全文获取类型
收费全文 | 5537篇 |
免费 | 229篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 139篇 |
综合类 | 13篇 |
化学工业 | 1425篇 |
金属工艺 | 117篇 |
机械仪表 | 104篇 |
建筑科学 | 431篇 |
矿业工程 | 10篇 |
能源动力 | 122篇 |
轻工业 | 751篇 |
水利工程 | 36篇 |
石油天然气 | 13篇 |
无线电 | 287篇 |
一般工业技术 | 919篇 |
冶金工业 | 637篇 |
原子能技术 | 58篇 |
自动化技术 | 711篇 |
出版年
2022年 | 44篇 |
2021年 | 69篇 |
2020年 | 55篇 |
2019年 | 58篇 |
2018年 | 66篇 |
2017年 | 85篇 |
2016年 | 114篇 |
2015年 | 137篇 |
2014年 | 149篇 |
2013年 | 249篇 |
2012年 | 227篇 |
2011年 | 242篇 |
2010年 | 208篇 |
2009年 | 224篇 |
2008年 | 217篇 |
2007年 | 250篇 |
2006年 | 202篇 |
2005年 | 203篇 |
2004年 | 183篇 |
2003年 | 125篇 |
2002年 | 135篇 |
2001年 | 111篇 |
2000年 | 99篇 |
1999年 | 77篇 |
1998年 | 87篇 |
1997年 | 85篇 |
1996年 | 82篇 |
1995年 | 75篇 |
1994年 | 55篇 |
1993年 | 78篇 |
1992年 | 80篇 |
1991年 | 53篇 |
1990年 | 62篇 |
1989年 | 61篇 |
1987年 | 71篇 |
1986年 | 58篇 |
1985年 | 72篇 |
1984年 | 65篇 |
1983年 | 61篇 |
1982年 | 63篇 |
1981年 | 68篇 |
1980年 | 67篇 |
1979年 | 68篇 |
1978年 | 51篇 |
1977年 | 54篇 |
1976年 | 57篇 |
1975年 | 56篇 |
1974年 | 67篇 |
1973年 | 49篇 |
1970年 | 41篇 |
排序方式: 共有5773条查询结果,搜索用时 31 毫秒
21.
In the following paper at first general concepts which have to be considered for the accomplishment of a 3D fatigue crack propagation simulation by the FE‐method in real structures are introduced. In doing so numerical aspects concerning the necessary mesh generation as well as fracture mechanical issues will be discussed. Furthermore the 3D crack simulation program ADAPCRACK3D, which has been developed at the Institute of Applied Mechanics at University of Paderborn, is presented in its general functionality. The simulation example of the crack propagation in a shutter ring of a hydraulic press shows the practical relevance of both the implemented algorithms and fracture mechanical concepts. 相似文献
22.
The exact magnetization pattern of magnetic films close to a spin-reorientation transition is difficult to analyze due to the intrinsically three-dimensional (3d) variation of the orientation of the local magnetization. We present a technique how this can be performed, based on the analysis of high quality 2d polarization maps from a single scanning electron microscope with polarization analysis (SEMPA) measurement with tilted sample. The key tool is the statistical distribution of all occurring polarization doublets, visualized in a 2d histogram plot. From the shape of the distribution the type of transition—canted-phase, or coexisting phases—can be inferred. For the canted-phase state, the canting angle can be accurately determined from geometrical considerations. With help of the histogram the image data can be analyzed and the three components of the magnetization can be calculated for most points of the image. For a Co/Pt multilayer film we found a cone state. The magnetization forms a complex pattern consisting of out-of-plane domains while the in-plane magnetization shows a maze pattern. 相似文献
23.
阿维斯塔波莱瑞特厂正在进行一个现代化改造项目,以提高炉卷轧机的生产能力,达到年产100万吨。但是,由于在阿维斯塔波莱瑞特厂炉卷轧机上的现有技术已达到极限,只有通过对轧机及自动化系统进行现代化的改造才有可能提高和增强轧机的利用率和易维护性。 相似文献
24.
OBJECTIVE: To study the effects of thevetoside (TS), a cardiac glycoside, and an inhibitor of Na+, K(+)-ATPase, on tumor cells cultured in vitro. METHODS: The cytotoxic effects of TS on tumor cells were determined by trypan blue dye exclusion, neutral red vital staining and clonogenic assay. The time-effect relationship and growth inhibition of tumor cells by TS were assayed with trypan blue exclusion method. RESULTS: TS at low doses (0.005-0.1 mg.L-1), with dose dependence, was able to kill SMMC-7721, SGC-7901 and HeLa cells. IC50 values for SMMC-7721, SGC-7901 and HeLa cells were 0.007, 0.011 and 0.018 mg.L-1 by trypan blue dye exclusion test and 0.016, 0.055 and 0.078 mg.L-1 by neutral red vital staining test. TS inhibited the clonal forming rate of SMMC-7721 and SGC-7901 significantly with IC50 values of 0.021 and 0.036 mg.L-1, respectively. Only when the cells were continuously treated with TS for more than 8 hours, the drug-induced cell lethality could be displayed and strengthened quickly. The growth of tumor cells was notably inhibited after they were exposed to 0.1 microgram/ml of TS for 12 hours. All the experimental results of antitumor activity in vitro showed that SMMC-7721 was most sensitive to TS among the three kinds of tumor cells. CONCLUSIONS: TS has cytotoxic action on tumor cells cultured in vitro and this lethal effect must have an action process, in which tumor cells are not dead but suffer from deadly injury and lost the capability of unlimited proliferation. 相似文献
25.
Emmanuel. Delamarche Bruno. Michel Hans A. Biebuyck Christoph Gerber 《Advanced materials (Deerfield Beach, Fla.)》1996,8(9):719-729
Self-assembled monolayers (SAMs) of alkanethiols and disulfides on gold form organic interfaces with properties largely controlled by the end groups of the molecules composing the film. SAMs provide a unique link between the science of organic surfaces and technologies that seek to exploit their adaptable character. Many techniques are useful for probing the structure of SAMs although only scanning tunneling microscopy (STM) at picoamperes reveals the details of the packing of their end groups at the sub-angstrom level. This review demonstrates that STM effectively tests new types of control over the microscopic structure–property relationships characteristic of SAMs on gold that should prove useful to their application. 相似文献
26.
The homopolyester of 4-(4′-hydroxyphenoxy)benzoic acid (poly(4-HPBA)), was prepared under two different reaction conditions and compared with a sample provided by another research group. Depending on the synthetic route, different melting points, d.s.c. traces and crystal lattices were found. However, after repeated heating and cooling, one thermodynamically stable modification with a melting point of 370–375°C can be obtained. Copolyesters of 4-hydroxybenzoic acid and 4-(4′-hydroxyphenoxy)benzoic acid were prepared with various molar ratios either in the melt (condensation in bulk) or in solution. These copolyesters were characterized by elemental analyses, 1H n.m.r. spectroscopy, d.s.c. measurements, wide-angle X-ray scattering measurements at various temperatures, and optical microscopy. Whereas copolyesters prepared in solution do not melt below 500°C, those prepared by polycondensation in bulk show melting points down to approximately 260°C and form a nematic melt. 相似文献
27.
Abderrafi M. Ougouag Jan Leen Kloosterman Wilfred F.G. van Rooijen Hans D. Gougar William K. Terry 《Nuclear Engineering and Design》2006,236(5-6):669-2004
Models and methods are presented for determining practical limits of the packing density of TRISO particles in fuel pebbles for a pebble-bed reactor (PBR). These models are devised for designing and interpreting fuel testing experiments. Two processes for particle failure are accounted for: failure of touching particles at the pressing stage in the pebble manufacturing process and failure due to inner pressure buildup during irradiation. The second process gains importance with increasing fuel temperature, which limits the particle packing density and the corresponding fuel enrichment. Suggestions for improvements to the models are presented. 相似文献
28.
Michael Maiwald Hongping Li Thorsten Schnabel Kay Braun Hans Hasse 《The Journal of Supercritical Fluids》2007,43(2):267
On-line NMR spectroscopy can beneficially be applied to studies of supercritical and near-critical fluids as an alternative to optical spectroscopy. Up to now high pressure NMR experiments are predominantly accomplished using custom made NMR batch reactors. The authors present a novel high pressure cell with displacement plunger for on-line NMR experiments on compressible fluids which can be used in conjunction with commercially available SCF NMR flow probes. The on-line technique offers advantages compared to stopped flow techniques such as enhanced control of mixture composition and reaction parameters as well as the facility of engagement into the reaction. The new apparatus is used for NMR studies on hydrogen bonding of methanol in near critical and supercritical carbon dioxide up to 403 K and 35 MPa for which data on the chemical shift of the hydroxyl group and methyl group are reported and interpreted. 相似文献
29.
Harrist R. Steven; Quintana Stephen M.; Strupp Hans H.; Henry William P. 《Canadian Metallurgical Quarterly》1994,31(1):49
[Correction Notice: An erratum for this article was reported in Vol 31(3) of Psychotherapy: Theory, Research, Practice, Training (see record 2009-17141-002). This article contained, as Figure 1, an SASB model. The authorship and copyrights for the model were not acknowledged. The following acknowledgement should have been included: "Adapted from Benjamin (1984). Principles of Prediction using Structural Analysis of Social Behavior (SASB). In R. A. Zucker, J. Aronoff, and A. J. Rabin (Eds.), Personality and the Prediction of Behavior (pp. 121- 174). New York: Academic." An apology is offered to the author, Dr. Lorna Smith Benjamin. The particular version used in the article was developed in collaboration with Clinton W. McLemore.] Investigated the internalization of positive aspects of therapist–patient (TP) interactions among 70 patients and their 16 therapists who participated in a 5-yr study (H. H. Strupp et al, unpublished) of time-limited dynamic psychotherapy. Patients sought help for anxiety, depression, or other problems with a clear interpersonal component and qualified for an Axis I or Axis II diagnosis on the Diagnostic and Statistical Manual of Mental Disorders-III (DSM-III). Instruments included the Structural Analysis of Social Behavior and outcome measures of depression, anxiety, and psychological functioning. Patients' intrapsychic functioning became more similar to interpersonal activity in the TP relationship over the course of psychotherapy. Intrapsychic movement toward interpersonal activity in the TP relationship was associated with positive outcome on measures of depression, anxiety, and on independent clinician ratings of patient psychological functioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
30.