 39.6% in Alzheimer's disease (AD), 29.0% in the Lewy body variant of AD (LBV), and 6.25% in diffuse Lewy body disease. For AD and LBV patients, the epsilon 4 frequency was significantly higher than that reported in nondemented controls (10 to 15%). Therefore, LBV and AD share ApoE epsilon 4 as a genetic risk factor, providing further evidence that these conditions overlap. 相似文献
6.
High division of the brachial artery was observed in two cadavers, during routine dissection of upper extremities. In the first case, the brachial artery of the right upper extremity was divided into its two terminal branches immediately after passing between the lateral and medial roots of the median nerve and just below the origin of the profunda brachii artery. The lateral branch was the radial artery, located in the space normally occupied by the brachial artery and the medial one was the ulnar artery. In the second case, the brachial artery was divided into its two terminal branches just below the origin of the profunda brachii artery. Accurate knowledge of the relationships and course of these major arterial conduits and particularly of their variational patterns, is of considerable practical importance in the conduct of reperative surgery in the arm, forearm and hand. 相似文献
7.
8.
A device that harnesses the mechanical energy of skeletal muscle contracting in a linear configuration has been implanted in goats. This energy convertor transforms muscle work to hydraulic energy that could drive a variety of cardiac assist devices. The device is mounted with a rib clamp and plate affixed to the sternum by cortical bone screws. A transcutaneous hydraulic line carries a silicon based working fluid to an external system that controls the muscle load. In 60 to 70 kg goats, the latissimus dorsi insertion was reattached to the energy convertor. A Telectronics myostimulator with intramuscular electrodes stimulated the latissimus dorsi. In acute implants, hydraulic pressures in excess of 150 psi were obtained. Chronic implantation of the device allowed system evaluation in the conscious unanesthetized animal. Two weeks after implant, hydraulic pressures in excess of 200 psi were obtained and energy transferred to the external loading system exceeded 1 J per contraction. Six weeks after implant, the device continued to cycle freely. These initial results are very promising and suggest an implantable energy convertor is feasible. Development of an energy convertor is an important step toward tether-free skeletal muscle powered cardiac assist devices. 相似文献
9.
Two versions of the pressure swing adsorption process are analysed as a means for purification of the light component of a binary feed of arbitrary composition. Local equilibrium with linear, uncoupled isotherms is assumed. The results of the analysis show that a critical pressure ratio must be exceeded before complete purification is possible and that this pressure ratio increases as the light-component content of the feed decreases. When clean up of the light component is complete, pressurization with product leads to higher light-component recoveries than pressurization with feed. This difference becomes large for small separation factors, small fractions of the light component in the feed, and large pressure ratios. 相似文献
10.
Jun-Guo Lu Hill D.J. 《Circuits and Systems II: Express Briefs, IEEE Transactions on》2008,55(6):586-590
Sampled-data feedback control for master-slave synchronization schemes that consist of identical chaotic Lur'e systems is studied. Sufficient conditions for global asymptotic synchronization of such chaotic Lur'e systems are obtained using the free-weighting matrix approach and expressed in terms of linear matrix inequalities (LMIs). With the help of the LMI solvers, the sampled-data feedback control law can easily be obtained to globally asymptotically synchronize Lur'e chaotic systems. The effectiveness of the proposed method is finally illustrated via numerical simulations of chaotic Chua's circuits. 相似文献