全文获取类型
收费全文 | 35224篇 |
免费 | 4412篇 |
国内免费 | 3336篇 |
专业分类
电工技术 | 2412篇 |
技术理论 | 2篇 |
综合类 | 4786篇 |
化学工业 | 3288篇 |
金属工艺 | 2333篇 |
机械仪表 | 2557篇 |
建筑科学 | 1623篇 |
矿业工程 | 749篇 |
能源动力 | 575篇 |
轻工业 | 1688篇 |
水利工程 | 577篇 |
石油天然气 | 821篇 |
武器工业 | 398篇 |
无线电 | 3625篇 |
一般工业技术 | 5208篇 |
冶金工业 | 1291篇 |
原子能技术 | 224篇 |
自动化技术 | 10815篇 |
出版年
2024年 | 135篇 |
2023年 | 504篇 |
2022年 | 1035篇 |
2021年 | 1218篇 |
2020年 | 1139篇 |
2019年 | 1139篇 |
2018年 | 1016篇 |
2017年 | 1303篇 |
2016年 | 1359篇 |
2015年 | 1599篇 |
2014年 | 2152篇 |
2013年 | 2508篇 |
2012年 | 2461篇 |
2011年 | 2620篇 |
2010年 | 2095篇 |
2009年 | 2310篇 |
2008年 | 2148篇 |
2007年 | 2463篇 |
2006年 | 2061篇 |
2005年 | 1872篇 |
2004年 | 1571篇 |
2003年 | 1278篇 |
2002年 | 1071篇 |
2001年 | 960篇 |
2000年 | 814篇 |
1999年 | 696篇 |
1998年 | 552篇 |
1997年 | 463篇 |
1996年 | 412篇 |
1995年 | 392篇 |
1994年 | 329篇 |
1993年 | 264篇 |
1992年 | 209篇 |
1991年 | 167篇 |
1990年 | 143篇 |
1989年 | 120篇 |
1988年 | 78篇 |
1987年 | 55篇 |
1986年 | 34篇 |
1985年 | 31篇 |
1984年 | 37篇 |
1983年 | 26篇 |
1982年 | 16篇 |
1981年 | 19篇 |
1980年 | 7篇 |
1979年 | 9篇 |
1978年 | 7篇 |
1977年 | 8篇 |
1976年 | 7篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
171.
In this paper, genetic algorithm is used to help improve the tolerance of feedforward neural networks against an open fault. The proposed method does not explicitly add any redundancy to the network, nor does it modify the training algorithm. Experiments show that it may profit the fault tolerance as well as the generalisation ability of neural networks. 相似文献
172.
Scaffold‐guided tissue engineering based on synthetic and natural occurring polymers has gained many interests in recent year. In this study, the development of a chitosan‐heparin artificial extracellular matrix (AECM) is reported. Three‐dimensional, macroporous composite AECMs composed of heparin (Hep) and chitosan (Chito) were prepared by an interpolyelectrolyte complex/lyophilization method. The Chito‐Hep composite AECMs were, respectively, crosslinked with glutaraldehyde, as well as cocrosslinked with N,N‐(3‐dimethylaminopropyl)‐N′‐ethyl carbodiimide (EDC/NHS) and N‐hydroxysuccinimide (NHS). The crosslinking reactions were examined by FT‐IR analysis. In physiological buffer solution (PBS), the EDC/NHS‐crosslinked Chito‐Hep composite AECM showed a relative lower water retention ratio than its glutaraldehyde‐crosslinked counterparts. The EDC/NHS‐crosslinked Chito‐Hep composite AECMs showed excellent biocompatibility, according to the results of the in vitro cytotoxic test. This result suggested that the EDC/NHS‐crosslinked Chito‐Hep composite AECMs might be a potential biomaterial for scaffold‐guided tissue engineering applications. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
173.
174.
175.
Discretization of boundary integral equations leads, in general, to fully populated non-symmetric linear systems of equations. An inherent drawback of boundary element method (BEM) is that, the non-symmetric dense linear systems must be solved. For large-scale problems, the direct methods require expensive computational cost and therefore the iterative methods are perhaps more preferable. This paper studies the comparative performances of preconditioned Krylov subspace solvers as bi-conjugate gradient (Bi-CG), generalized minimal residual (GMRES), conjugate gradient squared (CGS), quasi-minimal residual (QMR) and bi-conjugate gradient stabilized (Bi-CGStab) for the solution of dense non-symmetric systems. Several general preconditioners are also considered and assessed. The results of numerical experiments suggest that the preconditioned Krylov subspace methods are effective approaches solving the large-scale dense non-symmetric linear systems arising from BEM. 相似文献
176.
Gerda C. Glaeser 《Thin solid films》2007,515(15):5964-5967
Fluorescent photon down conversion for the improvement of the blue response of ZnO/CdS/Cu(In,Ga)Se2 heterojunction solar cells and modules is investigated. Fluorescent dyes of the series Lumogen® F are analyzed by optical transmission and reflection as well as by photoluminescence measurements. A spectral transfer matrix formalism is introduced that allows to predict the suitability of a luminescent dye as a down-converter for a given solar cell from its absorption/emission properties. We find that Lumogen® F Violet 570 and Lumogen® F Yellow 083 as well as a combination of both yields improvements for Cu(In,Ga)Se2 solar modules. Particularly, we find that the short circuit current density of a Cu(In,Ga)Se2 mini-module is improved by 1.5 mA cm− 2 when applying a varnish with a combination of Lumogen® F Violet and Yellow. About 0.5 mA cm− 2 of this improvement is due to a reduced overall reflectance and an improvement of 1 mA cm− 2 results from the frequency conversion by the dyes. 相似文献
177.
People have knowledge about relationships (i.e., relational schemas) that is based on their experiences. Because most people have experience with complementary behavior (interaction partners behaving similarly in terms of affiliation but oppositely in terms of control), they expect complementary behavior in their relationships. Like other beliefs about relationships, expectations of complementarity affect self-construal. The authors provide evidence for complementary self-construal; people assimilate to relevant relationship partners on the affiliation dimension and contrast on the control dimension. Consistent with the proposed role of relationship knowledge in these effects, complementary self-construal was moderated by the familiarity of the target, whether people focused on their relationship with or the appearance of the target, and whether the context was relevant for the interpersonal dimension. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
178.
Generalized null space uncorrelated Fisher discriminant analysis for linear dimensionality reduction
We propose a generalized null space uncorrelated Fisher discriminant analysis (GNUFDA) technique integrating the uncorrelated discriminant analysis and weighted pairwise Fisher criterion. The GNUFDA can effectively deal with the small sample-size problem and perform satisfactorily when the dimensionality of the null space decreases with increase in the number of training samples per class and/or classes, C. The proposed GNUFDA can extract at most C-1 optimal uncorrelated discriminative vectors without being influenced by the null-space dimensionality. 相似文献
179.
针对3^n阶矩阵的乘法运行,给出了一种分块算法,其乘法运行量比常规的矩阵乘法计算方法和补零的基-2算法都有所减少。 相似文献
180.
本文从C/C复合材料的基体入手,研究了基体沥青、焦炭中添加氧化物的工艺条件及其在复合材料中的作用.结果表明,添加氧化物对基体改性,不仅能提高C/C复合材料的高温抗氧化性,也能对其它性能带来很大影响.只要控制适当的工艺条件,就可以得到高性能的C/C复合材料. 相似文献