全文获取类型
收费全文 | 93118篇 |
免费 | 10342篇 |
国内免费 | 6508篇 |
专业分类
电工技术 | 8008篇 |
综合类 | 9373篇 |
化学工业 | 10781篇 |
金属工艺 | 5938篇 |
机械仪表 | 5755篇 |
建筑科学 | 6041篇 |
矿业工程 | 3830篇 |
能源动力 | 2481篇 |
轻工业 | 10741篇 |
水利工程 | 3013篇 |
石油天然气 | 3026篇 |
武器工业 | 1566篇 |
无线电 | 8043篇 |
一般工业技术 | 6949篇 |
冶金工业 | 11231篇 |
原子能技术 | 1426篇 |
自动化技术 | 11766篇 |
出版年
2024年 | 623篇 |
2023年 | 1568篇 |
2022年 | 3616篇 |
2021年 | 4563篇 |
2020年 | 3289篇 |
2019年 | 2240篇 |
2018年 | 2417篇 |
2017年 | 2746篇 |
2016年 | 2513篇 |
2015年 | 3999篇 |
2014年 | 4892篇 |
2013年 | 5822篇 |
2012年 | 7286篇 |
2011年 | 7526篇 |
2010年 | 7205篇 |
2009年 | 6572篇 |
2008年 | 6707篇 |
2007年 | 6513篇 |
2006年 | 5572篇 |
2005年 | 4316篇 |
2004年 | 3192篇 |
2003年 | 2188篇 |
2002年 | 1933篇 |
2001年 | 1788篇 |
2000年 | 1451篇 |
1999年 | 750篇 |
1998年 | 2771篇 |
1997年 | 1583篇 |
1996年 | 1024篇 |
1995年 | 599篇 |
1994年 | 505篇 |
1993年 | 555篇 |
1992年 | 119篇 |
1991年 | 128篇 |
1990年 | 124篇 |
1989年 | 119篇 |
1988年 | 98篇 |
1987年 | 82篇 |
1986年 | 79篇 |
1985年 | 64篇 |
1983年 | 24篇 |
1982年 | 44篇 |
1981年 | 47篇 |
1980年 | 81篇 |
1979年 | 19篇 |
1978年 | 16篇 |
1977年 | 172篇 |
1976年 | 302篇 |
1975年 | 18篇 |
1959年 | 37篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
MA Schuckit 《Canadian Metallurgical Quarterly》1998,59(5):485-494
Interference reflection microscopy (IRM) was used to evaluate the status of cell matrix adhesions in the MCF-7 human mammary carcinoma cell line. Focal contacts were concentrated at the periphery of individual cells or small cell clusters. Close contact was detected as a band at cell peripheries and as localized patches throughout the ventral face of cells. The MCF-7 cells also exhibited a distinctive reflection pattern of an intensity midway between that of either focal or close contact. This novel reflection pattern was located primarily at the periphery of cells and often obscured visualization of focal contacts in live cells. A similar distinctive pattern was absent from the normal tissue-derived MCF-10A mammary epithelial cell line. Immunofluorescence staining using an antiserum that cross-reacts with both alpha(v)beta3 and alpha(v)beta5 integrins revealed a distribution of the vitronectin receptor similar to that of the novel adhesion pattern as well as to that of focal contacts. In addition, IRM demonstrated the presence of "tracks" associated with cells, which were also stained with the vitronectin receptor antiserum. The tracks are apparently residual material left behind as a result of cell migration. When MCF-7 cells were cultured in the absence of estradiol, the tracks were greatly diminished when visualized with either IRM or staining for the vitronectin receptor. In contrast, the addition of 17-beta-estradiol to the medium resulted in an increased presence of the tracks as well as the development of extensive close contacts throughout the ventral surface of cells and cell clusters. Cells treated with the estrogen antagonist ICI 182,720 in the presence of estradiol had few associated tracks, indicating that the process leading to the formation of these structures is dependent on an estrogen receptor-activated pathway. However, the antagonist did not prevent the estradiol-induced formation of extensive close contacts. The extensive close contact as well as the increase in trailing material suggests that estradiol may promote breast tumor cell motility. However, this migratory activity may be mediated by both estrogen receptor-dependent and -independent pathways. 相似文献
72.
MA Warren 《Canadian Metallurgical Quarterly》1996,55(12):276-277
The St. Francis Hospice Program is symbolic of more than 100 years of Franciscan dedication to the people of Hawaii. Since Mother Marianne's arrival in November of 1883, the Sisters of the Third Franciscan Order Syracuse, New York have responded to the calling; "the charity of Christ impels us." It is through this calling that care and comfort for the terminally ill is a part of the mission of St. Francis Healthcare System. The magnificent spirit through which Hospice services have been made possible, is a reflection of God's great generosity to us throughout the years. 相似文献
73.
SD Boden PA Moskovitz MA Morone Y Toribitake 《Canadian Metallurgical Quarterly》1996,21(22):2689-2697
STUDY DESIGN: Cadaveric anatomic and in vivo survival animal studies were performed to develop a new arthrodesis technique for the lumbar spine. OBJECTIVES: To examine the feasibility, efficacy, and safety of a minimally invasive lumbar intertransverse process arthrodesis technique using an osteoinductive growth factor (rhBMP-2) delivered in a collagen sponge carrier. The technique was first developed using a rabbit model and modified for the nonhuman primate (rhesus monkey), a larger animal with the most similar bone biology to humans. SUMMARY OF BACKGROUND DATA: The morbidity of conventional posterolateral lumbar intertransverse process arthrodesis includes graft donor site morbidity; paraspinal muscle devascularization, denervation, and scarring and nonunion in up to 36% of patients. Minimally invasive anterior lumbar interbody arthrodesis techniques have been developed, but these often require a metal implant and carry risks to major vessels and development of retrograde ejaculation. A minimally invasive technique for posterolateral intertransverse process arthrodesis has not been described previously. METHODS: In Part 1, we examined seven New Zealand white rabbits and five rhesus monkeys at necropsy and during nonsurvival surgeries to determine the best access routes and to develop special instruments for video-assisted lateral intertransverse process arthrodesis. In Part 2, 38 New Zealand white rabbits underwent L4-L5 intertransverse process arthrodesis: the "OPEN" group (n = 16) underwent a standard open muscle-splitting approach using rhBMP-2 (bone morphogenetic protein) and collagen as a bone graft substitute; the "video-assisted control" group (n = 6) underwent video-assisted lateral intertransverse process arthrodesis with the collagen implant only (no growth factor); and the "video-assisted-BMP" group (n = 16) underwent video-assisted lateral intertransverse process arthrodesis with rhBMP-2 and collagen as the graft material. In Part 3, rhesus monkeys (n = 4) underwent video-assisted lateral intertransverse process arthrodesis using rhBMP-2 and collagen after laminectomy of L4-L5. RESULTS: In Part 1, we identified expedient, minimally invasive routes to the intertransverse process interval appropriate for each species: an intermuscular approach for the rabbit and a lateral, extramuscular approach for the rhesus monkey. In Part 2, all rabbits in the OPEN and video-assisted-BMP groups achieved solid intertransverse process lumbar fusions when assessed at 10 weeks. There were no neurologic impairments nor any difference between the two groups in the frequency of postoperative infection or other complications. None of the animals in the video-assisted control group showed evidence of fusion. In Part 3, exposure, decortication and grafting with rh-BMP-2 and collagen was accomplished successfully in all four monkeys through the video-assisted minimally invasive approach without complications. CONCLUSION: Video-assisted lateral intertransverse process arthrodesis is a feasible, effective, and safe method of lumbar spinal fusion in the rabbit and rhesus monkey. Use of this arthrodesis procedure will minimize the morbidity of paraspinal muscle denervation and devascularization seen with open intertransverse process fusion techniques, and the use of an osteoinductive growth factor will eliminate the problem of graft donor site morbidity and possibly increase the chances for successful fusion. 相似文献
74.
软件项目进度控制方法研究 总被引:3,自引:0,他引:3
为优化软件项目进度控制过程,使管理者能够对软件项目进度进行有效的跟踪和调整,研究并比较了主要的项目进度控制方法和技术,对甘特图、网络计划技术、关键链技术,对各技术的原理、适用范围、优缺点等进行了分析.为弥补上述技术的不足,引入工业项目进度控制方法--实际进度前锋线法,增强了对软件项目进度的信息统计和工期预测功能.通过对上述几种技术的改进和综合应用,提出了一个高效便捷的进度控制系统的设计方案. 相似文献
75.
马先波 《数字社区&智能家居》2010,(7X):5694-5695
顶岗实习是高职院校重要的实践教学环节,要实现对顶岗实习的有效管理,需要借助网络技术搭建管理平台,实现对参与实习师生的管理与指导。该文在对顶岗实习流程及实习任务分析基础上,运用UML建模方法对系统进行分析建模与设计建模,并提出了系统框架与解决方案。 相似文献
76.
77.
文献的语言风格是作者在语言运用方面的思维定势的体现,对于文献之间语言风格的差异,以前的研究大多采用定性分析的方式加以比较和概括,而在文献检索和文本分类领域需要得到量化的语言风格相似度。该文首先分析文献中词语分布的普遍规律,以先秦八部经典文献为观察语料,发现这些文献中的词语既呈离散分布,又呈集中分布;然后通过计算文献之间词型等级的相关系数,来获取量化的语言风格相似度,构建了八部文献之间的相似度矩阵,验证了语言风格的差异不仅体现在使用的常用词上,还更细微地体现在常用词的使用频率等级上。 相似文献
78.
HALT技术可在产品设计阶段快速消除设计缺陷,缩短研发时间和成本,迅速提高产品的质量和固有可靠性。本文从HALT试验的背景出发,介绍了HALT试验的基本原理和意义。在对HALT箱各方面性能验证的基础上,针对我司11kW变频器,详细讲述了HALT试验的具体操作过程。 相似文献
79.
物联网技术在现今实际应用中是极为普遍的,所谓物联网技术就是以互联网为载体来进行物与物之间信息交换的过程,以及通过互联网将任何物体与物体联系在一起的一种网络,也就是说,物联网实际上就是物物相连的互联网. 相似文献
80.
随着社会经济的发展和城市化进程的加快,全球对交通运输提出了更大的需求和更高的要求。就此,文中提出了一种嵌入式的车牌识别系统设计及具体实现方法,其中具体包括硬件结构、车牌定位算法、字符分割算法、字符识别算法和应用程序的实现。该系统采用DSP数字信号处理器和CPLD芯片来实现系统功能,并保持与PC机之间的高速数据传输,最终提出了一种使用软硬件技术开发的复合USB2.0规范的嵌入式车牌识别系统的方法。可见,嵌入式车牌识别对于维护交通安全和城市治安、防止交通堵塞、实现交通自动化管理有着现实的意义。 相似文献