首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1397篇
  免费   83篇
  国内免费   1篇
电工技术   18篇
化学工业   412篇
金属工艺   17篇
机械仪表   33篇
建筑科学   38篇
能源动力   66篇
轻工业   100篇
水利工程   9篇
石油天然气   1篇
无线电   159篇
一般工业技术   257篇
冶金工业   73篇
原子能技术   5篇
自动化技术   293篇
  2024年   2篇
  2023年   20篇
  2022年   49篇
  2021年   76篇
  2020年   41篇
  2019年   52篇
  2018年   52篇
  2017年   43篇
  2016年   67篇
  2015年   41篇
  2014年   74篇
  2013年   110篇
  2012年   84篇
  2011年   119篇
  2010年   90篇
  2009年   89篇
  2008年   87篇
  2007年   52篇
  2006年   51篇
  2005年   44篇
  2004年   27篇
  2003年   22篇
  2002年   21篇
  2001年   9篇
  2000年   11篇
  1999年   11篇
  1998年   23篇
  1997年   17篇
  1996年   23篇
  1995年   8篇
  1994年   11篇
  1993年   8篇
  1992年   9篇
  1991年   4篇
  1990年   4篇
  1989年   1篇
  1988年   2篇
  1987年   1篇
  1986年   3篇
  1985年   3篇
  1984年   1篇
  1983年   4篇
  1982年   4篇
  1980年   2篇
  1979年   1篇
  1978年   2篇
  1977年   6篇
排序方式: 共有1481条查询结果,搜索用时 0 毫秒
41.
Sarco‐endoplasmic reticulum Ca2+‐ATPase (SERCA), a P‐type ATPase that sustains Ca2+ transport and plays a major role in intracellular Ca2+ homeostasis, represents a therapeutic target for cancer therapy. Here, we investigated whether ruthenium‐based anticancer drugs, namely KP1019 (indazolium [trans‐tetrachlorobis(1H‐indazole)ruthenate(III)]), NAMI‐A (imidazolium [trans‐tetrachloro(1H‐imidazole)(S‐dimethylsulfoxide)ruthenate(III)]) and RAPTA‐C ([Ru(η6p‐cymene)dichloro(1,3,5‐triaza‐7‐phosphaadamantane)]), and cisplatin (cis‐diammineplatinum(II) dichloride) might act as inhibitors of SERCA. Charge displacement by SERCA adsorbed on a solid‐supported membrane was measured after ATP or Ca2+ concentration jumps. Our results show that KP1019, in contrast to the other metal compounds, is able to interfere with ATP‐dependent translocation of Ca2+ ions. An IC50 value of 1 μM was determined for inhibition of calcium translocation by KP1019. Conversely, it appears that KP1019 does not significantly affect Ca2+ binding to the ATPase from the cytoplasmic side. Inhibition of SERCA at pharmacologically relevant concentrations may represent a crucial aspect in the overall pharmacological and toxicological profile of KP1019.  相似文献   
42.
Due to the incompleteness of animal genome sequencing, the analysis and characterization of serum proteomes of most farm animals are still in their infancy, compared to the already well-documented human serum proteome. This review focuses on the implications of the farm animal serum proteomics in order to identify novel biomarkers for animal welfare, early diagnosis, prognosis and monitoring of infectious disease treatment, and develop new vaccines, aiming at determining the reciprocal benefits for humans and animals.  相似文献   
43.
In a standard cointegrating framework, Phillips (1991) introduced the weighted covariance (WC) estimator of cointegrating parameters. Later, Marinucci (2000) applied this estimator to fractional circumstances and, like Phillips (1991), analysed the so‐called small‐b asymptotic approximation to its sampling distribution. Recently, an alternative limiting theory (fixed‐b asymptotics) has been successfully employed to approximate sampling distributions. With the purpose of comparing both approaches, we derive here the fixed‐b limit of WC estimators in a fractional setting, filling also some gaps in the traditional (small‐b) theory. We also provide some Monte Carlo evidence that suggests that the fixed‐b limit is more accurate.  相似文献   
44.
45.
The human immunodeficiency virus type-1 (HIV-1) is able to shield immunogenic peptide epitopes on its envelope spike (a trimer of two glycoproteins, gp120 and gp41) by presenting numerous host-derived N-linked glycans. Nevertheless, broadly neutralizing antibodies against gp120 and gp41 have been isolated from HIV-1-infected patients and provide protection against viral challenge in animal models. Among these, the monoclonal antibody 2G12 binds to clusters of high-mannose-type glycans that are present on the surface of gp120. These types of glycans have thus been envisaged as target structures for the development of synthetic agents capable of eliciting 2G12-like antibodies. High-resolution structural studies of 2G12 and chemically defined glycan-type ligands, including crystallographic data, have been performed to gain an insight into this interaction. Further studies are still required to design a carbohydrate-based vaccine for HIV. Our previous NMR studies highlighted different recognition modes of two branched synthetic oligosaccharides, a penta- and a heptamannoside, by 2G12 in solution. In order to clarify the underlying structural reasons for such different behaviors, we have herein "dissected" the branches into the linear tri- and tetra- oligomannosides by chemical synthesis and studied their interactions with 2G12 in solution by saturation transfer difference (STD) NMR spectroscopy. The results confirm the distinct preferences of 2G12 for the studied branches and afford explanations for the observed differences. This study provides important structural information for further ligand optimizations. Possible effects of structural modifications on the solvent-exposed end of the ligands are also discussed.  相似文献   
46.
We report novel molecules incorporating the nontoxic squalene scaffold and different carbonic anhydrase inhibitors (CAIs). Potent inhibitory action, in the low-nanomolar range, was detected against isoforms hCA II for sulfonamide derivatives, which proved to be selective against this isoform over the tumor-associate hCA IX and XII isoforms. On the other hand, coumarin derivatives showed weak potency but high selectivity against the tumor-associated isoform CA IX. These compounds are interesting candidates for preclinical evaluation in glaucoma or various tumors in which the two enzymes are involved. In addition, an in silico study of inhibitor-bound hCA II revealed extensive interactions with the hydrophobic pocket of the active site and provided molecular insights into the binding properties of these new inhibitors.  相似文献   
47.
48.
Ablation resistance and mechanical properties of polyurethane-based composites containing different amounts (up to 5 wt%) of organoclay were correlated with the morphological characterization. The crosslinking density of the polyurethane increased with the amount of organoclay. At low concentration (up to 1 wt%), the organoclay was well exfoliated, while at higher concentration, both exfoliated and intercalated platelets were found. A linear correlation was observed between the tensile test and the concentration of organoclay. Erosion velocity decreased 40% with the incorporation of 5% of organoclay. POLYM. ENG. SCI., 60:630–635, 2020. © 2020 Society of Plastics Engineers  相似文献   
49.
Light- induced polymeric 3D printing is becoming a well-established fabrication method, showing manifold advantages such as control of the local chemistry of the manufactured devices. It can be considered a green technology, since the parts are produced when needed and with minimum amount of materials. In this work 3D printing is combined with another green technology, microwave-assisted reaction, to fabricate objects of complex geometry with controllable surface properties, exploiting the presence of remaining functional groups on the surface of 3D printed specimens. In this context, surface functionalization with different amines is studied, optimizing formulations, reaction times, and avoiding surface deterioration. Then, two different applications are investigated. MW-functionalized filter-type structures have been tested against Staphylococcus aureus bacteria, showing high bactericidal activity on the surface along all areas of the complex-shaped structure. Second, a fluidic chip composed of three separated channels is 3D printed, filled with different amine-reactive dyes (dansyl and eosine derivatives), and made to react simultaneously. Complete and independent functionalization of the surface of the three channels is achieved only after 2 min of irradiation. This study demonstrates that light induced 3D printing and microwave-induced chemistry can be used together effectively, and used to produce functional devices.  相似文献   
50.
A possibility to carry out sorption-enhanced gasification (SEG) is represented by its integration with the calcium looping concept in dual interconnected fluidized beds (DIFB). This article is focused on the sorbent CO2 uptake performance and attrition/fragmentation tendency when operating conditions simulating those of a DIFB-SEG process are adopted. Experiments were carried out on a commercial Italian limestone in a laboratory-scale DIFB reactor. Carbonation was carried out in a range of test conditions, including variable temperature (600–700°C) and absence/presence of steam (10% by volume); CO2 concentration was set at 10% by volume. The characterization is extended by investigating the behavior of preprocessed DIFB-SEG samples on impact fragmentation tests, conducted in an ex situ apparatus. Tests were carried out for impact velocities in the range 17–45 m/s. Results were discussed considering both the impact velocity value and the operating conditions under which the sample was preprocessed in the fluidized bed.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号