全文获取类型
收费全文 | 5448篇 |
免费 | 175篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 66篇 |
综合类 | 13篇 |
化学工业 | 1002篇 |
金属工艺 | 155篇 |
机械仪表 | 103篇 |
建筑科学 | 211篇 |
矿业工程 | 35篇 |
能源动力 | 115篇 |
轻工业 | 429篇 |
水利工程 | 27篇 |
石油天然气 | 8篇 |
无线电 | 460篇 |
一般工业技术 | 1004篇 |
冶金工业 | 1257篇 |
原子能技术 | 54篇 |
自动化技术 | 692篇 |
出版年
2023年 | 37篇 |
2022年 | 59篇 |
2021年 | 122篇 |
2020年 | 84篇 |
2019年 | 106篇 |
2018年 | 106篇 |
2017年 | 95篇 |
2016年 | 116篇 |
2015年 | 92篇 |
2014年 | 121篇 |
2013年 | 280篇 |
2012年 | 199篇 |
2011年 | 282篇 |
2010年 | 209篇 |
2009年 | 192篇 |
2008年 | 213篇 |
2007年 | 204篇 |
2006年 | 182篇 |
2005年 | 147篇 |
2004年 | 122篇 |
2003年 | 135篇 |
2002年 | 130篇 |
2001年 | 111篇 |
2000年 | 90篇 |
1999年 | 114篇 |
1998年 | 340篇 |
1997年 | 212篇 |
1996年 | 188篇 |
1995年 | 124篇 |
1994年 | 101篇 |
1993年 | 104篇 |
1992年 | 62篇 |
1991年 | 51篇 |
1990年 | 52篇 |
1989年 | 68篇 |
1988年 | 52篇 |
1987年 | 50篇 |
1986年 | 42篇 |
1985年 | 31篇 |
1984年 | 36篇 |
1983年 | 35篇 |
1982年 | 28篇 |
1981年 | 27篇 |
1980年 | 26篇 |
1979年 | 32篇 |
1978年 | 40篇 |
1977年 | 39篇 |
1976年 | 85篇 |
1975年 | 32篇 |
1974年 | 22篇 |
排序方式: 共有5631条查询结果,搜索用时 15 毫秒
11.
We have used Path Integral Monte Carlo to study the surface melting of molecular hydrogen. Density profiles perpendicular and parallel to the bare H2 surface are computed showing the formation of a liquid adlayer at 6 K, less than half the bulk melting temperature of para-hydrogen, 13.8 K. To estimate the onset temperature and depth of H2 surface melting we determine the static structure factor within the individual H2-layers for wave vectors in the plane and find no crystalline order down to 3 K in a partially filled H2 adlayer at the free surface. We find quantum effects amplify the melting point depression at the free H2 surface compared to bulk by a factor of five over classical Lennard-Jones solids and find that the zero-point fluctuations of molecules at the surface are much enhanced over their bulk values. We see vacancy formation in the solid before melting. 相似文献
12.
Convergence of simultaneous perturbation stochastic approximation for nondifferentiable optimization 总被引:1,自引:0,他引:1
We consider simultaneous perturbation stochastic approximation for function minimization. The standard assumption for convergence is that the function be three times differentiable, although weaker assumptions have been used for special cases. However, all work that we are aware of at least requires differentiability. We relax the differentiability requirement and prove convergence using convex analysis. 相似文献
13.
T. S. Shamirzaev A. I. Toropov A. K. Bakarov K. S. Zhuravlev A. Yu. Kobitski H. P. Wagner D. R. T. Zahn 《Semiconductors》2006,40(5):527-533
The stationary and time-resolved polariton radiation in ultrahigh quality AIGaAs layers have been studied. It has been found
that elastic exciton-exciton collisions lead to the appearance of a low-energy line of polariton radiation. We show that the
rate of exciton-to-polariton transitions caused by elastic exciton-exciton collisions is determined not only by the density
of the excitonic gas, but also by its temperature; this is in accordance with existing theoretical predictions.
The text was submitted by the authors in English. 相似文献
14.
15.
Facilitatory priming effects due to similarity of orthographic form are obtained for high-N target words provided that they have low-frequency bodies and the body is shared between the prime and target (e.g., perd-HERD). Conversely, it is shown that low-N target words show priming regardless of the frequency of the body, provided that the prime and target do not share the same body (e.g., drice-DRIVE). If the body is shared, then priming occurs only for targets with low-frequency bodies. These results suggest that neighborhood density should be defined in terms of both individual letter units and subsyllabic units and that both types of density jointly determine priming. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
16.
17.
We evaluated the effect of repeated administration of OC125 F(ab')2 fragments on cancer antigen (CA) 125 determination in 210 serum samples from 30 patients. We found falsely high CA 125 concentrations in 142 (68%) samples, using a homologous CA 125 enzyme immunoassay (EIA) with OC125 antibodies. The Truquant OV2 method, which involves two other murine antibodies, and the IMx CA 125 method, which uses sheep antibodies as capture antibodies, resulted in only slightly increased (false-positive) values in some samples with exceptionally high CA 125 EIA values. We measured falsely low CA 125 values in 37 (18%) samples with the Truquant OV2 method. Interferences could be eliminated by removal of serum IgG. Our results suggest that interferences are to some extent caused by anti-idiotypic IgG induced by OC125 administration. Assays involving nonmurine anti-CA 125 antibodies as capture antibodies seem to be most suited for CA 125 determination after OC125 treatment, but in every case an apparent increase of CA 125 after OC125 infusion should be validated. 相似文献
18.
T Higashiguchi PO Hasselgren K Wagner JE Fischer 《Canadian Metallurgical Quarterly》1993,17(4):307-314
The purpose of this study was to determine the etiologic factors of denture stomatitis. Fifteen subjects with clinical evidence of localized simple denture stomatitis, fifteen subjects without clinical signs of denture stomatitis, and forty-five subjects with clinical evidence of generalized simple denture stomatitis were investigated clinically and mycologically. Subjects were evaluated according to age, sex, duration of denture usage, smoking habits, frequency of denture brushing, overnight denture wearing, pH level of saliva and degree of candidal colonization and candidal formation. Salivary samples and swabs were taken from the palate and the mucosal surfaces of the dentures investigated mycologically in order to identify the yeast colonies. Smears were taken from the palate and investigated in order to identify candidal formation. No statistically significant relationship was found between denture stomatitis and age, sex, duration of denture usage, frequency of denture brushing, overnight denture wearing or pH level of saliva. There was however, a statistically significant relationship between denture stomatitis and denture hygiene, smoking habits, candidal colonization and candidal formation. 相似文献
19.
20.
Marcus T. Schmitz Bashir M. Al-Hashimi Petru Eles 《Design Automation for Embedded Systems》2002,6(4):401-424
In this paper, we introduce the LOPOCOS (Low Power Co-synthesis) system, a prototype CAD tool for system level co-design. LOPOCOS targets the design of energy-efficient embedded systems implemented as heterogeneous distributed architectures. In particular, it is designed to solve the specific problems involved in architectures that include dynamic voltage scalable (DVS) processors. The aim of this paper is to demonstrate how LOPOCOS can support the system designer in identifying energy-efficient hardware/software implementations for the desired embedded systems. Hence, highlighting the necessary optimization steps during design space exploration for DVS enable architectures. The optimization steps carried out in LOPOCOS involve component allocation and task/communication mapping as well as scheduling and dynamic voltage scaling. LOPOCOS has the following key features, which contribute to this energy efficiency. During the voltage scaling valuable power profile information of task execution is taken into account, hence, the accuracy of the energy estimation is improved. A combined optimization for scheduling and communication mapping based on genetic algorithm, optimizes simultaneously execution order and communication mapping towards the utilization of the DVS processors and timing behaviour. Furthermore, a separation of task and communication mapping allows a more effective implementation of both task and communication mapping optimizationsteps. Extensive experiments are conducted to demonstrate the efficiency of LOPOCOS. We report up to 38% higher energy reductions compared to previous co-synthesis techniques for DVS systems. The investigations include a real-life example of an optical flow detection algorithm. 相似文献