全文获取类型
收费全文 | 1593篇 |
免费 | 59篇 |
国内免费 | 10篇 |
学科分类
工业技术 | 1662篇 |
出版年
2023年 | 8篇 |
2022年 | 9篇 |
2021年 | 19篇 |
2020年 | 10篇 |
2019年 | 13篇 |
2018年 | 20篇 |
2017年 | 25篇 |
2016年 | 26篇 |
2015年 | 27篇 |
2014年 | 41篇 |
2013年 | 88篇 |
2012年 | 58篇 |
2011年 | 97篇 |
2010年 | 67篇 |
2009年 | 70篇 |
2008年 | 91篇 |
2007年 | 65篇 |
2006年 | 71篇 |
2005年 | 49篇 |
2004年 | 65篇 |
2003年 | 52篇 |
2002年 | 68篇 |
2001年 | 32篇 |
2000年 | 31篇 |
1999年 | 29篇 |
1998年 | 28篇 |
1997年 | 18篇 |
1996年 | 21篇 |
1995年 | 25篇 |
1994年 | 30篇 |
1993年 | 24篇 |
1992年 | 24篇 |
1991年 | 15篇 |
1990年 | 20篇 |
1989年 | 23篇 |
1988年 | 20篇 |
1987年 | 15篇 |
1986年 | 15篇 |
1985年 | 29篇 |
1984年 | 14篇 |
1983年 | 22篇 |
1982年 | 16篇 |
1981年 | 14篇 |
1980年 | 21篇 |
1979年 | 23篇 |
1978年 | 18篇 |
1977年 | 9篇 |
1976年 | 16篇 |
1975年 | 20篇 |
1974年 | 11篇 |
排序方式: 共有1662条查询结果,搜索用时 213 毫秒
31.
Claude S. Fischer Mark Baldassare Richard J. Ofshe 《Journal of the American Planning Association. American Planning Association》2013,79(6):406-418
In recent years, a great deal of speculation and research has appeared on the topic of whether population density has serious social psychological consequences. In this article, we review the crowding literature with particular concern for its implications for urban life. First, we examine the extant research and draw two conclusions: that much of the work is methodologically or conceptually limited; and, that density, though perceived as unpleasant, does not appear to have definite and consistent detrimental effects. Second, we consider the theoretical relevance of this literature to urban studies, find it lacking in certain respects, and suggest solutions to the problem of relevance. Finally, we present several theoretical frameworks for guiding future research on the effects of urban density. 相似文献
32.
Philippe Nika Yannick Bailly Michel De Labachelerie Jean Claude Jeannot Jacques De Lallee 《Nanoscale and Microscale Thermophysical Engineering》2013,17(4):301-325
The miniaturization of refrigerating systems represents a very current scientific and technical challenge to improve the performances of numerous electronic components. This work presents a global approach to the problem and suggests studying the cooling by means of small channels filled with an oscillating gas: the double inlet pulse tube refrigerator (DIPTR). A great level of miniaturization based on the technology of carving silicon is exposed. This study proposes to apply an electric analogy for modeling both hydrodynamic and thermal phenomena. Considering the complexity of the theoretical problem including mechanical, thermal, thermodynamical, and acoustic considerations, the authors take care to summarize the main governing equations in a particular form so any scientific engineer could understand the DIPTR principle. 相似文献
33.
34.
Wendie L. Claeys Jean-François Schmit Claude Bragard Guy Maghuin-Rogister Luc Pussemier Bruno Schiffers 《Food Control》2011,22(3-4):508-516
The output of a pesticide surveillance program (detection frequency and number of exceeding measures) can lead to unnecessary concern among consumers since they lack information concerning the actual exposure. In this study, the exposure to pesticide residues through fruit and vegetable consumption is evaluated based on the 2008 surveillance data of the Belgian Federal Agency for the Safety of the Food Chain (FASFC).Results (deterministic and probabilistic approach) demonstrate that the chronic exposure of the adult population (>15 years) is generally under control, even at high or frequent consumption of fruit and vegetables. For most of the pesticide residues studied, the exposure is one hundred times lower than the ‘acceptable daily intake’ or ADI. With regard to children (2–5 years) who consume regularly or large amounts of fruit and vegetables, there are however, indications that for some pesticides the ADI can be exceeded. Nevertheless, due to the large uncertainty in these calculations, a more detailed study is required for this vulnerable group of consumers. In addition, it was demonstrated that washing and peeling of fruit and vegetables result in an exposure that is probably five to six times lower. 相似文献
35.
Damien Steyer Claude Erny Patricia Claudel Geneviève Riveill Francis Karst Jean-Luc Legras 《Food microbiology》2013
Geraniol produced by grape is the main precursor of terpenols which play a key role in the floral aroma of white wines. We investigated the fate of geraniol during wine fermentation by Saccharomyces cerevisiae. The volatile compounds produced during fermentation of a medium enriched with geraniol were extracted by Stir-bar sorptive extraction and analysed by GC–MS. We were able to detect and quantify geranyl acetate but also citronellyl- and neryl-acetate. The presence of these compounds partly explains the disparition of geraniol. The amounts of terpenyl esters are strain dependant. We demonstrated both by gene overexpression and gene-deletion the involvement of ATF1 enzyme but not ATF2 in the acetylation of terpenols. The affinity of ATF1 enzyme for several terpenols and for isoamyl alcohol was compared. We also demonstrated that OYE2 is the enzyme involved in geraniol to citronellol reduction. Fermenting strain deleted from OYE2 gene produces far less citronellol than wild type strain. Moreover lab strain over-expressing OYE2 allows 87% geraniol to citronellol reduction in bioconversion experiment compared to about 50% conversion with control strain. 相似文献
36.
37.
38.
Fabrice Burel Hassan Oulyadi Claude Bunel Vladimir Grishchenko Natalya Busko Antonina Barantsova Vitaly Boiko 《Journal of Polymer Research》2011,18(6):2265-2273
Azo-bis(isobutyroamidoxime) was synthesized and used as functionalized initiator to prepare a liquid isoprene bearing amidoxime
end groups via radical polymerization. The polymer was characterized by FT-IR, Gel Permeation Chromatography and NMR. In particular,
the structure of the polymer was investigated using 1D and 2D NMR techniques. The distribution of the different isoprene units
(1,4-trans, 1,4-cis, 1,2 and 3,4), as well as the structure of the amidoxime end-groups was determined. It was found that
the structure of the end groups was governed by the steric hindrance of the initiator. Only 1,4 and 4,1 functionalized end
units were evidenced, with a majority of 4,1 end units. 相似文献
39.
We present a novel hierarchical grid based method for fast collision detection (CD) for deformable models on GPU architecture. A two‐level grid is employed to accommodate the non‐uniform distribution of practical scene geometry. A bottom‐to‐top method is implemented to assign the triangles into the hierarchical grid without any iteration while a deferred scheme is introduced to efficiently update the data structure. To address the issue of load balancing, which greatly influences the performance in SIMD parallelism, a propagation scheme which utilizes a parallel scan and a segmented scan is presented, distributing workloads evenly across all concurrent threads. The proposed method supports both discrete collision detection (DCD) and continuous collision detection (CCD) with self‐collision. Some typical benchmarks are tested to verify the effectiveness of our method. The results highlight our speedups over prior algorithms on different commodity GPUs. 相似文献
40.