全文获取类型
收费全文 | 1340篇 |
免费 | 60篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 7篇 |
综合类 | 3篇 |
化学工业 | 351篇 |
金属工艺 | 16篇 |
机械仪表 | 20篇 |
建筑科学 | 80篇 |
矿业工程 | 2篇 |
能源动力 | 31篇 |
轻工业 | 249篇 |
水利工程 | 8篇 |
石油天然气 | 5篇 |
无线电 | 73篇 |
一般工业技术 | 214篇 |
冶金工业 | 190篇 |
原子能技术 | 6篇 |
自动化技术 | 147篇 |
出版年
2023年 | 13篇 |
2022年 | 18篇 |
2021年 | 45篇 |
2020年 | 16篇 |
2019年 | 44篇 |
2018年 | 39篇 |
2017年 | 35篇 |
2016年 | 24篇 |
2015年 | 35篇 |
2014年 | 45篇 |
2013年 | 76篇 |
2012年 | 73篇 |
2011年 | 99篇 |
2010年 | 66篇 |
2009年 | 72篇 |
2008年 | 81篇 |
2007年 | 75篇 |
2006年 | 49篇 |
2005年 | 52篇 |
2004年 | 49篇 |
2003年 | 26篇 |
2002年 | 51篇 |
2001年 | 23篇 |
2000年 | 30篇 |
1999年 | 28篇 |
1998年 | 42篇 |
1997年 | 21篇 |
1996年 | 18篇 |
1995年 | 20篇 |
1994年 | 19篇 |
1993年 | 15篇 |
1992年 | 21篇 |
1991年 | 9篇 |
1990年 | 5篇 |
1989年 | 8篇 |
1988年 | 9篇 |
1987年 | 2篇 |
1986年 | 8篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1971年 | 3篇 |
1969年 | 1篇 |
排序方式: 共有1402条查询结果,搜索用时 15 毫秒
1.
Viktoria M. S. Kjær Loukas Ieremias Dr. Viktorija Daugvilaite Dr. Michael Lückmann Prof. Thomas M. Frimurer Prof. Trond Ulven Prof. Mette M. Rosenkilde Dr. Jon Våbenø 《ChemMedChem》2021,16(17):2623-2627
The G protein-coupled receptor GPR183/EBI2, which is activated by oxysterols, is a therapeutic target for inflammatory and metabolic diseases where both antagonists and agonists are of potential interest. Using the piperazine diamide core of the known GPR183 antagonist (E)-3-(4-bromophenyl)-1-(4-(4-methoxybenzoyl)piperazin-1-yl)prop-2-en-1-one (NIBR189) as starting point, we identified and sourced 79 structurally related compounds that were commercially available. In vitro screening of this compound collection using a Ca2+ mobilization assay resulted in the identification of 10 compounds with agonist properties. To enable establishment of initial structure-activity relationship trends, these were supplemented with five in-house compounds, two of which were also shown to be GPR183 agonists. Taken together, our findings suggest that the agonist activity of this compound series is dictated by the substitution pattern of one of the two distal phenyl rings, which functions as a molecular efficacy-switch. 相似文献
2.
Dr. Alexander Fries Dr. Laura S. Mazzaferro Dr. Björn Grüning Dr. Philippe Bisel Karin Stibal Patrick C. F. Buchholz Prof. Dr. Jürgen Pleiss Prof. Dr. Georg A. Sprenger Prof. Dr. Michael Müller 《Chembiochem : a European journal of chemical biology》2019,20(13):1672-1677
Chorismate and isochorismate constitute branch-point intermediates in the biosynthesis of many aromatic metabolites in microorganisms and plants. To obtain unnatural compounds, we modified the route to menaquinone in Escherichia coli. We propose a model for the binding of isochorismate to the active site of MenD ((1R,2S, 5S,6S)-2-succinyl-5-enolpyruvyl-6-hydroxycyclohex-3-ene-1-carboxylate (SEPHCHC) synthase) that explains the outcome of the native reaction with α-ketoglutarate. We have rationally designed variants of MenD for the conversion of several isochorismate analogues. The double-variant Asn117Arg–Leu478Thr preferentially converts (5S,6S)-5,6-dihydroxycyclohexa-1,3-diene-1-carboxylate (2,3-trans-CHD), the hydrolysis product of isochorismate, with a >70-fold higher ratio than that for the wild type. The single-variant Arg107Ile uses (5S,6S)-6-amino-5-hydroxycyclohexa-1,3-diene-1-carboxylate (2,3-trans-CHA) as substrate with >6-fold conversion compared to wild-type MenD. The novel compounds have been made accessible in vivo (up to 5.3 g L−1). Unexpectedly, as the identified residues such as Arg107 are highly conserved (>94 %), some of the designed variations can be found in wild-type SEPHCHC synthases from other bacteria (Arg107Lys, 0.3 %). This raises the question for the possible natural occurrence of as yet unexplored branches of the shikimate pathway. 相似文献
3.
The feature scale planarization of the copper chemical mechanical planarization (CMP) process has been characterized for two
copper processes using Hitachi 430-TU/Hitachi T605 and Cabot 5001/Arch Cu10K consumables. The first process is an example
of an abrasive-free polish with a high-selectivity barrier slurry, while the second is an example of a conventional abrasive
slurry with a low-selectivity barrier slurry. Copper fill planarization has been characterized for structures with conformal
deposition as well as with bumps resulting from bottom-up fill. Dishing and erosion were characterized for several structures
after clearing. The abrasive-free polish resulted in low sensitivity to overpolish and low saturation levels for dishing and
erosion. Consequently, this demonstrated superior performance when compared to the International Technology Roadmap for Semiconductors
(ITRS) 2000 roadmap targets for planarization. While the conventional slurry could achieve the 0.13-μm technology node requirements,
the abrasive-free polish met the planarization requirements beyond the 0.10-μm technology node. 相似文献
4.
Michael Anthony Puso Tod A. Laursen 《International journal for numerical methods in engineering》2002,54(8):1161-1194
In this work, a method is developed for smoothing three‐dimensional contact surfaces. The method can be applied to both regular and irregular meshes. The algorithm employs Gregory patches to interpolate finite element nodes and provide tangent plane continuity between adjacent patches. The resulting surface interpolation is used to calculate gaps and contact forces, in a variationally consistent way, such that contact forces due to normal and frictional contact vary smoothly as slave nodes transition from one patch to the next. This eliminates the ‘chatter’ which typically occurs in a standard contact algorithm when a slave node is situated near a master facet edge. The elimination of this chatter provides a significant improvement in convergence behaviour, which is illustrated by a number of numerical examples. Furthermore, smoothed surfaces also provide a more accurate representation of the actual surface, such that resulting stresses and forces can be more accurately computed with coarse meshes in many problems. This fact is also demonstrated by the numerical examples. Published in 2002 by John Wiley & Sons, Ltd. 相似文献
5.
Heinrich Heydt Philipp Eisenbarth Karin Feith Klaus Urgast Gerhard Maas Manfred Regitz 《Israel journal of chemistry》1986,27(1):96-104
Amino-substituted cyclopropenylium salts ( 11a,b ) react with diazomethyl compounds ( 12a-i ) in dichloromethane or acetonitrile in the presence of a base (ethyldiisopropylamine, 1,5-diazabicyclo[4.3.0] non-5-ene) to form 4-aminopyridazines ( 13a-i ) specifically. The reaction is interpreted in terms of an initial electrophilic diazoalkane substitution to give diazomethylcyclopropenes ( 11 + 12 → 14 ) which undergo a [1.5]-cyclisation to form the betaines 16 which, in turn, isomerise with opening of the bridging bond to give the aminopyridazines 13 . In a similar manner, the tris[amino] cyclopropenylium salts 8a,b and 10a-c are converted to the 3,4,5-tris[amino]-pyridazines ( 21a-k ) by treatment with diazomethyl compounds ( 12a, c-f ). 相似文献
6.
Karin Bucher Jens Mende Michael Mehring Martin Jansen 《Fullerenes, Nanotubes and Carbon Nanostructures》2007,15(1):29-42
A new Eu-endohedral fullerene cage, namely, Eu@C72, was synthesized, separated, and a single isomer, Eu@C72-I, has been isolated by multi-step HPLC for the first time and characterized by LDI-TOF mass spectrometry, UV-Vis and EPR spectroscopy. Additionally, a second isomer, Eu@C72-II, has been separated by HPLC and identified by LDI-TOF mass spectrometry. 相似文献
7.
The ability to accurately and reliably predict whether an older adult will commit suicide has eluded clinicians and researchers. A random national sample of psychologists who work with older adults was surveyed regarding their perception of 36 risk factors for completed suicide and indirect self-destructive behavior in older adults. This study produced a profile of psychologists' assessment and treatment practices when working with suicidal older adults. Determining what psychologists consider to be the most salient risk factors for completed suicide is important in identifying a minimum standard that clinicians should follow when assessing older adults. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
8.
Thompson Karin E.; Malow Robert M.; Corrigan Sheila A.; Sorensen James L. 《Canadian Metallurgical Quarterly》1992,6(2):67
Drug users are particularly at risk for contracting the human immunodeficiency virus and serve as a major mechanism for spreading the virus to other sectors of the population. As a result drug abuse treatment and potential behavioral change strategies are primary public health issues. The purpose of this article is to review the contributions included in this special edition, which represent an effort to describe the most current thinking in the field with a blend of theoretical, review, and empirical articles. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
9.
Karin Metz Stephanie Fl?ter Christoph Kr?ger Carolin Donath Daniela Piontek Sabine Gradl 《Nicotine & tobacco research》2007,9(8):853-863
Smokers with smoking-related diseases who are hospitalized in rehabilitation centers should be offered smoking cessation. This is the first study evaluating whether telephone booster sessions after intensive inpatient treatment are an effective strategy. The present study was conducted in 13 rehabilitation centers for somatic disorders as a prospective multicenter study with a randomized treatment-control group design. We compared abstinence rates after hospital discharge from treatment that included a group smoking cessation program with (treatment group) and without telephone booster sessions (control group). Data from 290 smokers were analyzed. After 6 and 12 months the treatment group achieved abstinence rates twice as high as those of the control group. Men profited more from telephone booster sessions than did women. Results indicated that telephone booster sessions were highly effective (even) after an inherently intensive group program during a hospital stay. Further research should focus on the special needs of women receiving telephone counseling. 相似文献
10.
David Nistr Karin Keis Sten-Eric Lindquist Anders Hagfeldt 《Solar Energy Materials & Solar Cells》2002,73(4)
In this paper a transport equation is derived which describes the behaviour of the nanostructured metal oxide films in a photoelectrochemical cell. It is shown that a detailed analysis of the charge compensation mechanism necessarily leads to a transport equation with characteristics similar to but logically distinct from the pure diffusion equation. The studied phenomenon was named ambipolar diffusion in the early 1950s. It takes into account the fact that the diffusion processes of ions and electrons occur at different speeds. A weak electric field therefore couples the processes together to preserve charge neutrality. The electric field in turn affects the transport resulting in a deviation from purely diffusive behaviour. However, this has not been widely recognised in the literature for nanostructured semiconductor films until very recently. In this paper a detailed analysis is presented. It is based on the assumption that the current density is solenoidal. It is shown that application of the ambipolar diffusion model to a photoelectrochemical cell based on a nanostructured metal oxide film leads to an additional term in the transport equation, rather than only a new diffusion coefficient as in earlier work. It is also shown that the boundary conditions interact closely with the equation to form a transport model. 相似文献