全文获取类型
收费全文 | 11838篇 |
免费 | 894篇 |
国内免费 | 52篇 |
专业分类
电工技术 | 215篇 |
综合类 | 68篇 |
化学工业 | 2938篇 |
金属工艺 | 336篇 |
机械仪表 | 372篇 |
建筑科学 | 329篇 |
矿业工程 | 41篇 |
能源动力 | 476篇 |
轻工业 | 2277篇 |
水利工程 | 139篇 |
石油天然气 | 81篇 |
无线电 | 781篇 |
一般工业技术 | 1925篇 |
冶金工业 | 1216篇 |
原子能技术 | 86篇 |
自动化技术 | 1504篇 |
出版年
2024年 | 45篇 |
2023年 | 130篇 |
2022年 | 348篇 |
2021年 | 571篇 |
2020年 | 385篇 |
2019年 | 483篇 |
2018年 | 535篇 |
2017年 | 557篇 |
2016年 | 511篇 |
2015年 | 363篇 |
2014年 | 501篇 |
2013年 | 867篇 |
2012年 | 748篇 |
2011年 | 811篇 |
2010年 | 557篇 |
2009年 | 623篇 |
2008年 | 529篇 |
2007年 | 449篇 |
2006年 | 382篇 |
2005年 | 277篇 |
2004年 | 258篇 |
2003年 | 300篇 |
2002年 | 302篇 |
2001年 | 242篇 |
2000年 | 184篇 |
1999年 | 163篇 |
1998年 | 376篇 |
1997年 | 260篇 |
1996年 | 205篇 |
1995年 | 133篇 |
1994年 | 109篇 |
1993年 | 101篇 |
1992年 | 57篇 |
1991年 | 42篇 |
1990年 | 45篇 |
1989年 | 44篇 |
1988年 | 44篇 |
1987年 | 24篇 |
1986年 | 32篇 |
1985年 | 25篇 |
1984年 | 19篇 |
1982年 | 9篇 |
1981年 | 12篇 |
1980年 | 12篇 |
1979年 | 11篇 |
1977年 | 13篇 |
1976年 | 37篇 |
1975年 | 10篇 |
1974年 | 10篇 |
1973年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
NE Taylor RN Rosenthal B Chabus S Levine AS Hoffman J Reynolds L Santos I Willets P Friedman 《Canadian Metallurgical Quarterly》1993,15(1):36-40
Cryptococcal meningitis has a high mortality rate of central nervous infection. The patients usually die of the disease itself, or complications from increased intracranial pressure. Early diagnosis and treatment, including surgical drainage, will improve the results. In this series, twenty-one patients with high intracranial pressure (ICP > 300 mmH2 O) are presented. Fourteen received implantation of Ommaya reservoir to aspirate cerebrospinal fluid (CSF) for relief of symptoms of ICP. Meanwhile 4 of these 14 patients also received intraventricular injection of amphotericin B because of poor response to systemic drugs. Another seven patient received systemic drug therapy only. Survival during therapy occurred in 11 of 14 patients in the surgical group, compared with only 1 of 7 patients treated by drug therapy alone (P = 0.019). In the 14 patients who received implantation of an Ommaya reservoir, there was one complication of CSF leakage when the reservoir ruptured because of repeated aspiration. For patients with cryptococcal meningitis with high ICP, early implantation of an Ommaya reservoir will improve the survival rate. 相似文献
102.
The first part of this paper analyses the influence of the molecular weight and concentration of carboxymethyl cellulose (CMC) and of kaolin concentration on rheology of the coating colours and on paper properties coated with ultra lightweight coatings (ULWC). In the second part, relationships between the rheological characteristics of the coating colour formulations and coated paper surface quality was also studied.New indexes on paper roughness at micro-scale are presented (RZI and SRI). In general, they show good correlation with sheet gloss. A new gloss index (SGI) is presented, accounting for the contribution of gloss from machine direction (MD) and cross direction (CD). Porosimetry was used to access microstructural characteristics in order to correlate them with light scattering and gloss properties. The former property is closely related to Hg intrusion volume of the coated layer while gloss is related to surface porosity with pore diameters in the range of 7–15 μm as measured by Hg intrusion volume. 相似文献
103.
104.
Solid polymer electrolytes (SPEs) synthesized by the sol-gel process and designated as di-ureasils have been prepared through the incorporation of lithium perchlorate, LiClO4, into the d-U(2000) organic-inorganic hybrid network. Electrolytes with lithium salt compositions of n (where n indicates the number of oxyethylene units per Li+ ion) between ∞ and 0.5 were characterized by conductivity measurements, cyclic voltammetry at a gold microelectrode, thermal analysis and Fourier transform Raman (FT-Raman) spectroscopy. The conductivity results obtained suggest that this system offers a quite significant improvement over previously characterized analogues doped with lithium triflate [S.C. Nunes, V. de Zea Bermudez, D. Ostrovskii, M.M. Silva, S. Barros, M.J. Smith, R.A. Sá Ferreira, L.D. Carlos, J. Rocha, E. Morales, J. Electrochem. Soc. 152 (2) (2005), A429]. “Free” perchlorate ions, detected in all the samples examined, are identified as the main charge carriers in the sample that yields the highest room temperature conductivity (n = 20). In the di-ureasils with n ≤ 10 ionic association is favoured and the ionic conductivity drops. 相似文献
105.
Muga N. J. Pinto A. N. Ferreira M. F. S. Ferreira da Rocha J. R. 《Lightwave Technology, Journal of》2006,24(11):3932-3943
A detailed study of fiber-coil-based polarization controllers (PCs) is performed. First, a method to deterministically calculate the PC configuration in order to transform between any two states of polarization is presented. In a second stage, the case in which the configuration angles are randomly changed is studied. The cases of a single PC and of the system obtained with the concatenation of several PCs are analyzed. For both cases, a general expression for the variance of the Stokes parameters is obtained. Using this expression, it is demonstrated that it is possible to achieve uniform polarization scattering using a concatenation of fiber-coil-based PCs. Finally, it is shown that fiber-coil-based PCs can be used to emulate both first- and second-order polarization-mode dispersions 相似文献
106.
J.V. Lobato N. Sooraj Hussain C.M. Botelho A.C. Maurício A. Afonso J.D. Santos 《Thin solid films》2006,515(1):362-367
Synthetic bone grafts have been developed to provide an alternative to autografts and allografts. Bonelike® is a patented synthetic osteoconductive bone graft that mimics the mineral composition of natural bone. In the present preliminary animal studies a user-friendly version of synthetic bone graft Bonelike® have been developed by using a resorbable matrix, Floseal®, as a vehicle and raloxifene hydrochloride as a therapeutic molecule, that is known to decrease osteoclast activity and therefore enhanced bone formation. From histological and scanning electron microscopy evaluations, the use of Bonelike® associated with Floseal® and raloxifene hydrochloride showed that new bone was rapidly apposed on implanted granules and also that the presence of the matrix and therapeutic molecule does not alter the proven highly osteoconductivity properties of Bonelike®. Therefore, this association may be one step-forward for the clinical applications of Bonelike® scaffolds since it is much more easy-to-handle when compared to granular materials. 相似文献
107.
O. Acselrad I. S. Kalashnikov E. M. Silva M. S. Khadyev R. A. Simao 《Metal Science and Heat Treatment》2006,48(11-12):543-553
The phase composition and the morphology of structures formed as a result of isothermal holds in the range of aging temperatures of hardened alloy Fe-28% Mn, 8.5% Al-1% C-1.25% S are studied. A diagram of the decomposition of initial austenite is plotted starting with the early stages and ending with the moment when the system attains the equilibrium state. 相似文献
108.
J. J. Rêgo Silva L. C. Wrobel J. C. F. Telles 《International journal for numerical methods in engineering》1993,36(10):1661-1679
This paper presents a new family of continuous/discontinuous three-dimensional boundary elements which has been implemented in a computer system for acoustic wave propagation in the frequency domain. The system includes elements of different geometrical shapes, 'order of interpolation and degree of continuity. Results of several tests are included to show the efficiency of the family of elements. 相似文献
109.
M. A. R. Buzalaf B. S. de Almeida V. E. da Silva Cardoso K. P. K. Olympio T. de Almeida Furlani 《Food Additives & Contaminants》2004,21(3):210-215
Total fluoride (TF) and HCl 0.01 M ('gastric juice')-soluble fluoride (SF) were analysed in infant foods, beverages and calcium-rich biscuits. Samples were divided into seven categories: children cereals (A), chocolate-flavoured milk (B), soy beverages (C), filled biscuits (D), non-filled biscuits (E), wafer biscuits (F) and corn starch biscuits (G). Mean TF concentrations ± SD (amplitude, unit µg F ml-1 or µg F g-1) were: (A) 4.25 ± 3.04 (0.20 - 7.84, n = 6); (B) 0.34 ± 0.47 (0.05-1.27, n = 6); (C) 0.15 ± 0.07 (0.09-0.29, n = 8); (D) 8.44 ± 1.76 (7.65-10.47, n = 4); (E) 12.41 ± 1.15 (10.69-13.68, n = 4); (F) 0.35 ± 0 (0.34-0.36, n = 4) and (G) 7.77 ± 1.12 (6.86-8.68, n = 2). Five samples of cereals, one sample of chocolate-flavoured milk and 10 samples of biscuits were analysed for SF. In cereals analysed for SF, all fluoride was soluble, while for the chocolate-flavoured milk, approximately 50% of TF was soluble. Regarding the biscuits analysed for SF approximately 20% of TF was soluble. It was observed that some of the cereals and beverages, and most of the biscuits analysed, might be important contributors to total daily fluoride intake. When consumed just once per day, cereals and beverages might supply up to 25% of the maximum recommended daily fluoride intake (0.07 mg F kg-1 body weight) for a 2-year-old child (12 kg). For the filled, non-filled and corn starch biscuits, when 3, 32 or 20 units of them, respectively, are consumed just once per day, they may supply up to 16% of the maximum recommended daily fluoride intake. However, only approximately 25% of fluoride absorption occurs from the stomach and 75% from the small intestine. Therefore, a higher fluoride bioavailability is possible. 相似文献
110.
Tuning of 802.11e network parameters 总被引:1,自引:0,他引:1
This paper introduces a mechanism which dynamically tunes the parameters of the 802.11e contention-based access method. The proposed mechanism aims at providing QoS as well as ameliorating the problem of delay asymmetry. 相似文献