全文获取类型
收费全文 | 15204篇 |
免费 | 1228篇 |
国内免费 | 217篇 |
专业分类
电工技术 | 462篇 |
技术理论 | 1篇 |
综合类 | 497篇 |
化学工业 | 3473篇 |
金属工艺 | 413篇 |
机械仪表 | 548篇 |
建筑科学 | 776篇 |
矿业工程 | 230篇 |
能源动力 | 428篇 |
轻工业 | 2644篇 |
水利工程 | 206篇 |
石油天然气 | 495篇 |
武器工业 | 52篇 |
无线电 | 1048篇 |
一般工业技术 | 2393篇 |
冶金工业 | 791篇 |
原子能技术 | 72篇 |
自动化技术 | 2120篇 |
出版年
2024年 | 52篇 |
2023年 | 205篇 |
2022年 | 464篇 |
2021年 | 667篇 |
2020年 | 428篇 |
2019年 | 441篇 |
2018年 | 559篇 |
2017年 | 625篇 |
2016年 | 585篇 |
2015年 | 545篇 |
2014年 | 736篇 |
2013年 | 1214篇 |
2012年 | 992篇 |
2011年 | 1071篇 |
2010年 | 870篇 |
2009年 | 810篇 |
2008年 | 843篇 |
2007年 | 757篇 |
2006年 | 736篇 |
2005年 | 505篇 |
2004年 | 398篇 |
2003年 | 385篇 |
2002年 | 339篇 |
2001年 | 333篇 |
2000年 | 274篇 |
1999年 | 259篇 |
1998年 | 324篇 |
1997年 | 239篇 |
1996年 | 179篇 |
1995年 | 163篇 |
1994年 | 127篇 |
1993年 | 85篇 |
1992年 | 59篇 |
1991年 | 43篇 |
1990年 | 36篇 |
1989年 | 41篇 |
1988年 | 39篇 |
1987年 | 19篇 |
1986年 | 20篇 |
1985年 | 26篇 |
1984年 | 30篇 |
1983年 | 29篇 |
1982年 | 22篇 |
1981年 | 8篇 |
1980年 | 11篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1977年 | 10篇 |
1976年 | 12篇 |
1967年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
This paper introduces and evaluates a new class of knowledge model, the recursive Bayesian multinet (RBMN), which encodes the joint probability distribution of a given database. RBMNs extend Bayesian networks (BNs) as well as partitional clustering systems. Briefly, a RBMN is a decision tree with component BNs at the leaves. A RBMN is learnt using a greedy, heuristic approach akin to that used by many supervised decision tree learners, but where BNs are learnt at leaves using constructive induction. A key idea is to treat expected data as real data. This allows us to complete the database and to take advantage of a closed form for the marginal likelihood of the expected complete data that factorizes into separate marginal likelihoods for each family (a node and its parents). Our approach is evaluated on synthetic and real-world databases. 相似文献
52.
V. Salgueiriño‐Maceira M. A. Correa‐Duarte 《Advanced materials (Deerfield Beach, Fla.)》2007,19(23):4131-4144
This Review article ponders core/shell structured nanoparticles that can be prepared with features that combine properties of different materials, including ligands that enhance their biocompatibility. These nanocomposites are not classified in terms of synthesis, but rather by how these features are distributed in the final morphology, attending to connected or isolated materials that end up in interacting or not‐interacting functionalities. In particular, we have focused on magnetic core/shell‐structured particles with a directly connected, coupled, or isolated second functionality. The current progress on methods in colloidal solution that have allowed the great development of these multifunctional magnetic and active spheres on biological and biomedical fields is reported. 相似文献
53.
54.
An evaluation of the Spanish CSIC performance in Biotechnology, as compared with those of the French CNRS and the Italian
CNR, has been carried out to determine the balance between the generation of scientific knowledge and the transfer of technology.
This study shows a high scientific productivity mostly in journals with moderate impact factor, a low generation of patents
and an insufficient transfer of knowledge to the Spanish companies. Other indicators confirm the existence of competitive
human resources in biotechnological research producing scientific knowledge of interest for the development of patents and
that cooperates successfully at European level. 相似文献
55.
P. Cañizares J. García-Gómez C. Sáez M.A. Rodrigo 《Journal of Applied Electrochemistry》2003,33(10):917-927
The electrochemical oxidation of 4-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol aqueous wastes using boron-doped diamond electrodes was studied. This treatment led to complete mineralization of the wastes regardless of the operating conditions. A simple mechanistic model is consistent with the voltammetric and electrolysis results. According to this model, the electrochemical treatment of chlorophenol aqueous wastes involves the anodic and cathodic release of chlorine followed by the formation of non-chlorinated aromatic intermediates. Subsequent cleavage of the aromatic ring gives rise to non-chlorinated carboxylic acids. Chlorine atoms arising from the hydrodehalogenation of the chlorophenols are converted into more oxidized molecules at the anode. These molecules react with unsaturated C4 carboxylic acid to finally yield trichloroacetic acid through a haloform reaction. The non-chlorinated organic acids are ultimately oxidized to carbon dioxide and the trichloroacetic acid into carbon dioxide and volatile organo-chlorinated molecules. Both direct and mediated electrochemical oxidation processes are involved in the electrochemical treatment of chlorophenols. 相似文献
56.
加固改造中的结构承重体系转换 总被引:2,自引:0,他引:2
从加固改造工程的实践出发 ,探讨了混合结构向框架结构体系转换的方法和构造措施 ,为实际工程提供了新的技术思路 相似文献
57.
C/O测井中采用同步测量技术来分析非弹性γ与俘获γ,但在一些MSI C/O测井中发现非弹性γ的一小部分或一大部分超前于非弹性门而进入俘获门,我们把这一问题叫做“错位”。“错位”使得C/O的CI值不正常,测井曲线不合格。这样的仪器不能用来测井。吉林油田测井公司碳氧比维修班成功地解决了C/O仪器“错位”等技术难题,在该油田所使用的CZF90-94-09发生器已测井88口,累计打靶时间230h,并且至今 相似文献
58.
59.
Fibroblast cultures were established from the skin of normal and psoriatic subjects. The response to 1 alpha,25-dihydroxyvitamin D3 [1,25-(OH)2D3] of each kind of cells was assessed by measuring tritiated thymidine incorporation into DNA as an index of cell proliferation. We found that both types of cells responded with a similar dose- and time-dependent inhibition of thymidine incorporation. We also studied the response of the mRNA encoding the proto-oncogene c-myc, since its level is associated to the proliferative state in many cell types. Psoriatic fibroblasts contained higher basal amounts of c-myc RNA than control fibroblasts. Addition of 1,25-(OH)2D3 to the culture medium induced a time-dependent increase of c-myc RNA in psoriatic fibroblasts but not in controls. As a control, retinoic acid had no effect in any of the two cell types. It is concluded that in primary normal human fibroblasts, c-myc RNA levels are not correlated with the proliferative state, and that there is an altered expression of this proto-oncogene in psoriasis. 相似文献
60.