全文获取类型
收费全文 | 10726篇 |
免费 | 711篇 |
国内免费 | 1篇 |
出版年
2023年 | 38篇 |
2022年 | 76篇 |
2021年 | 159篇 |
2020年 | 107篇 |
2019年 | 127篇 |
2018年 | 189篇 |
2017年 | 156篇 |
2016年 | 269篇 |
2015年 | 397篇 |
2014年 | 487篇 |
2013年 | 740篇 |
2012年 | 806篇 |
2011年 | 750篇 |
2010年 | 471篇 |
2009年 | 404篇 |
2008年 | 618篇 |
2007年 | 613篇 |
2006年 | 576篇 |
2005年 | 498篇 |
2004年 | 504篇 |
2003年 | 501篇 |
2002年 | 471篇 |
2001年 | 184篇 |
2000年 | 191篇 |
1999年 | 166篇 |
1998年 | 124篇 |
1997年 | 124篇 |
1996年 | 102篇 |
1995年 | 85篇 |
1994年 | 102篇 |
1993年 | 84篇 |
1992年 | 127篇 |
1991年 | 103篇 |
1990年 | 91篇 |
1989年 | 79篇 |
1988年 | 67篇 |
1987年 | 68篇 |
1986年 | 58篇 |
1985年 | 57篇 |
1984年 | 65篇 |
1983年 | 76篇 |
1982年 | 42篇 |
1981年 | 51篇 |
1980年 | 33篇 |
1979年 | 49篇 |
1978年 | 27篇 |
1977年 | 31篇 |
1975年 | 33篇 |
1974年 | 31篇 |
1973年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Gian Maria Rossolini Patrizia Muscas Alessandra Chiesurin Giuseppe Satta 《FEMS microbiology letters》1994,119(3):321-328
Abstract Analysis of the Salmonella chromosomal region located upstream of the fimA gene (coding for the major type 1 fimbrial subunit) showed a close linkage of this gene to the folD gene (coding for the enzyme 5,10-methylenetetrahydrofolate dehydrogenase/5, 10-methenyltetrahydrofolate cyclohydrolase), indicating that the fim gene cluster of Salmonella , unlike that of Escherichia coli , has no regulatory genes located upstream of fimA and apparently terminates with this gene. The respective locations of the fim and folD genes in the E. coli and Salmonella genetic maps suggests that the fimA-folD intergenic region of Salmonella encompasses a junctional site of a genetic rearrangement that probably originated from the different chromosomal location of the fim genes in these species. 相似文献
2.
3.
4.
5.
The aim of this study was to identify plant species among the diverse flora of the caatinga ecosystem that are used therapeutically. Research was undertaken in the municipalities of Piranhas and Delmiro Gouveia, in the Xingó region (state of Alagoas, NE Brazil). In order to identify the medicinal plants used in this region, semi-structured questionnaires were applied. The species cited were collected and sent to the Xingó Herbarium for taxonomic analysis. The relative importance (RI) of each species cited was calculated to verify their cultural importance. The therapeutic indications attributed to the species were classified under 16 body systems. A total of 187 medicinal species were cited, from 64 families and 128 genera. The main indications for medicinal plant use were against common colds, bronchitis, cardiovascular problems, kidney problems, inflammations in general, and as tranquilizers. Approximately 16% (30 plant species) were versatile in relation to their use, with an Relative Importance value over 1, having been indicated for up to nine body systems. The body systems that stood out the most were: the respiratory system, the gastrointestinal system, and infectious diseases. Most cited plant parts used for medicinal purposes were flowers, leaves, and inner stem bark. 相似文献
6.
Lorenzo Dal Bo Paolo Mazzucchelli Antonio Marzo 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2000,749(2):258
Zofenopril is a pro-drug designed to undergo metabolic hydrolysis yielding the active free sulfhydryl compound zofenoprilat, which is an angiotensin converting enzyme (ACE) inhibitor, endowed also with a marked cardioprotective activity. A simple, highly sensitive specific LC–MS–MS method was developed for the determination of zofenopril and zofenoprilat in human plasma. In order to prevent oxidative degradation of zofenoprilat and its internal standard, their free sulfhydryl groups were protected by treatment with N-ethylmaleimide (NEM), which produced the succinimide derivatives. The compounds and their corresponding fluorine derivatives, used as internal standards, were extracted from plasma with toluene. The reconstituted dried extracts were chromatographed and then monitored by a triple-stage-quadrupole instrument operating in the negative ion spray ionization mode. The method was validated over the concentration range of 1–300 ng/ml for zofenopril and 2–600 ng/ml for zofenoprilat. Inter- and intra-assay precision and accuracy of both zofenopril and zofenoprilat were better than 10%. The limit of quantitation was 1 ng/ml with zofenopril and 2 ng/ml with zofenoprilat. Extraction recovery proved to be on average 84.8% with zofenopril and 70.1% with zofenoprilat. Similar recoveries were shown by the above two internal standards. The method was applied to measure plasma concentrations of zofenopril and zofenoprilat in 18 healthy volunteers treated orally with zofenopril calcium salt at the dose of 60 mg. 相似文献
7.
Sergio Davinelli Mariano Intrieri Claudio Russo Alfonso Di Costanzo Davide Zella Paolo Bosco Giovanni Scapagnini 《Immunity & ageing : I & A》2011,8(1):1-10
Alzheimer's disease is a progressive and neurodegenerative disorder which involves multiple molecular mechanisms. Intense research during the last years has accumulated a large body of data and the search for sensitive and specific biomarkers has undergone a rapid evolution. However, the diagnosis remains problematic and the current tests do not accurately detect the process leading to neurodegeneration. Biomarkers discovery and validation are considered the key aspects to support clinical diagnosis and provide discriminatory power between different stages of the disorder. A considerable challenge is to integrate different types of data from new potent approach to reach a common interpretation and replicate the findings across studies and populations. Furthermore, long-term clinical follow-up and combined analysis of several biomarkers are among the most promising perspectives to diagnose and manage the disease. The present review will focus on the recent published data providing an updated overview of the main achievements in the genetic and biochemical research of the Alzheimer's disease. We also discuss the latest and most significant results that will help to define a specific disease signature whose validity might be clinically relevant for future AD diagnosis. 相似文献
8.
Adriana Calderaro Giovanna Piccolo Chiara Gorrini Sara Montecchini Sabina Rossi Maria Cristina Medici Carlo Chezzi Georges Snounou 《PloS one》2012,7(10)
It has been proposed that ovale malaria in humans is caused by two closely related but distinct species of malaria parasites: P. ovale curtisi and P. ovale wallikeri. We have extended and optimized a Real-time PCR assay targeting the parasite’s small subunit ribosomal RNA (ssrRNA) gene to detect both these species. When the assay was applied to 31 archival blood samples from patients diagnosed with P. ovale, it was found that the infection in 20 was due to P. ovale curtisi and in the remaining 11 to P. ovale wallikeri. Thus, this assay provides a useful tool that can be applied to epidemiological investigations of the two newly recognized distinct P. ovale species, that might reveal if these species also differ in their clinical manifestation, drugs susceptibility and relapse periodicity. The results presented confirm that P. ovale wallikeri is not confined to Southeast Asia, since the majority of the patients analyzed in this study had acquired their P. ovale infection in African countries, mostly situated in West Africa. 相似文献
9.
10.