全文获取类型
收费全文 | 241246篇 |
免费 | 2626篇 |
国内免费 | 427篇 |
专业分类
电工技术 | 4292篇 |
综合类 | 257篇 |
化学工业 | 39369篇 |
金属工艺 | 9379篇 |
机械仪表 | 7394篇 |
建筑科学 | 5448篇 |
矿业工程 | 1391篇 |
能源动力 | 5152篇 |
轻工业 | 24808篇 |
水利工程 | 2477篇 |
石油天然气 | 5092篇 |
武器工业 | 32篇 |
无线电 | 25044篇 |
一般工业技术 | 44770篇 |
冶金工业 | 45343篇 |
原子能技术 | 5950篇 |
自动化技术 | 18101篇 |
出版年
2021年 | 2107篇 |
2019年 | 2017篇 |
2018年 | 3488篇 |
2017年 | 3424篇 |
2016年 | 3687篇 |
2015年 | 2235篇 |
2014年 | 3898篇 |
2013年 | 10184篇 |
2012年 | 6146篇 |
2011年 | 8297篇 |
2010年 | 6546篇 |
2009年 | 7232篇 |
2008年 | 7585篇 |
2007年 | 7712篇 |
2006年 | 6888篇 |
2005年 | 6045篇 |
2004年 | 5815篇 |
2003年 | 5598篇 |
2002年 | 5673篇 |
2001年 | 5560篇 |
2000年 | 5383篇 |
1999年 | 5302篇 |
1998年 | 12570篇 |
1997年 | 8895篇 |
1996年 | 6857篇 |
1995年 | 5329篇 |
1994年 | 4735篇 |
1993年 | 4625篇 |
1992年 | 3667篇 |
1991年 | 3387篇 |
1990年 | 3593篇 |
1989年 | 3472篇 |
1988年 | 3303篇 |
1987年 | 2895篇 |
1986年 | 2932篇 |
1985年 | 3373篇 |
1984年 | 3219篇 |
1983年 | 2892篇 |
1982年 | 2738篇 |
1981年 | 2821篇 |
1980年 | 2719篇 |
1979年 | 2624篇 |
1978年 | 2684篇 |
1977年 | 2948篇 |
1976年 | 3805篇 |
1975年 | 2368篇 |
1974年 | 2242篇 |
1973年 | 2376篇 |
1972年 | 1970篇 |
1971年 | 1858篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
141.
G. A. Zeinalova A. E. Mushailov A. Kh. Mamedova É. A. Nagieva 《Chemistry and Technology of Fuels and Oils》1989,25(2):78-80
Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 2, pp. 14–15, February, 1989. 相似文献
142.
E M Chernovskaia 《Eksperimental?nai?a onkologii?a》1987,9(4):18-21, 78
The data of literature about the structure of cytoskeleton proteins in the normal and malignant cells are analyzed. The possibilities of using a specific polyclonal serum and a monoclonal antibody for a more precise ascertainment of the origin and diagnostic of tumours are discussed. The intermediate and active filaments may be used as a new class of histochemical markers. Laminin, the protein of basement membranes, probably, plays an important role in metastatic spreading. 相似文献
143.
J.E. Richards † 《Computer Graphics Forum》1987,6(3):211-218
Aspects of a prototype binding of GKS to the C++ programming language are presented. The binding makes use of classes and derived classes to define GKS concepts such as segments and workstations. Operator overloading is used for some GKS Functions. 相似文献
144.
PCR-based procedures in detection and DNA-fingerprinting of Salmonella from samples of animal origin
A. del Cerro S. M. Soto E. Landeras M. A. Gonzlez-Hevia J. A. Guijarro M. C. Mendoza 《Food microbiology》2002,19(6):567
The usefulness of selected PCR-protocols for the detection of Salmonella in 117 samples of animal origin (17 raw minced meat, 27 raw chicken meat, 8 raw sausages, and 25 egg samples, as well as 18 poultry faecal, and caecal swabs samples) and DNA-fingerprinting typing is shown. To establish an accurate PCR-procedure for Salmonella detection the following parameters were evaluated: two pre-PCR concentration procedures, centrifugation and immunomagnetic separation (IMS) using Dynabeads anti- Salmonella; the specificity and sensitivity of 10 sets of primers; and different conditions of the amplification reaction. In light of the results obtained from the use of PCR-based procedures alone or in combination with conventional methods, the following findings can be underlined: First, IMS is more efficient than centrifugation in the recovery of Salmonella. Second, the selected IMS/PCR-detection protocol is less time-consuming (45 h) than the IMS/culture procedure (90 h), and a good concordance between them was found when the Kappa coefficient was calculated (0·87). Third, PCR-ribotyping technique showed a very low discrimination power, being able to differentiate only three profiles. Fourth, RAPD technique using specific primers supports previous works in which it was proposed as a simple and useful tool for discriminating isolates between and within serotypes. Fifth, The efficiency, rapidity, and flexibility of the PCR-protocols applied were high, and they can be performed using two PCR-programs and the same basic equipment. 相似文献
145.
O. P. Mikheeva A. I. Sidorov A. S. Khaiikina E. V. Chuguevets 《Technical Physics Letters》2002,28(1):48-49
Experimental data on the pulsed laser radiation confinement in compensated GaAs and ZnSe with deep impurity levels are reported for the laser wavelength λ=1.55 μm and a pulse repetition frequency of up to 100 kHz. It is demonstrated that an increase in the pulse repetition rate is accompanied by a decrease in the energy confinement threshold and by an increase in the radiation attenuation coefficient. These effects are explained by the accumulation of nonequilibrium charge carriers related to a dependence of the recombination time constant on the concentration of free impurity centers. 相似文献
146.
M.E. Enyiegbulam 《International Journal of Adhesion and Adhesives》1985,5(4):207-210
Increased wetting of the coupling agent/epoxy resin interface was observed when γ-glycidoxypropyltrimethoxysilane, polyfunctional aminosilane and γ-aminopropyltriethoxysilane were applied respectively from methyllethylketone, dimethylformamide and water on woven glass cloths which had been cleaned at 300°C. However, when factory-applied coupling agents were burnt off the woven cloths and fresh coupling agents re-applied, it was found that the nature of the factory-applied coupling agent influenced subsequent wetting. Thinner glass fibres showed a greater improvement in wetting rate than thicker fibres in those solvents identified to be good for improved wettability, irrespective of the heat-cleaning temperature. 相似文献
147.
148.
149.
V. L. Ozol' L. F. Kandyba N. T. Bychenkov L. A. Zbarskii B. E. Koropov 《Metallurgist》1989,33(8):156-156
Lenin Dnepropetrovsk Pipe Plant. Translated from Metallurg, No. 8, p. 39, August, 1989. 相似文献
150.