全文获取类型
收费全文 | 49793篇 |
免费 | 4236篇 |
国内免费 | 2144篇 |
专业分类
电工技术 | 3582篇 |
综合类 | 3477篇 |
化学工业 | 10269篇 |
金属工艺 | 7479篇 |
机械仪表 | 1917篇 |
建筑科学 | 6307篇 |
矿业工程 | 1346篇 |
能源动力 | 3245篇 |
轻工业 | 3405篇 |
水利工程 | 848篇 |
石油天然气 | 1594篇 |
武器工业 | 323篇 |
无线电 | 2480篇 |
一般工业技术 | 5236篇 |
冶金工业 | 3019篇 |
原子能技术 | 592篇 |
自动化技术 | 1054篇 |
出版年
2024年 | 250篇 |
2023年 | 920篇 |
2022年 | 1773篇 |
2021年 | 1990篇 |
2020年 | 1805篇 |
2019年 | 1400篇 |
2018年 | 1320篇 |
2017年 | 1798篇 |
2016年 | 1743篇 |
2015年 | 1781篇 |
2014年 | 2711篇 |
2013年 | 2801篇 |
2012年 | 3264篇 |
2011年 | 3636篇 |
2010年 | 2652篇 |
2009年 | 2846篇 |
2008年 | 2335篇 |
2007年 | 2897篇 |
2006年 | 2839篇 |
2005年 | 2447篇 |
2004年 | 2030篇 |
2003年 | 1804篇 |
2002年 | 1596篇 |
2001年 | 1369篇 |
2000年 | 1093篇 |
1999年 | 975篇 |
1998年 | 776篇 |
1997年 | 660篇 |
1996年 | 492篇 |
1995年 | 484篇 |
1994年 | 369篇 |
1993年 | 281篇 |
1992年 | 237篇 |
1991年 | 191篇 |
1990年 | 151篇 |
1989年 | 99篇 |
1988年 | 71篇 |
1987年 | 62篇 |
1986年 | 35篇 |
1985年 | 26篇 |
1984年 | 28篇 |
1983年 | 27篇 |
1982年 | 31篇 |
1981年 | 15篇 |
1980年 | 17篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1960年 | 3篇 |
1959年 | 9篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
吐哈油田部分区块地层压力系数小于0.9,常规水基压井液对储层伤害大,若使用油基压井液成本高,环境污染严重。通过实验优选出了一种低密度水基微泡沫压井液。该压井液具有密度低、泡沫强度高、稳定性好、携砂能力强等优点。现场应用表明,低密度微泡沫压井液稳定时间大于48 h,密度在0.70~0.99 g/cm3之间可调,抗油污染能力强,抗油大于8%,抗温在100℃以上,岩心污染后渗透率恢复值大于80%;并且施工方便,成本低,具有储层保护能力,使用微泡沫压井液的井表皮系数在0.20~2.34之间。 相似文献
3.
回热损失对磁斯特林制冷循环制冷率的影响 总被引:7,自引:0,他引:7
从铁磁质的磁化强度一般表示式出发,探讨热阻和回热损失对磁斯特林制冷循环性能的影响,导出最大制冷率及其它性能参数。得到了结果适用于以顺磁质为工质的磁斯特林制冷循环。并指出在理想回热条件下的结论也适用于磁卡诺制冷循环。 相似文献
4.
5.
ImprovingWearResistanceoftheNibaseThermalSprayWeldingCoatingUsingRareEarthsZhaiGuangjie(翟光杰)(InstituteofPhysics,AcademicaSi... 相似文献
6.
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
7.
激光熔覆Ni基SiC合金涂层组织与性能的研究 总被引:5,自引:0,他引:5
利用5kWCO2连续波激光器在16Mn钢基材表面对含20%(体积比)SiC陶瓷粉末的镍基自熔性合金粉末进行激光熔覆得到Ni基SiC合金涂层(NiSiC)。研究了合金涂层的组织形貌及相结构,并用单纯的镍基合金涂层(Ni60)进行了显微硬度及滑动磨损性能的对比试验。结果表明,NiSiC合金涂层由γ枝晶及其间的共晶组织组成,主要组成相为γ-Ni,γ-(Ni,Fe)固溶体和(Cr,Fe)7C3,Cr23C6及(Cr,Si)3Ni3Si等化合物。添加SiC的镍基合金涂层NiSiC比单纯的镍基合金涂层Ni60具有较高的硬度和耐磨性。 相似文献
8.
Jrgen Sjdin 《国际能源研究杂志》2002,26(6):475-494
Energy taxation in Sweden is complicated and strongly guides and governs district energy production. Consequently, there is a need for methods for accurate calculation and analysis of effects that different energy tax schemes may have on district energy utilities. Here, a practicable method to analyse influence of such governmental policy measures is demonstrated. The Swedish Government has for some years now been working on a reform of energy taxation, and during this process, several interest groups have expressed their own proposals for improving and developing the system of energy taxation. Together with the present system of taxation, four new alternatives, including the proposed directive of the European Commission, are outlined in the paper. In a case study, an analysis is made of how the different tax alternatives may influence the choice of profitable investments and use of energy carriers in a medium‐sized district‐heating utility. The calculations are made with a linear‐programming model framework. By calculating suitable types and sizes of new investments, if any, and the operation of existing and potential plants, total energy costs are minimized. Results of the analysis include the most profitable investments, which fuel should be used, roughly when during a year plants should be in operation, and at what output. In most scenarios, the most profitable measure is to invest in a waste incineration plant. However, a crucial assumption is, with reference to the new Swedish waste disposal act, a significant income from incinerating refuse. Without this income, different tax schemes result in different technical solutions being most profitable. An investment in cogeneration seems possible in only one scenario. It is also found that particular features of some alternatives seem to oppose both main governmental policy goals, and intentions of the district heating company. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
9.
10.
提高自蔓延陶瓷内衬钢管耐蚀性研究的进展 总被引:1,自引:0,他引:1
广泛应用于石油,化工,能源等领域的钢管,除了要有高强度外,还要有良好的耐蚀性。自蔓延高温合成技术是制备耐蚀钢管的新技术,具有工艺简单,成本低和产品耐蚀性能好等特点。介绍了自蔓延高温合成陶瓷内衬钢管的原理和提高陶瓷内衬钢管耐蚀性的措施,展望了耐蚀陶瓷内衬钢管在工业生产上的应用前景。 相似文献