全文获取类型
收费全文 | 2391篇 |
免费 | 90篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 13篇 |
化学工业 | 479篇 |
金属工艺 | 34篇 |
机械仪表 | 38篇 |
建筑科学 | 101篇 |
矿业工程 | 3篇 |
能源动力 | 40篇 |
轻工业 | 297篇 |
水利工程 | 15篇 |
石油天然气 | 4篇 |
无线电 | 157篇 |
一般工业技术 | 336篇 |
冶金工业 | 721篇 |
原子能技术 | 9篇 |
自动化技术 | 238篇 |
出版年
2023年 | 18篇 |
2022年 | 51篇 |
2021年 | 86篇 |
2020年 | 43篇 |
2019年 | 45篇 |
2018年 | 50篇 |
2017年 | 50篇 |
2016年 | 45篇 |
2015年 | 51篇 |
2014年 | 89篇 |
2013年 | 139篇 |
2012年 | 107篇 |
2011年 | 113篇 |
2010年 | 84篇 |
2009年 | 94篇 |
2008年 | 96篇 |
2007年 | 82篇 |
2006年 | 71篇 |
2005年 | 72篇 |
2004年 | 59篇 |
2003年 | 41篇 |
2002年 | 67篇 |
2001年 | 54篇 |
2000年 | 44篇 |
1999年 | 45篇 |
1998年 | 48篇 |
1997年 | 43篇 |
1996年 | 45篇 |
1995年 | 36篇 |
1994年 | 44篇 |
1993年 | 47篇 |
1992年 | 47篇 |
1991年 | 12篇 |
1990年 | 39篇 |
1989年 | 38篇 |
1988年 | 36篇 |
1987年 | 32篇 |
1986年 | 24篇 |
1985年 | 33篇 |
1984年 | 32篇 |
1983年 | 21篇 |
1982年 | 17篇 |
1981年 | 17篇 |
1980年 | 15篇 |
1979年 | 27篇 |
1978年 | 16篇 |
1977年 | 12篇 |
1976年 | 16篇 |
1975年 | 21篇 |
1972年 | 13篇 |
排序方式: 共有2485条查询结果,搜索用时 0 毫秒
81.
Diana C Iza David Mu?oz-Rojas Quanxi Jia Brian Swartzentruber Judith L MacManus-Driscoll 《Nanoscale research letters》2012,7(1):655
With particular focus on bulk heterojunction solar cells incorporating ZnO nanorods, we study how different annealing environments (air or Zn environment) and temperatures impact on the photoluminescence response. Our work gives new insight into the complex defect landscape in ZnO, and it also shows how the different defect types can be manipulated. We have determined the emission wavelengths for the two main defects which make up the visible band, the oxygen vacancy emission wavelength at approximately 530 nm and the zinc vacancy emission wavelength at approximately 630 nm. The precise nature of the defect landscape in the bulk of the nanorods is found to be unimportant to photovoltaic cell performance although the surface structure is more critical. Annealing of the nanorods is optimum at 300°C as this is a sufficiently high temperature to decompose Zn(OH)2 formed at the surface of the nanorods during electrodeposition and sufficiently low to prevent ITO degradation. 相似文献
82.
This paper reports on impact behavior of concrete panels protected by Polypropylene and Zylon fabric, respectively. Concrete panels were cast with different thickness and subjected to impact by a steel projectile. The initial and residual velocities were measured experimentally and the energy absorbed by the different concrete panels with and without fabric was calculated. All concrete panels were able to absorb almost all the kinetic energy of the projectiles. For concrete panels protected by fabric scabbing of concrete from the back face was considerably reduced and the debris contained by the fabric. Upper and lower bounds are proposed for energy absorbed per unit thickness and penetration results are compared with the available empirical formulas. It is shown that current penetration equations do not accurately predict impact parameters for concrete protected by fabric. 相似文献
83.
Runoff of pharmaceuticals and personal care products following application of biosolids to an agricultural field 总被引:1,自引:0,他引:1
Topp E Monteiro SC Beck A Coelho BB Boxall AB Duenk PW Kleywegt S Lapen DR Payne M Sabourin L Li H Metcalfe CD 《The Science of the total environment》2008,396(1):52-59
Municipal biosolids are a source of nutrients for crop production. Beneficial Management Practices (BMPs) can be used to minimize the risk of contamination of adjacent water resources with chemical or microbial agents that are of public or environmental health concern. In this field study, we applied biosolids slurry at a commercial rate using either subsurface injection or broadcast application followed by incorporation. Precipitation was simulated at 1, 3, 7, 22, 36 and 266 days post-application on 2 m2 microplots to evaluate surface runoff of 9 model pharmaceuticals and personal care products (PPCPs), atenolol, carbamazepine, cotinine, gemfibrozil, naproxen, ibuprofen, acetaminophen, sulfamethoxazole and triclosan. In runoff from the injected plots, concentrations of the model PPCPs were generally below the limits of quantitation. In contrast, in the broadcast application treatment, the concentrations of atenolol, carbamazepine, cotinine, gemfibrozil, naproxen, sulfamethoxazole and triclosan on the day following application ranged from 70-1477 ng L− 1 in runoff and generally declined thereafter with first order kinetics. The total mass of PPCPs mobilized in surface runoff per m2 of the field ranged from 0.63 µg for atenolol to 21.1 µg for ibuprofen. For ibuprofen and acetaminophen, concentrations in runoff first decreased and then increased, suggesting that these drugs were initially chemically or physically sequestered in the biosolids slurry, and subsequently released in the soil. Carbamazepine and triclosan were detected at low concentrations in a runoff event 266 days after broadcast application. Overall, this study showed that injection of biosolids slurry below the soil surface could effectively eliminate surface runoff of PPCPs. 相似文献
84.
Ariana C. F. Santos Luís P. G. Monteiro Adriana C. C. Gomes Ftima Martel Teresa M. Santos Brbara J. M. Leite Ferreira 《International journal of molecular sciences》2022,23(5)
After the serendipitous discovery of cisplatin, a platinum-based drug with chemotherapeutic effects, an incredible amount of research in the area of coordination chemistry has been produced. Other transition metal compounds were studied, and several new relevant metallodrugs have been synthetized in the past few years. This review is focused on coordination compounds with first-row transition metals, namely, copper, cobalt, nickel or manganese, or with zinc, which have potential or effective pharmacological properties. It is known that metal complexes, once bound to organic drugs, can enhance the drugs’ biological activities, such as anticancer, antimicrobial or anti-inflammatory ones. NSAIDs are a class of compounds with anti-inflammatory properties used to treat pain or fever. NSAIDs’ properties can be strongly improved when included in complexes using their compositional N and O donor atoms, which facilitate their coordination to metal ions. This review focuses on the research on this topic and on the promising or effective results that complexes of first-row transition metals and NSAIDs can exhibit. 相似文献
85.
P.J.M. Monteiro A.P. Kirchheim S. Chae P. Fischer A.A. MacDowell E. Schaible H.R. Wenk 《Cement and Concrete Composites》2009,31(8):577-584
New and advanced methodologies have been developed to characterize the nano and microstructure of cement paste and concrete exposed to aggressive environments. High resolution full-field soft X-ray imaging in the water window is providing new insight on the nano scale of the cement hydration process, which leads to a nano-optimization of cement-based systems. Hard X-ray microtomography images of ice inside cement paste and cracking caused by the alkali–silica reaction (ASR) enables three-dimensional structural identification. The potential of neutron diffraction to determine reactive aggregates by measuring their residual strains and preferred orientation is studied. Results of experiments using these tools are shown on this paper. 相似文献
86.
87.
Objective: Individuals may desire to diet or restrain from eating certain foods while attempting to quit smoking out of concern for weight gain. However, previous research and clinical tobacco treatment guidelines suggest that concurrent dieting may undermine attempts to quit smoking. The current study applied the self-control strength model, which posits that self-regulation relies on a limited strength that is consumed with use, to test whether resisting tempting sweets would lead to a greater likelihood of subsequent smoking. Design: Participants were 101 cigarette smokers randomly assigned to resist eating either from a tempting plate of sweets or from a plate of less tempting vegetables. All participants were then given a 10-min recess. Main Outcome Measures: Whether participants smoked during the break, measured with a breath carbon monoxide sample, served as the primary dependent variable. Results: As predicted, participants who resisted sweets were more likely to smoke during the break (53.2%) than those who resisted vegetables (34.0%), χ2(1, N = 101) = 3.65 p 相似文献
88.
Joecila Santos da Silva Stéphane Calmant Frédérique Seyler Daniel Medeiros Moreira Daniel Oliveira Achiles Monteiro 《Water Resources Management》2014,28(3):587-603
The hydrological observation network in the Amazon basin is made of conventional rainfall and water level stations presently maintained by the Agência Nacional de Águas (ANA), the National Agency for Waters. The water level network has long been plagued by difficulties associated with spatial coverage, timely delivery and data errors. Satellite observations are important means for providing hydrologic data with acceptable spatial and temporal resolution, and radar altimeters embarked onboard successive satellites since the early 1970s collect measurements of water level over rivers in a well-defined geodetic reference frame and can be used to address some of these problems. Nowadays, satellite altimetry can be used to collect the time variations of the water levels over many rivers throughout the word, as long as the reach are several hundred meters wide. This ability is particularly interesting in ungauge basins but it can also be used as an independent source of information to cross-check existing gauge series. In the present study, we focus on examples from the Amazon basin where radar altimetry has been used to provide an independent dataset that can be used to support the management of hydrological observation networks by including new data together with conventional field data, 相似文献
89.
Elisa de Almeida Jackix Elisa Bernardes Monteiro Helena Fonseca Raposo Emerielle Cristine Vanzela Jaime Amaya‐Farfán 《Journal of food science》2013,78(12):H1929-H1934
Several studies have shown that fruits and vegetables contribute to protect against degenerative pathologies such as cardiovascular diseases, diabetes, and cancer, mainly due to the presence of dietary fiber (DF) and polyphenols. Taioba (Xanthosoma sagittifolium) is an edible aroid widely grown in many parts of Africa, America, and Asia. The tubers portions of taioba are widely consumed; however, the leafy portions are generally discarded, despite their high nutritive value. In this study, we have partly characterized the DF of lyophiized taioba leaf (LTL), and assessed the possible protective effects on biochemical parameters and on bile acid (BA) production in colon and cecum, when fed to healthy rats for 4 wk. Forty‐five Wistar rats were assigned to either of 5 groups: group 1 received AIN 93G diet (CG: Control); group 2 received AIN 93G containing 2.5% of cellulose + 2.5% inulin (CEIN_5%); group 3 received AIN 93G containing 2.5% of cellulose + 2.5% taioba fiber (CETA_5%); group 4 received AIN 93G containing 5% cellulose + 2.5% taioba fiber (CETA_7.5%); group 5 received AIN 93G containing 5% cellulose + 2.5% of inulin (CEIN_7.5%). LTL showed high contents of total fiber, predominantly comprising insoluble DF with glucose as the major monomer. Rats receiving LTL had increased fecal mass and fat excretion, and improved BA profiles by diminishing the proportion of secondary acids, thus suggesting that consumption of taioba leaf may have the property of lowering the risk of colon cancer. 相似文献
90.
Many people believe that the “mad genius” notion, which has been a favorite cultural fixture for centuries, is based on established scientific fact. Much of the evidence for the connection between great creativity and great pathology, particularly affective disorder, comes from the writings of psychiatrists Nancy Andreasen and Arnold K. Ludwig and psychologist Kay Redfield Jamison. For two decades, their studies and books have been widely referenced in both the popular and professional press without critique or comment and often without much detail, suggesting that few people have spent much time with the originals. This article examines their most influential works, encouraging readers to evaluate this evidence for themselves, because the author believes that many of their claims have had unfortunate implications for the perception of creativity and the credibility of psychological research in general. The author considers the inherent difficulties of generating any scientific findings in this area, and concludes by discussing the signs of a hopeful trend to celebrate, rather than pathologize, people with exceptional gifts. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献