全文获取类型
收费全文 | 1633篇 |
免费 | 87篇 |
国内免费 | 16篇 |
专业分类
电工技术 | 99篇 |
综合类 | 10篇 |
化学工业 | 547篇 |
金属工艺 | 35篇 |
机械仪表 | 65篇 |
建筑科学 | 86篇 |
矿业工程 | 9篇 |
能源动力 | 64篇 |
轻工业 | 182篇 |
水利工程 | 8篇 |
石油天然气 | 15篇 |
无线电 | 72篇 |
一般工业技术 | 299篇 |
冶金工业 | 59篇 |
原子能技术 | 76篇 |
自动化技术 | 110篇 |
出版年
2024年 | 9篇 |
2023年 | 31篇 |
2022年 | 52篇 |
2021年 | 73篇 |
2020年 | 38篇 |
2019年 | 30篇 |
2018年 | 41篇 |
2017年 | 37篇 |
2016年 | 50篇 |
2015年 | 33篇 |
2014年 | 35篇 |
2013年 | 120篇 |
2012年 | 84篇 |
2011年 | 116篇 |
2010年 | 74篇 |
2009年 | 73篇 |
2008年 | 72篇 |
2007年 | 80篇 |
2006年 | 62篇 |
2005年 | 55篇 |
2004年 | 40篇 |
2003年 | 55篇 |
2002年 | 60篇 |
2001年 | 39篇 |
2000年 | 35篇 |
1999年 | 28篇 |
1998年 | 33篇 |
1997年 | 22篇 |
1996年 | 28篇 |
1995年 | 22篇 |
1994年 | 21篇 |
1993年 | 22篇 |
1992年 | 15篇 |
1991年 | 8篇 |
1990年 | 7篇 |
1989年 | 5篇 |
1988年 | 9篇 |
1987年 | 9篇 |
1986年 | 8篇 |
1985年 | 10篇 |
1984年 | 15篇 |
1983年 | 13篇 |
1982年 | 6篇 |
1981年 | 9篇 |
1980年 | 6篇 |
1979年 | 9篇 |
1978年 | 7篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1968年 | 3篇 |
排序方式: 共有1736条查询结果,搜索用时 12 毫秒
1.
Rinji Akada Yoshirou Shimizu Yuji Matsushita Miho Kawahata Hisashi Hoshida Yoshinori Nishizawa 《Yeast (Chichester, England)》2002,19(1):17-28
Drug-resistance markers for yeast transformation are useful because they can be applied to strains without auxotrophic mutations. However, they are susceptible to technical difficulties, namely lower transformation efficiency and the appearance of drug-resistant mutants without the marker. To avoid these problems, we have constructed a phosphoglycerate kinase (PGK) promoter-driven YAP1 expression cassette, called PGKp-YAP1. Yeast cells containing PGKp-YAP1 were resistant to cycloheximide, a protein synthesis inhibitor, and also to cerulenin, a fatty acid synthesis inhibitor, but not to other drugs tested. The transformation efficiency of PGKp-YAP1 using cerulenin selection was comparable to that using a URA3 auxotrophic marker when low concentrations of cerulenin were used. Non-transformed drug-resistant colonies did appear on the low-concentration cerulenin plates. However, these non-transformed colonies could easily be identified, based on their cycloheximide sensitivity and/or their resistance to aureobasidin A to which the transformants were sensitive. Therefore, the dual drug resistance of PGKp-YAP1 could be used as an effective selection for PGKp-YAP1 recipient cells. The PGKp-YAP1 marker was used to disrupt the LYS2 gene and to transform an industrial yeast strain, indicating that this marker can be used for efficient and reliable gene manipulations in any Saccharomyces cerevisiae strain. 相似文献
2.
In recent years, ultrasonic motors (USM) as new actuators have attracted special interest. Several kinds of constructions and characteristics of USMs have been reported so far. Of these USMs, a traveling wave-type USM has many characteristics such as: high torque in the low-speed range, large holding torque based upon frictional force, flexible free forms, compactness in size and low magnetic noise. In practice, an inherent mechanical resonant frequency and a velocity amplitude of USM are changed largely according to operating temperature due to frictional drive, load disturbance torque, and applied voltage levels. Therefore, it is necessary to develop a new control system which solves these items and always supplies the required power with high efficiency and high performance in the practical applications. This paper proposes mainly a new sensorless high-performance control scheme of an inverter-fed ultrasonic motor, which is based on a control system technology with two feedbacks incorporating automatic resonant frequency tracking and constant velocity amplitude control strategies. This control system is realized in terms of a high-frequency chopper and a two-phase series/parallel resonant inverter. The experimental results are demonstrated and discussed compared with the theoretical ones. 相似文献
3.
A novel elastic polymer containing 4,4′-bipyridinium salts with tetrakis[3,5-bis(trifluoromethyl)phenyl]borate as part of the main chain was synthesized. The cast film showed persistent and reversible colour changes due to photoinduced electron transfer upon excitation of an ion-pair charge-transfer band (ex >365 nm) in vacuo. The lifetime of the coloured state markedly depended on temperature. The optically written data were stored without decay below 0°C and were erased thermally at elevated temperatures. The colour changes were reversibly repeatable for many times. 相似文献
4.
Motonobu Yoshikawa Hiroshi Nakajima Takeshi Inada Yasushi Harada Masahiko Amano Yuji Nakata 《Electrical Engineering in Japan》1995,115(7):29-39
A new practical method is proposed which gives a quasi-optimal solution of the dynamic load-dispatching problem formulated by a multiconstraint multiobjective optimization problem. Here, the multiple constraints are rate reserve constraints and power flow ones, and the multiple objectives are fuel cost and CO2 emission. The proposed method is an integration of the following three techniques: (1) “Group Dispatch Scheme,” which is developed by the authors, is used to satisfy a violated constraint easily. This scheme consists of three steps. The first step is to classify all generators into two groups. One is the group which should be more loaded to satisfy the violated constraint, and the other is the should-be less loaded group. The second step is to add some load to the former group, and to subtract the same load from the latter. The third step is to dispatch each group load to each groups generators, respectively; (2) the dynamic load-dispatching algorithm is used which provides, in practical time, quasi-optimal generation trajectories; (3) the conventional weighting parametric method is used to obtain a Pareto optimal solution of multiobjective problems. The effectiveness of the method is clarified by a computer simulation on the actual power system of Kansai Electric Power Company. 相似文献
5.
An addition reaction of maleic anhydride with polypropylene takes place in the presence of radical reagents or sunlight. The initial rate of the reaction was proportional to the concentration of polypropylene and maleic anhydride, and one-half power of the concentration of the radical reagents. The increase in the temperature from 80 to 120°C increased the rate of the reaction and di-cumyl peroxide was effective as a radical reagent for this reaction. Ionic crosslinked rubber-like polymers were obtained from the reaction of maleic polypropylene with some alkali metal compounds. They showed the characteristic absorption band due to ? COO? in their infrared spectra. 相似文献
6.
Extension of the applicable range of the implicit curve-fitting method for refrigerant thermodynamic properties to critical pressure 总被引:2,自引:1,他引:2
Guo Liang Ding Zhigang Wu Kaijian Wang Masaharu Fukaya 《International Journal of Refrigeration》2007,30(3):418-432
The method of implicit curve-fitting and explicit-calculation has been used for fast and stable calculations of thermodynamic properties of subcritical refrigerants. In order to extend that method to the critical pressure, a method of sectional implicit curve-fitting and explicit-calculation for refrigerant thermodynamic properties is introduced in this paper. The whole data range is divided into several subsections. The requirements on the continuity of thermodynamic properties and the first order derivative of thermodynamic properties in the intersection points of subsections are indicated, and the methods to meet the requirements are presented. Quadric equations are constructed instead of curve-fitting when no data can be given. With the source data obtained from REFPROP 7.1, explicit fast calculation formulae for thermodynamic properties of R410A, covering the saturated temperature of 213.15–344.51 K and superheat of 0–65 K, are given as an example. The calculation speeds of the formulae of R410A are more than 7000 times faster than those of REFPROP 7.1 while the total mean relative deviation of the fast calculation formulae from REFPROP 7.1 is only 0.04%. 相似文献
7.
Atsushi Kanamori Fumio Tanaka Masaki Ominami Yuji Nadatani Shusei Fukunaga Koji Otani Shuhei Hosomi Noriko Kamata Yasuaki Nagami Koichi Taira Yasuhiro Fujiwara 《International journal of molecular sciences》2022,23(15)
The effects of psychological stress on eosinophilic gastrointestinal disorders have not been elucidated. This study investigated the effects of psychological stress in a mouse model of eosinophilic enteritis (EoN). BALB/c mice were treated with ovalbumin (OVA) to create an EoN model and subjected to either water avoidance stress (WAS) or sham stress (SS). Microscopic inflammation, eosinophil and mast cell counts, mRNA expression, and protein levels of type 2 helper T cell (Th2) cytokines in the ileum were compared between groups. We evaluated ex vivo intestinal permeability using an Ussing chamber. A corticotropin-releasing hormone type 1 receptor (CRH-R1) antagonist was administered before WAS, and its effects were analyzed. WAS significantly increased diarrhea occurrence and, eosinophil and mast cell counts, and decreased the villus/crypt ratio compared to those in the SS group. The mRNA expression of CRH, interleukin IL-4, IL-5, IL-13, eotaxin-1, and mast cell tryptase β2 significantly increased, and the protein levels of IL-5, IL-13, and OVA-specific immunoglobulin E (IgE) also significantly increased in the WAS group. Moreover, WAS significantly increased the intestinal permeability. The CRH-R1 antagonist significantly inhibited all changes induced by WAS. Psychological stress exacerbated ileal inflammation via the CRH-mast cell axis in an EoN mouse model. 相似文献
8.
9.
Hasegawa Y Durstberger-Rennhofer K Sponar S Rauch H 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2011,634(1):S21-S24
The Kochen-Specker theorem shows the incompatibility of noncontextual hidden variable theories with quantum mechanics. Quantum contextuality is a more general concept than quantum non-locality which is quite well tested in experiments using Bell inequalities. Within neutron interferometry we performed an experimental test of the Kochen-Specker theorem with an inequality, which identifies quantum contextuality, by using spin-path entanglement of single neutrons. Here entanglement is achieved not between different particles, but between degrees of freedom of a single neutron, i.e., between spin and path degree of freedom. Appropriate combinations of the spin analysis and the position of the phase shifter allow an experimental verification of the violation of an inequality derived from the Kochen-Specker theorem. The observed violation 2.291±0.008?1 clearly shows that quantum mechanical predictions cannot be reproduced by noncontextual hidden variable theories. 相似文献
10.
This work compares the intercalation of K, Na, and Li in KxVPO4F (x ~ 0). The KxVPO4F (x ~ 0) cathode delivers reversible capacities of ≈90–100 mAh g?1 in K, Na, and Li cells, at an average voltage of ≈4.33 V for K, ≈3.98 V for Na, and ≈3.96 V for Li. This is so far the highest average voltage known for a K‐intercalation cathode. The lower voltage of Li insertion compared to Na is attributable to undercoordinated Li ions in the KxVPO4F (x ~ 0) framework. While the material shows high rate capability for all the alkali ions, Li migration in KxVPO4F (x ~ 0) is more difficult than with Na and K. This work suggests that a large cavity is not always good for insertion of alkali ions and cathode materials need to be suitably tailored to each intercalating ion species. 相似文献