全文获取类型
收费全文 | 31180篇 |
免费 | 1380篇 |
国内免费 | 130篇 |
专业分类
电工技术 | 506篇 |
综合类 | 281篇 |
化学工业 | 5207篇 |
金属工艺 | 830篇 |
机械仪表 | 692篇 |
建筑科学 | 862篇 |
矿业工程 | 155篇 |
能源动力 | 492篇 |
轻工业 | 4290篇 |
水利工程 | 242篇 |
石油天然气 | 135篇 |
武器工业 | 10篇 |
无线电 | 1603篇 |
一般工业技术 | 5663篇 |
冶金工业 | 7954篇 |
原子能技术 | 180篇 |
自动化技术 | 3588篇 |
出版年
2023年 | 314篇 |
2022年 | 279篇 |
2021年 | 646篇 |
2020年 | 524篇 |
2019年 | 450篇 |
2018年 | 914篇 |
2017年 | 833篇 |
2016年 | 928篇 |
2015年 | 821篇 |
2014年 | 945篇 |
2013年 | 1799篇 |
2012年 | 1400篇 |
2011年 | 1418篇 |
2010年 | 1191篇 |
2009年 | 1116篇 |
2008年 | 1293篇 |
2007年 | 1206篇 |
2006年 | 880篇 |
2005年 | 706篇 |
2004年 | 527篇 |
2003年 | 494篇 |
2002年 | 473篇 |
2001年 | 375篇 |
2000年 | 341篇 |
1999年 | 486篇 |
1998年 | 2502篇 |
1997年 | 1502篇 |
1996年 | 1055篇 |
1995年 | 638篇 |
1994年 | 531篇 |
1993年 | 478篇 |
1992年 | 189篇 |
1991年 | 210篇 |
1990年 | 171篇 |
1989年 | 186篇 |
1988年 | 154篇 |
1987年 | 185篇 |
1986年 | 150篇 |
1985年 | 245篇 |
1984年 | 204篇 |
1983年 | 183篇 |
1982年 | 152篇 |
1981年 | 187篇 |
1980年 | 191篇 |
1979年 | 134篇 |
1978年 | 123篇 |
1977年 | 239篇 |
1976年 | 518篇 |
1975年 | 102篇 |
1973年 | 116篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
91.
Jürgen Wallner 《Ethik in der Medizin》2010,22(2):117-130
Background In recent years, it has been intensively debated whether and how the conscience must be protected in the context of pharmacies. Currently, Germany and Austria have no legal regulation regarding this problem. Objective The ethical framework for a coping strategy dealing with the problem of freedom of conscience in the pharmacy will be outlined. Method By applying legal ethics' principle of proportionality within German and Austrian constitutional law as well as the European Convention on Human Rights, the problem is analyzed on its individual, corporative, and societal level. Results On the individual level, the pharmacist's and the patient's stakes and rights (e.g., the freedom of conscience) are carefully balanced by using the principle of proportionality. On the corporative level, the autonomy granted by the fundamental right of freedom of religion and belief legitimatizes a pharmacy's ideological profile as an organization and may cause conflicts of loyalty within the pharmacy. On the societal level, four pro-active options of shaping the legal framework are available: a social-welfare, a libertarian, a professional, and a communitarian. How conflicts on the individual or the corporative level can be solved depends on the option(s) that are chosen on the societal level. Conclusion If the status quo is to be changed, this article argues for two approaches: a) the introduction of a qualified conscience clause for pharmacists (including duties to consult, refer, treat in emergencies, and inform); b) a ‘weak’ communitarian option, striving for a compromise between a pharmaceutical corporation (i.e., pharmacy or pharmaceutical professional association) with an ideological profile and the public healthcare system. Both approaches satisfy a careful balancing of legitimate goods. 相似文献
92.
The transverse mixing of quartz sand (mean particle sizes 157, 323, 794 and 1038 μm) and sodium carbonate (soda) (mean particle size 137 μm) has been investigated in a laboratory rotary drum reactor of 300 mm length and 310 mm diam. Solid movement in the drum was observed by means of colored tracers and successive exposures as well as by means of hot tracers and recording the local temperature in the bulk of particles. Three different types of the particles and bulk behaviour could be observed for stickly particles. The time constant of the mixing was estimated as a function of the rotational speed of the drum. The “cooling-down” curves of the bulk of particles were measured in a laboratory oven of 250 mm diam. and 600 mm length. The temperature variation as a function of the time can be described by the Newtonian cooling law, from which the heat transfer coefficient at the wall αw was estimated.The absolute value of αw's and their dependence on the contact time and particle diameter cannot be calculated by the heat penetration model, which disregards the film resistance at the bulk/wall contact. By taking into account this resistance a good quality of fitting can be achieved. 相似文献
93.
We propose a new approach that improves perceptual quality of the separated sources in blind single-channel musical source separation. It uses the advantages of subspace learning based on Non-negative Matrix Factorization (NMF) in which the bases represent the notes. The cost function is formulated in the form of weighted β-divergence by adopting the PEAQ auditory model defined in ITU-R BS.1387 into the source separation. The proposed perceptually weighted factorization scheme is integrated into the Non-negative Matrix Factor 2-D Deconvolution (NMF2D) and Clustered Non-negative Matrix Factorization (CNMF) to overcome the source clustering problem encountered in under-determined source separation. It is shown that the introduced perceptually weighted NMF schemes, named as PW-NMF2D and PW-CNMF, efficiently learn the bases that enable us to apply a simple resynthesis of the musical sources based on the temporal model stored in the encoding matrix. Source separation performance has been reported on musical mixtures where 1–2 dB improvement is achieved in terms of SDR, SIR and SAR compared to the state-of-the-art methods. Performance has also been evaluated by perceptual measures resulting an improvement of 2–5 in OPS, TPS, IPS and APS values. 相似文献
94.
At the ISF (Joining and Welding Institute, RWTH Aachen University) the long-established electron beam (EB) welding process
is investigated to meet the requirements of the field of micro-applications. A modified LEO ZEISS DSM 962 scanning electron
microscope (SEM) is being used as a Micro-EB welding machine. The diameter of the beam in welding mode is about 20 μm, with
a maximum beam power of 6 Watt at 30 kV acceleration voltage. The process-specific advantages, such as the inertia-free movement
of the tool electron beam, the very small beam diameter, the clean room environment which is due to processing in a vacuum
(no shielding gas needed) and the excellent applicability for visual quality control offer the best preconditions for hybrid
micro-assembly purposes. If the technology is down-scaled to a micro-level, physical effects occur whose consequences must
be met with new approaches of solution. Joining of micro-components presupposes optimal contact conditions. If the micro-components
are of a flexible type, those optimal conditions are difficult to implement. The ratio of forces during the joining process
and also the low stiffness of the components which is due to the small dimensions require, on the one hand, the application
of a suitable handling technique or, on the other hand, a specific beam manipulation strategy. Especially in the field of
micro-applications, the possibility to exert influence on the thermal distortion by symmetrical heating and solidification
processes is of particular importance. Therefore, the reproducibility of the welded joints is one of the great challenges
in the field of microwelding. The investigations and developments done at the ISF show successful results in joining stainless
steel sheet materials down to 30 μm thickness and steel wire down to 50 μm in diameter, whereas other materials (Tungsten,
Aluminum, Titanium, Nickel) are under investigation. 相似文献
95.
After a period of general nonspecific symptoms (weakness; nocturnal sweating) for a few days a 29-year-old man suddenly developed a purpura-like rash on both hands and feet ("glove and sock") with mild itching and oedema. A blood count demonstrated leukopenia (2100/microliters) with neutropenia (1100/microliters), thrombocytopenia (81,000/microliters) and reticulocytopenia (1/1000), while haemoglobin content was normal. The bone-marrow showed almost complete reduction of erythropoiesis with the presence of giant proerythroblasts. Granulopoiesis and megakaryopoiesis were unremarkable. Positive tests for IgM and IgG antibodies against parvovirus B19 established the diagnosis of infection with this organism. The rash, blood picture and bone-marrow changes all regressed spontaneously, without any treatment, within a week. The petechial or purpuric "glove and sock" syndrome may be a special form of parvovirus B19 infection. 相似文献
96.
A method and an experimental setup have been developed for measuring absolute photoemission cross sections for electron-impact-induced line radiation in the vacuum ultraviolet (VUV). Unparalleled low uncertainties for the cross sections were achieved mainly from the use of the Berlin electron storage ring as a primary standard source in the VUV for the determination of the responsivity of the spectrometer-detector system used and from the use of a spinning rotor gauge as a secondary standard for the determination of the target gas density. As the first result we present a photoemission cross section for the Ar II 3s3p(6)(2)S(?)-3s(2)3p(5)(2)p?(3/2) transition at 91.98 nm for 2-keV electron-impact energy of 1.167 × 10(-18) cm(2) with a relative uncertainty of 4.4% (√3σ value). This low uncertainty demonstrates the suitability of the setup for further cross-section measurements. 相似文献
97.
Mechanical theorem proving in projective geometry 总被引:3,自引:0,他引:3
Jürgen Richter-Gebert 《Annals of Mathematics and Artificial Intelligence》1995,13(1-2):139-172
We present an algorithm that is able to confirm projective incidence statements by carrying out calculations in the ring of all formal determinants (brackets) of a configuration. We will describe an implementation of this prover and present a series of examples treated by the prover, includingPappus' andDesargues' theorems, thesixteen point theorem, Saam's theorem, thebundle condition, theuniqueness of a harmonic point andPascal's theorem. 相似文献
98.
K Oette G Kühn A R?mer R Niemann KJ Gundermann R Schumacher 《Canadian Metallurgical Quarterly》1995,45(8):875-879
Essentiale and Lipostabil contain "essential" phospholipids from the soybean, mainly 1,2-dilinoleoyl-phosphatidylcholine (CAS 998-06-1, DLPC) which is considered as the main active ingredient. A single oral dose of d15-DLPC loaded with deuterium 9 times in the choline and 6 times in the linoleic acid of the 1-position was given to volunteers. Sera from 11 blood samples taken within 48 h after application were examined by means of mass spectrometry with regard to d9-choline and d6-linoleic acid in the 1- and 2-position of serum phosphatidylcholines (PC) as well as in the serum triglycerides. d9-choline, i.e. the total of d15-PC and d9-PC, showed maximum values of 5.6% of the total serum PC concentration. Normally, about 1.3% of PC in the human serum is DLPC. Serum 1-linoleoyl-PC was increased by 32-40% after oral application of d15-DLPC. A minor uptake of d6-linoleic acid into the 2-position of serum PC, which is rich in linoleic acid, and into the serum triglycerides was observed with peak values of 2.3% and 6.1%, resp. The uptake of polyunsaturated PC species like DLPC and 1-linoleoyl-PC into the liver after oral application of drugs containing such species in high amounts like "essential" phospholipids with about 50% of DLPC let expect therapeutic effects on membranes into which this special species is incorporated. 相似文献
99.
K. A. Müller 《Journal of Superconductivity and Novel Magnetism》2017,30(10):2707-2709
Doped tungstates exhibit superconductivity as indicated to occur mainly at the surface of the WO3 grains present. To generate bulk 3D superconducting material of doped tungstates, it is proposed to employ the recently discovered UV-generated synthesis of complex oxides from mixed simple oxides by illuminating the mixture with ultraviolet light at modest temperatures, as found in Shengelaya’s group in Tbilisi, and to generate a percolating 3D network of 2D superconducting sheets using the smallest basis oxides as the starting material. The latter procedure was demonstrated recently to be very effective in a collaboration with the present author (Daraselia et al., J. Appl. Phys. 121, 145104, 2017). If this proposition is successful, it would establish the doped tungstates as a second group of HTS besides the copper oxides that could be chosen for certain applications. 相似文献
100.