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   2112篇
  免费   33篇
  国内免费   34篇
电工技术   43篇
综合类   43篇
化学工业   256篇
金属工艺   58篇
机械仪表   54篇
建筑科学   104篇
矿业工程   5篇
能源动力   81篇
轻工业   147篇
水利工程   18篇
石油天然气   15篇
武器工业   2篇
无线电   143篇
一般工业技术   175篇
冶金工业   928篇
原子能技术   11篇
自动化技术   96篇
  2022年   8篇
  2021年   12篇
  2020年   3篇
  2019年   9篇
  2018年   10篇
  2017年   16篇
  2016年   11篇
  2015年   25篇
  2014年   85篇
  2013年   73篇
  2012年   52篇
  2011年   136篇
  2010年   43篇
  2009年   93篇
  2008年   62篇
  2007年   79篇
  2006年   67篇
  2005年   50篇
  2004年   57篇
  2003年   48篇
  2002年   41篇
  2001年   39篇
  2000年   29篇
  1999年   35篇
  1998年   290篇
  1997年   171篇
  1996年   138篇
  1995年   76篇
  1994年   66篇
  1993年   56篇
  1992年   28篇
  1991年   18篇
  1990年   24篇
  1989年   27篇
  1988年   18篇
  1987年   13篇
  1986年   3篇
  1985年   15篇
  1984年   8篇
  1983年   10篇
  1982年   5篇
  1981年   8篇
  1980年   9篇
  1978年   9篇
  1977年   31篇
  1976年   52篇
  1975年   5篇
  1970年   3篇
  1969年   2篇
  1955年   2篇
排序方式: 共有2179条查询结果,搜索用时 31 毫秒
991.
A shearing interference microscope using a Savart prism as the shear plate is proposed for inspecting step‐heights. Where the light beam propagates through the Savart prism and microscopic system to illuminate the sample, it then turns back to re‐pass through the Savart prism and microscopic system to generate a shearing interference pattern on the camera. Two measurement modes, phase‐shifting and phase‐scanning, can be utilized to determine the depths of the step‐heights on the sample. The first mode, which employs a narrowband source, is based on the five‐step phase‐shifting algorithm and has a measurement range of a quarter‐wavelength. The second mode, which adopts a broadband source, is based on peak‐intensity identification technology and has a measurement range up to a few micrometres. This paper is to introduce the configuration and measurement theory of this microscope, perform a setup used to implement it, and present the experimental results from the uses of the setup. The results not only verify the validity but also confirm the high measurement repeatability of the proposed microscope.  相似文献   
992.
Altered antigen presentation in mice lacking H2-O   总被引:1,自引:0,他引:1  
The phenomenon of transgenerational traumatization has currently become widely recognized and described, although the task of disentangling the underlying interactional mechanisms remains a difficult one. These transgenerational mechanisms were first detected in families of the survivors of the Holocaust, but they may be equally prominent in families of parents who have been traumatized in other ways, for example, as victims of child neglect and abuse, as orphaned children, or during military service. In cases in which parents have themselves been subjected to early parental deprivation, one or more children may become projectively identified with a parent's (posttraumatic) "bad child"-self, whereas the parent him/herself has identified with--enacts the role of--the idealized internal "martyr" parent. A case study is presented describing the individual and family therapeutic treatment of a woman who, as a child, had been traumatically separated from her parents.  相似文献   
993.
Influenza polymer-subunit vaccine "Grippol", made up of the sterile conjugate of surface proteins of influenza viruses, groups A and B, with polyoxidonium (copolymer), was obtained at the State Scientific Centre of Research Institute of Immunology. As the result of our investigations, the coefficient of prophylactic effectiveness of vaccine "Grippol" was found to be 71%; in the presence of the 50% immune stratum in the group the coefficient of antiepidemic protection was found to be 66.4%. At the same time, cases of influenza and acute respiratory diseases were shown to take a milder form in persons immunized with vaccine "Grippol" than in the group of nonimmunized subjects. The results of this investigation did not show any side effects caused by the vaccine.  相似文献   
994.
The aim of this pilot study in 54 patients was to improve the visualization of the anatomy and postoperative changes in the pelvic topography after bilateral ureteroileal urethrostomy, using surface rendering of electron beam CT (EBCT) data for the 3D display. Fifty-four patients (39 men and 15 women) were scanned with an EBCT unit between 3 and 110 months after performing orthotopic ureteroileal urethrostomy ("Hemi-Kock") or ureteroileal rectosigmoidostomy. Various parameters and spatial viewing points were used in the 3D reconstruction, which was performed interactively on external workstations with commercially available software. The anti-reflux nipple was visualized as a distinct structure in all patients. In 8 patients with an interval of more than 12 months between surgery and CT, the pouch had developed an ovoid shape almost indistinguishable from the original bladder. The segmented data sets were partly animated to display the anatomy as virtual endoscopy. Three-dimensional depiction and virtual endoscopy of the neobladder using EBCT are a new way of imaging the postoperative anatomy. Its clinical efficacy in the diagnosis of inconclusive postoperative morbidity, especially voiding problems, and planning of necessary therapy have to be the subject of further evaluation.  相似文献   
995.
基于通用FLAC的模糊自适应UKF算法及其应用   总被引:1,自引:0,他引:1  
针对量测噪声方差统计值未知的非线性UKF(Unscented Kalman Filter)滤波问题,提出了一种基于通用FLAC(Fussy Logic Adaptive Controller)的模糊自适应UKF算法.在标准的非线性UKF算法基础上,以残差的实际方差与理论方差的比值作为FLAC的输入,使FLAC对滤波模型的依赖性减弱,强化了模糊自适应UKF方法的通用性;在对未知的量测噪声方差阵进行动态调节的过程中设置了指数调节参数,可不同程度地放大或缩小方差阵调节的幅度,使算法的调节速度和精度得到控制.将算法应用于GPS/DR(Dead-Reckoning)组合导航系统中,仿真结果表明了该算法的有效性.  相似文献   
996.
The decentralized control scheme for routing in current IP networks has been questioned, and a centralized routing scheme has been proposed as an alternative. In this paper, we compare the convergence of centralized control scheme with decentralized link-state routing protocols. We first review the architectural advantages and challenges of centralized control. Thereafter, we identify and discuss the components of the convergence time in both schemes. We present how to achieve fast routing convergence in networks with centralized control. In particular, we analyze how to distribute forwarding information efficiently. Finally, we perform simulation studies on the convergence time for both real and synthetic network topologies and study the impact of control element location, link weights, and number of failures on the convergence time. The results show that the centralized control scheme can provide faster routing convergence than link-state routing protocols.  相似文献   
997.
在研究Word VBA和Powerpoint VBA的基础上,对Word对象和Powerpoint对象深入研究,提出PPT文档转化为Word文档的完美解决方案,研究和开发了对应的转换系统。  相似文献   
998.
999.
This work presents a particle filter method closely related to Fastslam for solving the simultaneous localization and mapping (slam) problem. Using the standard Fastslam algorithm, only low-dimensional vehicle models can be handled due to computational constraints. In this work, an extra factorization of the problem is introduced that makes high-dimensional vehicle models computationally feasible. Results using experimental data from an unmanned aerial vehicle (helicopter) are presented. The proposed algorithm fuses measurements from on-board inertial sensors (accelerometer and gyro), barometer, and vision in order to solve the slam problem.  相似文献   
1000.
Muscle fibre type composition and glycogen depletion pattern at slaughter as related to meat quality, were studied in M. longissimus dorsi of halothane-gene-free Swedish Yorkshire pigs fed a high (n=19; 10 entire males and 9 gilts) or a low (n=18; 10 entire males and 8 gilts) protein diet. The muscle consisted of, on average, 8% type I, 9% type IIA and 83% type IIB fibres. Muscle fibre areas were significantly smaller in entire male pigs than in gilts irrespective of fibre type. There were no marked differences in muscle characteristics between pigs fed the low and high protein diets. Low glycogen concentrations were found in most type I and type IIA muscle fibres, while a greater variation in glycogen content was evident in type IIB fibres. The pigs were divided into two groups according to the proportion of glycogen depleted IIB fibres (more or less than 30% depleted IIB fibres). In the group where 30% or more of the type IIB fibres were glycogen depleted, a tendency toward DFD meat (dry, firm, dark) was seen, as the meat had higher ultimate pH (5·62 vs 5·52; p=0·02), lower drip loss (2·7% vs 4·4%; p=0·007) and lower reflectance value (darker meat; 16·5 vs 20·6 EEL units; p=0·0005), compared with the group with less than 30% depleted IIB fibres. No difference in total glycogen content was found between these two groups. This indicates that the distribution of glycogen in different fibre types seems to be of importance for the ultimate meat quality.  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