全文获取类型
收费全文 | 14001篇 |
免费 | 342篇 |
国内免费 | 22篇 |
专业分类
电工技术 | 192篇 |
综合类 | 12篇 |
化学工业 | 3063篇 |
金属工艺 | 231篇 |
机械仪表 | 300篇 |
建筑科学 | 654篇 |
矿业工程 | 100篇 |
能源动力 | 380篇 |
轻工业 | 976篇 |
水利工程 | 135篇 |
石油天然气 | 163篇 |
武器工业 | 1篇 |
无线电 | 854篇 |
一般工业技术 | 2052篇 |
冶金工业 | 3393篇 |
原子能技术 | 142篇 |
自动化技术 | 1717篇 |
出版年
2022年 | 116篇 |
2021年 | 170篇 |
2020年 | 144篇 |
2019年 | 160篇 |
2018年 | 179篇 |
2017年 | 181篇 |
2016年 | 209篇 |
2015年 | 166篇 |
2014年 | 228篇 |
2013年 | 819篇 |
2012年 | 456篇 |
2011年 | 629篇 |
2010年 | 406篇 |
2009年 | 446篇 |
2008年 | 570篇 |
2007年 | 552篇 |
2006年 | 547篇 |
2005年 | 452篇 |
2004年 | 365篇 |
2003年 | 360篇 |
2002年 | 380篇 |
2001年 | 239篇 |
2000年 | 239篇 |
1999年 | 252篇 |
1998年 | 237篇 |
1997年 | 247篇 |
1996年 | 246篇 |
1995年 | 249篇 |
1994年 | 254篇 |
1993年 | 296篇 |
1992年 | 251篇 |
1991年 | 187篇 |
1990年 | 203篇 |
1989年 | 221篇 |
1988年 | 175篇 |
1987年 | 220篇 |
1986年 | 205篇 |
1985年 | 249篇 |
1984年 | 231篇 |
1983年 | 210篇 |
1982年 | 185篇 |
1981年 | 195篇 |
1980年 | 169篇 |
1979年 | 185篇 |
1978年 | 184篇 |
1977年 | 142篇 |
1976年 | 151篇 |
1975年 | 175篇 |
1974年 | 135篇 |
1973年 | 135篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
A finite-difference numerical method of solution for the unsteady, incompressible Navier-Stokes equations using primitive variables is presented. The rate form of the equation of state is used for the calculation of pressure. This form of the equation of state is well-suited for use with the unsteady form of the conservation equations (mass, momentum and energy). An implicit algorithm is used for the time integration for greater numerical stability. This method is used to solve a known benchmark problem in steady-state natural convection as a test of steady-state accuracy. The results of the simulation are compared to the benchmark. 相似文献
92.
Motility related protein 1 (MRP1/CD9) expression in colon cancer 总被引:1,自引:0,他引:1
M Mori K Mimori T Shiraishi M Haraguchi H Ueo GF Barnard T Akiyoshi 《Canadian Metallurgical Quarterly》1998,4(6):1507-1510
STUDY OBJECTIVES: To examine the incidence and clinical significance of prolonged air leak (PAL) in patients undergoing radical upper lobectomy and to determine potential risk factors for PAL in this group of patients. DESIGN: Retrospective review of a prospective database. SETTING: Experience of one thoracic surgeon at a tertiary care cancer center. PATIENTS: One hundred consecutive patients undergoing right upper lobectomy and mediastinal lymph node dissection for non-small cell lung cancer over an 11-year period. MEASUREMENTS: PAL was defined as an air leak lasting >7 days. Preoperative, intraoperative, and postoperative clinical data were collected and analyzed to determine the factors associated with PAL. RESULTS: PAL was the most prevalent postoperative complication, comprising 25.5% of all complications seen, and lasting an average of 12.1+/-5.3 days. In 21 of the 26 patients with PAL, this complication was the only morbidity identified. There was no statistically significant difference in patient age, gender, preoperative FEV1 and diffusion of carbon monoxide, exposure to neoadjuvant chemotherapy, status of pulmonary fissures, or pathologic stage between the PAL group vs the remaining 74 patients without this complication. A significantly greater proportion of patients with PAL had FEV1/FVC ratio < or =50% (6/26 vs 5/74; p=0.02). Patients with PAL had significantly longer median length of hospital stay (11 vs 7 days; p=0.0001). Moreover, PAL was the single most common reason for an extended length of hospitalization (21/58, 36% of all causes). CONCLUSION: PAL is an alarmingly common postoperative complication and is the most frequent cause of an extended length of hospital stay in patients undergoing radical upper lobectomy. Severe obstructive pulmonary disease predisposes patients to the development of this complication. 相似文献
93.
Parallel parsing is currently receiving attention but there is little discussion about the adaptation of sequential error handling techniques to these parallel algorithms. We describe a noncorrecting error handler implemented with a parallel LR substring parser. The parser used is a parallel version of Cormack's LR substring parser. The applicability of noncorrecting error handling for parallel parsing is discussed. The error information provided for a standard set of 118 erroneous Pascal programs is analysed. The programs are run on the sequential LR substring parser. 相似文献
94.
Monroe William S. Skidmore Frank M. Odaibo David G. Tanik Murat M. 《Neural computing & applications》2021,33(11):6027-6038
Neural Computing and Applications - In the medical imaging domain, nonlinear warping has enabled pixel-by-pixel mapping of one image dataset to a reference dataset. This co-registration of data... 相似文献
95.
Anil Kumar William R. Leo Lawrence Green Gene L. Woodruff 《Journal of Fusion Energy》1989,8(1-2):107-126
The neutron spectra transmitted across a fission-suppressed hybrid blanket and its components, driven by a low intensity 14 MeV Haefely neutron generator, were measured with a 2×2 NE213 detector at LOTUS facility. These experiments have been analyzed with 2D and 3D codes DOT3.5 and MCNP, respectively. The spectral integrals between 15 to 1 MeV show good agreement among the 2D, the 3D, and the NE213 for 15 cm lead, 18 cm beryllium, and 25 cm graphite slabs. However, there are large discrepancies for 6.2 cm stainless steel and 15 cm lithium carbonate slabs. The assemblies involving two or more of these slabs reflect these tendencies. We observe also considerable disagreement over pointwise spectra for a number of assemblies.Work done while on visiting assignment to Institut de Génie Atomique, E.P.F.L. 相似文献
96.
Information theory offers a means for analyzing some constraints on the reading and copying process in Old English. Entropy for strings of various lengths offers a baseline measure of the uncertainty involved in transmission of Old English texts, while avoiding the pitfalls of applying models of modern reading to early medieval practice. Analysis of lengthy prose and verse texts in Old English revealed uniformly high values for entropy at all string lengths. High entropies may be the result of the language's irregular orthography, poetic koiné, and several dialects and imply that the language may have been easy to write but difficult to read. The low redundancy of the language which its high entropy values indicate suggests that the reader of Old English played an enhanced role in decoding a text and may provide an explanation for the high variability in the transmission of Old English verse.Katherine O'Brien O 'Keeffe is Professor of English at Texas A&M University and a co-director of its Interdisciplinary Group for Historical Literary Study.William Rundell is Professor of Mathematics at Texas A&M University. 相似文献
97.
The kinetics of thermal grooving at the intersection of rhombohedral twin boundaries with the \((10\bar 10)\) plane in aluminium oxide were measured from 1773 to 2273 K. Analysis of the data using the model of Mullins showed that surface diffusion was the dominant mechanism for mass transport. The results were compared with other similar published work on alumina, and the following equation for surface diffusion was determined: $$D_s (cm^2 sec^{ - 1} ) = 4.05 x 10^5 exp - (452kJ mol^{ - 1} /RT).$$ 相似文献
98.
Jaspreet S. Gandhi William J. van Ooij 《Journal of Materials Engineering and Performance》2004,13(4):475-480
Organofunctional silanes recently have emerged as outstanding, environmentally friendly corrosion protectors for metal substrates,
compared with conventional chromate treatments. A simple immersion technique is typically used to coat the metal surface with
silane films. However, the thickness and uniformity of the films are uncontrolled in this process. This paper proposes a new
deposition technique for the silane films on the metal surface, i.e., by electrodeposition. Hydrolyzed silanes are water-soluble,
ionized molecules, so they can be deposited on metals by electrodeposition. Various combinations of silane mixtures were tested
at different voltages, pH values, bath concentrations, and exposure times on panels of alloy aluminum and mirror-polished
ferro-plate. The surface structure was characterized by scanning electron microscopy (SEM) and ellipsometry. The resistance
of the film to corrosion was investigated by direct current (DC) polarization and electrochemical impedance spectroscopy (EIS)
techniques. Electrodeposition results in a more organized and uniform film with fewer pores, compared with immersed or dipped
films.
This paper was presented at the 2nd International Surface Engineering Congress sponsored by ASM International, on September
15–17, 2003, in Indianapolis, Indiana, and appears on pp. 320–26 of the Proceedings. 相似文献
99.
Viscosity data over a temperature range of 37-115°C and a pressure range of 0-10 MPa gauge are presented for a Cold Lake bitumen sample. These data show that the compression of Cold Lake bitumen results in a significant increase in its viscosity. Results are compared with those from a similar study on an Athabasca bitumen sample. Also presented are two correlations for the effects of pressure and temperature on the viscosity of Cold Lake bitumen. 相似文献
100.
Silicon Nitride Derived from an Organometallic Polymeric Precursor: Preparation and Characterization 总被引:1,自引:0,他引:1
Wayde R. Schmidt Vijay Sukumar William J. Hurley Jr. Roberto Garcia Robert H. Doremus Leonard V. Interrante Gary M. Renlund 《Journal of the American Ceramic Society》1990,73(8):2412-2418
Partially crystalline Si3 N4 , with nanosized crystals and a specific surface area greater than 200 m2 /g, is obtained by pyrolysis of a commercially available vinylic polysilane in a stream of anhydrous NH3 to 1000°C. This polymer does not contain N initially. Crystallization to high-purity α-Si3 N4 proceeds with additional heating above 1400°C under N2 . The changes in crystallinity, powder morphology, infrared spectra, and elemental compositions, for samples annealed from 1000° to 1600°C under N2 , are consistent with an amorphous-to-crystalline transformation. Although macroscopic consolidation and local densification occur at 1400°C, volatilization and accompanying weight loss limit bulk densification. The effect of temperature on specific surface area is examined and related to the sintering process. These results are applicable to pyrolysis, decomposition, and crystallization studies of ceramics synthesized by polymeric precursor routes. 相似文献