全文获取类型
收费全文 | 7260篇 |
免费 | 1383篇 |
国内免费 | 449篇 |
专业分类
电工技术 | 759篇 |
综合类 | 1060篇 |
化学工业 | 363篇 |
金属工艺 | 257篇 |
机械仪表 | 831篇 |
建筑科学 | 626篇 |
矿业工程 | 293篇 |
能源动力 | 158篇 |
轻工业 | 201篇 |
水利工程 | 318篇 |
石油天然气 | 287篇 |
武器工业 | 113篇 |
无线电 | 978篇 |
一般工业技术 | 776篇 |
冶金工业 | 88篇 |
原子能技术 | 106篇 |
自动化技术 | 1878篇 |
出版年
2025年 | 14篇 |
2024年 | 118篇 |
2023年 | 118篇 |
2022年 | 168篇 |
2021年 | 198篇 |
2020年 | 252篇 |
2019年 | 194篇 |
2018年 | 200篇 |
2017年 | 301篇 |
2016年 | 336篇 |
2015年 | 366篇 |
2014年 | 495篇 |
2013年 | 555篇 |
2012年 | 566篇 |
2011年 | 587篇 |
2010年 | 470篇 |
2009年 | 452篇 |
2008年 | 427篇 |
2007年 | 521篇 |
2006年 | 449篇 |
2005年 | 383篇 |
2004年 | 328篇 |
2003年 | 244篇 |
2002年 | 169篇 |
2001年 | 147篇 |
2000年 | 124篇 |
1999年 | 113篇 |
1998年 | 113篇 |
1997年 | 106篇 |
1996年 | 99篇 |
1995年 | 103篇 |
1994年 | 85篇 |
1993年 | 46篇 |
1992年 | 47篇 |
1991年 | 39篇 |
1990年 | 39篇 |
1989年 | 30篇 |
1988年 | 24篇 |
1987年 | 10篇 |
1986年 | 16篇 |
1985年 | 9篇 |
1984年 | 9篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1959年 | 1篇 |
排序方式: 共有9092条查询结果,搜索用时 15 毫秒
1.
Immobilization was carried out of the lactate dehydrogenase (LDH) from rabbit muscle (EC 1.1.1.27), cross-linked through the bifunctional reactive glutar-aldehyde on to nylon tubing (1 m long, 53cm2 internal surface area). Immobilized LDH inactivation kinetics are of first order (t1/2 = 3·6 years, k = 5·4,e?4 day?1 to 5°C). The smaller effect of pH on activity than in the case of LDH in solution can be explained on the basis of limitation to proton diffusion towards the support. A limiting effect to free external diffusion of the substrate towards and products from the support was also observed, an effect which seems to determine the effective kinetic behaviour of immobilized LDH. The apparent optimum temperature is centred around 40°C, observing a clear inactivation (thermal denaturation) above this temperature. In the temperature range studied (10–40°C), the co-existence was seen of a kinetic control accompanied by another control, involving diffusional transport of substrates and products, on the global activity of the immobilized enzyme. This makes the Arrhenius profiles curvilinear. Both graphic and statistical non-linear regression analysis of the kinetic data—rate, v, versus substrate concentration [S]—carried out under conditions in which the diffusional limitations can be considered negligible (high recirculation flow rate), permitted investigation of the intrinsic kinetic behaviour of immobilized LDH. In this sense, it can be deduced that the rate equation to which these data seem to be fitted is of the polynomial quotient type in [S] of minimum degree 2:2. Although the diffusional limitations have a marked effect on the type of global kinetics shown by immobilized LDH, temperature was not found to affect its v[S] behaviour. The experimental evidence obtained thus indicates that the rate equation in the 10-40°C temperature range continues to be a rational equation of at least degree 2:2 in [S]. 相似文献
2.
OPGW应用问题的探讨 总被引:2,自引:1,他引:1
根据多年的光纤复合架空地线(0PGW)应用经验与实践,从0PGW结构及组成、光纤余长、线路配合、金具配套、0PGW安装等方面,对0PGW应用中的若干问题进行详细的探讨。 相似文献
3.
4.
Geometrically non-linear behavior of structural systems with random material property: An asymptotic spectral stochastic approach 总被引:1,自引:0,他引:1
M. Tootkaboni L. Graham-Brady B.W. Schafer 《Computer Methods in Applied Mechanics and Engineering》2009,198(37-40):3173-3185
An asymptotic spectral stochastic approach is presented for computing the statistics of the equilibrium path in the post-bifurcation regime for structural systems with random material properties. The approach combines numerical implementation of Koiter’s asymptotic theory with a stochastic Galerkin scheme and collocation in stochastic space to quantify uncertainties in the parametric representation of the load–displacement relationship, specifically in the form of uncertain post-buckling slope, post-buckling curvature, and a family of stochastic displacement fields. Using the proposed method, post-buckling response statistics for two plane frames are obtained and shown to be in close agreement with those obtained from Monte Carlo simulation, provided a fine enough spectral representation is used to model the variability in the random dimension. 相似文献
5.
学生成绩评定方法研究 总被引:2,自引:0,他引:2
分别用x2拟合检验法、直方图和Q-Q分布图从直观和理论两方面出发验证学生成绩是否呈正态分布,通过图象与应用概率统计知识有机结合,运用数学软件对数据进行处理,达到验证研究的目的。 相似文献
6.
7.
The algorithm is divided into two steps. The first step pre-locates the blank by aligning its centre of gravity and approximate normal vector with those of destination surfaces, with largest overlap of projections of two objects on a plane perpendicular to the normal vector. The second step is optimizing an objective function by means of gradient-simulated annealing algorithm to get the best matching of a set of distributed points on the blank and destination surfaces. An example for machining… 相似文献
8.
利用Matcom将MATLAB和Visual C++结合起来,充分发挥各自的优势,是编制高效程序的有效途径。介绍了如何在VC++环境下利用Matcom进行数据拟合,并得到相应拟合曲线的方法。 相似文献
9.
10.
利用运行点和边界值条件简化模型的方法 总被引:1,自引:0,他引:1
一个高阶模型G(S)=K_0/(TS 1)~n可以在运行状态及边界条件下通过拟合,简化成确定性模型C_τ(S)=(?)或不确定性模型(?)文中研究这种模型简化原理和方法.仿真试 验表明:这种方法可以广泛应用于仪表及其系统分析与设计. 相似文献