全文获取类型
收费全文 | 180276篇 |
免费 | 18550篇 |
国内免费 | 12883篇 |
专业分类
电工技术 | 14687篇 |
技术理论 | 10篇 |
综合类 | 17694篇 |
化学工业 | 24895篇 |
金属工艺 | 11487篇 |
机械仪表 | 12011篇 |
建筑科学 | 13425篇 |
矿业工程 | 6787篇 |
能源动力 | 4849篇 |
轻工业 | 18328篇 |
水利工程 | 4779篇 |
石油天然气 | 7538篇 |
武器工业 | 2059篇 |
无线电 | 19605篇 |
一般工业技术 | 17727篇 |
冶金工业 | 7802篇 |
原子能技术 | 2577篇 |
自动化技术 | 25449篇 |
出版年
2024年 | 1030篇 |
2023年 | 3073篇 |
2022年 | 6604篇 |
2021年 | 8593篇 |
2020年 | 6264篇 |
2019年 | 4534篇 |
2018年 | 4966篇 |
2017年 | 5648篇 |
2016年 | 5246篇 |
2015年 | 7801篇 |
2014年 | 9489篇 |
2013年 | 11436篇 |
2012年 | 13544篇 |
2011年 | 14415篇 |
2010年 | 13002篇 |
2009年 | 12751篇 |
2008年 | 12792篇 |
2007年 | 12444篇 |
2006年 | 10925篇 |
2005年 | 9141篇 |
2004年 | 6655篇 |
2003年 | 5029篇 |
2002年 | 4616篇 |
2001年 | 4173篇 |
2000年 | 3810篇 |
1999年 | 2715篇 |
1998年 | 1942篇 |
1997年 | 1555篇 |
1996年 | 1480篇 |
1995年 | 1245篇 |
1994年 | 1068篇 |
1993年 | 773篇 |
1992年 | 608篇 |
1991年 | 445篇 |
1990年 | 388篇 |
1989年 | 365篇 |
1988年 | 253篇 |
1987年 | 168篇 |
1986年 | 129篇 |
1985年 | 92篇 |
1984年 | 70篇 |
1983年 | 60篇 |
1982年 | 59篇 |
1981年 | 58篇 |
1980年 | 69篇 |
1979年 | 30篇 |
1976年 | 13篇 |
1974年 | 11篇 |
1959年 | 32篇 |
1951年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
A locomotive cabin adsorption air‐conditioner has been equipped in #DF4B‐2369 locomotive; and has been successfully run for 2 years. It is powered by waste heat from the exhaust of the diesel engine. The influence on heat transfer is described by the equivalent heat transfer coefficient or thermal resistance of components inside the adsorber. The variation of adsorption capacity is expressed by a non‐equilibrium adsorption function. The dynamic heat transfer process of adsorption air‐conditioning system is treated with the lumped parameter method. Some typical running experimental results are present. The diesel engine rotating speed and locomotive speed influenced on the refrigeration system are discussed. The maximum mean refrigeration power is regarded as an objective function. Based on experiments and theoretical analysis, the running characteristics of the air‐conditioning system are optimized. Some techniques of performance improvement are suggested as well. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
2.
Chun-Tsen Lu Kun-Wei Lin Huey-Ing Chen Hung-Ming Chuang Chun-Yuan Chen Wen-Chau Liu 《Electron Device Letters, IEEE》2003,24(6):390-392
A new and interesting Pd-oxide-Al/sub 0.3/Ga/sub 0.7/As MOS hydrogen sensor has been fabricated and studied. The steady-state and transient responses with different hydrogen concentrations has been measured at various temperatures. Based on the large Schottky barrier height and presence of oxide layer, the studied device exhibits a high hydrogen detection sensitivity and wide temperature operating regime. The studied device exhibits the low-leakage current and obvious current changes when exposed to hydrogen-contained gas. Even at room temperature, a very high hydrogen detection sensitivity of 155.9 is obtained when a 9090 ppm H/sub 2//air gas is introduced. Furthermore, when exposed to hydrogen-contained gas at 95/spl deg/C, both the forward and reverse currents are substantially increased with increased hydrogen concentration. In other words, the studied device can be used as a hydrogen sensor under the applied bidirectional bias. Under the applied voltage of 0.35 V and 9090 ppm H/sub 2//air hydrogen ambient, a fast adsorption response time about 10 s is found. The transient and steady-state characteristics of hydrogen adsorption are also investigated. 相似文献
3.
对己二腈工业反应器提出了两釜串联带回流的模型,通过模拟计算得出模型的级间返混系数 f=6的结论。该模型能较好地预测工业反应器中物料组分浓度变化和气、液两相的流动特性;指出了现工业反应器的鼓泡中和段体积偏小是造成己二酸浓度偏高的关键;提出了可以通过增加串连一个鼓泡预反应段的改造方案,能有效地降低己二酸的浓度,从7%降至4%左右,从而能较好地减缓腐蚀和结焦。 相似文献
4.
测定钠中杂质的手动阻塞计的研究 总被引:1,自引:1,他引:0
文章介绍了测定钠中杂质浓度的手动阻塞计的原理、装置和实验结果。为了减少测量误差,我们研究了影响准确测定阻塞温度的因素,并且找到了减少测量误差的办法。在同样的杂质饱和温度下,该阻塞计测得的高、低阻塞温度所对应的杂质浓度差是很接近的。对氧其差值为1.03ppm;对氢为0.0763ppm。 相似文献
5.
Some methods determine the non-indolyl glucosinolates content in rapeseed as their hydrolysates: the isothiocyanates and the
oxazolidinethiones. These methods in their present form underestimate the amount of the glucosinolates content. In this investigation,
a modified method was developed to give a better quantitative estimate, indicating a glucosinolate level five times that obtained
by a typical existing method. 相似文献
6.
7.
应用事故树法对深水井控进行风险评估 总被引:5,自引:0,他引:5
深水井喷事故危害极大,严重时可导致井眼报废、船毁人亡等恶性后果,预防和控制深水井喷是国内外石油界的一个技术难题。文中利用风险树分析引发深水钻井工程事故的顶事件,重点讨论各底事件的相互联系及对系统的影响程度,分析顶事件的发生概率,为最大程度地减少深水井控事故的发生提供理论依据。通过对深水钻井过程中存在的风险进行分析,构建了深水井控风险分析事故树,并对其进行了定性与定量分析。通过风险分析,认为深水井控最主要的影响因素是关井及压井时设备故障、设计方法及操作失误的影响超过安全极限。分析表明,降低基本事件的发生概率对预防井喷作用明显,基本事件发生概率提高1倍,井喷发生概率提高近10倍。针对深水井控过程中存在的风险因素,从工艺、装备及人员要求方面提出了预防深水井喷的措施。 相似文献
8.
9.
A novel series of temperature‐sensitive poly[(N‐isopropylacrylamide)‐co‐(ethyl methacrylate)] (p(NIPAM‐co‐EMA)) microgels was prepared by the surfactant‐free radical polymerization of N‐isopropylacrylamide (NIPAM) with ethyl methacrylate (EMA). The shape, size dispersity and volume‐phase transition behavior of the microgels were investigated by transmission electron microscopy (TEM), ultraviolet–visible (UV–Vis) spectroscopy, dynamic light scattering (DLS) and differential scanning calorimetry (DSC). The transmission electron micrographs and DLS results showed that microgels with narrow distributions were prepared. It was shown from UV–Vis, DLS and DSC measurements that the volume‐phase transition temperature (VPTT) of the p(NIPAM‐co‐EMA) microgels decreased with increasing incorporation of EMA, but the temperature‐sensitivity was impaired when more EMA was incorporated, causing the volume‐phase transition of the microgels to become more continuous. It is noteworthy that incorporation of moderate amounts of EMA could not only lower the VPTT but also enhance the temperature‐sensitivity of the microgels. The reason for this phenomenon could be attributed to changes in the complicated interactions between the various molecules. Copyright © 2004 Society of Chemical Industry 相似文献
10.