全文获取类型
收费全文 | 17900篇 |
免费 | 332篇 |
国内免费 | 41篇 |
专业分类
电工技术 | 231篇 |
综合类 | 38篇 |
化学工业 | 2142篇 |
金属工艺 | 307篇 |
机械仪表 | 354篇 |
建筑科学 | 551篇 |
矿业工程 | 27篇 |
能源动力 | 267篇 |
轻工业 | 1788篇 |
水利工程 | 126篇 |
石油天然气 | 65篇 |
武器工业 | 2篇 |
无线电 | 1486篇 |
一般工业技术 | 2116篇 |
冶金工业 | 6806篇 |
原子能技术 | 201篇 |
自动化技术 | 1766篇 |
出版年
2022年 | 118篇 |
2021年 | 200篇 |
2020年 | 122篇 |
2019年 | 181篇 |
2018年 | 222篇 |
2017年 | 213篇 |
2016年 | 259篇 |
2015年 | 160篇 |
2014年 | 287篇 |
2013年 | 661篇 |
2012年 | 501篇 |
2011年 | 642篇 |
2010年 | 499篇 |
2009年 | 497篇 |
2008年 | 586篇 |
2007年 | 551篇 |
2006年 | 461篇 |
2005年 | 442篇 |
2004年 | 361篇 |
2003年 | 375篇 |
2002年 | 320篇 |
2001年 | 333篇 |
2000年 | 319篇 |
1999年 | 477篇 |
1998年 | 2245篇 |
1997年 | 1313篇 |
1996年 | 942篇 |
1995年 | 609篇 |
1994年 | 482篇 |
1993年 | 530篇 |
1992年 | 193篇 |
1991年 | 197篇 |
1990年 | 219篇 |
1989年 | 197篇 |
1988年 | 204篇 |
1987年 | 151篇 |
1986年 | 155篇 |
1985年 | 189篇 |
1984年 | 134篇 |
1983年 | 117篇 |
1982年 | 95篇 |
1981年 | 120篇 |
1980年 | 125篇 |
1979年 | 99篇 |
1978年 | 67篇 |
1977年 | 193篇 |
1976年 | 316篇 |
1975年 | 64篇 |
1974年 | 47篇 |
1973年 | 71篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Bart Van der Bruggen 《Membrane Technology》2003,2003(2):6-9
As the requirement for fresh water increases worldwide, there is a need for more and more plants that are able to treat non-conventional water sources. Sea water has become an important source of fresh water in many arid regions. This feature provides an overview of recent process improvements in sea water desalination using reverse osmosis, multi-stage flash, multi-effect distillation and electrodialysis. Areas discussed include the use of alternative energy sources (wind energy, solar energy and nuclear energy) for reverse osmosis or distillation processes, and the impact of the different desalination process on the environment. Also covered are the implementation of hybrid processes in sea water desalination, and the pretreatment of desalination plants by pressure-driven membrane processes. 相似文献
5.
Vladimir Rozenshtein Alexander Berg Haim Levanon Uwe Krueger Dietmar Stehlik Yuri Kandrashkin Art Van Der Est 《Israel journal of chemistry》2003,43(3-4):373-381
Light-induced spin-polarized transient EPR spectra are reported for several water-soluble copper porphyrins. The spectra are assigned to the doublet ground state, with emissive spin polarization resulting from photoexcitation and subsequent electronic relaxation. In contrast to other systems for which polarization of a doublet ground state has been observed, the exchange interactions in the copper porphyrins are strong and the geometry is fixed. It is proposed that intersystem crossing from the photoexcited trip-doublet to the trip-quartet state can lead to net polarization of the spin system and that this polarization is maintained during electronic decay, possibly via charge-transfer and exciplex states. The intensity of the observed spin polarization is essentially independent of the molecular orientation in the external field, but is strongly dependent on the nature of the charged peripheral groups. Possible reasons for this behavior are discussed. 相似文献
6.
Montanari D. Van Houdt J. Groeseneken G. Maes H.E. 《Solid-State Circuits, IEEE Journal of》1998,33(7):1090-1095
This paper presents a high-speed, small-area circuit specifically designed to identify the levels in the read out operation of a flash multilevel memory. The circuit is based on the analog computation of the Euclidean distance between the current read out from a memory cell and the reference currents that represent the different logic levels. An experimental version of the circuit has been integrated in a standard double-metal 0.7-μm CMOS process with a die area of only 140×100 μm2. Operating under a 5-V power supply, this circuit identifies the read-out current of a memory cell, and associates it with the appropriate logic level in 9 ns 相似文献
7.
Simultaneous determination of six ephedrines in urine sample has been achieved by high performance liquid chromatography on a Lichrospher RP-18 column, using methylamphetamine as internal standard. The 6 ephedrines are well separated in 25 minutes with resolution better than 1.8. This method has high recovery, selectivity and reproducibility, and the linearity is satisfactory from 1.5 micrograms/ml to 25 micrograms/ml with correlation coefficients better than 0.999. 相似文献
8.
The indications and results of single and double lung transplantation are described on the basis of 66 operations performed by the authors and on the background of the world literature. Lung transplantation is considered a new and promising therapeutic mode for treating patients with end-stage pulmonary failure related to fibrosis, emphysema, infective conditions, and pulmonary hypertension yielding satisfactory early results. The long-term prognosis of patients undergoing lung transplantation, like that of any other organ transfer, remains guarded. 相似文献
9.
10.
Dyspnea may be easily appreciated during exercise with dyspneic scales, but methodological standardisation still needs to be specified. Authors review the basic physiological mechanism relating dyspnea to indices obtained during a stress test. They propose to use the dyspnea/VE relationship. With the concept of dyspneic threshold (close to the ventilatory threshold) and the ramp that both could be modified (for instance by rehabilitation programmes including exercise training). Interpretation of dyspnea during an exercise test obviously needs to be integrated with other parameters studied during exercise. 相似文献