全文获取类型
收费全文 | 8313篇 |
免费 | 208篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 54篇 |
综合类 | 4篇 |
化学工业 | 964篇 |
金属工艺 | 76篇 |
机械仪表 | 101篇 |
建筑科学 | 162篇 |
矿业工程 | 27篇 |
能源动力 | 106篇 |
轻工业 | 360篇 |
水利工程 | 65篇 |
石油天然气 | 10篇 |
无线电 | 263篇 |
一般工业技术 | 875篇 |
冶金工业 | 4875篇 |
原子能技术 | 34篇 |
自动化技术 | 550篇 |
出版年
2023年 | 25篇 |
2022年 | 44篇 |
2021年 | 79篇 |
2020年 | 59篇 |
2019年 | 90篇 |
2018年 | 84篇 |
2017年 | 78篇 |
2016年 | 107篇 |
2015年 | 79篇 |
2014年 | 110篇 |
2013年 | 264篇 |
2012年 | 210篇 |
2011年 | 297篇 |
2010年 | 224篇 |
2009年 | 197篇 |
2008年 | 260篇 |
2007年 | 246篇 |
2006年 | 212篇 |
2005年 | 180篇 |
2004年 | 147篇 |
2003年 | 133篇 |
2002年 | 119篇 |
2001年 | 92篇 |
2000年 | 80篇 |
1999年 | 177篇 |
1998年 | 1246篇 |
1997年 | 780篇 |
1996年 | 525篇 |
1995年 | 293篇 |
1994年 | 281篇 |
1993年 | 278篇 |
1992年 | 94篇 |
1991年 | 70篇 |
1990年 | 91篇 |
1989年 | 94篇 |
1988年 | 75篇 |
1987年 | 84篇 |
1986年 | 81篇 |
1985年 | 64篇 |
1984年 | 45篇 |
1983年 | 50篇 |
1982年 | 57篇 |
1981年 | 59篇 |
1980年 | 81篇 |
1979年 | 21篇 |
1978年 | 30篇 |
1977年 | 127篇 |
1976年 | 281篇 |
1975年 | 22篇 |
1973年 | 17篇 |
排序方式: 共有8526条查询结果,搜索用时 46 毫秒
71.
JF Platt 《Canadian Metallurgical Quarterly》1996,34(6):1113-1129
Radiologic imaging is commonly used in the diagnosis, classification, and follow-up of renal obstruction. Precise definitions of the elements of urinary obstruction are critical. This article examines the physiology of renal obstruction and the use of such imaging tests as excretory urogram, retrograde pyelography, antegrade pyelography, Whitaker test, ultrasound, CT scan, MR imaging, and radionuclide renography. 相似文献
72.
73.
Robert G. Whirley Gregory A. Henshall 《International journal for numerical methods in engineering》1992,35(7):1427-1442
This paper presents a fast numerical algorithm for the implementation of material models for creep into finite element codes. First, an overview of existing algorithms for transient and steady-state creep is given. Next, a new formulation is presented which reduces the constitutive integration to the solution of a scalar non-linear algebraic equation. A solution is shown to exist without the need for subincrementation. Details of the numerical algorithm are then discussed. The paper closes with several numerical examples which illustrate the speed, robustness and accuracy of the proposed procedure as implemented in the Lawrence Livermore National Laboratory finite element codes NIKE2D and NIKE3D. 相似文献
74.
It is important to monitor the early stages of postoperative wound repair in order to identify those problems associated with impaired healing. Many of the crucial cellular responses of early wound healing, such as inflammatory infiltration, angiogenesis and re-epithelialization, are made possible through the action of matrix metalloproteinases (MMPs). Expression of MMP-2 and MMP-9 is elevated in acute wounds, and still greater levels are found in chronic wounds, indicating that uncontrolled proteolysis is a characteristic of retarded healing. Therefore, comparative measurements of MMPs may be used to monitor the progression of early wound healing. To investigate this, wound fluids and sera were collected from mastectomy and colectomy patients throughout early stages of repair, and the temporal expression profile established. Wounds which were healing were expressed maximal levels of MMP-9 at 24 h, followed by a significant decline by 48 h. Persistent elevation of MMP-9 expression was associated with infected and chronic wounds, and was identified in postoperative wounds by the absence of the significant decline between 24 and 48 h. Measurement of MMP-9 in postoperative wound fluids, therefore, provides an early indicator of impaired healing, which may be evaluated non-invasively within 48 h of closure. 相似文献
75.
76.
77.
78.
A new online streaming video and multi‐media application called eTEACH, http:eTEACH.engr.wisc.edu was used to reform a large, lecture‐based computer science course for engineering majors. In‐class lectures were replaced with videotaped lectures and other materials that students viewed on the Internet on their own schedule, making it possible to use the live class periods for small, team problem‐solving sessions facilitated by the professors and a teaching assistant. By using the eTEACH application to transform course lectures into “homework” and free up the face‐to‐face class time for working on problems that were similar to homework assignments, the professors effectively reversed the lecture and homework paradigm of a typical large lecture course. A thorough course evaluation over two semesters showed that students who took the online lecture version of the course gave significantly higher ratings to all aspects of the course, including lecture usefulness, professor responsiveness, the course overall, and the instructor. Although a few students missed having the opportunity to ask questions during lectures, about two‐thirds of the 531 students surveyed felt it was easier to take notes and understand the lectures presented via eTEACH than it would have been while attending the same lecture live, and 78% of students appreciated the ability to view and review course lectures on their own schedule. 相似文献
79.
80.