首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   121998篇
  免费   10756篇
  国内免费   5868篇
电工技术   7418篇
技术理论   6篇
综合类   8340篇
化学工业   20151篇
金属工艺   6974篇
机械仪表   7916篇
建筑科学   9157篇
矿业工程   3414篇
能源动力   3343篇
轻工业   8266篇
水利工程   2247篇
石油天然气   6464篇
武器工业   1002篇
无线电   15096篇
一般工业技术   15250篇
冶金工业   5425篇
原子能技术   1368篇
自动化技术   16785篇
  2024年   575篇
  2023年   1972篇
  2022年   3455篇
  2021年   4847篇
  2020年   3622篇
  2019年   3217篇
  2018年   3472篇
  2017年   3870篇
  2016年   3687篇
  2015年   4863篇
  2014年   5922篇
  2013年   7160篇
  2012年   7815篇
  2011年   8631篇
  2010年   7457篇
  2009年   6983篇
  2008年   6879篇
  2007年   6528篇
  2006年   6840篇
  2005年   5810篇
  2004年   4159篇
  2003年   3758篇
  2002年   3832篇
  2001年   3313篇
  2000年   3052篇
  1999年   2998篇
  1998年   2544篇
  1997年   2130篇
  1996年   1923篇
  1995年   1631篇
  1994年   1407篇
  1993年   1011篇
  1992年   751篇
  1991年   622篇
  1990年   447篇
  1989年   361篇
  1988年   313篇
  1987年   192篇
  1986年   154篇
  1985年   100篇
  1984年   61篇
  1983年   36篇
  1982年   49篇
  1981年   36篇
  1980年   36篇
  1979年   18篇
  1978年   8篇
  1976年   22篇
  1975年   16篇
  1970年   5篇
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
71.
分析了建筑陶瓷企业实施精益生产的条件和当前推行精益生产的主要障碍,对应用中存在的问题进行了分析并提出了相关建议。  相似文献   
72.
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   
73.
文中解决了2-重自补图的计数问题,获得了具有p个顶点的2-重自补图的数目是其中Z(A)表示置换群A的圈指标,S ̄(2)_p表示p次对称群的对群.  相似文献   
74.
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   
75.
76.
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   
77.
78.
Transdermal absorption of zidovudine (AZT) from an ethanol-isopropyl myristate (IPM) mixed system was examined in rats. For comparison of bioavailability (BA) after topical applications, 0.25 ml of the ethanol/IPM system containing 40% ethanol and 60 mM AZT was applied as a standard formulation. Values of the area under the plasma concentration-time curves of AZT for 8 hr (AUC0-8), as indices of BA, following application of various formulations were compared with that of the standard formulation. Then the influence of content of the drug and ethanol, and application volume of the system was evaluated. BA was effectively improved only when the total amount of ethanol applied on the skin was increased. On the other hand, simultaneous transdermal application of AZT and probenecid increased the AU0-8, of AZT without necessitating the increase in ethanol content in the formulation. In addition, coadministered probenecid improved cerebrospinal fluid/plasma concentration ratio of AZT.  相似文献   
79.
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   
80.
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   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号