全文获取类型
收费全文 | 8365篇 |
免费 | 392篇 |
国内免费 | 2篇 |
专业分类
8759篇 |
出版年
2023年 | 37篇 |
2022年 | 42篇 |
2021年 | 96篇 |
2020年 | 101篇 |
2019年 | 130篇 |
2018年 | 293篇 |
2017年 | 255篇 |
2016年 | 344篇 |
2015年 | 286篇 |
2014年 | 389篇 |
2013年 | 622篇 |
2012年 | 486篇 |
2011年 | 656篇 |
2010年 | 375篇 |
2009年 | 255篇 |
2008年 | 483篇 |
2007年 | 529篇 |
2006年 | 555篇 |
2005年 | 489篇 |
2004年 | 400篇 |
2003年 | 449篇 |
2002年 | 337篇 |
2001年 | 194篇 |
2000年 | 169篇 |
1999年 | 120篇 |
1998年 | 73篇 |
1997年 | 27篇 |
1996年 | 18篇 |
1995年 | 25篇 |
1994年 | 19篇 |
1993年 | 21篇 |
1992年 | 12篇 |
1991年 | 24篇 |
1990年 | 16篇 |
1989年 | 12篇 |
1987年 | 17篇 |
1986年 | 14篇 |
1985年 | 34篇 |
1984年 | 22篇 |
1983年 | 16篇 |
1982年 | 18篇 |
1981年 | 15篇 |
1979年 | 19篇 |
1978年 | 18篇 |
1977年 | 14篇 |
1974年 | 11篇 |
1953年 | 18篇 |
1952年 | 40篇 |
1888年 | 14篇 |
1887年 | 14篇 |
排序方式: 共有8759条查询结果,搜索用时 15 毫秒
41.
Monika Dybicz Anna Gierczak Julia Dąbrowska Łukasz Rdzanek Bogdan Michałowicz 《Parasitology international》2013,62(4):364-367
The identity of the causative agent of cystic echinococcosis (CE) in humans from central Poland receiving treatment between 2000 and 2010 was determined. A total of 47 samples obtained after hepatectomy were examined and protoscoleces were identified in wet preparations in 27 cases. Using DNA extracted from the samples, two mitochondrial regions (nad1 and cox1 genes) were amplified and the nad1 fragment was sequenced. This PCR analysis confirmed the presence of Echinococcus species in 30 cases and nad1 sequence alignments showed identity with the G7 (pig) strain, Echinococcus canadensis. These data demonstrate that the pig strain of this parasite is the most frequent causative agent of human cystic echinococcosis in central Poland. 相似文献
42.
The structure of a two-dimensional film formed by adsorbed polymer chains was studied by means of Monte Carlo simulations. The polymer chains were represented by linear sequences of lattice beads and positions of these beads were restricted to vertices of a two-dimensional square lattice. Two different Monte Carlo methods were employed to determine the properties of the model system. The first was the random sequential adsorption (RSA) and the second one was based on Monte Carlo simulations with a Verdier-Stockmayer sampling algorithm. The methodology concerning the determination of the percolation thresholds for an infinite chain system was discussed. The influence of the chain length on both thresholds was presented and discussed. It was shown that the RSA method gave considerably lower thresholds for longer chains. This behavior can be explained by a different pool of chain conformations used in the calculations in both methods under consideration. Figure
The percolation cluster (in red) in the system consisting of long flexible chains 相似文献
43.
44.
45.
46.
Olivier Véron Jean-Philippe Blondeau Michał Grabiec Aleksandra Wolak Krzystof Dzierżęga Nadège Ollier François Goutaland Mohamed Chérif Sow Stéphane Pellerin Nadia Pellerin 《Plasmonics (Norwell, Mass.)》2013,8(1):93-103
Silver-exchanged silicate glass has been irradiated by 532-nm pulsed Nd:YAG laser in order to locally form metallic nanoparticles. The particular interest of this process is to locally control the silver nanoparticles (NPs) growth. Silver ions are exchanged with sodium ions near the glass surface after dumping of a silicate glass few minutes in silver and sodium nitrates molten salt. A low-energy density laser exposure (0.239 J/cm2) chosen at the ablation threshold allows to observe the kinetics of the silver NPs growth according to the increasing shots number. An on-line optical measurement is carried out after each shot to identify the most important steps during the irradiation process. According to this measurement, we have determined four steps highlighted by UV/Visible spectrophotometry and we have identified the influence of located surface plasmon resonance. Three combined material analysis methods were used to understand the glass/laser interaction mechanism: we outlined the material volume variations by profilometric method, the element distribution by scanning electron microscopy and finally the structural distribution of the irradiated region by a local infrared investigation. The trend for NPs formation revealed by the UV/Visible spectrophotometry is thus explained by the formation of a ring expelled from a central hole. We highlight that the on-line extinction measurement can be used to data process the NPs evolution. 相似文献
47.
Helena Popławska Adam Wilczewski Agnieszka Dmitruk Wojciech Hołub 《Economics & Human Biology》2013,11(2):221-226
The aim of this study was to determine secular changes in the sexual maturation of children and adolescents from Eastern regions of Poland between 1980 and 2000, with special attention paid to rural–urban differences. Our sample comprised 34,055 girls and 28,100 boys from 9 to 18 years of age. The age at which each gender reached each stage of sexual maturation was examined, along with menarcheal age in girls. An increase in the rate of sexual maturation was observed over the 20-year period of this study. Menarcheal age in girls decreased by 0.59 years. The length of sexual maturation decreased: from 6.58 years to 3.85 years in girls and from 5.84 years to 3.65 years in boys. A significantly faster rate of sexual maturation was observed between 1990 and 2000. Over the entire 20-year period, adolescents living in rural settings experienced a slower rate of sexual maturation than did their urban peers. 相似文献
48.
Mansouri Borhan Błaszczyk Martyna Binkowski Lukasz J. Sayadi Mohammad Hossein Azadi Nammam Ali Amirabadizadeh Ali Reza Mehrpour Omid 《Biological trace element research》2020,195(1):63-70
Biological Trace Element Research - In low-income and middle-income countries such as Iran, smoking is becoming increasingly popular, especially among young people. This has led to additional... 相似文献
49.
Aleksandra Łukasiewicz Małgorzata Niśkiewicz Jacek Radwan 《Evolution; international journal of organic evolution》2020,74(8):1851-1855
Elaborate sexually selected ornaments and armaments are costly but increase the reproductive success of their bearers (usually males). It has been postulated that high-quality males can invest disproportionately more in such traits, making those traits honest signals of genetic quality. However, genes associated with such traits may have sexually antagonistic effects on fitness. Here, using a bulb mite Rhizoglyphus robini, a species in which a distinct dimorphism exists between males in the expression of a sexually selected weapon, we compare inbreeding and gender load between lines derived from armed fighters and unarmed scramblers. After four generations of sib-mating, inbreeding depression for female fitness was significantly lower in fighter-derived lines compared to scrambler-derived lines, suggesting that fighter males had significantly higher genetic quality. However, outbred females from fighter-derived lines had significantly lower fitness compared to outbred females from scrambler-derived lines, demonstrating significant gender load associated with the presence of a sexually selected male weapon. Our results imply that under outbreeding, genetic benefits of mating with bearers of elaborate sexually selected traits might be swamped by the costs of decreased fitness of female progeny due to sexually antagonistic effects. 相似文献
50.
Helena Rudnicka Tadeusz Debniak Cezary Cybulski Tomasz Huzarski Jacek Gronwald Jan Lubinski Bohdan Gorski 《Molecular biology reports》2013,40(12):6619-6623
BRCA1 and BRCA2 are two major genes associated with familial breast and ovarian cancer susceptibility. In Poland standard BRCA gene test is usually limited to Polish founder BRCA1 mutations: 5382insC, C61G and 4153delA. To date, just a few single large genomic rearrangements (LGRs) of BRCA1 gene have been reported in Poland. Here we report the first comprehensive analysis of large mutations in BRCA1 and BRCA2 genes in this country. We screened LGRs in BRCA1 and BRCA2 genes by multiplex ligation-dependent probe amplification in 200 unrelated patients with strong family history of breast/ovarian cancers and negative for BRCA1 Polish founder mutations. We identified three different LGRs in BRCA1 gene: exons 13-19 deletion, exon 17 deletion and exon 22 deletion. No LGR was detected in BRCA2 genes. Overall, large rearrangements accounted for 3.7 % of all BRCA1 mutation positive families in our population and 1.5 % in high-risk families negative for Polish founder mutation. 相似文献