全文获取类型
收费全文 | 67609篇 |
免费 | 6080篇 |
国内免费 | 3086篇 |
专业分类
电工技术 | 3987篇 |
技术理论 | 2篇 |
综合类 | 4372篇 |
化学工业 | 11316篇 |
金属工艺 | 3908篇 |
机械仪表 | 4283篇 |
建筑科学 | 4955篇 |
矿业工程 | 2254篇 |
能源动力 | 1789篇 |
轻工业 | 4377篇 |
水利工程 | 1164篇 |
石油天然气 | 4200篇 |
武器工业 | 558篇 |
无线电 | 8066篇 |
一般工业技术 | 8214篇 |
冶金工业 | 3170篇 |
原子能技术 | 750篇 |
自动化技术 | 9410篇 |
出版年
2024年 | 390篇 |
2023年 | 1216篇 |
2022年 | 2017篇 |
2021年 | 2797篇 |
2020年 | 2125篇 |
2019年 | 1873篇 |
2018年 | 2052篇 |
2017年 | 2268篇 |
2016年 | 2035篇 |
2015年 | 2672篇 |
2014年 | 3216篇 |
2013年 | 3868篇 |
2012年 | 4344篇 |
2011年 | 4743篇 |
2010年 | 3935篇 |
2009年 | 3729篇 |
2008年 | 3578篇 |
2007年 | 3477篇 |
2006年 | 3857篇 |
2005年 | 3201篇 |
2004年 | 2247篇 |
2003年 | 1919篇 |
2002年 | 1673篇 |
2001年 | 1530篇 |
2000年 | 1623篇 |
1999年 | 1795篇 |
1998年 | 1574篇 |
1997年 | 1323篇 |
1996年 | 1207篇 |
1995年 | 1001篇 |
1994年 | 888篇 |
1993年 | 596篇 |
1992年 | 449篇 |
1991年 | 384篇 |
1990年 | 278篇 |
1989年 | 225篇 |
1988年 | 190篇 |
1987年 | 130篇 |
1986年 | 101篇 |
1985年 | 59篇 |
1984年 | 32篇 |
1983年 | 21篇 |
1982年 | 29篇 |
1981年 | 16篇 |
1980年 | 22篇 |
1979年 | 10篇 |
1978年 | 7篇 |
1977年 | 5篇 |
1976年 | 14篇 |
1975年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
SL Nyberg HJ Mann MY Hu WD Payne WS Hu FB Cerra RP Remmel 《Canadian Metallurgical Quarterly》1996,24(6):643-648
OBJECTIVE: The initially well-fixed implants of total hip replacement (THR) are in the long-term subject to aseptic loosening. Many cytokines can contribute to osteolysis due to osteoclast recruitment and/or activation. However, in this respect tumor necrosis factor-alpha (TNF-alpha) plays a pivotal role, because it upregulates interleukin-1 and 6 and granulocyte-macrophage colony stimulating factor. The aim of this study was to assess the eventual presence, cellular localization and extent of expression of TNF-alpha in the synovial-like membrane at the implant or at the cement to bone interface compared to control synovial membrane. METHODS: Twenty samples from the synovial-like membrane of the periprosthetic tissues were compared to control samples. TNF-alpha containing cells were visualized using an avidin-biotin-peroxidase complex (ABC) method and analyzed by light microscopy, double labelling and image analysis. RESULTS: TNF-alpha was found in the periprosthetic tissues in fibroblasts and vascular endothelial cells, but mainly in the macrophages was it found to coincide with areas containing implant-derived debris. TNF-alpha containing cells were more numerous in the synovial-like membrane in the interface tissue from the proximal stem area (2816 +/- 318 cells) than in the control synovial membrane (565 +/- 93 cells, p < 0.01). Interestingly, similarly high TNF-alpha expression (3452 +/- 582 cells) was also seen in the synovial-like membrane of the pseudocapsule. CONCLUSION: These findings suggest that the foreign body-type host reaction caused by THR is characterized by the high expression of TNF-alpha. Because such expression occurred in the interface tissue between the implant and surrounding bone, TNF-alpha, due to its pivotal direct and indirect role in the activation and recruitment of osteoclasts, may contribute to periprosthetic osteolysis and to the loosening of THR. 相似文献
42.
Xiaolin Hu Jun Wang 《IEEE transactions on systems, man, and cybernetics. Part B, Cybernetics》2007,37(3):528-539
This paper presents a recurrent neural-network model for solving a special class of general variational inequalities (GVIs), which includes classical VIs as special cases. It is proved that the proposed neural network (NN) for solving this class of GVIs can be globally convergent, globally asymptotically stable, and globally exponentially stable under different conditions. The proposed NN can be viewed as a modified version of the general projection NN existing in the literature. Several numerical examples are provided to demonstrate the effectiveness and performance of the proposed NN. 相似文献
43.
44.
小口径弹道炮在使用初期,弹道特性值偏高,影响产品的验收和标准弹的鉴选.该文用膛阻理论解释弹道炮使用的各个时期的弹道特性变化,并介绍了“光膛”射击后,在弹道曲线下降段进行产品验收以及标准弹鉴选中的实际应用. 相似文献
45.
The computation of exact geodesics on triangle meshes is a widely used operation in computer-aided design and computer graphics. Practical algorithms for computing such exact geodesics have been recently proposed by Surazhsky et al. [5]. By applying these geometric algorithms to real-world data, degenerate cases frequently appear. In this paper we classify and enumerate all the degenerate cases in a systematic way. Based on the classification, we present solutions to handle all the degenerate cases consistently and correctly. The common users may find the present techniques useful when they implement a robust code of computing exact geodesic paths on meshes. 相似文献
46.
2007年1-10月,我国的粗钢产量达到4.09亿吨,同比增长18.14%。10月单月产量4292.2万吨,再创单月产量新高;1-10月,钢材产量达4.67亿吨(含重复材),同比增长23.53%,10月钢材产量 相似文献
47.
48.
岩石样品中铷的中子活化分析 总被引:1,自引:0,他引:1
研究了苦味酸溶液的pH变化对用18-C-6(18C6)的硝基苯溶液定量萃取Rb的影响及18C6浓度变化对定量萃取Rb的影响,确定了定量反萃Rb的实验条件。作出了磷酸锆无机离子交换柱上的Rb-Cs分离曲线。测定了岩石样品的微量Rb和痕量^84Rb。 相似文献
49.
50.
Random-effects regression modelling is proposed for analysis of correlated grouped-time survival data. Two analysis approaches are considered. The first treats survival time as an ordinal outcome, which is either right-censored or not. The second approach treats survival time as a set of dichotomous indicators of whether the event occurred for time periods up to the period of the event or censor. For either approach both proportional hazards and proportional odds versions of the random-effects model are developed, while partial proportional hazards and odds generalizations are described for the latter approach. For estimation, a full-information maximum marginal likelihood solution is implemented using numerical quadrature to integrate over the distribution of multiple random effects. The quadrature solution allows some flexibility in the choice of distributions for the random effects; both normal and rectangular distributions are considered in this article. An analysis of a dataset where students are clustered within schools is used to illustrate features of random-effects analysis of clustered grouped-time survival data. 相似文献