全文获取类型
收费全文 | 708342篇 |
免费 | 9769篇 |
国内免费 | 2102篇 |
专业分类
电工技术 | 13171篇 |
综合类 | 829篇 |
化学工业 | 105204篇 |
金属工艺 | 27018篇 |
机械仪表 | 20937篇 |
建筑科学 | 17192篇 |
矿业工程 | 3094篇 |
能源动力 | 19090篇 |
轻工业 | 61595篇 |
水利工程 | 7015篇 |
石油天然气 | 12007篇 |
武器工业 | 100篇 |
无线电 | 83585篇 |
一般工业技术 | 135815篇 |
冶金工业 | 138568篇 |
原子能技术 | 14055篇 |
自动化技术 | 60938篇 |
出版年
2021年 | 6196篇 |
2020年 | 4545篇 |
2019年 | 5903篇 |
2018年 | 10018篇 |
2017年 | 9882篇 |
2016年 | 10359篇 |
2015年 | 7107篇 |
2014年 | 11838篇 |
2013年 | 32248篇 |
2012年 | 18813篇 |
2011年 | 25954篇 |
2010年 | 20454篇 |
2009年 | 22965篇 |
2008年 | 23860篇 |
2007年 | 23477篇 |
2006年 | 20700篇 |
2005年 | 18971篇 |
2004年 | 18262篇 |
2003年 | 17976篇 |
2002年 | 17082篇 |
2001年 | 17068篇 |
2000年 | 16082篇 |
1999年 | 16905篇 |
1998年 | 42927篇 |
1997年 | 30179篇 |
1996年 | 23238篇 |
1995年 | 17576篇 |
1994年 | 15371篇 |
1993年 | 15079篇 |
1992年 | 11150篇 |
1991年 | 10390篇 |
1990年 | 10141篇 |
1989年 | 9740篇 |
1988年 | 9129篇 |
1987年 | 8123篇 |
1986年 | 7989篇 |
1985年 | 9005篇 |
1984年 | 8443篇 |
1983年 | 7517篇 |
1982年 | 7096篇 |
1981年 | 7240篇 |
1980年 | 6836篇 |
1979年 | 6668篇 |
1978年 | 6344篇 |
1977年 | 7635篇 |
1976年 | 9809篇 |
1975年 | 5618篇 |
1974年 | 5352篇 |
1973年 | 5488篇 |
1972年 | 4437篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
The application of barrier discharges at atmospheric pressure in air expands on the market of plasma technology, because it is an ecological and cost‐effective alternative to other processes of surface treatment. These plasmas usually consist of a multitude of spatially and temporally localized filaments, whose distribution should be as even as possible for homogeneous treatment. This holds especially for the plasma treatment of sensitive goods such as wool or other textiles. In equipment for continuous pass of material the barrier arrangements often consist of a system cylinder – cylinder or cylinder – plane, whereby the gap width changes locally. Space distribution and intensity of filaments has been investigated by means of short‐time photography and spatially resolved measurement of current distribution and energy distribution derived from it. The local dependency found can be explained by means of a capacitive equivalent circuit. 相似文献
152.
Neil P. Soice Adrian C. Maladono Doreen Y. Takigawa Arlan D. Norman William B. Krantz Alan R. Greenberg 《应用聚合物科学杂志》2003,90(5):1173-1184
Selected aromatic amides were used to model the chemical reactivity of aromatic polyamides found in thin‐film composite reverse osmosis (RO) membranes. Chlorination and possible amide bond cleavage of aromatic amides upon exposure to aqueous chlorine, which can lead to membrane failure, were investigated. Correlations are made of the available chlorine concentration, pH, and exposure time with chemical changes in the model compounds. From the observed reactivity trends, insights are obtained into the mechanism of RO membrane performance loss upon chlorine exposure. Two chemical pathways for degradation are shown, one at constant pH and another that is pH‐history dependent. An alternative strategy is presented for the design of chlorine‐resistant RO membranes, and an initial performance study of RO membranes incorporating this strategy is reported. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1173–1184, 2003 相似文献
153.
Hasegawa M. Furutani S. Doki S. Okuma S. 《Industrial Electronics, IEEE Transactions on》2003,50(5):912-919
This paper proposes a method for designing a robust full-order observer for vector-controlled induction motors taking core loss into account. Although conventional research focuses on parameter identification, global stability of the identification remains questionable. Therefore, robustness against some parameters is required. This paper describes the design of a robust full-order observer which takes core loss into account, using both the gain-scheduled H/sub /spl infin// control and the linear matrix inequality technique. This design always results in a stable controller. The robustness of the proposed method against variations of resistances is evaluated by experiments. 相似文献
154.
Honour Index (HoI), a method to evaluate research performance within different research fields, was derived from the impact
factor (IF). It can be used to rate and compare different categories of journals. HoI was used in this study to determine
the scientific productivity of stem cell research in the Asian Four Dragons (Hong Kong, Singapore, South Korea and Taiwan)
from 1981 to 2001. The methodology applied in this study represents a synthesis of universal indicator studies and bibliometric
analyses of subfields at the micro-level. We discuss several comparisons, and conclude the developmental trend in stem cell
research for two decades.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
155.
Barbara M. Johnston Peter R. Johnston 《International journal for numerical methods in engineering》2003,56(4):589-607
Accurate numerical evaluation of integrals arising in the boundary element method is fundamental to achieving useful results via this solution technique. In this paper, a number of techniques are considered to evaluate the weakly singular integrals which arise in the solution of Laplace's equation in three dimensions and Poisson's equation in two dimensions. Both are two‐dimensional weakly singular integrals and are evaluated using (in a product fashion) methods which have recently been used for evaluating one‐dimensional weakly singular integrals arising in the boundary element method. The methods used are based on various polynomial transformations of conventional Gaussian quadrature points where the transformation polynomial has zero Jacobian at the singular point. Methods which split the region of integration into sub‐regions are considered as well as non‐splitting methods. In particular, the newly introduced and highly accurate generalized composite subtraction of singularity and non‐linear transformation approach (GSSNT) is applied to various two‐dimensional weakly singular integrals. A study of the different methods reveals complex relationships between transformation orders, position of the singular point, integration kernel and basis function. It is concluded that the GSSNT method gives the best overall results for the two‐dimensional weakly singular integrals studied. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
156.
Chloride doped polyaniline conducting polymer films have been prepared in a protic acid medium (HCl) by potentiodynamic method
in an electrochemical cell and studied by cyclic voltammetry and FTIR techniques. The FTIR spectra confirmed Cl- ion doping in the polymers. The polymerization rate was found to increase with increasing concentration of aniline monomer.
But the films obtained at high monomer concentration were rough having a nonuniform flaky polyaniline distribution. Results
showed that the polymerization rate did not increase beyond a critical HCl concentration. Cyclic voltammetry suggested that,
the oxidation-reduction current increased with an increase in scan rate and that the undoped polyaniline films were not hygroscopic
whereas chloride doped polyaniline films were found to be highly hygroscopic. 相似文献
157.
158.
B. Pantchev P. Danesh K. Antonova B. Schmidt D. Grambole J. Baran 《Journal of Materials Science: Materials in Electronics》2003,14(10-12):751-752
The hydrogen content, its depth distribution, and its bonding configuration have been studied in hydrogenated amorphous silicon prepared by plasma-enhanced chemical vapor deposition with hydrogen-diluted silane. Nuclear reaction analysis and infrared spectroscopy were used to determine the total amount of hydrogen and its bonded component, respectively. It has been established that the total concentration of hydrogen does not depend on the film thickness, and has a uniform depth profile. The concentration of bonded hydrogen changes with the film thickness within the measurement accuracy. The data obtained suggest the presence of molecular (non-bonded) hydrogen, uniformly distributed in concentration across the film thickness. 相似文献
159.
Hook T.B. Brown J. Cottrell P. Adler E. Hoyniak D. Johnson J. Mann R. 《Electron Devices, IEEE Transactions on》2003,50(9):1946-1951
Lateral scattering of retrograde well implants is shown to have an effect on the threshold voltage of nearby devices. The threshold voltage of both NMOSFETs and PMOSFETs increases in magnitude for conventional retrograde wells, but for triple-well isolated NMOSFETs the threshold voltage decreases for narrow devices near the edge of the well. Electrical data, SIMS, and SUPREM4 simulations are shown that elucidate the phenomenon. 相似文献
160.
硫酸厂主鼓风机的主要设计准则 总被引:1,自引:1,他引:0
论述现代硫酸厂主鼓风机设计时必须考虑的关键因素,通过实例讨论操作费用与投资之间的平衡关系以及对装置竞争力的影响。建议在硫酸厂严酷的操作条件下改进风机特性,提高耐磨性并采用维修友好的设计。 相似文献