首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   9918篇
  免费   1027篇
  国内免费   571篇
电工技术   984篇
技术理论   1篇
综合类   691篇
化学工业   1191篇
金属工艺   678篇
机械仪表   538篇
建筑科学   479篇
矿业工程   280篇
能源动力   303篇
轻工业   818篇
水利工程   209篇
石油天然气   278篇
武器工业   84篇
无线电   1195篇
一般工业技术   829篇
冶金工业   1630篇
原子能技术   105篇
自动化技术   1223篇
  2024年   63篇
  2023年   178篇
  2022年   423篇
  2021年   500篇
  2020年   350篇
  2019年   255篇
  2018年   271篇
  2017年   317篇
  2016年   275篇
  2015年   395篇
  2014年   482篇
  2013年   597篇
  2012年   708篇
  2011年   629篇
  2010年   562篇
  2009年   593篇
  2008年   659篇
  2007年   567篇
  2006年   463篇
  2005年   348篇
  2004年   308篇
  2003年   229篇
  2002年   234篇
  2001年   205篇
  2000年   143篇
  1999年   98篇
  1998年   374篇
  1997年   265篇
  1996年   190篇
  1995年   117篇
  1994年   80篇
  1993年   92篇
  1992年   37篇
  1991年   41篇
  1990年   24篇
  1989年   22篇
  1988年   27篇
  1987年   29篇
  1986年   18篇
  1985年   20篇
  1984年   8篇
  1983年   12篇
  1982年   14篇
  1981年   17篇
  1980年   26篇
  1979年   6篇
  1978年   6篇
  1977年   64篇
  1976年   139篇
  1975年   10篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
本文介绍了柳钢冷轧板带厂1550 mm单机架平整机机前甩尾轧制的工艺。改进前轧制每卷钢卷生产效率低,钢卷成材率低,改进后生产效率、成材率明显提高,部分规格的钢卷能实现带尾剪切长度为零。  相似文献   
3.
Geosynthetic clay liners (GCLs), which have a very low permeability to water and a considerably high self-healing capacity, are widely used in liner systems of landfills. In this study, a series of experimental tests were carried out under complex conditions on typical commercial GCLs from China. In particular, the effects of pH values and lead ions (Pb2+) were tested in addition to other factors. The swelling properties of natural bentonite encapsulated between geotextile components in the GCLs were tested first. The swelling capacity was reduced rapidly at pH values < 3 and concentrations of Pb2+ >40 mM. Permeability tests on GCLs with different concentrations of lead ions were then performed by using the self-developed multi-link flexible wall permeameter, and data showed that increases in lead ion concentrations greatly improved the permeability. Finally, self-healing capacity tests were conducted on needle-punched GCLs under different levels of damage. Results showed that the GCLs have a good self-healing capacity with small diameter damage holes (2 mm, close to three times the original aperture), but with a damage aperture larger than 15% of the sample area, the self-healing capacity could not prevent leakage; hence, in certain situations it will be necessary to repair the damage to meet the anti-seepage requirement.  相似文献   
4.
5.
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   
6.
The generation-over-generation scaling of critical CMOS technology parameters is ultimately bound by nonscalable limitations, such as the thermal voltage and the elementary electronic charge. Sustained improvement in performance and density has required the introduction of new device structures and materials. Partially depleted SOI, a most recent MOSFET innovation, has extended VLSI performance while introducing unique idiosyncrasies. Fully depleted SOI is one logical extension of this device design direction. Gate dielectric tunneling, device self-heating, and single-event upsets present developers of these next-generation devices with new challenges. Strained silicon and high-permittivity gate dielectric are examples of new materials that will enable CMOS developers to continue to deliver device performance enhancements in the sub-100 nm regime.  相似文献   
7.
在编制遥测数据处理软件的过程中,面对大量的测试数据,经常需要编写高效率的数据过滤器。本文讨论了一种通过采用跨单元、跨类访问Delphi类的私有域的方法实现快速删除TList批连续结点的新算法,并通过测试结果得到验证。  相似文献   
8.
分别利用Ga2O3粉末和Ga2O3凝胶作为Ga源,采用NH3为N源,在950℃下,分别将两种反应物与流动的NH3反应20 min合成了GaN微晶。用X射线衍射(XRD)、扫描电子显微镜(SEM)、选择区电子衍射(SAED)对微晶进行结构、形貌的分析,特别是对两种不同途径合成GaN微晶的XRD进行了分析比较。结果表明,当Ga源温度为950℃时两种不同的合成途径均可得到六方纤锌矿结构的GaN单晶颗粒,在氮化温度为850℃和900℃时,利用Ga2O3粉末作为Ga源,仅有少量的Ga2O3转变为GaN;而采用Ga2O3凝胶作为Ga源,在相同的温度下,大部分凝胶经过高温氨化反应均可转化为GaN。  相似文献   
9.
许参  艾晓辉  王超 《电子器件》2003,26(2):122-124
设计了GMSK(Gauss Minimum Shift Keying,高斯最小频移键控)无线接收终端的硬件与软件系统。硬件的射频电路对空中信号进行接收与滤波,再由以MX589构成的解调模块解调,输出数字信号;数字硬件以单片机GMS97L5为核心。软件系统设计了对IC卡AT88SCl608加密卡的认证以及对串行数据的接收与处理的中断程序。终端系统接收数据快、性能稳定。  相似文献   
10.
A novel InP/InGaAs tunneling emitter bipolar transistor (TEBT) is fabricated and demonstrated. The studied device exhibits a very small collector-emitter offset voltage of 40 mV and an extremely wide operation regime. The operation region is larger than 11 decades in magnitude of collector current (10/sup -12/ to 10/sup -1/A). A current gain of 3 is obtained even if the device is operated at an ultralow collector current of 3.9 /spl times/ 10/sup -12/A (1.56 /spl times/ 10/sup -7/A/cm/sup 2/). Furthermore, the common-emitter breakdown voltage of the studied device is higher than 2 V. Consequently, the studied device shows a promise for low supply voltage, and low-power consumption circuit applications.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号