全文获取类型
收费全文 | 238403篇 |
免费 | 18796篇 |
国内免费 | 9718篇 |
专业分类
电工技术 | 13144篇 |
技术理论 | 24篇 |
综合类 | 15051篇 |
化学工业 | 40102篇 |
金属工艺 | 13666篇 |
机械仪表 | 15234篇 |
建筑科学 | 18507篇 |
矿业工程 | 7770篇 |
能源动力 | 6818篇 |
轻工业 | 14264篇 |
水利工程 | 3742篇 |
石油天然气 | 16992篇 |
武器工业 | 1725篇 |
无线电 | 26260篇 |
一般工业技术 | 28246篇 |
冶金工业 | 13099篇 |
原子能技术 | 2507篇 |
自动化技术 | 29766篇 |
出版年
2024年 | 841篇 |
2023年 | 3790篇 |
2022年 | 6234篇 |
2021年 | 9347篇 |
2020年 | 7232篇 |
2019年 | 6125篇 |
2018年 | 6889篇 |
2017年 | 7768篇 |
2016年 | 6963篇 |
2015年 | 9259篇 |
2014年 | 11806篇 |
2013年 | 13886篇 |
2012年 | 14932篇 |
2011年 | 16271篇 |
2010年 | 14171篇 |
2009年 | 13392篇 |
2008年 | 13053篇 |
2007年 | 12562篇 |
2006年 | 13092篇 |
2005年 | 11389篇 |
2004年 | 7701篇 |
2003年 | 6583篇 |
2002年 | 5857篇 |
2001年 | 5236篇 |
2000年 | 5807篇 |
1999年 | 6757篇 |
1998年 | 5672篇 |
1997年 | 4644篇 |
1996年 | 4365篇 |
1995年 | 3635篇 |
1994年 | 2923篇 |
1993年 | 2032篇 |
1992年 | 1594篇 |
1991年 | 1274篇 |
1990年 | 959篇 |
1989年 | 767篇 |
1988年 | 558篇 |
1987年 | 341篇 |
1986年 | 278篇 |
1985年 | 198篇 |
1984年 | 135篇 |
1983年 | 103篇 |
1982年 | 124篇 |
1981年 | 103篇 |
1980年 | 72篇 |
1979年 | 37篇 |
1978年 | 28篇 |
1977年 | 20篇 |
1976年 | 37篇 |
1973年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
951.
总结了南海北部陆缘晚期(或浅层)油气藏的勘探技术和方法,指出晚期油气成藏具有海底麻坑、气烟囱、"地震模糊带"和"亮点"等地震异常特征,从地化特征上可划分为浅层生物气、成熟—高成熟热解气和高含CO2热解气等3种油气成藏类型.在研究新构造运动表现形式的基础上,分析了逆断层、正断层和底辟—走滑断层3个断层活动区的晚期油气成藏机理,指出断层晚期活动和后期快速沉降促进了油气的运移和再分配,晚期油气成藏主要沿莺歌海盆地莺东斜坡带、东方—乐东区和沿琼东南盆地二号断裂带及珠江口盆地坳陷边缘斜坡带等分布,有利于油气和天然气水合物的勘探. 相似文献
952.
953.
从PMMA型LTCC素坯膜的制备和PMMA的排胶机理两方面,研究了LTCC基板Cu共烧金属化。结果表明,采用PMMA作为粘结剂的流延浆料具有剪切变稀行为,所得的流延坯膜微观组织均匀,叠压后坯体内部无分层现象。热失重、差热和傅立叶红外光谱联用分析结果表明高纯N2气氛中PMMA以解聚机理热解,热解后释放的主要产物为丙烯酸甲酯。在高纯N2气氛中LTCC与Cu共烧后Cu金属化膜平整、致密,连通良好。经测试,基板表面Cu导体方阻小于5mΩ/□。 相似文献
954.
Yunpeng Wang Zhaoyun Wang Changyi Zhao Hongjun Wang Jinzhong Liu Jialan Lu Dehan Liu 《Journal of Petroleum Geology》2007,30(4):339-356
In this paper we derive kinetic parameters for the generation of gaseous hydrocarbons (C1‐5) and methane (C1) from closed‐system laboratory pyrolysis of selected samples of marine kerogen and oil from the SW Tarim Basin. The activation energy distributions for the generation of both C1‐5 (Ea = 59‐72kcal, A = 1.0×1014 s?1) and C1 (Ea = 61‐78kcal, A = 6.06×1014 s?1) hydrocarbons from the marine oil are narrower than those for the generation of these hydrocarbons from marine kerogen (Ea = 50‐74kcal, A = 1.0×1014 s?1 for C1‐5; and Ea = 48‐72kcal, A=3.9×1013 s?1 for C1, respectively). Using these kinetic parameters, both the yields and timings of C1‐5 and C1 hydrocarbons generated from Cambrian source rocks and from in‐reservoir cracking of oil in Ordovician strata were predicted for selected wells along a north‐south profile in the SW of the basin. Thermodynamic conditions for the cracking of oil and kerogen were modelled within the context of the geological framework. It is suggested that marine kerogen began to crack at temperatures of around 120°C (or 0.8 %Ro) and entered the gas window at 138°C (or 1.05 %Ro); whereas the marine oil began to crack at about 140 °C (or 1.1 %Ro) and entered the gas window at 158 °C (or 1.6%Ro). The main geological controls identified for gas accumulations in the Bachu Arch (Southwest Depression, SW Tarim Basin) include the remaining gas potential following Caledonian uplift; oil trapping and preservation in basal Ordovician strata; the extent of breaching of Ordovician reservoirs; and whether reservoir burial depths are sufficiently deep for oil cracking to have occurred. In the Maigaiti Slope and Southwest Depression, the timing of gas generation was later than that in the Bachu Arch, with much higher yields and generation rates, and hence better prospects for gas exploration. It appears from the gas generation kinetics that the primary source for the gases in the Hetianhe gasfield was the Southwest Depression. 相似文献
955.
956.
弱凝胶调驱降维数值模拟方法研究 总被引:1,自引:0,他引:1
目前用于弱凝胶调驱的化学驱软件大多存在计算速度慢、数值弥散现象严重的问题,为了提高弱凝胶调驱数值模拟的速度和精度,提出了降低维数的模拟方法。利用追踪流线的方法,将弱凝胶调驱的三维渗流问题,转化为沿流线计算饱和度的一维问题,大大降低了求解饱和度方程组中方程的数目,从而提高了计算速度。利用该方法,模拟了玉门老君庙油田一个试验井区的水驱开发历史,优化了弱凝胶调驱的注入浓度、注入速度及注入体积等参数,并预测了弱凝胶调驱的动态,预测该方案可提高采收率7.6%。 相似文献
957.
Biofiltration is an efficient technology for treatment of gaseous waste. Its disadvantages, however, include large volume of bioreactor and slow adaptation to fluctuating concentrations in waste gas. Catalytic oxidation offers a high destructive efficiency at relatively low operating temperature and small unit. A bench scale system integrated with a biofilter and a catalytic oxidation unit for the treatment of gases containing o-xylene was investigated in this study. The catalytic oxidation unit was packed with Cu/Al2O3 catalyst. The results showed that 90% of o-xylene could be removed in the biofilter at the load below 38.2 g m−3 h−1. High o-xylene concentration in inlet gas resulted in an overload of the biofilter. Using the Cu/Al2O3 catalytic oxidation unit, the concentration of o-xylene could be reduced evidently. The combination of the chemical and microbial processes not only led to a high and stable efficiency of o-xylene conversion, but also improved capacity resisting the shock loads. The Cu/Al2O3 was studied for o-xylene oxidation in temperature range of 90–320 °C. The o-xylene conversion was improved correspondingly with the increasing of oxidation temperature. The reaction mechanism of o-xylene oxidation on Cu/Al2O3 was also investigated using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). 相似文献
958.
为适应城市发展需要,必须加强城市水利工作,通过对舒兰市水资源现状分析,对解决城市供水水源工程建设的措施进行探讨。 相似文献
959.
960.