全文获取类型
收费全文 | 51646篇 |
免费 | 5259篇 |
国内免费 | 2732篇 |
专业分类
电工技术 | 3491篇 |
技术理论 | 6篇 |
综合类 | 3974篇 |
化学工业 | 8535篇 |
金属工艺 | 2772篇 |
机械仪表 | 3316篇 |
建筑科学 | 4355篇 |
矿业工程 | 1553篇 |
能源动力 | 1716篇 |
轻工业 | 3874篇 |
水利工程 | 1067篇 |
石油天然气 | 2440篇 |
武器工业 | 543篇 |
无线电 | 6084篇 |
一般工业技术 | 5930篇 |
冶金工业 | 2119篇 |
原子能技术 | 617篇 |
自动化技术 | 7245篇 |
出版年
2024年 | 224篇 |
2023年 | 961篇 |
2022年 | 1786篇 |
2021年 | 2483篇 |
2020年 | 1795篇 |
2019年 | 1511篇 |
2018年 | 1655篇 |
2017年 | 1797篇 |
2016年 | 1598篇 |
2015年 | 2241篇 |
2014年 | 2736篇 |
2013年 | 3237篇 |
2012年 | 3636篇 |
2011年 | 3679篇 |
2010年 | 3505篇 |
2009年 | 3335篇 |
2008年 | 3206篇 |
2007年 | 2815篇 |
2006年 | 2804篇 |
2005年 | 2216篇 |
2004年 | 1595篇 |
2003年 | 1332篇 |
2002年 | 1432篇 |
2001年 | 1254篇 |
2000年 | 1112篇 |
1999年 | 1128篇 |
1998年 | 837篇 |
1997年 | 714篇 |
1996年 | 672篇 |
1995年 | 508篇 |
1994年 | 458篇 |
1993年 | 313篇 |
1992年 | 276篇 |
1991年 | 193篇 |
1990年 | 145篇 |
1989年 | 131篇 |
1988年 | 81篇 |
1987年 | 55篇 |
1986年 | 42篇 |
1985年 | 29篇 |
1984年 | 21篇 |
1983年 | 16篇 |
1982年 | 18篇 |
1981年 | 12篇 |
1980年 | 17篇 |
1979年 | 7篇 |
1974年 | 2篇 |
1970年 | 2篇 |
1959年 | 3篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
ZHU Liye FANG Yuan ZHANG Weidong 《机械工程学报(英文版)》2008,21(1):91-93
According to a type of normal nonlinear system, an indirect adaptive fuzzy (IAF) controller has been applied to those systems where no accurate mathematical models of the systems under control are available. To satisfy with system performance, an indirect accelerated adaptive fuzzy (IAAF) controller is proposed, and its general form is presented. The general form IAAF controller ensures necessary control criteria and system's global stability using Lyapunov Theorem. It has been proved that the close-loop system error converges to a small neighborhood of equilibrium point. The optimal IAAF controller is derived to guarantee the process's shortest settling time. Simulation results indicate the IAAF controller make the system more stable, accurate, and fast. 相似文献
93.
The effects of key parameters on the preparation and regeneration of protoplast from the β-carotene-producing fungus Blakeslea trispora were discussed in this paper, including the combination of various enzymes, mycelial age, digesting time and temperature,
pH value, osmotic stabilizers, pretreatment, culture medium and culture method. Under the condition of mixed enzymes in osmotic
stabilizer (0.6 M NaCl) combined with 2% lysozyme, 3% cellulase and 3% snailase, the highest protoplast yield, as high as
7.48×106 protoplasts/mL, was obtained when mycelial age was 60 h at pH 5.0–6.0 with digesting for 14–16 h at 28 °C. After
purification of the obtained protoplasts, they were regenerated in PDA regenerative medium using bilayer plate culture method.
To validate the usability of the protoplasts, a novel plasmid with green fluorescent protein (GFP) was used in transformation
for easy visual observation. The results showed that the protoplasts prepared by the optimized method were active and applicable
in further gene manipulation experiments.
This work was presented at 13
th
YABEC symposium held at Seoul, Korea, October 20–22, 2007. 相似文献
94.
Wei Feng Jianping Wen Xiaoqiang Jia Qing Yuan Yan Sun Cuiyun Liu 《American Institute of Chemical Engineers》2006,52(8):2864-2875
A coupled three-dimensional (3-D) model, combining hydrodynamics with biochemical reactions, was developed to simulate the local transient flow patterns and the dynamic behaviors of cell growth and phenol biodegradation by yeast Candida tropicalis in the bubble-column bioreactor, using the computational fluid dynamic (CFD) method. In order to validate this proposed model effectively, the validation of the local hydrodynamic characteristics of the gas-mineral salt solution (gas-liquid) two-phase system, with the phenol concentration of 1200 mg/L, and with the absence of cells, was performed in a square-sectioned bubble column bioreactor using the LDA system and conductivity probe. Furthermore, the validation of phenol biodegradation behaviors by yeast Candida tropicalis at different initial concentrations of phenol and cell was also carried out in the above bubble-column bioreactor. The results indicated that the model simulations had a satisfying agreement with the experimental data. Finally, the local instantaneous flow and phenol biodegradation features including gas holdup, gas velocity, liquid velocity, cell concentration and phenol concentration inside the bioreactor were successfully predicted in different-scale bubble columns by the proposed model. © 2006 American Institute of Chemical Engineers AIChE J, 2006 相似文献
95.
针对碳酸盐岩气藏部分气井生产效能低的状况,决定在长庆气田下古生界尝试开展加砂压裂重复改造试验,以期提高低产、低效气井的产量,延长气田稳产期。通过潜心研究、精细设计及现场质检监控,优选了4口老井进行加砂压裂重复改造现场试验。从试验结果来看,虽然只有1口井取得明显的改造效果,但4口井加砂压裂施工都是成功的,说明对碳酸盐岩气藏实施加砂压裂是可以实现的,但在选井思路和压裂工艺方面还有待探索和研究。 相似文献
96.
A model for preventive maintenance operations and forecasting 总被引:2,自引:1,他引:1
Equipment costs constitute the greatest majority of overall costs for semiconductor manufacturing. Therefore, maintaining
high equipment availability has been regarded as one of the major goals in the industry. The ability to forecast correctly
equipment preventive maintenance (PM) timing requirements not only can help optimizing equipment uptime but also minimizing
negative impacts on manufacturing production efficiency. This research used grey theory and evaluation diagnosis to construct
a PM forecasting model for prediction of PM timing of various machines. The results showed significant improvements of PM
timing predictions compared to the existing method based on experience and an alternative method proposed by Li and Chang
(Semiconductor Manufacturing Technology Workshop 2002: 10–11, pp. 275–277) for the same fab cases.
Received: June 2005 / Accepted: December 2005 相似文献
97.
Average consensus in networks of dynamic agents with switching topologies and multiple time-varying delays 总被引:5,自引:0,他引:5
In this paper, we discuss average consensus problem in undirected networks of dynamic agents with fixed and switching topologies as well as multiple time-varying communication delays. By employing a linear matrix inequality method, we prove that all the nodes in the network achieve average consensus asymptotically for appropriate communication delays if the network topology is connected. Particularly, several feasible linear matrix inequalities are established to determine the maximal allowable upper bound of time-varying communication delays. Numerical examples are given to demonstrate the effectiveness and the sharpness of the theoretical results. 相似文献
98.
通过对铰孔孔径增大,误差大产生原因的工艺探讨、分析,提出了有效、切实可行的避免措施,通过灵活应用,提高了产品质量。 相似文献
99.
100.
An innovative method for modelling biological processes under anaerobic conditions is presented and discussed. The method is based on titrimetric and off-gas measurements. Titrimetric data is recorded as the addition rate of hydroxyl ions or protons that is required to maintain pH in a bioreactor at a constant level. An off-gas analysis arrangement measures, among other things, the transfer rate of carbon dioxide. The integration of these signals results in a continuous signal which is solely related to the biological reactions. When coupled with a mathematical model of the biological reactions, the signal allows a detailed characterisation of these reactions, which would otherwise be difficult to achieve. Two applications of the method to the enhanced biological phosphorus removal processes are presented and discussed to demonstrate the principle and effectiveness of the method. 相似文献