首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2463篇
  免费   108篇
  国内免费   1篇
电工技术   91篇
综合类   7篇
化学工业   577篇
金属工艺   109篇
机械仪表   27篇
建筑科学   105篇
矿业工程   13篇
能源动力   62篇
轻工业   186篇
水利工程   20篇
石油天然气   5篇
无线电   288篇
一般工业技术   421篇
冶金工业   368篇
原子能技术   16篇
自动化技术   277篇
  2023年   25篇
  2022年   48篇
  2021年   46篇
  2020年   41篇
  2019年   48篇
  2018年   46篇
  2017年   46篇
  2016年   54篇
  2015年   38篇
  2014年   76篇
  2013年   144篇
  2012年   119篇
  2011年   133篇
  2010年   80篇
  2009年   75篇
  2008年   110篇
  2007年   90篇
  2006年   83篇
  2005年   89篇
  2004年   61篇
  2003年   73篇
  2002年   58篇
  2001年   48篇
  2000年   40篇
  1999年   29篇
  1998年   81篇
  1997年   43篇
  1996年   50篇
  1995年   30篇
  1994年   39篇
  1993年   33篇
  1992年   26篇
  1991年   32篇
  1990年   33篇
  1989年   30篇
  1988年   17篇
  1987年   23篇
  1986年   26篇
  1985年   25篇
  1984年   21篇
  1983年   23篇
  1982年   25篇
  1981年   16篇
  1980年   32篇
  1979年   16篇
  1977年   16篇
  1976年   23篇
  1975年   18篇
  1973年   24篇
  1972年   19篇
排序方式: 共有2572条查询结果,搜索用时 31 毫秒
1.
We propose a standardization procedure that provides a convenient, quantitative and reproducible laboratory-based method for measuring the state of polarization (SOP) fluctuations produced by polarization varying devices. This method is based on the SOP distributions generated by commercial polarization scramblers. We show that these devices generate distributions of the maximum change of the SOP (in a given sample time) that follow Rayleigh statistics, which scale linearly with scrambling frequency and the sample time. We use this procedure to measure the SOP fluctuations in a short length of coiled fiber subject to mechanical perturbations.  相似文献   
2.
3.
Defect equilibria for binary semiconducting compound phases which exhibit ionized native donor and acceptor defects were considered, and equations describing the pressure-temperature-composition relationships for these compound phases were derived. These equations were used to analyze experimental data from the literature for tin telluride. Excellent agreement was obtained between calculated thermodynamic and phase boundary values and experimental data. The approach presented is readily extended to obtain equations for the thermodynamic properties of ternary and higher order semiconducting compound phases.  相似文献   
4.
Egghe  Leo 《Scientometrics》2004,60(3):497-509
We show that the composition of two information production processes (IPPs), where the items of the first IPP are the sources of the second, and where the ranks of the sources in the first IPP agree with the ranks of the sources in the second IPP, yields an IPP which is positively reinforced with respect to the first IPP. This means that the rank-frequency distribution of the composition is the composition of the rank-frequency distribution of the first IPP and an increasing function φ, which is explicitly calculable from the two IPPs' distributions. From the rank-frequency distribution of the composition, we derive its size-frequency distribution in terms of the size-frequency distribution of the first IPP and of the function φ. The paper also relates the concentration of the reinforced IPP to that of the original one. This theory solves part of the problem of the determination of a third IPP from two given ones (so-called three-dimensional informetrics). In this paper we solved the “linear” case, i.e., where the third IPP is the composition of the other two IPPs. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   
5.
Safety, local and systemic immunomodulation, and tumor response to treatment with aerosolized natural interleukin 2 (nIL-2) applied five times a day were studied in a Phase I trial in 16 patients with pulmonary malignancies refractory to conventional therapy. The toxicity of inhaled nIL-2 was different from that observed after systemic administration. Reversible airway irritation causing a nonproductive cough represented the dose-limiting toxicity. Mild to moderate reduction of the vital capacity and forced expiratory volume (FEV1) with minor effects on relative FEV1, peak expiratory flow, airway resistance, and PaO2 was experienced by individual patients. In 14 patients suffering from pulmonary metastases due to renal cell cancer, one durable complete response, one partial response, and one mixed response were observed. Inhalation of nIL-2 aerosol resulted in a dose-dependent expansion of pulmonary immunocompetent cells in bronchoalveolar lavage fluid. Posttreatment bronchoalveolar lavage showed an activated lymphocyte phenotype with increased HLA-DR expression. The only systemic biological effect detectable in peripheral blood was a marked increase of soluble interleukin 2 receptor serum levels. We conclude that treatment with aerosolized nIL-2 is an effective means for site-specific immunomodulation and deserves further investigation for the treatment of malignant and inflammatory lung disease.  相似文献   
6.
Leo Egghe 《Scientometrics》2005,63(2):277-296
Summary We study new and existing data sets which show that growth rates of sources usually are different from growth rates of items. Examples: references in publications grow with a rate that is different (usually higher) from the growth rate of the publications themselves; article growth rates are different from journal growth rates and so on. In this paper we interpret this phenomenon of “disproportionate growth' in terms of Naranan's growth model and in terms of the self-similar fractal dimension of such an information system, which follows from Naranan's growth model. The main part of the paper is devoted to explain disproportionate growth. We show that the “simple' 2-dimensional informetrics models of source-item relations are not able to explain this but we also show that linear 3-dimensional informetrics (i.e. adding a new source set) is capable to model disproportionate growth. Formulae of such different growth rates are presented using Lotkaian informetrics and new and existing data sets are presented and interpreted in terms of the used linear 3-dimensional model.  相似文献   
7.
This paper addresses one of the central problems arising at the transfer stage in machine translation: syntactic mismatches, that is, mismatches between a source-language sentence structure and its equivalent target-language sentence structure. The level at which we assume the transfer to be carried out is the Deep-Syntactic Structure (DSyntS) as proposed in the Meaning-Text Theory (MTT). DSyntS is abstract enough to avoid all types of divergences that result either from restricted lexical co-occurrence or from surface-syntactic discrepancies between languages. As for the remaining types of syntactic divergences, all of them occur not only interlinguistically, but also intralinguistically; this means that establishing correspondences between semantically equivalent expressions of the source and target languages that diverge with respect to their syntactic structure is nothing else than paraphrasing. This allows us to adapt the powerful intralinguistic paraphrasing mechanism developed in MTT for purposes of interlinguistic transfer.  相似文献   
8.
A high-sensitivity flat-coil inductive proximity sensor microsystem has been realized and successfully tested. The flat coil, made with CMOS-compatible post processes, is connected to a versatile differential relaxation oscillator electronic interface. In this new and simple interface, the excitation, the signal extraction and amplification are assured by only one operational amplifier. Experimental results on the microsystem confirm that large output frequency variations occur when a metallic target approaches the sensor.  相似文献   
9.
10.
Equal Strain Consolidation by Vertical Drains   总被引:1,自引:0,他引:1  
This paper shows the development of a series of closed-form solutions of equal strain consolidation in the presence of a vertical drain with smear and well resistance. Using an approach that considers the effects of both the radial and vertical drainage in a fully coupled fashion, solutions are obtained for the excess pore pressure and the degree of consolidation in the compressible soil subjected to a step- or ramp-loading situation. The closed-form solutions in the present paper may be evaluated in an electronic spreadsheet on a standard personal computer.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号