全文获取类型
收费全文 | 167898篇 |
免费 | 11897篇 |
国内免费 | 6094篇 |
专业分类
电工技术 | 8705篇 |
技术理论 | 9篇 |
综合类 | 8717篇 |
化学工业 | 27883篇 |
金属工艺 | 10007篇 |
机械仪表 | 10070篇 |
建筑科学 | 9797篇 |
矿业工程 | 3934篇 |
能源动力 | 3664篇 |
轻工业 | 9472篇 |
水利工程 | 3137篇 |
石油天然气 | 9548篇 |
武器工业 | 1051篇 |
无线电 | 17534篇 |
一般工业技术 | 26974篇 |
冶金工业 | 11116篇 |
原子能技术 | 4829篇 |
自动化技术 | 19442篇 |
出版年
2024年 | 719篇 |
2023年 | 2353篇 |
2022年 | 4795篇 |
2021年 | 6383篇 |
2020年 | 4716篇 |
2019年 | 4051篇 |
2018年 | 5167篇 |
2017年 | 5630篇 |
2016年 | 5192篇 |
2015年 | 5683篇 |
2014年 | 7369篇 |
2013年 | 8943篇 |
2012年 | 9599篇 |
2011年 | 10299篇 |
2010年 | 8726篇 |
2009年 | 8568篇 |
2008年 | 8456篇 |
2007年 | 7926篇 |
2006年 | 7340篇 |
2005年 | 6269篇 |
2004年 | 4796篇 |
2003年 | 4710篇 |
2002年 | 4755篇 |
2001年 | 4330篇 |
2000年 | 3750篇 |
1999年 | 3314篇 |
1998年 | 2635篇 |
1997年 | 2217篇 |
1996年 | 1975篇 |
1995年 | 1737篇 |
1994年 | 1463篇 |
1993年 | 1244篇 |
1992年 | 1217篇 |
1991年 | 1074篇 |
1990年 | 1091篇 |
1989年 | 1011篇 |
1988年 | 899篇 |
1987年 | 843篇 |
1986年 | 764篇 |
1985年 | 717篇 |
1984年 | 704篇 |
1981年 | 669篇 |
1979年 | 738篇 |
1978年 | 779篇 |
1977年 | 742篇 |
1976年 | 760篇 |
1975年 | 713篇 |
1974年 | 721篇 |
1973年 | 723篇 |
1972年 | 706篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
122.
123.
Analytical solution of a system of nonlinear measuring equations of a 12-pole microwave reflectometer was obtained. Criteria for selecting a true solution in the general case were developed and the analysis was conducted for a number of particular cases that may generate practical interest. 相似文献
124.
The safe operation of VVéR reactors has been discussed throughout the entire design process, taking account of the normative
documentation, including the international requirements (IAEA, EUR). After the first domestic normative document “Basic principles
for securing the safety of nuclear power plants” was approved in 1973, work began on the reconstruction of the first-generation
VVéR-440 power-generating units. The measures taken to increase safety concerned all types of reactors VVéR-440 and-1000.
Information on implementing these measures is presented.
__________
Translated from Atomnaya énergiya, Vol. 101, No. 2, pp. 87–93, August, 2006. 相似文献
125.
V. P. Vasilevskii M. N. Mikhailov A. A. Petrov M. I. Rozhdestvenskii Yu. M. Cherkashov 《Atomic Energy》2006,100(4):295-301
The basic stages and directions of upgrading and reconstruction of the power-generating units of nuclear power plants with
RBMK reactors over a period of 20 yr since the Chernobyl accident are reflected in this paper. The greatest amount of work
was done in 1986–1990 on all units with RBMK-1000 and-1500 reactors which were operating at that time in the USSR. The purpose
of the upgrade was to improve the neutron-physical characteristics of the reactor cores, increase the response speed of the
safety and control system and decrease the positive effect of water outflow from the cooling loop of this system, increase
the flow capacity of the systems performing emergency discharge of the steam-gas mixture from the reactor, and improve the
basic operating documentation.
The subsequent stages of the upgrading and reconstruction concerned mainly the first-generation power-generating units (Nos.
1 and 2 units of the Leningrad and Kursk nuclear power plants). These works were performed to make the power-generating units
conform to the requirements of the modern normative documents on safety and allow for the possibility of these units to remain
in operation after the nominal 30-yr service life has been exhausted.
__________
Translated from Atomnaya énergiya, Vol. 100, No. 4, pp. 312–320, April, 2006. 相似文献
126.
The formation specifics of the structure and phase composition of densely sintered ceramics based on a low-melting argillaceous
material from Belarus together with a combined flux and a grog additive are investigated. The correlation between the physicochemical
properties, structure, phase composition, and the time-temperature firing schedules of the developed materials are investigated.
Electron probe microanalysis makes it possible to monitor variations in the chemical composition at various local sites and
compare it with the estimated composition of the mixture. The optimum regimes for the heat treatment of articles are determined.
__________
Translated from Steklo i Keramika, No. 6, pp. 32 – 36, June, 2005. 相似文献
127.
We present an automatic algorithm to segment all the local and global asymmetric units of a three-dimensional density map of icosahedral viruses. This approach is readily applicable to the structural analysis of a broad range of virus structures that are reconstructed using cryo-electron microscopy (cryo-EM) technique. Our algorithm includes three major steps operating on the three dimensional density map: the detection of critical points of the volumetric density function, the detection of global and local symmetry axes, and, finally, the boundary segmentation of all the asymmetric units. We demonstrate the efficacy of our algorithm and report our results on several experimental volumetric datasets, consisting of both reconstructed cryo-EM molecular density maps taken from the European Bioinformatics Institute archive, as well our own synthetically generated (blurred) maps calculated from X-ray resolution molecular structural data taken from the Protein Data Bank. 相似文献
128.
K.F. Chan C.K. Wan K.N. Yu 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2007,262(1):128-134
In the present work, we have studied the feasibility of a method based on polyallyldiglycol-carbonate (PADC) films to investigate the effects of alpha particles on HeLa cervix cancer cells. Thin PADC films with thickness of about 20 μm were prepared from commercially available CR-39 films by chemical etching to fabricate custom-made petri dishes for cell culture, which could accurately record alpha particle hit positions. A special method involving “base tracks” for aligning the images of cell nuclei and alpha particle hits has been proposed, so that alpha particle transversals of cell nuclei can be visually counted. Radiobiological experiments were carried out to induce DNA damages, with the TdT-mediated dUTP Nick-End Labeling (TUNEL) fluorescence method employed to detect DNA strand breaks. The staining results were investigated by flow cytometer. The preliminary results showed that more strand breaks occurred in cells hit by alpha particles with lower energies. Moreover, large TUNEL positive signals were obtained even with small percentages of cells irradiated and TUNEL signals were also obtained from non-targeted cells. These provided evidence for the bystander effect. 相似文献
129.
Yu. P. Pyt’ev 《Pattern Recognition and Image Analysis》2006,16(3):460-477
The quality-estimation and decision-making criteria based on the values of error possibility likelihood measures, error necessity
likelihood, error possibility confidence, and error necessity confidence are considered. The criteria are formulated for the
adequacy of an uncertain fuzzy (UF) model and conclusions based on the UF model for the object under investigation and the
UF observation model. 相似文献
130.