全文获取类型
收费全文 | 15521篇 |
免费 | 117篇 |
国内免费 | 268篇 |
专业分类
系统科学 | 155篇 |
丛书文集 | 186篇 |
教育与普及 | 196篇 |
理论与方法论 | 51篇 |
现状及发展 | 5159篇 |
研究方法 | 587篇 |
综合类 | 9411篇 |
自然研究 | 161篇 |
出版年
2014年 | 156篇 |
2013年 | 214篇 |
2012年 | 344篇 |
2011年 | 482篇 |
2010年 | 210篇 |
2009年 | 222篇 |
2008年 | 381篇 |
2007年 | 406篇 |
2006年 | 328篇 |
2005年 | 347篇 |
2004年 | 311篇 |
2003年 | 319篇 |
2002年 | 346篇 |
2001年 | 522篇 |
2000年 | 485篇 |
1999年 | 484篇 |
1998年 | 172篇 |
1997年 | 185篇 |
1996年 | 204篇 |
1995年 | 162篇 |
1994年 | 161篇 |
1992年 | 316篇 |
1991年 | 261篇 |
1990年 | 272篇 |
1989年 | 252篇 |
1988年 | 272篇 |
1987年 | 233篇 |
1986年 | 174篇 |
1985年 | 251篇 |
1984年 | 172篇 |
1983年 | 150篇 |
1982年 | 168篇 |
1980年 | 174篇 |
1979年 | 385篇 |
1978年 | 291篇 |
1977年 | 287篇 |
1976年 | 251篇 |
1975年 | 287篇 |
1974年 | 308篇 |
1973年 | 308篇 |
1972年 | 344篇 |
1971年 | 344篇 |
1970年 | 428篇 |
1969年 | 362篇 |
1968年 | 381篇 |
1967年 | 351篇 |
1966年 | 319篇 |
1965年 | 204篇 |
1958年 | 204篇 |
1957年 | 137篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
结合边连通度,本文探讨了3-边连通简单网的独立数与上可嵌人性的关系,我们得到了下列结果:设G是一个3-边连通简单图,α(G)是G的独立数,若α/(G)≤5,则G是上可嵌入的,同时我们又得到了两个在3-边连通意义下最小的非上可嵌入图例. 相似文献
42.
沿海城市以海水为工业用水,其废水经处理后,用标准方法测定COD 时,产生了几十倍甚至于上百倍的正误差,当改用研究的“高氯废水COD 测定方法”测定时,有效地消除了 Cl~-离子对 COD 测定的影响,测定结果的准确度及精密度均符合我国“环境监测技术规范”的规定。 相似文献
43.
44.
Aspirin-like drugs may block pain independently of prostaglandin synthesis inhibition 总被引:2,自引:0,他引:2
K. Brune W. S. Beck G. Geisslinger S. Menzel-Soglowek B. M. Peskar B. A. Peskar 《Cellular and molecular life sciences : CMLS》1991,47(3):257-261
Summary Using flurbiprofen, a chiral anti-inflammatory and analgesic 2-arylpropionic acid derivative, the enantiomers of which are not converted to each other (less than 5%) in rats or man, we obtained evidence that prostaglandin synthesis inhibition is primarily mediating the anti-inflammatory activity but prostaglandin synthesis independent mechanisms contribute to the analgesic effects. Thus, the S-form inhibited prostaglandin synthesis, inflammation and nociception in rats. The R-form had much less effect on prostaglandin synthesis and did not affect inflammation. It did, however, block nociception in rats almost as potently as the S-form. S-flurbiprofen, in contrast to the R-form, was clearly ulcerogenic in the gastrointestinal mucosa. These results indicate additional molecular mechanisms of analgesia and suggest the use of R-arylpropionic acids as analgesics. 相似文献
45.
46.
FROM MANUFACTURING SCHEDULING TO SUPPLY CHAIN COORDINATION:THE CONTROL OF COMPLEXITY AND UNCERTAINTY
Peter B.LUH 《系统科学与系统工程学报(英文版)》2003,12(3):279-297
With time-based competition and rapid technology advancements, effective manufacturingscheduling and supply chain coordination are critical to quickly respond to changing marketconditions. These problems, however, are difficult in view of inherent complexity and variousuncertainties involved. Based on a series of results by the authors, decomposition and coordination byusing Lagrangian relaxation is identified in this paper as an effective way to control complexity anduncertainty.A manufacturing scheduling problem is first formulated within the job shop context withuncertain order arrivals, processing times, due dates, and part priorities as a separable optimizationproblem. A solution methodology that combines Lagrangian relaxation, stochastic dynamicprogramming, and heuristics is developed. Method improvements to effectively solve large problemsare also highlighted. To extend manufacturing scheduling within a factory to coordinate autonomicmembers across chains of suppliers, a decentralized supply chai 相似文献
47.
McCarroll SA Hadnott TN Perry GH Sabeti PC Zody MC Barrett JC Dallaire S Gabriel SB Lee C Daly MJ Altshuler DM;International HapMap Consortium 《Nature genetics》2006,38(1):86-92
The locations and properties of common deletion variants in the human genome are largely unknown. We describe a systematic method for using dense SNP genotype data to discover deletions and its application to data from the International HapMap Consortium to characterize and catalogue segregating deletion variants across the human genome. We identified 541 deletion variants (94% novel) ranging from 1 kb to 745 kb in size; 278 of these variants were observed in multiple, unrelated individuals, 120 in the homozygous state. The coding exons of ten expressed genes were found to be commonly deleted, including multiple genes with roles in sex steroid metabolism, olfaction and drug response. These common deletion polymorphisms typically represent ancestral mutations that are in linkage disequilibrium with nearby SNPs, meaning that their association to disease can often be evaluated in the course of SNP-based whole-genome association studies. 相似文献
48.
萃取浮选光度法测定微量钼的研究及应用 总被引:2,自引:0,他引:2
研究了用甲苯萃取浮选Mo(Ⅴ)—SCN~-—Kφ三元络合物的各种条件。在硫酸介质中,紫红色络合物最大吸收波长位于585nm,摩尔吸光系数为2.8×10~5l·mol~(-1)·cm~(-1),钼量在0—10μg/25ml范围内符合比耳定律。大量常见元素均不干扰,40倍的钨(Ⅵ)亦不干扰钼的测定,方法已应用于钨矿中微量钼的测定,其结果令人满意。 相似文献
49.
M E MacDonald A Novelletto C Lin D Tagle G Barnes G Bates S Taylor B Allitto M Altherr R Myers 《Nature genetics》1992,1(2):99-103
Analysis of 78 Huntington's disease (HD) chromosomes with multi-allele markers revealed 26 different haplotypes, suggesting a variety of independent HD mutations. The most frequent haplotype, accounting for about one third of disease chromosomes, suggests that the disease gene is between D4S182 and D4S180. However, the paucity of an expected class of chromosomes that can be related to this major haplotype by assuming single crossovers may reflect the operation of other mechanisms in creating haplotype diversity. Some of these mechanisms sustain alternative scenarios that do not require a multiple mutational origin for HD and/or its positioning between D4S182 and D4S180. 相似文献