全文获取类型
收费全文 | 1187篇 |
免费 | 42篇 |
专业分类
各国政治 | 92篇 |
工人农民 | 136篇 |
世界政治 | 78篇 |
外交国际关系 | 53篇 |
法律 | 582篇 |
中国政治 | 54篇 |
政治理论 | 228篇 |
综合类 | 6篇 |
出版年
2023年 | 7篇 |
2022年 | 5篇 |
2021年 | 11篇 |
2020年 | 33篇 |
2019年 | 41篇 |
2018年 | 49篇 |
2017年 | 49篇 |
2016年 | 49篇 |
2015年 | 26篇 |
2014年 | 38篇 |
2013年 | 184篇 |
2012年 | 36篇 |
2011年 | 37篇 |
2010年 | 25篇 |
2009年 | 41篇 |
2008年 | 41篇 |
2007年 | 26篇 |
2006年 | 26篇 |
2005年 | 24篇 |
2004年 | 30篇 |
2003年 | 27篇 |
2002年 | 31篇 |
2001年 | 10篇 |
2000年 | 19篇 |
1999年 | 22篇 |
1998年 | 14篇 |
1997年 | 10篇 |
1996年 | 18篇 |
1995年 | 19篇 |
1994年 | 20篇 |
1993年 | 20篇 |
1992年 | 13篇 |
1991年 | 15篇 |
1990年 | 15篇 |
1989年 | 12篇 |
1988年 | 14篇 |
1987年 | 13篇 |
1986年 | 15篇 |
1985年 | 18篇 |
1984年 | 15篇 |
1983年 | 16篇 |
1982年 | 19篇 |
1981年 | 10篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1976年 | 12篇 |
1975年 | 9篇 |
1972年 | 5篇 |
1970年 | 4篇 |
1968年 | 5篇 |
排序方式: 共有1229条查询结果,搜索用时 15 毫秒
171.
A solid-phase microextraction-gas chromatographic-mass spectrometric (SPME-GC-MS) method has been developed and validated for measuring four club drugs in human urine. These drugs include gamma-hydroxybutyrate (GHB), ketamine (KET), methamphetamine (MAMP), and methylenedioxymethamphetamine (MDMA). These drugs are referred to as 'club drugs' because of their prevalence at parties and raves. Deuterium labeled internal standards for each of the four drugs was included in the assay to aid in quantitation. The drugs were spiked into human urine and derivatized using pyridine and hexylchloroformate to make them suitable for GC-MS analysis. The SPME conditions of extraction time/temperature and desorption time/temperature were optimized to yield the highest peak area for each of the four drugs. The final SPME parameters included a 90 degrees C extraction for 20min with a 1min desorption in the GC injector at 225 degrees C using a splitless injection. All SPME work was done using a 100microm PDMS fiber by Supelco. The ratio of pyridine to hexylchloroformate for derivatization was also optimized. The GC separation was carried out on a VF-5ht column by Varian (30m, 0.25mm i.d., 0.10microm film thickness) using a temperature program of 150-270 degrees C at 10 degrees C/min. The instrument used was a ThermoFinnigan Trace GC-Polaris Q interfaced with a LEAP CombiPal autosampler. The data was collected by using extracted ion chromatograms of marker m/z values for each drug from the total ion chromatograms (TIC) (full scan mode). Calibration curves with R(2)>0.99 were generated each day using the peak area ratios (peak area drug/peak area internal standard) versus concentration. The validated method resulted in intra-day and inter-day precision (% R.S.D.) of less than 15% and a % error of less than 15% for four concentrations in the range of 0.05-20microg/mL (MAMP) and 0.10-20microg/mL (GHB, KET, and MDMA). This method has the advantage of an easy sample preparation with acceptable accuracy and precision for the simultaneous quantification of these four drugs of abuse and shows no interference from the urine matrix. 相似文献
172.
Trevor L. Brown 《Public administration review》2012,72(5):687-696
This article examines the contract design decisions of three federal agencies—the Departments of Health and Human Services, Defense, and Homeland Security—using five years of data from the Federal Procurement Data System. Three basic contract design elements are charted—type (fixed price versus cost reimbursement), length, and value—across simple to complex products. All three agencies use short‐term, fixed‐price contracts for the majority of the purchases that they make. This basic contract design allows agencies to tap the benefits of competition: innovation and cost‐efficiency. However, the Departments of Defense and Homeland Security often dramatically increase the length and value of contracts through modifications to initial agreements. This approach forgoes the benefits of competition and may expose the agency to the risk of cost overruns, delivery delays, and diminished product quality. 相似文献
173.
Newell AJ Morgan RM Griffin LD Bull PA Marshall JR Graham G 《Journal of forensic sciences》2012,57(5):1285-1289
Quartz sand surface texture analysis has been automated for the first time for forensic application. The derived Basic Image Features (BIFs) provide computer-generated texture recognition from preexisting data sets. The technique was applied to two distinct classification problems; first, the ability of the system to discriminate between (quartz) sand grains with upturned plate features (indicative of eolian, global sand sea environments) and grains that do not exhibit these features. A success rate of grain classification of 98.8% was achieved. Second, to test the ability of the computer recognition system to identify specific energy levels of formation of the upturned plate surface texture features. Such recognition ability has to date been beyond manual geological interpretation. The discrimination performance was enhanced to an exact classification success rate of 81%. The enhanced potential for routine forensic investigation of the provenance of common quartz sand is indicated. 相似文献
174.
Brown LD 《Journal of health politics, policy and law》2012,37(4):587-609
As the challenges of maintaining (or, in the US case, attaining) affordable universal coverage multiply, the debate about what constitutes "real" reform intensifies in Western health care systems. The reality of reform, however, lies in the eyes of myriad beholders who variously enshrine consumer responsibility, changes in payment systems, reorganization, and other strategies -- or some encompassing combination of all of the above -- as the essential ingredient(s). This debate, increasingly informed by the agendas of health services researchers and health policy analysts, arguably serves as much or more to becloud as to clarify the practical options policy makers face and remains severely imbalanced with respect to the institutional sectors on which it concentrates, the fields of knowledge on which it draws, and the roles it envisions for markets and the state. 相似文献
175.
Palmer EJ Hatcher RM McGuire J Bilby CA Hollin CR 《International journal of offender therapy and comparative criminology》2012,56(4):525-538
This study reports an evaluation of the Drink-Impaired Drivers program in the English and Welsh probation service. Participants were adult male offenders who had been convicted of a drink-driving offence and were serving community sentences. The 1-year drink-drive reconviction rates were compared for offenders who completed the program, offenders who started but did not complete the program, and a comparison group who were not allocated to the program. At 1-year follow-up, there was no reconviction among offenders who had completed the program. Multivariate analysis showed that the noncompleters had a significantly higher rate of reconviction than the completers and comparison group. 相似文献
176.
Edelman G Manti V van Ruth SM van Leeuwen T Aalders M 《Forensic science international》2012,220(1-3):239-244
Non-destructive identification and subsequent age estimation of blood stains are significant steps in forensic casework. The latter can provide important information on the temporal aspects of a crime. As previously shown, visible spectroscopy of blood stains on white backgrounds can successfully be used for their identification and age estimation. The use of this technique however, is hampered by dark backgrounds. In the present study the feasibility to use near infrared (NIR) spectroscopy was evaluated for blood stain identification and age estimation on dark backgrounds. Using NIR reflectance spectroscopy, blood stains were distinguished from other substances with 100% sensitivity and 100% specificity. In addition, Partial Least Squares Regression analysis was applied to estimate the age of blood stains on colored backgrounds. The age of blood stains up to 1 month old was estimated successfully with a root mean squared error of prediction of 8.9%. These findings are an important step toward the practical implementation of blood stain identification and age estimation in forensic casework, where a large variety of backgrounds can be encountered. 相似文献
177.
Ruth Breeze 《International Journal for the Semiotics of Law》2012,25(3):393-413
Though still relatively infrequent, the issuing of dissenting and concurring opinions is becoming more common in international investment arbitration. This paper reviews the reasons for delivering separate opinions envisaged in the bibliography on investment arbitration, comparing these with practices in the related area of commercial arbitration. Fourteen recent separate opinions appended to ICSID arbitration awards and decisions are then analysed to determine how the arbitrators themselves explain why they have taken the drastic step of issuing a separate opinion. Potential areas of convergence between investment arbitration and commercial arbitration practice will be addressed. 相似文献
178.
Kerry Brown 《北京周报(英文版)》2014,(36)
正Dear Readers,Forum is a column that provides a space for varying perspectives on contemporary Chinese society.We invite you to submit personal viewpoints on past and current topics(in either English or Chinese).yanwei@bjreview.com Please provide your name and address along with your comments Deng Xiaoping’s role as the father of reform in modern China is historically secure.In his vast biography of the Chinese leader published in 2011,American academic 相似文献
179.
180.
Jessica Skinner PhD Natalie Langley PhD Malin Joseph MS James Herrick MSA Robert Brown BS Brian Waletzki BS Peter Goguen Dipl T Loukham Shyamsunder PhD Subramaniam Rajan PhD 《Journal of forensic sciences》2023,68(3):757-767
Forensic fractographic features of bone reliably establish crack propagation in perimortem injuries. We investigated if similar fracture surface features characterize postmortem fractures. Experimentally induced peri- and postmortem fractures were used to assess if fractographic features vary as bone elasticity decreases during the postmortem interval (PMI). Thirty-seven unembalmed, defleshed human femoral shafts from males and females aged 33–81 years were fractured at varying PMIs with a drop test frame using a three-point bending setup and recorded with a high-speed camera. Vital statistics, cause of death, PMI length, temperature, humidity, collagen percentage, water loss, fracture energy, and fractography scores were recorded for each sample. Results showed that fractographic features associated with perimortem fractures were expressed in PMIs up to 40,600 accumulated degree hours (ADH), or 60 warm weather days. Hackle was the most consistently expressed feature, occurring in all fractures regardless of ADH. The most variable characteristics were wake features (78.4%) and arrest ridges (70.3%). Collagen percentage did not correlate strongly with ADH (r = −0.04, p = 0.81); however, there was a strong significant correlation between ADH and water loss (r = 0.74, p < 0.001). Multinomial logistic regression showed no association between fractographic feature expression and ADH or collagen percentage. In conclusion, forensic fractographic features reliably determine initiation and directionality of crack propagation in experimentally induced PMIs up to 40,600 ADH, demonstrating the utility of this method into the recent postmortem interval. This expression of reliable fractographic features throughout the early PMI intimates these characteristics may not be useful standalone features for discerning peri- versus postmortem fractures. 相似文献