全文获取类型
收费全文 | 15276篇 |
免费 | 478篇 |
专业分类
各国政治 | 670篇 |
工人农民 | 624篇 |
世界政治 | 960篇 |
外交国际关系 | 472篇 |
法律 | 9895篇 |
中国共产党 | 3篇 |
中国政治 | 101篇 |
政治理论 | 2919篇 |
综合类 | 110篇 |
出版年
2020年 | 193篇 |
2019年 | 245篇 |
2018年 | 329篇 |
2017年 | 368篇 |
2016年 | 363篇 |
2015年 | 252篇 |
2014年 | 302篇 |
2013年 | 1562篇 |
2012年 | 375篇 |
2011年 | 397篇 |
2010年 | 338篇 |
2009年 | 352篇 |
2008年 | 417篇 |
2007年 | 416篇 |
2006年 | 457篇 |
2005年 | 385篇 |
2004年 | 393篇 |
2003年 | 385篇 |
2002年 | 360篇 |
2001年 | 535篇 |
2000年 | 517篇 |
1999年 | 388篇 |
1998年 | 197篇 |
1997年 | 188篇 |
1996年 | 181篇 |
1995年 | 162篇 |
1994年 | 169篇 |
1993年 | 168篇 |
1992年 | 314篇 |
1991年 | 330篇 |
1990年 | 299篇 |
1989年 | 316篇 |
1988年 | 282篇 |
1987年 | 315篇 |
1986年 | 297篇 |
1985年 | 299篇 |
1984年 | 267篇 |
1983年 | 292篇 |
1982年 | 186篇 |
1981年 | 181篇 |
1980年 | 143篇 |
1979年 | 195篇 |
1978年 | 146篇 |
1977年 | 130篇 |
1976年 | 114篇 |
1975年 | 100篇 |
1974年 | 117篇 |
1973年 | 127篇 |
1972年 | 102篇 |
1970年 | 90篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
901.
Wulf J Bednarz J Junge M Engelmann K Püschel K 《Forensic science international》2000,113(1-3):495-496
Between 1997 and 1999 a steady increase in cornea donations was achieved, but the number of transplantations remained stable because many grafts did not pass quality control. Intermediate organ culture of entire bulbi was examined as a possible solution to reduce post-mortem times and increase suitability for transplantation. 相似文献
902.
3,4-methylenedioxyamphetamine (MDA) derivatives are increasingly abused central nervous system stimulants with neurotoxic properties. In recent years a number of controlled substance analogs (designer drugs) with high structural variety reached the illegal market making their identification an arduous task. The underivatized compounds give very similar or even virtually identical electron impact mass spectra containing mainly intense C(n)H(2n+2)N(+) immonium ions. Using tandem mass spectrometry (MS-MS) the additional structural information contained in the collision induced dissoziation (CID) mass spectra of molecular ions using electron impact (EI) and especially chemical ionization (CI) allowed an unequivocal differentiation of 18 studied regioisomeric 1-(methylenedioxyphenyl)-2-propanamines and 1-(methylenedioxyphenyl)-2-butanamines.Further synthetic methods are presented for 1-(3,4-methylenedioxyphenyl)-N-propyl-2-butanamine, N-isopropyl-1-(3,4-methylenedioxyphenyl)-2-butanamine and four 1-(2, 3-methylenedioxyphenyl)-2-butanamines. N-alkylated 1-(3, 4-methylenedioxyphenyl)-2-butanamine compounds (e.g. MBDB) are also known to be abused psychoactive agents (entactogenes) without the sympatomimetic effects of the 3,4-methylenedioxyamphetamines. 相似文献
903.
This paper describes a collaborative exercise organised under the auspices of the European Network of Forensic Science Institutes (ENFSI). The purpose of this EU (European Union) funded group is to carry out research to enable STR loci to be compared between European laboratories, ultimately leading to the formation of a pan-European database. Accordingly, an exercise was designed to evaluate a prototype STR multiplex system manufactured by Applied Biosystems (ABD). Each laboratory was sent 12 samples to analyse along with a multiplex kit. Of specific interest was the definition of parameters to define the efficiency of the system. Stutter, split allelic peaks (differing by one base), pull-up, heterozygous balance and between locus balance were all objectively measured. Once the important parameters are defined it is possible to directly compare performances of different multiplexes and the different laboratories carrying out the tests. Since the multiplex used was a prototype system, this exercise cannot be regarded as a proficiency test. 相似文献
904.
905.
906.
907.
908.
909.
910.
Smith GP 《Medical law international》2000,4(2):85-95
So long as procreation continues to remain a central driving force in a marital relationship, and the family the very core of progressive society, efforts will be undertaken to expand the period of fecundity and combat infertility. Genetic planning and eugenic programming are more rational and humane alternatives to population regulation than death by famine and war. Genetic enhancement technologies and the scientific research undertaken to advance them should be viewed as not only aiding (or, sometimes resolving) the tragedy of infertility in family planning, but as a tool for enhancing the health of a Nation's citizens by engineering man's genetic weaknesses out of the line of inheritance. Put simply, healthier and genetically sound individuals have a much better opportunity for pursuing and achieving the "good life" and making a significant contribution to society's greater well being. 相似文献