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   73062篇
  免费   7542篇
  国内免费   4497篇
电工技术   7189篇
技术理论   10篇
综合类   6814篇
化学工业   5184篇
金属工艺   2970篇
机械仪表   5452篇
建筑科学   13638篇
矿业工程   2798篇
能源动力   2333篇
轻工业   3249篇
水利工程   3599篇
石油天然气   4368篇
武器工业   1480篇
无线电   6051篇
一般工业技术   6492篇
冶金工业   2618篇
原子能技术   688篇
自动化技术   10168篇
  2024年   289篇
  2023年   894篇
  2022年   1844篇
  2021年   2241篇
  2020年   2544篇
  2019年   1973篇
  2018年   1854篇
  2017年   2471篇
  2016年   2695篇
  2015年   2995篇
  2014年   4876篇
  2013年   4380篇
  2012年   5644篇
  2011年   5989篇
  2010年   4581篇
  2009年   4430篇
  2008年   4108篇
  2007年   4829篇
  2006年   4408篇
  2005年   3836篇
  2004年   3219篇
  2003年   2629篇
  2002年   2175篇
  2001年   1933篇
  2000年   1527篇
  1999年   1246篇
  1998年   999篇
  1997年   784篇
  1996年   745篇
  1995年   609篇
  1994年   453篇
  1993年   342篇
  1992年   290篇
  1991年   181篇
  1990年   177篇
  1989年   130篇
  1988年   96篇
  1987年   54篇
  1986年   51篇
  1985年   31篇
  1984年   30篇
  1981年   24篇
  1980年   67篇
  1979年   49篇
  1965年   27篇
  1964年   37篇
  1960年   23篇
  1959年   33篇
  1956年   31篇
  1955年   32篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
Information systems (IS) integration is among the most challenging tasks in corporate mergers and acquisitions (M&As). In this paper we propose and illustrate the use of an approach to analyzing and planning post-merger IS integration that extends general theory for IS planning, considering the specific characteristics of the M&A context. We highlight that planning effectiveness is possible to achieve in fundamentally different ways, dependent on the characteristics of the merger or acquisition at hand.
Stefan HenningssonEmail:
  相似文献   
73.
A major factor contributing to the total measuring error of coordinate measuring machines (CMMs) is the performance of the probing sub-system. Probing test methods are typically used to detect errors due to the probing sub-system. The probe performance evaluation method specified in the ANSI B89 standard is investigated in this paper. The sampling plan associated in the probe performance evaluation was tested by using experimental probing data from a CMM. Research findings indicate that the performance of touch trigger probes is overestimated due to a systematic bias in the vertical direction of the best-fit reference ball center in the probe performance test. A two-latitude sampling plan synthesis method based on a pretravel model for touch trigger probes is proposed in this paper. The proposed method can be used to accurately identify the reference ball center in the performance test of touch trigger probes.  相似文献   
74.
As a novel parallel hip joint simulator, the 3SPS+1PS bionic parallel test platform with 4 degrees of freedom including three rotations and one translation is proposed. SPS denotes the spherical-prismatic-spherical leg and PS denotes the prismatic-spherical leg where only the prismatic joint is actuated and hence underlined. By means of the unit quaternion method, the formulae for solving the inverse/forward displacement, the inverse/forward velocity and the inverse/forward acceleration kinematics are derived. Using the unit quaternion to represent the position and orientation of a moving platform, singularities caused by Euler angles can be avoided. Combining the topological structure characteristics of the 3SPS+1PS bionic parallel test platform and letting the three-dimensional (3-D) motion of a human hip joint as its output movement, the displacement trajectories of three active legs are constructed based on the inverse displacement kinematics. The forward kinematic tests whose data are recorded by a 3-D orientation capture system are carried out on the developed parallel hip joint simulator. Moreover, the results of the forward kinematic tests prove that the 3SPS+1PS bionic parallel test platform can approximately represent human hip joint motion and provide more reliable experimental data for hip joint prostheses in clinical application.  相似文献   
75.
《Ergonomics》2012,55(6):1012-1021
For decades, research to quantify the effects of firefighting activities and personal protective equipment on physiology and biomechanics has been conducted in a variety of testing environments. It is unknown if these different environments provide similar information and comparable responses. A novel Firefighting Activities Station, which simulates four common fireground tasks, is presented for use with an environmental chamber in a controlled laboratory setting. Nineteen firefighters completed three different exercise protocols following common research practices. Simulated firefighting activities conducted in an environmental chamber or live-fire structures elicited similar physiological responses (max heart rate: 190.1 vs 188.0 bpm, core temperature response: 0.047°C/min vs 0.043°C/min) and accelerometry counts. However, the response to a treadmill protocol commonly used in laboratory settings resulted in significantly lower heart rate (178.4 vs 188.0 bpm), core temperature response (0.037°C/min vs 0.043°C/min) and physical activity counts compared with firefighting activities in the burn building.

Practitioner Summary: We introduce a new approach for simulating realistic firefighting activities in a controlled laboratory environment for ergonomics assessment of fire service equipment and personnel. Physiological responses to this proposed protocol more closely replicate those from live-fire activities than a traditional treadmill protocol and are simple to replicate and standardise.  相似文献   
76.
In this paper we introduce and describe a new scheme for the numerical integration of smooth functions. The scheme is based on the modified Taylor expansion and is suitable for functions that exhibit near-sinusoidal or repetitive behaviour. We discuss the method and its rate of convergence, then implement it for the approximation of certain integrals. Examples include integrands involving Airy wave, Bessel, Gamma, and elliptic functions. The results, from the data in the tables, demonstrate that the method converges rapidly and approximates the integral as well as some well-known numerical integration methods used with sufficiently small step sizes.  相似文献   
77.
78.
为满足实验室单克隆抗体的制备研究,本实验特对实验室常用的制备单抗的模拟抗原(Ac-NK16-Ahx-3)进行ELISA间接法检测,进而建立一种高效的检测方法。通过对不同稀释度待测抗体的免疫吸附测定,检测出它的最终灵敏度为0.078mg/mL,最佳二抗稀释倍数为300倍,其最佳拟合曲线为y=-0.0732x+0.6875,R2=0.8619。并且,通过统计学方法进行统计分析,确定出各实验组的相关性及变异系数,从而排除实验中的操作误差,最终可确定最佳的实验条件,并保证实验的准确性。  相似文献   
79.
80.
The work presented in this paper focuses on improving coal loading performance of shear drum.Employing the similarity theory,we carried out a dimensional analysis of the correlation parameters which in...  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