全文获取类型
收费全文 | 33099篇 |
免费 | 3589篇 |
国内免费 | 1820篇 |
专业分类
电工技术 | 6973篇 |
技术理论 | 4篇 |
综合类 | 3027篇 |
化学工业 | 1538篇 |
金属工艺 | 743篇 |
机械仪表 | 2183篇 |
建筑科学 | 1837篇 |
矿业工程 | 1312篇 |
能源动力 | 3198篇 |
轻工业 | 451篇 |
水利工程 | 792篇 |
石油天然气 | 1404篇 |
武器工业 | 313篇 |
无线电 | 4009篇 |
一般工业技术 | 2017篇 |
冶金工业 | 1124篇 |
原子能技术 | 313篇 |
自动化技术 | 7270篇 |
出版年
2024年 | 167篇 |
2023年 | 558篇 |
2022年 | 920篇 |
2021年 | 1205篇 |
2020年 | 1198篇 |
2019年 | 966篇 |
2018年 | 814篇 |
2017年 | 1102篇 |
2016年 | 1206篇 |
2015年 | 1302篇 |
2014年 | 2261篇 |
2013年 | 1884篇 |
2012年 | 2545篇 |
2011年 | 2776篇 |
2010年 | 2116篇 |
2009年 | 2061篇 |
2008年 | 1893篇 |
2007年 | 2035篇 |
2006年 | 1775篇 |
2005年 | 1563篇 |
2004年 | 1251篇 |
2003年 | 1096篇 |
2002年 | 928篇 |
2001年 | 842篇 |
2000年 | 745篇 |
1999年 | 559篇 |
1998年 | 412篇 |
1997年 | 408篇 |
1996年 | 306篇 |
1995年 | 293篇 |
1994年 | 216篇 |
1993年 | 198篇 |
1992年 | 144篇 |
1991年 | 128篇 |
1990年 | 82篇 |
1989年 | 86篇 |
1988年 | 50篇 |
1987年 | 47篇 |
1986年 | 38篇 |
1985年 | 47篇 |
1984年 | 38篇 |
1983年 | 19篇 |
1982年 | 19篇 |
1981年 | 17篇 |
1980年 | 20篇 |
1979年 | 21篇 |
1975年 | 12篇 |
1974年 | 11篇 |
1973年 | 13篇 |
1966年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
This paper presents a partial scan algorithm, calledPARES (PartialscanAlgorithm based onREduced Scan shift), for designing partial scan circuits. PARES is based on the reduced scan shift that has been previously proposed for generating short test sequences for full scan circuits. In the reduced scan shift method, one determines proch FFs must be controlled and observed for each test vector. According to the results of similar analysis, PARES selects these FFs that must be controlled or observed for a large number of test vectors, as scanned FFs. Short test sequences are generated by reducing scan shift operations using a static test compaction method. To minimize the loss of fault coverage, the order of test vectors is so determined that the unscanned FFs are in the state required by the next test vector. If there are any faults undetected yet by a test sequence derived from the test vectors, then PARES uses a sequential circuit test generator to detect the faults. Experimental results for ISCAS'89 benchmark circuits are given to demonstrate the effectiveness of PARES. 相似文献
43.
Due to technology scaling and increasing clock frequency, problems due to noise effects lead to an increase in design/debugging efforts and a decrease in circuit performance. This paper addresses the problem of efficiently and accurately generating two-vector tests for crosstalk induced effects, such as pulses, signal speedup and slowdown, in digital combinational circuits. These noise effects can propagate through a circuit and create a logic error in a latch or at a primary output. We have developed a mixed-signal test generator, called XGEN, that incorporates classical static values as well as dynamic signals such as transitions and pulses, and timing information such as signal arrival times, rise/fall times, and gate delay. In this paper we first discuss the general framework of the test generation algorithm followed by computational results. Comparison of results with SPICE simulations confirms the accuracy of this approach. 相似文献
44.
45.
Humanitarian psychological support as an organized field is relatively young. Pioneers in the field were involved primarily in providing psychological support to refugees and internally displaced persons in conflict and nonconflict situations. This article describes basic principles for the design of psychological support programs and interventions. The International Federation of Red Cross and Red Crescent Societies (IFRC) began a psychological support program in 1991. The IFRC chose psychological first aid as its model for implementation in developing countries. Psychological first aid fits all the principles for psychological support program design and is adapted to individual communities. The first generation of psychological support programs differed dramatically depending on the countries in which they were developed. A second generation of psychological support programs evolved in response to the earthquake/tsunami of December 26, 2004. The Inter-Agency Standing Committee international guidelines consolidated the advances of second-generation programs and provided a clear indication of the wide acceptance of the importance of psychological support. A glimpse is provided of the third generation of psychological support programs, and an admonition is made for a more empirical evaluation of the effectiveness of interventions. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
46.
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
47.
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
48.
The development of renewable technologies in the last decade has been exceptional. In photovoltaic (PV) for example, efforts were not only limited to merely improving their efficiency but also to the reduction of the cost of cells and modules via volume production for commercial markets. There are many national schemes promoting the use of PV technology and regional targets for a share of renewable energy production. This paper attempts to relay to the reader a journey, based on experience, approaches for enhancing the prospect of utilising solar energy within the society we live in. The issue of expansion or enhancing the utilisation of solar energy can be undertaken by individuals, groups, institutions and governments. The aim of this paper is to provide some examples, which could serve as a framework in which action could be taken to promote solar technology. 相似文献
49.
高精度视觉贴片机拾放程序设计编程 总被引:3,自引:0,他引:3
龙绪明 《电子工业专用设备》2002,31(3):151-155,183
探讨了SMT高精度视觉贴片机难点之一拾放程序设计编程 ,重点介绍示教编程和CAD输入编程设计方法。 相似文献
50.
曹闯明 《中国海上油气(工程)》2002,(6)
通过业余学习,自编了一些AutoLISP小型应用程序,并在绘制PFD和P&ID中取得了良 好的应用效果。对此实践进行了研讨,以期获得可资借鉴之处。 相似文献