全文获取类型
收费全文 | 5314篇 |
免费 | 120篇 |
国内免费 | 27篇 |
专业分类
电工技术 | 418篇 |
综合类 | 17篇 |
化学工业 | 1507篇 |
金属工艺 | 137篇 |
机械仪表 | 142篇 |
建筑科学 | 190篇 |
矿业工程 | 1篇 |
能源动力 | 245篇 |
轻工业 | 513篇 |
水利工程 | 19篇 |
石油天然气 | 7篇 |
无线电 | 293篇 |
一般工业技术 | 951篇 |
冶金工业 | 217篇 |
原子能技术 | 215篇 |
自动化技术 | 589篇 |
出版年
2023年 | 30篇 |
2022年 | 59篇 |
2021年 | 96篇 |
2020年 | 52篇 |
2019年 | 64篇 |
2018年 | 75篇 |
2017年 | 63篇 |
2016年 | 114篇 |
2015年 | 81篇 |
2014年 | 152篇 |
2013年 | 324篇 |
2012年 | 187篇 |
2011年 | 308篇 |
2010年 | 260篇 |
2009年 | 281篇 |
2008年 | 318篇 |
2007年 | 269篇 |
2006年 | 206篇 |
2005年 | 222篇 |
2004年 | 180篇 |
2003年 | 163篇 |
2002年 | 167篇 |
2001年 | 107篇 |
2000年 | 98篇 |
1999年 | 100篇 |
1998年 | 116篇 |
1997年 | 84篇 |
1996年 | 81篇 |
1995年 | 59篇 |
1994年 | 84篇 |
1993年 | 74篇 |
1992年 | 58篇 |
1991年 | 77篇 |
1990年 | 53篇 |
1989年 | 78篇 |
1988年 | 68篇 |
1987年 | 41篇 |
1986年 | 74篇 |
1985年 | 58篇 |
1984年 | 54篇 |
1983年 | 57篇 |
1982年 | 61篇 |
1981年 | 48篇 |
1980年 | 42篇 |
1979年 | 41篇 |
1978年 | 42篇 |
1977年 | 28篇 |
1976年 | 29篇 |
1975年 | 18篇 |
1973年 | 17篇 |
排序方式: 共有5461条查询结果,搜索用时 12 毫秒
131.
Rosiah Rohani Tetsuya Yamaki Hiroshi Koshikawa Shin Hasegawa Yasunari Maekawa Christina Trautmann 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2009,267(3):554-557
We investigated how pretreatment and high-LET beam irradiation affected the ion-track dissolution rate in poly(vinylidene fluoride) (PVDF) films by SEM observations and conductometric analysis in order to develop the preparation methodology of nano-sized ion-track membranes. PVDF thin films irradiated with four types of ion beams were exposed to a 9 mol/dm3 KOH aqueous solution after their storage in air at 120 °C. This heating treatment was found to enhance the etch rate in the latent track, both in the inner core and outer halo regions, without changing that in the bulk, probably due to the formation of parasitic oxidation products facilitating the introduction of the etching agent to improve the etchability. Additionally, the irradiation of heavier higher-LET ions, causing each track to more activated sites (like radicals), was preferable for achieving effective etching. 相似文献
132.
Tomoya Hasegawa Mikako Ito Satoru Hasegawa Masaki Teranishi Koki Takeda Shuto Negishi Hiroshi Nishiwaki Jun-ichi Takeda Tyler W. LeBaron Kinji Ohno 《International journal of molecular sciences》2022,23(5)
Molecular hydrogen ameliorates pathological states in a variety of human diseases, animal models, and cell models, but the effects of hydrogen on cancer have been rarely reported. In addition, the molecular mechanisms underlying the effects of hydrogen remain mostly unelucidated. We found that hydrogen enhances proliferation of four out of seven human cancer cell lines (the responders). The proliferation-promoting effects were not correlated with basal levels of cellular reactive oxygen species. Expression profiling of the seven cells showed that the responders have higher gene expression of mitochondrial electron transport chain (ETC) molecules than the non-responders. In addition, the responders have higher mitochondrial mass, higher mitochondrial superoxide, higher mitochondrial membrane potential, and higher mitochondrial spare respiratory capacity than the non-responders. In the responders, hydrogen provoked mitochondrial unfolded protein response (mtUPR). Suppression of cell proliferation by rotenone, an inhibitor of mitochondrial ETC complex I, was rescued by hydrogen in the responders. Hydrogen triggers mtUPR and induces cell proliferation in cancer cells that have high basal and spare mitochondrial ETC activities. 相似文献
133.
Yi Liu Toyoki Fujiwara Hiroshi Yukawa Masahiko Morinaga 《Solar Energy Materials & Solar Cells》2000,62(1-2)
Employing the DV-Xα molecular orbital method, lithium intercalation effect and alloying effect have been investigated on the electronic structures of spinel MxMn2−xO4 and LiMxMn2−xO4 (M=Ti, V, Cr, Mn, Fe, Co, Ni and Cu). It is found that the lithium intercalation induces the electron transfer from Li to the surrounding O ions, and enlarges the Mn-3d/O-2p band gap greatly. Such a modification of the oxygen electronic state is probably related to the electrochemical cell voltage. This lithium intercalation effect still holds even in the alloyed systems. However, the amount of transferred charges from M to O ions changes depending on the alloying element, M. So the alloying addition modifies the oxygen electronic state and influences the lithium intercalation process indirectly. 相似文献
134.
Toshihiko Hirama Masashi Goto Keiji Shiba Toshio Kobayashi Ryozo Tanaka Shizuo Tsurumaki Katsuki Takiguchi Hiroshi Akiyama 《Nuclear Engineering and Design》2005,235(13):7
A 1/8-scale model was constructed of a reinforced concrete containment vessel (RCCV) used in the latest advanced boiling water reactors (ABWR). Shaking table tests were conducted on it with input motions corresponding to or exceeding a design earthquake assumed for a real Nuclear Power Plant.The objectives of the tests were to verify the structural integrity and the leak-proof functional soundness of the RCCV subjected to design earthquakes, and to determine the ultimate strength and seismic margin by an excitation that led to the model's collapse. The model, the test sequence and the pressure and leak test results were addressed in Part 1. The shaking table test method, the input motions and the test results, including the transition of the model's stiffness, natural frequencies and damping factors and the effects of vertical input motions and internal pressure on the model's characteristics and behavior, the load–deformation, the ultimate strength, the failure mode of the reinforced concrete portion and the liner plate are described here. The seismic safety margin that was evaluated by the energy input during the failure test to a design basis earthquake will be described in Part 3. The analytical results of simulation using the multi-lumped mass model will be described in Part 4. 相似文献
135.
Rei Kimura Hiroshi Sagara Satoshi Chiba 《Journal of Nuclear Science and Technology》2016,53(12):1978-1987
We have developed a new nondestructive assay technique based on the photonuclear reaction, which is aimed at measuring the isotopic composition of nuclear fuel materials without relying on their self-generated neutron information. This methodology enables measurement of the number of neutrons produced by the photofission reactions at different specific photon energies, and only information on the relative counts and not the absolute values or energies, which are considerably affected by backgrounds, are required for the enrichment induction according to a mathematical process. The present methodology estimated the 235U enrichment value with 8% accuracy when the cross section uncertainty is 5%. 相似文献
136.
The similarity between two nuclear systems is expressed by the representativity factors and maximizing its value to unity reduces the uncertainty from its existing value. As the representativity factor is a function of covariance matrix of neutron cross-sections, the inherent systematic uncertainty in neutron cross-sections inhibits it from approaching unity and hence statistical procedures have to be resorted to minimize the systematic uncertainty. As the conventional statistical techniques fail when systematic uncertainty is dominant, we propose an entropy based information theoretic approach of maximizing the mutual information by the knowledge of bounds for the correlated elements. We show that maximizing the mutual information and the representativity factors express the similar phenomena of uncertainty reduction. We estimated the bounds for the correlated elements of the correlation matrix for minor actinides and show how the systematic uncertainty is reduced when lower bound values are considered. These lower bound values aid in experimental planning for future measurement of cross-sections with reduced systematic uncertainty. 相似文献
137.
Hiroshi Noguchi 《世界建筑导报》2019,(4)
<正>香港部屋座落在日本新潟县中鱼沼郡津南町内的一个村落里。津南的上乡被大自然紧紧包围着,是一个有大树,有小草,充满着雪国风貌的青葱之地。为了不打扰这份自然和宁静,LAAB以融入作为设计理念,希望香港部屋成为这个村落的一部分。屋顶微微倾侧,和村落中此起彼落的民居建筑物互相呼应。LAAB用新潟当地的鱼沼杉木和常见的镀铁板 相似文献
138.
Chonan T Fujimoto T Inoue M Tazawa T Ogawa H 《Shokuhin eiseigaku zasshi. Journal of the Food Hygienic Society of Japan》2008,49(3):244-248
A simple and rapid multiresidue method was developed for the determination of twelve quinolones (ciprofloxacin, danofloxacin, difloxacin, enrofloxacin, flumequine, marbofloxacin, nalidixic acid, norfloxacin, ofloxacin, orbifloxacin, oxolinic acid and sarafloxacin) in muscle, liver, chicken eggs, milk, prawn and rainbow trout.The quinolones were extracted from a sample with acetonitrile-water (95 : 5). A fifth part of the filtered extract was diluted with water to keep the acetonitrile ratio at ca. 60%, and passed through a C18 mini-column. The eluate was evaporated to dryness, and the residues were dissolved in methanol-water (30 : 70) for HPLC analysis.The quinolones were separated on a Inertsil ODS-3V column (4.6 mm i.d.x250 mm) with a gradient system of 0.1% phosphoric acid-acetonitrile as the mobile phase, with fluorescence detection.No interfering peak was found on the chromatograms of animal and fishery products, except for milk. The recoveries of the quinolones were over 60% from the animal and fishery products fortified at 0.1 microg/g, and the quantification limits of the quinolones were 0.005 microg/g. This proposed method was found to be effective and suitable for the screening of the quinolones in animal and fishery products. 相似文献
139.
Bonding a fiber reinforced polymer (FRP) sheet to the tension-side surface of reinforced concrete (RC) structures is often performed to upgrade the flexural capacity and stiffness. Except for upper concrete crushing, FRP sheet reinforcing RC structure may fail in sheet rupture, sheet peeloff failure due to opening of a critical diagonal crack, or concrete cover delamination failure from the sheet end. Accompanying the occurrence of these failure modes, reinforcing effects of the FRP sheet will be lost and load-carrying capacity of the RC structures will be decreased suddenly. This study is devoted to developing a numerical analysis method by using a three-dimensional elasto-plastic finite element method to simulate the load-carrying capacity of RC beams failed in the FRP sheet peeloff mode. Here, the discrete crack approach was employed to consider geometrical discontinuities such as opening of cracks, slipping of rebar, and debonding of the FRP sheet. Comparisons between analytical and experimental results confirm that the proposed numerical analysis method is appropriate for estimating the load-carrying capacity and failure behavior of RC beams flexurally reinforced with a FRP sheet. 相似文献
140.
Addition of [FeII(MeCN)24+(ClO−4)2 to solutions of hydrogen peroxide in dry acetonitrile (MeCN) catalyzes a rapid disproportionation of H2O2 via the initial formation of an adduct, [FeII(HOOH)↔Fe(O)(OH2)]2+, which oxidizes a second H2O2 to dioxygen. This intermediate also cleanly oxidizes substituted hydrazines, alcohols, aldehydes, and thioethers by a two-electron process. The products for these H2O2 oxidations are consistent with those that result from catalase- and some peroxidase-catalyzed processes. In the same aprotic medium (MeCN) anhydrous FeIIICl3 catalyzes the demethylation of N,N-dimethylaniline, the epoxidation of olefins, and the oxidative cleavage of 1-phenyl-1,2-ethanediol (and other 1,2-diols) by hydrogen peroxide. A mechanism is proposed in which an initial Lewis acid-base interaction of FeIIICl3 with H2O2 generates a highly electrophilic FeIII-oxene species as the reactive intermediate. For each class of substrate the products closely parallel those that result from their enzymatic oxidation by cytochrome P-450. Because of (a) the close congruence of products, (b) the catalytic nature of the FeIIICl3/H2O2 reaction mimic, and (c) the similarity of the dipolar aprotic solvent (acetonitrile) to the proteinaceous lipid matrix of the biomembrane, the form of the reactive intermediate may be the same in each case. This is in contrast to the prevailing view that cytochrome P-450 acts as a redox catalyst to generate an Fe(V)-oxo species or an Fe(IV)-oxo cation radical as the reactive intermediate. 相似文献