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   47792篇
  免费   4581篇
  国内免费   2707篇
电工技术   2227篇
技术理论   2篇
综合类   3925篇
化学工业   4701篇
金属工艺   2861篇
机械仪表   3484篇
建筑科学   1326篇
矿业工程   1625篇
能源动力   658篇
轻工业   5793篇
水利工程   463篇
石油天然气   1591篇
武器工业   920篇
无线电   7477篇
一般工业技术   3812篇
冶金工业   2342篇
原子能技术   456篇
自动化技术   11417篇
  2024年   211篇
  2023年   697篇
  2022年   1110篇
  2021年   1437篇
  2020年   1403篇
  2019年   1081篇
  2018年   1017篇
  2017年   1376篇
  2016年   1493篇
  2015年   1781篇
  2014年   2564篇
  2013年   2554篇
  2012年   3225篇
  2011年   3587篇
  2010年   2581篇
  2009年   2695篇
  2008年   2677篇
  2007年   3242篇
  2006年   2901篇
  2005年   2610篇
  2004年   2166篇
  2003年   2010篇
  2002年   1641篇
  2001年   1341篇
  2000年   1237篇
  1999年   927篇
  1998年   830篇
  1997年   757篇
  1996年   665篇
  1995年   517篇
  1994年   506篇
  1993年   414篇
  1992年   321篇
  1991年   268篇
  1990年   238篇
  1989年   204篇
  1988年   147篇
  1987年   85篇
  1986年   72篇
  1985年   88篇
  1984年   69篇
  1983年   81篇
  1982年   57篇
  1981年   41篇
  1980年   31篇
  1979年   29篇
  1978年   19篇
  1977年   24篇
  1976年   13篇
  1973年   9篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
叠后高分辨率资料处理方法及应用效果   总被引:2,自引:0,他引:2  
高分辨率勘探是一项系统工程,它由多个环节组成。甚至叠后高发辨率资料处理也是由多个环节组成。本文介绍的叠后高分辨率资料处理流程主要包括Lp模自适应预测统计反褶积,高频成分补偿,振幅补偿及有色成分校正。文中还就处理流程中各种方法的合理组合,各种方法自身参数的合理选取作了试验和探讨,最后给出了处理实例。  相似文献   
102.
A new concept, the generalized inverse group (GIG) of signal, is firstly proposed and its properties, leaking coefficients and implementation with neural networks are presented. Theoretical analysis and computational simulation have shown that (1) there is a group of finite length of generalized inverse signals for any given finite signal, which forms the GIG; (2) each inverse group has different leaking coefficients, thus different abnormal states; (3) each GIG can be implemented by a grouped and improved single-layer perceptron which appears with fast convergence. When used in deconvolution, the proposed GIG can form a new parallel finite length of filtering deconvolution method. On off-line processing, the computational time is reduced to O(N) from O(N2). And the less the leaking coefficient is, the more reliable the deconvolution will be.  相似文献   
103.
In this paper, the evaluation by running window smoothing is used for the digital processing of the polarization of geophysical ULF signals. The observed signals are resolved into two orthogonal complex components so that it is no longer necessary to consider the phase and amplitude of the signals simultaneously.  相似文献   
104.
The various parameters related to sol-gel processing are discussed with special reference to those which usually attract less attention but depending on the final product in mind, can play important roles. The versatility of the sol-gel technique in materials preparation is demonstrated by discussing the various products developed at the author’s laboratory by using this processing method.  相似文献   
105.
对薄板成形应变场传统的测量方法进行了研究。指出了其不足和误差的来源,提出了数字图像分析法测量薄板成形中的应变场,对测量原理,新的测量方法对传统方法的改进,以及如何降低误差进行了介绍,指出数字图像分析法的前景,提出了改进意见。  相似文献   
106.
We have isolated a mutant which exhibits partial constitutivity for a -specific gene expression in α cells. The wild-type gene was cloned and demonstrated to be allelic to the STE13 gene, which encodes the dipeptidyl aminopeptidase involved in processing of the α-factor prepropheromone. Thus, the mating defect of the ste13 mutations in α cells may result both from the production of incompletely processed α-factor and from the increased expression of a -specific genes. The STE13 open reading frame of 931 amino acids contains a putative membrane-spanning segment near its amino terminus and is 31% identical to a second yeast dipeptidyl aminopeptidase (DAP2). A null mutant of STE13 has been constructed: it is viable and sporulation-proficient. The sequence has been deposited in the GenBank data library under Accession Number L21944.  相似文献   
107.
Based on thermal degradation kinetics and heat transfer expressed as the Ball formula method, a simplified approach was used to optimize sterilization processes for thermal softening of white beans (Phaseolus vulgaris, subsp. nanus Metz., variety Manteca de Leon) Constant retort profiles in a still and end-over-end rotary water cascading retort (Barriquand Steriflow) were used. Quality attributes of beans processed at the optimum were evaluated by a trained taste panel and by a tenderometer. Both approaches could distinguish (P<0.01) between attributes of products from optimal rotary and still processes. End-over-end rotation resulted in faster heat penetration and better quality retention of beans. Texture of white beans processed at 4° or 8°C from the optimal temperature could be distinguished (P<0.01) by the sensory panel and by the tenderometer.  相似文献   
108.
Pb0.4Bi1.8Sr2Ca2.2Cu3Ox (Bi-2223) precursor powder was prepared by a solid-state reaction of carbonates and oxides of lead, bismuth, strontium, calcium, and copper, and the powder was then used to fabricate silver-clad tapes by the powder-in-tube technique. Transport critical current density (Jc) values>4×104 A/cm2 at 77K and 2×105 A/cm2 at 4.2 and 27K have been achieved in short tape samples. Long lengths of tape were tested by winding them into pancake coils. Recently, we fabricated a test magnet by stacking ten pancake coils, each containing three 16m lengths of rolled tape, and tested it at 4.2, 27 and 77K. A maximum generated field of 2.6 T was measured in zero applied field at 4.2K and the test magnet generated significant self-field in background fields up to 20 T. The results are discussed in this paper.  相似文献   
109.
110.
Relative grain boundary energies can be simply related to true dihedral angles, which are the angles between grain boundary planes meeting at triple edges in polycrystals. Some limited efforts in the measurement of true dihedral angles have used the technique of serial sectioning, which is usually cumbersome and time consuming. In this study the three‐dimensional probe called the ‘disector’ has been employed to evaluate true dihedral angles. This probe, combined with automated image processing, introduces precision as well as efficiency, overcomes the disadvantages of the two‐dimensional probe and is far less tedious and less complicated than serial sectioning. It is shown that the technique is relatively simple and therefore can be applied to obtain a significantly large and accurate statistical sample of true dihedral angles. The application of this method is demonstrated by evaluating the triple junction geometry and the associated relative grain boundary energies in polycrystalline 316L austenitic stainless steel.  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