全文获取类型
收费全文 | 2170篇 |
免费 | 43篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 45篇 |
综合类 | 8篇 |
化学工业 | 333篇 |
金属工艺 | 58篇 |
机械仪表 | 43篇 |
建筑科学 | 35篇 |
矿业工程 | 8篇 |
能源动力 | 36篇 |
轻工业 | 165篇 |
水利工程 | 10篇 |
石油天然气 | 4篇 |
无线电 | 233篇 |
一般工业技术 | 376篇 |
冶金工业 | 569篇 |
原子能技术 | 48篇 |
自动化技术 | 244篇 |
出版年
2023年 | 13篇 |
2022年 | 26篇 |
2021年 | 34篇 |
2020年 | 17篇 |
2019年 | 17篇 |
2018年 | 19篇 |
2017年 | 20篇 |
2016年 | 41篇 |
2015年 | 26篇 |
2014年 | 40篇 |
2013年 | 100篇 |
2012年 | 72篇 |
2011年 | 98篇 |
2010年 | 85篇 |
2009年 | 73篇 |
2008年 | 71篇 |
2007年 | 71篇 |
2006年 | 51篇 |
2005年 | 62篇 |
2004年 | 58篇 |
2003年 | 42篇 |
2002年 | 48篇 |
2001年 | 42篇 |
2000年 | 28篇 |
1999年 | 45篇 |
1998年 | 180篇 |
1997年 | 77篇 |
1996年 | 88篇 |
1995年 | 67篇 |
1994年 | 47篇 |
1993年 | 45篇 |
1992年 | 29篇 |
1991年 | 34篇 |
1990年 | 42篇 |
1989年 | 41篇 |
1988年 | 31篇 |
1987年 | 14篇 |
1986年 | 20篇 |
1985年 | 28篇 |
1984年 | 20篇 |
1983年 | 13篇 |
1982年 | 17篇 |
1981年 | 16篇 |
1980年 | 13篇 |
1978年 | 14篇 |
1977年 | 17篇 |
1976年 | 36篇 |
1975年 | 12篇 |
1974年 | 12篇 |
1973年 | 18篇 |
排序方式: 共有2215条查询结果,搜索用时 15 毫秒
61.
I. Zeiringer N. Melnychenko-Koblyuk A. Grytsiv E. Bauer G. Giester P. Rogl 《Journal of Phase Equilibria and Diffusion》2011,32(2):115-127
In the Au-Ba-Ge system the clathrate type I solid solution, Ba8Au
x
Ge46−x−y
□
y
, extends at 800 °C from binary Ba8Ge43□3 (□ is a vacancy) to Ba8Au6Ge40. For the clathrate phase (1 ≤ x ≤ 6) cubic primitive symmetry (space group Pm[`3]n Pm{\bar{{3}}}n ) was confirmed by x-ray powder diffraction assisted by x-ray single crystal analyses of Ba8Au4.6Ge40.3□1.1. The lattice parameters of the solid solution show an almost linear increase with increasing gold content. Site preference
from x-ray refinement shows that gold atoms preferably occupy the 6d site in random mixture with Ge and vacancies, which vanish
at the solubility limit. Clathrate type ΙX (Ba6Ge25 type) has a maximum solubility of 2.7 at.% gold at 800 °C. Phase equlilibria at 800 °C are characterized by four ternary
phases in the investigated region up to 33.3 at.% barium. The homogeneity range of Ba(Au1−x
Ge
x
)2 (AlB2-type) and BaAu1+x
Ge3−x
has been established: Ba(Au1−x
Ge
x
)2 extends from BaAu0.5Ge1.5 to BaAu0.9Ge1.1 and BaAu1+x
Ge3−x
from BaAu1.1Ge2.9 (BaNiSn3-type) to BaAu2.7Ge1.3 (Ce(Ni,Sb)4-type). The crystal structures of two phases in the gold-rich part have been determined from single crystal x-ray data and
were found to form new structure types: BaAu3Ge with BaAu3Ge-type (space group P4/nmm, a = 0.6459(2), c = 0.5487(2) nm) and BaAu5+x
Ge2−x
(x = 0, BaAu5Si2-type, space group Pnma, a = 0.8981(2), b = 0.7106(2) and c = 1.0363(2) nm), the latter revealing with increasing gold content a closely related derivative structure type (BaAu5.3Ge1.7,
a = a\textBaAu5 \textSi2 , b = b\textBaAu5 \textSi2 , c = 2c\textBaAu5 \textSi2 a = a_{{{\text{BaAu}}_{5} {\text{Si}}_{2} }} ,\;b = b_{{{\text{BaAu}}_{5} {\text{Si}}_{2} }} ,\;c = 2c_{{{\text{BaAu}}_{5} {\text{Si}}{}_{2}}} ). Transport properties and particularly the thermoelectric behavior were studied for Ba8Au6Ge40. 相似文献
62.
Information about electron-transfer reactions of dissolved organic matter (DOM) is lacking. We determined electron acceptor and donor capacities (EAC and EDC) of a peat humic acid and an untreated peat DOM by electrochemical reduction and reduction with metallic Zn and H2S (EAC), and by oxidation with complexed ferric iron (EDC) at pH 6.5. DOC concentrations (10-100 mg L(-1)) and pH values (4.5-8) were varied in selected experiments. EAC reached up to 6.2 mequiv x (g C)(-1) and EDC reached up to 1.52 mequiv-(g C)(-1). EDC decreased with pH and conversion of chelated to colloidal iron, and the electron-transfer capacity (ETC) was controlled by the redox potential Eh of the reactant (ETC = 1.016x Eh - 0.138; R(2) = 0.87; p = 0.05). The kinetics could be adequately described by pseudo first-order rate laws, one or two DOM pools, and time constants ranging from 2.1 x 10(-3) d-1 to 1.9 x 10(-2) d(-1) for the fast pool. Reactions were completed after 24-160 h depending on the redox couple applied. The results indicate that DOM may act as a redox buffer over electrochemical potentials ranging from -0.9 to +1.0 V. 相似文献
63.
The paper describes a model and a simple experimental method to determine suspension transport properties, separating the role of particles from the suspending fluid. Shear stresses are described as consisting of 2 components: 1st, a shear stress caused by the flow of the suspending fluid and 2nd, a shear stress caused by direct interaction between suspended particles. We show that the determination of these shear stresses of a complex (food) suspension is largely independent of the definition of its suspending fluid. The rheological behavior of soy milks at low and intermediate moisture contents was studied, and results are compared with those obtained previously. The method evidences that the high viscosity of soy milks is predominantly caused by direct particle interaction. 相似文献
64.
O. Kolditz S. Bauer N. Böttcher D. Elsworth U.-J. Görke C.-I. McDermott C.-H. Park A.K. Singh J. Taron W. Wang 《Mathematics and computers in simulation》2012
In this paper, conceptual modeling as well as numerical simulation of two-phase flow in deep, deformable geological formations induced by CO2 injection are presented. The conceptual approach is based on balance equations for mass, momentum and energy completed by appropriate constitutive relations for the fluid phases as well as the solid matrix. Within the context of the primary effects under consideration, the fluid motion will be expressed by the extended Darcy's law for two phase flow. Additionally, constraint conditions for the partial saturations and the pressure fractions of carbon dioxide and brine are defined. To characterize the stress state in the solid matrix, the effective stress principle is applied. Furthermore, the interaction of fluid and solid phases is illustrated by constitutive models for capillary pressure, porosity and permeability as functions of saturation. Based on this conceptual model, a coupled system of nonlinear differential equations for two-phase flow in a deformable porous matrix (H2M model) is formulated. As the displacement vector acts as primary variable for the solid matrix, multiphase flow is simulated using both pressure/pressure or pressure/saturation formulations. An object-oriented finite element method is used to solve the multi-field problem numerically. The capabilities of the model and the numerical tools to treat complex processes during CO2 sequestration are demonstrated on three benchmark examples: (1) a 1-D case to investigate the influence of variable fluid properties, (2) 2-D vertical axi-symmetric cross-section to study the interaction between hydraulic and deformation processes, and (3) 3-D to test the stability and computational costs of the H2M model for real applications. 相似文献
65.
Matthew J. Bauer Catherine S. Snyder Christopher C. Bowland Amanda M. Uhl Maeve A. K. Budi Maria Villancio‐Wolter Henry A. Sodano Jennifer S. Andrew 《Journal of the American Ceramic Society》2016,99(12):3902-3908
Barium titanate nanofibers were uniaxially aligned by electrospinning onto a rotating copper wire drum and alignment was maintained during calcination of the fibers. Two methods for maintaining alignment during calcination were tested, by either using carbon tape or a peeling off method to remove the aligned fibers from the mandrel followed by calcination. The carbon tape removal method led to the formation of shorter aligned nanowires while the peeling off method resulted in longer nanofibers. Additionally, the effects of calcination temperature and time on crystal structure were also examined. The degree of tetragonality in the barium titanate nanofibers increased at higher calcination temperatures and times. Piezoelectricity was confirmed in the nanofibers calcined using piezoeresponse force microscopy, yielding a d33 value of 15.5 pm/V. Using the methods presented here, large quantities of aligned piezoelectric barium titanate and other ceramic fibers or wires can be produced to fulfill their demand in novel microelectronics. 相似文献
66.
Tama Dinur Peter Bauer Christian Beetz Guido Kramp Claudia Cozma Marius-Ionu Iuracu Michal Becker-Cohen Majdolen Istaiti Arndt Rolfs Ari Zimran Shoshana Revel-Vilk 《International journal of molecular sciences》2022,23(3)
For years, the gold standard for diagnosing Gaucher disease (GD) has been detecting reduced β-glucocerebrosidase (GCase) activity in peripheral blood cells combined with GBA1 mutation analysis. The use of dried blood spot (DBS) specimens offers many advantages, including easy collection, the need for a small amount of blood, and simpler transportation. However, DBS has limitations for measuring GCase activity. In this paper, we recount our cross-sectional study and publish seven years of experience using DBS samples and levels of the deacylated form of glucocerebroside, glucosylsphingosine (lyso-Gb1), for GD diagnosis. Of 444 screened subjects, 99 (22.3%) were diagnosed with GD at a median (range) age of 21 (1–78) years. Lyso-Gb levels for genetically confirmed GD patients vs. subjects negative to GD diagnosis were 252 (9–1340) ng/mL and 5.4 (1.5–16) ng/mL, respectively. Patients diagnosed with GD1 and mild GBA1 variants had lower median (range) lyso-Gb1, 194 (9–1050), compared to GD1 and severe GBA1 variants, 447 (38–1340) ng/mL, and neuronopathic GD, 325 (116–1270) ng/mL (p = 0.001). Subjects with heterozygous GBA1 variants (carrier) had higher lyso-Gb1 levels, 5.8 (2.5–15.3) ng/mL, compared to wild-type GBA1, 4.9 (1.5–16), ng/mL (p = 0.001). Lyso-Gb1 levels, median (range), were 5 (2.7–10.7) in heterozygous GBA1 carriers with Parkinson’s disease (PD), similar to lyso-Gb1 levels in subjects without PD. We call for a paradigm change for the diagnosis of GD based on lyso-Gb1 measurements and confirmatory GBA1 mutation analyses in DBS. Lyso-Gb1 levels could not be used to differentiate between heterozygous GBA1 carriers and wild type. 相似文献
67.
P. R. Gentner I. Dieterich M. Bauer 《European Journal of Lipid Science and Technology》1982,84(1):15-17
Column Chromatographic Separation of Phospholipids from Total Lipid Extracts The separation of phospholipids out of total lipid extracts is described by using a column chromatographic method. Up to 800 mg total lipids in a mixture of chloroform and methanol (19 : 1, v/v) may be applied to dry-column-chromatography using 5 g silica gel as a matrix. Neutral lipids and free fatty acids are elutet by propanol-2. Following extraction of phospholipids is achieved by methanol, containing 0.5 ml/100 ml ammonia solution (25%). In the course of the preparation no lyso-phospholipids are formed and the composition of the phospholipidfraction is not altered. The recovery of applied phospholipids amounts 98-99.5%. 相似文献
68.
K. Täufel H. Thaler und O. Bauer 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1935,69(5):401-405
Ohne Zusammenfassung 相似文献
69.
This introduces an organic–inorganic thermosetting hybrid resin system based on unsaturated polyester and polysilazanes. It shows the chemical modification of unsaturated polyester structures by end capping to enable the combination of both components. In general, halogen‐free unsaturated polyesters are not fire‐retardant and have to be equipped with additives. Fillers and intumescent additives are preponderantly used in today's fire‐retardant formulations. In contrast to these fire‐retardants, polysilazanes act as ceramizing agents. Polysilazanes are suitable fire‐retardants for resin transfer molding due to their low viscosity. Both burning behavior and glass transition temperature (Tg) are investigated as important application properties. In contrast to state‐of‐the‐art fire‐retardant formulations polysilazane‐based thermosetting hybrid resins burn with high intensity and fast extinction. Therefore, total heat and smoke emission is decreased. The formation of ceramic structures during burning results in high residual mechanical properties and a low mass loss. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40375. 相似文献
70.