全文获取类型
收费全文 | 36188篇 |
免费 | 1446篇 |
国内免费 | 63篇 |
专业分类
电工技术 | 371篇 |
综合类 | 29篇 |
化学工业 | 7237篇 |
金属工艺 | 725篇 |
机械仪表 | 738篇 |
建筑科学 | 1963篇 |
矿业工程 | 114篇 |
能源动力 | 1054篇 |
轻工业 | 2883篇 |
水利工程 | 430篇 |
石油天然气 | 117篇 |
武器工业 | 5篇 |
无线电 | 2475篇 |
一般工业技术 | 6116篇 |
冶金工业 | 6598篇 |
原子能技术 | 268篇 |
自动化技术 | 6574篇 |
出版年
2023年 | 214篇 |
2022年 | 440篇 |
2021年 | 684篇 |
2020年 | 463篇 |
2019年 | 617篇 |
2018年 | 781篇 |
2017年 | 694篇 |
2016年 | 833篇 |
2015年 | 757篇 |
2014年 | 1040篇 |
2013年 | 2372篇 |
2012年 | 1680篇 |
2011年 | 2092篇 |
2010年 | 1652篇 |
2009年 | 1547篇 |
2008年 | 1800篇 |
2007年 | 1774篇 |
2006年 | 1591篇 |
2005年 | 1439篇 |
2004年 | 1174篇 |
2003年 | 1122篇 |
2002年 | 1051篇 |
2001年 | 702篇 |
2000年 | 549篇 |
1999年 | 595篇 |
1998年 | 583篇 |
1997年 | 574篇 |
1996年 | 549篇 |
1995年 | 572篇 |
1994年 | 525篇 |
1993年 | 510篇 |
1992年 | 500篇 |
1991年 | 288篇 |
1990年 | 418篇 |
1989年 | 389篇 |
1988年 | 319篇 |
1987年 | 355篇 |
1986年 | 310篇 |
1985年 | 418篇 |
1984年 | 416篇 |
1983年 | 318篇 |
1982年 | 295篇 |
1981年 | 281篇 |
1980年 | 269篇 |
1979年 | 270篇 |
1978年 | 247篇 |
1977年 | 225篇 |
1976年 | 206篇 |
1975年 | 194篇 |
1974年 | 173篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
121.
122.
123.
Non-redundant data clustering 总被引:6,自引:6,他引:0
Data clustering is a popular approach for automatically finding classes, concepts, or groups of patterns. In practice, this
discovery process should avoid redundancies with existing knowledge about class structures or groupings, and reveal novel,
previously unknown aspects of the data. In order to deal with this problem, we present an extension of the information bottleneck
framework, called coordinated conditional information bottleneck, which takes negative relevance information into account by maximizing a conditional mutual information score subject to
constraints. Algorithmically, one can apply an alternating optimization scheme that can be used in conjunction with different
types of numeric and non-numeric attributes. We discuss extensions of the technique to the tasks of semi-supervised classification
and enumeration of successive non-redundant clusterings. We present experimental results for applications in text mining and
computer vision. 相似文献
124.
The local chemistry and structure of α-iron/molybdenum nitride heterophase interfaces is studied on a subnanometer scale by atom-probe field-ion microscopy (APFIM),
three-dimensional atom-probe microscopy (3DAPM) and both conventional transmission electron microscopy (CTEM) and highresolution
electron microscopy (HREM). Molybdenum nitride precipitates are generated by annealing Fe-2 at. pct Mo-X, where X=0.4 at.
pct Sb or 0.5 at. pct Sn, at 550 °C or 600 °C, in an ammonia/hydrogen mixture. Internal nitridation at 550 °C produces thin,
coherent platelet-shaped molybdenum nitride precipitates. Nitridation at 600 °C generates a much coarser structure with semicoherent
thick plate-shaped and spheroidal precipitates in addition to the thin-platelet structure. The APFIM and 3DAPM analyses of
the heterophase interfaces show substantial segregation of the solute species Sn and Sb only at the coarse precipitates, with
Gibbsian interfacial excesses of up to 7±3 nm−2, whereas the broad faces of the thin platelets have no detectable segregation. The TEM and HREM analyses show that the coarse
precipitates are semicoherent, whereas the thin platelets are either coherent or have much fewer misfit dislocations than
geometrically necessary. This demonstrates that Sn and Sb segregation is related to the presence of misfit dislocations at
the interfaces of the coarse precipitates.
This article is based on a presentation made at the symposium entitled “The Mechanisms of the Massive Transformation,” a part
of the Fall 2000 TMS Meeting held October 16–19, 2000, in St. Louis, Missouri, under the auspices of the ASM Phase Transformations
Committee. 相似文献
125.
Dicyanate Semi-Interpenetrating Polymer Networks (semi IPNs) are made by dissolving a thermoplastic in crosslinking dicyanates and then curing the resulting mixture. The semi IPNs produced are strong, with tensile strengths of 10,000 to 12,000 psi, and flexible, with elongations to break of 10 to 17 percent. Dicyanate semi IPNs also have good thermal stability and the softening temperatures of the IPNs are significantly, higher than those of the corresponding thermoplastics. 相似文献
126.
127.
Howard Kenneth I.; Krause Merton S.; Orlinsky David E. 《Canadian Metallurgical Quarterly》1986,54(1):106
Presents an analysis of the attrition dilemma in psychotherapy research and reviews the methods used to compensate for data loss. It is argued that attrition is not ultimately a problem of bias but a problem of lack of information. A reformulation is offered that integrates single-case studies with traditional group comparison methodology in an attempt to find optimal causal relations of treatments to outcomes. (10 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
128.
Jon David 《Computers & Security》2002,21(8):696
The flow of information, within organizations, between networks, and from single users to other individuals and networks, is commonly at rates that only a few years ago were dreams. Earlier methods for the detection and prevention of malicious activities are anywhere from inefficient to unworkable with transmissions at the giga speeds that are prevalent today. This writing sets forth the problems and threats associated with these new high speed transmissions, and presents methodologies and systems for treating them. 相似文献
129.
130.
One hypothesis for the transcontinental and intra-Great Lakes basin transfer of round gobies (Neogobius melanostomus) has been that round gobies were pumped into the ballast water of ships. During June 2005 in Lake Erie, we obtained evidence of a vertical migration of round goby larvae, when we collected 167 round goby larvae in surface ichthyoplankton net tows at night and zero during day. These results complemented similar findings from the Muskegon River estuary of Lake Michigan during 2003 and 2004, documenting diel vertical migration for the first time in larval round gobies. We suggest vertical migration behavior may have allowed larval round gobies to be transported to and within the Great Lakes via ballast water and dispersed in the Great Lakes via advection of 6.5–8.5-mm long larvae at the surface. Based on our results, if ballast water was only taken on near the surface during daylight hours from May through September when larval round gobies were present, it would have mitigated the spread of round gobies throughout the Great Lakes. 相似文献