全文获取类型
收费全文 | 495980篇 |
免费 | 6020篇 |
国内免费 | 1198篇 |
专业分类
电工技术 | 8605篇 |
综合类 | 426篇 |
化学工业 | 79596篇 |
金属工艺 | 19531篇 |
机械仪表 | 14722篇 |
建筑科学 | 11919篇 |
矿业工程 | 2977篇 |
能源动力 | 11233篇 |
轻工业 | 48338篇 |
水利工程 | 5359篇 |
石油天然气 | 10805篇 |
武器工业 | 46篇 |
无线电 | 51885篇 |
一般工业技术 | 94616篇 |
冶金工业 | 92046篇 |
原子能技术 | 11859篇 |
自动化技术 | 39235篇 |
出版年
2021年 | 4187篇 |
2019年 | 3944篇 |
2018年 | 6973篇 |
2017年 | 6876篇 |
2016年 | 7348篇 |
2015年 | 4732篇 |
2014年 | 7909篇 |
2013年 | 21576篇 |
2012年 | 12603篇 |
2011年 | 16695篇 |
2010年 | 13438篇 |
2009年 | 15109篇 |
2008年 | 15669篇 |
2007年 | 15591篇 |
2006年 | 13684篇 |
2005年 | 12433篇 |
2004年 | 11723篇 |
2003年 | 11301篇 |
2002年 | 11386篇 |
2001年 | 11037篇 |
2000年 | 10667篇 |
1999年 | 10682篇 |
1998年 | 25929篇 |
1997年 | 18852篇 |
1996年 | 14582篇 |
1995年 | 11043篇 |
1994年 | 10006篇 |
1993年 | 9745篇 |
1992年 | 7532篇 |
1991年 | 7222篇 |
1990年 | 7236篇 |
1989年 | 7152篇 |
1988年 | 6975篇 |
1987年 | 5989篇 |
1986年 | 6040篇 |
1985年 | 6973篇 |
1984年 | 6640篇 |
1983年 | 6032篇 |
1982年 | 5675篇 |
1981年 | 5876篇 |
1980年 | 5678篇 |
1979年 | 5497篇 |
1978年 | 5572篇 |
1977年 | 6368篇 |
1976年 | 8249篇 |
1975年 | 5029篇 |
1974年 | 4788篇 |
1973年 | 4921篇 |
1972年 | 4194篇 |
1971年 | 3875篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
We present the design of E-kernel, an embedding kernel on the Victor V256 message-passing partitionable multiprocessor, developed for the support of program mapping and network reconfiguration. E-kernel supports the embedding of a new network topology onto Victor's 2D mesh and also the embedding of a task graph onto the 2D mesh network or the reconfigured network. In the current implementation, the reconfigured network can be a line or an even-size ring, and the task graphs meshes or tori of a variety of dimensions and shapes or graphs with similar topologies. For application programs having these task graph topologies and that are designed according to the communication model of E-kernel, they can be run without any change on partitions connected by the 2D mesh, line, or ring. Further, E-kernel attempts the communication optimization of these programs on the different networks automatically, thus making both the network topology and the communication optimization attempt completely transparent to the application programs. Many of the embeddings used in E-kernel are optimal or asymptotically optimal (with respect to minimum dilation cost). The implementation of E-kernel translated some of the many theoretical results in graph embeddings into practical tools for program mapping and network reconfiguration in a parallel system. E-kernel is functional on Victor V256. Measurements of E-kernel's performance on V256 are also included 相似文献
82.
This research was supported under project No. 6.02.02/128-93 as part of the state scientific-technical program on future information
technologies and systems by the Ukrainian State Committee, of Science and Technology. 相似文献
83.
84.
85.
The study presents a hypothesis on how randomness could be simulated by human subjects. Three sources of deviation from randomness are predicted: (1) the preferred application of overlearned production schemata for producing sequences of digits, (2) a wrong concept of randomness, and (3) the impossibility to monitor for redundancies of higher- than those of first-order. Deviations of random generation of digits produced by healthy subjects, patients with chronic frontal lobe damage, and patients with Parkinson's disease from random sequences produced by a computer program can be explained by the differential influence of these factors. Whereas incorrect concepts of randomness and limits on monitoring capacity distinguished all sequences produced by humans from actual random sequences, persistence on a single production strategy distinguished brain-damaged patients from controls. Random generation of digits appears to be a theoretically transparent and clinically useful test of executive function. 相似文献
86.
F. Cioffi E. M. Cohen Richard Badick 《Drug development and industrial pharmacy》1993,19(14):1741-1746
Carstensen and Rhodes1 have suggested that when, in stability programs, assays cannot be performed immediately after the protocol-designated storage time, then freezing them until such a time when assays can be performed would be a reasonable manner to retain the protocol schedule. They caution, however, that such a procedure may not be valid for dissolution data. The article to follow deals with real-time data showing that such a process is feasible for Nalidixic Acid tablets (and presumably for other tablets as well), and that, furthermore, the dissolution pattern would seem to be “frozen” as well. 相似文献
87.
A. G. Strunina 《Journal of Engineering Physics and Thermophysics》1993,65(4):953-956
The process of combustion of homogeneous and heterogeneous nongasifying and slightly gasifying systems over the range of a number of parameters characterizing the reactive composition and the conditions for the arrangement of the combustion process is studied by using thermocouple and optical methods. The regions of the implementation of different combustion regimes, namely, steady, pulsating, multiple-point, and spin, are determined experimentally.Institute of Structural Macrokinetics, Russian Academy of Sciences, Chernogolovka. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 65, No. 4, pp. 407–411, October, 1993. 相似文献
88.
An extended logistic model with a varying asymptotic upper bound for long-range peak demand forecasting is described. The model has been applied to a typical fast growing system, the Saudi Consolidated Electric Company. The forecasts are compared with actual demands and with those obtained from classical forecasting methods. The model gave relatively accurate peak demand forecasts compared with other classical methods. The model with a single load observation is capable of producing several peak demand forecasts corresponding to different levels of maximum temperature and various levels of social activity. The forecasts produced by the model were also stable irrespective of the length of the ex-post simulation period 相似文献
89.
E. Smith 《Journal of Materials Science》1993,28(4):880-884
The criterion for crack growth instability in an elastic-softening material that is subjected to displacement control loading conditions is examined. A theoretical analysis of the model of a solid containing two symmetrically situated deep cracks and with tensile loading of the remaining ligament, defines the criterion for crack growth instability. The criterion is expressed in terms of the material's softening characteristics and the solid's geometrical parameters. The analysis covers the complete spectrum of material behaviour from the case where the softening zone is very small to the case where instability does not occur until the softening zone traverses the ligament between the crack tips. 相似文献
90.
Robben J.; der Schueren J.Van; Verhasselt P.; Aert R.; Volckaert G. 《Protein engineering, design & selection : PEDS》1995,8(2):159-165
The deletion of nine residues from the C-terminus of the bacterialchloramphenicol acetyltransferase (CAT) results in depositionof the mutant protein in cytoplasmic inclusion bodies and lossof chloramphenicol resistance in Escherichia coli. This foldingdefect is relieved by C-terminal fusion of the polypeptide withas few as two residues. Based on these observations, efficientpositive selection for the cloning of DNA fragments has beendemonstrated. The cloning vector encodes a C-terminally truncatedCAT protein. Restriction sites in front of the stop codon allowthe insertion of target DNA, resulting in the production ofproperly folded CAT fusion proteins and regained chloramphenicolresistance. The positive selection of recombinants is accomplishedby growth of transformants on chloramphenicol-containing agarplates. The method appears particularly convenient for the cloningof DNA fragments amplified by the PCR because minimal informationto restore CAT folding can be included in the primers. The cloningof random sequences shows that the folding defect can be relievedby fusion to a wide variety of peptides, providing great flexibilityto the positive selection system. This vector may also contributeto the determination of the role of the C-terminus in CAT folding. 相似文献