全文获取类型
收费全文 | 36061篇 |
免费 | 2240篇 |
国内免费 | 32篇 |
专业分类
电工技术 | 258篇 |
综合类 | 20篇 |
化学工业 | 7663篇 |
金属工艺 | 719篇 |
机械仪表 | 789篇 |
建筑科学 | 1041篇 |
矿业工程 | 78篇 |
能源动力 | 661篇 |
轻工业 | 5732篇 |
水利工程 | 331篇 |
石油天然气 | 138篇 |
武器工业 | 5篇 |
无线电 | 1345篇 |
一般工业技术 | 6205篇 |
冶金工业 | 8235篇 |
原子能技术 | 163篇 |
自动化技术 | 4950篇 |
出版年
2023年 | 314篇 |
2022年 | 403篇 |
2021年 | 899篇 |
2020年 | 731篇 |
2019年 | 822篇 |
2018年 | 1423篇 |
2017年 | 1377篇 |
2016年 | 1464篇 |
2015年 | 1108篇 |
2014年 | 1424篇 |
2013年 | 2793篇 |
2012年 | 2079篇 |
2011年 | 1963篇 |
2010年 | 1572篇 |
2009年 | 1434篇 |
2008年 | 1379篇 |
2007年 | 1295篇 |
2006年 | 895篇 |
2005年 | 755篇 |
2004年 | 725篇 |
2003年 | 636篇 |
2002年 | 605篇 |
2001年 | 455篇 |
2000年 | 447篇 |
1999年 | 481篇 |
1998年 | 2459篇 |
1997年 | 1709篇 |
1996年 | 1087篇 |
1995年 | 654篇 |
1994年 | 507篇 |
1993年 | 596篇 |
1992年 | 224篇 |
1991年 | 225篇 |
1990年 | 167篇 |
1989年 | 179篇 |
1988年 | 170篇 |
1987年 | 150篇 |
1986年 | 140篇 |
1985年 | 168篇 |
1984年 | 138篇 |
1983年 | 115篇 |
1982年 | 155篇 |
1981年 | 162篇 |
1980年 | 173篇 |
1979年 | 96篇 |
1978年 | 91篇 |
1977年 | 303篇 |
1976年 | 661篇 |
1975年 | 67篇 |
1973年 | 79篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
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
93.
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
94.
M. Polák M. Majoro F. Hanic J. Pitel M. Kedrová P. Kottman J. Talapa L. Vencel 《Journal of Superconductivity》1989,2(2):219-233
A method for contactless measurement of the shielding critical current density and its dependence on the external magnetic field is described and analyzed. The obtained values are compared with those measured resistively on two different samples. It is shown that the shielding critical current densityJ
cs
and the intergranular transport current densityJ
cr
are identical if the measurement conditions are similar. A degradation ofJ
cs
measured in the external field with AC ripple has been observed. 相似文献
95.
A Symbolic Pole/Zero Extraction Methodology Based on Analysis of Circuit Time-Constants 总被引:1,自引:0,他引:1
O. Guerra J. D. Rodríguez-García F. V. Fernández A. Rodríguez-Vázquez 《Analog Integrated Circuits and Signal Processing》2002,31(2):101-118
This paper introduces a methodology for symbolic pole/zero extraction based on the formulation of the time-constant matrix of the circuits. This methodology incorporates approximation techniques specifically devoted to achieve an optimum trade-off between accuracy and complexity of the symbolic root expressions. The capability to efficiently handle even large circuits will be demonstrated through several practical circuits. 相似文献
96.
97.
A one-dimensional mesoscopic ring with one input and two output leads acts as a spintronic beam splitter. The spatial degree of freedom, i.e., the presence of two different possible output channels, gets intertwined with the spin direction as a consequence of quantum interference and spin-orbit interaction. We investigate this kind of spatial-spin correlation, and show that the output density operator contains no quantum entanglement in the important special case when the device polarizes a perfectly random input spin state. However, the correlations are in general not purely classical, we also present specific input states with maximal spatial-spin entanglement after the ring. 相似文献
98.
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
99.
V. Psota I. Boha
enko J. Hartmann M. Budinsk J. Chmelík 《Journal of the Institute of Brewing》2002,108(2):200-203
A newly developed method GFFF (Gravitational Field‐Flow Fractionation) and the well known method LALLS (Low Angle Laser Light Scattering) were used to assess starch granule size distribution of ten varieties of spring barley. As a distribution criterion, the ratio of starch granule content larger than 8 μm (type A) and smaller than 8 μm (type B) was chosen. Both methods divided the observed set in a similar way. Varieties Akcent, Forum and Atribut formed a variety set with the highest ratio of large and small starch granules. Varieties Scarlet and Kompakt had intermediate ratios. The remaining five varieties Amulet, Novum, Olbram, Tolar and Krona had the lowest ratios of large and small starch granules. Statistical analysis showed that there was a highly significant correlation between the GFFF and LALLS methods. 相似文献
100.
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