全文获取类型
收费全文 | 168246篇 |
免费 | 11846篇 |
国内免费 | 6100篇 |
专业分类
电工技术 | 8803篇 |
技术理论 | 9篇 |
综合类 | 8716篇 |
化学工业 | 27495篇 |
金属工艺 | 10001篇 |
机械仪表 | 10075篇 |
建筑科学 | 9806篇 |
矿业工程 | 3929篇 |
能源动力 | 3690篇 |
轻工业 | 9380篇 |
水利工程 | 3137篇 |
石油天然气 | 9524篇 |
武器工业 | 1051篇 |
无线电 | 17705篇 |
一般工业技术 | 27027篇 |
冶金工业 | 11546篇 |
原子能技术 | 4870篇 |
自动化技术 | 19428篇 |
出版年
2024年 | 715篇 |
2023年 | 2318篇 |
2022年 | 4603篇 |
2021年 | 6216篇 |
2020年 | 4677篇 |
2019年 | 4026篇 |
2018年 | 5137篇 |
2017年 | 5587篇 |
2016年 | 5152篇 |
2015年 | 5647篇 |
2014年 | 7313篇 |
2013年 | 8934篇 |
2012年 | 9574篇 |
2011年 | 10307篇 |
2010年 | 8741篇 |
2009年 | 8571篇 |
2008年 | 8470篇 |
2007年 | 7940篇 |
2006年 | 7356篇 |
2005年 | 6277篇 |
2004年 | 4819篇 |
2003年 | 4737篇 |
2002年 | 4781篇 |
2001年 | 4349篇 |
2000年 | 3777篇 |
1999年 | 3361篇 |
1998年 | 2788篇 |
1997年 | 2321篇 |
1996年 | 2045篇 |
1995年 | 1795篇 |
1994年 | 1509篇 |
1993年 | 1295篇 |
1992年 | 1243篇 |
1991年 | 1093篇 |
1990年 | 1112篇 |
1989年 | 1027篇 |
1988年 | 915篇 |
1987年 | 855篇 |
1986年 | 783篇 |
1985年 | 749篇 |
1984年 | 716篇 |
1981年 | 676篇 |
1979年 | 741篇 |
1978年 | 791篇 |
1977年 | 747篇 |
1976年 | 776篇 |
1975年 | 722篇 |
1974年 | 727篇 |
1973年 | 730篇 |
1972年 | 710篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
从稳态到动态的空气调节 总被引:1,自引:0,他引:1
分析传统空调所提供的稳态参数微气候环境不一定能达到人的舒适和健康的要求,提出符合人本身生理习惯的空调送风方式应该是动态空气调节.认为个人可调节和适宜的环境渐变能同时保证舒适和健康两方面需要. 相似文献
22.
低温脂肪酶产生菌的筛选、鉴定及其部分酶学性质 总被引:15,自引:1,他引:14
从南极乔治王岛冻土来源的76株低温细菌中筛选到13株低温脂肪酶产生菌,对其中的BTsl0022菌株进行鉴定。通过生理生化特征、16s rDNA基因序列的同源性和系统发育分析发现,菌株RTsl0022属于假单胞菌属(Pseudomonas),但与已定名的假单胞菌有一定的差异,与未定名的Pseudomonas sp.PsB的亲缘关系最接近,故将其暂定名为Pseudomonas sp.BTsl0022。对该菌脂肪酶的酶学性质初步研究表明,酶的最适作用温度为24℃,对热敏感,60℃处理30min仅残留25%酶活性,酶的适宜作用pH范围在7.0~9.0,最适pH为8.0。 相似文献
23.
The hydrocarbon-group composition and distribution of naphthenoaromatic hydrocarbons of West Siberian oils were studied by the technique of mass spectrometry. Naphthenoaromatic hydrocarbons of the general formula CnH2n?z , where z is 8, 10, 12, 14, 16, or 18, containing from one to six saturated cycles are present in oils in significant concentrations. Naphthenomonoarenes with one saturated cycle dominate in all oils. An increase in the amount of compounds containing 3–6 saturated cycles in their molecule with the occurrence depth was noted. Naphthenobiarenes of the general formula CnH2n?z , where z is 14, 16, 18, 20, 22, or 24 containing from one to six saturated cycles are present in oils in concentrations from 20.0 to 54.0 wt % of the biaromatic fraction. Most oils are characterized by the prevalence of structures with one and two saturated cycles in their molecule. The dependence of the number of cycles in naphthenobiarenes on the nature of original organic matter (OM) was not traced. The lack of correlation between the number of cycles and the OM type is presumably due to the fact that, for the most part, fused polycyclic naphthenobiarenes reflect the degree of catagenetic alteration of organic matter. 相似文献
24.
Extraction of Cs, Sr, Eu, U, Np, and Am with mixtures of dipicolinic acid diamides with chlorinated cobalt dicarbollide was studied. A synergistic effect was revealed. 相似文献
25.
Albul V. I. Bychkov V. B. Gusev K. E. Demidov V. S. Demidova E. V. Kurchanov A. F. Luk'yashin V. E. Sokolov A. Yu. 《Measurement Techniques》2003,46(8):810-814
A monitor is proposed based on ultrasonic production when ionizing radiation passes through a medium. The recording element is a 0.2 mm aluminum plate mounted in a ceramic acoustic converter AC in the form of a wedge of thickness 2 mm. The low plate thickness minimizes the beam parameter distortion, while special technology used in the AC provides high sensitivity. The device has been calibrated in the proton beam from the ITEP accelerator at 200 MeV with 2·109–6·1010 particles in a pulse and a pulse length of 70 nsec. 相似文献
26.
Polyaryloxydiphenylsilanes were prepared from phosphorus‐containing diols and diphenydichlorolsilane through solution polymerization. With a stoichiometric imbalance in feed monomers, the resulting polymers exhibited moderate melting points and good processing properties. The polymers prepared showed initial decomposition temperatures above 340 °C, excellent thermal stability, high char yields at 850 °C and very high limited oxygen index values of 56–59. The polymers' char yields and their (P + Si) contents showed linear relationships. © 2003 Society of Chemical Industry 相似文献
27.
28.
N.S. Chen S.F. Yu 《Photonics Technology Letters, IEEE》2004,16(7):1610-1612
The effect of external optical feedback on the transient response of antiresonant reflecting optical waveguide (ARROW) vertical-cavity surface-emitting lasers (VCSELs) is studied. It can be shown that the proper design of ARROW can suppress the excitation of high-order transverse leaky mode as well as increase the critical feedback strength so that stable high-power single-mode operation of VCSELs can be obtained even under the influence of strong external optical feedback. 相似文献
29.
A.S. Fomichev I. David S.M. Lukyanov Yu.E. Penionzhkevich N.K. Skobelev O.B. Tarasov 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1994,350(3):605-607
The mass and charge identification of secondary particles with Z < 4 by a large CsI(T1) scintillation detector is performed using pulse shape analysis and time-of-flight methods. The dependence of the light output on E, A and Z is studied in the energy range of 1–20 MeV/A and special attention is paid to the integration time of the photomultiplier anode signal. It is found that the behaviour of the calibration curves strongly depends on the choice of the integration time interval. 相似文献
30.
Modeling ion implantation of HgCdTe 总被引:2,自引:0,他引:2
H. G. Robinson D. H. Mao B. L. Williams S. Holander-Gleixner J. E. Yu C. R. Helms 《Journal of Electronic Materials》1996,25(8):1336-1340
Ion implantation of boron is used to create n on p photodiodes in vacancy-doped mercury cadmium telluride (MC.T). The junction
is formed by Hg interstitials from the implant damage region diffusing into the MC.T and annihilating Hg vacancies. The resultant
doping profile is n+/n-/p, where the n+ region is near the surface and roughly coincides with the implant damage, the n- region is where Hg vacancies have been annihilated revealing a residual grown-in donor, and the p region remains doped by
Hg vacancy double acceptors. We have recently developed a new process modeling tool for simulating junction formation in MC.T
by ion implantation. The interstitial source in the damage region is represented by stored interstitials whose distribution
depends on the implant dose. These interstitials are released into the bulk at a constant, user defined rate. Once released,
they diffuse away from the damage region and annihilate any Hg vacancies they encounter. In this paper, we present results
of simulations using this tool and show how it can be used to quantitatively analyze the effects of variations in processing
conditions, including implant dose, annealing temperature, and doping background. 相似文献