全文获取类型
收费全文 | 15876篇 |
免费 | 222篇 |
专业分类
各国政治 | 470篇 |
工人农民 | 1405篇 |
世界政治 | 679篇 |
外交国际关系 | 538篇 |
法律 | 9761篇 |
中国政治 | 60篇 |
政治理论 | 3145篇 |
综合类 | 40篇 |
出版年
2020年 | 98篇 |
2019年 | 129篇 |
2018年 | 1407篇 |
2017年 | 1354篇 |
2016年 | 1177篇 |
2015年 | 182篇 |
2014年 | 188篇 |
2013年 | 762篇 |
2012年 | 358篇 |
2011年 | 1093篇 |
2010年 | 1152篇 |
2009年 | 746篇 |
2008年 | 938篇 |
2007年 | 911篇 |
2006年 | 248篇 |
2005年 | 251篇 |
2004年 | 378篇 |
2003年 | 359篇 |
2002年 | 211篇 |
2001年 | 329篇 |
2000年 | 311篇 |
1999年 | 234篇 |
1998年 | 104篇 |
1997年 | 93篇 |
1996年 | 109篇 |
1995年 | 106篇 |
1994年 | 101篇 |
1993年 | 67篇 |
1992年 | 155篇 |
1991年 | 167篇 |
1990年 | 145篇 |
1989年 | 167篇 |
1988年 | 142篇 |
1987年 | 155篇 |
1986年 | 142篇 |
1985年 | 161篇 |
1984年 | 136篇 |
1983年 | 153篇 |
1982年 | 106篇 |
1981年 | 98篇 |
1980年 | 79篇 |
1979年 | 109篇 |
1978年 | 86篇 |
1977年 | 80篇 |
1976年 | 59篇 |
1975年 | 47篇 |
1974年 | 58篇 |
1973年 | 61篇 |
1971年 | 50篇 |
1970年 | 47篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
911.
Salas A Prieto L Montesino M Albarrán C Arroyo E Paredes-Herrera MR Di Lonardo AM Doutremepuich C Fernández-Fernández I de la Vega AG Alves C López CM López-Soto M Lorente JA Picornell A Espinheira RM Hernández A Palacio AM Espinoza M Yunis JJ Pérez-Lezaun A Pestano JJ Carril JC Corach D Vide MC Alvarez-Iglesias V Pinheiro MF Whittle MR Brehm A Gómez J 《Forensic science international》2005,150(2-3):191-198
A qualitative and quantitative analytical method was developed and validated for the determination of 49 licit and illicit drugs in oral fluid. Small oral fluid samples, volume 1mL, were collected from volunteers using a modified Omni-Sal device and the analytes were extracted from an oral fluid/buffer mixture using a single Bond Elut Certify solid phase extraction cartridge. Liquid chromatography-tandem mass spectrometry (LC-MS-MS) and gas chromatography-repetitive full scan mass spectrometry (GC-MS) were used in parallel to analyze the extracts for the targeted drugs. Extracts were analyzed by GC-MS in their underivatized form and as their pentafluoropropionyl derivatives. Deuterated internal standards were used for quantification of drugs of abuse by LC-MS-MS to minimize matrix effects. Methadone-d(9) and tumoxetine were used as the internal standards for quantification of non-derivatized and derivatized analytes respectively by GC-MS. Linearity was demonstrated over the range 5-200 ng/mL and limits of detection were less than 4 ng/mL for each drug analyzed. The method demonstrated acceptable recoveries for most of the analytes and good intra- and inter-day precision. Acquisition of data by repetitive full scan GC-MS allows the addition of further analytes to the target menu. 相似文献
912.
We present a review of a population of 114 immigrant Moroccan males for which an age estimation was requested. The subjects' real chronological age was confirmed by the Moroccan Embassy in Spain. The confirmed age range was between 13 and 25, with an average age of 18.1 years and a standard deviation of 2.03. The following tests were performed to arrive at the forensic estimation of age: general physical examination, carpus X-ray (Greulich and Pyle method) and dental orthopantomography to determine the degree of maturity of the third inferior molars (Demirjian's method). Carpus X-ray (skeletal age) was the most useful method, followed by Demirjian's method (dental age), as prediction factors of a chronological age of over or under 18. The combination of skeletal and dental age variables represented a significant improvement in the prediction of the chronological age of the subjects in this population, reducing the number of ethically unacceptable test errors to a minimum. 相似文献
913.
Validation of a 21-locus autosomal SNP multiplex for forensic identification purposes 总被引:8,自引:0,他引:8
Dixon LA Murray CM Archer EJ Dobbins AE Koumi P Gill P 《Forensic science international》2005,154(1):62-77
A single nucleotide polymorphism (SNP) multiplex has been developed to analyse highly degraded and low copy number (LCN) DNA template, i.e. <100 pg, for scenarios including mass disaster identification. The multiplex consists of 20 autosomal non-coding loci plus Amelogenin for sex determination, amplified in a single tube PCR reaction and visualised on the Applied Biosystems 3100 capillary electrophoresis (CE) system. Allele-specific primers tailed with shared universal tag sequences were designed to speed multiplex design and balance the amplification efficiencies of all loci through the use of a single reverse and two differentially labelled allele denoting forward universal primers. As the multiplex is intended for use with samples too degraded for conventional profiling, a computer program was specifically developed to aid interpretation. Critical factors taken into account by the software include empirically determined extremes of heterozygous imbalance (Hb) and the drop-out threshold (Ht) defined as the maximum peak height of a surviving heterozygous allele, where its partner may have dropped out. The discrimination power of the system is estimated at 1 in 4.5 million, using a White Caucasian population database. Comparisons using artificially degraded samples profiled with both the SNP multiplex and AMPFISTR SGM plus (Applied Biosystems) demonstrated a greater likelihood of obtaining a profile using SNPs for certain sample types. Saliva stains degraded for 147 days generated an 81% complete SNP profile whilst short tandem repeats (STRs) were only 18% complete; similarly blood degraded for 243 days produced full SNP profiles but only 9% with STRs. Reproducibility studies showed concordance between SNP profiles for different sample types, such as blood, saliva, semen and hairs, for the same individual, both within and between different DNA extracts. 相似文献
914.
The recent House of Lords decision in Quintavalle v Human Fertilisation and Embryology Authority has raised difficult and complex issues regarding the extent to which embryo selection and reproductive technology can be used as a means of rectifying genetic disorders and treating critically ill children. This comment outlines the facts of Quintavalle and explores how the House of Lords approached the legal, ethical and policy issues that arose out of the Human Fertilisation and Embryology Authority's (UK) decision to allow reproductive and embryo technology to be used to produce a 'saviour sibling' whose tissue could be used to save the life of a critically ill child. Particular attention will be given to the implications of the decision in Quintavalle for Australian family and medical law and policy. As part of this focus, the comment explores the current Australian legislative and policy framework regarding the use of genetic and reproductive technology as a mechanism through which to assist critically ill siblings. It is argued that the present Australian framework would appear to impose significant limits on the medical uses of genetic technology and, in this context, would seem to reflect many of the principles that were articulated by the House of Lords in Quintavalle. 相似文献
915.
916.
917.
918.
919.
Contrary to a widespread belief about the undesirability of relatively large prisons, a review of the criminological literature yields no empirical evidence that prison size influences behavior inside or after leaving prison. The English prison statistics show that prison offenses, and more specifically assaults, are less likely in larger prisons. However, it was impossible in these analyses to control for the kinds of inmates in each prison. In a more controlled analysis of correctional effectiveness (defined as the difference between predicted and actual reconviction rates), there was a strong tendency for the more overcrowded prisons to be less effective. Size was only weakly related to effectiveness, and this association was reduced further after controlling for overcrowding. It was concluded that an important priority for governmental agencies should be to reduce overcrowding in prisons. 相似文献
920.
An investigation of the following psychoactive drugs: barbiturate, benzodiazepine, meprobamate, methaqualone and phenothiazine, was performed on all automobile occupants killed in accidents in southern Sweden during 1977 and 1978. Of 122 drivers and 55 passengers analysed, low concentrations of these drugs were found in nine drivers and in five passengers. Thus, 7.3% of the drivers were driving under the influence of drugs and, of these, two drivers (1.6% of all analysed drivers) were also inebriated. Twenty-three per cent of the drivers were inebriated only. According to the circumstances in the accidents and the number of drivers whose analyses proved positive, drug influence seldom seems to be the cause of fatal traffic accidents. 相似文献