全文获取类型
收费全文 | 1687篇 |
免费 | 138篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 10篇 |
综合类 | 2篇 |
化学工业 | 664篇 |
金属工艺 | 36篇 |
机械仪表 | 21篇 |
建筑科学 | 45篇 |
矿业工程 | 7篇 |
能源动力 | 38篇 |
轻工业 | 312篇 |
水利工程 | 9篇 |
石油天然气 | 9篇 |
无线电 | 70篇 |
一般工业技术 | 313篇 |
冶金工业 | 87篇 |
原子能技术 | 2篇 |
自动化技术 | 203篇 |
出版年
2024年 | 4篇 |
2023年 | 23篇 |
2022年 | 54篇 |
2021年 | 191篇 |
2020年 | 55篇 |
2019年 | 60篇 |
2018年 | 76篇 |
2017年 | 60篇 |
2016年 | 71篇 |
2015年 | 57篇 |
2014年 | 83篇 |
2013年 | 138篇 |
2012年 | 96篇 |
2011年 | 121篇 |
2010年 | 95篇 |
2009年 | 95篇 |
2008年 | 108篇 |
2007年 | 56篇 |
2006年 | 70篇 |
2005年 | 58篇 |
2004年 | 49篇 |
2003年 | 30篇 |
2002年 | 39篇 |
2001年 | 18篇 |
2000年 | 15篇 |
1999年 | 11篇 |
1998年 | 16篇 |
1997年 | 6篇 |
1996年 | 15篇 |
1995年 | 7篇 |
1994年 | 2篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1990年 | 2篇 |
1989年 | 5篇 |
1986年 | 5篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1964年 | 1篇 |
1911年 | 2篇 |
排序方式: 共有1828条查询结果,搜索用时 171 毫秒
101.
Dr. Veronika Papoušková Dr. Pavel Kadeřávek Olga Otrusinová Alžbeta Rabatinová Dr. Hana Šanderová Jiří Nováček Dr. Libor Krásný Prof. Vladimír Sklenář Dr. Lukáš Žídek 《Chembiochem : a European journal of chemical biology》2013,14(14):1772-1779
The partially disordered δ subunit of RNA polymerase was studied by various NMR techniques. The structure of the well‐folded N‐terminal domain was determined based on inter‐proton distances in NOESY spectra. The obtained structural model was compared to the previously determined structure of a truncated construct (lacking the C‐terminal domain). Only marginal differences were identified, thus indicating that the first structural model was not significantly compromised by the absence of the C‐terminal domain. Various 15N relaxation experiments were employed to describe the flexibility of both domains. The relaxation data revealed that the C‐terminal domain is more flexible, but its flexibility is not uniform. By using paramagnetic labels, transient contacts of the C‐terminal tail with the N‐terminal domain and with itself were identified. A propensity of the C‐terminal domain to form β‐type structures was obtained by chemical shift analysis. Comparison with the paramagnetic relaxation enhancement indicated a well‐balanced interplay of repulsive and attractive electrostatic interactions governing the conformational behavior of the C‐terminal domain. The results showed that the δ subunit consists of a well‐ordered N‐terminal domain and a flexible C‐terminal domain that exhibits a complex hierarchy of partial ordering. 相似文献
102.
Ahn Woo-Young; Rass Olga; Fridberg Daniel J.; Bishara Anthony J.; Forsyth Jennifer K.; Breier Alan; Busemeyer Jerome R.; Hetrick William P.; Bolbecker Amanda R.; O'Donnell Brian F. 《Canadian Metallurgical Quarterly》2011,120(4):911
Patients with bipolar disorder (BD) and schizophrenia (SZ) often show decision-making deficits in everyday circumstances. A failure to appropriately weigh immediate versus future consequences of choices may contribute to these deficits. We used the delay discounting task in individuals with BD or SZ to investigate their temporal decision making. Twenty-two individuals with BD, 21 individuals with SZ, and 30 healthy individuals completed the delay discounting task along with neuropsychological measures of working memory and cognitive function. Both BD and SZ groups discounted delayed rewards more steeply than did the healthy group even after controlling for current substance use, age, gender, and employment. Hierarchical multiple regression analyses showed that discounting rate was associated with both diagnostic group and working memory or intelligence scores. In each group, working memory or intelligence scores negatively correlated with discounting rate. The results suggest that (a) both BD and SZ groups value smaller, immediate rewards more than larger, delayed rewards compared with the healthy group and (b) working memory or intelligence is related to temporal decision making in individuals with BD or SZ as well as in healthy individuals. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
103.
Ward Ryan D.; Kellendonk Christoph; Simpson Eleanor H.; Lipatova Olga; Drew Michael R.; Fairhurst Stephen; Kandel Eric R.; Balsam Peter D. 《Canadian Metallurgical Quarterly》2009,123(4):720
Increased striatal dopamine D2 receptor activity is thought to contribute to the pathophysiology of schizophrenia. To model this condition in mice, Kellendonk et al. (2006) generated transgenic mice that selectively overexpress the D2 receptor in striatum (D2OE). Drew et al. (2007) reported that D2OE mice display deficits in interval timing and motivation. The present study further explored the impaired timing in D2OE mice. Experiment 1 assessed the role of motivation in producing timing deficits in the peak procedure and found that performance in D2OE mice was improved by increasing motivation. In addition, performance was impaired in control mice when motivation was decreased. In Experiment 2, we found that D2OE mice have no timing impairment when tested using the bisection task, a procedure in which the measure of timing performance is less influenced by motivation to respond. In Experiment 3, we also used the bisection task and found selective impairment in timing of long durations in D2OE mice. These results suggest that striatal D2 overexpression impairs timing by decreasing motivation and through its impact on working memory and/or sustained attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
104.
Olga Filippova Yu Xiao Michael Rehm Jason Ingham 《Building Research & Information》2018,46(7):711-724
The marked increase in the awareness of earthquake risk following the Canterbury earthquakes in New Zealand offered a unique opportunity to investigate the economic effect of disaster-mitigation regulations on the commercial building stock. A difference-in-differences (DD) framework was used to determine whether earthquake risk has been capitalized into the property prices of buildings constructed prior to 1976, as a response to the national policy requiring assessment and strengthening (or demolition) of the existing earthquake-prone building stock. A negative externality is found in the policy announcement on affected (pre-1970s) office and retail buildings which caused office buildings to suffer a 12.5% stigma discount. However, retail properties were less impacted suffering a 2.3% stigma loss. The value of the commercial building stock has been affected by the policy. These findings provide policy-makers with timely evidence as to the economic effects of New Zealand’s earthquake-prone buildings policy. Facing losses in property value and financial responsibility for retrofitting their assets, building owners will be looking for a workable set of regulatory and non-regulatory incentives to encourage disaster risk management and protect the built environment. 相似文献
105.
106.
One of main applications of interval computations is estimating errors of indirect measurements. A quantity y is measured indirectly if we measure some quantities xi related to y and then estimate y from the results
of these measurements as
by using a known relation f. Interval computations are used "to find the range of f(x1,...,xn) when xi are known to belong to intervals
," where i are guaranteed accuracies of direct measurements. It is known that the corresponding problem is intractable (NP-hard) even for polynomial functions f.In some real-life situations, we know the probabilities of different value of xi; usually, the errors xi -
are independent Gaussian random variables with 0 average and known standard deviations i. For such situations, we can formulate a similar probabilistic problem: "given i, compute the standard deviation of f(x1,...,xn) ." It is reasonably easy to show that this problem is feasible for polynomial functions f. So, for polynomial f, this probabilistic computation problem is easier than the interval computation problem.It is not too much easier: Indeed, polynomials can be described as functions obtained from xi by applying addition, subtraction, and multiplication. A natural expansion is to add division, thus getting rational functions. We prove that for rational functions, the probabilistic computational problem (described above) is NP-hard. 相似文献
107.
108.
This paper describes an efficient, accurate and simple implementation of an algorithm for generation of quadrilateral finite element meshes. An original algorithm by Talbert and Parkinson [J.A. Talbert, A. Parkinson, Development of an automatic two-dimensional finite element mesh generator using quadrilateral elements and Bezier curve boundary definition, Int. J. Numer. Meth. Eng., 29 (1990) 1551–1567], has been substantially redeveloped and modified and presented in greater detail. We cover several important issues omitted in publication mentioned and we will provide interested readers with fully documented source code of the program. 相似文献
109.
Juan M. C. Tascn A. M. Olga Olivn Luis G. Tejuca 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1986,36(3):136-143
Some aspects of the interactions of CO and NO with LaRhO3 have been studied. The reduction of this oxide with CO occurs where the contracting sphere model is of perovskite structure stable up to a concentration of anion vacancies of ca. 2e? per molecule. By reduction of LaRhO3 at 817 K, rhodium was obtained, highly dispersed on a matrix of La2O3. After a reduction-oxidation cycle at 871 K the particle size of the perovskite decreased drastically. The activation energy of the reduction (67 kJ mol?1) was significantly lower than that of other LaMO3 oxides of group-VIII metals. Coverages of CO(θCO) and NO(θNO) at room temperature were lower than 3%, θNO being substantially higher than θCO. The reversibly adsorbed fractions of CO and NO underwent a remarkable decrease after preadsorbing NO and CO, respectively. This competitive adsorption is assumed to be associated with the adsorption of CO and NO on metallic sites. NO preadsorption inhibited the total adsorption of CO more severely than the reverse, indicating that NO is bound more strongly than CO to the LaRhO3 surface. 相似文献
110.
During the last ten or fifteen years we have seen an increase in enrollment in undergraduate psychology courses that is far out of proportion to the general increase in overall university attendance. Psychology departments are overwhelmed with undergraduate students, and the numbers continue to increase each year. Since we are allocating so much of our time, energy, and resources to undergraduate teaching, it is important to determine what these students are being educated for. This note reports the results of an inquiry into the postgraduate occupations of the members of the first three graduating classes of the psychology major programme at McGill University. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献