全文获取类型
收费全文 | 1496篇 |
免费 | 79篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 33篇 |
综合类 | 4篇 |
化学工业 | 374篇 |
金属工艺 | 35篇 |
机械仪表 | 23篇 |
建筑科学 | 56篇 |
矿业工程 | 37篇 |
能源动力 | 33篇 |
轻工业 | 93篇 |
水利工程 | 25篇 |
石油天然气 | 4篇 |
无线电 | 106篇 |
一般工业技术 | 267篇 |
冶金工业 | 316篇 |
原子能技术 | 11篇 |
自动化技术 | 162篇 |
出版年
2023年 | 12篇 |
2022年 | 19篇 |
2021年 | 38篇 |
2020年 | 20篇 |
2019年 | 19篇 |
2018年 | 35篇 |
2017年 | 31篇 |
2016年 | 37篇 |
2015年 | 41篇 |
2014年 | 44篇 |
2013年 | 62篇 |
2012年 | 76篇 |
2011年 | 85篇 |
2010年 | 68篇 |
2009年 | 49篇 |
2008年 | 66篇 |
2007年 | 54篇 |
2006年 | 55篇 |
2005年 | 39篇 |
2004年 | 37篇 |
2003年 | 37篇 |
2002年 | 23篇 |
2001年 | 29篇 |
2000年 | 23篇 |
1999年 | 34篇 |
1998年 | 97篇 |
1997年 | 54篇 |
1996年 | 49篇 |
1995年 | 31篇 |
1994年 | 24篇 |
1993年 | 23篇 |
1992年 | 18篇 |
1991年 | 21篇 |
1990年 | 11篇 |
1989年 | 10篇 |
1988年 | 13篇 |
1987年 | 10篇 |
1986年 | 10篇 |
1985年 | 16篇 |
1984年 | 10篇 |
1983年 | 9篇 |
1982年 | 13篇 |
1981年 | 13篇 |
1980年 | 14篇 |
1979年 | 12篇 |
1977年 | 17篇 |
1976年 | 18篇 |
1975年 | 8篇 |
1970年 | 7篇 |
1920年 | 4篇 |
排序方式: 共有1579条查询结果,搜索用时 15 毫秒
1.
Many media processing applications create a load that varies significantly over time. Hence, if such an application is assigned a lower processing-time budget than needed in its worst-case load situation, deadline misses are likely to occur. This problem can be dealt with by designing media processing applications in a scalable fashion. A scalable media processing application can run in multiple qualities, leading to correspondingly different resource demands. The problem we consider is to find an accompanying quality control strategy, which minimizes both the number of deadline misses and the number of quality changes, while maximizing the quality of processing. We present an initial approach to the above problem by modeling it as a Markov decision process (MDP). Our model is based on measuring relative progress at milestones. Solving the MDP results in a quality control strategy that can be applied during runtime with only little overhead. We evaluate our approach by means of a practical example, which concerns a scalable MPEG-2 decoder. 相似文献
2.
3.
4.
Assessments of sewer performance are usually based on a single computation of CSO (combined sewer overflow) volumes using a time series of rainfall as system loads. A shortcoming of this method is that uncertainties in knowledge of sewer system dimensions are not taken into account. Moreover, sewer models are rarely calibrated. This paper presents the impacts of database errors and model calibration on return periods of calculated CSO volumes. The impact of uncertainties is illustrated with two examples. Variability of calculated CSO volumes is estimated using Monte Carlo simulations. The results show that calculated CSO volumes vary considerably due to database errors, especially uncertain dimensions of the catchment area. Furthermore, event-based calibration of a sewer model does not result in more reliable predictions because the calibrated parameters have low portability. However, it enables removal of database errors harmonising model predictions and 'reality'. 相似文献
5.
The testing and quality assurance of the Motif 1.0 graphical user-interface software are described. The testing goals, which fell into three general categories (code coverage, defect-density, and defect-arrival rate), and a deliverable formal test suite are examined. The three phases of the testing process-evaluation, test development, and regression testing-and the tools used in testing are discussed 相似文献
6.
OBJECTIVE: To evaluate the efficacy of terazosin, an alpha-blocker, for the treatment of idiopathic oligozoospermia. PATIENTS AND METHODS: Thirty couples with infertility whose only detectable abnormality was male idiopathic subfertility entered the study. The diagnosis of idiopathic subfertility in all males studied, aged 26 to 38 years (mean 28.2 years), was confirmed after exclusion of any iatrogenic, systemic, congenital, infectious, autoimmune or endocrinological cause. In order to start with a baseline value before the study, at least three semen samples were evaluated in accordance with the WHO recommendation. Before initiation of treatment, blood samples were drawn for measurement of FSH, LH, testosterone, prolactin, dihydrotestosterone, and estradiol. Fifteen randomly selected patients (Group A) received 2 mg/d of alpha-blocker (terazosin), while another 15 (Group B) were administered an identically packed placebo tablet. Both groups received therapy for 6 months. RESULTS: The mean seminal volume changed insignificantly between the two groups (4.15 +/- 1.95 vs. 4.10 +/- 1.95). There was a statistically significant increase of the sperm concentration in patients who received the alpha-blocker compared to those receiving placebo (24.76 +/- 9.45 vs. 13.15 +/- 11.55 millions/mL; P < .001). No improvement of the mean percentage of abnormal spermatozoa was observed in the treated patients, nor a statistically significant difference of sperm motility in the treated group compared to the placebo group. Side effects were not observed in the patients receiving terazosin treatment, or were so minimal that therapy was continued. The pregnancy rates did not differ between the two groups to a statistically significant degree. CONCLUSION: The administration of terazosin to patients with idiopathic oligozoospermia has a demonstrably positive effect, especially on sperm concentration. 相似文献
7.
DR Gehlert DT Stephenson DA Schober K Rash JA Clemens 《Canadian Metallurgical Quarterly》1997,31(5):705-713
Peripheral benzodiazepine receptors (PBRs) are expressed in a variety of tissues but are normally found at low levels in the brain. Following various types of nerve injury, a reactive gliosis results that exhibits a high expression of this receptor. To further characterize the expression of PBRs following neuronal injury, we evaluated PBR expression in the facial nucleus following facial nerve axotomy (FNA). Injury to a peripheral nerve results in a complex series of metabolic and morphological changes around the injured neuron. Transections of the facial nerve results in a rapid activation of both astrocytes and microglia around axotomized motor neurons. FNA resulted in an increase in the staining for both astrocytes (glial fibrillary acidic protein) and activated microglia (OX42). There was also a reduction in synaptic contacts with the motor nucleus as evidenced by reduced staining for the synaptic marker, synaptophysin. In sections labeled with [3H]-PK11195, the subsequent autoradiograms displayed marked increases in the labeling for PBRs. This increase was observed at 5, 7 and 10 days after nerve transection. The increase was primarily in the level of expression (Bmax), with no change in the affinity of the ligand (Kd). The increase in PBR expression after FNA supports the hypothesis that PBRs can be used as a sensitive marker for CNS injury. 相似文献
8.
R Albrecht TC Awes C Baktash P Beckmann F Berger R Bock G Claesson G Clewing L Dragon A Eklund RL Ferguson A Franz S Garpman R Glasow HA Gustafsson HH Gutbrod J Idh P Jacobs K Kampert BW Kolb P Kristiansson IY Lee H Loehner I Lund FE Obenshain A Oskarsson I Otterlund T Peitzmann S Persson F Plasil AM Poskanzer M Purschke H Ritter S Saini R Santo HR Schmidt T Siemiarczuk SP Sorensen E Stenlund ML Tincknell GR Young 《Canadian Metallurgical Quarterly》1991,44(6):2736-2752
9.
10.
Chandrasekhar S. Lunardi L.M. Gnauck A.H. Ritter D. Hamm R.A. Panish M.B. Qua G.J. 《Electronics letters》1992,28(5):466-468
Metal organic molecular beam epitaxy (MOMBE) was successfully used for the first time to realise a high speed monolithic photoreceiver. Incorporating an InGaAs pin photodetector followed by a transimpedance preamplifier circuit implemented with InP/InGaAs heterojunction bipolar transistors (HBTs), the OEIC photoreceiver had a bandwidth of 6 GHz and a midband transimpedance of 350 Omega . In a system experiment performed at 10 Gbit/s, the receiver exhibited a sensitivity of -15.5 dBm for a bit error rate of 10/sup -9/ at a wavelength of 1.53 mu m. This is the first demonstration of operation of a long wavelength OEIC photoreceiver at this speed.<> 相似文献