全文获取类型
收费全文 | 5921篇 |
免费 | 114篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 69篇 |
综合类 | 6篇 |
化学工业 | 823篇 |
金属工艺 | 63篇 |
机械仪表 | 134篇 |
建筑科学 | 298篇 |
矿业工程 | 22篇 |
能源动力 | 161篇 |
轻工业 | 378篇 |
水利工程 | 39篇 |
石油天然气 | 33篇 |
无线电 | 470篇 |
一般工业技术 | 792篇 |
冶金工业 | 1992篇 |
原子能技术 | 40篇 |
自动化技术 | 724篇 |
出版年
2021年 | 46篇 |
2020年 | 39篇 |
2019年 | 56篇 |
2018年 | 53篇 |
2017年 | 54篇 |
2016年 | 72篇 |
2015年 | 52篇 |
2014年 | 86篇 |
2013年 | 303篇 |
2012年 | 173篇 |
2011年 | 238篇 |
2010年 | 207篇 |
2009年 | 184篇 |
2008年 | 226篇 |
2007年 | 216篇 |
2006年 | 223篇 |
2005年 | 180篇 |
2004年 | 145篇 |
2003年 | 154篇 |
2002年 | 133篇 |
2001年 | 103篇 |
2000年 | 95篇 |
1999年 | 118篇 |
1998年 | 285篇 |
1997年 | 193篇 |
1996年 | 167篇 |
1995年 | 137篇 |
1994年 | 119篇 |
1993年 | 130篇 |
1992年 | 97篇 |
1991年 | 54篇 |
1990年 | 84篇 |
1989年 | 84篇 |
1988年 | 96篇 |
1987年 | 83篇 |
1986年 | 83篇 |
1985年 | 95篇 |
1984年 | 85篇 |
1983年 | 87篇 |
1982年 | 66篇 |
1981年 | 65篇 |
1980年 | 69篇 |
1979年 | 65篇 |
1978年 | 57篇 |
1977年 | 61篇 |
1976年 | 84篇 |
1975年 | 71篇 |
1974年 | 57篇 |
1973年 | 50篇 |
1972年 | 32篇 |
排序方式: 共有6044条查询结果,搜索用时 0 毫秒
61.
Tae Y. Jung Hong Jang Jay H. Lee 《International Journal of Control, Automation and Systems》2015,13(2):410-418
Model predictive control (MPC)-based approach to fab-wide scheduling has been suggested to solve constraint-aware production optimization and in-process inventory level control simultaneously at each scheduling instance. However, application of this approach to real fab suffers from computational difficulties brought by the need to solve a huge optimization problem on-line as real fab scheduling problems are characterized by long cycle times, multiple product types, hundreds of machines/processing steps and re-entrant product flows. This study explores the use of an offset-blocking strategy combined with a modified recursive least square (RLS) estimation in the fab-wide scheduler, in order to alleviate the difficulty. The strategy is tested on a modified version of published case study called Intel Mini-Fab (IMF) problem. Despite its simplicity, the blocking strategy showed excellent performance in the face of realistic demand changes and plant/model mismatch. 相似文献
62.
Jay Bhatt 《New Review of Information Networking》2013,18(1):83-98
Last year, researchers and librarians at both Drexel University and the University of Maryland initiated similar collaborative projects in their respective institutions to contribute to the development of life-long learning skills among the select participants. One joint finding was the importance of linking advances in knowledge, not just as hypothetical learning that benefits an elite few, but rather for the advancement of our society as a whole. 相似文献
63.
Using electric actuation and detection of oscillations in microcantilevers for pressure measurements
Gayatri Keskar Bevan Elliott Jay Gaillard Malcolm J. Skove Apparao M. Rao 《Sensors and actuators. A, Physical》2008,147(1):203-209
Response characteristics of a microcantilever, such as resonant frequency, amplitude, phase and quality factor, can be used for absolute pressure measurements in the range of 10−4 to 103 Torr. To this end, it would be very convenient to have the resonance of the microcantilever actuated and detected electrostatically. Herein, we report the nonlinear dynamics of microcantilevers under varying pressure and different gases using the harmonic detection of resonance (HDR) technique [J. Gaillard, M.J. Skove, R. Ciocan, A.M. Rao, Electrical detection of oscillations in 340 microcantilevers and nanocantilevers, Rev. Sci. Instrum. 77 (2006) 073907]. The HDR technique exploits nonlinearities in the cantilever-counter electrode system to allow electrostatic actuation and detection of the responses of the microcantilever to the pressure and gas composition. In particular, the 2nd and 3rd harmonics of the measured charge on the cantilever are investigated. The microcantilever demonstrates a quality factor of 10,000 at 10−3 Torr, and a usable response in the range from 10−3 to 103 Torr. The use of different harmonics can enable us to adjust the range of pressures over which the sensor has an efficacious response, enhancing its sensitivity to a particular environment. The experimental results are in reasonable agreement with theoretical calculations, despite the nonlinearities involved. 相似文献
64.
Robert Jay Milewski Venu Govindaraju Anurag Bhardwaj 《International Journal on Document Analysis and Recognition》2009,11(4):203-218
A new paradigm, which models the relationships between handwriting and topic categories, in the context of medical forms,
is presented. The ultimate goals are: (1) a robust method which categorizes medical forms into specified categories, and (2)
the use of such information for practical applications such as an improved recognition of medical handwriting or retrieval
of medical forms as in a search engine. Medical forms have diverse, complex and large lexicons consisting of English, Medical
and Pharmacology corpus. Our technique shows that a few recognized characters, returned by handwriting recognition, can be
used to construct a linguistic model capable of representing a medical topic category. This allows (1) a reduced lexicon to
be constructed, thereby improving handwriting recognition performance, and (2) PCR (Pre-Hospital Care Report) forms to be
tagged with a topic category and subsequently searched by information retrieval systems. We present an improvement of over
7% in raw recognition rate and a mean average precision of 0.28 over a set of 1,175 queries on a data set of unconstrained
handwritten medical forms filled in emergency environments.
This work was supported by the National Science Foundation. 相似文献
65.
相信许多朋友都知道《成吉思汗》麒麟游戏的开山之作,故此该公司根舍得下本钱。不仅花费两年的时间,还投资上亿!付出便有回报,游戏压力封测后,很多媒体、玩家对这款以成吉思汗征服世界的历史, 相似文献
66.
The authors reassert the need for methodological changes in depression research appearing in the Journal of Personality and Social Psychology and other personality and social psychology journals. In this rejoinder the authors update their earlier literature review (H. Tennen, J. Hall, & G. Affleck; see record 1995-31710-001) and respond to the commentaries by P C. Kendall and E. C. Flannery-Schroeder (see record 1995-31700-001) and G. Weary, J. A. Edwards, and J. A. Jacobson (see record 1995-31713-001). The authors notice that G. Weary et al.'s own findings demonstrate the need to change how depression is measured and participants are assigned to experimental groups. The authors also challenge G. Weary et al.'s contention that structured interviews are limited because they require interviewer judgments, and they urge personality and social psychologists to learn more about these interviews. Finally, G. Weary et al.'s suspicion that depression research guidelines reflect professional parochialism is disputed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
67.
Histogenetically, the thymus is the primary lymphopoietic organ and provides an optimal microenvironment for the differentiation of T lymphocytes, independently of the influence of foreign antigens. Lymphocytes with diverse potential are produced in a protective microenvironment optimal for their maturation, whose dual cellular network is provided by endodermally derived RE cells and numerous ectomesenchymal cells derived from the neural crest. The full development of intrathymic hematopoiesis depends upon the successful completion of a series of well coordinated cellular interactions between widely divergent (in terms of origin) cells [epithelium (primitive pharynx); ectomesenchyrne (neural crest); and PHSCs (yolk sac, fetal liver)]. The cells of the thymic epithelial primordium do not proliferate in the absence of "inductive" interactions with the ectomesenchyme. Moreover, the nature of the mesenchyme determines the behavior of the thymic epithelial anlagen. The ectomesenchymal origin of chemotactic stem cell factor secretion, responsible for hemopoietic stem cell immigration, is a distinct possibility. The human thymus is a generalized hematopoietic tissue with between 7 to 9 weeks of ontogenesis. In human and dog fetuses various elements of mammalian hematopoiesis were identified intrathymically: B lymphocytes, plasma cells, erythropoietic and granulocytopoietic (neutrophils and eosinophils) cells, antigen presenting dendritic cells, and mast cells. Our light and ultrastructural (transmission and scanning), as well as immunocytochemical observations have established that during the embryonal and fetal period, the thymus is seeded by pluripotent, yolk sac derived PHSCs characterized by the following immunophenotype CD34+CD43+CD38-Lin-HLA-DR+CD69+. Stem cell c-kit tyrosine kinase (also referred to as mast cell growth factor, stem cell factor, or steel factor) in combination with autocrine and paracrine growth factors and cytokines (IL-3, IL-4, IL-5, IL-6, IL-7, G-CSF, etc.) stimulates myelopoiesis, including erythropoiesis, as well as lymphopoiesis. These hematopoietic growth factors are produced by activated lymphoblastic cells and stromal RE cells under the influence of immunoneuroendocrine regulation, supported by the finding that experimental or spontaneous, in vivo neural crest ablation during early mammalian ontogenesis always results in an abnormal development of the thymus, as well as the heart and great vessels, thyroid, and parathyroid glands. 相似文献
68.
69.
A unified picture is obtained of the Cooper pair-breaking data by Cu-site Zn and Ni in Nd2–z
Ce
z
CuO4, La2–SrCuO4, Bi2Sr2CaCu2O8, Bi1.8Pb0.2Sr2Ca2Cu3O10, YBa2Cu3O7, and YBa2Cu4O8. The data are generally inconsistent with spin-fluctuation d-wave pairing mechanisms of superconductivity and with all two-dimensional cuprate-plane models. The data are consistent with superconductivity in the charge reservoirs. 相似文献
70.
The charge-transfer hypothesis is shown to be inconsistent with data for YBa2Cu3Ox: (i) The two-step behavior ofT
c(x) (with jumps from zero to 60 K and then to 90 K) is not reflected as a similar, statistically significant two-step behavior in the bond-valence-sum charge of cuprate-plane Cu ions (as once believed), (ii) as a consequence of the law of conservation of charge, the derivatives of the layer charges with respect to oxygen contentx for both the Ba-O layers and the charge-reservoir Cu-O chains have the opposite signs to those predicted, and (iii) the charge-transfer observed for superconducting YBa2Cu3Ox is not sufficient to produce superconductivity, as demonstrated by insulating PrBa2Cu3Ox, which has virtually the same layer charges. 相似文献