全文获取类型
收费全文 | 17433篇 |
免费 | 1443篇 |
国内免费 | 20篇 |
专业分类
电工技术 | 144篇 |
综合类 | 10篇 |
化学工业 | 6360篇 |
金属工艺 | 183篇 |
机械仪表 | 398篇 |
建筑科学 | 599篇 |
矿业工程 | 23篇 |
能源动力 | 502篇 |
轻工业 | 3869篇 |
水利工程 | 144篇 |
石油天然气 | 98篇 |
无线电 | 857篇 |
一般工业技术 | 2456篇 |
冶金工业 | 1048篇 |
原子能技术 | 76篇 |
自动化技术 | 2129篇 |
出版年
2024年 | 49篇 |
2023年 | 236篇 |
2022年 | 1022篇 |
2021年 | 1189篇 |
2020年 | 511篇 |
2019年 | 571篇 |
2018年 | 640篇 |
2017年 | 648篇 |
2016年 | 729篇 |
2015年 | 598篇 |
2014年 | 828篇 |
2013年 | 1264篇 |
2012年 | 1153篇 |
2011年 | 1292篇 |
2010年 | 967篇 |
2009年 | 937篇 |
2008年 | 809篇 |
2007年 | 786篇 |
2006年 | 608篇 |
2005年 | 475篇 |
2004年 | 423篇 |
2003年 | 362篇 |
2002年 | 341篇 |
2001年 | 212篇 |
2000年 | 166篇 |
1999年 | 198篇 |
1998年 | 286篇 |
1997年 | 224篇 |
1996年 | 183篇 |
1995年 | 128篇 |
1994年 | 105篇 |
1993年 | 123篇 |
1992年 | 86篇 |
1991年 | 70篇 |
1990年 | 64篇 |
1989年 | 69篇 |
1988年 | 55篇 |
1987年 | 50篇 |
1986年 | 59篇 |
1985年 | 51篇 |
1984年 | 46篇 |
1983年 | 27篇 |
1982年 | 28篇 |
1981年 | 26篇 |
1980年 | 31篇 |
1979年 | 28篇 |
1978年 | 23篇 |
1977年 | 22篇 |
1976年 | 25篇 |
1975年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
The bulk modification of SBS rubber with maleic anhydride in a mixing chamber of a Haake rheomixer was studied. The effect of temperature, maleic anhydride, and benzoyl peroxide concentrations on the grafting efficiency was evaluated. High grafting efficiency was achieved when the ratio of peroxide and maleic anhydride concentration was high. On the other hand, on this condition high insoluble fraction was generated. The addition of a diamine, 4,4′‐diaminediphenylmethane to the reaction mixture minimizes the amount of insoluble polymer. However, the grafted MAH content also decreases. The graft copolymer was characterized by infrared spectroscopy and the grafting extension was determined by titration. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2953–2960, 2002; DOI 10.1002/app.10355 相似文献
102.
In this paper we develop and compare several heuristic methods for solving the general two-dimensional cutting stock problem.
We follow the Gilmore-Gomory column generation scheme in which at each iteration a new cutting pattern is obtained as the
solution of a subproblem on one stock sheet. For solving this subproblem, in addition to classical dynamic programming, we
have developed three heuristic procedures of increasing complexity, based on GRASP and Tabu Search techniques, producing solutions
differing in quality and in time requirements. In order to obtain integer solutions from the fractional solutions of the Gilmore-Gomory
process, we compare three rounding procedures, rounding up, truncated branch and bound and the solution of a residual problem.
We have coded and tested all the combinations of algorithms and rounding procedures. The computational results obtained on
a set of randomly generated test problems show their relative efficiency and allow the potential user to choose from among
them, according to the available computing time.
Rceived: January 9, 2001 / Accepted: December 10, 2001 相似文献
103.
Ionomeric composites based on sepiolite and hydrogenated poly(styrene butadiene) block copolymer were obtained and characterized from a microstructural and electrical point of view. Before blending, because of the high silanol group concentration in the sepiolite, the latter could be organophilized with suitable coupling agents. The resulting materials were easily processed into thin films or membranes 0.2–0.4 mm thick, their conductivity in some cases approaching 10?1 S/cm. Their suitability for film formation and good electrical properties indicate potential applications as electrolytes in polymer fuel cells. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3512–3519, 2002 相似文献
104.
P Casolo D Mosca C Amorotti B Drei A Raspadori P Di Blasio E Ganz G De Luca G Colli R De Maria D Amuso 《Canadian Metallurgical Quarterly》1997,68(2):207-11; discussion 212
Primary and sole breast lymphoma is a very rare disease. With the review of our series of 616 cases operated on for breast cancer, only 3 cases (0.48%) of primary breast non-Hodgkin lymphoma (LNH) have been observed. The authors outline the problems concerning diagnosis and therapy of this rare disease: pathological and immunohistochemical aspects are discussed. They stress the importance of staging in order to plan a correct multidisciplinary approach. 相似文献
105.
JF Tomás E Rodriguez-I?igo J Bartolomé A Madejón M Fogeda H Oliva A Moreno JM Fernández-Ra?ada V Carre?o 《Canadian Metallurgical Quarterly》1997,19(10):1053-1057
Long-term effects after blood or bone marrow transplantation (BMT) are emerging as an important issue, as more patients are included in BMT programmes and as this procedure becomes more successful. Long-term liver dysfunction, mainly due to chronic graft-versus-host disease or hepatitis C virus infection, is a well-known complication. Nevertheless, the diagnosis of liver disease in this patient group is sometimes difficult and, despite adequate studies, it may remain undetected. A novel hepatitis-associated virus, hepatitis G virus (HGV), has recently been identified. The virus belongs to the Flaviviridae family and is known to be parenterally transmitted, although there is no clear evidence to implicate this agent in causing acute or chronic hepatitis. We report a patient who developed mild, but persistent, abnormalities in transaminases for 2 years after an autologous BMT. HGV RNA was detected in both serum and liver. HGV RNA persisted in serum for at least 8 months. No other known hepatitis virus was found. This report provides the first direct evidence of a patient with long-term liver abnormalities after a BMT in whom the only known hepatitis virus isolated was the HGV. 相似文献
106.
107.
108.
Birthe Mller Jose Luis Molina‐Cano Lars Munck 《Journal of the Institute of Brewing》2002,108(3):294-302
In earlier studies concerning vigour, where subsamples are heat‐treated before germination there was found heat‐sensitive as well as heat‐resistant barley samples. The vigour model developed by Ellis and Roberts and further developed at Carlsberg, could only describe the heat‐sensitive barleys. Seventeen samples of the “Alexis” variety grown widely in Europe were collected from the EBC trials in 1994 in order to see if heat resistance in barley was influenced by different growing conditions. We found both heat‐sensitive samples following the vigour model as well as pronounced heat‐resistant samples, but these were not divided according to growing conditions. The germination curves dependent on heat treatment and germination time were evaluated by Principal Component Analysis (PCA). Heat‐resistant barley samples could be differentiated from heat‐sensitive samples already after ½ h of heat treatment at 68°C (12% moisture) and after 3 days of germination. The barley samples were analysed with regard to malting quality. The PCA evaluation of the data divided the samples according to growing location, mainly due to differences in protein and β‐glucan. However, the malting analyses could not describe the differences in heat resistance and sensitivity of the barleys. The biochemical background of the heat resistance found is discussed on the basis of literature. Our findings should give an experimental basis for exploiting a biochemical principle for heat resistance, which is formed during grain filling and consumed during storage and germination. 相似文献
109.
Vilar Moreno C. Amaris Duarte H. Usaola Garcia J. 《Energy Conversion, IEEE Transaction on》2002,17(2):267-272
Wind energy conversion systems (WECS) produce fluctuating output power, which may cause voltage fluctuations and flicker. Flicker assessment in networks may be difficult since its evaluation requires long computing time and special procedures to calculate the flicker severity index, Pst. In this paper, a frequency domain method to study flicker propagation is presented. This method is based on propagation of frequency components from WECS output currents throughout the grid. In this way, a fast flicker analysis in a network of any size can be performed. Also, an algorithm for flicker measurement in the frequency domain, which allows Pst calculation, is proposed. Several study cases have been performed, and results have been compared with time domain simulations, showing good agreement between them 相似文献
110.
Juntunen Cindy L.; Atkinson Donald R.; Reyes Carla; Gutierrez Maria 《Canadian Metallurgical Quarterly》1994,31(2):327
Investigated whether (1) feminist identity development for women therapists was related to their use of feminist therapy behaviors (FTBs) and (2) feminist identity development and use of FTBs for women therapists were related to self-identification as a feminist therapist. 153 women psychologists (aged 30–77 yrs) were administered a women's issues in therapy questionnaire, which included a short version of the Feminist Identity Scale (FIS; K. M. Rickard, 1989, 1990). Ss were categorized into stages of feminine identity development according to their scores on 4 subscales of the FIS: Passive-Acceptance (PA), Revelation (REV), Embeddedness (EMB), and Synthesis (SYN). Ss scoring high on SYN and REV, and low on PA, reported greater use of FTBs; scores on the EMB were not related to the use of FTBs. All 4 subscales were predictive of women therapists who self-identified as feminist therapists. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献