全文获取类型
收费全文 | 4193篇 |
免费 | 158篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 57篇 |
综合类 | 13篇 |
化学工业 | 702篇 |
金属工艺 | 79篇 |
机械仪表 | 73篇 |
建筑科学 | 272篇 |
矿业工程 | 14篇 |
能源动力 | 100篇 |
轻工业 | 353篇 |
水利工程 | 35篇 |
石油天然气 | 13篇 |
无线电 | 437篇 |
一般工业技术 | 668篇 |
冶金工业 | 827篇 |
原子能技术 | 25篇 |
自动化技术 | 688篇 |
出版年
2023年 | 47篇 |
2022年 | 67篇 |
2021年 | 99篇 |
2020年 | 67篇 |
2019年 | 88篇 |
2018年 | 99篇 |
2017年 | 89篇 |
2016年 | 125篇 |
2015年 | 110篇 |
2014年 | 139篇 |
2013年 | 239篇 |
2012年 | 183篇 |
2011年 | 239篇 |
2010年 | 208篇 |
2009年 | 159篇 |
2008年 | 196篇 |
2007年 | 170篇 |
2006年 | 166篇 |
2005年 | 157篇 |
2004年 | 102篇 |
2003年 | 104篇 |
2002年 | 95篇 |
2001年 | 84篇 |
2000年 | 60篇 |
1999年 | 69篇 |
1998年 | 181篇 |
1997年 | 120篇 |
1996年 | 105篇 |
1995年 | 67篇 |
1994年 | 59篇 |
1993年 | 53篇 |
1992年 | 40篇 |
1991年 | 36篇 |
1990年 | 43篇 |
1989年 | 50篇 |
1988年 | 35篇 |
1987年 | 25篇 |
1986年 | 22篇 |
1985年 | 23篇 |
1984年 | 17篇 |
1983年 | 20篇 |
1982年 | 15篇 |
1981年 | 18篇 |
1980年 | 17篇 |
1979年 | 16篇 |
1978年 | 24篇 |
1977年 | 15篇 |
1976年 | 26篇 |
1971年 | 19篇 |
1970年 | 14篇 |
排序方式: 共有4356条查询结果,搜索用时 15 毫秒
1.
W. Shang B. Robrahn F. Golding M. H. J. Koch 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2004,530(3):513-520
A data acquisition system for time resolved X-ray scattering experiments using linear, quadrant or area gas proportional detectors with delay line readout based on commercially available hardware (National Instruments) is described. The system can easily be configured for recording data from point detectors (e.g. photomultipliers and photodiodes) and/or ancillary data only. Applications involving measurements with two different types of time to digital converters illustrate the features and performances of the system. 相似文献
2.
Terahertz characterisation of building materials 总被引:1,自引:0,他引:1
Piesiewicz R. Kleine-Ostmann T. Krumbholz N. Mittleman D. Koch M. Kurner T. 《Electronics letters》2005,41(18):1002-1004
To obtain realistic models for propagation channels in future pico-cellular indoor terahertz communication systems it is necessary to know the reflective properties of building materials found in a typical office environment. The angular dependent reflection coefficients of different building materials were determined using terahertz time-domain spectroscopy in transmission geometry and Fresnel's equations. This approach is more efficient than a set of measurements in reflection geometry for different angles. Verification of the method with a set of such reflection measurements shows an excellent agreement. 相似文献
3.
4.
5.
BACKGROUND: Diabetic patients with end-stage renal failure (ESRD) have a high cardiovascular morbidity and mortality. The underlying mechanisms are not completely elucidated. The aim of our study was to define predictors of death in diabetic patients with end-stage renal disease. PATIENTS AND METHODS: We performed a prospective study in 35 dialysis centres in Germany between 1985 and 1994. To evaluate predictors and risk factors in this population we examined 412 diabetic patients at the time of admission to dialysis treatment (peritoneal dialysis (PD) or haemodialysis (HD)). Classification of the type of diabetes was done according the criteria of the National Diabetes Data Group [1,2]. Items assessed at the time of admission were coronary artery disease (CAD), peripheral occlusive disease (POD), and stroke. CAD was defined as a history of myocardial infarction with the corresponding changes in the ECG or luminal narrowing by more than 50% in at least one coronary artery upon coronarangiography; POD was defined as claudication and/or brachial-tibial ratio (BTR) less than 0.9 or a history of amputation. Assessment of the nutritional state comprised body mass index, skinfold thickness of the upper arm and lateral thorax area, and urea concentration. Cholesterol, HDL, LDL, apolipoprotein A (ApoA-I) and B (ApoB), triglycerides, lipoprotein(a) (Lp(a)), and fibrinogen were measured. As an index of disturbed cardiac innervation beat-to-beat variation was measured. Outcome measurements were causes of death (i.e. cardiac and non-cardiac) and time of survival. RESULTS: One hundred and eighty of 412 (44%) patients died during the observation period. Patients who died were older (61 +/- 12 versus 53 +/- 15 years P < 0.0001), had lower skin fold thickness (13.1 +/- 6.0 versus 15.1 +/- 7.3 mm P < 0.04), lower ApoA-I (100 +/- 35 versus 111 +/- 32 mg/dl P < 0.005) and higher fibrinogen (515 +/- 146 versus 451 +/- 155 mg/dl P < 0.02). Type II diabetic patients had a lower mean survival time than type I (34 versus 66 months P < 0.0006). The mode of renal replacement therapy (PD or HD) had no adverse effect on survival time. Survivors less frequently had a history of CAD, POD and stroke than non-survivors. In multivariate analysis ApoA-I, fibrinogen, age and stroke were independent predictors of cardiac and non-cardiac death in diabetic patients with end-stage renal failure. Lipid values and nutritional state did not independently predict the overall and cardiovascular mortality. CONCLUSION: This study in dialysed diabetic patients identifies several predictors of death, some of which are susceptible to intervention. 相似文献
6.
GB Lipford T Sparwasser M Bauer S Zimmermann ES Koch K Heeg H Wagner 《Canadian Metallurgical Quarterly》1997,27(12):3420-3426
Certain bacterial immunostimulatory (i.s.) DNA sequences containing unmethylated CpG motifs stimulate antigen-presenting cells (APC) to express a full complement of costimulatory molecules and to produce cytokines including interleukin (IL)-12 and tumor necrosis factor (TNF)-alpha. While IL-12 is key to their T helper cell (Th)1-promoting adjuvant activity, secretion of toxic levels of TNF-alpha is harmful in that it promotes toxic shock. Given the beneficial as well as harmful consequences of i.s. DNA, we investigated the possibility of identifying DNA sequences, i.e. CpG oligodeoxynucleotides (ODN) which differentially activate IL-12 versus TNF-alpha cytokine production in APC. Here, we describe an i.s. DNA sequence with these characteristics. While its potential to induce IL-12 is preserved, its ability to trigger TNF-alpha release is strongly curtailed both in vitro and in vivo. I.s. DNA could be segregated into lethal and non-lethal in a mouse toxic shock model. The non-toxic i.s. DNA was useful as an adjuvant, thus allowing cytotoxic T cell responses to the soluble protein ovalbumin and conferring a resistant Th 1 phenotype to BALB/c mice lethally infected with Leishmania major. This i.s. CpG motif may thus be prototypic for a useful immunostimulating DNA sequence that lacks harmful side effects. 相似文献
7.
8.
9.
Koch B. Hidayat A. Hongbin Zhang Mirvoda V. Lichtinger M. Sandel D. Noe R. 《Photonics Technology Letters, IEEE》2008,20(12):961-963
We demonstrate endless polarization stabilization with a control speed of up to 9 krad/s, over random Poincare sphere trajectories. These are in total >35 Mrad long, are composed in particular of difficult-to-track circles with all radii and orientations, and thereby include all possible worst cases. The maximum polarization mismatch and relative intensity errors are 0.13 rad and 0.43%, respectively. The controller runs on a field-programmable gate array and uses a commercial multistage LiNbO3 polarization transformer as the control device. 相似文献
10.
Sustaining Rural Landscapes: the role of integrated tourism 总被引:2,自引:0,他引:2
The aim of a European Union-funded research project entitled 'Supporting and Promoting Integrated Tourism in Europe's Lagging Rural Regions' (SPRITE) is to analyse and develop the potential for better-integrated tourism in the rural landscapes of Europe. Integrated tourism can be defined as that which is explicitly linked to the localities in which it takes place and, in practical terms, has clear connections with local resources, activities, products, production and service industries, and a participatory local community. Enhancing the sustainable economic potential of rural landscapes requires partnerships among rural people and the sustainable yet productive use of rural resources. A 'culture economy' approach to integrated tourism is proposed, which emphasizes the importance of local identity, the strategic commodification of resources and of place, and the importance of extra-local forces in enabling local activities. It is suggested that this approach may represent a shift beyond more traditional approaches to rural development. 相似文献