全文获取类型
收费全文 | 10074篇 |
免费 | 462篇 |
国内免费 | 20篇 |
学科分类
工业技术 | 10556篇 |
出版年
2023年 | 74篇 |
2022年 | 139篇 |
2021年 | 220篇 |
2020年 | 178篇 |
2019年 | 214篇 |
2018年 | 237篇 |
2017年 | 236篇 |
2016年 | 263篇 |
2015年 | 229篇 |
2014年 | 343篇 |
2013年 | 673篇 |
2012年 | 564篇 |
2011年 | 806篇 |
2010年 | 511篇 |
2009年 | 485篇 |
2008年 | 604篇 |
2007年 | 532篇 |
2006年 | 450篇 |
2005年 | 402篇 |
2004年 | 337篇 |
2003年 | 316篇 |
2002年 | 284篇 |
2001年 | 163篇 |
2000年 | 164篇 |
1999年 | 153篇 |
1998年 | 194篇 |
1997年 | 178篇 |
1996年 | 151篇 |
1995年 | 127篇 |
1994年 | 99篇 |
1993年 | 100篇 |
1992年 | 93篇 |
1991年 | 68篇 |
1990年 | 82篇 |
1989年 | 68篇 |
1988年 | 47篇 |
1987年 | 65篇 |
1986年 | 59篇 |
1985年 | 66篇 |
1984年 | 57篇 |
1983年 | 69篇 |
1982年 | 54篇 |
1981年 | 46篇 |
1980年 | 39篇 |
1979年 | 38篇 |
1978年 | 34篇 |
1977年 | 34篇 |
1976年 | 30篇 |
1975年 | 29篇 |
1973年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Nicholas Biery Marc De Graef Jack Beuth Rafel Raban Andrew Elliott Tresa M. Pollock Curt Austin 《Metallurgical and Materials Transactions A》2002,33(10):3127-3136
Tensile experiments have been performed on specimens of four different investment-cast TiAl-based alloys with variations in
casting conditions. The average ductilities obtained in these experiments vary between approximately 0.8 to 2.0 pct plastic
strain to failure in tension. By using the three-parameter form of the Weibull relation, with the 0.2 pct offset yield strength
as the minimum failure strength, the resulting variability in the data can be quantified and is found to be similar for those
alloys with similar microstructural scale (grain size). Large variations in lamellar volume fraction, segregation, and phase
distribution have a minor influence on property variability, compared to changes in the scale of the grain structure caused
by either variations in cooling rate during casting or the addition of grain refiners. 相似文献
3.
4.
C Andrew Clayton Larry Michael Edo D Pellizzari James J Quackenboss 《Quality Assurance: Good Practice, Regulation, and Law》2003,10(3-4):161-175
Multimedia data from two probability-based exposure studies were investigated in terms of how missing data and measurement-error imprecision affected estimation of population parameters and associations. Missing data resulted mainly from individuals'refusing to participate in certain measurement activities, rather than from field or laboratory problems; it suggests that future studies should focus on methods for maximizing participation rates. Measurement error variances computed from duplicate-sample data were small relative to the inherent variation in the populations; consequently, adjustments in nonparametric percentile estimates to account for measurement imprecision were small. Methods of adjustment based on lognormality assumptions, however, appeared to perform poorly. 相似文献
5.
6.
The Lambda Library (LL) adds a form of lambda functions to C++, which are common in functional programming languages. The LL is implemented as a template library using standard C++; thus no language extensions or preprocessing is required. The LL consists of a rich set of tools for defining unnamed functions. In particular these unnamed functions work seamlessly with the generic algorithms in the C++ Standard Library. The LL offers significant improvements, in terms of generality and ease of use, compared to the current tools in the C++ Standard Library. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
7.
Bartolo A. Clymer B.D. Burgess R.C. Turnbull J.P. 《Signal Processing, IEEE Transactions on》1998,46(8):2243-2248
A new method of implementing efficient FIR filters is presented. It involves approximation of an equiripple FIR by a rounding operation and application of the derived impulse response by a simple recursive equation. The technique is extremely efficient for lowpass, highpass, bandpass, and bandstop filters with sharp transitions and low edge frequencies 相似文献
8.
9.
10.
EH Jeffery K Abreo E Burgess J Cannata JL Greger 《Canadian Metallurgical Quarterly》1996,48(6):649-665
Although the full mechanisms are not yet elucidated, research into the mechanism of toxicity of aluminum (Al) on bone formation and remodeling and on hematopoietic tissue is ongoing. In contrast little information exists on the interactive effects of systemic Al and the kidney. In bone, both clinically and experimentally, high doses of Al inhibit remodeling, slowing both osteoblast and osteoclast activities and producing osteomalacia and adynamic bone disease. In contrast, while very low levels of Al are mitogenic in bones of experimental animals, the effect of low levels of Al in humans is unknown. Aluminum has been shown to have its mitogenic action at the osteoblast, but whether the effect on resorption is viz osteoblast-directed changes in osteoclast activity has not yet been determined. Parathyroid hormone (PTH) levels are disrupted by Al in humans and animals. Whether altered PTH levels play a major or even a minor role in Al-dependent osteotoxicity requires clarification. In hematopoietic tissue, Al causes a microcytic anemia, not reversible by iron. Friend leukemia cells treated with Al have been reported to accumulate excess iron, without incorporating it into ferritin or heme. It is not yet known which steps in iron metabolism are disrupted by Al, if they involve a single mechanism of action, or even if this disruption in iron metabolism accounts for the anemia seen in Al toxicosis. In kidney, research is needed to evaluate Al nephrotoxicity; there are almost no studies in this area. Furthermore, research is needed to evaluate mechanisms of renal Al excretion, presently shown by one study to occur at the distal tubule. Such studies might well throw light on whether Al plays a role in aggravating renal insufficiency, or whether the role of the kidney in Al toxicosis is limited to the causative effect of renal compromise on Al accumulation. In summary, while a number of mechanisms have been proposed for the toxic action of Al, no single mechanism emerges to explain these diverse effects of systemic Al. Recommendations for future research are presented and summarized in Table 1. 相似文献