全文获取类型
收费全文 | 3896篇 |
免费 | 78篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 40篇 |
综合类 | 6篇 |
化学工业 | 379篇 |
金属工艺 | 57篇 |
机械仪表 | 53篇 |
建筑科学 | 116篇 |
矿业工程 | 10篇 |
能源动力 | 104篇 |
轻工业 | 337篇 |
水利工程 | 16篇 |
石油天然气 | 19篇 |
无线电 | 235篇 |
一般工业技术 | 345篇 |
冶金工业 | 1830篇 |
原子能技术 | 24篇 |
自动化技术 | 415篇 |
出版年
2022年 | 22篇 |
2021年 | 35篇 |
2020年 | 27篇 |
2019年 | 19篇 |
2018年 | 42篇 |
2017年 | 33篇 |
2016年 | 41篇 |
2015年 | 44篇 |
2014年 | 79篇 |
2013年 | 126篇 |
2012年 | 90篇 |
2011年 | 117篇 |
2010年 | 93篇 |
2009年 | 83篇 |
2008年 | 100篇 |
2007年 | 110篇 |
2006年 | 99篇 |
2005年 | 64篇 |
2004年 | 66篇 |
2003年 | 79篇 |
2002年 | 60篇 |
2001年 | 61篇 |
2000年 | 60篇 |
1999年 | 86篇 |
1998年 | 602篇 |
1997年 | 345篇 |
1996年 | 223篇 |
1995年 | 125篇 |
1994年 | 151篇 |
1993年 | 131篇 |
1992年 | 45篇 |
1991年 | 53篇 |
1990年 | 36篇 |
1989年 | 50篇 |
1988年 | 38篇 |
1987年 | 40篇 |
1986年 | 28篇 |
1985年 | 37篇 |
1984年 | 20篇 |
1983年 | 25篇 |
1982年 | 16篇 |
1981年 | 20篇 |
1980年 | 28篇 |
1978年 | 18篇 |
1977年 | 53篇 |
1976年 | 120篇 |
1975年 | 15篇 |
1974年 | 14篇 |
1973年 | 19篇 |
1972年 | 13篇 |
排序方式: 共有3986条查询结果,搜索用时 375 毫秒
11.
12.
CB Verchere DA D'Alessio S Wang S Andrikopoulos SE Kahn 《Canadian Metallurgical Quarterly》1997,29(6):311-316
Islet amyloid polypeptide forms islet amyloid deposits in non-insulin-dependent diabetes mellitus. We have generated transgenic mice which express human islet amyloid polypeptide in their pancreatic beta cells yet do not develop islet amyloid deposits despite producing levels of the amyloidogenic human peptide 2 - 3 fold higher than the native (mouse) peptide. To determine whether marked overproduction of islet amyloid polypeptide is a potential cause of islet amyloid formation, we increased expression of this transgene by producing homozygous transgenic animals and by making heterozygous mice experimentally insulin resistant with nicotinic acid. Pancreatic content of islet amyloid polypeptide-like immunoreactivity in homozygous and nicotinic acid-treated mice was 2-fold (25 +/- 7 fmol/microg; n = 6) and 3.5-fold (47 +/- 20 fmol/microg; n = 3) higher, respectively, than that of untreated heterozygous animals (13+/-2 fmol/microg; n = 11; both p < 0.05). Despite this marked increase in production of islet amyloid polypeptide, neither group of mice developed gross islet amyloid deposits even after 16 months of age. We conclude that overproduction of islet amyloid polypeptide, even as produced by extreme insulin resistance, is not in itself sufficient for islet amyloid formation. 相似文献
13.
14.
RM Bionta G Blewitt CB Bratton D Casper A Ciocio R Claus M Crouch ST Dye S Errede GW Foster W Gajewski KS Ganezer M Goldhaber TJ Haines TW Jones D Kielczewska WR Kropp JG Learned JM LoSecco J Matthews HS Park LR Price F Reines J Schulz S Seidel E Shumard D Sinclair HW Sobel JL Stone L Sulak R Svoboda G Thornton van der Velde JC C Wuest 《Canadian Metallurgical Quarterly》1987,36(1):30-36
15.
The paper describes a new boundary-layer wind tunnel at the Danish Maritime Institute in Lyngby. The wind tunnel is of the open-circuit type and is integrated into a building raised for the purpose. The design was constrained by the need to provide a simulation of the atmospheric boundary layer (without thermal stratification) and alternatively a uniform flow without excessive turbulence.The wind tunnel has a working section of principal dimensions: length 20.8 m, width 2.6 m and height 1.8 m (adjustable from 1.8 to 2.3 m). The maximum wind speed in the working section when empty is about 26 m s?1.Data acquisition, analysis and instrumentation in relation to the new wind tunnel are discussed and, finally, an example of a simulated natural wind is presented. 相似文献
16.
P. K. Chaviaropoulos I. G. Nikolaou K. A. Aggelis N. N. Soerensen J. Johansen M. O. L. Hansen Mac Gaunaa T. Hambraus Heiko Frhr. von Geyr Ch. Hirsch Kang Shun S. G. Voutsinas G. Tzabiras Y. Perivolaris S. Z. Dyrmose 《风能》2003,6(4):365-385
Aerodynamic modelling of HAWT rotors by means of “engineering methods” has reached a saddle point, where no further development can be expected without a breakthrough in understanding the physics of unsteady, rotating three‐dimensional flows. However, such a breakthrough becomes ever more necessary, as the size of the wind turbines increases. With the experimental work in that direction being mostly limited to observing the phenomena and interpreting the associated mechanisms, and its increased cost, alternatives are being sought. The use of CFD techniques and state‐of‐the‐art Navier–Stokes solvers is considered a very serious contender, a belief shared by the members of the present consortium, which has worked on the VISCEL JOR3‐CT98‐0208 Joule III project. This project's goal was to determine the aerodynamic characteristics as well as the aeroelastic behaviour of wind turbine blades across their broad range of operational conditions, from attached to highly separated flow regimes. The work programme included specific tasks for the validation and assessment of existing 3D solvers, for the parametric study of 3D flow around realistic blades and for the investigation of aeroelastic stability, at the blade section level. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
17.
18.
A patient with B-cell prolymphocytic leukemia (PLL) who has had a prolonged survival is presented. The patient was diagnosed incidentally while asymptomatic, but later developed progressive disease. He was refractory to alkylating agents and fludarabine, but responded to treatment with cyclophosphamide, doxorubicin, vincristine, and prednisone. This patient's prolonged survival may be due partly to his diagnosis at an indolent phase, possibly representing the early phase of the natural course of the disease. Diagnosis, clinical course, and treatment options for PLL are discussed. 相似文献
19.
Hansen P.B. Raybon G. Koren U. Miller B.J. Young M.G. Newkirk M.A. Chien M.-D. Tell B. Burrus C.A. 《Electronics letters》1993,29(9):739-741
A 2 cm long three-contact multisection laser has been fabricated for modelocking at very low repetition rates. Active modelocking yields 8.0-12.3 ps pulses at 2.2, 4.3 and 6.5 GHz corresponding to the fundamental, first, and second harmonics of the cavity resonance frequency. This device demonstrates the feasibility of fabricating monolithic pulse sources operating at rates as low as the OC-48 Sonet transmission rate (2.488 Gbit/s).<> 相似文献
20.
OBJECTIVE: To determine the relationship between serum gamma-glutamyltransferase (GGT) activity and serum IgG concentration in neonatal crias. DESIGN: Prospective observational study. ANIMALS: 21 llama and 4 alpaca crias from 0 to 5 days old. PROCEDURE: Serum GGT activity was measured, using a commercially available kit. Serum IgG concentration was determined by use of radial immunodiffusion. With a serum IgG concentration of 1,000 mg/dl (considered adequate passive transfer), specificity and sensitivity of serum GGT activity in the detection of failure of passive transfer were determined. Regression models were developed to determine the relationship between serum GGT activity and serum IgG concentration. RESULTS: Sensitivity ranged from 0.56 to 0.89, and specificity ranged from 0.88 to 0.31, depending on the value of serum GGT activity chosen as a threshold. Proportion of crias correctly classified ranged from 0.76 to 0.52. Regression models failed to demonstrate a significant relationship between serum GGT activity and serum IgG concentration. CLINICAL IMPLICATIONS: Passive transfer status in crias cannot be accurately predicted on the basis of serum GGT activity. 相似文献