全文获取类型
收费全文 | 417篇 |
免费 | 29篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 3篇 |
化学工业 | 119篇 |
金属工艺 | 8篇 |
机械仪表 | 15篇 |
建筑科学 | 3篇 |
能源动力 | 14篇 |
轻工业 | 7篇 |
武器工业 | 1篇 |
无线电 | 44篇 |
一般工业技术 | 129篇 |
冶金工业 | 11篇 |
原子能技术 | 10篇 |
自动化技术 | 84篇 |
出版年
2023年 | 3篇 |
2022年 | 14篇 |
2021年 | 22篇 |
2020年 | 7篇 |
2019年 | 9篇 |
2018年 | 17篇 |
2017年 | 7篇 |
2016年 | 16篇 |
2015年 | 13篇 |
2014年 | 25篇 |
2013年 | 24篇 |
2012年 | 28篇 |
2011年 | 47篇 |
2010年 | 24篇 |
2009年 | 25篇 |
2008年 | 25篇 |
2007年 | 23篇 |
2006年 | 21篇 |
2005年 | 16篇 |
2004年 | 13篇 |
2003年 | 11篇 |
2002年 | 19篇 |
2001年 | 5篇 |
2000年 | 5篇 |
1998年 | 6篇 |
1997年 | 3篇 |
1996年 | 6篇 |
1995年 | 7篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
排序方式: 共有448条查询结果,搜索用时 31 毫秒
31.
Natalia V. Pozdniakova Oxana V. Ryabaya Alevtina S. Semkina Vsevolod A. Skribitsky Alexei B. Shevelev 《International journal of molecular sciences》2022,23(6)
Three artificial proteins that bind the gadolinium ion (Gd3+) with tumour-specific ligands were de novo engineered and tested as candidate drugs for binary radiotherapy (BRT) and contrast agents for magnetic resonance imaging (MRI). Gd3+-binding modules were derived from calmodulin. They were joined with elastin-like polypeptide (ELP) repeats from human elastin to form the four-centre Gd3+-binding domain (4MBS-domain) that further was combined with F3 peptide (a ligand of nucleolin, a tumour marker) to form the F3-W4 block. The F3-W4 block was taken alone (E2-13W4 protein), as two repeats (E1-W8) and as three repeats (E1-W12). Each protein was supplemented with three copies of the RGD motif (a ligand of integrin αvβ3) and green fluorescent protein (GFP). In contrast to Magnevist (a Gd-containing contrast agent), the proteins exhibited three to four times higher accumulation in U87MG glioma and A375 melanoma cell lines than in normal fibroblasts. The proteins remained for >24 h in tumours induced by Ca755 adenocarcinoma in C57BL/6 mice. They exhibited stability towards blood proteases and only accumulated in the liver and kidney. The technological advantages of using the engineered proteins as a basis for developing efficient and non-toxic agents for early diagnosis of tumours by MRI as well as part of BRT were demonstrated. 相似文献
32.
Tatyana Strekalova Dmitrii Pavlov Alexander Trofimov Daniel C. Anthony Andrei Svistunov Andrey Proshin Aleksei Umriukhin Alexei Lyundup Klaus-Peter Lesch Raymond Cespuglio 《International journal of molecular sciences》2022,23(4)
The phenomenon of individual variability in susceptibility/resilience to stress and depression, in which the hippocampus plays a pivotal role, is attracting increasing attention. We investigated the potential role of hippocampal cyclooxygenase-2 (COX-2), which regulates plasticity, neuroimmune function, and stress responses that are all linked to this risk dichotomy. We used a four-week-long chronic mild stress (CMS) paradigm, in which mice could be stratified according to their susceptibility/resilience to anhedonia, a key feature of depression, to investigate hippocampal expression of COX-2, a marker of microglial activation Iba-1, and the proliferation marker Ki67. Rat exposure, social defeat, restraints, and tail suspension were used as stressors. We compared the effects of treatment with either the selective COX-2 inhibitor celecoxib (30 mg/kg/day) or citalopram (15 mg/kg/day). For the celecoxib and vehicle-treated mice, the Porsolt test was used. Anhedonic (susceptible) but not non-anhedonic (resilient) animals exhibited elevated COX-2 mRNA levels, increased numbers of COX-2 and Iba-1-positive cells in the dentate gyrus and the CA1 area, and decreased numbers of Ki67-positive cells in the subgranular zone of the hippocampus. Drug treatment decreased the percentage of anhedonic mice, normalized swimming activity, reduced behavioral despair, and improved conditioned fear memory. Hippocampal over-expression of COX-2 is associated with susceptibility to stress-induced anhedonia, and its pharmacological inhibition with celecoxib has antidepressant effects that are similar in size to those of citalopram. 相似文献
33.
Ya-Fei Zhao Wen-Jing Ren Ying Zhang Jin-Rong He Hai-Yan Yin Yang Liao Patrizia Rubini Jan M. Deussing Alexei Verkhratsky Zeng-Qiang Yuan Peter Illes Yong Tang 《International journal of molecular sciences》2022,23(3)
Extracellular adenosine 5′-triphosphate (ATP) in the brain is suggested to be an etiological factor of major depressive disorder (MDD). It has been assumed that stress-released ATP stimulates P2X7 receptors (Rs) at the microglia, thereby causing neuroinflammation; however, other central nervous system (CNS) cell types such as astrocytes also possess P2X7Rs. In order to elucidate the possible involvement of the MDD-relevant hippocampal astrocytes in the development of a depressive-like state, we used various behavioral tests (tail suspension test [TST], forced swim test [FST], restraint stress, inescapable foot shock, unpredictable chronic mild stress [UCMS]), as well as fluorescence immunohistochemistry, and patch-clamp electrophysiology in wild-type (WT) and genetically manipulated rodents. The TST and FST resulted in learned helplessness manifested as a prolongation of the immobility time, while inescapable foot shock caused lower sucrose consumption as a sign of anhedonia. We confirmed the participation of P2X7Rs in the development of the depressive-like behaviors in all forms of acute (TST, FST, foot shock) and chronic stress (UCMS) in the rodent models used. Further, pharmacological agonists and antagonists acted in a different manner in rats and mice due to their diverse potencies at the respective receptor orthologs. In hippocampal slices of mice and rats, only foot shock increased the current responses to locally applied dibenzoyl-ATP (Bz-ATP) in CA1 astrocytes; in contrast, TST and restraint depressed these responses. Following stressful stimuli, immunohistochemistry demonstrated an increased co-localization of P2X7Rs with a microglial marker, but no change in co-localization with an astroglial marker. Pharmacological damage to the microglia and astroglia has proven the significance of the microglia for mediating all types of depression-like behavioral reactions, while the astroglia participated only in reactions induced by strong stressors, such as foot shock. Because, in addition to acute stressors, their chronic counterparts induce a depressive-like state in rodents via P2X7R activation, we suggest that our data may have relevance for the etiology of MDD in humans. 相似文献
34.
Steffen A Schroeder W Macdonald R Poissant L Konoplev A 《The Science of the total environment》2005,342(1-3):185-198
Eight years of gaseous elemental mercury (GEM) concentration measurements from Alert, Nunavut, Canada (between 1995 and 2002) is presented. The annual time series shows a distinct repeating seasonal pattern with an overall annual median concentration for this time period of 1.58 (S.D.=0.04 ng m(-3)). Strong seasonal variation was observed throughout the years with springtime displaying strong variability in the GEM and overall lower median concentrations due to the so-called mercury depletion events (MDEs). Summer concentrations are higher than the annual average and show a decrease in variability. Fall and winter concentrations are distributed around the annual median concentrations and show little variability. The relationship between the springtime depression and the summer increase shows a change in the behaviour of mercury between 1995 and 2002. Preliminary results suggest that during this period an increasing amount of the mercury lost from the atmosphere in the spring is not returned to atmosphere in summer. A comparison of GEM concentration data from three sites--Alert (Canada), Amderma (Russia) and Kuujjuarapik (Canada)--demonstrated similar monthly distribution of GEM between Alert and Amderma, with the latter not showing as high summer concentrations. Monthly distribution of GEM at Kuujjuarapik varied considerably from the other two sites. MDEs were found to occur at each site in the spring yet displayed different characteristics. MDEs appear to start at Alert shortly after polar sunrise but in Amderma their initiation is delayed approximately 2 months following polar sunrise. MDEs occur in Kuujjuarapik in the springtime despite an incomplete development of the polar day-night cycle. In spring, as soon as air temperature attained temperatures consistently above 0 degrees C, MDEs ended immediately at all three sites. Continued studies into MDEs are warranted, but clearly an important component of future studies must focus on the origins of the variation of GEM behaviour at different sites. 相似文献
35.
36.
Xianqin Meng Guillaume Gomard Ounsi El Daif Emmanuel Drouard Regis Orobtchouk Anne Kaminski Alain Fave Mustapha Lemiti Alexei Abramov Pere Roca i Cabarrocas Christian Seassal 《Solar Energy Materials & Solar Cells》2011
In this paper, we present the integration of an absorbing photonic crystal within a thin-film photovoltaic solar cell. Optical simulations performed on a complete solar cell revealed that patterning the hydrogenated amorphous silicon active layer as a 2D photonic crystal membrane enabled to increase its integrated absorption by 28 % between 300 and 720 nm, comparing to a similar but unpatterned stack. In order to fabricate such promising cells, we developed a high throughput process based on holographic lithography and reactive ion etching. The influences of the parameters taking part in those processes on the obtained patterns are discussed. Optical measurements performed on the resulting “photonized” solar cell structures underline the regularity of the 2D pattern and a significant absorption increase above 550 nm, similarly to what is observed on the simulated absorption spectra. Moreover, our patterned cells are found to be robust with regards to the angle of incidence of the light. 相似文献
37.
Matching Trajectories of Anatomical Landmarks Under Viewpoint,Anthropometric and Temporal Transforms
Alexei Gritai Yaser Sheikh Cen Rao Mubarak Shah 《International Journal of Computer Vision》2009,84(3):325-343
An approach is presented to match imaged trajectories of anatomical landmarks (e.g. hands, shoulders and feet) using semantic
correspondences between human bodies. These correspondences are used to provide geometric constraints for matching actions
observed from different viewpoints and performed at different rates by actors of differing anthropometric proportions. The
fact that the human body has approximate anthropometric proportion allows innovative use of the machinery of epipolar geometry
to provide constraints for analyzing actions performed by people of different sizes, while ensuring that changes in viewpoint
do not affect matching. In addition, for linear time warps, a novel measure, constructed only from image measurements of the
locations of anatomical landmarks across time, is proposed to ensure that similar actions performed at different rates are
accurately matched as well. An additional feature of this new measure is that two actions from cameras moving at constant
(and possibly different) velocities can also be matched. Finally, we describe how dynamic time warping can be used in conjunction
with the proposed measure to match actions in the presence of nonlinear time warps. We demonstrate the versatility of our
algorithm in a number of challenging sequences and applications, and report quantitative evaluation of the matching approach
presented. 相似文献
38.
The cationic polymerization of cyclopentadiene (CPD) with 1-(4-methoxyphenyl)ethanol (1)/BF3OEt2 initiating system in CH2Cl2:CH3CN 4:1 (v/v) mixture at room temperature and in the presence of water ([H2O]/[BF3OEt2] up to 8) is reported. The number-average molecular weights of obtained polymers increased in direct proportion to monomer
conversion or initial monomer concentration (M
n ≤ 4,000 g mol−1) in agreement with calculated values, and were inversely proportional to initiator concentration. Polymer MWDs were relatively
narrow (M
w/M
n = 1.4–1.7) up to 60% of monomer conversion. It was also shown that regioselectivity of CPD polymerization with 1/BF3OEt2 initiating system did not depend significantly on water, monomer, or initiator concentration (1,4-structures content was
nearly 60% in all cases). 相似文献
39.
Kholdeeva Oxana A. Ivanchikova Irina D. Maksimchuk Nataliya V. Melgunov Maxim S. Chang Jong-San Guidotti Matteo Shutilov Alexei A. Zaikovskii Vladimir I. 《Topics in Catalysis》2014,57(17):1377-1384
Catalytic properties of Ti-containing porous solids were compared in the oxidation of 2,3,6-trimethylphenol (TMP) with H2O2 to produce 2,3,5-trimethyl-1,4-benzoquinone (TMBQ, vitamin E key intermediate). Mesoporous titanium–silicates with di(oligo)nuclear Ti centers, metal–organic framework MIL-125 and amorphous TiO2 demonstrated 100 % selectivity toward TMBQ. Titanium–silicates prepared by evaporation-induced self-assembly revealed superior performance in terms of product yield and catalyst reusability.
相似文献40.
Lyapustin A 《Applied optics》2002,41(27):5607-5615
Results of an extensive validation study of the new radiative transfer code SHARM-3D are described. The code is designed for modeling of unpolarized monochromatic radiative transfer in the visible and near-IR spectra in the laterally uniform atmosphere over an arbitrarily inhomogeneous anisotropic surface. The surface boundary condition is periodic. The algorithm is based on an exact solution derived with the Green's function method. Several parameterizations were introduced into the algorithm to achieve superior performance. As a result, SHARM-3D is 2-3 orders of magnitude faster than the rigorous code SHDOM. It can model radiances over large surface scenes for a number of incidence-view geometries simultaneously. Extensive comparisons against SHDOM indicate that SHARM-3D has an average accuracy of better than 1%, which along with the high speed of calculations makes it a unique tool for remote-sensing applications in land surface and related atmospheric radiation studies. 相似文献