全文获取类型
收费全文 | 184590篇 |
免费 | 9689篇 |
国内免费 | 5624篇 |
学科分类
工业技术 | 199903篇 |
出版年
2024年 | 247篇 |
2023年 | 1239篇 |
2022年 | 2027篇 |
2021年 | 3281篇 |
2020年 | 2590篇 |
2019年 | 2252篇 |
2018年 | 16622篇 |
2017年 | 15888篇 |
2016年 | 12365篇 |
2015年 | 4232篇 |
2014年 | 5103篇 |
2013年 | 6129篇 |
2012年 | 9874篇 |
2011年 | 16628篇 |
2010年 | 14907篇 |
2009年 | 12009篇 |
2008年 | 13151篇 |
2007年 | 13861篇 |
2006年 | 6402篇 |
2005年 | 6580篇 |
2004年 | 5315篇 |
2003年 | 4890篇 |
2002年 | 4757篇 |
2001年 | 3774篇 |
2000年 | 3016篇 |
1999年 | 2483篇 |
1998年 | 1756篇 |
1997年 | 1496篇 |
1996年 | 1418篇 |
1995年 | 1166篇 |
1994年 | 907篇 |
1993年 | 675篇 |
1992年 | 530篇 |
1991年 | 412篇 |
1990年 | 317篇 |
1989年 | 232篇 |
1988年 | 217篇 |
1987年 | 134篇 |
1986年 | 78篇 |
1985年 | 70篇 |
1984年 | 52篇 |
1983年 | 45篇 |
1982年 | 47篇 |
1968年 | 45篇 |
1966年 | 43篇 |
1965年 | 44篇 |
1959年 | 42篇 |
1958年 | 37篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Yachao Dong Christos T. Maravelias Norman F. Jerome 《Optimization and Engineering》2018,19(4):937-976
We study a maritime inventory routing problem, in which shipments between production and consumption nodes are carried out by a fleet of vessels. The vessels have specific capacities and can be chartered under different agreements. The inventory levels of all consumption nodes and some production nodes should be maintained within specified bounds; for the remaining production nodes, orders should be picked up within pre-defined time windows. We propose a discrete-time mixed-integer programming model. In the face of new information and uncertainty, this optimization model has to be re-solved, as the horizon is rolled forward. We discuss how to account for different sources of uncertainty. We present a rolling-horizon reoptimization framework that allows us to study different policies that impact the quality of the implemented solution, so we can identify the optimal set of policies. 相似文献
92.
User Modeling and User-Adapted Interaction - Personality plays a pivotal role at work. Many scholars have investigated the association between personality and language usage habits in the English... 相似文献
93.
Tian Xiaoying Peng Hui Luo Xuguang Nie Shiyuan Zhou Feng Peng Xiaoyan 《International Journal of Control, Automation and Systems》2020,18(4):897-910
International Journal of Control, Automation and Systems - There is a class of typical nonlinear industrial process, which can be characterized by a first-order inertia plus pure delay model in an... 相似文献
94.
Providing reliable group communication is an ever recurring topic in distributed settings. In mobile ad hoc networks, this problem is even more significant since all nodes act as peers, while it becomes more challenging due to highly dynamic and unpredictable topology changes. In order to overcome these difficulties, we deviate from the conventional point of view, i.e., we "fight fire with fire," by exploiting the nondeterministic nature of ad hoc networks. Inspired by the principles of gossip mechanisms and probabilistic quorum systems, we present in this paper PILOT (probabilistic lightweight group communication system) for ad hoc networks, a two-layer system consisting of a set of protocols for reliable multicasting and data sharing in mobile ad hoc networks. The performance of PILOT is predictable and controllable in terms of both reliability (fault tolerance) and efficiency (overhead). We present an analysis of PILOT's performance, which is used to fine-tune protocol parameters to obtain the desired trade off between reliability and efficiency. We confirm the predictability and tunability of PILOT through simulations with ns-2. 相似文献
95.
Gert Schubring 《NTM》2003,11(2):90-99
Enno Heeren Dirksen (1788–1850) was one of several mathematicians originating from Eastern Frisia at the end of the eighteenth
century to acquire prominence in neohumanist reformed Prussia. While striving—like so many of his contemporaries—for more
rigour in the foundations of calculus, his work is significant due to his unusual emphasis on the semiotic aspects of the
basic concepts. As a clear-sighted propagator of Cauchy's conceptual innovations in Germany, his achievements in improving
sign expressions of such concepts enabled him to clarify hitherto not differentiated multiple limit processes—although less
successfully in constructive concept formation itself.
The contribution is based on the analysis of Dirksen's published texts and on the numerous texts which remained drafts for
his projected voluminousOrganon der gesamten Analysis.
Menso Folkerts zum 60. Geburtstag gewidmet 相似文献
Menso Folkerts zum 60. Geburtstag gewidmet 相似文献
96.
Yang Aiying Wang Ziyu Zhang Zhaoyi Chen Zhangyuan Wu Deming 《电子科学学刊(英文版)》2003,20(6):461-466
A 10Gbit/s recirculating system is configured with Chirped Fiber Bragg Grating (CFBG) for the dispersion compensation. For the first time, the transmission distance in the loop reaches 1000km with bit error rate of 10-9. The effect of the group delay ripple of the fiber grating is also investigated in the recirculating systems, and it is shown that the transmission distance is limited to 4 cycles (4×167.1km ) in the loop with the power penalty fluctuation below 1.0dB. Thus the group delay ripple should be reduced to allow for the wavelength drift of±5GHz. At the end of this letter, the principles are given for designing long haul recirculating systems with dispersion compensation CFBG. 相似文献
97.
综述了氰酸钾的合成方法,并对各种方法进行了评价,其中液固相反应法具有原料易得,操作简便,产物纯度较高、易与溶剂分离、经济性好等特点,适用于工业化生产。 相似文献
98.
99.
100.