全文获取类型
收费全文 | 55341篇 |
免费 | 5072篇 |
国内免费 | 3090篇 |
专业分类
电工技术 | 3722篇 |
技术理论 | 1篇 |
综合类 | 3592篇 |
化学工业 | 7093篇 |
金属工艺 | 3093篇 |
机械仪表 | 3167篇 |
建筑科学 | 3704篇 |
矿业工程 | 1393篇 |
能源动力 | 1400篇 |
轻工业 | 3611篇 |
水利工程 | 1181篇 |
石油天然气 | 2120篇 |
武器工业 | 507篇 |
无线电 | 6172篇 |
一般工业技术 | 5050篇 |
冶金工业 | 1708篇 |
原子能技术 | 844篇 |
自动化技术 | 15145篇 |
出版年
2024年 | 211篇 |
2023年 | 763篇 |
2022年 | 1535篇 |
2021年 | 2223篇 |
2020年 | 1598篇 |
2019年 | 1375篇 |
2018年 | 1368篇 |
2017年 | 1527篇 |
2016年 | 1438篇 |
2015年 | 2001篇 |
2014年 | 2759篇 |
2013年 | 2998篇 |
2012年 | 4192篇 |
2011年 | 5933篇 |
2010年 | 4501篇 |
2009年 | 4152篇 |
2008年 | 3646篇 |
2007年 | 3489篇 |
2006年 | 3195篇 |
2005年 | 2735篇 |
2004年 | 2165篇 |
2003年 | 2021篇 |
2002年 | 1845篇 |
2001年 | 1266篇 |
2000年 | 1010篇 |
1999年 | 863篇 |
1998年 | 518篇 |
1997年 | 461篇 |
1996年 | 357篇 |
1995年 | 276篇 |
1994年 | 240篇 |
1993年 | 175篇 |
1992年 | 146篇 |
1991年 | 107篇 |
1990年 | 107篇 |
1989年 | 81篇 |
1988年 | 64篇 |
1987年 | 26篇 |
1986年 | 27篇 |
1985年 | 14篇 |
1984年 | 15篇 |
1983年 | 5篇 |
1982年 | 10篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1979年 | 12篇 |
1978年 | 9篇 |
1977年 | 4篇 |
1959年 | 12篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 38 毫秒
91.
Dong Sun Author Vitae 《Automatica》2003,39(6):997-1005
A new control approach to position synchronization of multiple motion axes is developed, by incorporating cross-coupling technology into adaptive control architecture. The control strategy is to stabilize position tracking of each axis while synchronizing its motion with other axes’ motions so that differential position errors amongst axes converge to zero. The proposed adaptive controller and parameter estimator employ coupling control by feeding back position errors and differential position errors, and have been realized to guarantee asymptotic convergence to zero of both position and synchronization errors. Simulations conducted on a multi-axis motion control system demonstrate the effectiveness of the method. 相似文献
92.
93.
Nonlinear model predictive control with polytopic invariant sets 总被引:1,自引:0,他引:1
Ellipsoidal invariant sets have been widely used as target sets in model predictive control (MPC). These sets can be computed by constructing appropriate linear difference inclusions together with additional constraints to ensure that the ellipsoid lies within a given inclusion polytope. The choice of inclusion polytope has a significant effect on the size of the target ellipsoid, but the optimal inclusion polytope cannot in general be computed systematically. This paper shows that use of polytopic invariant sets overcomes this difficulty, allowing larger stabilizable sets without loss of performance. In the interests of online efficiency, consideration is focused on interpolation-based MPC. 相似文献
94.
Qing-Chang Zhong Author Vitae 《Automatica》2003,39(3):499-508
This paper generalizes the frequency-domain results on the delay-type Nehari problem in the stable case to the unstable case. The solvability condition of the delay-type Nehari problem is formulated in terms of the nonsingularity of three matrices. The optimal value γopt is the maximal γ∈(0,∞) such that one of the three matrices becomes singular. All sub-optimal compensators are parameterized in a transparent structure incorporating a modified Smith predictor. 相似文献
95.
Gilles Celeux Author VitaeFlorence ForbesAuthor Vitae Nathalie Peyrard Author Vitae 《Pattern recognition》2003,36(1):131-144
Image segmentation using Markov random fields involves parameter estimation in hidden Markov models for which the EM algorithm is widely used. In practice, difficulties arise due to the dependence structure in the models and approximations are required. Using ideas from the mean field approximation principle, we propose a class of EM-like algorithms in which the computation reduces to dealing with systems of independent variables. Within this class, the simulated field algorithm is a new stochastic algorithm which appears to be the most promising for its good performance and speed, on synthetic and real image experiments. 相似文献
96.
Determination of vitality from a non-invasive biomedical measurement for use in fingerprint scanners
Fingerprints are the oldest and most widely used biometrics for personal identification. Unfortunately, it is usually possible to deceive automatic fingerprint identification systems by presenting a well-duplicated synthetic or dismembered finger. This paper introduces one method to provide fingerprint vitality authentication in order to solve this problem. Detection of a perspiration pattern over the fingertip skin identifies the vitality of a fingerprint. Mapping the two-dimensional fingerprint images into one-dimensional signals, two ensembles of measures, namely static and dynamic measures, are derived for classification. Static patterns as well as temporal changes in dielectric mosaic structure of the skin, caused by perspiration, demonstrate themselves in these signals. Using these measures, this algorithm quantifies the sweating pattern and makes a final decision about vitality of the fingerprint by a neural network trained by examples. 相似文献
97.
本文利用模糊集理论,提出一种非确定环境的描述方法,并且针对机器人在该类环境中的避障轨迹规划,建立了相应的决策函数和规划策略,最后,给出在PC-386计算机上的仿真试验结果。 相似文献
98.
Previously, we showed that the N-terminal recognition domain (T1) of Kv1.3 was not required for assembly of functional channels [Tu et al. (1996) J. Biol. Chem. 271, 18904-18911]. Moreover, specific Kv1.3 peptide fragments including regions of the central core are able to inhibit expression of current produced from a channel lacking the T1 domain, Kv1.3(T1-). To elucidate the mechanism whereby Kv1.3 peptide fragments suppress Kv1.3(T1-) current, we have studied the ability of peptide fragments containing the transmembrane segments S1, S1-S2, or S1-S2-S3 to physically associate with the Kv1.3(T1-) polypeptide subunit in vitro in microsomal membranes. Using c-myc (9E10) epitope-labeled peptide fragments and anti-myc antibody as well as antisera to the Kv1.3 C-terminus, we now demonstrate specific association of these peptide fragments with Kv1.3(T1-). Association of peptide fragments with Kv1.3(T1-) was correlated with integration of both proteins into the membrane. Furthermore, the relative strength and kinetics of this association directly correlated with the ability of fragments to suppress Kv1.3(T1-) current. The rate-limiting step in the sequential synthesis, integration, and formation of a complex was the association of integrated polypeptides within the plane of the lipid bilayer. These results strongly suggest that the physical association of transmembrane segments provides the basis for suppression of K+ channel function by K+ channel peptide fragments in vivo. Moreover, the S1-S2-S3 peptide fragment potently suppressed full-length Kv1.3, thus implicating a role for the S1-S2-S3 region of Kv1.3 in the assembly of the Kv1.3 channel. We refer to these putative association sites as IMA (intramembrane association) sites. 相似文献
99.
该研究采用问卷法,通过对30种消费品的调查,分析了消费者对消费品说明中警示信息的阅读倾向性,消费者的危险感受、消费者安全使用商品的自信度、遵守警示信息的可能性、主观危险估计和客观危险性这几项因素之间的关系。结果表明:消费者的危险感受与阅读警示信息的倾向性、遵守警告的要求之间存在高度的一致性;且与自信度呈负相关,所以可以通过研究消费者的危险感受来研究警示信息的有效性;消费者的危险感受、主观危险估计常与商品的客观危险性不一致,所以必须采取一些措施来矫正消费者的危险感受,以确保警示信息发挥应有的安全保障作用 相似文献
100.
N-羟甲基丙烯酰胺的合成 总被引:6,自引:0,他引:6
对N-羟甲基丙烯酰胺(NAM)的合成工艺做了进一步的研究。结果表明:在丙烯酰胺:甲醛=1∶1.05(mol比),碱性催化剂存在下,70℃反应3h。转化率可达99%。产品质量稳定,反应液可不经分离直接用作交联剂,降低了生产成本。并提出用固含量法测定溶液中的NAM含量,简易可靠。 相似文献