全文获取类型
收费全文 | 1188篇 |
免费 | 23篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 62篇 |
综合类 | 4篇 |
化学工业 | 307篇 |
金属工艺 | 35篇 |
机械仪表 | 35篇 |
建筑科学 | 21篇 |
矿业工程 | 1篇 |
能源动力 | 54篇 |
轻工业 | 79篇 |
水利工程 | 2篇 |
无线电 | 96篇 |
一般工业技术 | 204篇 |
冶金工业 | 148篇 |
原子能技术 | 61篇 |
自动化技术 | 110篇 |
出版年
2023年 | 3篇 |
2022年 | 9篇 |
2021年 | 18篇 |
2019年 | 10篇 |
2018年 | 17篇 |
2017年 | 13篇 |
2016年 | 16篇 |
2015年 | 15篇 |
2014年 | 16篇 |
2013年 | 53篇 |
2012年 | 45篇 |
2011年 | 71篇 |
2010年 | 39篇 |
2009年 | 38篇 |
2008年 | 56篇 |
2007年 | 47篇 |
2006年 | 47篇 |
2005年 | 52篇 |
2004年 | 36篇 |
2003年 | 32篇 |
2002年 | 30篇 |
2001年 | 23篇 |
2000年 | 22篇 |
1999年 | 38篇 |
1998年 | 88篇 |
1997年 | 35篇 |
1996年 | 35篇 |
1995年 | 22篇 |
1994年 | 30篇 |
1993年 | 20篇 |
1992年 | 10篇 |
1991年 | 23篇 |
1990年 | 13篇 |
1989年 | 13篇 |
1988年 | 8篇 |
1987年 | 13篇 |
1986年 | 18篇 |
1985年 | 13篇 |
1984年 | 20篇 |
1983年 | 14篇 |
1982年 | 12篇 |
1981年 | 13篇 |
1980年 | 9篇 |
1979年 | 18篇 |
1978年 | 13篇 |
1977年 | 12篇 |
1976年 | 8篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1967年 | 2篇 |
排序方式: 共有1219条查询结果,搜索用时 0 毫秒
21.
Masao Tomikawa Frank W. Harris Stephen Z. D. Cheng Edward Galentier 《Reactive and Functional Polymers》1996,30(1-3):101-107
A series of new, substituted pyromellitic dianhydrides were synthesized from 1,2,4,5-tetramethylbenzene. New soluble rigid-rod polyimides were obtained from the dianhydrides and 2,2′-bis(trifluoromethyl)-4,4′-biphenyl (PFMB) in phenolic solvents in the presence of isoquinoline as a catalyst. The polyimides are soluble in N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAc), m-cresol and other solvents, in spite of having no bending in their rigid structures.
UV irradiation changed color of the polyimide solutions and also their viscosity. We observed new absorbance in the 700-nm region and an ESR signal by UV irradiation. The new visible absorbance and the ESR signal are derived from the same origin. They are attributed to the anion radical of the diimide moiety in the polyimide as deduced from the hyper fine structure of the ESR signal. In addition, UV irradiation diminishes the solution viscosity. 相似文献
22.
Sun-Chan Jeong Ichiro Katayama Hirokane Kawakami Yutaka Watanabe Hironobu Ishiyama Nobuaki Imai Yoshikazu Hirayama Hiroari Miyatake Masao Sataka Satoru Okayasu Hiroyuki Sugai Shin-Ichi Ichikawa Katsuhisa Nishio Shinichi Mitsuoka Takamitsu Nakanoya Masahito Yahagi Takanori Hashimoto Kazunori Takada Mamoru Watanabe Tomoko Ishikawa Akihiro Iwase 《Journal of Phase Equilibria and Diffusion》2005,26(5):472-476
For the effective use of short-lived radioactive beams, soon to be available at the Tokai Radioactive Ion Accelerator Complex, the authors have developed a radiotracer method for diffusion studies in solids. The experimental test was performed by the measurement of the diffusion coefficients of Li in a sample of the compound βLiAl using an α-emitting radiotracer of 8Li (T1/2=0.84 s). It was found that the time-dependent yields of the α particles from the diffusing 8Li that was initially implanted in the sample could be used as a measure of the diffusivity of the tracer in a nondestructive way. The method was applied to measure the self-diffusion coefficients of Li in βLiGa, and for investigating how the Li diffusion in the Li ionic conductors is affected by the concentration of atomic defects (i.e., the existence of the atomic vacancies of Li and the defects in Ga sites that are replaced by Li). 相似文献
23.
Masahiro Hayashi Masahiko Jin Sutasn Thipprakmas Masao Murakawa Jung-Chung Hung Yu-Chung Tsai Ching-Hua Hung 《Journal of Materials Processing Technology》2003,140(1-3):30-35
In ultrasonic-vibration drawing, wires are drawn while ultrasonic vibration is applied to a drawing die. Prior studies provide experimental proof that ultrasonic-vibration drawing reduces drawing resistance, improves lubrication and prevents wire breakage. In the future, ultrasonic-vibration drawing is expected to contribute to the drawing of difficult-to-draw materials and operations, such as shaped wires, ultrafine wires, and the wire drawing operation in semidry or dry condition. However, a detailed analysis and understanding of the mechanism of improvement is not possible on the basis of conventional experimental observations because the ultrasonic-vibration processing phenomenon occurs at high speed. Therefore, we attempted to understand the processing mechanism of ultrasonic-vibration drawing using the finite element method (FEM). ABAQUS was used for the FEM. Drawing force and stress–strain distributions in drawn wires were analyzed. From these studies, we quantitatively clarified the mechanism of improved drawing characteristics, such as decreased drawing force. 相似文献
24.
Emad Shihab Akinori Ihara Yasutaka Kamei Walid M. Ibrahim Masao Ohira Bram Adams Ahmed E. Hassan Ken-ichi Matsumoto 《Empirical Software Engineering》2013,18(5):1005-1042
Bug fixing accounts for a large amount of the software maintenance resources. Generally, bugs are reported, fixed, verified and closed. However, in some cases bugs have to be re-opened. Re-opened bugs increase maintenance costs, degrade the overall user-perceived quality of the software and lead to unnecessary rework by busy practitioners. In this paper, we study and predict re-opened bugs through a case study on three large open source projects—namely Eclipse, Apache and OpenOffice. We structure our study along four dimensions: (1) the work habits dimension (e.g., the weekday on which the bug was initially closed), (2) the bug report dimension (e.g., the component in which the bug was found) (3) the bug fix dimension (e.g., the amount of time it took to perform the initial fix) and (4) the team dimension (e.g., the experience of the bug fixer). We build decision trees using the aforementioned factors that aim to predict re-opened bugs. We perform top node analysis to determine which factors are the most important indicators of whether or not a bug will be re-opened. Our study shows that the comment text and last status of the bug when it is initially closed are the most important factors related to whether or not a bug will be re-opened. Using a combination of these dimensions, we can build explainable prediction models that can achieve a precision between 52.1–78.6 % and a recall in the range of 70.5–94.1 % when predicting whether a bug will be re-opened. We find that the factors that best indicate which bugs might be re-opened vary based on the project. The comment text is the most important factor for the Eclipse and OpenOffice projects, while the last status is the most important one for Apache. These factors should be closely examined in order to reduce maintenance cost due to re-opened bugs. 相似文献
25.
Hideyuki Nakano Hiroyuki Tetsuka Michelle J. S. Spencer Tetsuya Morishita 《Science and Technology of Advanced Materials》2018,19(1):76-100
Mono-elemental two-dimensional (2D) crystals (graphene, silicene, germanene, stanene, and so on), termed 2D-Xenes, have been brought to the forefront of scientific research. The stability and electronic properties of 2D-Xenes are main challenges in developing practical devices. Therefore, in this review, we focus on 2D free-standing group-IV graphene analogs (graphene quantum dots, silicane, and germanane) and the functionalization of these sheets with organic moieties, which could be handled under ambient conditions. We highlight the present results and future opportunities, functions and applications, and novel device concepts. 相似文献
26.
A new image analysis-based technique was used to quantitatively examine the effects of the "Ca2+-jump" activation protocol on the maintenance of fiber quality in skinned rabbit psoas muscle fiber segments. Specifically, contractions in pCa 4.6 were preceded by short-duration "preactivation" soaks in a solution in which EGTA was replaced with the low-Ca2+ buffering capacity analog hexamethylenediamine-N, N, N', N'-tetraacetate, which facilitated rapid Ca2+ equilibration within the fiber segments. Fiber quality was assessed by examining the Fourier spectra of the muscle fiber images before, during, and after activation. Segment lengths were typically below 500 micrometer, thus allowing the majority of the sarcomeres to be visualized in the field of view (x200 and x400 magnification). The preactivation protocol resulted in less deterioration of fiber quality with repetitive activation. In addition, there was also a significant reduction in the time required to reach the 50% level of maximum tension, with no significant change in the maximum tension level. 相似文献
27.
This study was designed to test the hypothesis that distinct alterations in cardiac beta-adrenoceptors (betaARs) may occur during cardiopulmonary bypass (CPB) alone, during CPB with cold cardioplegic cardiac arrest (CCCA), and during CPB with electrically induced ventricular fibrillation (EIVF). We assessed the density and affinity of right atrial betaARs in 27 patients undergoing open-heart surgery by (-)-[125I]iodocyanopindolol binding before CPB, defined as the "control," immediately after initiation, defined as "before," and immediately before the cessation of CCCA or EIVF, defined as "after." The density of betaARs was equivalent between the "control" and "before" groups; however, during CPB with EIVF, the density of betaARs decreased significantly (P < 0.001), whereas during CPB with CCCA, it increased significantly (P < 0.01). The rate of changes of the betaAR density was not correlated with the "before"-"after" interval, and the affinity of the betaARs did not change throughout these CPBs. These findings demonstrate that: CPB alone does not affect cardiac betaARs, at least until the onset of EIVF or CCCA; CPB with EIVF induces rapid desensitization of cardiac betaARs; and CPB with CCCA induces rapid sensitization of cardiac betaARs. 相似文献
28.
29.
Hybrid Petri net (HPN) is an extension of the Petri net formalism, which enables us to handle continuous information in addition
to discrete information. Firstly, this paper demonstrates how biological pathways can be modeled by the integration of discrete
and continuous elements, with an example of the λ phage genetic switch system including induction and retroregulation mechanisms.
Although HPN allows intuitive modeling of biological pathways, some fundamental biological processes such as complex formation
cannot be represented with HPN. Thus, this paper next provides the formal definition of hybrid functional Petri net with extension
(HFPNe), which has high potential for modeling various kinds of biological processes. Cell Illustrator is a software tool
developed on the basis of the definition of HFPNe. Hypothesis creation by Cell Illustrator is demonstrated with the example
of the cyanobacterial circadian gene clock system. Finally, our ongoing tasks, which include the development of a computational
platform for systems biology, are presented. 相似文献
30.
Tabu search for attribute reduction in rough set theory 总被引:2,自引:0,他引:2
Abdel-Rahman Hedar Jue Wang Masao Fukushima 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2008,12(9):909-918
In this paper, we consider a memory-based heuristic of tabu search to solve the attribute reduction problem in rough set theory.
The proposed method, called tabu search attribute reduction (TSAR), is a high-level TS with long-term memory. Therefore, TSAR
invokes diversification and intensification search schemes besides the TS neighborhood search methodology. TSAR shows promising
and competitive performance compared with some other CI tools in terms of solution qualities. Moreover, TSAR shows a superior
performance in saving the computational costs. 相似文献