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   25715篇
  免费   1030篇
各国政治   1282篇
工人农民   1003篇
世界政治   1926篇
外交国际关系   912篇
法律   15873篇
中国共产党   6篇
中国政治   243篇
政治理论   5314篇
综合类   186篇
  2020年   376篇
  2019年   461篇
  2018年   574篇
  2017年   668篇
  2016年   675篇
  2015年   533篇
  2014年   581篇
  2013年   2752篇
  2012年   612篇
  2011年   775篇
  2010年   644篇
  2009年   674篇
  2008年   699篇
  2007年   641篇
  2006年   688篇
  2005年   612篇
  2004年   636篇
  2003年   618篇
  2002年   552篇
  2001年   957篇
  2000年   912篇
  1999年   686篇
  1998年   417篇
  1997年   352篇
  1996年   324篇
  1995年   295篇
  1994年   320篇
  1993年   322篇
  1992年   491篇
  1991年   497篇
  1990年   475篇
  1989年   482篇
  1988年   476篇
  1987年   471篇
  1986年   508篇
  1985年   468篇
  1984年   427篇
  1983年   436篇
  1982年   281篇
  1981年   265篇
  1980年   226篇
  1979年   303篇
  1978年   214篇
  1977年   192篇
  1976年   184篇
  1975年   146篇
  1974年   175篇
  1973年   179篇
  1972年   170篇
  1969年   129篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
A gas chromatographic (GC) fingerprint method, based on the presence or absence of six congeners, was developed for illicit cocaine samples. The fingerprint utilizes the relative abundances of these congeners towards each other, disregarding cocaine as the main constituent, and can be expressed numerically or graphically in the form of pictograms for rapid visual comparison. The method can be applied directly to a solution of the sample in chloroform, without previous workup procedures. More than 70 unrelated samples were analyzed and a great variation was observed in the parameter composition. On the other hand, a remarkable similarity could be seen between related samples. The GC fingerprint method may be considered an important contribution for sample comparison, as is exemplified by a subdivision of the analyzed samples in different categories, based on the number and types of congeners found.  相似文献   
112.
We report a case of rapid death from thrombotic thrombocytopaenic purpura (TTP) in a young pregnant lady who developed full blown symptoms soon after caesarean section. Extensive intramyocardial confluent haemorrhages and widespread microthrombi in heart, brain, adrenals and kidney were found at autopsy. Thrombotic thrombocytopaenic purpura is an uncommon condition, which carries a high fatality rate if untreated. Awareness of this syndrome together with its high risk of sudden death underlines the importance of rapid diagnosis and treatment.  相似文献   
113.
A new solid-phase extraction procedure for the determination of cocaine and benzoylecgonine in amniotic fluid, using high flow co-polymeric sorbents is reported. The recoveries of cocaine and benzoylecgonine within the range 0.1-1 mg/l were 95.7% and 50.3%, respectively. The use of high-flow sorbents allowed the easy extraction of amniotic fluid regardless of sample viscosity or physical nature. The use of these solid-phase columns provided many advantages over the more commonly used solvent extraction, including an increase in extraction speed and efficiency, reduced operator time, reduced solvent use and disposal volumes and exceptional extract quality. Further, the determination of amniotic fluid obtained from pregnant cocaine users may provide important information about handling of cocaine by the fetus at various gestational ages. The procedure was successfully applied to amniotic fluid from suspected cocaine abusers.  相似文献   
114.
The polymerase chain reaction (PCR) method of specific gene amplification was used in casework to synthesize millions of copies of the polymorphic second exon of the human leukocyte antigen (HLA)-DQ alpha (or DQA1) locus from a variety of evidence samples. The HLA-DQ alpha allelic variants in the amplified deoxyribonucleic acid (DNA) were determined in a rapid non-radioactive test by hybridization to sequence-specific oligonucleotide probes in both the dot-blot and reverse dot-blot formats. This genetic typing system has been subjected to blind proficiency testing; the performance of this test in the analysis of experimentally mixed samples was also evaluated. As of August 1990, over 250 cases have been tested and more than 2000 individual evidence (bloodstains, semen stains, individual hairs, bone fragments, and tissue sections) and reference samples have been analyzed. The first 198 of these cases are summarized in this paper; in 65% of the cases with conclusive results a suspect was included, and in 35%, all suspects were excluded. Individual cases as well as some of the general issues relating to forensic science analysis and this genetic typing system are discussed. The high rate of exclusion reported here combined with the ability of PCR to type old evidence samples suggests the relevance of this genetic test for postconviction review; two cases in which the convicted suspect was excluded are discussed.  相似文献   
115.
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   
116.
Alcoholism and drug addiction affects the entire family. At least 22 million Americans have been raised in an alcoholic environment. Parental alcoholism and/or addiction can have profound emotional and psychological scars on the children. These homes are often characterized by emotional and or physical insecurity, loneliness, terror and inconsistency. The children from these homes often are extremely insecure have low self-esteem, and have a variety of emotional problems. Adolescents from addictive homes are over-represented in juvenile court as status offenders, delinquents and abuse and neglect cases. This article will discuss this issue and implications for the juvenile justice system and personnel working with these youth  相似文献   
117.
Postmortem changes in sulfide concentrations in body tissues were examined in autopsied rats exposed to hydrogen sulfide concentrations of 550 to 650 ppm, and in nonexposed rats and humans. Analyses were made by gas chromatography, following an extractive alkylation. Sulfide concentrations in the blood, liver, and kidneys of rats increased in both the exposed and nonexposed groups, depending on the lapse of time after death. On the other hand, the lung, brain, and muscle showed little or no change in sulfide concentration with elapse of time after death. The data obtained from human tissues were almost the same as those for rats, except data for blood, in which no or little increase of sulfide was observed.  相似文献   
118.
B. C. Koh 《East Asia》1994,13(2):61-74
North Korea’s foreign policy track record in the post-cold war era is mixed. Most notable setbacks are the diplomatic normalization between the Soviet Union (now Russia) and South Korea; the reversal of its UN policy that paved the way for the simultaneous admission of the two Korean states to the world organization; and the diplomatic normalization between China and South Korea. On the credit side of Pyongyang’s diplomatic ledger are changes in its relations with Tokyo and Washington. While tangible results have yet to materialize, particularly in North Korea-Japan relations, the groundwork has nonetheless been laid for significant improvement. North Korea’s suspected nuclear weapons development program has played a major role in the unfolding of its relations with the United States. Conceptually, North Korean foreign policy can be explained in terms of its quest for three interrelated goals: security, legitimacy, and development. In the post-cold war era security appears to have emerged as the most important of the three goals. North Korea is at a crossroads. The choices it makes in foreign policy will determine not only the direction of its domestic policy but, ultimately, the survival of the regime itself. The external players in Seoul, Washington, Tokyo, Beijing, Moscow, and Vienna (the IAEA) have varying degrees of leverage over Pyongyang’s policy as well.  相似文献   
119.
A 22-year-old Korean soldier, who had received blows to the neck and epigastrium from an officer 10 h earlier, suddenly died after massive hematemesis. He had been in relatively good health except for episodes of blood-tinged vomiting approximately 5 and 7 months prior to this event. Postmortem examination revealed angiodysplasia involving the gastroesophageal junction, and the stomach was distended with blood. No abnormal findings were present around the whole viscera, and the duodenum was free of blood. The pathologic significance of upper gastrointestinal angiodysplasia as a potential source of bleeding and a chronologic correlation between the trauma and bleeding are discussed.  相似文献   
120.
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