全文获取类型
收费全文 | 143291篇 |
免费 | 7342篇 |
国内免费 | 3371篇 |
专业分类
电工技术 | 5220篇 |
技术理论 | 6篇 |
综合类 | 6422篇 |
化学工业 | 20547篇 |
金属工艺 | 8385篇 |
机械仪表 | 6653篇 |
建筑科学 | 7431篇 |
矿业工程 | 2175篇 |
能源动力 | 2985篇 |
轻工业 | 7412篇 |
水利工程 | 2355篇 |
石油天然气 | 3594篇 |
武器工业 | 514篇 |
无线电 | 16687篇 |
一般工业技术 | 23610篇 |
冶金工业 | 5199篇 |
原子能技术 | 1095篇 |
自动化技术 | 33714篇 |
出版年
2024年 | 965篇 |
2023年 | 1355篇 |
2022年 | 1896篇 |
2021年 | 2727篇 |
2020年 | 2011篇 |
2019年 | 1605篇 |
2018年 | 15989篇 |
2017年 | 15151篇 |
2016年 | 11618篇 |
2015年 | 2980篇 |
2014年 | 3089篇 |
2013年 | 3714篇 |
2012年 | 6861篇 |
2011年 | 13327篇 |
2010年 | 11821篇 |
2009年 | 8834篇 |
2008年 | 10192篇 |
2007年 | 11047篇 |
2006年 | 3493篇 |
2005年 | 4036篇 |
2004年 | 3133篇 |
2003年 | 2968篇 |
2002年 | 2444篇 |
2001年 | 1793篇 |
2000年 | 1648篇 |
1999年 | 1641篇 |
1998年 | 1211篇 |
1997年 | 1058篇 |
1996年 | 1049篇 |
1995年 | 831篇 |
1994年 | 681篇 |
1993年 | 496篇 |
1992年 | 452篇 |
1991年 | 346篇 |
1990年 | 217篇 |
1989年 | 183篇 |
1988年 | 168篇 |
1987年 | 100篇 |
1986年 | 67篇 |
1985年 | 61篇 |
1984年 | 36篇 |
1968年 | 43篇 |
1966年 | 42篇 |
1965年 | 44篇 |
1959年 | 37篇 |
1958年 | 37篇 |
1957年 | 36篇 |
1956年 | 34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 0 毫秒
161.
Category Partition Method (CPM) is a general approach to specification-based program testing, where test frame reduction and
refinement are two important issues. Test frame reduction is necessary since too many test frames may be produced, and test
frame refinement is important since during CPM testing new information about test frame generation may be achieved and considered
incrementally. Besides the information provided by testers or users, implementation related knowledge offers alternative information
for reducing and refining CPM test frames. This paper explores the idea by proposing a call patterns semantics based test
frame updating method for Prolog programs, in which a call patterns analysis is used to collect information about the way
in which procedures are used in a program. The updated test frames will be represented as constraints. The effect of our test
frame updating is two-fold. On one hand, it removes “uncared” data from the original set of test frames; on the other hand,
it refines the test frames to which we should pay more attention. The first effect makes the input domain on which a procedure
must be tested a subset of the procedure’s input domain, and the latter makes testers stand more chance to find out the faults
that are more likely to show their presence in the use of the program under consideration. Our test frame updating method
preserves the effectiveness of CPM testing with respect to the detection of faults we care. The test case generation from
the updated set of test frames is also discussed. In order to show the applicability of our method an approximation call patterns
semantics is proposed, and the test frame updating on the semantics is illustrated by an example.
相似文献
Lingzhong ZhaoEmail: |
162.
The identification of part families and machine groups that form the cells is a major step in the development of a cellular
manufacturing system and, consequently, a large number of concepts, theories and algorithms have been proposed. One common
assumption for most of these cell formation algorithms is that the product mix remains stable over a period of time. In today’s
world, the market demand is being shaped by consumers resulting in a highly volatile market. This has given rise to a new
class of products characterized by low volume and high variety. To incorporate product mix changes into an existing cellular
manufacturing system many important issues have to be tackled. In this paper, a methodology to incorporate new parts and machines
into an existing cellular manufacturing system has been presented. The objective is to fit the new parts and machines into an existing cellular manufacturing system thereby increasing machine utilization and reducing
investment in new equipment. 相似文献
163.
This paper reports on recent results in a series of the work of the authors on the stability and nonlinear control for general
dynamical systems described by retarded functional differential and difference equations. Both internal and external stability
properties are studied. The corresponding Lyapunov and Razuminkhin characterizations for input-to-state and input-to-output
stabilities are proposed. Necessary and sufficient Lyapunov-like conditions are derived for robust nonlinear stabilization.
In particular, an explicit controller design procedure is developed for a new class of nonlinear time-delay systems. Lastly,
sufficient assumptions, including a small-gain condition, are presented for guaranteeing the input-to-output stability of
coupled systems comprised of retarded functional differential and difference equations. 相似文献
164.
High fidelity repeater false-target badly affects a radar system’s detecting, tracking, and data processing. It is an available approach of confronting false-target for radar that discriminates firstly and then eliminates. Whereas for the technique progress about the repeater false-target jam, it is more and more difficult to discriminate this jam in the time-domain, frequency-domain, or space-domain. The technique using polarization information to discriminate the target and false-target is discussed in th... 相似文献
165.
Zhixue Wu 《Structural and Multidisciplinary Optimization》2009,37(6):625-634
The goal of this work is to obtain optimal hole shape for minimum stress concentration in two-dimensional finite plates using
parameterized geometry models. The boundary shape for a hole is described by two families of smooth curves: one is a “generalized
circular” function with powers as two parameters; the other one is a “generalized elliptic” function
a and b are ellipse axes) with powers as two parameters and one of the ellipse axes as the third parameter. Special attention is
devoted to the practicability of parameterized equations and the corresponding optimal results under the condition with and
without the curvature radius constraint. A number of cases were examined to test the effectiveness of the parameterized equations.
The numerical examples show that extremely good results can be obtained under the conditions with and without curvature radius
constraint, as compared to the known solutions in the literature. The geometries of the optimized holes are presented in a
form of compact parametric functions, which are suitable for use and test by designers. It is anticipated that the implementation
of the suggested parameterized equations would lead to considerable improvements in optimizing hole shape with high quality. 相似文献
166.
We present two algorithms that are near optimal with respect to the number of inversions present in the input. One of the
algorithms is a variation of insertion sort, and the other is a variation of merge sort. The number of comparisons performed
by our algorithms, on an input sequence of length n that has I inversions, is at most . Moreover, both algorithms have implementations that run in time . All previously published algorithms require at least comparisons for some c > 1.
M. L. Fredman was supported in part by NSF grant CCR-9732689. 相似文献
167.
郑思孝 《核技术(英文版)》1994,(2)
ACOMPLEX-TYPEFOCUSSEDMAGNETRONFORSPUTTERING¥ZhengSixiao(郑思孝)(InstituteofNuclearScienceandTechnology,SichuanUniversity,Chengdu... 相似文献
168.
郑跃伟 《上海冶金高等专科学校学报》1995,(2)
由于水的选择性吸收特性,辐射换热中水份波长匹配一直是一个有分歧的问题。文章通过理论与计算论证了这个问题,得出的结论否定了波长匹配的重要性。 相似文献
169.
Wang Lin Wang Xin Li Tao Zheng Ruijuan Zhu Junlong Zhang Mingchuan 《Neural computing & applications》2023,35(11):8051-8063
Neural Computing and Applications - Adaptive (sub)gradient methods have received wide applications such as the training of deep networks. The square-root regret bounds are achieved in convex... 相似文献
170.
Zheng Jianbing Gao Ming Lim Ee-Peng Lo David Jin Cheqing Zhou Aoying 《Knowledge and Information Systems》2022,64(7):1967-1996
Knowledge and Information Systems - Network robustness measures how well network structure is strong and healthy when it is under attack, such as vertices joining and leaving. It has been widely... 相似文献