全文获取类型
收费全文 | 212401篇 |
免费 | 29570篇 |
国内免费 | 10712篇 |
专业分类
电工技术 | 15038篇 |
技术理论 | 4篇 |
综合类 | 14249篇 |
化学工业 | 40550篇 |
金属工艺 | 10869篇 |
机械仪表 | 12442篇 |
建筑科学 | 16079篇 |
矿业工程 | 5663篇 |
能源动力 | 6158篇 |
轻工业 | 20083篇 |
水利工程 | 4551篇 |
石油天然气 | 8397篇 |
武器工业 | 2009篇 |
无线电 | 28123篇 |
一般工业技术 | 28343篇 |
冶金工业 | 7953篇 |
原子能技术 | 1965篇 |
自动化技术 | 30207篇 |
出版年
2024年 | 864篇 |
2023年 | 2815篇 |
2022年 | 5725篇 |
2021年 | 8009篇 |
2020年 | 7103篇 |
2019年 | 7379篇 |
2018年 | 7830篇 |
2017年 | 9140篇 |
2016年 | 8790篇 |
2015年 | 11419篇 |
2014年 | 13438篇 |
2013年 | 16417篇 |
2012年 | 16114篇 |
2011年 | 16344篇 |
2010年 | 15591篇 |
2009年 | 14732篇 |
2008年 | 14151篇 |
2007年 | 13360篇 |
2006年 | 12029篇 |
2005年 | 9497篇 |
2004年 | 7019篇 |
2003年 | 6157篇 |
2002年 | 5893篇 |
2001年 | 5174篇 |
2000年 | 4327篇 |
1999年 | 3085篇 |
1998年 | 1963篇 |
1997年 | 1539篇 |
1996年 | 1373篇 |
1995年 | 1157篇 |
1994年 | 990篇 |
1993年 | 624篇 |
1992年 | 499篇 |
1991年 | 386篇 |
1990年 | 304篇 |
1989年 | 272篇 |
1988年 | 208篇 |
1987年 | 150篇 |
1986年 | 135篇 |
1985年 | 71篇 |
1984年 | 77篇 |
1983年 | 64篇 |
1982年 | 47篇 |
1981年 | 64篇 |
1980年 | 60篇 |
1979年 | 37篇 |
1978年 | 25篇 |
1977年 | 34篇 |
1976年 | 46篇 |
1974年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
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
22.
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
23.
针对有线电视系统工程建设的特点,依照《招标投标法》的规定和程序,对有线电视系统工程招标的种类、招标方式、招标工程必备的条件、标底的编制及审定、开标、评标和中标的原则进行详细介绍,对招标文件的编制进行具体说明。 相似文献
24.
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
25.
26.
T. Choi J.‐H. Jang C.K. Ullal M.C. LeMieux V.V. Tsukruk E.L. Thomas 《Advanced functional materials》2006,16(10)
The probing of the micromechanical properties within a two‐dimensional polymer structure with sixfold symmetry fabricated via interference lithography reveals a nonuniform spatial distribution in the elastic modulus “imprinted” with an interference pattern in work reported by Tsukruk, Thomas, and co‐workers on p. 1324. The image prepared by M. Lemieux and T. Gorishnyy shows how the interference pattern is formed by three laser beams and is transferred to the solid polymer structure. The elastic and plastic properties within a two‐dimensional polymer (SU8) structure with sixfold symmetry fabricated via interference lithography are presented. There is a nonuniform spatial distribution in the elastic modulus, with a higher elastic modulus obtained for nodes (brightest regions in the laser interference pattern) and a lower elastic modulus for beams (darkest regions in the laser interference pattern) of the photopatterned films. We suggest that such a nonuniformity and unusual plastic behavior are related to the variable material properties “imprinted” by the interference pattern. 相似文献
27.
28.
29.
SUNShou-qun ZHAOSan-xing ZHANGWei CHANGXin-long 《国际设备工程与管理》2003,8(2):80-87
The multi-fault phenomena are common in the turbo-rotor system of a liquid rocket engine.As it has many excellent qualities,the neural network might be used to solve the problems of multi-fault diagnasis of a turbo-rotor system.First,the feature expression of a common turbo-rotor fault was studied in order to build up the standard fault pattern and satisfy the need of neural network studying and diagnosing.Then.the turbo-rotor fault identification and diagnosis problems were investigated by using a BP(back-propaga-tion)neural network.According to the BP neural network problems,the parallel BP neural network method of multi-fault diagnosis and classification was presented and investigated.The results indicated that the parallel Bp neural network method could solve the turbo-rotor multi-fault diagnosis problems. 相似文献
30.
Latchup-free ESD protection design with complementary substrate-triggered SCR devices 总被引:2,自引:0,他引:2
Ming-Dou Ker Kuo-Chun Hsu 《Solid-State Circuits, IEEE Journal of》2003,38(8):1380-1392
The turn-on mechanism of silicon-controlled rectifier (SCR) devices is essentially a current triggering event. While a current is applied to the base or substrate of an SCR device, it can be quickly triggered on into its latching state. In this paper, latchup-free electrostatic discharge (ESD) protection circuits, which are combined with the substrate-triggered technique and an SCR device, are proposed. A complementary circuit style with the substrate-triggered SCR device is designed to discharge both the pad-to-V/sub SS/ and pad-to-V/sub DD/ ESD stresses. The novel complementary substrate-triggered SCR devices have the advantages of controllable switching voltage, adjustable holding voltage, faster turn-on speed, and compatible to general CMOS process without extra process modification such as the silicide-blocking mask and ESD implantation. The total holding voltage of the substrate-triggered SCR device can be linearly increased by adding the stacked diode string to avoid the transient-induced latchup issue in the ESD protection circuits. The on-chip ESD protection circuits designed with the proposed complementary substrate-triggered SCR devices and stacked diode string for the input/output pad and power pad have been successfully verified in a 0.25-/spl mu/m salicided CMOS process with the human body model (machine model) ESD level of /spl sim/7.25 kV (500 V) in a small layout area. 相似文献