全文获取类型
收费全文 | 1894篇 |
免费 | 81篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 25篇 |
综合类 | 1篇 |
化学工业 | 397篇 |
金属工艺 | 36篇 |
机械仪表 | 51篇 |
建筑科学 | 42篇 |
矿业工程 | 2篇 |
能源动力 | 127篇 |
轻工业 | 182篇 |
水利工程 | 22篇 |
石油天然气 | 9篇 |
无线电 | 221篇 |
一般工业技术 | 441篇 |
冶金工业 | 157篇 |
原子能技术 | 27篇 |
自动化技术 | 246篇 |
出版年
2023年 | 17篇 |
2022年 | 39篇 |
2021年 | 71篇 |
2020年 | 46篇 |
2019年 | 51篇 |
2018年 | 79篇 |
2017年 | 64篇 |
2016年 | 76篇 |
2015年 | 51篇 |
2014年 | 62篇 |
2013年 | 148篇 |
2012年 | 86篇 |
2011年 | 96篇 |
2010年 | 82篇 |
2009年 | 101篇 |
2008年 | 97篇 |
2007年 | 80篇 |
2006年 | 49篇 |
2005年 | 32篇 |
2004年 | 20篇 |
2003年 | 31篇 |
2002年 | 32篇 |
2001年 | 24篇 |
2000年 | 24篇 |
1999年 | 22篇 |
1998年 | 27篇 |
1997年 | 34篇 |
1996年 | 30篇 |
1995年 | 17篇 |
1994年 | 19篇 |
1993年 | 24篇 |
1992年 | 18篇 |
1991年 | 18篇 |
1990年 | 9篇 |
1989年 | 15篇 |
1988年 | 22篇 |
1987年 | 15篇 |
1986年 | 20篇 |
1985年 | 24篇 |
1984年 | 24篇 |
1983年 | 28篇 |
1982年 | 18篇 |
1981年 | 25篇 |
1980年 | 21篇 |
1979年 | 11篇 |
1978年 | 17篇 |
1977年 | 11篇 |
1976年 | 22篇 |
1975年 | 13篇 |
1974年 | 10篇 |
排序方式: 共有1986条查询结果,搜索用时 15 毫秒
101.
102.
Jagjiwan Mittal Shih-Ming Kuo Yu-Wei Lin Kwang-Lung Lin 《Journal of Electronic Materials》2009,38(12):2436-2442
Reflow behavior of Sn-Zn solder on Ni/Cu substrate was investigated in an infrared (IR) reflow furnace using different heating
rates from 180 °C/min to 36 °C/min. Energy dispersive spectroscopy (EDX) studies of the reflowed samples showed increased
diffusion of Zn from the solder to the intermetallic compound (IMC) layer with a decrease in heating rate. Higher interfacial
activity and affinity of the Zn in the formation of the IMC with the lowering of the heating rate were further demonstrated
by electron probe microanalyzer (EPMA) results. The Zn diffusion behavior was related to its higher reactivity and smaller
size in comparison with Sn, phase separation during heating, and affinity of Zn to form Ni-Sn-Zn and Ni-Zn intermetallic compounds. 相似文献
103.
Suresh Bhalla Praveen Kumar Ashok Gupta Tushar K. Datta 《Canadian Metallurgical Quarterly》2009,22(4):373-382
The electromechanical impedance technique employs surface-bonded lead zirconate titanate piezoelectric ceramic patches as impedance transducers for structural health monitoring and nondestructive evaluation. The patches are bonded to the monitored structures using finitely thick adhesive bond layer, which introduces shear lag effect, thus invariably influencing the electromechanical admittance signatures. This paper presents a new simplified impedance model to incorporate shear lag effect into electromechanical admittance formulations, both one-dimensional and two-dimensional. This provides a closed-form analytical solution of the inverse problem, i.e. to derive the true structural impedance from the measured conductance and susceptance signatures, thus an improvement over the existing models. The influence of various parameters (associated with the bond layer) on admittance signatures is investigated using the proposed model and the results compared with existing models. The results show that the new model, which is far simpler than the existing models, models the shear lag phenomenon reasonably well besides providing direct solution of a complex inverse problem. 相似文献
104.
Sangamesh G. Kumbar Anandrao R. Kulkarni Ashok M. Dave Tejraj M. Aminabhavi 《应用聚合物科学杂志》2001,82(11):2863-2866
This article presents our preliminary experimental data on the release kinetics and encapsulation efficiency of urea formaldehyde (UF) crosslinked matrices of starch (St), guar gum (GG), and starch + guar gum (St + GG) for the controlled release of solid (chlorpyrifos) and liquid (neem seed oil) pesticides. The data reveal variable release rates in relation to the polymer type and especially the pesticide type. It is possible to slow the release rates of pesticides using cheaply available materials such as starch and guar gum. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2863–2866, 2001 相似文献
105.
Batch sorbitol to sorbose bioconversion by Acetobacter suboxydans using initial sorbitol concentration (S0 = 100 g/L) yielded a productivity of 10.11 g/L‐h and 98.6% conversion in 10 h time. The batch kinetics was then used to develop an unstructured mathematical model. Model parameters were identified using a nonlinear regression technique assisted by a computer program which minimized the deviation between the model predictions and actual batch experimental data. F test indicated 99% confidence on the prediction of model using optimized parameters. The batch model was eventually extrapolated to identify nutrient feeding strategies to maintain constant noninhibitory sorbitol supply and eliminate substrate limitation for fed‐batch fermentation in order to improve the sorbose productivity. The adequacy of the fed‐batch model was established by excellent agreement between experimental data and model simulation (except towards the end of fermentation). 相似文献
106.
Manjima Bhattacharya Riya Chakraborty Arjun Dey Ashok Kumar Mandal Anoop Kumar Mukhopadhyay 《Ceramics International》2013,39(2):999-1009
The present experiments were focused on nanoindentation behaviour and the attendant “micro-pop-in” in a dense (~95% of theoretical) coarse-grain (~20 μm) alumina ceramic as a function of loading rate variations at three constant peak loads in the range of 105–106 μN. Based on the experimental results here we report for the first time, to the best of our knowledge, an increase in intrinsic nano scale contact resistance as well as the nanohardness with the loading rate. These observations were explained in terms of the correlation between the nanoscale plasticity and shear stress active just underneath the nanoindenter. 相似文献
107.
Sagar S Pandit Ram S Kulkarni Hemangi G Chidley Ashok P Giri Keshav H Pujari Tobias G Köllner Jörg Degenhardt Jonathan Gershenzon Vidya S Gupta 《Journal of the science of food and agriculture》2009,89(12):2071-2081
BACKGROUND: Volatile blends of five developing and five ripening stages of mango (Mangifera indica L. cv. Alphonso) were investigated along with those of flowers and leaves. Raw and ripe fruits of cv. Sabja were also used for comparison. RESULTS: A total of 55 volatiles belonging to various chemical classes such as aldehydes, alcohols, mono‐ and sesquiterpene hydrocarbons, lactones and furanones were identified. In all Alphonso tissues monoterpenes quantitatively dominated, with 57–99% contribution; in particular, (Z)‐ocimene was found in the highest amount. Ripeness was characterized by the de novo appearance of lactones and furanones in the blend of monoterpenes. Sabja was distinguished by the abundance of monoterpene hydrocarbons in the raw fruit, and that of sesquiterpene hydrocarbons and their derivatives in the ripe stage. CONCLUSION: Various stages of the Alphonso fruit during transition from flower to ripe fruit are characterized by unique volatile signatures that are distinguished from each other by the qualitative and quantitative appearance of different volatile compounds. Thus volatiles can be highly informative markers while studying the development and ripening of mango. Copyright © 2009 Society of Chemical Industry 相似文献
108.
Ashok Mahajan Naazneen Surti Pooja Koladiya 《Drug development and industrial pharmacy》2018,44(3):463-471
The aim of the present study was to improve the dissolution and flow properties of lurasidone hydrochloride (LH) by solid dispersion adsorbate (SDA) technique. Solid dispersions (SDs) of LH were prepared by fusion method using Poloxamer P188. The melt dispersion was adsorbed onto the porous carrier Florite (calcium silicate). A 32 factorial design was employed to quantify the effect of two independent variables, namely ratio of carrier (Poloxamer 188) and LH in SD and ratio of adsorbent (Florite) to SD. SDA granules of LH were studied for flow properties and characterized using differential scanning calorimetry, scanning electron microscopy, and X-ray diffraction. Tablets of optimized composition of SDA granules (equivalent to 20?mg of drug) and plain tablets were prepared by direct compression method. The dissolution studies were carried out in Mcllvaine buffer (pH 3.8) as per USFDA guidelines and characterized for parameters such as percent dissolution efficiency, t50, and Q30. Tablets prepared from SDA granules showed almost four-fold increase in cumulative percentage drug release as compared to tablets prepared from plain LH. The value of dissolution efficiency was enhanced from 49.60% for plain tablets to 94.15% for SDA tablets. SDA granules did not show any change in drug release and X-ray diffraction pattern after storage at 40?°C/75% of RH for 3?months, which confirms that Florite prevented conversion of drug from amorphous form to crystalline form improving physical stability of the amorphous state of LH. 相似文献
109.
This paper reports on a microfluidic device for the screening of organophosphonate nerve agent degradation products. The miniaturized system relies on an efficient chip-based separation of alkyl methylphosphonic acids (breakdown products of Sarin, Soman, and VX nerve agents) followed by their sensitive contactless conductivity detection. Experimental parameters relevant to the separation and detection processes have been optimized to yield high sensitivity (with 48-86 microg L(-1) detection limits), fast response (50 s for a three alkyl methylphosphonic acid mixture), high precision (RSD = 3.8-5.0%), and good linearity (over the 0.3-100 mg L(-1) range). Applicability to natural (river) water samples is demonstrated. The new microsystem offers promise for monitoring degradation products of chemical warfare agents, with advantages of speed/warning, efficiency, portability, sample size, and cost compared to conventional ion chromatography or capillary electrophoresis systems. 相似文献
110.
The problem of video classification can be viewed as discovering the signature patterns in the elemental features of a video
class. In order to solve this problem, a large and diverse set of video features is proposed in this paper. The contributions
of the paper further lie in dealing with high-dimensionality induced by the feature space and in presenting an algorithm based
on two-phase grid searching for automatic parameter selection for support vector machine (SVM). The framework thus is directed
to bridge the gap between low-level features and semantic video classes. The experimental results and comparison with state-of-the-art
learning tools on more than 5000 video segments show the effectiveness of our approach. 相似文献