全文获取类型
收费全文 | 260161篇 |
免费 | 3186篇 |
国内免费 | 823篇 |
专业分类
电工技术 | 5130篇 |
综合类 | 330篇 |
化学工业 | 37244篇 |
金属工艺 | 10253篇 |
机械仪表 | 8489篇 |
建筑科学 | 6102篇 |
矿业工程 | 1076篇 |
能源动力 | 6398篇 |
轻工业 | 22862篇 |
水利工程 | 2561篇 |
石油天然气 | 3910篇 |
武器工业 | 68篇 |
无线电 | 34735篇 |
一般工业技术 | 50078篇 |
冶金工业 | 46532篇 |
原子能技术 | 5419篇 |
自动化技术 | 22983篇 |
出版年
2021年 | 2041篇 |
2019年 | 2033篇 |
2018年 | 3481篇 |
2017年 | 3535篇 |
2016年 | 3737篇 |
2015年 | 2322篇 |
2014年 | 4053篇 |
2013年 | 11297篇 |
2012年 | 6568篇 |
2011年 | 8876篇 |
2010年 | 6987篇 |
2009年 | 7852篇 |
2008年 | 8679篇 |
2007年 | 8614篇 |
2006年 | 7803篇 |
2005年 | 7139篇 |
2004年 | 6885篇 |
2003年 | 6733篇 |
2002年 | 6372篇 |
2001年 | 6469篇 |
2000年 | 6169篇 |
1999年 | 6253篇 |
1998年 | 14240篇 |
1997年 | 10270篇 |
1996年 | 8112篇 |
1995年 | 6415篇 |
1994年 | 5711篇 |
1993年 | 5583篇 |
1992年 | 4552篇 |
1991年 | 4211篇 |
1990年 | 4049篇 |
1989年 | 3779篇 |
1988年 | 3625篇 |
1987年 | 3170篇 |
1986年 | 3065篇 |
1985年 | 3610篇 |
1984年 | 3382篇 |
1983年 | 3031篇 |
1982年 | 2850篇 |
1981年 | 2951篇 |
1980年 | 2760篇 |
1979年 | 2648篇 |
1978年 | 2499篇 |
1977年 | 2945篇 |
1976年 | 3554篇 |
1975年 | 2316篇 |
1974年 | 2312篇 |
1973年 | 2318篇 |
1972年 | 1849篇 |
1971年 | 1745篇 |
排序方式: 共有10000条查询结果,搜索用时 145 毫秒
981.
L. D. Panteleev L. N. Konovalov I. I. Konovalov S. A. Krylov V. B. Malygin K. I. Naboichenko 《Atomic Energy》1994,77(2):613-617
A. A. Bochvar All-Union Scientific-Research Institute of Standardization in Machine Engineering. Moscow Engineering Physics
Institute. Translated from Atomnaya énergiya, Vol. 77, No. 2, pp. 123–129, August, 1994. 相似文献
982.
This paper describes a verified compiler for PreScheme, the implementation language for thevlisp run-time system. The compiler and proof were divided into three parts: A transformational front end that translates source text into a core language, a syntax-directed compiler that translates the core language into a combinator-based tree-manipulation language, and a linearizer that translates combinator code into code for an abstract stored-program machine with linear memory for both data and code. This factorization enabled different proof techniques to be used for the different phases of the compiler, and also allowed the generation of good code. Finally, the whole process was made possible by carefully defining the semantics ofvlisp PreScheme rather than just adopting Scheme's. We believe that the architecture of the compiler and its correctness proof can easily be applied to compilers for languages other than PreScheme.This work was supported by Rome Laboratory of the United States Air Force, contract No. F19628-89-C-0001, through the MITRE Corporation, and by NSF and DARPA under NSF grants CCR-9002253 and CCR-9014603. Author's current address: Department of Computer Science and Engineering, Oregon Graduate Institute, P.O. Box 91000, Portland, OR 97291-1000.The work reported here was supported by Rome Laboratory of the United States Air Force, contract No. F19628-89-C-0001. Preparation of this paper was generously supported by The MITRE Corporation.This work was supported by Rome Laboratory of the United States Air Force, contract No. F19628-89-C-0001, through the MITRE Corporation, and by NSF and DARPA under NSF grants CCR-9002253 and CCR-9014603. 相似文献
983.
984.
An overview of MOSFET modeling for circuit simulation is presented. After discussing some of the implications of analog and low-power applications, the history of the MOS models commonly used in SPICE-like circuit simulators is presented, followed by a discussion of the evolution of strategies for modeling the geometry dependence of MOSFET characteristics. The growth of complexity and requirements for future MOS models are also considered 相似文献
985.
D Del Bufalo C Cucco C Leonetti G Citro I D'Agnano M Benassi T Geiser G Zon B Calabretta G Zupi 《Canadian Metallurgical Quarterly》1996,74(3):387-393
We investigated the effect of c-myb antisense phosphorothioate oligodeoxynucleotides [(S)ODNs] and cisplatin (CDDP) combination on the human colon carcinoma cell line LoVo Dx both in vitro and in nude mice bearing LoVo Dx solid tumour. We show that antisense (S)ODN treatment decreases c-myb mRNA and protein expression, induces growth arrest in the G1 phase of the cell cycle, and inhibits cell proliferation. In vivo treatment with c-myb antisense (S)ODNs results in a reduction in tumour growth. A greater inhibition of cell proliferation in vitro and a higher increase of tumour growth inhibition and growth delay in vivo were obtained with the combination of (S)ODNs and CDDP than when the two agents were administered separately. This comparative study, using the same tumour cell line in vitro and in vivo, suggests that c-myb antisense (S)ODNs might be useful in the therapy of colon cancer in combination with antineoplastic drugs. 相似文献
986.
V. P. Ryabukho V. L. Khomutov D. V. Lyakin K. V. Konstantinov 《Technical Physics Letters》1998,24(2):132-134
Analogies with interferometers using a light source with low temporal coherence are used to analyze the principles of the
construction of laser interferometers with averaging over the photodetector aperture, whose sensitivity to the position of
an object being monitored at the maximum of the output signal is as good as that of low-coherence interferometry and tomography.
Pis’ma Zh. Tekh. Fiz. 24, 19–24 (February 26, 1998) 相似文献
987.
F Nachon L Ehret-Sabatier D Loew C Colas A van Dorsselaer M Goeldner 《Canadian Metallurgical Quarterly》1998,37(29):10507-10513
Purified butyrylcholinesterase (BuChE) was photolabeled by [3H]-p-N, N-dimethylamino benzene diazonium ([3H]DDF) to identify the quaternary ammonium binding sites on this protein [Ehret-Sabatier, L. , Schalk, I., Goeldner, M., and Hirth, C. (1992) Eur. J. Biochem. 203, 475-481]. The covalent photoincorporation occurs with a stoichiometry of one mole of probe per mole of inactivated site and could be fully prevented by several cholinergic inhibitors such as tacrine or tetramethylammonium. After complete deglycosylation of the enzyme using N-glycosidase F, the alkylated protein was trypsinolyzed and the digests were analyzed by HPLC coupled to ES-MS. A direct comparison of tryptic fragments from labeled and unlabeled BuChE allowed us to identify the tryptic peptide Tyr61-Lys103 as carrying the probe. Purification of the labeled peptides by anion-exchange chromatography gave a major radioactive peak which was further fractionated by reversed-phase HPLC leading to three, well-resolved, radioactive peaks. Microsequencing revealed that two of these peaks contained an overlapping sequence starting at Tyr61, while the third peak contained a sequence extending from Thr315. Radioactive signals could be unambiguously attributed to positions corresponding to residues Trp82 and Tyr332. This labeling study establishes the existence of two different binding domains for quaternary ammonium in BuChE and exemplifies additional cation/pi interactions in cholinergic proteins. This work strongly supports the existence of a peripheral anionic site in BuChE, implying residue Tyr332 as a key element. 相似文献
988.
K Basen-Engquist GS Parcel R Harrist D Kirby K Coyle S Banspach D Rugg 《Canadian Metallurgical Quarterly》1997,67(9):365-371
Randomized trials of school-based health promotion programs present unique design and analytical issues not widely discussed in the research literature. This article describes the Safer Choices study--a school-based program for prevention of HIV, other sexually transmitted diseases, and pregnancy--to illustrate critical methodological issues involved in large-scale, school-based intervention trials, particularly those evaluating interventions with a school-wide focus. The issues presented are: 1) comparability of the intervention and control groups even when few units are randomized; 2) factors that affect the decision to use a cohort or cross-sectional design; and 3) appropriate analysis strategy when the unit of randomization and intervention is at the school level, but observations are at the student level. 相似文献
989.
990.