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   5384篇
  免费   72篇
  国内免费   21篇
教育   3623篇
科学研究   710篇
各国文化   31篇
体育   422篇
综合类   11篇
文化理论   35篇
信息传播   645篇
  2022年   39篇
  2021年   47篇
  2020年   93篇
  2019年   129篇
  2018年   169篇
  2017年   200篇
  2016年   161篇
  2015年   124篇
  2014年   172篇
  2013年   842篇
  2012年   147篇
  2011年   156篇
  2010年   129篇
  2009年   115篇
  2008年   128篇
  2007年   149篇
  2006年   112篇
  2005年   81篇
  2004年   97篇
  2003年   93篇
  2002年   73篇
  2001年   119篇
  2000年   135篇
  1999年   98篇
  1998年   82篇
  1997年   70篇
  1996年   63篇
  1995年   46篇
  1994年   50篇
  1993年   35篇
  1992年   80篇
  1991年   69篇
  1990年   66篇
  1989年   69篇
  1988年   80篇
  1987年   62篇
  1986年   81篇
  1985年   72篇
  1984年   58篇
  1983年   71篇
  1982年   55篇
  1981年   42篇
  1980年   38篇
  1979年   57篇
  1978年   55篇
  1977年   44篇
  1976年   48篇
  1975年   34篇
  1974年   35篇
  1973年   35篇
排序方式: 共有5477条查询结果,搜索用时 6 毫秒
91.
This article serves as an introduction to log-linear analysis, a technique used in the analysis of qualitative data arranged in multidimensional contingency tables. The steps involved in log-linear analysis are presented in the context of an investigation of a personality characteristic of a group of counselor trainees. The references cited and supplemental readings allow interested readers to pursue the topic further.  相似文献   
92.
Selecting the correct method for routine analysis by ‘method evaluation’ is an important component of quality assurance. It is a step-wise procedure that evaluates various analytical parameters like accuracy, precision etc of the given method. Finally reference intervals are established for selected population. We evaluated an enzymatic method for serum creatinine. The results show that it is an acceptable method based on the above mentioned criteria.  相似文献   
93.
Sialic acid, the end moieties of the carbohydrate chains are biologically important and essential for functions of glycoconjugates and are reported to be altered in cancer patients. Two hundred and twenty five breast cancer (BC) patients, 100 patients with benign breast disease (BBD) and 100 healthy females (controls) were enrolled for the study. Eight hundred and twenty four follow-up samples of 225 breast carcinoma patients were also evaluated. The association of sialic acid forms, sialyltransferase and α-2–6 sialoproteins levels with presence and extent as well as prognosis of breast carcinoma was studied. Serum sialic acid forms and sialyltransferase revealed significantly elevated levels among untreated breast cancer patients as compared to the controls, patients with BBD as well as cancer patients in remission. Non-responders showed comparable levels of the markers with those found in breast cancer patients at the time of diagnosis. Higher levels of sialic acid forms at diagnosis were associated with poor prognosis. A positive correlation between serum levels of different forms of sialic acids and extent of malignant disease was observed. The changes in serum proteins with terminal α-2–6 sialic acid correlated well with alterations in the levels of sialic acid forms and sialyltransferase. Malignant tissues showed elevated levels of sialic acid and sialyltransferase as compared to surrounding normal tissues. The results suggested potential utility of these markers in evaluation of clinical outcome.  相似文献   
94.
Membrane hydrophobicity and slalidase activity of normal Poly morphonuclear Leucocyte were significantly enhanced when incubated with DSF. As a consequence, internalisation ofE. coli andS. aureus (opsonised or unopsonised) were greatly dimnished, internalisation ofE. coli being higher in either category. Although, increase in hydrophobicity of the membrane correlated well with the time of decrease of particle internalisation (both at 30 min.), enhancement of sialidase activity did not coincide with the said alterations.  相似文献   
95.
Several methods of detecting the presence of various chemical species are considered. A specific example of atomic hydrogen in lead selenide is examined and used to illustrate some important principles.  相似文献   
96.
Prostate Specific Antigen (PSA) has emerged as the most applicable and important tumor marker for carcinoma prostate. In the present study PSA was determined in serum of healthy subjects, patients of benign prostate hypertrophy (BPH) and Carcinoma Prostate (Ca−P) to evaluate its diagnostic efficiency in day to day management of prostate cancer patients and in differentiating patients of early prostate cancer from those with BPH. Receiver operating characteristic curve (ROC) revealed 2 ng/ml and 10 ng/ml cut off serum PSA level for BPH and untreated carcinoma prostate patients (Ca−P). An extremely significant increase (P<0.0001) was observed in mean PSA concentration in BPH patients and adenocarcinoma prostate patients when compared to healthy males. Clinical relevance of PSA was highlighted by a case study of cancer patient prior to any therapy till death.  相似文献   
97.
我国各地区现代化进程研究   总被引:4,自引:0,他引:4  
本文根据国际通行的现代化指标体系计算了中国大陆31个省市区的各项现代化指标的重分,采用主成分分析法和聚类分析法评估了各省市区的现代化水平及其分级和分类特征,并在此基础上分析了我国现代化水平的整体特点及地域分异特点。  相似文献   
98.
The performance of parallel query processing in a cluster of index servers is crucial for modern web search systems. In such a scenario, the response time basically depends on the execution time of the slowest server to generate a partial ranked answer. Previous approaches investigate performance issues in this context using simulation, analytical modeling, experimentation, or a combination of them. Nevertheless, these approaches simply assume balanced execution times among homogeneous servers (by uniformly distributing the document collection among them, for instance)—a scenario that we did not observe in our experimentation. On the contrary, we found that even with a balanced distribution of the document collection among index servers, correlations between the frequency of a term in the query log and the size of its corresponding inverted list lead to imbalances in query execution times at these same servers, because these correlations affect disk caching behavior. Further, the relative sizes of the main memory at each server (with regard to disk space usage) and the number of servers participating in the parallel query processing also affect imbalance of local query execution times. These are relevant findings that have not been reported before and that, we understand, are of interest to the research community.  相似文献   
99.
李娜  刘洋  李玉乐  孙静 《编辑学报》2020,32(2):177-180
随着泛在网络时代的到来,新媒体已成为人们获取健康知识的首要途径;但当前网络健康知识来源芜杂,各种夸大甚至歪曲医学事实的报道层出不穷,健康科普的“含金量”亟须提高。临床医学期刊是权威医学成果发布和交流的重要平台,拥有由作者、审者和编者等众多优秀医学专业工作者组成的专家团队,具有天然的健康科普优势和媒体属性。《协和医学杂志》通过将医学论文科普化、捕捉新闻热点、培养科普人才、充分利用新媒体平台等途径,证明临床医学期刊有责任更有能力在健康科普中发挥重要作用。  相似文献   
100.
We document some basic facts about how liquids behave in the low gravity of outer space and how this poses challenges to space scientists and engineers who need to design and test systems that handle fluids in outer space while working in the 1-g environment on Earth. N Ananthkrishnan is Director, Coral Digital Technologies (P) Ltd, a Bangalore-based company working in the area of multidisciplinary simulation and system integration of aerospace, naval and surface vehicles, and in the design and development of autonomous unmanned/micro air vehicles.  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