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   9818篇
  免费   310篇
各国政治   473篇
工人农民   328篇
世界政治   886篇
外交国际关系   438篇
法律   5392篇
中国政治   68篇
政治理论   2484篇
综合类   59篇
  2021年   62篇
  2020年   113篇
  2019年   159篇
  2018年   226篇
  2017年   226篇
  2016年   256篇
  2015年   158篇
  2014年   200篇
  2013年   1212篇
  2012年   256篇
  2011年   247篇
  2010年   238篇
  2009年   262篇
  2008年   281篇
  2007年   284篇
  2006年   264篇
  2005年   252篇
  2004年   271篇
  2003年   237篇
  2002年   216篇
  2001年   378篇
  2000年   365篇
  1999年   263篇
  1998年   176篇
  1997年   153篇
  1996年   95篇
  1995年   124篇
  1994年   110篇
  1993年   104篇
  1992年   190篇
  1991年   194篇
  1990年   184篇
  1989年   187篇
  1988年   176篇
  1987年   197篇
  1986年   162篇
  1985年   170篇
  1984年   158篇
  1983年   129篇
  1982年   110篇
  1981年   125篇
  1980年   72篇
  1979年   114篇
  1978年   79篇
  1977年   58篇
  1976年   50篇
  1975年   59篇
  1974年   70篇
  1973年   75篇
  1972年   55篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
861.
Three programs in BASIC and SUPER BASIC language for personal computer are suggested. The first program makes it possible to calculate the degree of substance extraction and factor of its distribution between two liquid immiscible phases. The second program is designed to make calculations on distribution of substance in the organs of experimental animals. The third program is designed to determine specific and molar factors of light absorption. Results of calculations are presented as tables. Programs can be also used in mathematical processing of results obtained in the course of scientific research.  相似文献   
862.
Fifty-eight garments were taped and searched for mid to dark blue wool fibres. These were then removed from the tapings, mounted on slides and examined using a high-power microscope (400x). A total of 2,740 blue wool fibres were identified and visible range microspectrophotometry (MSP) was performed on them. Three hundred independent blue wool populations were identified on 56 of the 58 garments searched. The lack of control fibres meant the spectral range of each population was unknown. The number of populations may have been underestimated by grouping together the fibres that had broad single peaks and a lack of distinguishing features in the spectra. Although blue wool is considered to be a common fibre type, 300 unique spectral shapes were identified by the use of microspectrophotometry alone. This demonstrates that the dyes used in the dyeing of blue wool are variable. Showing that many different populations of blue wool occur on a range of garments should ensure that the forensic scientist does not underestimate or understate the strength of evidence in cases where blue wool is found. Hopefully this work will enlighten scientists and enable them to also assess the true value of their findings when other commonly occurring fibres are encountered.  相似文献   
863.
864.
A simple method was devised to assess dental attrition in terms of its area and number of sites by using dental plaster casts and a computer assisted image analyser. The changes presented on the occlusal surfaces of teeth were investigated for age estimation using these criteria. The area of attrition on each tooth demonstrated a significant positive correlation with age, but a wide individual variation was observed in the values for each tooth. Therefore, this method was unsuitable for accurate age estimation of a single tooth. A strong negative correlation with age was observed in the number of sites of attrition. A multiple stepwise regression analysis using the variables 'attrition area' and 'attrition number' revealed multiple correlation coefficient values of 0.93. The quantitative assessment of both horizontal and vertical factors of dental attrition would be essential to improve the accuracy of this method.  相似文献   
865.
Abstract: A new screening method for detecting gamma-hydroxybutyric acid (GHB) in drink matrices, using the IonSense, Inc. (Saugus, MA) direct analysis in real time (DART) ion source coupled to a JEOL exact mass time-of-flight mass spectrometer (AccuTOF), was validated and compared with the current screening methodology. The DART ion source allows for analysis of samples under ambient conditions with little to no sample preparation. Fifty drink specimens were spiked at levels of 1, 2, 3, and 4 mg/mL GHB, and analyzed on the AccuTOF-DART. Positive detection of GHB occurred for each of the samples at each concentration level, giving 100% accuracy for the samples tested. Twenty-five of the 50 drink specimens were spiked at 1 mg/mL GHB and tested using a color test known as the GHB Color Test #3. Only two of these 25 specimens tested positive for the presence of GHB, giving only 8% accuracy. Implementation of this new methodology as a screening tool for GHB analysis will quickly eliminate negative specimens allowing the examiner to focus analysis time on those that screened positive.  相似文献   
866.
The relation between recession and homicide is classic in the United States. This has been affirmed in the 1976 and 1984 Reports to the Joint Economic Committee (JEC) of the United States Congress. Recent analysis confirms the findings reported in both 1976 and 1984 and demonstrates that the influence of recession on homicide is greater than previously estimated. Differences in the 1976 and 1984 findings on homicide are related to differences in the hypotheses tested, as discussed in detail and highlighted in the 1984 report. JEC staff correctly interpreted and reported the 1984 findings. Reproduction of the 1984 homicide equation is straightforward, provided the same data and any of several standard estimation techniques are used. Evidence does not support any of Cook and Zarkin's claims in their critique of the 1984 homicide equation. The JEC report of 1984 used appropriate techniques in the attempt (a) to ensure that influences attributed to economic changes are not actually due to other social factors and (b) to minimize underspecification of models.  相似文献   
867.
Fluids from frozen muscle tissue taken from 449 white-tailed deer (Odocoileus virginianus) were analyzed using a radioimmunoassay technique for testosterone. Comparing 309 deer sampled in early November, antlered males had significantly higher tissue testosterone levels (range = 0.18 to 16.00 ng/mL) than females (range = 0.00 to 0.18 ng/mL) while antlerless (fawn) males overlapped both groups (range = 0.00 to 0.68 ng/mL). Samples taken from 132 deer from January through August showed no differences among ages or sexes. Antlered males can be differentiated from females during the breeding season.  相似文献   
868.
The intradural sagittal diameter at the second cervical vertebra (SD/C2) of 62 SIDS cases was measured myelographically. This SD/C2 proved to be dependent on body size, body weight, and age. A clear, age-dependent difference is to be found in the primarily narrow spinal canal. This parameter (SD/C2), which is more precisely defined in adults on the basis of clinical, radiological, and autopsical findings is assumed to have the value of 0.5 cm in the first 2 months, 0.6 cm in the third month, and 0.65 cm in the fourth month. The resulting potential danger to infants is dependent upon their position. The SD/C2, was significantly decreased in extension as compared to a neutral posture. With consideration of the primarily narrow spinal canal in the infant, there is, according to our measurements, a potential hazard for the infant in any further, significant shortening of the SD/C2. This is independent of the width of the spinal canal under maximal extension. We found individual cases in which the SD/C2 was decreased by almost 50% from the normal value in neutral position. No correlation was found between the primary width of the spinal canal and the degree of luminal reduction upon extension.  相似文献   
869.
870.
The growth of mass media has complicated the relatioship between the courts and the media. Free press and fair trial rights are kept in balance by the use of judicial restraints and remedies such asvoir dire, change of venue, and gag orders. This balance has shifted back and forth during the past two decades. Current case law and legal codes are inconsistent and provide insufficient guidance to judges in their use of restraints and remedies. Nor is there a body of empirical research on the impact of news coverage and juror behavior capable of informing the courts at this time. In this paper, we review and critically assess the empirical social science literature as it pertains to the legal issues involving free press and fair trial. We argue that carefully conducted empirical research could provide important information to the courts. We suggest research directions and methodological caveats to increase legal relevance and scientific validity.  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