全文获取类型
收费全文 | 987篇 |
免费 | 18篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 30篇 |
综合类 | 1篇 |
化学工业 | 98篇 |
金属工艺 | 30篇 |
机械仪表 | 21篇 |
建筑科学 | 20篇 |
矿业工程 | 4篇 |
能源动力 | 15篇 |
轻工业 | 40篇 |
水利工程 | 4篇 |
石油天然气 | 2篇 |
无线电 | 117篇 |
一般工业技术 | 81篇 |
冶金工业 | 413篇 |
原子能技术 | 15篇 |
自动化技术 | 120篇 |
出版年
2021年 | 5篇 |
2018年 | 4篇 |
2017年 | 12篇 |
2016年 | 12篇 |
2015年 | 11篇 |
2014年 | 13篇 |
2013年 | 31篇 |
2012年 | 13篇 |
2011年 | 15篇 |
2010年 | 26篇 |
2009年 | 22篇 |
2008年 | 19篇 |
2007年 | 11篇 |
2006年 | 22篇 |
2005年 | 19篇 |
2004年 | 30篇 |
2003年 | 33篇 |
2002年 | 18篇 |
2001年 | 17篇 |
2000年 | 18篇 |
1999年 | 13篇 |
1998年 | 89篇 |
1997年 | 66篇 |
1996年 | 52篇 |
1995年 | 40篇 |
1994年 | 31篇 |
1993年 | 35篇 |
1992年 | 28篇 |
1991年 | 26篇 |
1990年 | 21篇 |
1989年 | 14篇 |
1988年 | 21篇 |
1987年 | 10篇 |
1986年 | 9篇 |
1985年 | 9篇 |
1984年 | 6篇 |
1983年 | 9篇 |
1982年 | 5篇 |
1981年 | 10篇 |
1980年 | 10篇 |
1979年 | 11篇 |
1978年 | 8篇 |
1977年 | 35篇 |
1976年 | 53篇 |
1975年 | 5篇 |
1973年 | 3篇 |
1971年 | 3篇 |
1970年 | 3篇 |
1969年 | 5篇 |
1958年 | 3篇 |
排序方式: 共有1011条查询结果,搜索用时 0 毫秒
81.
In Situ Measurement of Nonlinear Shear Modulus of Silty Soil 总被引:1,自引:0,他引:1
A new field test method to evaluate in situ nonlinear shear modulus of soils was developed. The method utilizes a drilled shaft as a cylindrical, axisymmetric source for shear loading of soil at depth. The applicability of the test method was studied by conducting small-scale, prototype experiments at a “calibration” field site in Austin, Texas. Numerous conventional in situ and laboratory measurements were performed to characterize the soil at the field site. The “small-scale” nature of the tests involved using a 381?mm (15?in.) diameter, 3.7?m (12?ft) long drilled shaft. Experimental results from this field study provided an opportunity to compare laboratory and field measurements of the G?log?γ and G/Gmax?log?γ curves. This comparison was used to investigate the accuracy of common procedures relating field and laboratory modulus reduction curves. Nonlinear modulus measurements were performed at depths of 1.8?to?2.1?m (6?to?7?ft) in a silt (ML). The field G/Gmax?log?γ curve for this soil at low confining pressures are in general agreement with the laboratory curve from an intact specimen as well as empirical curves. 相似文献
82.
Clayton J. Clark II Michael D. Annable P. S. C. Rao 《Canadian Metallurgical Quarterly》2000,126(11):1033-1038
Remediation of source zones at sites contaminated with dense non-aqueous-phase liquids using aggressive in situ flushing technologies, such as the addition of chemical additives known as cosolvents, have been implemented and successfully demonstrated in recent field tests. However, treatment of the waste fluids generated from such cleanup technologies has not received much attention. The purpose of this laboratory research was to evaluate the feasibility of using sonication as a method for treating waste fluids produced during in situ alcohol flushing at a site contaminated with a dense non-aqueous-phase liquid. Experimental results showed that sonochemical destruction of perchloroethylene (PCE) followed pseudo first-order kinetics and that increasing ethanol cosolvent percentages in the aqueous effluent resulted in decreasing degradation rates of PCE in solution. The energy efficiency (G = degradation∕energy input) of the sonication treatment also decreased as the ethanol volume fraction increased. Overall, sonication was seen to degrade PCE in aqueous solutions, becoming less effective as the cosolvent fraction increased. 相似文献
83.
The response of a wide range of metals under the action of an applied stress and in environments spanning an entire range of aggressiveness, from the very inert to aggressive has been the subject of several investigations. Most of these studies have focused on mechanisms governing fatigue crack propagation and little attention has been paid to the effect of environment on fatigue crack initiation. A comprehensive understanding of the influence of aqueous environments has been hampered by the complexity of the problem, the difficulties in understanding the various micromechanisms governing crack initiation and crack propagation and by an absence of a truly interdisciplinary attack of the problem. In this paper, several of the fatigue crack initiation models are presented and the micromechanisms governing fatigue crack initiation are examined. The various processes that control the phenomenon of cracking including aqueous environment enhanced fatigue crack growth are also highlighted in this review. 相似文献
84.
85.
Kathryn M. L. Taylor-Pashow Thomas B. Peters Fernando F. Fondeur Aaron L. Washington II David T. Hobbs 《分离科学与技术》2015,50(18):2853-2865
The Defense Waste Processing Facility (DWPF), responsible for vitrifying high-level waste (HLW) at the Savannah River Site (SRS), is planning to introduce glycolic acid as a reductant during chemical conditioning of the waste prior to vitrification. A portion of this glycolic acid may be recycled back to the tank farm as sodium glycolate. Since glycolate can serve as a complexing agent for a variety of metallic ions, recent studies were performed to examine the effect of glycolate on the removal of Sr and actinides by monosodium titanate (MST) and modified MST (mMST) and the separation of Cs by the caustic-side solvent extraction (CSSX) process. 相似文献
86.
John M. Davis Ian A. Gravagne Robert J. Marks II 《Circuits, Systems, and Signal Processing》2010,29(6):1141-1165
The convergence of Laplace transforms on time scales is generalized to the bilateral case. The bilateral Laplace transform
of a signal on a time scale subsumes the continuous time bilateral Laplace transform, and the discrete time bilateral z-transform as special cases. As in the unilateral case, the regions of convergence (ROCs) time scale Laplace transforms are
determined by the time scale’s graininess. ROCs for the bilateral Laplace transforms of double sided time scale exponentials
are determined by two modified Hilger circles. The ROC is the intersection of points external to modified Hilger circle determined
by behavior for positive time and the points internal to the second modified Hilger circle determined by negative time. Since
graininess lies between zero and infinity, there can exist conservative ROCs applicable for all time scales. For continuous
time (ℝ) bilateral transforms, the circle radii become infinite and results in the familiar ROC between two lines parallel
to the imaginary z axis. Likewise, on ℤ, the ROC is an annulus. For signals on time scales bounded by double sided exponentials, the ROCs are
at least that of the double sided exponential. The Laplace transform is used to define the box minus shift through which time scale convolution can be defined. Generalizations of familiar properties of signals on ℝ and ℤ include
identification of the identity convolution operator, the derivative theorem, and characterizations of wide sense stationary
stochastic processes for an arbitrary time scales including autocorrelation and power spectral density expressions. 相似文献
87.
Phosphorous Levels in Peeled and Deveined Shrimp Treated with Sodium Tripolyphosphate 总被引:1,自引:0,他引:1
VICKIE TENHET GUNNAR FINNE RANZELL NICKELSON II DON TOLODAY 《Journal of food science》1981,46(2):350-352
Using volumetric and spectrophotometric methods for the determination of phosphorous, untreated shrimp were shown to have high and variable phosphorous content. When peeled and deveined shrimp were treated with 0.5% and 1.0% sodium tripolyphosphate (STP) solutions, the STP uptake was shown to be low. At these low treatment concentrations the phosphorous content in the treated shrimp did not exceed the range of natural phosphorous found in untreated shrimp. When higher treatment concentrations were used, treated thrimp could be identified. The stability of STP in treated shrimp during frozen storage was investigated using a P32 STP isotope. After 2 wk of frozen storage at –26°C only 12% of the total activity could be attributed to STP. At the same time, pyrophosphate was present at a level of 25% and orthophosphate at 27%. During further frozen storage, the STP concentration remained at approxinately 12%, pyrophosphate dropped down to as low as 2% while orthophosphate gradually increased reaching 45% of total activity at the end of 10 wk storage period. 相似文献
88.
Alvin C. Bach II David W. Cochran 《Journal of The Association for Laboratory Automation》2002,7(6):103-107
We have designed and implemented an automated walkup NMR computer application for use by synthetic chemists. The Wyeth Walkup NMR (WWNMR) application is a TCL/TK graphical user interface front-end to Varian's NMR automation routines. The key feature of WWNMR is that the chemists are isolated from the spectrometer's control program (VNMR) and only enter information to WWNMR windows for a sample to be run. The resulting data can be printed out on paper, or stored on disk for easy access by all users at their desktops. Proton and carbon NMR experiments are available. An overview of the WWNMR application will be presented. 相似文献
89.
Ionov P. A. Senin P. V. Zemskov A. M. Stolyarov A. V. P’yanzov S. V. 《Russian Engineering Research》2021,41(10):971-973
Russian Engineering Research - An approach is outlined to selecting conditions of electrical discharge machining such that coatings with the required functional properties are formed on the working... 相似文献
90.