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   3355篇
  免费   198篇
  国内免费   12篇
电工技术   33篇
综合类   10篇
化学工业   1052篇
金属工艺   85篇
机械仪表   71篇
建筑科学   62篇
矿业工程   12篇
能源动力   152篇
轻工业   161篇
水利工程   20篇
石油天然气   14篇
武器工业   1篇
无线电   309篇
一般工业技术   874篇
冶金工业   157篇
原子能技术   73篇
自动化技术   479篇
  2023年   32篇
  2022年   114篇
  2021年   175篇
  2020年   70篇
  2019年   85篇
  2018年   110篇
  2017年   108篇
  2016年   123篇
  2015年   99篇
  2014年   175篇
  2013年   261篇
  2012年   198篇
  2011年   246篇
  2010年   180篇
  2009年   169篇
  2008年   185篇
  2007年   146篇
  2006年   107篇
  2005年   104篇
  2004年   90篇
  2003年   94篇
  2002年   100篇
  2001年   67篇
  2000年   61篇
  1999年   47篇
  1998年   27篇
  1997年   34篇
  1996年   35篇
  1995年   28篇
  1994年   29篇
  1993年   19篇
  1992年   23篇
  1991年   14篇
  1990年   25篇
  1989年   10篇
  1988年   7篇
  1987年   10篇
  1986年   9篇
  1985年   7篇
  1984年   14篇
  1983年   11篇
  1982年   7篇
  1981年   9篇
  1979年   8篇
  1976年   7篇
  1975年   7篇
  1974年   7篇
  1973年   7篇
  1972年   7篇
  1971年   13篇
排序方式: 共有3565条查询结果,搜索用时 625 毫秒
121.
SMYD3 is a multifunctional epigenetic enzyme with lysine methyltransferase activity and various interaction partners. It is implicated in the pathophysiology of cancers but with an unclear mechanism. To discover tool compounds for clarifying its biochemistry and potential as a therapeutic target, a set of drug-like compounds was screened in a biosensor-based competition assay. Diperodon was identified as an allosteric ligand; its R and S enantiomers were isolated, and their affinities to SMYD3 were determined (KD=42 and 84 μM, respectively). Co-crystallization revealed that both enantiomers bind to a previously unidentified allosteric site in the C-terminal protein binding domain, consistent with its weak inhibitory effect. No competition between diperodon and HSP90 (a known SMYD3 interaction partner) was observed although SMYD3–HSP90 binding was confirmed (KD=13 μM). Diperodon clearly represents a novel starting point for the design of tool compounds interacting with a druggable allosteric site, suitable for the exploration of noncatalytic SMYD3 functions and therapeutics with new mechanisms of action.  相似文献   
122.
123.
We demonstrate that silver nanoisland film self-assembled on the surface of silver-containing glass in the course of thermal processing in hydrogen is capable to detect 10−7 M concentration of rhodamine 6G in water using surface enhanced Raman spectroscopy (SERS) technique. The film can be multiply restored on the same glass substrate via annealing of the glass in hydrogen. We showed that the film can be self-assembled after as much as ten circles of the substrate cleaning followed by annealing. The proposed technique of the silver nanoisland film formation enables multiple usage of the same glass substrate in SERS experiments.  相似文献   
124.
Renewable energy technologies are expected to take the leading role in the forthcoming energy generation portfolio in order to achieve sustainable energy generation. The major constraints for increasing penetration of renewable energy sources is their availability and intermittency, which can be addressed through energy storage when available and energy use when needed. This work reviews the energy storage technologies and gives an up to date comparative summary of the performance parameters of the major energy storage options. The parameters compared here include efficiency, energy capacity, energy density, run time, capital investment costs, response time, lifetime in years and cycles, self discharge and maturity of each energy storage option. The choice of storage system will depend on individual requirements, and may even incorporate more than one energy storage system to increase the energy storage capacity and improve energy security.  相似文献   
125.
We construct universal prediction systems in the spirit of Popper’s falsifiability and Kolmogorov complexity and randomness. These prediction systems do not depend on any statistical assumptions (but under the IID assumption they dominate, to within the usual accuracy, conformal prediction). Our constructions give rise to a theory of algorithmic complexity and randomness of time containing analogues of several notions and results of the classical theory of Kolmogorov complexity and randomness.  相似文献   
126.
127.
Abstract

Inventory management deals with a tradeoff between the benefits of keeping stocks of goods that allows fulfillment of the customer’s demand, and the cost of carrying inventory. Inventory control techniques are very important components and the most organizations can substantially reduce their costs associated with the flow of materials. This paper presents new inventory management model based on particle swarm optimization and pure adaptive search global optimization algorithm in production-inventory system. The proposed model is focusing on planned level of demand for finished goods, production and raw materials cost, production capacity as the norm, change of the production cost and inventory capital cost, all of which are typical factors in automobile manufacture industry. The model determines different factors such as the minimizing inventory quantity, minimizing inventory value, and minimizing production cost based on demand for production items. The model is tested with original real-world dataset obtained from the automotive company Lear from US and its factory in Novi Sad, Serbia.  相似文献   
128.
We aim to develop novel catalysts that exhibit high activity, selectivity and stability under real catalytic conditions. In the recent decades, the fast development of nanoscience and nanotechnology has allowed synthesis of nanoparticles with well-defined size, shape and composition using colloidal methods. Utilization of mesoporous oxide supports effectively prevents the nanoparticles from aggregating at high temperatures and high pressures. Nanoparticles of less than 2?nm sizes were found to show unique activity and selectivity during reactions, which was due to the special surface electronic structure and atomic arrangements that are present at small particle surfaces. While oxide support materials are employed to stabilize metal nanoparticles under working conditions, the supports are also known to strongly interact with the metals through encapsulation, adsorbate spillover, and charge transfer. These factors change the catalytic performance of the metal catalysts as well as the conductivity of oxides. The employment of new in situ techniques, mainly high-pressure scanning tunneling microscopy (HPSTM) and ambient-pressure X-ray photoelectron spectroscopy (APXPS) allows the determination of the surface structure and chemical states under reaction conditions. HPSTM has identified the importance of both adsorbate mobility to catalytic turnovers and the metal substrate reconstruction driven by gaseous reactants such as CO and O2. APXPS is able to monitor both reacting species at catalyst surfaces and the oxidation state of the catalyst while it is being exposed to gases. The surface composition of bimetallic nanoparticles depends on whether the catalysts are under oxidizing or reducing conditions, which is further correlated with the catalysis by the bimetallic catalytic systems. The product selectivity in multipath reactions correlates with the size and shape of monodisperse metal nanoparticle catalysts in structure sensitive reactions.  相似文献   
129.
GPR55 is a GPCR of the non-CB1/CB2 cannabinoid receptor family, which is activated by lysophosphatidylinositol (LPI) and stimulates the proliferation of cancer cells. Anandamide, a bioactive lipid endocannabinoid, acts as a biased agonist of GPR55 and induces cancer cell death, but is unstable and psychoactive. We hypothesized that other endocannabinoids and structurally similar compounds, which are more hydrolytically stable, could also induce cancer cell death via GPR55 activation. We chemically synthesized and tested a set of fatty acid amides and esters for cell death induction via GPR55 activation. The most active compounds appeared to be N-acyl dopamines, especially N-docosahexaenoyl dopamine (DHA-DA). Using a panel of cancer cell lines and a set of receptor and intracellular signal transduction machinery inhibitors together with cell viability, Ca2+, NO, ROS (reactive oxygen species) and gene expression measurement, we showed for the first time that for these compounds, the mechanism of cell death induction differed from that published for anandamide and included neuronal nitric oxide synthase (nNOS) overstimulation with concomitant oxidative stress induction. The combination of DHA-DA with LPI, which normally stimulates cancer proliferation and is increased in cancer setting, had an increased cytotoxicity for the cancer cells indicating a therapeutic potential.  相似文献   
130.
Aliphatic fluorine-18 radiolabeling is the most commonly used method to synthesize tracers for PET-imaging. With an increasing demand for 18F-radiotracers for clinical applications, new labeling strategies aiming to increase radiochemical yields of established tracers or, more importantly, to enable 18F-labeling of new scaffolds have been developed. In recent years, increased attention has been focused on the direct aliphatic 18F-fluorination of base-sensitive substrates in this respect. This minireview gives a concise overview of the recent advances within this field and aims to highlight the advantages and limitations of these methods.  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