全文获取类型
收费全文 | 1555篇 |
免费 | 44篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 25篇 |
化学工业 | 254篇 |
金属工艺 | 23篇 |
机械仪表 | 21篇 |
建筑科学 | 63篇 |
矿业工程 | 23篇 |
能源动力 | 47篇 |
轻工业 | 111篇 |
水利工程 | 13篇 |
石油天然气 | 6篇 |
武器工业 | 1篇 |
无线电 | 119篇 |
一般工业技术 | 182篇 |
冶金工业 | 432篇 |
原子能技术 | 9篇 |
自动化技术 | 274篇 |
出版年
2022年 | 11篇 |
2021年 | 28篇 |
2019年 | 15篇 |
2018年 | 27篇 |
2017年 | 25篇 |
2016年 | 23篇 |
2015年 | 13篇 |
2014年 | 37篇 |
2013年 | 111篇 |
2012年 | 41篇 |
2011年 | 71篇 |
2010年 | 56篇 |
2009年 | 55篇 |
2008年 | 46篇 |
2007年 | 58篇 |
2006年 | 46篇 |
2005年 | 54篇 |
2004年 | 42篇 |
2003年 | 49篇 |
2002年 | 42篇 |
2001年 | 37篇 |
2000年 | 19篇 |
1999年 | 31篇 |
1998年 | 63篇 |
1997年 | 36篇 |
1996年 | 30篇 |
1995年 | 34篇 |
1994年 | 28篇 |
1993年 | 24篇 |
1992年 | 21篇 |
1991年 | 12篇 |
1990年 | 19篇 |
1989年 | 23篇 |
1988年 | 17篇 |
1987年 | 17篇 |
1986年 | 27篇 |
1985年 | 27篇 |
1984年 | 27篇 |
1983年 | 17篇 |
1982年 | 22篇 |
1981年 | 23篇 |
1980年 | 22篇 |
1979年 | 21篇 |
1978年 | 11篇 |
1977年 | 19篇 |
1976年 | 20篇 |
1975年 | 12篇 |
1974年 | 11篇 |
1973年 | 12篇 |
1972年 | 13篇 |
排序方式: 共有1603条查询结果,搜索用时 15 毫秒
1.
Yang Hu Stephanie M. Sjoberg Chunpen Chen Amber L. Hauvermale Craig F. Morris Stephen R. Delwiche Ashley E. Cannon Camille M. Steber Zhiwu Zhang 《Comprehensive Reviews in Food Science and Food Safety》2022,21(3):2105-2117
This review examines the application, limitations, and potential alternatives to the Hagberg–Perten falling number (FN) method used in the global wheat industry for detecting the risk of poor end-product quality mainly due to starch degradation by the enzyme α-amylase. By viscometry, the FN test indirectly detects the presence of α-amylase, the primary enzyme that digests starch. Elevated α-amylase results in low FN and damages wheat product quality resulting in cakes that fall, and sticky bread and noodles. Low FN can occur from preharvest sprouting (PHS) and late maturity α-amylase (LMA). Moist or rainy conditions before harvest cause PHS on the mother plant. Continuously cool or fluctuating temperatures during the grain filling stage cause LMA. Due to the expression of additional hydrolytic enzymes, PHS has a stronger negative impact than LMA. Wheat grain with low FN/high α-amylase results in serious losses for farmers, traders, millers, and bakers worldwide. Although blending of low FN grain with sound wheat may be used as a means of moving affected grain through the marketplace, care must be taken to avoid grain lots from falling below contract-specified FN. A large amount of sound wheat can be ruined if mixed with a small amount of sprouted wheat. The FN method is widely employed to detect α-amylase after harvest. However, it has several limitations, including sampling variability, high cost, labor intensiveness, the destructive nature of the test, and an inability to differentiate between LMA and PHS. Faster, cheaper, and more accurate alternatives could improve breeding for resistance to PHS and LMA and could preserve the value of wheat grain by avoiding inadvertent mixing of high- and low-FN grain by enabling testing at more stages of the value stream including at harvest, delivery, transport, storage, and milling. Alternatives to the FN method explored here include the Rapid Visco Analyzer, enzyme assays, immunoassays, near-infrared spectroscopy, and hyperspectral imaging. 相似文献
2.
The solvent-dependent polymorphism of the active pharmaceutical ingredient (API) carbamazepine is interpreted from calculations of the solid-state and API-solvent intermolecular interactions. These simulations suggested that apolar solute-solute interactions could be disrupted by apolar solvents. In contrast, the polar solute-solute interactions were found to be easily disrupted by polar and protic solvents. This is consistent with experimental observations that the crystallization of the metastable form II is more dominant in apolar solvents. The Mercury program remains the gold standard in terms of usability; however, further expansion into more complex simulation techniques could make this package of even greater use in pharmaceutical manufacturing workflows. 相似文献
3.
We demonstrate that alkali-halide salts, particularly potassium bromide, can reduce the photothermal emission (PTE) from single walled carbon nanotubes (SWNT). PTE is a prominent spectral feature in Raman spectroscopy when a near infrared laser is used to analyze a dark colored sample. We subsequently show that trapping salts inside SWNT and coating SWNT with the salt has a more pronounced impact on not only reducing PTE, but also enhancing the intensity of the Raman spectral features. The effect, which we have called nanotube enhanced Raman spectroscopy (NERS), has differences and similarities to the widely studied surface enhanced Raman spectroscopy (SERS). 相似文献
4.
In response to an interpretation made by Moore and Akgerman of data taken from a recent publication, previously unexplainable phenomena are accounted for, based on new experimental results. These relate to a thermodynamic equilibrium reaction involving saturation of aromatic hydrocarbons in synthetic crude middle distillates. 相似文献
5.
Ronald R. Delyser Sheila S. Thompson Jerry Edelstein Corinne Lengsfeld Albert J. Rosa Paul J. Rullkoetter Robert Whitman Margaret Whitt 《工程教育杂志》2003,92(3):269-273
A team of faculty members at the University of Denver changed the learning environment in key courses in the Department of Engineering from predominately teacher centered to student centered. Through this funded project new grading methods were implemented, classrooms were renovated and wired with studio layouts to facilitate learning, the Engineering Circuits Laboratory was rewired and instrumented for automated data acquisition and reporting, and two new pedagogical approaches were developed. At the onset of the project, six goals were established related to student learning. The introduction of industry standard hardware and software provided students with unprecedented hands‐on experience and project related activities stimulated faculty innovations in other current and future courses. Assessment results indicate that the new grading system improved the clarity of expectations for students before assignments were given resulting in increased reported motivation for learning in many courses. Even though course GPAs did not always reflect higher achievement on graded work, faculty members firmly believe that deeper understanding was achieved because more complex material was assimilated. 相似文献
6.
Nonlinear model predictive control with polytopic invariant sets 总被引:1,自引:0,他引:1
Ellipsoidal invariant sets have been widely used as target sets in model predictive control (MPC). These sets can be computed by constructing appropriate linear difference inclusions together with additional constraints to ensure that the ellipsoid lies within a given inclusion polytope. The choice of inclusion polytope has a significant effect on the size of the target ellipsoid, but the optimal inclusion polytope cannot in general be computed systematically. This paper shows that use of polytopic invariant sets overcomes this difficulty, allowing larger stabilizable sets without loss of performance. In the interests of online efficiency, consideration is focused on interpolation-based MPC. 相似文献
7.
Chemometrics has enjoyed tremendous success in the areas related to calibration of spectrometers and spectroscopy-based measurements. These chemometric-based spectrometers have been widely applied for process monitoring and quality assurance. However, chemometrics has the potential to revolutionize the very intellectual roots of problem solving. Are there barriers to a more rapid proliferation of chemometric-based thinking, particularly in industry? What are the potential effects of chemometrics technology and the New Network Economy (NNE) working in concert? Who will be the winners in the race for faster, better, cheaper systems and products? These questions are reviewed in terms of the principles of the NNE and in the promise of chemometrics for industry. What then is the state of multivariate thinking in industry? Several powerful principles are derived from an evaluation of the NNE and chemometrics which could allow chemometrics to proliferate much more rapidly as a key general problem-solving tool. 相似文献
8.
9.
AH Bosworth MK Williams KA Albrecht R Kwiatkowski J Beynon TR Hankinson CW Ronson F Cannon TJ Wacek EW Triplett 《Canadian Metallurgical Quarterly》1994,60(10):3815-3832
The construction of rhizobial strains which increase plant biomass under controlled conditions has been previously reported. However, there is no evidence that these newly constructed strains increase legume yield under agricultural conditions. This work tested the hypothesis that carefully manipulating expression of additional copies of nifA and dctABD in strains of Rhizobium meliloti would increase alfalfa yield in the field. The rationale for this hypothesis is based on the positive regulatory role that nifA plays in the expression of the nif regulon and the fact that a supply of dicarboxylic acids from the plant is required as a carbon and energy source for nitrogen fixation by the Rhizobium bacteroids in the nodule. These recombinant strains, as well as the wild-type strains from which they were derived, are ideal tools to examine the effects of modifying or increasing the expression of these genes on alfalfa biomass. The experimental design comprised seven recombinant strains, two wild-type strains, and an uninoculated control. Each treatment was replicated eight times and was conducted at four field sites in Wisconsin. Recombinant strain RMBPC-2, which has an additional copy of both nifA and dctABD, increased alfalfa biomass by 12.9% compared with the yield with the wild-type strain RMBPC and 17.9% over that in the uninoculated control plot at the site where soil nitrogen and organic matter content was lowest. These increases were statistically significant at the 5% confidence interval for each of the three harvests made during the growing season. Strain RMBPC-2 did increase alfalfa biomass at the Hancock site; however, no other significant increases or decreases in alfalfa biomass were observed with the seven other recombinant strains at that site. At three sites where this experiment was conducted, either native rhizobial populations or soil nitrogen concentrations were high. At these sites, none of the recombinant strains affected yield. We conclude that RMBPC -2 can increase alfalfa yields under field conditions of nitrogen limitation, low endogenous rhizobial competitors, and sufficient moisture. 相似文献
10.
Jerry Loraine 《电子技术》2006,33(2):8-11
预计到2009年,大部分移动终端系统都将配备各式各样的无线存取技术,用以处理多媒体信息。要为这种发展趋势作好准备,业界就必须从现在开始积极创新无线频射(RF)设计。 相似文献