全文获取类型
收费全文 | 3237篇 |
免费 | 149篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 59篇 |
综合类 | 6篇 |
化学工业 | 798篇 |
金属工艺 | 81篇 |
机械仪表 | 75篇 |
建筑科学 | 181篇 |
矿业工程 | 4篇 |
能源动力 | 124篇 |
轻工业 | 247篇 |
水利工程 | 9篇 |
石油天然气 | 2篇 |
无线电 | 298篇 |
一般工业技术 | 640篇 |
冶金工业 | 393篇 |
原子能技术 | 20篇 |
自动化技术 | 453篇 |
出版年
2022年 | 34篇 |
2021年 | 54篇 |
2020年 | 34篇 |
2019年 | 50篇 |
2018年 | 54篇 |
2017年 | 75篇 |
2016年 | 77篇 |
2015年 | 80篇 |
2014年 | 105篇 |
2013年 | 157篇 |
2012年 | 132篇 |
2011年 | 206篇 |
2010年 | 121篇 |
2009年 | 145篇 |
2008年 | 155篇 |
2007年 | 152篇 |
2006年 | 140篇 |
2005年 | 118篇 |
2004年 | 103篇 |
2003年 | 101篇 |
2002年 | 76篇 |
2001年 | 72篇 |
2000年 | 68篇 |
1999年 | 59篇 |
1998年 | 141篇 |
1997年 | 92篇 |
1996年 | 100篇 |
1995年 | 52篇 |
1994年 | 53篇 |
1993年 | 43篇 |
1992年 | 40篇 |
1991年 | 32篇 |
1990年 | 27篇 |
1989年 | 34篇 |
1988年 | 29篇 |
1987年 | 16篇 |
1986年 | 27篇 |
1985年 | 30篇 |
1984年 | 27篇 |
1983年 | 23篇 |
1982年 | 16篇 |
1981年 | 23篇 |
1980年 | 16篇 |
1979年 | 21篇 |
1978年 | 23篇 |
1977年 | 24篇 |
1976年 | 26篇 |
1974年 | 12篇 |
1973年 | 12篇 |
1970年 | 13篇 |
排序方式: 共有3390条查询结果,搜索用时 15 毫秒
1.
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
2.
A comparison between different PMD compensation techniques 总被引:17,自引:0,他引:17
Sunnerud H. Chongjin Xie Karlsson M. Samuelsson R. Andrekson P.A. 《Lightwave Technology, Journal of》2002,20(3):368-378
We quantify the benefits of using different techniques for compensation of polarization mode dispersion (PMD) in fiber-optic communication systems by means of numerical simulations. This is done both with respect to PMD-induced pulse broadening and in terms of system outage probability for different data formats [nonreturn-to-zero (NRZ) and return-to-zero (RZ)]. Attention is focused on simple and relevant single- and double-stage post-transmission compensators with a few degrees of freedom (DOF). It is generally believed that a PMD compensator with a polarization controller and a variable delay line can only compensate the PMD to the first order. We show, from analytical results, the counterintuitive fact that this scheme can also partially compensate for higher order PMD. We also investigate the benefit of using a polarizer as compensation element where the optical average power can be used as a feedback signal 相似文献
3.
4.
5.
Dr. V. Recina Dr. D. Lundström B. Karlsson 《Metallurgical and Materials Transactions A》2002,33(9):2869-2881
The influence of chemical composition on the microstructure of the γ-titanium aluminide alloy Ti-48Al-2W-0.5Si (at. pct) and the accompanying tensile, low-cycle fatigue, and creep properties
has been evaluated. The study showed that small variations in chemical composition and casting procedures resulted in considerable
variations in the microstructure, yielding vastly different mechanical properties. Low contents of aluminum and tungsten led
to a coarse-grained lamellar (γ/α
2) microstructure with high creep resistance. A composition close to the nominal one produced a duplex (γ+γ/α
2) structure with favorable strength, ductility, and low-cycle fatigue properties. By controlling the solidification and cooling
rates at casting, a pseudoduplex (PS-DP) microstructure with a unique combination of high strength and high fatigue and creep
resistance can be obtained. These unique properties can be explained by the diffuse boundaries between the relatively small
γ grains and the neighboring lamellar colonies, combined with semicoherent interfaces between the γ and α
2 phases. At tensile and low-cycle fatigue loading, these boundaries act like high-angle boundaries, producing a virtually
fine-grained material promoting strength, whereas at creep loading, grain-boundary sliding is hindered in the semicoherent
interfaces leading to high creep resistance. 相似文献
6.
Joachim Schummer 《Scientometrics》2007,70(3):669-692
Based on bibliometric methods, this paper describes the global institutionalization of nanotechnology research from the mid-1980s
to 2006. Owing to an extremely strong dynamics, the institutionalization of nanotechnology is likely to surpass those of major
disciplines in only a few years. A breakdown of the relative institutionalizations strengths by the main geographical regions,
countries, research sectors, disciplines, and institutional types provides a very diverse picture over the time period because
of different national science policies. The results allow a critical assessment of the different science policies based on
the relative institutionalizations strengths as well as the conclusion that the institutionalization process has run out of
control of individual governments who once induced the development. 相似文献
7.
8.
Multilayer calculations by conventional matrix methods for dielectricum/noble metal/dielectricum systems on glass have been performed. The aim has been to maximize the integrated parameters for solar transmission, Tsol, and transmission of visible light, Teye We have found that Ag is superior for maximizing the transmittance over the narrow visible wavelength range owing to the low internal absorptance. When solar energy transmission is considered multilayers based on Au are the best choice for metal film thicknesses above 15 nm. For thinner films, Ag is still to be preferred. 相似文献
9.
10.