全文获取类型
收费全文 | 11384篇 |
免费 | 741篇 |
国内免费 | 595篇 |
专业分类
电工技术 | 353篇 |
综合类 | 579篇 |
化学工业 | 2390篇 |
金属工艺 | 1267篇 |
机械仪表 | 430篇 |
建筑科学 | 403篇 |
矿业工程 | 133篇 |
能源动力 | 330篇 |
轻工业 | 603篇 |
水利工程 | 85篇 |
石油天然气 | 409篇 |
武器工业 | 58篇 |
无线电 | 1128篇 |
一般工业技术 | 2075篇 |
冶金工业 | 407篇 |
原子能技术 | 215篇 |
自动化技术 | 1855篇 |
出版年
2024年 | 25篇 |
2023年 | 179篇 |
2022年 | 292篇 |
2021年 | 349篇 |
2020年 | 267篇 |
2019年 | 237篇 |
2018年 | 258篇 |
2017年 | 295篇 |
2016年 | 287篇 |
2015年 | 316篇 |
2014年 | 468篇 |
2013年 | 572篇 |
2012年 | 590篇 |
2011年 | 853篇 |
2010年 | 597篇 |
2009年 | 697篇 |
2008年 | 749篇 |
2007年 | 786篇 |
2006年 | 652篇 |
2005年 | 591篇 |
2004年 | 503篇 |
2003年 | 483篇 |
2002年 | 328篇 |
2001年 | 344篇 |
2000年 | 452篇 |
1999年 | 220篇 |
1998年 | 169篇 |
1997年 | 133篇 |
1996年 | 123篇 |
1995年 | 132篇 |
1994年 | 128篇 |
1993年 | 109篇 |
1992年 | 96篇 |
1991年 | 74篇 |
1990年 | 63篇 |
1989年 | 53篇 |
1988年 | 47篇 |
1987年 | 44篇 |
1986年 | 51篇 |
1985年 | 27篇 |
1984年 | 13篇 |
1983年 | 9篇 |
1982年 | 11篇 |
1981年 | 12篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1977年 | 8篇 |
1976年 | 3篇 |
1975年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
The dynamic behaviour of a thermostatic-expansion–valve (TEV)-controlled dry-evaporator is studied experimentally and numerically. Although the linear model of the TEV together with the distributed model of the evaporator is able to predict the stable dynamic response of the system adequately, it fails to reproduce the hunting behaviour that is observed under certain operating conditions. A scrutiny of the experimental data reveals the possible existence of hysteresis in the system. The distributed model including the experimentally determined input-output characteristics of the TEV is able to reproduce the main features of the hunting oscillations well. The amplitude and frequency of these oscillations depend on the static superheat setting, the heat load of the evaporator and the time constant of the TEV bulb. 相似文献
42.
43.
Kazutaka Chibana Chaedong Kang Masashi Okada Koji Matsumoto Tetsuo Kawagoe 《International Journal of Refrigeration》2002,25(2):83
Water-silicone oil emulsion with an additive, (C2H5O)3SiC3H6NH2, was examined as a heat storage material. A spiral tube used as a heat exchanger was immersed in a low temperature bath and the emulsion was circulated in the tube to make ice continuously. Ice was separated from the ice–liquid suspension in an outlet tank. The amount of formed ice, the temperatures of the inlet and the outlet of the heat exchanger, and the temperatures in the tube wall were measured and the overall heat transfer coefficient and the heat flux through the tube were calculated. Experiments were carried out, varying the flow rate, the temperature of cooling brine, and the thickness of tube wall. The condition under which slurry ice was formed continuously without adhesion of ice to the cooling wall was clarified. Though decrease in the thermal resistance of the tube increased the rate of ice formation or raised the brine temperature, it narrowed the range of the flow rate and of the brine temperature in which slurry ice was formed continuously. 相似文献
44.
Mitsuhiro Fukuta Tadashi Yanagisawa Hiroaki Iwata Kazutaka Tada 《International Journal of Refrigeration》2002,25(7)
This paper discusses the feasibility of a vapor compression/absorption hybrid refrigeration cycle for energy saving and utilization of waste heat. The cycle employs propane as a natural refrigerant and a refrigeration oil as an absorbent. A prototype of the cycle is constructed, in which a compressor and an absorption unit are combined in series. The performance of the cycle is examined both theoretically and experimentally. Although the solubility of the propane with the oil is not enough as a working pair in the absorption unit, the theoretical calculation shows that the hybrid cycle has a potential to achieve a higher performance in comparison with a simple vapor compression cycle by using the waste heat. In the experiment, the prototype cycle is operated successfully and it is found that an improvement of an absorber is necessary to achieve the good performance close to the theoretical one. The application of an AHE (absorber heat exchanger) can reduce the heat input to a generator. Further examinations on some other combinations of refrigerant/refrigeration oil and additives are desirable. 相似文献
45.
8-R-9苄基-9H-嘌呤衍生物的合成研究 总被引:5,自引:2,他引:3
采用 (Ph3 P) 2 PdCl2 为催化剂 ,DMF为溶剂 ,对 8 碘 9 苄基 9H 嘌呤与有机锡试剂RSnBu3 (R=乙烯基、2 噻吩基、2 呋喃基、苯乙炔基和苯基等 )之间的Stille偶合反应进行了研究 ,合成出了5种 8位取代的嘌呤衍生物。在反应温度为 80℃ ,n(8 碘 9 苄基 9H 嘌呤 )∶n (RSnBu3 )∶n〔(Ph3 P) 2 PdCl2 〕 =1 0∶1 2∶0 0 5的较佳工艺条件下 ,产品收率 4 1%~ 91%。用1H NMR、13 C NMR和MS对产物进行了表征 相似文献
46.
直接序列扩展频谱中伪码优选研究 总被引:1,自引:0,他引:1
本文从最优化理论和工程实际出发,全面分析和完善了直接序列扩展频谱中伪码的数学模型,在此基础上,建立了一种较准确的伪码优选数学模型,并探讨了合适的搜索算法。 相似文献
47.
K0.9Li0.1(Ta0.5Nb0.5)O3晶体压电应变系数的测量 总被引:4,自引:2,他引:2
用准静态d_(33)测量仪和干涉法相结合。测量了K_(0.9)Li_(0.1)(Ta_(0.5)Nb_(0.5)Nb_(0.5))O_3晶体的压电应变系数。结果为:d_(33)=86.0,d_(33)=一29.5,d_(15)=112.9×10 ̄(-12)C/N. 相似文献
48.
准噶尔盆地边缘山区的初步静校正 总被引:1,自引:0,他引:1
本文讨论了准噶尔盆地边缘山区替代速度对初步静校正精度的影响。通过用相遇法[1]从多次覆盖反射地震采集记录中的初至折射波计算基岩面的t0时和选用合适的替代速度进行初步静校正,在很大程度上消除了表层不均匀和基岩面起伏引起的大静校量,使静校误差控制在自动静校的要求范围之内、从而提高了速度谱和水平叠加剖面的质量。 相似文献
49.
简要介绍了随钻气侵检测仪的结构特点、工作原理、现场模拟试验及应用情况。中原油田全尺寸实验井和胜利油田6口井的现场试验及应用结果表明,该仪器能实现早期气侵检测,比常规方法检测到气侵的时间明显提前,对高压气井和复杂地层井控具有重要的现实意义。 相似文献
50.