全文获取类型
收费全文 | 29745篇 |
免费 | 2808篇 |
国内免费 | 1079篇 |
专业分类
电工技术 | 692篇 |
综合类 | 1016篇 |
化学工业 | 6248篇 |
金属工艺 | 3871篇 |
机械仪表 | 1160篇 |
建筑科学 | 1124篇 |
矿业工程 | 282篇 |
能源动力 | 3874篇 |
轻工业 | 2075篇 |
水利工程 | 64篇 |
石油天然气 | 308篇 |
武器工业 | 82篇 |
无线电 | 3331篇 |
一般工业技术 | 4468篇 |
冶金工业 | 4038篇 |
原子能技术 | 302篇 |
自动化技术 | 697篇 |
出版年
2024年 | 111篇 |
2023年 | 792篇 |
2022年 | 1667篇 |
2021年 | 1994篇 |
2020年 | 1237篇 |
2019年 | 993篇 |
2018年 | 923篇 |
2017年 | 1211篇 |
2016年 | 1221篇 |
2015年 | 1165篇 |
2014年 | 1844篇 |
2013年 | 1808篇 |
2012年 | 1960篇 |
2011年 | 2475篇 |
2010年 | 1669篇 |
2009年 | 1655篇 |
2008年 | 1281篇 |
2007年 | 1518篇 |
2006年 | 1361篇 |
2005年 | 1066篇 |
2004年 | 878篇 |
2003年 | 736篇 |
2002年 | 736篇 |
2001年 | 629篇 |
2000年 | 497篇 |
1999年 | 364篇 |
1998年 | 362篇 |
1997年 | 302篇 |
1996年 | 232篇 |
1995年 | 158篇 |
1994年 | 131篇 |
1993年 | 122篇 |
1992年 | 95篇 |
1991年 | 79篇 |
1990年 | 58篇 |
1989年 | 85篇 |
1988年 | 40篇 |
1987年 | 29篇 |
1986年 | 26篇 |
1985年 | 26篇 |
1984年 | 22篇 |
1983年 | 11篇 |
1982年 | 10篇 |
1981年 | 4篇 |
1980年 | 15篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1975年 | 6篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
热镀锌板(卷)工程设计中的环境保护问题 总被引:1,自引:0,他引:1
对热镀锌板(卷)的生产工艺、主要生产设备进行了简要介绍,并就其污染源(工序)、生产过程中产生的污染物及其控制措施进行了评述,同时就设计和生产中宜注意的几个环保问题进行了分析。 相似文献
3.
S. MESCHINI A. MOLINARI A. CALCABRINI G. CITRO G. ARANCIA 《Journal of microscopy》1994,176(3):204-210
The intracellular distribution of the anthracyclinic antibiotic adriamycin in living cultured cells has been investigated by confocal microscopy. In human melanoma cells (M14), adriamycin was localized inside the nuclei. When adriamycin-treated M14 cells were allowed to recover in drug-free medium, a complete efflux of the drug from the nucleus was revealed. In recovered cells, a weakly fluorescent signal was observed in the perinuclear region. When M14 cells were recovered in a medium containing colcemid, a microtubule depolymerizing agent, the drug transport from the nucleus to the cell periphery appeared to be inhibited, suggesting that the microtubule network is strongly involved in drug transport mechanisms. In multidrug-resistant (MDR) cells the intracellular location of adriamycin was shown to be noticeably different from that of the parental wild-type cells. In particular, in resistant human breast carcinoma cells (MCF-7), adriamycin appeared to be exclusively located within the cytoplasm whereas the nuclei were shown to be completely negative. When adriamycin treatment was performed in association with MDR revertants, such as Lonidamine (inhibitor of the energy metabolism) or verapamil (inhibitor of the P-glycoprotein efflux pump), a marked enhancement of the cytoplasmic signal was observed in resistant cells. Under these conditions, adriamycin appeared concentrated in the perinuclear region, but the nuclei were still negative. Confocal microscopy proved to be a very useful method for the study of the intracellular transport of fluorescent substances, such as anthracyclinic antibiotics, and for the investigation of the multidrug resistance phenomenon in tumour cells. 相似文献
4.
ABSTRACT: The traditional small-scale production of boucané, a cured smoked pork-belly product from Réunion, involves several unit operations that are performed in a single step. The aim of this study was to highligh the impact of 4 unit operations (salting, drying, cooking, and smoking) on stability, color, and flavor development in processed pork. These characateristics are the 3 main criteria of boucané's quality. Mass transfer, color, and volatile compounds were measured, analyzed, and compared in 4 products. Results indicated that a major quantity of volatile compounds detected in the processed meat were derived from the smoking process. Color variations were mainly explained by muscle pigment modification due to the cooking process, and by the input of volatile compounds of smoke. 相似文献
5.
Alessandro Fantoni Manuela Viera Rodrigo Martins 《Solar Energy Materials & Solar Cells》2002,73(2):148
In this paper a set of one-dimensional simulations of a-Si:H p–i–n junctions under different illumination conditions and with different intrinsic layer are presented. The simulation program ASCA permits the analysis of the internal electrical behaviour of the cell allowing a comparison among the different internal configurations determined by a change in the input set. Results about the internal electric configuration will be presented and discussed outlining their influence on the current tension characteristic curve. Considerations about the drift–diffusion and the generation–recombination balance distributions, outlined by the simulation, can be used to explain the correlation between the basic device output, the i-layer characteristics (thickness and DOS), the incident radiation intensity and photon energy. 相似文献
6.
7.
8.
9.
G. H. Palmir 《Journal of the Institute of Brewing》1987,93(4):332-333
The aleurone cells of barley, wheat, rice, rye, oats and triticale contained, comparatively, higher percentages of phosphorus than the aleurone cells of sorghum, maize or millet. The aleurone tissues of barley, wheat and rice had more phosphate than corresponding tissues of sorghum and maize. Phosphate was not detected in the aleurone tissue of maize but was found in trace amounts in the aleurone tissue of sorghum. 相似文献
10.
Per Hovstad Liching Sung 《International Journal of Satellite Communications and Networking》2005,23(2):91-110
The 1977 Broadcasting‐Satellite Service (BSS) Plan for Region 1 & 3 had been widely acknowledged to be out‐of‐date by the late 1980s. Development of digital modulation in the early 1990s provided an opportunity to update the technical provisions of the Plan to make it more economically viable. After a decade of work and three World Radiocommunication Conferences (WRCs), the revision of Region 1 & 3 BSS Plan was finally completed in 2003. The new Plan increased channel assignments from 5 to 10 analog‐equivalent channels for each country in Region 1, and from 4 to 12 channels for each country in Region 3. Yet, despite the increase in capacity, the new Plan is surprisingly similar to the original one in terms of the technical parameters. It is still based on national coverage, and the channel plan, orbital location, orbital spacing, and polarization are also the same. As a result, the new Plan is no more economically viable to implement than the old. To create economically viable BSS systems would most likely require modifications to the assignment in the Plan. Yet, modification procedures were made more difficult to apply after replanning. Less future implementation of BSS networks than would otherwise have occurred can be expected, and an inefficient usage of these frequency bands will likely result. On the other hand, less implemented systems will mean more capacity set aside for future use. This is important for countries that currently do not have satellite operations. In the end, BSS replanning reflects the eternal conflict between efficient usage and guaranteed future access. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献