全文获取类型
收费全文 | 104946篇 |
免费 | 1152篇 |
国内免费 | 820篇 |
出版年
2021年 | 123篇 |
2020年 | 94篇 |
2019年 | 125篇 |
2018年 | 11953篇 |
2017年 | 10789篇 |
2016年 | 7640篇 |
2015年 | 945篇 |
2014年 | 638篇 |
2013年 | 835篇 |
2012年 | 4863篇 |
2011年 | 13349篇 |
2010年 | 12395篇 |
2009年 | 8569篇 |
2008年 | 10265篇 |
2007年 | 11851篇 |
2006年 | 792篇 |
2005年 | 1044篇 |
2004年 | 1493篇 |
2003年 | 1558篇 |
2002年 | 1305篇 |
2001年 | 386篇 |
2000年 | 256篇 |
1999年 | 161篇 |
1998年 | 177篇 |
1997年 | 175篇 |
1996年 | 154篇 |
1995年 | 156篇 |
1994年 | 133篇 |
1993年 | 190篇 |
1992年 | 133篇 |
1991年 | 175篇 |
1990年 | 130篇 |
1989年 | 111篇 |
1988年 | 139篇 |
1987年 | 119篇 |
1986年 | 91篇 |
1985年 | 111篇 |
1984年 | 175篇 |
1983年 | 158篇 |
1982年 | 142篇 |
1981年 | 151篇 |
1980年 | 126篇 |
1979年 | 109篇 |
1978年 | 131篇 |
1977年 | 101篇 |
1976年 | 87篇 |
1975年 | 99篇 |
1974年 | 80篇 |
1972年 | 297篇 |
1971年 | 314篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Jiang Gui Jason H. Moore Scott M. Williams Peter Andrews Hans L. Hillege Pim van der Harst Gerjan Navis Wiek H. Van Gilst Folkert W. Asselbergs Diane Gilbert-Diamond 《PloS one》2013,8(6)
We present an extension of the two-class multifactor dimensionality reduction (MDR) algorithm that enables detection and characterization of epistatic SNP-SNP interactions in the context of a quantitative trait. The proposed Quantitative MDR (QMDR) method handles continuous data by modifying MDR’s constructive induction algorithm to use a T-test. QMDR replaces the balanced accuracy metric with a T-test statistic as the score to determine the best interaction model. We used a simulation to identify the empirical distribution of QMDR’s testing score. We then applied QMDR to genetic data from the ongoing prospective Prevention of Renal and Vascular End-Stage Disease (PREVEND) study. 相似文献
992.
Michael Edlinger Nicole Concin Hans Concin Gabriele Nagel Hanno Ulmer Georg Göbel 《Cancer epidemiology》2013,37(2):156-161
Background: Lifestyle seems to play an important role in endometrial cancer mortality, but it remains unclear which biomarkers are involved. The aim of this study was to assess the extent of the association between lifestyle-related biomarkers and the survival of endometrial cancer patients. Methods: A sub-cohort of 242 endometrial cancer patients, from a population-based study of the more than 90,000 female participants of the Vorarlberg Health Monitoring and Promotion Programme, was followed for a median duration of twelve years. Besides age, tumour staging, and histology, also pre-diagnostic levels of body mass index, blood pressure, triglycerides, total cholesterol, glucose, gamma-glutamyltransferase (GGT), and serum uric acid were analysed in Cox proportional hazards regression models to estimate multivariate mortality risks. Results: During follow-up 89 deaths occurred of which 49 were cancer-related. Survival was associated with age, tumour stage, and histology. Of the biomarkers, log10-transformed GGT showed a large effect on cancer-related mortality (HR = 3.35, 95% CI 1.12–10.03), whereas the other parameters did not appear with significant effects after adjustment for the other factors. Conclusion: Elevated level of GGT, a lifestyle-related marker, was associated with poor survival among endometrial cancer patients. 相似文献
993.
Alcohol consumption and alcohol problems after bariatric surgery in the swedish obese subjects study
994.
995.
996.
Teresa Fiebig Giovanna Figueiredo Hanne Boll Hans Ulrich Kerl Ingo S. Noelte Alex Forster Christoph Groden Martin Kramer Marc A. Brockmann 《PloS one》2013,8(6)
Purpose
Small injection ports for mice are increasingly used for drug testing or when administering contrast agents. Commercially available mini-ports are expensive single-use items that cause imaging-artifacts. We developed and tested an artifact-free, low-cost, vascular access mini-port (VAMP) for mice.Procedures
Leakage testing of the VAMP was conducted with high speed bolus injections of different contrast agents. VAMP-induced artifacts were assessed using a micro-CT and a small animal MRI (9.4T) scanner ex vivo. Repeated contrast administration was performed in vivo.Results
With the VAMP there was no evidence of leakage with repeated punctures, high speed bolus contrast injections, and drawing of blood samples. In contrast to the tested commercially available ports, the VAMP did not cause artifacts with MRI or CT imaging.Conclusions
The VAMP is an alternative to commercially available mini-ports and has useful applications in animal research involving imaging procedures and contrast agent testing. 相似文献997.
Luomeng Chao Lihong Bao Wei Wei O. Tegus Zhidong Zhang 《Plasmonics (Norwell, Mass.)》2016,11(3):697-701
The optical response of lanthanum hexaboride (LaB6) nanoparticles has been investigated by both theoretically and experimentally. The LaB6 nanoparticles obtained by solid-state reaction could avoid serious surface oxidization and exhibit excellent optical performance. The discrete dipole approximation (DDA) has been used to investigate the optical response of LaB6 nanoparticles with different sizes and different shapes. The calculation results coincide with the experimental results and reveal that the largest extinction peak value appears at 60 nm for cubic particles and 40 nm for spherical particles, respectively. Our calculation results show that the existence of the largest extinction peak value is not only due to the surface oxides but also relate to the particle shape of LaB6 compound. In addition, the LaB6 nanoparticles with cubic and spherical shapes exhibit different optical responses, and the cubic particles exhibit stronger near infrared (NIR) extinction than spherical particles. With increasing particle size, the extinction peak value of spherical particle decreases more rapidly than that of cubic ones. 相似文献
998.
Lisheng Zhang Feng Zhao Zhipeng Li Yan Fang Peijie Wang 《Plasmonics (Norwell, Mass.)》2016,11(6):1511-1517
We report the synthesis and the characterization of core-shell Au@Ag nanorods through reduction by the wet chemical method. UV-visible absorption spectra of core-shell Au@Ag nanorods demonstrate the longitudinal mode of localized surface plasmon resonances (LSPRs) can be tailored from 724 to 786 nm by controlling the thickness of the silver shell, as is assessed by transmission electron microscope (TEM). Furthermore, the tunable and well-controlled LSPRs of core-shell Au@Ag nanorods are also investigated by numerical simulation using the finite difference time domain (FDTD) method, which strongly supports the experimental observations. The growth mechanism for core-shell Au@Ag nanorods is proposed, according to experimental observations and numerical calculations. 相似文献
999.
Jian-Ping Liu Xiang Zhai Ling-Ling Wang Hong-Ju Li Fang Xie Qi Lin Sheng-Xuan Xia 《Plasmonics (Norwell, Mass.)》2016,11(3):703-711
A graphene-based cylindrical hybrid surface plasmon polariton waveguide, composed of a silicon nanowire core surrounded by a silica layer and then a graphene layer, is investigated using the finite-difference time-domain method. The analytical solutions and the numerical simulation show that an ultra-small mode area and a large propagation length can be achieved with this waveguide. Utilizing the perturbation theory of coupled mode, we demonstrate that the six lowest-order coupling modes originate from the coupling of the three lowest-order single-waveguide modes, and the m?=?1 order yy-coupling mode possesses the maximum coupling length and the minimum crosstalk. This waveguide can be used for photonic integrated circuits in the mid-infrared range. 相似文献
1000.
We introduce a Y-shaped gap into a silver disk to break the structure symmetry which can be looked as a loop-linked structure. Magnetic resonances are excited by incident light when incident electric field is parallel to the trimer plane. Fano resonance is generated by the coupling between bright electric mode and dark magnetic mode. These resonances can be adjusted by tuning the gap size, the radius of trimer, and the position of Y-shaped gap. The extinction cross section of the structure is calculated with the finite element method (FEM). The maximum figure of merit (FOM) is 37.8. Both the magnetic and electric field are greatly enhanced at the Fano dip and the magnetic resonance peak. 相似文献