全文获取类型
收费全文 | 30284篇 |
免费 | 2922篇 |
国内免费 | 1275篇 |
专业分类
电工技术 | 1754篇 |
综合类 | 1523篇 |
化学工业 | 5173篇 |
金属工艺 | 1861篇 |
机械仪表 | 2086篇 |
建筑科学 | 1804篇 |
矿业工程 | 794篇 |
能源动力 | 1129篇 |
轻工业 | 2286篇 |
水利工程 | 455篇 |
石油天然气 | 1329篇 |
武器工业 | 179篇 |
无线电 | 3985篇 |
一般工业技术 | 4732篇 |
冶金工业 | 1558篇 |
原子能技术 | 296篇 |
自动化技术 | 3537篇 |
出版年
2024年 | 127篇 |
2023年 | 565篇 |
2022年 | 997篇 |
2021年 | 1417篇 |
2020年 | 1065篇 |
2019年 | 917篇 |
2018年 | 1050篇 |
2017年 | 1030篇 |
2016年 | 1081篇 |
2015年 | 1212篇 |
2014年 | 1585篇 |
2013年 | 1876篇 |
2012年 | 1998篇 |
2011年 | 2246篇 |
2010年 | 1957篇 |
2009年 | 1834篇 |
2008年 | 1718篇 |
2007年 | 1472篇 |
2006年 | 1357篇 |
2005年 | 1250篇 |
2004年 | 918篇 |
2003年 | 901篇 |
2002年 | 873篇 |
2001年 | 768篇 |
2000年 | 653篇 |
1999年 | 632篇 |
1998年 | 581篇 |
1997年 | 457篇 |
1996年 | 392篇 |
1995年 | 339篇 |
1994年 | 272篇 |
1993年 | 187篇 |
1992年 | 152篇 |
1991年 | 100篇 |
1990年 | 97篇 |
1989年 | 84篇 |
1988年 | 55篇 |
1987年 | 40篇 |
1986年 | 36篇 |
1985年 | 26篇 |
1984年 | 27篇 |
1983年 | 19篇 |
1982年 | 15篇 |
1981年 | 27篇 |
1980年 | 15篇 |
1979年 | 8篇 |
1978年 | 9篇 |
1977年 | 8篇 |
1976年 | 12篇 |
1973年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
42.
标准化的目的是“获得最佳秩序和社会效益”,而最佳秩序是企业进行高效率生产和管理的前提条件。能够更及时准确的对企业的生产标准、技术标准、安全标准、管理标准进行监督和管理工作;有助于更好的督促企业在每个环节都建立起互相适应、配套的标准体系,使企业生产活动和经营管理活动井然有序,避免混乱;能够进一步加强对认证及认证咨询工作的质量,提高认证企业质量体系运行的有效性。为此我们提出了建设《哈尔滨市企业产品执行标准数据库管理系统》,对企业的产品执行标准进行登记注册管理,这将有助于组织、监督标准实施工作;有助于组织制订地方标准;推行采用国际标准和国外先进标准;有助于协调指导企业产品标准的制订并管理其备案;组织重要标准的宣传贯彻,监督检查重要标准的实施情况。 相似文献
43.
To determine three‐dimensional fiber orientation states in injection‐molded short‐fiber composites, a confocal laser scanning microscope (CLSM) is used. Since the CLSM optically sections the specimen, more than two images of the cross sections on and below the surface of the composite can be obtained. Three‐dimensional fiber orientation states can be determined by using geometric parameters of fiber images obtained from two parallel cross sections. For experiments, carbon‐fiber‐reinforced polystyrene is examined by the CLSM and geometric parameters of fibers on each cross‐sectional plane are measured by an image analysis. In order to describe fiber orientation states compactly, orientation tensors are determined at different positions of the prepared specimen. Three‐dimensional orientation states are obtained without any difficulty by determining the out‐of‐plane angles utilizing fiber images on two parallel planes acquired by the CLSM. Orientation states are different at different positions and show the shell–core structure along the thickness of the specimen. Fiber orientation tensors are predicted by a numerical analysis and the numerically predicted orientation states show good agreement with measured ones. However, some differences are found at the end of cavity. They may result from the fountain flow effects, which are not considered in the numerical analysis. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 500–509, 2003 相似文献
44.
介绍了一种日常参数智能控制器的研制及研制过程中的几个重要问题的解决方法。特别是用于城市照明及美化城市的彩灯的开、关时间智能控制方面,给出了依据当地绝对时间、经度、纬度进行昼夜时间计算的方法,使之在不接光电传感器情况下可跟踪季节的昼夜变化。控制系统采用89C2051单片机,配有时钟日历芯片DS12887,系统体积小、功能强、可靠性高。 相似文献
45.
Ki Hyun Kim Yong Hoon Kang Byoungho Lee 《Photonics Technology Letters, IEEE》1997,9(12):1610-1612
A photorefractive volume hologram was recorded and probed using light diffracted from a tapered optical fiber as a reference beam. A single-mode fiber (SMF) was chemically etched and tapered to give a complicated beam pattern, and it is shown that the tapered optical fiber can be utilized to increase the storage density of the volume hologram. Spatial selectivity of the volume hologram with this method was increased by two times compared to the normal SMF referencing, which is due to the fact that the complicated beam pattern has little correlation with its shifted version 相似文献
46.
DH Kang CL Coe DO McCarthy NN Jarjour EA Kelly RR Rodriguez WW Busse 《Canadian Metallurgical Quarterly》1997,17(8):481-487
T cell cytokines play an important role in mediating airway inflammation in asthma. The predominance of a Th2 cytokine profile, particularly interleukin (IL)-4 and IL-5, is associated with the pathogenesis and course of asthma. The aim of this study was to test the hypothesis that a stressful life event alters the pattern of cytokine release in asthmatic individuals. Thirteen healthy controls and 21 asthmatic adolescents gave blood samples three times over a semester: midsemester, during the week of final examinations, and 2-3 weeks after examinations. Interferon-gamma (IFN-gamma), IL-2, IL-4, and IL-5 were measured from supernatants of cells stimulated with PHA/PMA for 24 h. Cells from asthmatic subjects released significantly more IL-5 during the examination and postexamination periods, whereas cells from healthy controls released significantly more IL-2 during the midsemester and examination periods, thereby indicating a bias for a Th2-like pattern in asthmatics and a Th1-like pattern in healthy controls. IL-4 and IL-5 production showed a marked decrease during and after examinations in healthy controls, whereas this decline was absent in asthmatics. The ratios of IFN-gamma:IL-4 and IFN-gamma:IL-5 also revealed significant changes in the profile of cytokine release across the semester. These results indicate differential cytokine responses in asthmatics that may become pronounced during periods of cellular activation. 相似文献
47.
Ju D.-C.R. Chuan-Lin Wu Carini P. 《Parallel and Distributed Systems, IEEE Transactions on》1994,5(10):1113-1120
We present a classification scheme for array language primitives that quantifies the variation in parallelism and data locality that results from the fusion of any two primitives. We also present an algorithm based on this scheme that efficiently determines when it is beneficial to fuse any two primitives. Experimental results show that five LINPACK routines report 50% performance improvement from the fusion of array operators 相似文献
48.
2Mbit/s高速信令链路在移动通信七号信令网中的应用 总被引:1,自引:0,他引:1
通过对2Mbit/s高速信令链路原理、特点的介绍,阐明了该技术在现阶段使用的实际意义,并给出了2Mbit/s高速信令链路在移动通信七号信令网中的应用。 相似文献
49.
50.