全文获取类型
收费全文 | 6367篇 |
免费 | 685篇 |
国内免费 | 291篇 |
专业分类
电工技术 | 353篇 |
综合类 | 382篇 |
化学工业 | 1143篇 |
金属工艺 | 349篇 |
机械仪表 | 396篇 |
建筑科学 | 479篇 |
矿业工程 | 160篇 |
能源动力 | 210篇 |
轻工业 | 398篇 |
水利工程 | 130篇 |
石油天然气 | 244篇 |
武器工业 | 74篇 |
无线电 | 797篇 |
一般工业技术 | 862篇 |
冶金工业 | 432篇 |
原子能技术 | 81篇 |
自动化技术 | 853篇 |
出版年
2024年 | 45篇 |
2023年 | 131篇 |
2022年 | 247篇 |
2021年 | 375篇 |
2020年 | 254篇 |
2019年 | 193篇 |
2018年 | 247篇 |
2017年 | 241篇 |
2016年 | 249篇 |
2015年 | 289篇 |
2014年 | 378篇 |
2013年 | 398篇 |
2012年 | 480篇 |
2011年 | 473篇 |
2010年 | 391篇 |
2009年 | 336篇 |
2008年 | 291篇 |
2007年 | 263篇 |
2006年 | 271篇 |
2005年 | 219篇 |
2004年 | 199篇 |
2003年 | 162篇 |
2002年 | 149篇 |
2001年 | 129篇 |
2000年 | 126篇 |
1999年 | 120篇 |
1998年 | 117篇 |
1997年 | 108篇 |
1996年 | 81篇 |
1995年 | 70篇 |
1994年 | 60篇 |
1993年 | 50篇 |
1992年 | 36篇 |
1991年 | 22篇 |
1990年 | 24篇 |
1989年 | 24篇 |
1988年 | 16篇 |
1987年 | 11篇 |
1986年 | 8篇 |
1985年 | 5篇 |
1984年 | 8篇 |
1982年 | 10篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1976年 | 6篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 3篇 |
排序方式: 共有7343条查询结果,搜索用时 15 毫秒
1.
Rajoo R. Lim S.S. Wong E.H. Hnin W.Y. Seah S.K.W. Tay A.A.O. Iyer M. Tummala R.R. 《Advanced Packaging, IEEE Transactions on》2008,31(2):377-385
A wafer level packaging technique has been developed with an inherent advantage of good solder joint co-planarity suitable for wafer level testing. A suitable weak metallization scheme has also been established for the detachment process. During the fabrication process, the compliancy of the solder joint is enhanced through stretching to achieve a small shape factor. Thermal cycling reliability of these hourglass-shaped, stretch solder interconnections has been found to be considerably better than that of the conventional spherical-shaped solder bumps. 相似文献
2.
Business process redesign (BPR) has been widely touted as a means for leveraging the power of information technology to change business processes radically, resulting in substantial improvements in organizational effectiveness and efficiency. This study represents an early attempt at examining the strategic nature of the phenomenon. Because BPR is radical change and has the ability to alter both the competitive and operational nature of the corporation, it is critical that BPR be coordinated with corporate strategy. Through a survey of information system executives, the relationships between corporate competitive strategy and three types of BPR – intrafunctional, interfunctional and interorganizational – were examined. It was found that organizations following a cost strategy tended to do more BPR projects on interfunctional processes. Furthermore, the positive effect of a cost strategy on interfunctional BPR was found to be strengthened by the degree of integration of IS and business planning. It was also found that while interorganizational BPR was not related to a specific strategy, it was strongly related directly with IS–business planning integration. 相似文献
3.
Jackson T.J. Engman E.T. Le Vine D. Schmugge T.J. Lang R. Wood E. Teng W. 《Geoscience and Remote Sensing, IEEE Transactions on》1994,32(1):201-206
MACHYDR0'90 was an experiment conducted in Pennsylvania in 1990 to study the synergistic use of remote sensors in multitemporal hydrologic studies. As part of this mission the pushbroom microwave radiometer was flown and used to produce brightness temperature maps. Verification studies and vegetation algorithms for mixed land cover areas are described 相似文献
4.
In this study, the diffusion of various types of solvent in oil palm empty fruit bunch/polyurethane composites, produced from chemically modified empty fruit bunches, was investigated. The solubility parameters and polymer–solvent interaction parameters of the produced composites were determined. The void contents of the composites were also determined before swelling tests to eliminate the free solvent present in the system. From the results obtained, we found that the diffusion of the solvents was dependent on the compatible group available and the voids present in the system. The solubility parameters of the empty fruit bunch/polyurethane composites with different degrees of chemical modification were 11.6 and 11.7 (cal/cm?3)1/2. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
5.
Li Yu-cheng Teng Bin 《水动力学研究与进展(B辑)》1993,(2)
By using Cokelet's wave theory,the limiting wave height and the relative waveangular frequency in wave-current field were calculated in this paper.It is indicated by numeri-cal calculation that if the water depth is not too small,the result given by authors'calculationare very close to the results of limiting wave height by Dalrymple(1975)and to the data of rel-ative wave angular frequency by linear wave theory;but if water depth is rather small,thereare some discrepancy, 相似文献
6.
The authors describe an experiment, a model, and an analytic method for on/off vs. continuous policy evaluation. The methodology was developed and verified through experimentation. An experimental life-test of small DC motors was designed and performed; it involved on/off cycling vs. continuous operation under multiple stresses. A stress-factor reliability model based on the two-parameter Weibull proportional-hazards life distribution was fitted to the data. The analysis provides an estimate of the model parameters for the life distribution of the DC motors under two operating policies, while under multiple stresses. The characteristic life was related to the explanatory covariates: voltage, on/off cycling, and load. Due to the proportional hazards (common Weibull shape) nature of the model, acceleration factors were calculated to relate the stress levels. The reliability model was extended to develop a simple rule to aid in a decision between on/off cycling and continuous-run policies (to achieve higher reliability). The proposed model (with covariates) allows a much broader approach to reliability modeling than the usual Weibull model (without covariates) because it predicts the reliability under various environmental combinations 相似文献
7.
A number of methods of surface preparation of tantalum for encapsulation in silicone rubber and for structural adhesive bonding were explored. The only ones which could be generally useful were boiling for 24 hours in distilled water (28% improvement) or boiling for 4 hours in 20% sodium hydroxide solution followed by boiling for 2 hours in dilute hydrochloric acid (34% improvement). An alternative, which could sometimes be used, was heating in air for at least 2 hours at 100°C. 相似文献
8.
9.
Jing Lv Longhai Guo Chunjie Xie Weitong Xu Jun Ye Xiaoyu Li Teng Qiu Xinlin Tuo 《应用聚合物科学杂志》2021,138(44):51316
Being a new kind of nanomaterials, aromatic polyamide nanofibers (ANF) have been much highlighted in recent studies. We here demonstrate an isopropyl alcohol (IPA) accelerated chemical cleavage on poly (p-phenylene terephthalamide) chopped fibers, which provides an efficient preparation method of ANF. The comprehensive study on the processes accelerated by different alcohols revealed that the preparation time of ANF in the mixed medium of dimethyl sulfoxide (DMSO)-alcohol (20:1 in volume) was shorten to 45 min and 75 min for methanol (ethanol) and isopropanol, respectively. However, the nanofibers prepared in DMSO-IPA exhibited the minimum in axial and radial dimensions, providing the finest and most uniform diameter of 16 nm. The corresponding ANF films through vacuum assisted filtration also showed the highest tensile strength of 150 MPa, in comparison with those of the ANF films prepared using other alcohols, which were about 110 MPa. Furthermore, ANF/silicon hybrid films were prepared by the ionic ring-opening reaction followed by the alkoxysilane condensation and nanoparticle fabrication. By changing the organo functional groups in the alkoxysilane, the surface of the films were adjustable in a wide contact angle range from 56° (hydrophilic) to 150° (superhydrophobic), suggesting the amendable interfacial properties potential applicable to composite fabrication with most of the resin matrix. 相似文献
10.