全文获取类型
收费全文 | 2254篇 |
免费 | 73篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 30篇 |
综合类 | 6篇 |
化学工业 | 508篇 |
金属工艺 | 56篇 |
机械仪表 | 25篇 |
建筑科学 | 118篇 |
矿业工程 | 10篇 |
能源动力 | 98篇 |
轻工业 | 136篇 |
水利工程 | 6篇 |
石油天然气 | 15篇 |
无线电 | 161篇 |
一般工业技术 | 327篇 |
冶金工业 | 480篇 |
原子能技术 | 26篇 |
自动化技术 | 337篇 |
出版年
2022年 | 30篇 |
2021年 | 38篇 |
2020年 | 25篇 |
2019年 | 25篇 |
2018年 | 33篇 |
2017年 | 36篇 |
2016年 | 32篇 |
2015年 | 34篇 |
2014年 | 48篇 |
2013年 | 220篇 |
2012年 | 72篇 |
2011年 | 84篇 |
2010年 | 91篇 |
2009年 | 83篇 |
2008年 | 94篇 |
2007年 | 76篇 |
2006年 | 56篇 |
2005年 | 63篇 |
2004年 | 50篇 |
2003年 | 47篇 |
2002年 | 42篇 |
2001年 | 36篇 |
2000年 | 20篇 |
1999年 | 35篇 |
1998年 | 74篇 |
1997年 | 48篇 |
1996年 | 49篇 |
1995年 | 50篇 |
1994年 | 38篇 |
1993年 | 44篇 |
1992年 | 28篇 |
1991年 | 28篇 |
1990年 | 36篇 |
1989年 | 18篇 |
1988年 | 22篇 |
1987年 | 27篇 |
1986年 | 34篇 |
1985年 | 21篇 |
1984年 | 31篇 |
1983年 | 26篇 |
1982年 | 29篇 |
1981年 | 36篇 |
1980年 | 21篇 |
1979年 | 22篇 |
1978年 | 19篇 |
1977年 | 26篇 |
1976年 | 19篇 |
1975年 | 31篇 |
1974年 | 19篇 |
1973年 | 17篇 |
排序方式: 共有2339条查询结果,搜索用时 15 毫秒
71.
72.
Khaled Safi Samer Mohammed Inke Marie Albertsen Eric Delechelle Yacine Amirat Mohamad Khalil Jean-Michel Gracies Emilie Hutin 《Signal, Image and Video Processing》2017,11(6):1081-1088
The present study proposes a new approach for the assessment of the human balance control. This approach is based on the decomposition of the center of pressure displacement using empirical mode decomposition (EMD) that provides an effective time-frequency analysis of non-stationary signals. Twenty-eight healthy subjects performed quiet standing in four conditions—feet apart/together with respect to eyes open/closed—while recording the stabilometric signals in the anteroposterior (AP) and mediolateral (ML) directions. The EMD method decomposes each stabilometric signal into several subsignals called intrinsic mode functions (IMFs). Stabilogram-diffusion analysis technique is applied to generate the diffusion curve of each IMF signal. Each diffusion curve is modeled as a second-order system and provides representative features, such as the gain parameter. Analysis of the gain parameter shows the major effect of visual input and feet conditions on the strategy to control/stabilize the balance. Significant differences were found between young and elderly, and between women and men. In addition, the impact of feet position seems to be higher in ML direction than in AP direction. 相似文献
73.
An X‐FEM‐based numerical–asymptotic expansion for simulating a Stokes flow near a sharp corner 下载免费PDF全文
Louis C. Foucard Franck J. Vernerey 《International journal for numerical methods in engineering》2015,102(2):79-98
A numerical technique that is based on the integration of the asymptotic solution in the numerical framework for computing the local singular behavior of Stokes flow near a sharp corner is presented. Moffat's asymptotic solution is used, and special enriched shape functions are developed and integrated in the extended finite element method (X‐FEM) framework to solve the Navier–Stokes equations. The no‐slip boundary condition on the walls of the corner is enforced via the use of Lagrange multipliers. Flows around corners with different angles are simulated, and the results are compared with both those of the known analytic solution and the X‐FEM with no special enrichment near the corner. The results of the present technique are shown to greatly reduce the error made in computing the pressure and velocity fields near a corner tip without the need for mesh refinement near the corner. The method is then applied to the estimation of the permeability of a network of fibers, where it is shown that the local small‐scale pressure singularities have a large impact on the large‐scale network permeability. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
74.
Louis de Redon 《The International journal of environmental studies》2013,70(5):722-744
This speculative opinion is based on an apparent dream caused by Donald Trump’s decision to withdraw the U.S. from the Paris Agreement. The account includes a comparison between arguments against the abolition of slavery and those against ending a fossil-fuel based economy in favor of sustainability through a green approach. Recent social disturbance in France shows that a carbon tax has not been persuasively advocated. But it should be clear that unchanged laissez-faire economics will produce disaster in light of the facts about global heating and climate change. This account is based on historical and contemporary quotations from American political figures from both the XIX and XXI centuries. The parallels raise fundamental issues of human rights. 相似文献
75.
76.
77.
In modern day pattern recognition, neural nets are used extensively. General use of a feedforward neural net consists of a training phase followed by a classification phase. Classification of an unknown test vector is very fast and only consists of the propagation of the test vector through the neural net. Training involves an optimization procedure and is very time-consuming since a feasible local minimum is sought in high-dimensional weight space. In this paper we present an analysis of a parallel implementation of the backpropagation training algorithm using conjugate gradient optimization for a three-layered, feedforward neural network, on the KSR1 parallel shared-memory machine. We implement two parallel neural net training versions on the KSR1, one using native code, the other using P4, a library of macros and functions. A speedup model is presented which we use to clarify our experimental results. We identify the general requirements which render the parallel implementation useful, compared to the sequential execution of the same neural net training procedure. We determine the usefulness of a library of functions (such as P4) developed to ease the task of the programmer. Using experimental results we further identify the limits in processor utilization for our parallel training algorithm. 相似文献
78.
Brittleness is an important parameter controlling the mechanical behavior and failure characteristics of rocks under loading and unloading conditions,such as fracability,cutability,drillability and rockburst proneness.As such,it is of high practical value to correctly evaluate rock brittleness.However,the definition and measurement method of rock brittleness have been very diverse and not yet been standardized.In this paper,the definitions of rock brittleness are firstly reviewed,and several representative definitions of rock brittleness are identified and briefly discussed.The development and role of rock brittleness in different fields of rock engineering are also studied.Eighty brittleness indices publicly available in rock mechanics literature are compiled,and the measurement method,applicability and limitations of some indices are discussed.The results show that(1)the large number of brittleness indices and brittleness definitions is attributed to the different foci on the rock behavior when it breaks;(2)indices developed in one field usually are not directly applicable to other fields;and(3)the term“brittleness”is sometimes misused,and many empirically-obtained brittleness indices,which lack theoretical basis,fail to truly reflect rock brittleness.On the basis of this review,three measurement methods are identified,i.e.(1)elastic deformation before fracture,(2)shape of post-peak stressestrain curves,and(3)methods based on fracture mechanics theory,which have the potential to be further refined and unified to become the standard measurement methods of rock brittleness.It is highly beneficial for the rock mechanics community to develop a robust definition of rock brittleness.This study will undoubtedly provide a comprehensive timely reference for selecting an appropriate brittleness index for their applications,and will also pave the way for the development of a standard definition and measurement method of rock brittleness in the long term. 相似文献
79.
Poya Kavianpour Madeleine C. M. Gemmell Dr. Jan U. Kahlert Prof. Louis M. Rendina 《Chembiochem : a European journal of chemical biology》2020,21(19):2786-2791
Histone deacetylase enzymes (HDACs) are responsible for the global silencing of tumour-suppressor genes. Treatment with a histone deacetylase inhibitor (HDACi) can reverse this process and restore normal cell function. Herein, we report a small series of boron-based (boronic acid, boronate ester and closo-1,2-carborane) HDAC2 inhibitors with IC50 values in the nanomolar range. The boronate ester 4 b was the most potent compound assessed in this study (IC50=40.6±1.5 nM), followed closely by the 1,2-closo-carborane (IC50=42.9±1.5 nM). Compound 4 b exceeds the potency of the related gold-standard HDAC pan-inhibitor vorinostat ( 1 ) toward this particular HDAC isoform. 相似文献
80.
Richard M. Gunner Rory P. Wilson Mark D. Holton Phil Hopkins Stephen H. Bell Nikki J. Marks Nigel C. Bennett Sam Ferreira Danny Govender Pauli Viljoen Angela Bruns O. Louis van Schalkwyk Mads F. Bertelsen Carlos M. Duarte Martin C. van Rooyen Craig J. Tambling Aoife Gppert Delmar Diesel D. Michael Scantlebury 《Journal of the Royal Society Interface》2022,19(186)
The combined use of global positioning system (GPS) technology and motion sensors within the discipline of movement ecology has increased over recent years. This is particularly the case for instrumented wildlife, with many studies now opting to record parameters at high (infra-second) sampling frequencies. However, the detail with which GPS loggers can elucidate fine-scale movement depends on the precision and accuracy of fixes, with accuracy being affected by signal reception. We hypothesized that animal behaviour was the main factor affecting fix inaccuracy, with inherent GPS positional noise (jitter) being most apparent during GPS fixes for non-moving locations, thereby producing disproportionate error during rest periods. A movement-verified filtering (MVF) protocol was constructed to compare GPS-derived speed data with dynamic body acceleration, to provide a computationally quick method for identifying genuine travelling movement. This method was tested on 11 free-ranging lions (Panthera leo) fitted with collar-mounted GPS units and tri-axial motion sensors recording at 1 and 40 Hz, respectively. The findings support the hypothesis and show that distance moved estimates were, on average, overestimated by greater than 80% prior to GPS screening. We present the conceptual and mathematical protocols for screening fix inaccuracy within high-resolution GPS datasets and demonstrate the importance that MVF has for avoiding inaccurate and biased estimates of movement. 相似文献