全文获取类型
收费全文 | 2677篇 |
免费 | 62篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 8篇 |
化学工业 | 213篇 |
金属工艺 | 6篇 |
机械仪表 | 12篇 |
建筑科学 | 32篇 |
矿业工程 | 4篇 |
能源动力 | 42篇 |
轻工业 | 191篇 |
水利工程 | 6篇 |
无线电 | 74篇 |
一般工业技术 | 161篇 |
冶金工业 | 1846篇 |
原子能技术 | 2篇 |
自动化技术 | 143篇 |
出版年
2022年 | 23篇 |
2021年 | 34篇 |
2020年 | 18篇 |
2019年 | 25篇 |
2018年 | 21篇 |
2017年 | 36篇 |
2016年 | 21篇 |
2015年 | 17篇 |
2014年 | 35篇 |
2013年 | 54篇 |
2012年 | 46篇 |
2011年 | 58篇 |
2010年 | 56篇 |
2009年 | 53篇 |
2008年 | 46篇 |
2007年 | 46篇 |
2006年 | 41篇 |
2005年 | 25篇 |
2004年 | 36篇 |
2003年 | 31篇 |
2002年 | 21篇 |
2001年 | 19篇 |
2000年 | 14篇 |
1999年 | 63篇 |
1998年 | 534篇 |
1997年 | 304篇 |
1996年 | 207篇 |
1995年 | 140篇 |
1994年 | 122篇 |
1993年 | 112篇 |
1992年 | 18篇 |
1991年 | 28篇 |
1990年 | 19篇 |
1989年 | 34篇 |
1988年 | 31篇 |
1987年 | 33篇 |
1986年 | 24篇 |
1985年 | 21篇 |
1984年 | 3篇 |
1983年 | 7篇 |
1982年 | 10篇 |
1981年 | 10篇 |
1980年 | 21篇 |
1978年 | 7篇 |
1977年 | 61篇 |
1976年 | 134篇 |
1975年 | 5篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1964年 | 2篇 |
排序方式: 共有2740条查询结果,搜索用时 15 毫秒
1.
This article addresses the computation of invariant control laws [A. Fradkov, I. Miroshnik, V. Nikiforov, Nonlinear and Adaptive Control of Complex Systems, Kluwer, 1999] for fed-batch fermenters represented by two standard models. It will be shown how to derive partial state feedbacks that, assuming ideal conditions and perfect model, keep the specific growth rate μ constant provided the initial conditions are adequate. The invariant control law is the closed loop version of the exponential feeding already suggested in several references as shown later. The paper presents an analysis of invariance and a study of global stability within the framework of partial stability. That is, stability with respect to some of the state variables. This enables us to treat the case with Haldane-like or non-monotonous kinetics. 相似文献
2.
3.
DH Kang CL Coe DO McCarthy NN Jarjour EA Kelly RR Rodriguez WW Busse 《Canadian Metallurgical Quarterly》1997,17(8):481-487
T cell cytokines play an important role in mediating airway inflammation in asthma. The predominance of a Th2 cytokine profile, particularly interleukin (IL)-4 and IL-5, is associated with the pathogenesis and course of asthma. The aim of this study was to test the hypothesis that a stressful life event alters the pattern of cytokine release in asthmatic individuals. Thirteen healthy controls and 21 asthmatic adolescents gave blood samples three times over a semester: midsemester, during the week of final examinations, and 2-3 weeks after examinations. Interferon-gamma (IFN-gamma), IL-2, IL-4, and IL-5 were measured from supernatants of cells stimulated with PHA/PMA for 24 h. Cells from asthmatic subjects released significantly more IL-5 during the examination and postexamination periods, whereas cells from healthy controls released significantly more IL-2 during the midsemester and examination periods, thereby indicating a bias for a Th2-like pattern in asthmatics and a Th1-like pattern in healthy controls. IL-4 and IL-5 production showed a marked decrease during and after examinations in healthy controls, whereas this decline was absent in asthmatics. The ratios of IFN-gamma:IL-4 and IFN-gamma:IL-5 also revealed significant changes in the profile of cytokine release across the semester. These results indicate differential cytokine responses in asthmatics that may become pronounced during periods of cellular activation. 相似文献
4.
R Jover J Llach JM Bordas A Mas JM Salmerón S Navarro J Terés 《Canadian Metallurgical Quarterly》1997,20(7):344-346
There are evidence indicating that endoscopic retrograde cholangiopancreatography with sphincterotomy (ERCP+S) reduces the rate of complications in patients with severe acute biliary pancreatitis (ABP). The aim of this study was to analyze our experience in the treatment of severe ABP with ERCP+S and compare the evolution of the patients treated early (3 days or less following admission) with those treated late (after the 3rd day). A retrospective review of the clinical histories of the 16 patients with severe ABP treated with ERCP+S over the last two years is presented, analyzing their clinical features on admission and evolution. Biliary stones or biliary sludge was observed in 11 cases (69%). Nine patients had undergone early, and 7 late, ERCP+S. The patients of the latter group presented a greater number of complications during evolution than the former group (43% vs 0%; p = 0.025). The mortality of the patients of the late ERCP+S was also greater although without statistical significance (28.6% vs 0%; p = 0.15). No complication secondary to ERCP+S was detected. These findings confirm the fact that ERCP+S performed early in severe ABP significantly reduces the number of complications and is associated with a lower mortality. 相似文献
5.
6.
7.
Cypriano G da Trindade Neto Ana LP Fernandes Ana IB Santos Waldenice A Morais Marcos VM Navarro Tereza NC Dantas Mrcia R Pereira Jos LC Fonseca 《Polymer International》2005,54(4):659-666
Complexation of chitosan in aqueous solutions by low molecular weight electrolytes is one of the simplest methods for the preparation of aqueous chitosan dispersions. In this work, the influence of storage time, sulfate concentration, method of preparation and surfactant content on some properties of the resultant chitosan dispersions (turbidity, viscosity and zeta potential) was analyzed. Turbidimetry was adequate to monitor the formation of particles, while viscometry was suitable to monitor changes in the dispersing phase. An analysis of the properties of these systems, mainly in terms of particle–particle and macromolecule–macromolecule interactions was carried out. Copyright © 2004 Society of Chemical Industry 相似文献
8.
J. L. Díez J. L. Navarro A. Sala 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2007,11(10):973-983
In this work, simple modifications on the cost index of particular local-model fuzzy clustering algorithms are proposed in
order to improve the readability of the resulting models. The final goal is simultaneously providing local linear models (reasonably
close to the plant’s Jacobian) and clustering in the input space so that desirable characteristics (regarding final model
accuracy, and convexity and smoothness of the cluster membership functions) are improved with respect to other proposals in
literature. Some examples illustrate the proposed approach. 相似文献
9.
An amplified primer extension assay has been developed for quantitatively mapping the sites of psoralen photoaddition to DNA. This assay was applied to a torsionally tuned Z-DNA-probe that was specifically designed for the primer extension assay. The torsionally tuned Z-DNA forming sequence, (CG)6TA(CG)2(TG)8, forms Z-DNA in vitro at negative superhelical density: sigma = -0.05. The internal 5'-TA dinucleotide was reactive to psoralen when it existed as B-DNA. Upon the formation of Z-DNA, the internal 5'-TA no longer photobound psoralen. The torsionally tuned sequence was synthesized as an EcoRI fragment such that, when Z-DNA formed, the central 5'-AATT of the EcoRI sites was part of the B-Z junctions. The 5'-AATT sequence was not reactive with psoralen when it existed as B-DNA. When the 5'-AATT sequence existed as a B-Z junction, one strand of each junction became hyperreactive to psoralen. The TT directly 5' to the B-DNA-Z-DNA junction photobound psoralen in a strand-specific fashion. Quantitation of the relative rate of psoralen photobinding to the internal 5'-TA and the 5'-AATT at the B-Z junctions provides relationships that are characteristic of the level of supercoiling in DNA. 相似文献
10.