全文获取类型
收费全文 | 3837篇 |
免费 | 133篇 |
国内免费 | 30篇 |
专业分类
电工技术 | 67篇 |
综合类 | 7篇 |
化学工业 | 709篇 |
金属工艺 | 87篇 |
机械仪表 | 72篇 |
建筑科学 | 217篇 |
矿业工程 | 11篇 |
能源动力 | 148篇 |
轻工业 | 199篇 |
水利工程 | 8篇 |
石油天然气 | 17篇 |
无线电 | 461篇 |
一般工业技术 | 558篇 |
冶金工业 | 772篇 |
原子能技术 | 39篇 |
自动化技术 | 628篇 |
出版年
2023年 | 24篇 |
2022年 | 46篇 |
2021年 | 63篇 |
2020年 | 37篇 |
2019年 | 38篇 |
2018年 | 66篇 |
2017年 | 52篇 |
2016年 | 44篇 |
2015年 | 58篇 |
2014年 | 78篇 |
2013年 | 310篇 |
2012年 | 111篇 |
2011年 | 159篇 |
2010年 | 161篇 |
2009年 | 158篇 |
2008年 | 176篇 |
2007年 | 148篇 |
2006年 | 117篇 |
2005年 | 129篇 |
2004年 | 106篇 |
2003年 | 120篇 |
2002年 | 79篇 |
2001年 | 89篇 |
2000年 | 67篇 |
1999年 | 77篇 |
1998年 | 197篇 |
1997年 | 106篇 |
1996年 | 89篇 |
1995年 | 95篇 |
1994年 | 66篇 |
1993年 | 76篇 |
1992年 | 52篇 |
1991年 | 46篇 |
1990年 | 65篇 |
1989年 | 47篇 |
1988年 | 47篇 |
1987年 | 38篇 |
1986年 | 42篇 |
1985年 | 29篇 |
1984年 | 33篇 |
1983年 | 30篇 |
1982年 | 37篇 |
1981年 | 36篇 |
1980年 | 27篇 |
1979年 | 26篇 |
1978年 | 24篇 |
1977年 | 32篇 |
1976年 | 28篇 |
1975年 | 32篇 |
1973年 | 22篇 |
排序方式: 共有4000条查询结果,搜索用时 15 毫秒
1.
Cerebral microbleeds and cognitive decline in a hemodialysis patient: Case report and review of literature 下载免费PDF全文
Lin Li Mark Fisher Wei‐Ling Lau Hamid Moradi Alexander Cheung Gaby Thai Jason Handwerker Kamyar Kalantar‐Zadeh 《Hemodialysis international. International Symposium on Home Hemodialysis》2015,19(3):E1-E7
Cerebral microbleeds (CMBs) are small hemosiderin deposits indicative of prior cerebral microscopic hemorrhage and previously thought to be clinically silent. Recent population‐based cross‐sectional studies and prospective longitudinal cohort studies have revealed association between CMB and cognitive dysfunction. In the general population, CMBs are associated with age, hypertension, and cerebral amyloid angiopathy. In the chronic kidney disease (CKD) population, diminished estimated glomerular filtration rate has been found to be an independent risk factor for CMB, raising the possibility that a uremic milieu may predispose to microbleeds. In the end‐stage renal disease (ESRD) population on hemodialysis, the incidence of microbleeds is significantly higher compared with a control group without history of CKD or stroke. We present an ESRD patient on chronic hemodialysis with a history of gradual cognitive decline and progressive CMBs. Through this case and literature review, we illustrate the need to develop detection and prediction models to treat this frequent development in ESRD patients. 相似文献
2.
AI & SOCIETY - This paper is addressed to recent theoretical discussions of the Anthropocene, in particular Bernard Stiegler’s Neganthropocene (Open Universities Press, 2018), which... 相似文献
3.
4.
Given Hong Kong's special circumstances of small physical size, advanced infrastructure, and low shopping cost, a survey is designed under which supply-side problems in Internet business-to-consumer (B2C) e-commerce are indirectly revealed by responses on the demand side. Difficulties arising from the reluctance to answer questionnaires on the part of e-firms wary about trade and innovation secrets and their small number at the outset are thereby overcome. Survey data on demand-side obstacle factors in the form of perceived low e-shopping comparability, e-shopping inconvenience, e-transaction insecurity, and poor Internet privacy, together with orientation toward social interaction and low awareness on the part of consumers, translate into information on notionally matching supply-side hurdles. Regression analysis and hypothesis testing indicate statistical significance for the above hurdle factors in terms of impact on individual unwillingness to shop online. These results add to the inductive basis for future research into a general demand-supply theory of Internet B2C e-commerce and offer an empirically-grounded position against which the effects of later supply-side changes can be evaluated. Useful information also follows for engineer-managers seeking to compare marginal improvements in supply-side problems, particularly in the form of estimated substitution ratios. 相似文献
5.
The intent of a binomial effect size display (BESD) is to show "the [real-world] importance of [an] effect indexed by a correlation [r]" (R. Rosenthal, 1994, p. 242) by reexpressing this correlation as a success rate difference (SRD) (e.g., treatment group success rate - control group success rate). However, SRDs displayed in BESDs generally overestimate real-world SRDs implied by correlations of (a) dichotomous X and Y variables (φ coefficients), (b) dichotomous X and continuous Y variables (point-biserial coefficients [rphs]). and (c) continuous X and Y variables (rxys). Furthermore, overestimation biases are larger for rxys than for rphs. Differences in the sizes of biases linked to different correlations suggest that BESD SRDs reported for different correlations are not comparable. The stochastic difference index (N. Cliff, 1993: A. Vargha & H. D. Delaney, 2000) is recommended as an alternative to the BESD. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
6.
A revised methodology is described for research on metacognitive monitoring, especially judgments of learning (JOLs), to investigate psychological processing that previously has been only hypothetical and unobservable. During data collection a new stage of recall occurs just prior to the JOL, so that during data analysis the items can be partitioned into subcategories to measure the degree of JOL accuracy in ways that are more analytic than was previously possible. A weighted-average combinatorial rule allows the component measures of JOL accuracy to be combined into the usual overall measure of metacognitive accuracy. An example using the revised methodology offers a new explanation for the delayed-JOL effect, in which delayed JOLs are more accurate than immediate JOLs for predicting recall. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
7.
A 1 V switched-capacitor (SC) bandpass sigma-delta (/spl Sigma//spl Delta/) modulator is realized using a high-speed switched-opamp (SO) technique with a sampling frequency of up to 50 MHz, which is improved ten times more than prior 1 V SO designs and comparable to the performance of the state-of-the-art SC circuits that operate at much higher supply voltages. On the system level, a fast-settling double-sampling SC biquadratic filter architecture is proposed to achieve high-speed operation. A low-voltage double-sampling finite-gain-compensation technique is employed to realize a high-resolution /spl Sigma//spl Delta/ modulator using only low-DC-gain opamps to maximize the speed and to reduce power dissipation. On the circuit level, a fast-switching methodology is proposed for the design of the switchable opamps to achieve a switching frequency up to 50 MHz. Implemented in a 0.35-/spl mu/m CMOS process (V/sub TP/=0.82 V and V/sub TN/=0.65 V) and at 1 V supply, the modulator achieves a measured peak signal-to-noise-and-distortion ratio (SNDR) of 42.3 dB at 10.7 MHz with a signal bandwidth of 200 kHz, while dissipating 12 mW and occupying a chip area of 1.3 mm/sup 2/. 相似文献
8.
John C. Hart Gordon W. Lescinsky Daniel J. Sandin Thomas A. DeFanti Louis H. Kauffman 《The Visual computer》1993,9(7):346-355
The pipelined architecture and parallel organization of the AT&T Pixel Machine image computer are described and demonstrated with applications for the visualization of multidimensional fractals, particularly linear fractals and quaternion/ stacked Julia sets. Techniques for pushing the Pixel Machine to its peak abilities are described and apply to more recent parallel image computers as well. 相似文献
9.
Oliveira M. Dart-Mao Cheung C. Al-Zayed A. Chio I.-F.F. Swisher R.R. Lecuyer F. DeLisio M.P. 《Antennas and Propagation, IEEE Transactions on》2002,50(5):698-702
Grid-mixer arrays can achieve high linearity and dynamic range through quasi-optical power combining. We present a 100-element single-ended diode grid mixer operating at 2.45 GHz. Each element incorporates two diodes in series. We measure an input third-order intercept of 11 W (40.5 dBm), and output third-order intercept of 3.4 W (35.4 dBm), and an associated conversion loss of 5.1 dB. The power-handling capability of the array is 100 times larger than that of a microstrip mixer using a single element. The local oscillator (LO) drive requirement for the entire array is 1.4 W (31.6 dBm). The angular dependence of the array's IF power is also presented and is in agreement with theory 相似文献
10.
Y. K. Cheung W. G. Jin O. C. Zienkiewicz 《International journal for numerical methods in engineering》1991,32(1):63-78
The application of the Trefftz method for calculating wave forces on offshore structures is presented. Indirect and direct formulations using complete and non-singular systems of Trefftz functions for the Helmholtz equation are posed in this paper. An effective technique using different interpolation functions for the velocity potential and wave force are suggested to improve the computational accuracy of the wave force. The numerical examples show that the present method is highly efficient and accurate. 相似文献