全文获取类型
收费全文 | 5485篇 |
免费 | 36篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 30篇 |
化学工业 | 327篇 |
金属工艺 | 26篇 |
机械仪表 | 35篇 |
建筑科学 | 116篇 |
矿业工程 | 7篇 |
能源动力 | 48篇 |
轻工业 | 248篇 |
水利工程 | 42篇 |
石油天然气 | 12篇 |
无线电 | 182篇 |
一般工业技术 | 310篇 |
冶金工业 | 3779篇 |
原子能技术 | 24篇 |
自动化技术 | 336篇 |
出版年
2022年 | 16篇 |
2021年 | 17篇 |
2019年 | 22篇 |
2018年 | 23篇 |
2017年 | 21篇 |
2016年 | 29篇 |
2015年 | 22篇 |
2014年 | 40篇 |
2013年 | 103篇 |
2012年 | 70篇 |
2011年 | 84篇 |
2010年 | 64篇 |
2009年 | 91篇 |
2008年 | 85篇 |
2007年 | 85篇 |
2006年 | 79篇 |
2005年 | 61篇 |
2004年 | 75篇 |
2003年 | 78篇 |
2002年 | 57篇 |
2001年 | 62篇 |
2000年 | 56篇 |
1999年 | 138篇 |
1998年 | 1149篇 |
1997年 | 645篇 |
1996年 | 448篇 |
1995年 | 275篇 |
1994年 | 207篇 |
1993年 | 223篇 |
1992年 | 61篇 |
1991年 | 78篇 |
1990年 | 79篇 |
1989年 | 66篇 |
1988年 | 61篇 |
1987年 | 76篇 |
1986年 | 64篇 |
1985年 | 57篇 |
1984年 | 37篇 |
1983年 | 32篇 |
1982年 | 39篇 |
1981年 | 40篇 |
1980年 | 38篇 |
1979年 | 17篇 |
1978年 | 16篇 |
1977年 | 85篇 |
1976年 | 194篇 |
1975年 | 23篇 |
1974年 | 18篇 |
1973年 | 21篇 |
1972年 | 14篇 |
排序方式: 共有5522条查询结果,搜索用时 593 毫秒
1.
2.
Sama Rezasoltani Reza Ghanbari Mehdi Azizmohammad Looha Ehsan Nazemalhosseini Mojarad Abbas Yadegar Delisha Stewart Hamid Asadzadeh Aghdaei Mohammad Reza Zali 《International journal of molecular sciences》2020,21(23)
Abnormal activation of Toll-like receptor (TLRs) signaling can result in colon cancer development. The aim of this study was to investigate the expression of important TLRs in different histological types of colorectal polyps and evaluate their relationship with intestinal microbiota. The expression levels of TLR2, 3, 4, and 5 were analyzed in intestinal biopsy specimens of 21 hyperplastic polyp (HP), 16 sessile serrated adenoma (SSA), 29 tubular adenoma (TA), 21 villous/tubulovillous (VP/TVP) cases, and 31 normal controls. In addition, selected gut bacteria including Streptococcus bovis, Enterococcus faecalis, Enterotoxigenic Bacteroides fragilis (ETBF), Fusobacterium nucleatum, Porphyromonas spp., Lactobacillus spp., Roseburia spp., and Bifidobacterium spp. were quantified in fecal samples using absolute qRT PCR, and, finally, the association between TLRs and these gut microbiota- was evaluated by Spearman’s correlation coefficient. Higher expression of TLR2 and TLR4 in VP/TVP and TA, and lower expression levels of TLR3 and TLR5 in all type of polyps were observed. The differences in TLR expression patterns was not only dependent on the histology, location, size, and dysplasia grade of polyps but also related to the intestinal microbiota patterns. TLR2 and TLR4 expression was directly associated with the F. nucleatum, E. faecalis, S. bovis, Porphyromonas, and inversely to Bifidobacterium, Lactobacillus, and Roseburia quantity. Furthermore, TLR3 and TLR5 expression was directly associated with Bifidobacterium, Roseburia, and Lactobacillus quantity. Our results suggest a possible critical role of TLRs during colorectal polyp progression. An abnormal regulation of TLRs in relation to gut microbial quantity may contribute to carcinogenesis. 相似文献
3.
4.
Stewart C. Kai Shen Dwarkadas S. Scott M.L. Jian Yin 《Distributed Systems Online, IEEE》2004,5(10):1-1
The growth of the Internet and of various intranets has spawned a wealth of online services, most of which are implemented on local-area clusters using remote invocation (for example, remote procedure call/remote method invocation) among manually placed application components. Component placement can be a significant challenge for large-scale services, particularly when application resource needs are workload dependent. Automatic component placement has the potential to maximize overall system throughput. The key idea is to construct (offline) a mapping between input workload and individual-component resource consumption. Such mappings, called component profiles, then support high-performance placement. Preliminary results on an online auction benchmark based on J2EE (Java 2 Platform, Enterprise Edition) suggest that profile-driven tools can identify placements that achieve near-optimal overall throughput. 相似文献
5.
Thomas S. Lowry John C. Bright Murray E. Close Christina A. Robb Paul A. White Stewart G. Cameron 《国际水资源开发杂志》2003,19(4):579-592
The primary objective of this project is to identify gaps, whether real or perceived, that hinder effective groundwater management in New Zealand. These gaps show as gaps in information, gaps in implementation, gaps in technological and management tools, and gaps in understanding of fundamental processes. The secondary objective is to propose a management strategy to close the identified gaps. Several methods are used to meet these objectives: surveys distributed to selected staff in each regional council; the review of various written reports; the analysis of land-use databases; and private consultation within each regional council. Results show that groundwater management in New Zealand is generally reactionary with the main gaps being in strategic planning and national guidelines. Most gaps appear to be predominantly information and implementation issues. In some cases there are gaps in the understanding of fundamental processes within an aquifer system, including the long-term effects of land-use on groundwater quality. An adaptive management approach is suggested as a means of closing these gaps. 相似文献
6.
A coupled cell system is a network of dynamical systems, or 'cells', coupled together. Such systems can be represented schematically by a directed graph whose nodes correspond to cells and whose edges represent couplings. A symmetry of a coupled cell system is a permutation of the cells and edges that preserves all internal dynamics and all couplings. It is well known that symmetry can lead to patterns of synchronized cells, rotating waves, multirhythms, and synchronized chaos. Recently, the introduction of a less stringent form of symmetry, the 'symmetry groupoid', has shown that global group-theoretic symmetry is not the only mechanism that can create such states in a coupled cell system. The symmetry groupoid consists of structure-preserving bijections between certain subsets of the cell network, the input sets. Here, we introduce a concept intermediate between the groupoid symmetries and the global group symmetries of a network: 'interior symmetry'. This concept is closely related to the groupoid structure, but imposes stronger constraints of a group-theoretic nature. We develop the local bifurcation theory of coupled cell systems possessing interior symmetries, by analogy with symmetric bifurcation theory. The main results are analogues for 'synchrony-breaking' bifurcations of the Equivariant Branching Lemma for steady-state bifurcation, and the Equivariant Hopf Theorem for bifurcation to time-periodic states. 相似文献
7.
FJ Overdyk PM Gramling-Babb JR Handy NI Faller MJ Miller 《Canadian Metallurgical Quarterly》1997,84(1):213-215
Robertsonian translocations, although relatively common as a constitutional genetic aberration, are rarely encountered in leukaemia. We report a case of acute myeloid leukaemia which showed an acquired Robertsonian translocation in the form of der(14;21) by cytogenetic analysis of leukaemic cells. This was confirmed by the PHA-stimulated culture of peripheral blood lymphocytes. A review of the literature identifies only eight reported cases of acquired Robertsonian translocations in leukaemia. In the majority of cases the Robertsonian translocation occurs as a secondary change in a complex abnormal clone, whereas in two out of nine patients reported, including ours, it is found as a sole karyotypic abnormality. 相似文献
8.
Stewart L. Stokes Jr. 《Information Systems Management》1994,11(3):34-40
Mentoring has been around for ages, often masquerading as the management club or the fast track. Among successful business unit managers, mentoring is a well-understood practice, and it's a career development strategy today's IS professional would be wise to consider. 相似文献
9.
Twenty-six patients with an intracardiac myxoma underwent surgical resection at our institution from 1977 through 1992. Left atrial myxoma was diagnosed in 22 patients, left ventricular in 1, right atrial in 2, and right ventricular in 1. Six patients were asymptomatic; preoperative symptoms included dyspnea, arrhythmias, embolic episodes, and syncope. The diagnosis was established with transthoracic echocardiography in all cases but one. Surgery was performed in all cases with the aid of cardiopulmonary bypass with moderate hypothermia and cold crystalloid cardioplegia. One patient with a left ventricular myxoma died in a comatose state during the immediate postoperative period. Long-term clinical and echocardiographic evaluation was performed in 19 patients; results were excellent (all the patients were in New York Heart Association functional class I or II), and no recurrences were documented. The clinical characteristics, diagnostic methods, and surgical approach are presented and discussed. 相似文献
10.