首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   10377篇
  免费   374篇
  国内免费   530篇
系统科学   402篇
丛书文集   256篇
教育与普及   201篇
理论与方法论   29篇
现状及发展   51篇
研究方法   48篇
综合类   10292篇
自然研究   2篇
  2024年   79篇
  2023年   145篇
  2022年   191篇
  2021年   235篇
  2020年   156篇
  2019年   82篇
  2018年   97篇
  2017年   133篇
  2016年   145篇
  2015年   254篇
  2014年   327篇
  2013年   295篇
  2012年   337篇
  2011年   408篇
  2010年   385篇
  2009年   424篇
  2008年   464篇
  2007年   551篇
  2006年   407篇
  2005年   496篇
  2004年   310篇
  2003年   235篇
  2002年   280篇
  2001年   305篇
  2000年   314篇
  1999年   509篇
  1998年   479篇
  1997年   520篇
  1996年   453篇
  1995年   365篇
  1994年   331篇
  1993年   282篇
  1992年   291篇
  1991年   231篇
  1990年   232篇
  1989年   192篇
  1988年   152篇
  1987年   113篇
  1986年   61篇
  1985年   10篇
  1984年   1篇
  1978年   2篇
  1968年   1篇
  1957年   1篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
Lin Z  Bei JX  Shen M  Li Q  Liao Z  Zhang Y  Lv Q  Wei Q  Low HQ  Guo YM  Cao S  Yang M  Hu Z  Xu M  Wang X  Wei Y  Li L  Li C  Li T  Huang J  Pan Y  Jin O  Wu Y  Wu J  Guo Z  He P  Hu S  Wu H  Song H  Zhan F  Liu S  Gao G  Liu Z  Li Y  Xiao C  Li J  Ye Z  He W  Liu D  Shen L  Huang A  Wu H  Tao Y  Pan X  Yu B  Tai ES  Zeng YX  Ren EC  Shen Y  Liu J  Gu J 《Nature genetics》2012,44(1):73-77
To identify susceptibility loci for ankylosing spondylitis, we performed a two-stage genome-wide association study in Han Chinese. In the discovery stage, we analyzed 1,356,350 autosomal SNPs in 1,837 individuals with ankylosing spondylitis and 4,231 controls; in the validation stage, we analyzed 30 suggestive SNPs in an additional 2,100 affected individuals and 3,496 controls. We identified two new susceptibility loci between EDIL3 and HAPLN1 at 5q14.3 (rs4552569; P = 8.77 × 10(-10)) and within ANO6 at 12q12 (rs17095830; P = 1.63 × 10(-8)). We also confirmed previously reported associations in Europeans within the major histocompatibility complex (MHC) region (top SNP, rs13202464; P < 5 × 10(-324)) and at 2p15 (rs10865331; P = 1.98 × 10(-8)). We show that rs13202464 within the MHC region mainly represents the risk effect of HLA-B*27 variants (including HLA-B*2704, HLA-B*2705 and HLA-B*2715) in Chinese. The two newly discovered loci implicate genes related to bone formation and cartilage development, suggesting their potential involvement in the etiology of ankylosing spondylitis.  相似文献   
72.
Hu Z  Xia Y  Guo X  Dai J  Li H  Hu H  Jiang Y  Lu F  Wu Y  Yang X  Li H  Yao B  Lu C  Xiong C  Li Z  Gui Y  Liu J  Zhou Z  Shen H  Wang X  Sha J 《Nature genetics》2012,44(2):183-186
Non-obstructive azoospermia (NOA) is one of the most severe forms of male infertility. Its pathophysiology is largely unknown, and few genetic influences have been defined. To identify common variants contributing to NOA in Han Chinese men, we performed a three-stage genome-wide association study of 2,927 individuals with NOA and 5,734 controls. The combined analyses identified significant (P < 5.0 × 10(-8)) associations between NOA risk and common variants near PRMT6 (rs12097821 at 1p13.3: odds ratio (OR) = 1.25, P = 5.7 × 10(-10)), PEX10 (rs2477686 at 1p36.32: OR = 1.39, P = 5.7 × 10(-12)) and SOX5 (rs10842262 at 12p12.1: OR = 1.23, P = 2.3 × 10(-9)). These findings implicate genetic variants at 1p13.3, 1p36.32 and 12p12.1 in the etiology of NOA in Han Chinese men.  相似文献   
73.
Gui Y  Guo G  Huang Y  Hu X  Tang A  Gao S  Wu R  Chen C  Li X  Zhou L  He M  Li Z  Sun X  Jia W  Chen J  Yang S  Zhou F  Zhao X  Wan S  Ye R  Liang C  Liu Z  Huang P  Liu C  Jiang H  Wang Y  Zheng H  Sun L  Liu X  Jiang Z  Feng D  Chen J  Wu S  Zou J  Zhang Z  Yang R  Zhao J  Xu C  Yin W  Guan Z  Ye J  Zhang H  Li J  Kristiansen K  Nickerson ML  Theodorescu D  Li Y  Zhang X  Li S  Wang J  Yang H  Wang J  Cai Z 《Nature genetics》2011,43(9):875-878
Transitional cell carcinoma (TCC) is the most common type of bladder cancer. Here we sequenced the exomes of nine individuals with TCC and screened all the somatically mutated genes in a prevalence set of 88 additional individuals with TCC with different tumor stages and grades. In our study, we discovered a variety of genes previously unknown to be mutated in TCC. Notably, we identified genetic aberrations of the chromatin remodeling genes (UTX, MLL-MLL3, CREBBP-EP300, NCOR1, ARID1A and CHD6) in 59% of our 97 subjects with TCC. Of these genes, we showed UTX to be altered substantially more frequently in tumors of low stages and grades, highlighting its potential role in the classification and diagnosis of bladder cancer. Our results provide an overview of the genetic basis of TCC and suggest that aberration of chromatin regulation might be a hallmark of bladder cancer.  相似文献   
74.
五味子对心血管、免疫系统及CNS具有调节作用,阐述了五味子中有效成分木脂素和多糖保护心室重构的作用.  相似文献   
75.
Particle Filter(PF) is a data assimilation method to solve recursive state estimation problem which does not depend on the assumption of Gaussian noise, and is able to be applied for various systems even with non-linear and non-Gaussian noise. However, while applying PF in dynamic systems, PF undergoes particle degeneracy,sample impoverishment, and problems of high computational complexity. Rapidly developing sensing technologies are providing highly convenient availability of real-time big traffic data from the system under study like never before. Moreover, some sensors can even receive control commands to adjust their monitoring parameters. To address these problems, a bidirectional dynamic data-driven improvement framework for PF(B3 DPF) is proposed.The B3 DPF enhances feedback between the simulation model and the big traffic data collected by the sensors,which means the execution strategies(sensor data management, parameters used in the weight computation,resampling) of B3 DPF can be optimized based on the simulation results and the types and dimensions of traffic data injected into B3 DPF can be adjusted dynamically. The first experiment indicates that the B3 DPF overcomes particle degeneracy and sample impoverishment problems and accurately estimates the state at a faster speed than the normal PF. More importantly, the new method has higher accuracy for multidimensional random systems.In the rest of experiments, the proposed framework is applied to estimate the traffic state on a real road network and obtains satisfactory results. More experiments can be designed to validate the universal properties of B3 DPF.  相似文献   
76.
A new type of vocoder system based upon formant analysis is presented in this paper. The LMS adaptive algorithm is used for tracking formants of speech signals. The results of computer simulation show that the new vocoder has better synthesized speech quality.  相似文献   
77.
本文介绍了阶段原型法(SPA)及其支持环境(PEMIS)的总体结构和主要功能,探讨了知识库和推理机制在循环控制中的作用,以及软件重用技术、图形接口技术和应用生成技术等实现技术。  相似文献   
78.
本文作者曾对UNIX分时操作系统第六版和第七版的核心代码作过分析,尔后又对该系统的几个重要的外围程序和工具性程序做了解剖。UNIX初始化程序(包括init,getty和login)规模小、结构简单;但是,对初始化过程的深入了解,有助于理解系统活动的全过程,同时也是分析其他程序(如Shell)所不可缺少的准备。  相似文献   
79.
低糖白茶饮料的研制   总被引:2,自引:0,他引:2  
本试验以福鼎白茶为主要原料开发低糖白茶饮料.首先通过茶水比、温度、时间三个因素设计正交试验,并根据正交试验的结果确定最佳浸提条件;其次将根据此最佳浸提条件得到的茶汤按一定的浓度梯度加入去离子水稀释,确定最佳稀释量;然后在上述最佳条件所得到的茶汤中加入不同浓度组合的辅料白砂糖和维生素C并确定最佳添加量;最后经杀菌制得天然低糖白茶饮料.  相似文献   
80.
调和测度     
“调和”这个概念在数学中有多种意义,本书所讲的调和测度来源于解偏微分方程有关Laplace方程的Dirichlet问题。Dirichlet问题的解称为调和函数,如果它在边界上等于给定的函数。最简单的情形是平面区域,可以定义区域边界的子集在某点的调和测度来解决系列单复变函数和位势理论的问题。这样,调和测度成为重要的理论工具。近20多年,在这方面有突破性进展,本书就是介绍这些进展的专著。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号