全文获取类型
收费全文 | 1689篇 |
免费 | 59篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 9篇 |
化学工业 | 245篇 |
金属工艺 | 29篇 |
机械仪表 | 16篇 |
建筑科学 | 58篇 |
矿业工程 | 3篇 |
能源动力 | 33篇 |
轻工业 | 183篇 |
水利工程 | 15篇 |
石油天然气 | 7篇 |
无线电 | 105篇 |
一般工业技术 | 272篇 |
冶金工业 | 608篇 |
原子能技术 | 4篇 |
自动化技术 | 163篇 |
出版年
2023年 | 13篇 |
2022年 | 30篇 |
2021年 | 45篇 |
2020年 | 30篇 |
2019年 | 32篇 |
2018年 | 23篇 |
2017年 | 36篇 |
2016年 | 35篇 |
2015年 | 26篇 |
2014年 | 46篇 |
2013年 | 119篇 |
2012年 | 67篇 |
2011年 | 90篇 |
2010年 | 82篇 |
2009年 | 65篇 |
2008年 | 98篇 |
2007年 | 81篇 |
2006年 | 79篇 |
2005年 | 72篇 |
2004年 | 53篇 |
2003年 | 36篇 |
2002年 | 39篇 |
2001年 | 20篇 |
2000年 | 34篇 |
1999年 | 30篇 |
1998年 | 71篇 |
1997年 | 53篇 |
1996年 | 42篇 |
1995年 | 29篇 |
1994年 | 19篇 |
1993年 | 24篇 |
1992年 | 18篇 |
1991年 | 13篇 |
1990年 | 16篇 |
1989年 | 19篇 |
1988年 | 8篇 |
1987年 | 11篇 |
1986年 | 12篇 |
1985年 | 6篇 |
1983年 | 5篇 |
1982年 | 10篇 |
1981年 | 11篇 |
1980年 | 10篇 |
1979年 | 9篇 |
1977年 | 8篇 |
1976年 | 17篇 |
1975年 | 8篇 |
1974年 | 6篇 |
1973年 | 6篇 |
1967年 | 7篇 |
排序方式: 共有1750条查询结果,搜索用时 62 毫秒
1.
2.
Joo H. Kang Eujin Um Alexander Diaz Harry Driscoll Melissa J. Rodas Karel Domansky Alexander L. Watters Michael Super Howard A. Stone Donald E. Ingber 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(42):5657-5666
Magnetic nanoparticles have been employed to capture pathogens for many biological applications; however, optimal particle sizes have been determined empirically in specific capturing protocols. Here, a theoretical model that simulates capture of bacteria is described and used to calculate bacterial collision frequencies and magnetophoretic properties for a range of particle sizes. The model predicts that particles with a diameter of 460 nm should produce optimal separation of bacteria in buffer flowing at 1 L h−1. Validating the predictive power of the model, Staphylococcus aureus is separated from buffer and blood flowing through magnetic capture devices using six different sizes of magnetic particles. Experimental magnetic separation in buffer conditions confirms that particles with a diameter closest to the predicted optimal particle size provide the most effective capture. Modeling the capturing process in plasma and blood by introducing empirical constants (ce), which integrate the interfering effects of biological components on the binding kinetics of magnetic beads to bacteria, smaller beads with 50 nm diameters are predicted that exhibit maximum magnetic separation of bacteria from blood and experimentally validated this trend. The predictive power of the model suggests its utility for the future design of magnetic separation for diagnostic and therapeutic applications. 相似文献
3.
Joshua C. Price Simon J. Levett Valentin Radu David A. Simpson Aina Mogas Barcons Christopher F. Adams Melissa L. Mather 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(22)
Fluorescent nanodiamonds (fNDs) containing nitrogen vacancy (NV) centers are promising candidates for quantum sensing in biological environments. This work describes the fabrication and implementation of electrospun poly lactic‐co‐glycolic acid (PLGA) nanofibers embedded with fNDs for optical quantum sensing in an environment, which recapitulates the nanoscale architecture and topography of the cell niche. A protocol that produces uniformly dispersed fNDs within electrospun nanofibers is demonstrated and the resulting fibers are characterized using fluorescent microscopy and scanning electron microscopy (SEM). Optically detected magnetic resonance (ODMR) and longitudinal spin relaxometry results for fNDs and embedded fNDs are compared. A new approach for fast detection of time varying magnetic fields external to the fND embedded nanofibers is demonstrated. ODMR spectra are successfully acquired from a culture of live differentiated neural stem cells functioning as a connected neural network grown on fND embedded nanofibers. This work advances the current state of the art in quantum sensing by providing a versatile sensing platform that can be tailored to produce physiological‐like cell niches to replicate biologically relevant growth environments and fast measurement protocols for the detection of co‐ordinated endogenous signals from clinically relevant populations of electrically active neuronal circuits. 相似文献
4.
5.
6.
Bruch Monroe A.; Fallon Melissa; Heimberg Richard G. 《Canadian Metallurgical Quarterly》2003,50(1):109
This study examined whether social phobics differed from nonanxious controls in occupational adjustment. Results indicated that generalized and nongeneralized social phobics, in contrast to controls, were underemployed and believed that their supervisor would rate them as less dependable. Nongeneralized social phobics and controls believed their supervisor would rate them higher in work role conformance and likelihood of advancement than did generalized social phobics. Generalized socially phobic women, in contrast to nongeneralized and control group women, were more likely to be employed in noninterpersonally oriented jobs. Generalized social phobics were more anxious than controls when starting their current job but did not differ in job satisfaction. Results are discussed relative to the nature of social phobia, subtype differences, and counseling services. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
7.
Chadwin D. Young Gennadi Bersuker Yuegang Zhao Jeff J. Peterson Joel Barnett George A. Brown Jang H. Sim Rino Choi Byoung Hun Lee Peter Zeitzoff 《Microelectronics Reliability》2005,45(5-6):806
Effects of constant voltage stress (CVS) on gate stacks consisting of an ALD HfO2 dielectric with various interfacial layers were studied with time dependent sensing measurements: DC I–V, pulse I–V, and charge pumping (CP) at different frequencies. The process of injected electron trapping/de-trapping on pre-existing defects in the bulk of the high-κ film was found to constitute the major contribution to the time dependence of the threshold voltage (Vt) shift during stress. The trap generation observed with the low frequency CP measurements is suggested to occur within the interfacial oxide layer or the interfacial layer/high-κ interface, with only a minor effect on Vt. 相似文献
8.
9.
Melissa Kurtz 《Journal of Failure Analysis and Prevention》2007,7(3):175-178
Fuel system assemblies used on recreational watercraft failed after a short time in service in a seawater environment. Examination
of the assemblies revealed significant degradation of the polyacetal connectors of the wire subassemblies. Optical and microscopic
evaluations indicated the complete loss of connector material implying decomposition of the resin, along with mud-cracking
and a rough surface morphology signifying chemical attack. An elemental analysis performed on both an intact connector and
degraded connector suggested a potential chemical agent in the form of zinc chloride. At elevated temperatures, concentrated
zinc chloride solutions are known to decompose polyacetal resins. The source of the zinc chloride was established as corrosion
products that resulted during the dezincification of the internal brass connector through exposure to saltwater in the application. 相似文献
10.
A time-domain test for some types of nonlinearity 总被引:1,自引:0,他引:1
The bispectrum and third-order moment can be viewed as equivalent tools for testing for the presence of nonlinearity in stationary time series. This is because the bispectrum is the Fourier transform of the third-order moment. An advantage of the bispectrum is that its estimator comprises terms that are asymptotically independent at distinct bifrequencies under the hypothesis of linearity. An advantage of the third-order moment is that its values in any subset of joint lags can be used in the test, whereas when using the bispectrum the entire (or truncated) third-order moment is required to construct the Fourier transform. We propose a test for nonlinearity based upon the estimated third-order moment. We use the phase scrambling bootstrap method to give a nonparametric estimate of the variance of our test statistic under the hypothesis. Using a simulation study, we demonstrate that the test obtains its target significance level, with large power, when compared to an existing standard parametric test that uses the bispectrum. Further we show how the proposed test can be used to identify the source of nonlinearity due to interactions at specific frequencies. We also investigate implications for heuristic diagnosis of nonstationarity. 相似文献