全文获取类型
收费全文 | 3502篇 |
免费 | 151篇 |
国内免费 | 14篇 |
专业分类
电工技术 | 48篇 |
综合类 | 10篇 |
化学工业 | 816篇 |
金属工艺 | 78篇 |
机械仪表 | 49篇 |
建筑科学 | 169篇 |
矿业工程 | 29篇 |
能源动力 | 62篇 |
轻工业 | 295篇 |
水利工程 | 17篇 |
石油天然气 | 14篇 |
无线电 | 314篇 |
一般工业技术 | 665篇 |
冶金工业 | 669篇 |
原子能技术 | 30篇 |
自动化技术 | 402篇 |
出版年
2023年 | 21篇 |
2022年 | 40篇 |
2021年 | 67篇 |
2020年 | 49篇 |
2019年 | 58篇 |
2018年 | 54篇 |
2017年 | 64篇 |
2016年 | 91篇 |
2015年 | 88篇 |
2014年 | 123篇 |
2013年 | 137篇 |
2012年 | 134篇 |
2011年 | 160篇 |
2010年 | 115篇 |
2009年 | 138篇 |
2008年 | 134篇 |
2007年 | 142篇 |
2006年 | 99篇 |
2005年 | 105篇 |
2004年 | 80篇 |
2003年 | 91篇 |
2002年 | 72篇 |
2001年 | 65篇 |
2000年 | 60篇 |
1999年 | 81篇 |
1998年 | 218篇 |
1997年 | 150篇 |
1996年 | 114篇 |
1995年 | 75篇 |
1994年 | 70篇 |
1993年 | 75篇 |
1992年 | 43篇 |
1991年 | 40篇 |
1990年 | 41篇 |
1989年 | 38篇 |
1988年 | 31篇 |
1987年 | 35篇 |
1986年 | 39篇 |
1985年 | 35篇 |
1984年 | 26篇 |
1983年 | 37篇 |
1981年 | 29篇 |
1980年 | 27篇 |
1979年 | 31篇 |
1978年 | 30篇 |
1977年 | 24篇 |
1976年 | 47篇 |
1975年 | 15篇 |
1974年 | 15篇 |
1973年 | 19篇 |
排序方式: 共有3667条查询结果,搜索用时 15 毫秒
21.
JC Mohle-Boetani JE Koehler TG Berger PE LeBoit CA Kemper AL Reingold BD Plikaytis JD Wenger JW Tappero 《Canadian Metallurgical Quarterly》1996,22(5):794-800
Clinical characteristics associated with bacillary angiomatosis and bacillary peliosis (BAP) in patients with human immunodeficiency virus (HIV) infection were evaluated in a case-control study; 42 case-patients and 84 controls were matched by clinical care institution. Case-patients presented with fever (temperature, > 37.8 degrees C; 93%), a median CD4 lymphocyte count of 21/mm3, cutaneous or subcutaneous vascular lesions (55%), lymphadenopathy (21%), and/or abdominal symptoms (24%). Many case-patients experienced long delays between medical evaluation and diagnosis of BAP (median, 4 weeks; range, 1 day to 24 months). Case-patients were more likely than controls to have fever, lymphadenopathy, hepatomegaly, splenomegaly, a low CD4 lymphocyte count, anemia, or an elevated serum level of alkaline phosphatase (AP) (P < .001). In multivariate analysis, a CD4 lymphocyte count of < 200/mm3 (matched odds ratio [OR], 9.9; P < .09), anemia reflected by a hematocrit value of < 0.36 (OR, 19.7; P < .04), and an elevated AP level of > or = 2.6 mukat/L (OR, 23.9; P < .05) remained associated with disease after therapy with zidovudine was controlled for. BAP should be considered an AIDS-defining opportunistic infection and should be included in the differential diagnosis for febrile, HIV-infected patients with cutaneous or osteolytic lesions, lymphadenopathy, abdominal symptoms, anemia, or an elevated serum level of AP. 相似文献
22.
An inulin syrup made from Jerusalem artichoke tubers, either in its commercial form or after ultrafiltration, was freeze-dried and used as a prebiotic ingredient in the small-scale manufacture of wafer crackers. The flours used for the preparation of wafer batters were from wheat, rye or spelt wheat, or 1:1 combinations of wheat flour and rye flour or wheat flour and spelt wheat flour. Batter viscosity was strongly influenced by the selection of the flour type, but remained within technologically acceptable limits. The ultrafiltration of the inulin syrup, using a 1 kDa membrane, resulted in a significant reduction of the content of free sugars and minerals which, in turn, had a significant impact on the CIE-Lab color values of the wafer crackers. Using spelt wheat flour instead of wheat flour significantly increased wafer cracker firmness measured by penetration, as did the incorporation of ultrafiltered freeze-dried instead of native freeze-dried Jerusalem artichoke syrup. Sensory analysis revealed a significant influence of product formulation on appearance, flavor and texture of the wafer crackers. It can be concluded from quality scores, which were calculated by using weighting factors assigned to the sensory attributes, that wheat flour may be partially replaced by rye flour or spelt wheat flour without negatively affecting the sensory properties of the wafer crackers. 相似文献
23.
Multiterminal source encoding with one distortion criterion 总被引:1,自引:0,他引:1
Berger T. Yeung R.W. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1989,35(2):228-236
The authors unify earlier investigations concerning the encoding of two correlated sources {X k}, {Y k } by means of separate encoders. Decoding is done by a single decoder which receives the outputs from both encoders. The reconstruction of {X k} is required to be perfect in the usual Shannon sense. The authors determine the admissible rate region R (D ), where D is the distortion of the reconstruction of {Y k}. The binary Hamming case is investigated explicitly 相似文献
24.
25.
Ohne Zusammenfassung 相似文献
26.
27.
The special situation of patent information is dealt with against the background of the general problems of information provision. The role of the Patent Department of Siemens as a user of patent information and in the distribution of patent information within the company is discussed. Finally, the present system of current patent information on granted patents and first publications is outlined and an outlook on future developments given. 相似文献
28.
Rheological behaviour of 48 Swiss-type cheese samples in lubricated uniaxial compression was evaluated at three initial strain rates ranging from 4·76 × 10−3 to 7·62 × 10−2 s−1. Modulus, apparent fracture stress and apparent fracture strain increased significantly with increasing strain rate, which is attributed to the viscoelastic nature of cheese. The influence of strain rate on apparent fracture strain strongly depended on the shape of the stress-strain curves. The relationship between the rheological parameters evaluated at different strain rates proved to be significant. The strain rate dependency of the apparent fracture strain is further explained by the contribution of elastic and viscous components, which was evaluated in relaxation experiments in the linear viscoelastic region. 相似文献
29.
Ingo Alig Dirk Lellinger Harald Oehler Sergey A. Adamovsky Christoph Schick 《Progress in Organic Coatings》2008,61(2-4):166-175
A new microcalorimeter with eight parallel channels using robust, low cost sensors for characterization of coatings and adhesives is described and first experiments on coatings and adhesives are presented. The calorimetric sensors are based on thin glass plates (20 mm × 20 mm, thickness 150 μm) with heater and thermocouple sputtered on the surfaces (calorimetric active area of about 9 mm2). The setup allows heating and cooling experiments as well as isothermal measurements in the temperature-modulated mode with up to eight sensors in parallel. The measured quantities are the real (C′p) and imaginary part (C″p) of the complex heat capacity (), the related absolute value of the heat capacity () and the heat flow . An industrial computer (NI PXI system) with specific software for calibration and data recording controls the electronic components. Sensors can be embedded in a temperature controlled oven (heating and cooling by Peltier elements) or alternatively in a climatic cabinet with controlled temperature and humidity.
The method has been applied successfully to monitoring of film formation of aqueous polymer dispersions (styrene-acrylate copolymer) and curing of coatings. 相似文献
30.
Martin Fleischmann Harald Krenn Josef Eberhardsteiner Gerhard Schickhofer 《Holz als Roh- und Werkstoff》2007,65(4):301-313
To be able to perform more realistic simulations of timber constructions with modern numerical simulation methods like the finite element method (FEM), a suitable constitutive material model is required. Such a material model was developed by Mackenzie-Helnwein et al. (2005) for clear spruce wood. This paper presents an application-oriented adaption and usage of the mentioned material model, its implementation in a FE software as well as performing ultimate load analyses using FEM and the validation of the material model by means of the comparison of results of FE Simulations and experiments on the structure level (Fleischmann 2005). Further, some aspects with respect to the standardisation are discussed in one of the two examples. 相似文献