全文获取类型
收费全文 | 50868篇 |
免费 | 3504篇 |
国内免费 | 389篇 |
专业分类
电工技术 | 868篇 |
综合类 | 519篇 |
化学工业 | 10586篇 |
金属工艺 | 1165篇 |
机械仪表 | 1405篇 |
建筑科学 | 1887篇 |
矿业工程 | 273篇 |
能源动力 | 1165篇 |
轻工业 | 8183篇 |
水利工程 | 527篇 |
石油天然气 | 501篇 |
武器工业 | 69篇 |
无线电 | 2970篇 |
一般工业技术 | 8465篇 |
冶金工业 | 8948篇 |
原子能技术 | 250篇 |
自动化技术 | 6980篇 |
出版年
2024年 | 121篇 |
2023年 | 518篇 |
2022年 | 718篇 |
2021年 | 1407篇 |
2020年 | 1153篇 |
2019年 | 1254篇 |
2018年 | 1848篇 |
2017年 | 1888篇 |
2016年 | 2043篇 |
2015年 | 1699篇 |
2014年 | 2209篇 |
2013年 | 3996篇 |
2012年 | 3240篇 |
2011年 | 3082篇 |
2010年 | 2527篇 |
2009年 | 2290篇 |
2008年 | 2258篇 |
2007年 | 2118篇 |
2006年 | 1600篇 |
2005年 | 1368篇 |
2004年 | 1172篇 |
2003年 | 1062篇 |
2002年 | 1064篇 |
2001年 | 826篇 |
2000年 | 736篇 |
1999年 | 720篇 |
1998年 | 2681篇 |
1997年 | 1873篇 |
1996年 | 1196篇 |
1995年 | 791篇 |
1994年 | 620篇 |
1993年 | 684篇 |
1992年 | 275篇 |
1991年 | 267篇 |
1990年 | 195篇 |
1989年 | 199篇 |
1988年 | 198篇 |
1987年 | 158篇 |
1986年 | 139篇 |
1985年 | 168篇 |
1984年 | 158篇 |
1983年 | 119篇 |
1982年 | 158篇 |
1981年 | 174篇 |
1980年 | 179篇 |
1979年 | 107篇 |
1978年 | 92篇 |
1977年 | 294篇 |
1976年 | 645篇 |
1973年 | 81篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
R Herruzo-Cabrera L Malo-González ME Calle Purón MJ Vizcaíno-Alcaide J Del Rey-Calero 《Canadian Metallurgical Quarterly》1993,9(4):442-446
A cross-sectional study was performed to obtain risk factors for hepatitis B disease, HBsAg carriers and immunised personnel, among 2470 workers in a general hospital in Madrid, Spain. The data obtained were analyzed with multiple logistic regression to obtain beta coefficients for variables. The results of the analysis show that being a nurse or being regularly exposed to blood are the most important risk factors for hepatitis B acquisition. The length of time working at the same job activity was also a risk factor. The resulting beta coefficients allow the construction for a hepatitis non-immunised, HBsAg carrier and immunised HBV status, which can select subjects for a hepatitis B vaccination program. 相似文献
42.
Generation of Technology-Independent Retargetable Analog Blocks 总被引:1,自引:0,他引:1
R. Castro-López F. V. Fernández F. Medeiro A. Rodríguez-Vázquez 《Analog Integrated Circuits and Signal Processing》2002,33(2):157-170
This paper introduces a complete methodology for retargeting of analog cells to different sets of specifications. This methodology is technology-independent, thus allowing the migration, from one technology to another, of the circuit under retargeting. Careful integration of the device sizing and layout generation tasks via the incorporation of layout constraints during the sizing process allows to generate fully functional designs in a few minutes. The methodology is illustrated via the retargeting of a fully-differential Miller-compensated two-stage operational amplifier for a new set of specifications and two different technological processes.An erratum to this article can be found at 相似文献
43.
Astrid Labidi Marie-Christine Salon Alessandro Gandini Hervé Cheradame 《Polymer Bulletin》1985,14(3-4):271-278
Summary 2-Furyl vinyl ketone was polymerised using anionic, cationic and free-radical initiators. Yields and molecular weights varied with the type of activation. Whereas radical polymerisation gave a product possessing a regular vinylic structure, other kinds of units were detected in the polymers prepared with anionic and cationic catalysts. 相似文献
44.
45.
We determine the exact power of two-prover interactive proof systems introduced by Ben-Or, Goldwasser, Kilian, and Wigderson (1988). In this system, two all-powerful noncommunicating provers convince a randomizing polynomial time verifier in polynomial time that the inputx belongs to the languageL. We show that the class of languages having tow-prover interactive proof systems is nondeterministic exponential time.We also show that to prove membership in languages inEXP, the honest provers need the power ofEXP only.The first part of the proof of the main result extends recent techniques of polynomial extrapolation used in the single prover case by Lund, Fortnow, Karloff, Nisan, and Shamir.The second part is averification scheme for multilinearity of a function in several variables held by an oracle and can be viewed as an independent result onprogram verification. Its proof rests on combinatorial techniques employing a simple isoperimetric inequality for certain graphs: 相似文献
46.
We compare two link analysis ranking methods of web pages in a site. The first, called Site Rank, is an adaptation of PageRank to the granularity of a web site and the second, called Popularity Rank, is based on the frequencies of user clicks on the outlinks in a page that are captured by navigation sessions of users through
the web site. We ran experiments on artificially created web sites of different sizes and on two real data sets, employing
the relative entropy to compare the distributions of the two ranking methods. For the real data sets we also employ a nonparametric
measure, called Spearman's footrule, which we use to compare the top-ten web pages ranked by the two methods. Our main result
is that the distributions of the Popularity Rank and Site Rank are surprisingly close to each other, implying that the topology
of a web site is very instrumental in guiding users through the site. Thus, in practice, the Site Rank provides a reasonable
first order approximation of the aggregate behaviour of users within a web site given by the Popularity Rank. 相似文献
47.
Various influence diagnostics in Multiple Discriminant Analysis can be found in the literature. Almost all of them are based
on the overall probability of misclassification. Two case-deletion diagnostics which evaluate the effect of the omission on
the linear functions which determine Fisher’s Linear Discriminant Rule are proposed in this paper. Both measures are based
on the L
2-norm: The first diagnostic is calculated from the data set and the second diagnostic is calculated in the minimum hypercube
which covers it. 相似文献
48.
49.
Intraseptal scopolamine has differential effects on Pavlovian eye blink and heart rate conditioning.
Evaluated the effects of intraseptal scopolamine hydrobromide (40 μg) injections on Pavlovian (classical) conditioning, with tones used as the CS and a periorbital electric shock train as the UCS, using New Zealand albino rabbits. Eyeblink (EB) and heart rate (HTR) CRs were concomitantly recorded. Although injections of scopolamine into the medial septum impaired the acquisition of the Pavlovian conditioned eyelid reflex, these injections enhanced the magnitude of accompanying Pavlovian conditioned HTR decelerations. However, scopolamine applied to the lateral septal area had no effect on EB conditioning, relative to the vehicle; like medial injections, scopolamine also enhanced the magnitude of the accompanying HTR decelerations. Results are compatible with those of previous investigations indicating that medial septal dysfunction impairs somatomotor conditioning but leaves autonomic conditioning intact and that septal dysfunction produces a parasympathetic bias of the cardiovascular system. (49 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
50.
The transmission mode of holographic polymer‐dispersed liquid crystals (HPDLCs) was developed an under electric field. It is reported that orientation of LC molecules under an electric field induces orientation of oligomer molecules giving rise to low off‐state diffraction and small grating shrinkage. Copyright © 2005 Society of Chemical Industry 相似文献