全文获取类型
收费全文 | 73767篇 |
免费 | 2262篇 |
国内免费 | 820篇 |
专业分类
电工技术 | 950篇 |
综合类 | 69篇 |
化学工业 | 12672篇 |
金属工艺 | 3684篇 |
机械仪表 | 2051篇 |
建筑科学 | 1762篇 |
矿业工程 | 222篇 |
能源动力 | 1962篇 |
轻工业 | 7592篇 |
水利工程 | 660篇 |
石油天然气 | 1500篇 |
武器工业 | 5篇 |
无线电 | 5157篇 |
一般工业技术 | 16019篇 |
冶金工业 | 14556篇 |
原子能技术 | 892篇 |
自动化技术 | 7096篇 |
出版年
2023年 | 354篇 |
2022年 | 508篇 |
2021年 | 1083篇 |
2020年 | 923篇 |
2019年 | 1100篇 |
2018年 | 1982篇 |
2017年 | 1932篇 |
2016年 | 2068篇 |
2015年 | 1552篇 |
2014年 | 2003篇 |
2013年 | 4886篇 |
2012年 | 3271篇 |
2011年 | 3554篇 |
2010年 | 2878篇 |
2009年 | 3004篇 |
2008年 | 2823篇 |
2007年 | 2900篇 |
2006年 | 2149篇 |
2005年 | 1871篇 |
2004年 | 1786篇 |
2003年 | 1627篇 |
2002年 | 1598篇 |
2001年 | 1508篇 |
2000年 | 1331篇 |
1999年 | 1413篇 |
1998年 | 4310篇 |
1997年 | 3143篇 |
1996年 | 2394篇 |
1995年 | 1552篇 |
1994年 | 1198篇 |
1993年 | 1283篇 |
1992年 | 785篇 |
1991年 | 765篇 |
1990年 | 669篇 |
1989年 | 628篇 |
1988年 | 517篇 |
1987年 | 524篇 |
1986年 | 475篇 |
1985年 | 515篇 |
1984年 | 424篇 |
1983年 | 392篇 |
1982年 | 423篇 |
1981年 | 428篇 |
1980年 | 491篇 |
1979年 | 412篇 |
1978年 | 368篇 |
1977年 | 663篇 |
1976年 | 1182篇 |
1975年 | 355篇 |
1973年 | 372篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Continuing our work on the immunosuppressive activity of cyclolinopeptide A (CLA), a cyclic nonapeptide of the sequence: c-(-Leu-Ile-Ile-Leu-Val-Pro-Pro-Phe-Phe), we synthesized a series of 6 linear analogs of CLA, successively shortened at the N-terminus of the peptide chain. Immunosuppressive activity of acetates as well as trifluoroacetates of these peptides was investigated using PFC (humoral immunity) and DTH (cellular immunity) tests. It was found that the immunosuppressive potency of the peptides examined diminishes with shortening of the peptide chain. Octapeptide I with the sequence Ile-Ile-Leu-Val-Pro-Pro-Phe-Phe was found to be the most active of the whole series. The immunosuppressive activity increased again for a tripeptide fragment of CLA of the sequence Pro-Phe-Phe. The immunosuppressive activity of octapeptide probably depends on the suppression of IL-1, IL-6 and TNF production by the cells involved in immune and inflammatory response. 相似文献
72.
R. Z. Gataulin 《Chemical and Petroleum Engineering》1992,28(8):519-521
Translated from Khimicheskoe i Neftyanoe Mashinostroenie, No. 8, pp. 31–32, August, 1992. 相似文献
73.
74.
75.
Casacca M.A. Capobianco M.R. Salameh Z.M. 《Energy Conversion, IEEE Transaction on》1996,11(1):139-145
Battery storage is a crucial element in alternative energy and electric vehicle systems. Three battery storage configurations: a conventional; a parallel; and a dual, were analyzed for both shallow cycle and deep cycle lead-acid batteries to determine if capacity improvement is achievable. Daily profiles for the weekly irradiance, daily loads, and ambient temperature are simulated. Cycle tests were performed monthly to determine the effect each configuration had on the available battery capacity. Results for each battery type differ. Available capacity was improved using the parallel configuration with shallow cycle batteries and the dual configuration with deep cycle batteries 相似文献
76.
77.
A simple electrical network is used to represent the five differential equations describing basic phenomena in one-dimensional semiconductor devices. Both standard and integrated approaches for solving transport equations are developed. Also, an electrical network equivalent for the nonlinear Poisson equation was derived. It allows students to better understand the physical phenomena and the process of computer simulation of such semiconductor devices 相似文献
78.
79.
80.
Of 1,666 patients who underwent fine needle aspiration for breast lumps, 4 developed pneumothorax as a complication. The incidence of this complication in our patients is 1:417. The clinical manifestations were immediate chest pain, shoulder pain and, occasionally, dyspnea that developed later. Observation is sufficient treatment in most patients, and rarely is drainage of the pneumothorax required. 相似文献