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771.
Correlations between magnetic susceptibility and contents of magnetic minerals in rocks are important in interpreting magnetic anomalies in geophysical exploration and understanding magnetic behaviors of rocks in rock magnetism studies. Previous studies were focused on describing such correlations using a sole expression or a set of expressions through statistical analysis. In this paper, we use neural network techniques to approximate the nonlinear relations between susceptibility and magnetite and/or hematite contents in rocks. This is the first time that neural networks are used for such study in rock magnetism and magnetic petrophysics. Three multilayer perceptrons are trained for producing the best possible estimation on susceptibility based on magnetic contents. These trained models are capable of producing accurate mappings between susceptibility and magnetite and/or hematite contents in rocks. This approach opens a new way of quantitative simulation using neural networks in rock magnetism and petrophysical research and applications. 相似文献
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773.
集成电路(IC)技术的迅速发展,对IC封装提出了越来越苛刻的要求。作为IC的”芯片载体”,IC封装不仅要满足Ic的电磁兼容、物理支撑、热管理等方面的要求,更要保持足够高的性能价格比。技术及市场的需求促使IC封装技术不断进步。 相似文献
774.
基于遗传算法的城市交通运输网优化问题研究 总被引:2,自引:0,他引:2
孙艳丰 《系统工程理论与实践》2000,20(7):94-98
香港是一个市区人口相对集中的城市 ,公路和公共交通运输网的优化非常重要 ,随着经济的发展 ,人口的增加 ,对公共交通设施的需求越来越大 ,每年香港政府都要投资三亿港币建设新的公共交通设施 ,满足日益增长的需求 .这些新的交通设施要从许多公路和公共交通的规划项目中选择 ,这个问题数学上归结为一个 0 -1规划问题 .本文用遗传算法对这一 0 -1规划问题进行了求解 ,这是第一次将遗传算法应用于实际的网络设计问题 ,这一模型将有助于香港政府进行交通规划 ,香港 2 0 0 6年规划数据被用于进行实例研究. 相似文献
775.
Chan VS Chan KY Chen Y Poon LL Cheung AN Zheng B Chan KH Mak W Ngan HY Xu X Screaton G Tam PK Austyn JM Chan LC Yip SP Peiris M Khoo US Lin CL 《Nature genetics》2006,38(1):38-46
Severe acute respiratory syndrome (SARS) is caused by infection of a previously undescribed coronavirus (CoV). L-SIGN, encoded by CLEC4M (also known as CD209L), is a SARS-CoV binding receptor that has polymorphism in its extracellular neck region encoded by the tandem repeat domain in exon 4. Our genetic risk association study shows that individuals homozygous for CLEC4M tandem repeats are less susceptible to SARS infection. L-SIGN is expressed in both non-SARS and SARS-CoV-infected lung. Compared with cells heterozygous for L-SIGN, cells homozygous for L-SIGN show higher binding capacity for SARS-CoV, higher proteasome-dependent viral degradation and a lower capacity for trans infection. Thus, homozygosity for L-SIGN plays a protective role during SARS infection. 相似文献
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Thomas RK Baker AC Debiasi RM Winckler W Laframboise T Lin WM Wang M Feng W Zander T MacConaill L Macconnaill LE Lee JC Nicoletti R Hatton C Goyette M Girard L Majmudar K Ziaugra L Wong KK Gabriel S Beroukhim R Peyton M Barretina J Dutt A Emery C Greulich H Shah K Sasaki H Gazdar A Minna J Armstrong SA Mellinghoff IK Hodi FS Dranoff G Mischel PS Cloughesy TF Nelson SF Liau LM Mertz K Rubin MA Moch H Loda M Catalona W Fletcher J Signoretti S Kaye F Anderson KC Demetri GD Dummer R Wagner S 《Nature genetics》2007,39(3):347-351
Systematic efforts are underway to decipher the genetic changes associated with tumor initiation and progression. However, widespread clinical application of this information is hampered by an inability to identify critical genetic events across the spectrum of human tumors with adequate sensitivity and scalability. Here, we have adapted high-throughput genotyping to query 238 known oncogene mutations across 1,000 human tumor samples. This approach established robust mutation distributions spanning 17 cancer types. Of 17 oncogenes analyzed, we found 14 to be mutated at least once, and 298 (30%) samples carried at least one mutation. Moreover, we identified previously unrecognized oncogene mutations in several tumor types and observed an unexpectedly high number of co-occurring mutations. These results offer a new dimension in tumor genetics, where mutations involving multiple cancer genes may be interrogated simultaneously and in 'real time' to guide cancer classification and rational therapeutic intervention. 相似文献
778.
A genome-wide association scan of tag SNPs identifies a susceptibility variant for colorectal cancer at 8q24.21 总被引:16,自引:0,他引:16
Tomlinson I Webb E Carvajal-Carmona L Broderick P Kemp Z Spain S Penegar S Chandler I Gorman M Wood W Barclay E Lubbe S Martin L Sellick G Jaeger E Hubner R Wild R Rowan A Fielding S Howarth K;CORGI Consortium Silver A Atkin W Muir K Logan R Kerr D Johnstone E Sieber O Gray R Thomas H Peto J Cazier JB Houlston R 《Nature genetics》2007,39(8):984-988
Much of the variation in inherited risk of colorectal cancer (CRC) is probably due to combinations of common low risk variants. We conducted a genome-wide association study of 550,000 tag SNPs in 930 familial colorectal tumor cases and 960 controls. The most strongly associated SNP (P = 1.72 x 10(-7), allelic test) was rs6983267 at 8q24.21. To validate this finding, we genotyped rs6983267 in three additional CRC case-control series (4,361 affected individuals and 3,752 controls; 1,901 affected individuals and 1,079 controls; 1,072 affected individuals and 415 controls) and replicated the association, providing P = 1.27 x 10(-14) (allelic test) overall, with odds ratios (ORs) of 1.27 (95% confidence interval (c.i.): 1.16-1.39) and 1.47 (95% c.i.: 1.34-1.62) for heterozygotes and rare homozygotes, respectively. Analyses based on 1,477 individuals with colorectal adenoma and 2,136 controls suggest that susceptibility to CRC is mediated through development of adenomas (OR = 1.21, 95% c.i.: 1.10-1.34; P = 6.89 x 10(-5)). These data show that common, low-penetrance susceptibility alleles predispose to colorectal neoplasia. 相似文献
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780.