全文获取类型
收费全文 | 596085篇 |
免费 | 4497篇 |
国内免费 | 1694篇 |
专业分类
电工技术 | 11008篇 |
综合类 | 660篇 |
化学工业 | 90999篇 |
金属工艺 | 23496篇 |
机械仪表 | 18876篇 |
建筑科学 | 13125篇 |
矿业工程 | 3281篇 |
能源动力 | 15772篇 |
轻工业 | 48656篇 |
水利工程 | 6299篇 |
石油天然气 | 11492篇 |
武器工业 | 67篇 |
无线电 | 67995篇 |
一般工业技术 | 116829篇 |
冶金工业 | 111762篇 |
原子能技术 | 13321篇 |
自动化技术 | 48638篇 |
出版年
2021年 | 5644篇 |
2020年 | 4466篇 |
2019年 | 5677篇 |
2018年 | 8820篇 |
2017年 | 8839篇 |
2016年 | 9560篇 |
2015年 | 5978篇 |
2014年 | 9940篇 |
2013年 | 27984篇 |
2012年 | 15890篇 |
2011年 | 21503篇 |
2010年 | 17099篇 |
2009年 | 19149篇 |
2008年 | 19786篇 |
2007年 | 19652篇 |
2006年 | 17627篇 |
2005年 | 15655篇 |
2004年 | 14826篇 |
2003年 | 14622篇 |
2002年 | 14187篇 |
2001年 | 13941篇 |
2000年 | 13190篇 |
1999年 | 13615篇 |
1998年 | 34168篇 |
1997年 | 23668篇 |
1996年 | 18274篇 |
1995年 | 13786篇 |
1994年 | 12097篇 |
1993年 | 12089篇 |
1992年 | 8963篇 |
1991年 | 8354篇 |
1990年 | 8494篇 |
1989年 | 8048篇 |
1988年 | 7710篇 |
1987年 | 6758篇 |
1986年 | 6690篇 |
1985年 | 7601篇 |
1984年 | 7064篇 |
1983年 | 6378篇 |
1982年 | 5907篇 |
1981年 | 6053篇 |
1980年 | 5717篇 |
1979年 | 5513篇 |
1978年 | 5533篇 |
1977年 | 6232篇 |
1976年 | 8096篇 |
1975年 | 4795篇 |
1974年 | 4514篇 |
1973年 | 4666篇 |
1972年 | 3922篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Physical and chemical characterization of thermosoftened bases for molten filled hard gelatin capsule formulations 总被引:1,自引:0,他引:1
A. R. Hawley G. Rowley W. J. Lough S. Chatham 《Drug development and industrial pharmacy》1992,18(16):1719-1739
Dynafill, Dynasan-114, Lutrol-F68, PEG-10000 and PEG-20000 have been examined as potential bases for the preparation of fusion formed solid dispersions for molten filling into hard gelatin capsules. Investigations included, an examination of thermal effects on crystal structure by DSC and XRD, a theological study to evaluate capsule filling characteristics, dissolution studies on drug/base formulations, chemical analysis for free fatty acid impurities in Dynafill and Dynasan-114, and detailed studies on selected drug/base formulations. PEG-20000 and Dynasan-114 were not examined in detail, after preliminary investigations had shown high viscosity and poor filling characteristics for PEG-20000 and poor dissolution characteristics for Dynasan-114. Dynafill provided good release profiles when formulated with a variety of model drugs (Acetohexamide, Ibuprofen, Indomethacin, Quinidine sulphate and Theophylline). Results from hot stage photomicrography supported by DSC and XRD were used to construct a phase diagram of the Ibuprofen/Lutrol-F68 system. The evidence from the phase diagram indicated the formulation of a simple eutectic system with no solid solubility and a eutectic composition at approximately 35% w/w Ibuprofen. 相似文献
992.
V. N. Eremenko L. S. Kriklya V. G. Khoruzhaya 《Powder Metallurgy and Metal Ceramics》1992,31(3):243-248
Translated from Poroshkovaya Metallurgiya, No. 3, pp. 61–67, March, 1992. 相似文献
993.
994.
995.
The present paper uses a classical Galerkin weighted residual formulation to obtain the approximate analytical solution of a thermally loaded beam executing free flexural vibrations. The approach used is one where the time variable is considered in the same manner as the spatial variable, and is included in the basis functions. The basis functions used in the approach are polynomials obtained from the terms of a power series, with the condition of nullity on the boundary. This choice simplifies the algebraic manipulations considerably and yields close form expressions for components of the system matrix. The latter also simplifies the numerical computation of coefficients of the approximating polynomial. The approach provides benefits in terms of increased accuracy and lower computational costs. 相似文献
996.
Translated from Poroshkovaya Metallurgiya, No. 11(359), pp. 71–73, November, 1992. 相似文献
997.
This paper presents a space-domain method of moments (MoM) solution to the problem of a strip dipole on a dielectric slab. The solution involves the use of a special junction basis function which models the nearly singular polarization currents in the vicinity of the strip/dielectric junction 相似文献
998.
The authors undertook the Solar System Modeler project to improve comprehension and appreciation of the size, complexity, and splendor of the solar system. To do so, the Solar System Modeler must (1) accurately portray the orbital behavior of satellites, planets, comets, and other celestial bodies, and (2) function in a distributed virtual environment. Additionally, the system needs to: provide a flexible, 3D graphical user interface for immersive operation; assist the user in comprehending the state of the virtual environment; accurately portray the stars and their locations; graphically model all bodies throughout the solar system in 3D and to the same scale; and maintain an interactive frame rate. They describe how they met these requirements 相似文献
999.
C Cepollaro S Gonnelli C Pondrelli S Martini A Montagnani S Rossi L Gennari C Gennari 《Canadian Metallurgical Quarterly》1997,70(835):691-696
Measurement of ultrasonographic parameters provides information concerning not only bone density but also bone architecture. We investigated the usefulness of ultrasonographic parameters and bone mineral density for evaluating the probability of vertebral fracture. 397 postmenopausal women (59.1 +/- 6.0 years) with (n = 178) or without (n = 219) atraumatic vertebral fractures were studied. In all women, bone mineral density (BMD) of the lumbar spine was evaluated by dual X-ray absorptiometry (DXA) and speed of sound (SOS); broadband ultrasound attenuation (BUA) and Stiffness in the calcaneus were evaluated by an Achilles unit (Lunar Corporation). Ultrasonographic parameters and BMD were compared by examining the magnitude of the odds ratios, to determine which produces the highest estimate of the probability of odds of fracture, and by examining widths of the respective confidence intervals (CI) to show which estimate of odd ratio is the most precise. The relative risk of vertebral fracture, after adjusting for potential confounders, was 3.5 (CI 2.6-4.8) for BUA; 4.5 (CI 3.2-6.2) for SOS; 5.8 (CI 4.0-8.4) for Stiffness and 7.5 (CI 4.8-11.5) for BMD. Ultrasound (US) parameters were still significant independent predictors of vertebral fracture, even after adjusting for BMD. The relative risk of fracture for a simultaneous decrease by 1 SD of BMD and by 1 SD of each ultrasound parameter was 17.3 (CI 9.4-39.6) for BMD and SOS; 18.3 (CI 8.4-30.6) for BMD and BUA and 22.1 (CI 8.9-52.7) for BMD and Stiffness. Our data suggest that US and BMD provide complementary information which can be combined to improve estimates of vertebral fracture risk. 相似文献
1000.
P Sánchez García 《Canadian Metallurgical Quarterly》1997,114(1):157-63; discussion 164-7