首页 | 官方网站   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   1891篇
  免费   211篇
  国内免费   152篇
工业技术   2254篇
  2024年   3篇
  2023年   24篇
  2022年   54篇
  2021年   69篇
  2020年   78篇
  2019年   50篇
  2018年   41篇
  2017年   53篇
  2016年   90篇
  2015年   71篇
  2014年   131篇
  2013年   127篇
  2012年   121篇
  2011年   143篇
  2010年   102篇
  2009年   106篇
  2008年   128篇
  2007年   155篇
  2006年   93篇
  2005年   86篇
  2004年   89篇
  2003年   60篇
  2002年   70篇
  2001年   57篇
  2000年   44篇
  1999年   25篇
  1998年   25篇
  1997年   23篇
  1996年   24篇
  1995年   16篇
  1994年   15篇
  1993年   13篇
  1992年   12篇
  1991年   7篇
  1990年   6篇
  1989年   5篇
  1988年   3篇
  1987年   3篇
  1984年   2篇
  1983年   2篇
  1966年   3篇
  1965年   3篇
  1964年   3篇
  1963年   1篇
  1962年   3篇
  1960年   1篇
  1958年   3篇
  1957年   1篇
  1956年   2篇
  1955年   2篇
排序方式: 共有2254条查询结果,搜索用时 31 毫秒
1.
This paper investigates the relationship between economic growth, carbon dioxide (CO2) emissions, and energy consumption with an aim to test the validity of the Environmental Kuznets Curve (EKC) hypothesis in five ASEAN (Association of South East Asian Nations) countries (Indonesia, Malaysia, Philippines, Singapore, and Thailand) by applying the panel smooth transition regression (PSTR) model as a new econometric technique. The PSTR model is more flexible and appropriate for describing cross-country heterogeneity and time instability. Our empirical results strongly rejected the null hypothesis of linearity, and the test for no remaining nonlinearity indicated a model with one transition function and two threshold parameters. The first regime (levels of GDP per capita below 4686 USD) showed that environmental degradation increases with economic growth while the trend was reversed in the second regime (GDP per capita above 4686 USD). The results also showed that energy consumption with either the first or the second regime lead to increase CO2. The overall results support the validity of the EKC hypothesis in the ASEAN countries.  相似文献   
2.
针对压延铜箔在表面处理过程中光面易出现色差的问题,从设备、工艺、人员操作等方面进行成因探讨,并给出了应对措施。  相似文献   
3.
A Lattice Approach to Image Segmentation   总被引:1,自引:0,他引:1  
After a formal definition of segmentation as the largest partition of the space according to a criterion σ and a function f, the notion of a morphological connection is reminded. It is used as an input to a central theorem of the paper (Theorem 8), that identifies segmentation with the connections that are based on connective criteria. Just as connections, the segmentations can then be regrouped by suprema and infima. The generality of the theorem makes it valid for functions from any space to any other one. Two propositions make precise the AND and OR combinations of connective criteria. The soundness of the approach is demonstrated by listing a series of segmentation techniques. One considers first the cases when the segmentation under study does not involve initial seeds. Various modes of regularity are discussed, which all derive from Lipschitz functions. A second category of examples involves the presence of seeds around which the partition of the space is organized. An overall proposition shows that these examples are a matter for the central theorem. Watershed and jump connection based segmentations illustrate this type of situation. The third and last category of examples deals with cases when the segmentation occurs in an indirect space, such as an histogram, and is then projected back on the actual space under study. The relationships between filtering and segmentation are then investigated. A theoretical chapter introduces and studies the two notions of a pulse opening and of a connected operator. The conditions under which a family of pulse openings can yield a connected filter are clarified. The ability of segmentations to generate pyramids, or hierarchies, is analyzed. A distinction is made between weak hierarchies where the partitions increase when going up in the pyramid, and the strong hierarchies where the various levels are structured as semi-groups, and particularly as granulometric semi-groups. The last section is based on one example, and goes back over the controversy about “lattice” versus “functional” optimization. The problem is now tackled via a case of colour segmentation, where the saturation serves as a cursor between luminance and hue. The emphasis is put on the difficulty of grouping the various necessary optimizations into a single one.  相似文献   
4.
对韶钢炼铁厂4号高炉炉况和操作上存在的问题进行了分析,主要原因是原材料质量较差,精料水平低,同时,高炉操作不能完全适应原材料条件.按照上稳下活工艺的原则,采取合理鼓风动能、活跃炉缸工作状态、稳定热制度、合理中部冷却强度、炉顶小高压操作以及使用上部调节手段等一系列措施,使高炉的炉况顺行得到了较大的改善,各项主要技术经济指标取得相应的进步.2001年利用系数达3.024 t/m3·d,焦比达441 kg/t.  相似文献   
5.
供水工程输水隧洞钻爆设计与施工   总被引:1,自引:1,他引:0  
钟伟华 《爆破》2003,20(1):36-38
介绍了采用钻焊法开挖深圳市东部供水工程输水隧洞的掏槽方式,光面爆破参数,装药结构及钻爆作业安排等参数。在近4年的工程实践中,取得了良好的爆破效果和明显的经济效益。  相似文献   
6.
铵油炸药在炮孔爆破中的应用   总被引:1,自引:0,他引:1  
文章介绍了在炮孔直径小于100mm条件下,尤其是光面和预裂爆破中,使用铵油炸药的体会及有关施工工艺.  相似文献   
7.
The smooth fractionator   总被引:8,自引:0,他引:8  
A modification of the general fractionator sampling technique called the smooth fractionator is presented. It may be used in almost every situation in which sampling is performed from distinct items that are uniquely defined, often they are physically separated items or clusters like pieces, blocks, slabs, sections, etc. To each item is associated a ‘guesstimate’ or an associated variable with a more‐or‐less close – and possibly biased ? relationship to the content of the item. The smooth fractionator is systematic sampling among the items arranged according to the guesstimates in a unique, symmetric sequence with one peak and minimal jumps. The smooth fractionator is both very simple to implement and so efficient that it should probably always be used unless the natural sequence of the sampling items is equally smooth. So far, there is no theory for the prediction of the efficiency of smooth fractionator designs in general, and their properties are therefore illustrated with a range of real and simulated examples. At the cost of a slightly more elaborate sampling scheme, it is, however, always possible to obtain an unbiased estimate of the real precision and of some of the variance components. The only real practical problem for always obtaining a high precision with the smooth fractionator is specimen inhomogeneity, but that is detectable at almost no extra cost. With careful designs and for sample sizes of about 10, the sampling variation for the primary, smooth fractionator sampling step may in practice often be small enough to be ignored.  相似文献   
8.
投标竞争的胜负不仅取决于各投标人的综合实力,也取决于投标人的投标策略和投标技巧运用得是否得当。结合莱钢成功招标的经验,从几个方面介绍了成功投标需要注意的一些事项,对今后国际项目投标具有借鉴意义。  相似文献   
9.
对我国酱油酿造几项新技术应用之浅见   总被引:3,自引:0,他引:3  
本文概述了三十年来我国酿造酱油工业开展研究的六项新技术在现阶段的投产可行性,及进一步研究方向的看法。  相似文献   
10.
基于协方差矩阵变换的相干源个数估计   总被引:1,自引:0,他引:1  
正确地估计信号源个数是高分辨阵列信号处理的一个重要组成部分,本文提出了一种相干源个数估计的方法。这种方法是先采用空间平滑技术对信号源去相关,然后对阵列协方差进行酉变换,最后用基于协方差矩阵变换的信息论准则和盖氏半径(Gerschgorin Radii)两种方法估计信号源个数。计算机仿真结果证实了方法的可行性。  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-23

京公网安备 11010802026262号