全文获取类型
收费全文 | 3420篇 |
免费 | 165篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 39篇 |
综合类 | 1篇 |
化学工业 | 759篇 |
金属工艺 | 60篇 |
机械仪表 | 60篇 |
建筑科学 | 172篇 |
矿业工程 | 6篇 |
能源动力 | 107篇 |
轻工业 | 386篇 |
水利工程 | 29篇 |
石油天然气 | 15篇 |
无线电 | 242篇 |
一般工业技术 | 474篇 |
冶金工业 | 695篇 |
原子能技术 | 16篇 |
自动化技术 | 530篇 |
出版年
2023年 | 16篇 |
2022年 | 24篇 |
2021年 | 47篇 |
2020年 | 37篇 |
2019年 | 46篇 |
2018年 | 64篇 |
2017年 | 67篇 |
2016年 | 67篇 |
2015年 | 91篇 |
2014年 | 107篇 |
2013年 | 215篇 |
2012年 | 149篇 |
2011年 | 223篇 |
2010年 | 157篇 |
2009年 | 162篇 |
2008年 | 179篇 |
2007年 | 148篇 |
2006年 | 172篇 |
2005年 | 137篇 |
2004年 | 131篇 |
2003年 | 110篇 |
2002年 | 103篇 |
2001年 | 60篇 |
2000年 | 51篇 |
1999年 | 78篇 |
1998年 | 167篇 |
1997年 | 124篇 |
1996年 | 99篇 |
1995年 | 58篇 |
1994年 | 52篇 |
1993年 | 59篇 |
1992年 | 42篇 |
1991年 | 35篇 |
1990年 | 24篇 |
1989年 | 26篇 |
1988年 | 16篇 |
1987年 | 17篇 |
1986年 | 13篇 |
1985年 | 25篇 |
1984年 | 23篇 |
1983年 | 10篇 |
1982年 | 23篇 |
1981年 | 20篇 |
1980年 | 11篇 |
1979年 | 14篇 |
1978年 | 8篇 |
1977年 | 12篇 |
1976年 | 24篇 |
1975年 | 8篇 |
1970年 | 8篇 |
排序方式: 共有3591条查询结果,搜索用时 15 毫秒
21.
BACKGROUND: Arteriovenous malformations (AVMs) are an abnormal communication between arterial and venous structures. Pelvic AVMs have been infrequently described in the literature and represent an uncommon cause of a palpable pelvic mass. CASE: A case of pelvic AVM with ureteral obstruction occurred. The location and radiologic appearance of the AVM suggested a complex adnexal mass. During exploration and resection of the mass, significant bleeding was encountered. The diagnosis of AVM was made only retrospectively, with histologic examination of the specimen. CONCLUSION: AVMs are an uncommon and unique cause of pelvic pathology. Preoperative diagnosis will alert the surgeon as to the technically difficult resection that may be encountered and to the massive bleeding that can be associated with their removal. 相似文献
22.
23.
Efforts to correlate molecular characteristics with microstructural dimensions in microphase-separated diblock and triblock copolymers have been very successful, resulting in relationships that can be utilized to design materials with a specific microstructure and, consequently, with particular thermomechanical properties. However, similar efforts in the arena of multiblock copolymers have not been nearly as extensive, despite the increasing interest and diversity of this class of materials. In the present work, energy-filtered electron microscopy (EFEM) and small-angle neutron scattering (SANS) are used in a complementary fashion to probe the phase behavior of a series of three polysiloxaneimide (PSI) multiblock copolymers with different molecular architectures. Despite their relatively short segment lengths, all three materials exhibit signs of microphase separation at ambient temperature. SANS data are obtained from chemically unaltered materials and are subsequently interpreted with the Teubner-Strey model for microemulsions. Resultant microstructural dimensions are in good agreement with those measured from EFEM micrographs. Additional insight into the intramolecular sequencing of each copolymer is obtained from scaling relationships. 相似文献
24.
Traditionally, companies used to view themselves as separate entities and did not devote efforts to collaborate with other echelons of the extended enterprise. This even happened at multi-site companies owning different plants that belonged to the same supply chain. However, manufacturing facilities of the same supply chain should intensively share information and coordinate planning and scheduling tasks in order to get a globally optimized solution. This paper discusses some specific characteristics of the planning and scheduling problem in the extended enterprise including an analysis of a case study, and reviews the available state-of-the-art research studies in this field. Most studies suggest that integrated approaches can have a significant impact on the system performance, in terms of lower production costs, and less inventory levels. The paper provides some conclusions and suggestions of future works. 相似文献
25.
BE Gilbert C Knight FG Alvarez C Waldrep JR Rodarte V Knight WL Eschenbacher 《Canadian Metallurgical Quarterly》1997,156(6):1789-1793
Cyclosporine A (CsA) in liposomes of dilauroylphosphatidylcholine (DLPC), containing 118 micrograms of CsA/L of aerosol with a particle size of 1.6 to 1.7 micron diameter, was inhaled by 10 nonsmoking, normal volunteers each for 45 min. Aerosol was administered through an Aerotech II nebulizer (CIS-US, Inc., Bedford, MA) mouthpiece. Eight of the 10 volunteers had tracheal irritation and intermittent coughing following exposure. FEV1 and FVC values were mildly reduced, but returned to normal in 1 h. Blood chemical and hematologic values were unchanged at any time point after as opposed to before inhalation. Nine of the 10 volunteers later inhaled DLPC only, administered through the nebulizer mouthpiece. There was no change in FEV1 or FVC values, and there was no coughing or tracheal irritation. Subsequently, five of the volunteers who had previously had respiratory reactions inhaled CsA-DLPC liposome aerosol for 45-min, but through a mouth-only face mask. There was no tracheal irritation, coughing, or changes in spirometric measures. Blood concentrations of CsA at 15 min after the 45-min inhalation with a face mask averaged 83 +/- 42 ng/ml (mean +/- SD). At 24 h after treatment, CsA was undetectable in blood of the initial 10 volunteers. These studies indicate that CsA-DLPC liposome aerosol can be safely explored as a treatment for patients with moderately severe asthma. 相似文献
26.
V. J. Cid A. M. Alvarez A. I. Santos C. Nombela M. Sanchez 《Yeast (Chichester, England)》1994,10(6):747-756
Yeast exo-1,3-β-glucanases are secretable proteins whose function is basically trophic and may also be involved in cell wall glucan hydrolytic processes. Since fluorescein di(β-D -glucopyranoside) is a fluorogenic substrate detectable and quantifiable by flow cytometry, it was used for testing the ability of the EXG1 gene product of Saccharomyces cerevisiae and its homologous gene in Candida albicans to function as reporter genes. These open reading frames were coupled to different promoters in multicopy plasmids, and exoglucanase activity quantified at flow cytometry. Exoglucanases were found to be useful tools for the study of promoter regions in S. cerevisiae. This technique has the advantage over other reporter gene systems—such as β-galactosidase fusions—that it does not require permeabilization of yeast cells and therefore it allows the recovery of viable cells—by sorting—after flow cytometry analysis. 相似文献
27.
Gerosa G. Gary S. Dietz C. Dac Pham Hoover K. Alvarez J. Sanchez H. Ippolito P. Tai Ngo Litch S. Eno J. Golab J. Vanderschaaf N. Kahle J. 《Solid-State Circuits, IEEE Journal of》1994,29(12):1440-1454
A 28 mW/MHz at 80 MHz structured-custom RISC microprocessor design is described. This 32-b implementation of the PowerPC architecture is fabricated in a 3.3 V, 0.5 μm, 4-level metal CMOS technology, resulting in 1.6 million transistors in a 7.4 mm by 11.5 mm chip size. Dual 8-kilobyte instruction and data caches coupled to a high performance 32/64-b system bus and separate execution units (float, integer, loadstore, and system units) result in peak instruction rates of three instructions per clock cycle. Low-power design techniques are used throughout the entire design, including dynamically powered down execution units. Typical power dissipation is kept under 2.2 W at 80 MHz. Three distinct levels of software-programmable, static, low-power operation-for system power management are offered, resulting in standby power dissipation from 2 mW to 350 mW. CPU to bus clock ratios of 1×, 2×, 3×, and 4× are implemented to allow control of system power while maintaining processor performance. As a result, workstation level performance is packed into a low-power, low-cost design ideal for notebooks and desktop computers 相似文献
28.
Jos A.D. Muoz Antn Alvarez Jorge Ancheyta Miguel A. Rodríguez Gustavo Marroquín 《Catalysis Today》2005,109(1-4):214-218
The present paper focuses on the study of process alternatives for heat integration of a heavy crude oil hydrotreatment plant. Experimental information obtained from a pilot scale, kinetics and reactor modeling tools, and a commercial process simulator were employed to develop mass and energy balances. Four study cases, which employ a combination of quenching and heat exchangers, were identified and evaluated. The results indicated that the case with two quenches with hydrogen and three heat exchangers is the best process heat integration (PHI) option from an energetic point of view. 相似文献
29.
Tim T. Y. Wong D. O. McInnis Mohsen M. Ramadan Jon I. Nishimoto 《Journal of chemical ecology》1991,17(12):2481-2487
Laboratory-reared and wild adults of the melon fly,Dacus cucurbitae Coquillett, were tested for response to cue-lure at various ages. Virgin laboratory (4, 6, 8, 10, 12, and 14 days old) and wild (10, 12, 14, 16, 18, 20, and 22 days old) flies were released into outdoor field cages and trapped from 0800 until 1600 hr. Response of males to cue-lure increased with age and corresponded with sexual maturity for each strain. Females of both strains were relatively nonresponsive to cue-lure. Failure to eradicate in past male annihilation programs againstD. cucurbitae may be explained in part by the fact that only older males, which may have already mated with gravid females, respond to cue-lure. 相似文献
30.
F. R. Perioto M. E. T. Alvarez W. A. Araujo M. R. Wolf‐Maciel R. Maciel Filho 《应用聚合物科学杂志》2008,110(6):3544-3551
A new calculation procedure for free‐volume parameters is considered in this work by using viscosity prediction methods and the Levenberg‐Marquardt calculation scheme. All parameters used in the Vrentas–Duda free‐volume theory can be estimated from pure component properties. The prediction results are compared with experimental data for some polymer/solvent systems. The diffusion coefficient calculated by Vrentas–Duda theory can be used in the modeling of membrane separation processes. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献