全文获取类型
收费全文 | 9668篇 |
免费 | 764篇 |
国内免费 | 22篇 |
专业分类
电工技术 | 87篇 |
综合类 | 15篇 |
化学工业 | 2473篇 |
金属工艺 | 289篇 |
机械仪表 | 315篇 |
建筑科学 | 390篇 |
矿业工程 | 19篇 |
能源动力 | 318篇 |
轻工业 | 1365篇 |
水利工程 | 72篇 |
石油天然气 | 46篇 |
武器工业 | 2篇 |
无线电 | 719篇 |
一般工业技术 | 1769篇 |
冶金工业 | 880篇 |
原子能技术 | 95篇 |
自动化技术 | 1600篇 |
出版年
2024年 | 19篇 |
2023年 | 106篇 |
2022年 | 206篇 |
2021年 | 389篇 |
2020年 | 277篇 |
2019年 | 287篇 |
2018年 | 429篇 |
2017年 | 425篇 |
2016年 | 467篇 |
2015年 | 341篇 |
2014年 | 453篇 |
2013年 | 720篇 |
2012年 | 656篇 |
2011年 | 765篇 |
2010年 | 558篇 |
2009年 | 527篇 |
2008年 | 498篇 |
2007年 | 371篇 |
2006年 | 324篇 |
2005年 | 292篇 |
2004年 | 211篇 |
2003年 | 219篇 |
2002年 | 202篇 |
2001年 | 135篇 |
2000年 | 116篇 |
1999年 | 94篇 |
1998年 | 233篇 |
1997年 | 188篇 |
1996年 | 122篇 |
1995年 | 88篇 |
1994年 | 85篇 |
1993年 | 74篇 |
1992年 | 41篇 |
1991年 | 41篇 |
1990年 | 33篇 |
1989年 | 34篇 |
1988年 | 30篇 |
1987年 | 32篇 |
1986年 | 22篇 |
1985年 | 37篇 |
1984年 | 25篇 |
1983年 | 24篇 |
1982年 | 16篇 |
1981年 | 26篇 |
1980年 | 20篇 |
1979年 | 25篇 |
1978年 | 14篇 |
1977年 | 20篇 |
1976年 | 37篇 |
1971年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 750 毫秒
41.
42.
JY Cesbron H Agut B Gosselin D Candotti M Rapha?l F Puech M Grandadam P Debré A Capron B Autran 《Canadian Metallurgical Quarterly》1994,317(7):669-674
HIV induces a multi-organ infection with a dual tropism for both lymphocytes and monocytes/macrophages. The lung is a target both for HIV infection and HIV-related opportunistic infections. The SCID mouse has provided the opportunity to develop a small animal model for HIV infection. However, HIV-1 infection of the human fetal thymus and liver (SCID Liv/Thy) implanted in these mice occurred only after direct intraimplant injection of HIV-1 and the resultant HIV-1 infection was restricted to the human thymus. Here we report that human foetal lung can develop in SCID Liv/Thy mice resulting in the development of normal human alveolar and bronchiolar lung compartments which can be productively infected with cell-free HIV-1 virus, leading to a systemic and bifocal infection. This SCID-Hu model should be useful for studying AIDS physiopathology, human viruses with lung tropism and for helping to define gene therapy protocols in lung human cells in vivo. 相似文献
43.
The relationship between endometriosis and infertility is observed frequently. Patients with both conditions require a conservative approach to their management. Since hormonal therapy is one of those approaches, we sought to compare the efficacy of Danazol and Gestrinone in 80 infertile patients (48 and 32, respectively). Therapy lasted 6 months in both treatment groups, and all patients studied had laboratory tests performed and were clinically evaluated and classified through laparoscopy before and after therapy. The improvement of symptoms and favorable follow-up were similar with both treatments. The reestablishment of menstrual patterns and fertility were also nearly alike in both groups. However, Gestrinone was associated with fewer secondary effects and is easier to administer than Danazol. We conclude that Gestrinone is a useful medication in the management of the infertile patient with endometriosis. 相似文献
44.
45.
Paulo S. André António L. Teixeira Armando N. Pinto Lara P. Pellegrino Berta B. Neto José F. Rocha Joäo L. Pinto Paulo N. Monteiro 《ETRI Journal》2006,28(2):257-259
In this letter, we will evaluate the performance degradation of a 40 km high‐speed (40 Gb/s) optical system, induced by optical fiber variations of the chromatic dispersion induced by temperature changes. The chromatic dispersion temperature sensitivity will be estimated based on the signal quality parameters. 相似文献
46.
In-Situ and Real-Time Investigation of Columnar-to-Equiaxed Transition in Metallic Alloy 总被引:1,自引:0,他引:1
H. Nguyen-Thi G. Reinhart N. Mangelinck-Noël H. Jung B. Billia T. Schenk J. Gastaldi J. Härtwig J. Baruchel 《Metallurgical and Materials Transactions A》2007,38(7):1458-1464
In this article, we present a review of observations during Al-3.5 wt pct Ni alloy solidi.cation experiments performed at
the European Synchrotron Radiation Facility (ESRF) in Grenoble. These experiments provide direct access to dynamical phenomena
during columnar growth (initial transient and breakdown of a planar solid-liquid interface), and for the first time to the
transition from columnar-to-equiaxed microstructure (nucleation ahead of a columnar front and blocking of a columnar front
by an equiaxed microstructure) and fully equiaxed growth (propagation of an effective front). Based on these experimental
observations, critical parameters such as columnar growth velocity variation during the transition or equiaxed-grain diameter
are measured and discussed.
This article is based on a presentation made in the symposium entitled “Solidi.cation Modeling and Microstructure Formation:
In Honor of Prof. John Hunt,” which occurred March 13–15, 2006, during the TMS Spring Meeting in San Antonio, Texas, under
the auspices of the TMS Materials Processing and Manufacturing Division, Solidification Committee. 相似文献
47.
Peter Eaton Andrea Ragusa Caroline Clavel Cristina T Rojas Paul Graham Raúl V Durán Soledad Penadés 《IEEE transactions on nanobioscience》2007,6(4):309-318
Glyconanoparticles which present carbohydrate and amino groups motifs at their surface were produced. These particles were highly stable and soluble in aqueous solutions. The presence of the carbohydrate groups also allowed the inclusion of more strongly binding groups, without affecting solubility. The binding of a model DNA, plasmid by these nanoparticles was studied by atomic force microscopy, transmission electron microscopy, and gel electrophoresis. Significant differences between the nanoparticles based on their affinities for the DNA were found, with implications for their potential use as nonviral gene delivery agents. 相似文献
48.
Hybrid Approach for Addressing Uncertainty in Risk Assessments 总被引:3,自引:0,他引:3
Dominique Guyonnet Bernard Bourgine Didier Dubois Hélène Fargier Bernard C?me Jean-Paul Chilès 《Canadian Metallurgical Quarterly》2003,129(1):68-78
Parameter uncertainty is a major aspect of the model-based estimation of the risk of human exposure to pollutants. The Monte Carlo method, which applies probability theory to address model parameter uncertainty, relies on a statistical representation of available information. In recent years, other uncertainty theories have been proposed as alternative approaches to address model parameter uncertainty in situations where available information is insufficient to identify statistically representative probability distributions, due in particular to data scarcity. The simplest such theory is possibility theory, which uses so-called fuzzy numbers to represent model parameter uncertainty. In practice, it may occur that certain model parameters can be reasonably represented by probability distributions, because there are sufficient data available to substantiate such distributions by statistical analysis, while others are better represented by fuzzy numbers (due to data scarcity). The question then arises as to how these two modes of representation of model parameter uncertainty can be combined for the purpose of estimating the risk of exposure. This paper proposes an approach (termed a hybrid approach) which combines Monte Carlo random sampling of probability distribution functions with fuzzy calculus. The approach is applied to a real case of estimation of human exposure, via vegetable consumption, to cadmium present in the surficial soils of an industrial site located in the north of France. The application illustrates the potential of the proposed approach, which allows the uncertainty affecting model parameters to be represented in a way that is consistent with the information at hand. Also, because the hybrid approach takes advantage of the “rich” information provided by probability distributions, while retaining the conservative character of fuzzy calculus, it is believed to hold value in terms of a “reasonable” application of the precautionary principle. 相似文献
49.
50.