全文获取类型
收费全文 | 5202篇 |
免费 | 241篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 43篇 |
综合类 | 4篇 |
化学工业 | 1059篇 |
金属工艺 | 79篇 |
机械仪表 | 97篇 |
建筑科学 | 187篇 |
矿业工程 | 30篇 |
能源动力 | 129篇 |
轻工业 | 339篇 |
水利工程 | 70篇 |
石油天然气 | 12篇 |
武器工业 | 1篇 |
无线电 | 416篇 |
一般工业技术 | 872篇 |
冶金工业 | 1241篇 |
原子能技术 | 33篇 |
自动化技术 | 834篇 |
出版年
2023年 | 30篇 |
2022年 | 46篇 |
2021年 | 90篇 |
2020年 | 69篇 |
2019年 | 77篇 |
2018年 | 83篇 |
2017年 | 85篇 |
2016年 | 116篇 |
2015年 | 108篇 |
2014年 | 166篇 |
2013年 | 285篇 |
2012年 | 255篇 |
2011年 | 370篇 |
2010年 | 264篇 |
2009年 | 288篇 |
2008年 | 307篇 |
2007年 | 307篇 |
2006年 | 246篇 |
2005年 | 193篇 |
2004年 | 183篇 |
2003年 | 176篇 |
2002年 | 154篇 |
2001年 | 113篇 |
2000年 | 109篇 |
1999年 | 97篇 |
1998年 | 97篇 |
1997年 | 94篇 |
1996年 | 85篇 |
1995年 | 73篇 |
1994年 | 74篇 |
1993年 | 81篇 |
1992年 | 50篇 |
1991年 | 43篇 |
1990年 | 53篇 |
1989年 | 61篇 |
1988年 | 51篇 |
1987年 | 42篇 |
1986年 | 38篇 |
1985年 | 47篇 |
1984年 | 47篇 |
1983年 | 32篇 |
1982年 | 32篇 |
1981年 | 43篇 |
1980年 | 22篇 |
1979年 | 20篇 |
1978年 | 36篇 |
1977年 | 21篇 |
1976年 | 23篇 |
1975年 | 15篇 |
1974年 | 15篇 |
排序方式: 共有5446条查询结果,搜索用时 15 毫秒
1.
Olivier Merlin Jeffrey P. Walker Abdelghani Chehbouni Yann Kerr 《Remote sensing of environment》2008,112(10):3935-3946
A deterministic approach for downscaling ~ 40 km resolution Soil Moisture and Ocean Salinity (SMOS) observations is developed from 1 km resolution MODerate resolution Imaging Spectroradiometer (MODIS) data. To account for the lower soil moisture sensitivity of MODIS surface temperature compared to that of L-band brightness temperature, the disaggregation scale is fixed to 10 times the spatial resolution of MODIS thermal data (10 km). Four different analytic downscaling relationships are derived from MODIS and physically-based model predictions of soil evaporative efficiency. The four downscaling algorithms differ with regards to i) the assumed relationship (linear or nonlinear) between soil evaporative efficiency and near-surface soil moisture, and ii) the scale at which soil parameters are available (40 km or 10 km). The 1 km resolution airborne L-band brightness temperature from the National Airborne Field Experiment 2006 (NAFE'06) are used to generate a time series of eleven clear sky 40 km by 60 km near-surface soil moisture observations to represent SMOS pixels across the three-week experiment. The overall root mean square difference between downscaled and observed soil moisture varies between 1.4% v/v and 1.8% v/v depending on the downscaling algorithm used, with soil moisture values ranging from 0 to 15% v/v. The accuracy and robustness of the downscaling algorithms are discussed in terms of their assumptions and applicability to SMOS. 相似文献
2.
We cloned the Saccharomyces kluyveri HIS3 homolog, k-HIS3, and made a partial deletion of the gene. The k-HIS3 gene complemented a HIS3 deletion in S. cerevisiae. The DNA sequences of the open reading frames (ORFs) of the HIS3 homologs are 70% identical at the DNA level and 83% identical at the deduced amino acid level. The ORF upstream of the k-HIS3 gene is related to the PET56 gene of S. cerevisiae found upstream of the HIS3 gene of S. cerevisiae. The ORF downstream from the k-HIS3 gene is not related to the DED1 gene found downstream of the HIS3 gene in S. cerevisiae. 相似文献
3.
4.
Joshua Vaughan Joel Fortgang William Singhose Jeffrey Donnell Thomas Kurfess 《Mechatronics》2008,18(4):179-186
It is commonly accepted that hands-on experiences increase both learning and enjoyment during coursework. Mechatronics projects provide both interesting and relevant hands-on experiences for a wide range of topics including design processes, basic mechatronics concepts, technical communication, and working in a group environment. ME2110: Creative Decisions and Design at Georgia Tech integrates mechatronics and technical communication into a sophomore level mechanical design class. This paper describes the course in detail, highlighting the course goals and layout, tools provided to the students, industry involvement, and the main challenges of administering such a course. 相似文献
5.
The present study evaluated the reliability and validity of the Triage Assessment Survey: Organizations (TAS:O), a 27-item, 5-point, Likert summated rating scale. One hundred and seventeen participants responded to the TAS:O after reading mild, moderate, marked and severe organizational crisis scenarios. The overall Cronbach's alpha and split-half reliability were both .93. Confirmatory factor analysis revealed three factors, supporting the hypothesis that the TAS:O is comprised of three distinct factors (i.e., Affect, Behavior, and Cognition). An analysis of variance provided evidence that the TAS:O has the capacity to distinguish among mild, moderate, marked, and severe crises. Because this research is the first to evaluate the TAS:O, further studies are needed to strengthen confidence in the psychometric properties of this scale. 相似文献
6.
The effects of induction conditions on production of a soluble antitumor sFv in Escherichia coli 总被引:2,自引:0,他引:2
Jaymie R.Sawyer; Schlom Jeffrey; Kashmiri S. V. S. 《Protein engineering, design & selection : PEDS》1994,7(11):1401-1406
CC49 is a second generation monoclonal antibody(mAb) with highaffinity to a pancarcinoma antigen, TAG-72. A single-chain Fv(sFv)ofCC49 may have a role in managing human carcinomas. Most reportedsFvs have been expressed as insoluble products that must besolubilized and renatured. Soluble sFv expression is advantageousas activity can be assayed directly from the periplasmic fraction.Also, gene-level immunoconjugates may not be amenable to refoldingprotocols. Using a vector that carries the tac promoter andomp A signal, we have examined the effects of four variableson the expression and accumulation of soluble CC49 sFv: (i)linker sequence joining VL and VH, (ii) isopropylthio-ß-D-galactosideconcentration for induction, (iii) temprature, and (iv) theaddition of nonmetabolizable sugars to the medium. We have beenable to demonstrate, using rapidly prepared periplasmic extracts,that the yield of soluble sFv improves by the addition of 0.4Msucrose to the medium and by inducing expression with a verylow concentration of IPTG (0.020.03 mM). Under theseinduction conditions periplasmic extracts demonstrate increasedexpression of the sFv, as shown by the larger amount of a 27kDa band on SDS-polyacrylamide gel, and an increased abilityto inhibit binding of the mAb CC49 to immobilized tumor extracts. 相似文献
7.
This article describes a circuit model for infinitesimally thin inductive strips centered in homogeneous finline. The model is valid for 0.1 ≤ W/b ≤ 1.0, 0.01 ≤ T/a, and 0.4 ≤ b/a ≤ 0.5 when frequency is in the normal operating band for the rectangular waveguide shield. The error is less than 2.5%. 相似文献
8.
Bo Jiang Jeffrey L. Brown Jane Sheraton Nathalie Fortin Howard Bussey 《Yeast (Chichester, England)》1994,10(3):341-353
We have identified three yeast genes, KES1, HES1 and OSH1, whose products show homology to the human oxysterol binding protein (OSBP). Mutations in these genes resulted in pleiotropic sterol-related phenotypes. These include tryptophan-transport defects and nystatin resistance, shown by double and triple mutants. In addition, mutant combinations showed small but apparently cumulative reductions in membrane ergosterol levels. The three yeast genes are also functionally related as overexpression of HES1 or KES1 alleviated the tryptophan-transport defect in kes1Δ or osh1Δ mutants, respectively. Our study implicates this new yeast gene family in ergosterol synthesis and provides comparative evidence of a role for human OSBP in cholesterol synthesis. 相似文献
9.
Predd Joel Pfleeger Shari Lawrence Hunker Jeffrey Bulford Carla 《Security & Privacy, IEEE》2008,6(4):66-70
This column goes beyond previous insider analyses to identify a framework for a taxonomy of insider threats including both malicious and inadvertent actions by insiders that put organizations or their resources at some risk. The framework includes factors reflecting the organization, the individual, the information technology system, and the environment. 相似文献
10.
The most influential study of the person–environment (P–E) fit approach to stress was conducted by J. R. French et al (1982). Unfortunately, this study operationalized fit using various transformations of difference scores, thereby introducing numerous substantive and methodological problems. In the present study, the authors reanalyze data from French et al, using a procedure described by J. R. Edwards (in press) that avoids problems with difference scores and captures the underlying 3-dimensional relationship between environment, person, and strain. Results resolve ambiguities in the French et al findings and identify relationships between environment, person, and strain that, although consistent with P–E fit theory, cannot be adequately represented by fit measures such as those used by French et al. Implications for P–E fit research are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献