全文获取类型
收费全文 | 10571篇 |
免费 | 169篇 |
国内免费 | 20篇 |
专业分类
电工技术 | 114篇 |
综合类 | 32篇 |
化学工业 | 1148篇 |
金属工艺 | 117篇 |
机械仪表 | 311篇 |
建筑科学 | 248篇 |
矿业工程 | 39篇 |
能源动力 | 194篇 |
轻工业 | 878篇 |
水利工程 | 49篇 |
石油天然气 | 11篇 |
武器工业 | 2篇 |
无线电 | 654篇 |
一般工业技术 | 1269篇 |
冶金工业 | 4824篇 |
原子能技术 | 121篇 |
自动化技术 | 749篇 |
出版年
2022年 | 53篇 |
2021年 | 66篇 |
2020年 | 67篇 |
2019年 | 82篇 |
2018年 | 64篇 |
2017年 | 72篇 |
2016年 | 74篇 |
2015年 | 62篇 |
2014年 | 111篇 |
2013年 | 391篇 |
2012年 | 191篇 |
2011年 | 276篇 |
2010年 | 211篇 |
2009年 | 213篇 |
2008年 | 242篇 |
2007年 | 241篇 |
2006年 | 238篇 |
2005年 | 175篇 |
2004年 | 189篇 |
2003年 | 176篇 |
2002年 | 155篇 |
2001年 | 148篇 |
2000年 | 145篇 |
1999年 | 255篇 |
1998年 | 1479篇 |
1997年 | 830篇 |
1996年 | 624篇 |
1995年 | 353篇 |
1994年 | 313篇 |
1993年 | 366篇 |
1992年 | 139篇 |
1991年 | 143篇 |
1990年 | 148篇 |
1989年 | 152篇 |
1988年 | 127篇 |
1987年 | 149篇 |
1986年 | 139篇 |
1985年 | 140篇 |
1984年 | 114篇 |
1983年 | 91篇 |
1982年 | 95篇 |
1981年 | 135篇 |
1980年 | 120篇 |
1979年 | 101篇 |
1978年 | 87篇 |
1977年 | 168篇 |
1976年 | 305篇 |
1975年 | 82篇 |
1974年 | 50篇 |
1973年 | 73篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
The sector - also known as the proportional, geometric, or military compass - was an analog calculating instrument used widely from the late 16th century until modern times. The origins and usage of this commonly encountered instrument are not well known. This article provides historical background on the sector's invention and on its precursor instruments, and describes the uses for many of the scales commonly found on these instruments. 相似文献
72.
73.
Beutler Larry E.; Williams Rebecca E.; Wakefield Phylis J.; Entwistle Stephanie R. 《Canadian Metallurgical Quarterly》1995,50(12):984
Literature suggests that a complex and often hostile relationship exists between the science and practice of clinical psychology. Contributors to this conflict of viewpoints are reconsidered within the proposition that there are different roads to discovery and that there may be good reasons to keep the science and practice of clinical psychology somewhat separate. Results of a national survey of 325 psychologists are reviewed that support the view that psychological practitioners value research and consider their practices to be augmented by scientific findings. However, they are in need of vehicles of communication that will help them translate scientific findings into practice. Results suggest that practitioners do more to understand scientific findings than scientists do to understand the problems that face clinical practitioners. Ways to facilitate communication between and among these groups are considered. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
74.
75.
A competitive enzyme-linked immunoadsorbent assay (ELISA) technique has been developed to facilitate quantitative analysis of the earliest step in the initiation of the extrinsic pathway of coagulation, i.e., complex formation of factor VII/VIIa with tissue factor. The ELISA measures the binding of biotinylated human plasma factor VII to relipidated recombinant human tissue factor. Quantitation of the relative affinity (expressed as IC50) of any factor VII molecular population or structural analogue for tissue factor can be determined by competitive binding. Subnanomolar concentrations of both wild-type recombinant human factor VII (rFVII) and rFVII(R152Q), a mutation at the FVII activation site, competed effectively with biotinylated plasma-derived factor VII in binding to tissue factor. In contrast, the affinity of rFVII(R79Q), a mutation in the first epidermal growth factor-like domain, was 12-fold lower. Following activation of rFVII(R79Q), its affinity for tissue factor and enzymatic activity increased 4-fold and 6-fold, respectively. For wild-type rFVII, enzymatic activity rose significantly following activation. However, its affinity for tissue factor was unchanged. We conclude that both the activation state of factor VII and the mutation of amino-acid residues within the first epidermal growth factor-like domain may alter the affinity of factor VII for tissue factor. 相似文献
76.
Memory reallocation is used to construct a run-time data structure for fast/efficient storage of information during collection and analysis. The data structure presented uses dynamic memory but does not require the use of pointers to link nodes of information together. It allows for simple and efficient access to data via array indexing rather than through the use of lists or tree structures and it provides flexibility for competing storage requirements that are determined dynamically. The data structure is developed in the C programming language and a suite of ANSI standard C subroutines that make up a run-time data structure management system is provided. 相似文献
77.
Davidson J.D. Wager J.F. Khormaei R.I. King C.N. Williams R. 《Electron Devices, IEEE Transactions on》1992,39(5):1122-1128
Electrical characterization of evaporated ZnS:Mn alternating-current thin-film electroluminescent (ACTFEL) devices is accomplished by capacitance-voltage (C -V ) analysis. Interpretation of these C -V characteristics is aided by SPICE modeling and by electrical characterization of an ideal ACTFEL device constructed from discrete components, based on a simple equivalent circuit for the ACTFEL device. Various features of the C -V curve are ascribed to equivalent circuit parameters and associated device physics parameters 相似文献
78.
A Williams 《Canadian Metallurgical Quarterly》1996,92(14):40-41
This article examines factors that may contribute to errors in drug administration. These can range from the omission of a single dose of a non-essential drug to a major overdose resulting in serious harm to a patient. It concludes that a combination of being observant and well-informed can help to prevent errors. 相似文献
79.
80.
DE Anderson XJ Yuan CM Tseng LJ Rubin GM Rosen ML Tod 《Canadian Metallurgical Quarterly》1993,193(3):878-885
Free radicals react with nitrones to form stable nitroxides which can be identified by ESR spectroscopy. Unfortunately, little is known regarding the pharmacological properties of these compounds. In this study, three commonly used nitrones, 5,5-dimethylpyrroline-N-oxide (DMPO), alpha-phenyl-tert-butylnitrone (PBN), and alpha-(4-pyridyl 1-oxide)-N-tert-butylnitrone (POBN), were found to induce relaxation of preconstricted isolated rat pulmonary artery rings. Additional experiments with PBN indicated that vasorelaxation could not be attributed to production of endothelial derived factors, prostaglandins, or free radicals. Patch-clamp techniques revealed reversible calcium channel blockade with PBN at a concentration below that needed to detect free radicals. Calcium channel blockade probably accounts for the vasorelaxation observed in the isolated ring preparations described here, and should be considered when using nitrone spin-traps both in in vivo and clinical studies. 相似文献