全文获取类型
收费全文 | 167861篇 |
免费 | 7480篇 |
国内免费 | 2435篇 |
专业分类
电工技术 | 3765篇 |
技术理论 | 5篇 |
综合类 | 5204篇 |
化学工业 | 27623篇 |
金属工艺 | 8458篇 |
机械仪表 | 6894篇 |
建筑科学 | 7052篇 |
矿业工程 | 2365篇 |
能源动力 | 3583篇 |
轻工业 | 13963篇 |
水利工程 | 2452篇 |
石油天然气 | 4262篇 |
武器工业 | 397篇 |
无线电 | 16197篇 |
一般工业技术 | 27706篇 |
冶金工业 | 11145篇 |
原子能技术 | 1029篇 |
自动化技术 | 35676篇 |
出版年
2024年 | 322篇 |
2023年 | 1230篇 |
2022年 | 2075篇 |
2021年 | 3281篇 |
2020年 | 2549篇 |
2019年 | 2351篇 |
2018年 | 16930篇 |
2017年 | 16057篇 |
2016年 | 12670篇 |
2015年 | 3833篇 |
2014年 | 4378篇 |
2013年 | 6219篇 |
2012年 | 8553篇 |
2011年 | 14737篇 |
2010年 | 12862篇 |
2009年 | 9751篇 |
2008年 | 10862篇 |
2007年 | 11679篇 |
2006年 | 4001篇 |
2005年 | 4433篇 |
2004年 | 3385篇 |
2003年 | 3194篇 |
2002年 | 2412篇 |
2001年 | 1578篇 |
2000年 | 1766篇 |
1999年 | 1952篇 |
1998年 | 3213篇 |
1997年 | 2294篇 |
1996年 | 1853篇 |
1995年 | 1355篇 |
1994年 | 1065篇 |
1993年 | 831篇 |
1992年 | 509篇 |
1991年 | 422篇 |
1990年 | 327篇 |
1989年 | 279篇 |
1988年 | 291篇 |
1987年 | 197篇 |
1986年 | 174篇 |
1985年 | 161篇 |
1984年 | 142篇 |
1983年 | 96篇 |
1982年 | 88篇 |
1981年 | 102篇 |
1980年 | 87篇 |
1977年 | 122篇 |
1976年 | 227篇 |
1966年 | 50篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
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
102.
103.
Jon T. Carter Paul E. Krajewski Ravi Verma 《JOM Journal of the Minerals, Metals and Materials Society》2008,60(11):77-81
The hot blow forming of magnesium sheet offers significant opportunity for forming complex, lightweight parts for automotive
applications. This paper characterizes the elevated-temperature formability of AZ31 magnesium sheet materials and the effect
of processing conditions on the performance of these materials. In addition, magnesium sheet application development at General
Motors Corporation is reviewed. 相似文献
104.
Toshihiko Hoshide Junpei Fujita 《Journal of Materials Engineering and Performance》2008,17(5):627-632
Strength of ground ceramics may be affected by residual stress as well as surface flaws induced by grinding. Strength prediction
for ground ceramics is convenient for mechanical design of ceramic components. In this article, a numerical procedure based
on fracture mechanics was proposed to estimate strength distribution of ground ceramics by considering grinding-induced residual
stress. Bending strength and residual stress of ground ceramics were measured for three grinding-conditions. By comparison
of simulated results with experimental ones, it was revealed that strength characteristics in experiments were well simulated
by using the proposed procedure. 相似文献
105.
A novel series of temperature‐sensitive poly[(N‐isopropylacrylamide)‐co‐(ethyl methacrylate)] (p(NIPAM‐co‐EMA)) microgels was prepared by the surfactant‐free radical polymerization of N‐isopropylacrylamide (NIPAM) with ethyl methacrylate (EMA). The shape, size dispersity and volume‐phase transition behavior of the microgels were investigated by transmission electron microscopy (TEM), ultraviolet–visible (UV–Vis) spectroscopy, dynamic light scattering (DLS) and differential scanning calorimetry (DSC). The transmission electron micrographs and DLS results showed that microgels with narrow distributions were prepared. It was shown from UV–Vis, DLS and DSC measurements that the volume‐phase transition temperature (VPTT) of the p(NIPAM‐co‐EMA) microgels decreased with increasing incorporation of EMA, but the temperature‐sensitivity was impaired when more EMA was incorporated, causing the volume‐phase transition of the microgels to become more continuous. It is noteworthy that incorporation of moderate amounts of EMA could not only lower the VPTT but also enhance the temperature‐sensitivity of the microgels. The reason for this phenomenon could be attributed to changes in the complicated interactions between the various molecules. Copyright © 2004 Society of Chemical Industry 相似文献
106.
Analysis of multiple FSS screens of unequal periodicity using an efficient cascading technique 总被引:1,自引:0,他引:1
In this paper, we present an efficient cascading procedure for analyzing frequency selective surface (FSS) systems consisting of multiple FSS screens of unequal periodicity embedded in multiple dielectric layers. In this procedure, we first find a global period for the FSS system by studying the composite in its entirety. Next, we compute the scattering matrix [S] of each of the FSS subsystems for the global Floquet harmonics by applying a relationship we establish that maps the [S] matrix of the subsystem for the individual Floquet harmonics to that for the global harmonics. This mapping-cum-filling process substantially reduces the effort needed to compute the [S] matrix of a subsystem. Finally, we compute the [S] of the entire system by applying a modified cascading formulation, in which one matrix inversion step is eliminated, resulting in a reduction in the total computing resource requirement as well as time. Two numerical examples are given to illustrate the efficiency and effectiveness of the technique. 相似文献
107.
本文评价了塑料闪烁片用作软β核素探测器时的计数效率、β谱、本底谱和康普顿电子谱的特征。文中强调:采用胶合光导剂构成的系统是一种新型探测器(软β核素内部样品塑料闪烁探测器)。本文提出内部样品固体探测器、胶合光导剂和胶合闪烁光导剂的新概念。 相似文献
108.
In this article, a general synthesis method is proposed for the design of discontinuous feedback strategies leading to asymptotically stabilizing sliding regimes. The method is applicable to the class of nonlinear dynamical systems possessing constant equilibrium points. A family of nonlinear stabilizing sliding manifolds, parametrized by generic desired equilibrium point, is specified on the basis of the extended linearization approach. Some examples including simulations are presented for illustrative purposes.
Editor: S. Zak 相似文献
109.
Zirconium(IV) tungstoiodophosphate has been synthesized under a variety of conditions. The most chemically and thermally stable
sample is prepared by adding a mixture of aqueous solutions of 0·5 mol L−1 sodium tungstate, potassium iodate and 1 mol L−1 orthophosphoric acid to aqueous solution of 0·1 mol L−1 zirconium(IV) oxychloride. Its ion exchange capacity for Na+ and K+ was found to be 2·20 and 2·35 meq g−1 dry exchanger, respectively. The material has been characterized on the basis of chemical composition, pH titration, Fourier
transform infrared spectroscopy (FTIR) and thermogravimetric analysis. The effect on the exchange capacity of drying the exchanger
at different temperatures has been studied. The analytical importance of the material has been established by quantitative
separation of Pb2+ from other metal ions. 相似文献
110.
Jonathan P. Belnoue Giang D. Nguyen Alexander M. Korsunsky 《International Journal of Fracture》2007,144(1):53-60
This paper presents a new 1-D non-local damage-plasticity deformation model for ductile materials. It uses the thermodynamic
framework described in Houlsby and Puzrin (2000) and holds, nevertheless, some similarities with Lemaitre’s (1971) approach.
A 1D finite element (FE) model of a bar fixed at one end and loaded in tension at the other end is introduced. This simple
model demonstrates how the approach can be implemented within the finite element framework, and that it is capable of capturing
both the pre-peak hardening and post-peak softening (generally responsible for models instability) due to damage-induced stiffness
and strength reduction characteristic of ductile materials. It is also shown that the approach has further advantages of achieving
some degree of mesh independence, and of being able to capture deformation size effects. Finally, it is illustrated how the
model permits the calculation of essential work of rupture (EWR), i.e. the specific energy per unit cross-sectional area that
is needed to cause tensile failure of a specimen. 相似文献