全文获取类型
收费全文 | 13429篇 |
免费 | 1039篇 |
国内免费 | 616篇 |
专业分类
电工技术 | 1417篇 |
技术理论 | 1篇 |
综合类 | 1014篇 |
化学工业 | 1932篇 |
金属工艺 | 592篇 |
机械仪表 | 1279篇 |
建筑科学 | 1201篇 |
矿业工程 | 453篇 |
能源动力 | 706篇 |
轻工业 | 659篇 |
水利工程 | 575篇 |
石油天然气 | 650篇 |
武器工业 | 102篇 |
无线电 | 772篇 |
一般工业技术 | 1021篇 |
冶金工业 | 854篇 |
原子能技术 | 147篇 |
自动化技术 | 1709篇 |
出版年
2024年 | 39篇 |
2023年 | 135篇 |
2022年 | 251篇 |
2021年 | 337篇 |
2020年 | 365篇 |
2019年 | 283篇 |
2018年 | 272篇 |
2017年 | 336篇 |
2016年 | 428篇 |
2015年 | 452篇 |
2014年 | 801篇 |
2013年 | 763篇 |
2012年 | 935篇 |
2011年 | 1176篇 |
2010年 | 772篇 |
2009年 | 843篇 |
2008年 | 769篇 |
2007年 | 860篇 |
2006年 | 795篇 |
2005年 | 704篇 |
2004年 | 623篇 |
2003年 | 507篇 |
2002年 | 484篇 |
2001年 | 398篇 |
2000年 | 303篇 |
1999年 | 302篇 |
1998年 | 219篇 |
1997年 | 178篇 |
1996年 | 162篇 |
1995年 | 145篇 |
1994年 | 106篇 |
1993年 | 70篇 |
1992年 | 62篇 |
1991年 | 41篇 |
1990年 | 42篇 |
1989年 | 31篇 |
1988年 | 26篇 |
1987年 | 13篇 |
1986年 | 13篇 |
1985年 | 9篇 |
1984年 | 11篇 |
1983年 | 2篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1972年 | 1篇 |
1964年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Lake-Level Change and Water Balance Analysis at Lake Qinghai,West China during Recent Decades 总被引:7,自引:0,他引:7
Xiao-Yan Li He-Ye Xu Yong-Liang Sun Deng-Shan Zhang Zhi-Peng Yang 《Water Resources Management》2007,21(9):1505-1516
Lake Qinghai, the largest saline lake with an area of 4,260 km2 (2000) and average depth of 21 m (1985) in West China, has experienced severe decline in water level in recent decades. This
study aimed to investigate water balance of the lake and identify the causes for the decline in lake level. There was a 3.35-m
decline in water level with an average decreasing rate of 8.0 cm year−1 between 1959 and 2000. The lake water balance showed that mean annual precipitation between 1959 and 2000 over the lake was
357 ± 10 mm, evaporation was 924 ± 10 mm, surface runoff water inflow was 348 ± 21 mm, groundwater inflow was 138 mm ± 9 and
the change in lake level was −80 ± 31 mm. The variation of lake level was highly positively correlated to surface runoff and
precipitation and negatively to evaporation, the correlation coefficients were 0.89, 0.81 and −0.66, respectively. Water consumption
by human activities accounts for 1% of the evaporation loss of the lake, implying that water consumption by human activities
has little effect on lake level decline. Most dramatic decline in lake level occurred in the warm and dry years, and moderate
decline in the cold and dry years, and relatively slight decline in the warm and wet years, therefore, the trend of cold/warm
and dry climate in recent decades may be the main reasons for the decline in lake level. 相似文献
32.
针对某厂金、银总平衡情况,分别采用平衡法和连乘法计算金、银回收率,得出两种不同的结果,文章分析了产生不同结果的原因,探讨不同的企业如何根据自身特点,选择与之相适应的金、银回收率计算方法,以便准确地反映本企业的回收率实际水平。 相似文献
33.
R. Masui 《International Journal of Thermophysics》2002,23(4):921-935
The development of a magnetic suspension densimeter that has been built for measurement of the density of compressed liquid at pressures up to 30 MPa in the temperature range 20 to 150°C is described. The densimeter was first built by the author and his coworkers at NIST. We describe here further improvements made on a second system built at NMIJ based on the same principle. The densimeter uses a small coil suspended from an electronic balance. Within the coil is placed a sample cell in which the pressurized sample and a buoy, which is a permanent magnet, are enclosed. For measurement of density, balance readings are recorded (1) with the buoy at rest and (2) with the buoy in magnetic suspension. The measurement procedure is basically a hydrostatic weighing, which is simpler than those of conventional magnetic densimetry. As an example, measurements of toluene density performed as part of an inter-laboratory comparison are presented. The data agreed with reliable literature values to within a few hundredths of a per cent. 相似文献
34.
用APACHE+PHP+MYSQL实现网站自动更新 总被引:1,自引:0,他引:1
在分析建立自动更新网站必要性的基础上,较详细地说明了如何利用APACHE+PHP+MYSQL工具实现网站自动更新中的权限控制、资料上传、自动更新,并给出了网页的部分源代码. 相似文献
35.
碘量法测铜中物质性质和分析操作 总被引:3,自引:0,他引:3
本文讨论了碘量法测定铜量中一些有关物质的特性,以及这些性质对分析条件和操作的要求。 相似文献
36.
姚新荣 《河南纺织高等专科学校学报》2007,19(3):24-27
2006年2月15日财政部颁布的《企业会计准则》中有多处要求采用实际利率法计算摊余成本和利息,而会计职称考试用书等资料则采用列表形式。本文在分析实际利率法内涵的基础上,通过若干实例解析了利用账簿记录计算各期摊余成本。 相似文献
37.
39.
We investigate the dynamic response, of a generalization of an incompressible Kelvin-Voigt viscoelastic solid, whose viscosity depends on the pressure. Bodies with pressure-dependent material moduli have relevance to numerous technologically significant problems in geomechanics, the mechanics of granular media and powder compaction. We obtain analytical results for creep and recovery phenomena as well as solutions to the propagation of waves in such bodies. We are able to obtain explicit exact solutions that clearly illustrate the marked difference in the response of bodies with pressure-dependent material moduli as opposed to their counterparts whose moduli do not depend on the pressure. We also show that the governing equations for such materials can change type, and that their solutions exhibit singularities and localization. 相似文献
40.
对屏蔽电泵在非设计流量下工作存在较大的轴向力不平衡,造成前端轴承磨损严重进行了分析。在不降低效率的情况下,在屏蔽电泵的泵头加入平衡盘使轴向力得到平衡,并取得了满意的效果。 相似文献