全文获取类型
收费全文 | 21508篇 |
免费 | 1329篇 |
专业分类
各国政治 | 857篇 |
工人农民 | 1057篇 |
世界政治 | 1456篇 |
外交国际关系 | 716篇 |
法律 | 14741篇 |
中国共产党 | 2篇 |
中国政治 | 132篇 |
政治理论 | 3763篇 |
综合类 | 113篇 |
出版年
2023年 | 108篇 |
2021年 | 110篇 |
2020年 | 474篇 |
2019年 | 512篇 |
2018年 | 665篇 |
2017年 | 680篇 |
2016年 | 769篇 |
2015年 | 565篇 |
2014年 | 616篇 |
2013年 | 2220篇 |
2012年 | 577篇 |
2011年 | 620篇 |
2010年 | 620篇 |
2009年 | 670篇 |
2008年 | 623篇 |
2007年 | 618篇 |
2006年 | 639篇 |
2005年 | 512篇 |
2004年 | 535篇 |
2003年 | 456篇 |
2002年 | 488篇 |
2001年 | 814篇 |
2000年 | 751篇 |
1999年 | 598篇 |
1998年 | 293篇 |
1997年 | 226篇 |
1996年 | 239篇 |
1995年 | 241篇 |
1994年 | 226篇 |
1993年 | 223篇 |
1992年 | 392篇 |
1991年 | 392篇 |
1990年 | 396篇 |
1989年 | 371篇 |
1988年 | 414篇 |
1987年 | 363篇 |
1986年 | 396篇 |
1985年 | 405篇 |
1984年 | 319篇 |
1983年 | 285篇 |
1982年 | 221篇 |
1981年 | 192篇 |
1980年 | 180篇 |
1979年 | 264篇 |
1978年 | 146篇 |
1977年 | 112篇 |
1976年 | 104篇 |
1975年 | 120篇 |
1974年 | 156篇 |
1973年 | 106篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
In the wake of the 1990 amendments to the Clean Air Act, localities across the United States initiated public information campaigns both to raise awareness of threats to air quality and to change behavior related to air pollution by recommending specific behavioral changes in the campaign messages. These campaigns are designed to reduce the health hazards associated with poor air quality and to avoid federal sanctions resulting from the failure to meet air quality standards. As in many other communities across the country, a coalition of government agencies and businesses initiated a public information campaign in the Atlanta metropolitan region to reduce certain targeted behaviors, mainly driving. A two‐stage model used to analyze data from a rolling sample survey shows that the centerpiece of the information campaign—air quality alerts—was effective in raising awareness and reducing driving in a segment of the population. When the overall information campaign was moderated by employers' participation in programs to improve air quality, drivers significantly reduced the number of miles they drove and the number of trips they took by car on days when air quality alerts were sounded. Public information campaigns can be successful in increasing awareness, but changing well‐established behaviors, such as driving, is likely to require institutional mediation to provide social contexts that support the behavioral change, as well. © 2003 by the Association for Public Policy Analysis and Management. 相似文献
92.
Report of an unusual finding of bones on the shore of the Baltic Sea. Although the morphological findings appeared similar to a human foot skeleton, a quick identification as sea dog bone was possible. 相似文献
93.
On the one hand the following case demonstrates the problems of finding a dead body in the bathroom and on the other hand the importance of postmortem x-ray examinations. The corpse of an 65-year-old woman was discovered in her bath tub. At the body's feet there was a hair dryer. Investigations concerning murder were negative, circumstances appeared to be unsuspicious. That was why a postmortem examination was not performed. -4 years later murder had to be considered. After manual strangling the deceased and the hair dryer were layed into the bath tub. The corpse was exhumed and taken to a forensic autopsy. It was found that the hyoid bone and the superior horn of the thyroid cartilage were both fractured on the right. Damages caused by the preparation itself were excluded by using serial roentgenographs. These observations in combination with histological findings and the results of further investigations convincingly supported the suspicion of strangling by hand. 相似文献
94.
In many countries it is left to the discretion of the court to accept or reject conclusions based on sampling procedures as applied to the total drug exhibit. As an alternative to this subjective approach, a statistical basis is presented using binomial and hypergeometric distributions to determine a lower limit for the proportion of units in a population which contains a drug, at a given confidence level. A method for calculating the total weight of a drug present in a population within a given confidence interval is also presented. In the event of no failures (all units sampled contain a drug), a sample size of six or seven units is generally sufficient to state that a proportion of at least 0.70 of the population contains a drug at a confidence level of at least 90%. When failures do occur in the sample, point estimation is used as the basis for selecting the appropriate sample size. 相似文献
95.
Y Aoki H Terunuma Y Iwasaki M Nata K Sagisaka 《The American journal of forensic medicine and pathology》1992,13(3):199-203
A case of the sudden death of a 14-month-old girl due to massive hemorrhage in a primitive neuroectodermal tumor (PNET) is presented along with a review of the relevant literature. PNET is a rare, malignant brain neoplasm occurring predominantly in children. 相似文献
96.
97.
An improved method has been developed for the reliable classification of different C1R genetic variant forms from human serum or plasma. The method combines the use of neuraminidase-digested samples followed by monodimensional isoelectric focusing in the pH range 5 to 8 followed by immunoblotting. The method yields a simple pattern, with one major band in homozygote and two major bands in heterozygote cases. 相似文献
98.
Dilutions of 100 serum samples of various GM phenotypes were dotted onto a nitrocellulose membrane. The serum dot-blots were detected with peroxidase-labeled anti-G3M T monoclonal antibody (anti-G3M T MAb). Up to a 1 : 256 dilution could be G3M T-typed correctly. By use of anti-G3M T MAb and peroxidase-labeled anti-mouse IgG or the biotin-avidin system instead of use of labeled anti-G3M T MAb, up to a 1 : 512 or 1 : 1024, respectively, dilution was typable. As with previous work with G3M G MAb, the dot immunobinding (DIB) method for G3M T typing was found very simple and practical. 相似文献
99.
M Moniri 《Journal of forensic sciences》1990,35(1):181-185
A technique was developed for Gm/Km typing of bloodstains and sera in U-bottom microtiter plates. Gm/Km typing of sweat and urine samples was also attempted with limited success. 相似文献
100.