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   507篇
  免费   9篇
  国内免费   1篇
电工技术   5篇
综合类   2篇
化学工业   74篇
金属工艺   21篇
机械仪表   12篇
建筑科学   8篇
能源动力   22篇
轻工业   34篇
水利工程   2篇
石油天然气   3篇
无线电   71篇
一般工业技术   87篇
冶金工业   62篇
原子能技术   7篇
自动化技术   107篇
  2024年   2篇
  2023年   11篇
  2022年   11篇
  2021年   35篇
  2020年   31篇
  2019年   20篇
  2018年   28篇
  2017年   16篇
  2016年   21篇
  2015年   10篇
  2014年   16篇
  2013年   24篇
  2012年   16篇
  2011年   23篇
  2010年   22篇
  2009年   16篇
  2008年   18篇
  2007年   21篇
  2006年   11篇
  2005年   8篇
  2004年   5篇
  2003年   6篇
  2002年   1篇
  2001年   9篇
  2000年   5篇
  1999年   6篇
  1998年   18篇
  1997年   11篇
  1996年   12篇
  1995年   12篇
  1994年   5篇
  1993年   9篇
  1992年   3篇
  1990年   5篇
  1989年   5篇
  1988年   3篇
  1987年   2篇
  1986年   6篇
  1985年   6篇
  1984年   2篇
  1983年   2篇
  1982年   1篇
  1981年   2篇
  1980年   2篇
  1978年   4篇
  1977年   3篇
  1976年   4篇
  1975年   2篇
  1974年   2篇
  1973年   4篇
排序方式: 共有517条查询结果,搜索用时 15 毫秒
91.
Electrozone sensing is a rapid and effective method that has been widely used for particle size analysis. This method is based on the Coulter principle, which provides a measure of the solid volume of particles. However, for wastewater particles, due to the high porosity of these particles, the measured Coulter size is significantly less than the physical dimension of these particles. To quantify this effect, the size distribution curves of the sieved wastewater particles were measured using the Coulter particle sizing method, microscopy technique, and sieving methods. A theoretical model was developed by accounting for the porosity of wastewater particles to correlate the physical size of these particles to Coulter size measurement. However, this theoretical model underestimated the size of wastewater particles smaller than 100 μm. Instead, the wastewater particles size (D) for both primary and activated sludge samples was found to be linearly related to the Coulter particle size measurement (d) according to: D = 2.14d with r2 = 0.98.  相似文献   
92.
Tandem mass spectrometry is the prevailing approach for large-scale peptide sequencing in high-throughput proteomic profiling studies. Effective database search engines have been developed to identify peptide sequences from MS/MS fragmentation spectra. Since proteins are polymorphic and subject to post-translational modifications (PTM), however, computational methods for detecting unanticipated variants are also needed to achieve true proteome-wide coverage. Different from existing "unrestrictive" search tools, we present a novel algorithm, termed SIMS (for Sequential Motif Interval Search), that interprets pairs of product ion peaks, representing potential amino acid residues or "intervals", as a means of mapping PTMs or substitutions in a blind database search mode. An effective heuristic software program was likewise developed to evaluate, rank, and filter optimal combinations of relevant intervals to identify candidate sequences, and any associated PTM or polymorphism, from large collections of MS/MS spectra. The prediction performance of SIMS was benchmarked extensively against annotated reference spectral data sets and compared favorably with, and was complementary to, current state-of-the-art methods. An exhaustive discovery screen using SIMS also revealed thousands of previously overlooked putative PTMs in a compendium of yeast protein complexes and in a proteome-wide map of adult mouse cardiomyocytes. We demonstrate that SIMS, freely accessible for academic research use, addresses gaps in current proteomic data interpretation pipelines, improving overall detection coverage, and facilitating comprehensive investigations of the fundamental multiplicity of the expressed proteome.  相似文献   
93.
94.
Arthritis, most notably rheumatoid arthritis, can destroy the surfaces of the bones; the ideal solution for this is T JR (total joint replacement), which would restore joint functionality, maintain correct aesthetics and eradicate pain for the patient. Current metacarpophalangeal TJR do not provide the normal biomechanical range of motion and functionality. The proposed design attempts to correct this through the use of design geometry and functional anatomy. Numerical analysis is used in conjunction with computational solid modeling to compare a one-piece silicone implant with the proposed T JR. Peak stresses during flexion for the proposed design did not exceed 1.2 MPa, where as soft implants approach 100 MPa to 1,000 MPa for peak stress values. The proposed design, due to high stress tolerances with low deformation, along with functionality and biomechanics, seems to be an appropriate replacement for one-piece silicone implant.  相似文献   
95.
96.
The data on safety investigation of product "Rialam", which is proposed as biologically active food supplement are presented. Chronic experiment and single generation experiment were made on Wistar rats. It is shown that diet "Rialam" in dose 100 mg/kg of body weight didn't influence negatively on growth and development of rats blood parameters, immune status, internal organs morphology, metabolism, hadn't embryotoxic, gonadotoxic and teratogenic action.  相似文献   
97.
In this paper an extension of Weibull theory by the introduction of a statistical length scale is presented. The classical Weibull strength theory is self-similar; a feature that can be illustrated by the fact that the strength dependence on structural size is a power law (a straight line on a double logarithmic graph). Therefore, the theory predicts unlimited strength for extremely small structures. In the paper, it is shown that such a behavior is a direct implication of the assumption that structural elements have independent random strengths. By the introduction of statistical dependence in the form of spatial autocorrelation, the size dependent strength becomes bounded at the small size extreme. The local random strength is phenomenologically modeled as a random field with a certain autocorrelation function. In such a model, the autocorrelation length plays the role of a statistical length scale. The focus is on small failure probabilities and the related probabilistic distributions of the strength of composites. The theoretical part is followed by applications in fiber bundle models, chains of fiber bundle models and the stochastic finite element method in the context of quasibrittle failure.  相似文献   
98.
A significant change in the UV-vis absorption of TiO2 nanorods (NRs) was induced by changing electrondonating stabilizer from oleic acid (OA) to acrylic acid (AcA). When TiO2 NRs with an average size of 2.5 nm in diameter and 30 nm in length were dispersed in an aqueous AcA solution, a red shift in the optical absorption (0.73 eV at the band edge and 0.55 eV at the onset) was observed. The red shift was attributed to an increase in the electron density inside the TiO2 NRs. The applicability of the AcA-exchanged TiO2 NRs for the photocatalyst as well as a UV sensor was evaluated. The AcA-exchanged TiO2 NRs showed significant photocatalytic activity on the degradation of toluene in the visible light region. Moreover, thin film of the AcA-exchanged TiO2 NRs on a quartz plate was tested as a UV sensor and it exhibited a good response to a wide range of the UV light.  相似文献   
99.
A review of the literature revealed that recently published phase diagrams of the Fe-Nb system show considerable discrepancies regarding phase equilibria with the melt and the homogeneity ranges of the intermetallic phases, specifically of the Laves phase Fe2Nb. Therefore the system has been reinvestigated by metallography, electron probe microanalysis (EPMA), and differential thermal analysis (DTA). Temperatures of invariant reactions were determined and the homogeneity ranges of the two intermetallic phases, Fe2Nb Laves phase and Fe7Nb6 μ phase, which both exist within a wide composition range, were established.  相似文献   
100.
We study for the first time the backward problem for nonlocal nonlinear boundary value problem of Kirchhoff’s model of parabolic type. First, we show that the problem is severely ill-posed in the sense of Hadamard. We propose two methods: the Fourier truncation method for stabilizing the problem with homogeneous source and the quasi-reversibility method for regularizing the problem with nonlinear source. Under some priori assumptions on the exact solution, we establish some stability estimates in the H01 norm.  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