全文获取类型
收费全文 | 349570篇 |
免费 | 36654篇 |
国内免费 | 14030篇 |
专业分类
电工技术 | 19682篇 |
技术理论 | 23篇 |
综合类 | 21453篇 |
化学工业 | 67336篇 |
金属工艺 | 17042篇 |
机械仪表 | 19737篇 |
建筑科学 | 26610篇 |
矿业工程 | 8011篇 |
能源动力 | 9804篇 |
轻工业 | 30454篇 |
水利工程 | 5857篇 |
石油天然气 | 16283篇 |
武器工业 | 2424篇 |
无线电 | 42837篇 |
一般工业技术 | 46991篇 |
冶金工业 | 15612篇 |
原子能技术 | 3371篇 |
自动化技术 | 46727篇 |
出版年
2024年 | 1360篇 |
2023年 | 4907篇 |
2022年 | 9322篇 |
2021年 | 12597篇 |
2020年 | 10381篇 |
2019年 | 10248篇 |
2018年 | 10894篇 |
2017年 | 12572篇 |
2016年 | 12080篇 |
2015年 | 15260篇 |
2014年 | 18733篇 |
2013年 | 23283篇 |
2012年 | 22538篇 |
2011年 | 24632篇 |
2010年 | 21820篇 |
2009年 | 21125篇 |
2008年 | 20134篇 |
2007年 | 19161篇 |
2006年 | 18998篇 |
2005年 | 16173篇 |
2004年 | 11668篇 |
2003年 | 10472篇 |
2002年 | 10232篇 |
2001年 | 8940篇 |
2000年 | 8274篇 |
1999年 | 8010篇 |
1998年 | 6646篇 |
1997年 | 5453篇 |
1996年 | 4893篇 |
1995年 | 4022篇 |
1994年 | 3326篇 |
1993年 | 2586篇 |
1992年 | 2023篇 |
1991年 | 1529篇 |
1990年 | 1186篇 |
1989年 | 1029篇 |
1988年 | 779篇 |
1987年 | 574篇 |
1986年 | 458篇 |
1985年 | 369篇 |
1984年 | 227篇 |
1983年 | 226篇 |
1982年 | 193篇 |
1981年 | 172篇 |
1980年 | 164篇 |
1979年 | 108篇 |
1978年 | 67篇 |
1977年 | 69篇 |
1976年 | 80篇 |
1973年 | 39篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
A central event in the life of a cellular system is the interaction between the exterior and the interior compartments. Biochemical signals arrive at the cellular surface, bind to their membrane bound receptor followed by a conformational change triggering the release of an internal chemical or electrical signal.This basic principle is followed by all our perceptive abilities like sense of smell or taste, but also by different signal transduction pathways involved in nerve conductivity, vision, sense of touch or hearing. To follow and mimic this principle of parallel registration is one of the aims of modern nanobiotechnology. If we are able to specifically biofunctionalize small arrays of a solid surface, which could be an electrode or a semiconductor, this approach will enable us to build up devices called “biochips” or “biosensors” that allow the determination of bioactive molecules with high specificity at lowest concentrations. Potential pharmacological active substrates might be screened as well as new receptors may be determined. Applications in genomics as well as proteomics are realistic. The major prerequisite for such a broad spectrum of applications is the fabrication of receptive surfaces. Biomolecules have to be surface‐adsorbed in a highly reproducible, oriented and well organised fashion, a task which in biology is taken by the cellular membranes as external or internal receptive surfaces. The physical principles like hydrogen bonds, electrostatic or hydrophobic interactions that lead to such an organized surface are well known. To synthesize molecular building blocks and to position them onto an otherwise unspecific surface is one of the challenges of nanobiotechnology combining biological knowledge and chemical skills with biophysical techniques that allow to handle or analyze even single molecules. 相似文献
42.
43.
燕善敏 《徐州工程学院学报》2003,(6)
行政法学的研究应该尽量放宽视角,适应将来法治建设的需要。我们必须把行政行为的概念放到整个法治体系中甚至整个社会的发展中去研究。 相似文献
44.
From its foundation until 2004, ETRI has registered over 1,000 US patents. This letter analyzes the characteristics of these patents and addresses the explanatory factors affecting their citation counts. For explanatory variables, research team related variables, invention specific variables, and geographical domain related variables are suggested. Zero‐altered count data models are used to test the impact of independent variables. A key finding is that technological cumulativeness, the scale of invention, outputs in the electronic field, and the degree of dependence on the US technology domain positively affect the citation counts of ETRI‐invented US patents. The magnitude of international presence appears to negatively affect the citation counts of ETRI‐invented US patents. 相似文献
45.
为确保特殊时期党政军指挥通信畅通,充分利用中国移动现网资源,将卫星通信与地面光缆、微波传榆。以及移动网络无缝衔接,共同构建中国移动天地一体应急通信平台。 相似文献
46.
TD-SCDMA直放站对网络性能的影响 总被引:1,自引:0,他引:1
TD-SCDMA直放站是用于TD-SCDMA移动通信网的全双工、线性射频放大设备.介绍了TD直放站不同于其它系统的同步的时分双工模式特点,并讨论了TD-SCDMA直放站的引入可能对网络性能造成的影响及其解决方法。 相似文献
47.
论文将Fermat素性检验的思想运用于不可约多项式的判断,给出了一个对于不可约判断问题的Monte Carlo 算法,分析了该算法的计算复杂度问题,并且给出了次数在200以内的检验结果。 相似文献
48.
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
49.
A route to synthesize ZSM‐5 crystals with a bimodal micro/mesoscopic pore system has been developed in this study; the successful incorporation of the mesopores within the ZSM‐5 structure was performed using tetrapropylammonium hydroxide (TPAOH)‐impregnated mesoporous materials containing carbon nanotubes in the pores, which were encapsulated in the ZSM‐5 crystals during a solid rearrangement process within the framework. Such mesoporous ZSM‐5 zeolites can be readily obtained as powders, thin films, or monoliths. 相似文献
50.
The hydrogenated poly-silicon germanium (poly-SiGe:H) epitaxial film has been investigated using gold-induced lateral crystallization (Au-ILC) technology on a-SiGe:H layers at 10-h 350/spl deg/C annealing temperature and 60-sccm hydrogen (H/sub 2/) content. Using this optimal condition, the growth rate of the induced Au was as large as 15.9 /spl mu/m/h. With a low annealing temperature (/spl les/400/spl deg/C) and large growth rate, this novel technology will be noticeably useful for poly-SiGe:H pin IR-sensing fabrication on a conventional precoated indium tin oxide (ITO)-glass substrate. Under a 1-/spl mu/W IR-LED incident light (with peak wave length at 710 nm) and at a 5-V biased voltage, the poly-SiGe:H pin IR sensor developed by the Au-ILC technology, i.e., an Al (anode)/n poly-SiGe:H/i poly-SiGe:H/p poly-SiGe:H/ITO (cathode)/glass-substrate structure allowed for maximum optical gain and response speed. The optical gains and the response speeds were almost 600 and 130%, respectively, better than that of a traditional pin type. Meanwhile, the FWHM of a poly-SiGe:H pin sensor with Au-ILC technology was reduced from 280 to 150 nm. This reveals excellent IR-sensing selectivity. These IR-sensing trials demonstrated again that the proposed Au-ILC technology has very useful application in the field of low cost integrated circuits on optoelectronic applications. 相似文献