全文获取类型
收费全文 | 1151篇 |
免费 | 61篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 10篇 |
综合类 | 4篇 |
化学工业 | 298篇 |
金属工艺 | 23篇 |
机械仪表 | 14篇 |
建筑科学 | 71篇 |
矿业工程 | 4篇 |
能源动力 | 20篇 |
轻工业 | 90篇 |
水利工程 | 6篇 |
无线电 | 83篇 |
一般工业技术 | 228篇 |
冶金工业 | 88篇 |
原子能技术 | 8篇 |
自动化技术 | 271篇 |
出版年
2023年 | 17篇 |
2022年 | 31篇 |
2021年 | 46篇 |
2020年 | 23篇 |
2019年 | 31篇 |
2018年 | 29篇 |
2017年 | 27篇 |
2016年 | 30篇 |
2015年 | 32篇 |
2014年 | 66篇 |
2013年 | 69篇 |
2012年 | 93篇 |
2011年 | 105篇 |
2010年 | 62篇 |
2009年 | 65篇 |
2008年 | 85篇 |
2007年 | 72篇 |
2006年 | 49篇 |
2005年 | 47篇 |
2004年 | 38篇 |
2003年 | 33篇 |
2002年 | 27篇 |
2001年 | 16篇 |
2000年 | 19篇 |
1999年 | 12篇 |
1998年 | 15篇 |
1997年 | 12篇 |
1996年 | 11篇 |
1995年 | 13篇 |
1994年 | 7篇 |
1993年 | 7篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有1218条查询结果,搜索用时 234 毫秒
131.
132.
In the paper, the development of final energy consumption in Lithuania, on the basis of realistic economic scenarios, is investigated. The main parameters influencing the energy consumption are the gross national product (GNP) and the wholesale price of energy. Owing to the uncertainties in former socialist economies, these parameters are described as ‘fuzzy sets.’ The theory of fuzzy sets is used to study the influences that the prices of preceding periods have on the actual final energy consumption, with a quasidynamic model. In so far as this mechanism cannot be ascertained for Lithuania, experiences with other former centrally planned economies, which have already turned into a kind of market economy, are applied to give realistic projections for the transitory period. The underlying scenarios for the GNP and price developments are taken from official Lithuanian projections. The results of the fuzzy quasidynamic model are compared with the official final energy demand projections, to provide policy advice for a proper restructuring of the energy system. 相似文献
133.
The selective oxidation of hydrocarbons is an important value-enhancing chemical transformation in particular with respect to fine chemicals and pharmaceuticals production. Enzymatic oxidations operate under mild reaction conditions and produce little if any waste. However, its industrial use is still limited mainly due to their high cost and the low space time yields. In the present work, chloroperoxiase from Calariomyces fumago immobilized on the mesoporous molecular sieve SBA-15 was applied for the oxidation of indole to 2-oxoindole using hydrogen peroxide or tert.-butyl hydroperoxide as oxidants. The performance of the immobilized enzyme was found to be superior to native chloroperoxidase with respect to maximum conversion and pH range applicable. However, immobilized CPO is still sensitive to high concentrations of hydrogen peroxide. The use of tert.-buty hydroperoxide is found to avoid this problem, but the reaction rate is significantly reduced. 相似文献
134.
Robinson Michael D.; Wilkowski Benjamin M.; Kirkeby Ben S.; Meier Brian P. 《Canadian Metallurgical Quarterly》2006,135(1):78
Clinical views of neuroticism-linked distress often make reference to the perseverative sorts of mental processes that reinforce such experiences. The goal of the present 7 studies, involving 488 undergraduate participants, was to directly examine such perseverative processes. Individual differences in response perseveration were operationalized in terms of choice reaction time difficulties switching (vs. repeating) responses across consecutive trials. Response perseveration interacted with neuroticism in predicting negative emotion, dissatisfaction with life, and displays of negative emotion (Studies 1-4). Specifically, neuroticism-outcome relations were quite a bit stronger at high levels of perseveration. Additional studies (Studies 5-7) provided support for the convergent and discriminant validity of response perseveration. Overall, the results highlight the manner in which response perseveration reinforces experiences of negative emotion. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
135.
136.
Schorr Gudrun; Ulbricht Sabina; Schmidt Carsten O.; Baumeister Sebastian E.; Rüge Jeannette; Schumann Anja; Rumpf Hans-Jürgen; John Ulrich; Meyer Christian 《Canadian Metallurgical Quarterly》2008,76(5):840
The authors examined the subtype structure of smokers classified in the precontemplation stage of change within the transtheoretical model. From a general practice-based sample of 1,499 daily smoking patients from Germany (participation rate 80%), they used a subgroup of 929 smokers who were classified in the precontemplation stage and applied latent class analysis, using the pros and cons of nonsmoking and smoking cessation self-efficacy as the defining variables. Cross-sectional validation of the emerging classes was based on smoking behavior and processes of change variables. For longitudinal validation, generalized estimation equation analyses were used on motivational and abstinence criteria from 6-, 12-, 18-, and 24-month follow-ups. A 4-class model best represented the data. Three subtypes (labeled progressive, immotive, and disengaged pessimistic) were similar to clusters identified in U.S. studies. The 4th (disengaged optimistic), by contrast, was reminiscent of a type that had previously only emerged in a Dutch study. Cross-sectional and longitudinal validation results confirmed the distinctiveness and predictive power of the classes. The findings highlight the importance of tailoring interventions for smoking behavior change to the needs of different subgroups of precontemplating smokers. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
137.
138.
Carsten W. Scherer 《Systems & Control Letters》1995,25(5):327-335
For arbitrary equally sized square complex matrices A and Q (Q Hermitian), the paper provides a complete algebraic test for verifying the existence of a Hermitian solution X of the nonstrict Lyapunov inequality A*X + XA + Q 0. If existing, we exhibit how to construct a solution. Our approach involves the validation problem for the linear matrix inequality Σj=1k (Aj*XjBj + Bj*Xj*Aj) + Q> 0 in Xj, for which we provide an algebraic solvability test and a construct solutions if the kernels of Aj or, dually, those of Bj form an isotonic sequence. 相似文献
139.
A theoretical model based on the theory of complex potentials and dislocation formalism is used to simulate fatigue crack growth in a transformation-toughened ceramic. The effective stress-intensity factor is calculated during crack growth, because it is believed to determine the crack-growth rate similar to the Paris-type growth law. For certain combinations of transformation strength and load, the effective stress-intensity factor decreases to zero, indicating crack arrest. A detailed parametric study of this phenomenon reveals that the applied load and minimum transformation strength parameter necessary to cause crack arrest are linearly related, independent of initial crack length. This suggests that a threshold stress similar to the endurance limit in the conventional stress/life (S/N) approach should be used instead of the threshold stress-intensity factor in the design of transformation-toughened ceramics against fatigue. 相似文献
140.
Mayer A Taguchi T Linnenbrink A Hofmann C Luzhetskyy A Bechthold A 《Chembiochem : a European journal of chemical biology》2005,6(12):2312-2315
LanV is involved in the biosynthesis of landomycin A. The exact function of this enzyme was elucidated with combinatorial biosynthesis by using Streptomyces fradiae mutants that produce urdamycin A. After expression of lanV in S. fradiae DeltaurdM, which is a mutant that accumulates rabelomycin, urdamycinon B and urdamycin B were found to be produced by the strain. This result indicates that LanV is involved in the 6-ketoreduction of the angucycline core, which preceeds a 5,6-dehydration reaction. 9-C-D-Olivosyltetrangulol was also produced by this strain; this demonstrates that LanV catalyses the aromatization of ring A of the angucycline structure. Coexpression of lanV and lanGT2 in S. fradiae AO, a mutant that lacks all four urdamycin glycosyltransferases, resulted in the production of tetrangulol and the glycoside landomycin H, both of which have an aromatic ring A. As glycosylated angucyclines were not observed after expression of lanGT2 in the absence of lanV, we conclude that LanGT2 needs an aromatized ring A for substrate recognition. 相似文献