全文获取类型
收费全文 | 9329篇 |
免费 | 367篇 |
国内免费 | 61篇 |
专业分类
化学 | 6389篇 |
晶体学 | 93篇 |
力学 | 279篇 |
数学 | 808篇 |
物理学 | 2188篇 |
出版年
2023年 | 54篇 |
2022年 | 190篇 |
2021年 | 226篇 |
2020年 | 178篇 |
2019年 | 172篇 |
2018年 | 172篇 |
2017年 | 144篇 |
2016年 | 296篇 |
2015年 | 269篇 |
2014年 | 353篇 |
2013年 | 596篇 |
2012年 | 742篇 |
2011年 | 823篇 |
2010年 | 469篇 |
2009年 | 385篇 |
2008年 | 616篇 |
2007年 | 580篇 |
2006年 | 512篇 |
2005年 | 473篇 |
2004年 | 408篇 |
2003年 | 325篇 |
2002年 | 326篇 |
2001年 | 216篇 |
2000年 | 177篇 |
1999年 | 129篇 |
1998年 | 69篇 |
1997年 | 79篇 |
1996年 | 95篇 |
1995年 | 80篇 |
1994年 | 75篇 |
1993年 | 57篇 |
1992年 | 60篇 |
1991年 | 47篇 |
1990年 | 51篇 |
1989年 | 34篇 |
1988年 | 26篇 |
1987年 | 12篇 |
1986年 | 10篇 |
1985年 | 26篇 |
1984年 | 18篇 |
1983年 | 17篇 |
1982年 | 18篇 |
1981年 | 16篇 |
1980年 | 12篇 |
1979年 | 13篇 |
1978年 | 16篇 |
1977年 | 10篇 |
1976年 | 13篇 |
1975年 | 10篇 |
1972年 | 9篇 |
排序方式: 共有9757条查询结果,搜索用时 15 毫秒
171.
172.
Yang Shin Park Chang Hee Lee Baek Hui Kim Jongmee Lee Jae Woong Choi Kyeong Ah Kim Jeong Hwan Ahn Cheol Min Park 《Magnetic resonance imaging》2013
Purpose
The purpose of the study was to determine significant imaging features to differentiate between infiltrative hepatocellular carcinoma (HCC) and confluent fibrosis (CF) in liver cirrhosis using Gd-EOB-DTPA-enhanced 3-T magnetic resonance imaging.Material and methods
Nineteen infiltrative HCCs and eight CFs were included. We evaluated the difference in imaging findings and apparent diffusion coefficient (ADC) between the two entities. We compared T2-weighted image (WI) and hepatobiliary phase (HBP) in terms of the clarity of the lesion outer margin.Results
Seventeen infiltrative HCCs showed lobulated margin, while focal CFs showed either straight (n = 3) or irregular margins (n = 5) (P = .001). All infiltrative HCCs had intact or bulging contours, and all focal CFs showed capsular retraction (P = .001). Fourteen infiltrative HCCs and two focal CFs showed arterial enhancement (P = .035). The ADC of infiltrative HCCs was significantly lower than that of CFs (P = .001). Satellite nodules were noted in 10 infiltrative HCCs. In terms of outer margin clarity, infiltrative HCCs showed a more distinct margin on HBP than on T2-WI (P = .005), while these two sequences were not significantly different in focal CFs (P = 1.000).Conclusion
HBP improved the imaging characteristics of infiltrative HCC, allowing it to be distinguished from focal CF. Infiltrative HCC showed lower ADC values than focal CF. Lobular configuration, contour bulging, enhancement pattern, associated satellite nodules and portal vein thrombosis were still found to be highly suggestive MR findings for infiltrative HCC. 相似文献173.
Chul‐Kyu Lee Se Yeob Park Hong Yoon Jung Chang‐Kyu Lee Byeong‐Geun Son Hyo Jin Kim Young‐Joo Lee Young‐Chang Joo Jae Kyeong Jeong 《固体物理学:研究快报》2013,7(3):196-198
Zn–Sn–O (ZTO) thin film transistors (TFTs) were fabricated with a Cu source/drain electrode. Although a reasonably high mobility (μFE) of 13.2 cm2/Vs was obtained for the ZTO TFTs, the subthreshold gate swing (SS) and threshold voltage (Vth) of 1.1 V/decade and 9.1 V, respectively, were inferior. However, ZTO TFTs with Ta film inserted as a diffusion barrier, exhibited improved SS and Vth values of 0.48 V/decade and 3.0 V, respectively as well as a high μFE value of 18.7 cm2/Vs. The improvement in the Ta‐inserted device was attributed to the suppression of Cu lateral diffusion into the ZTO channel region. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
174.
K. R. Sun M. W. Jang H. C. Park H. M. Jeong K. S. Yoon B. K. Kim 《Journal of Macromolecular Science: Physics》2013,52(4):795-805
The a-D-glucose was chemically modified with an allyl isocyanate (MG) and introduced into the polymer matrix for holographic polymer-dispersed liquid crystal (HPDLC), and the effects were studied in terms of morphology, grating formulation dynamics and electro-optical and biodegradable properties. Phase separation and diffraction efficiency increased at low content of (MG ≤ 4 wt%), while a rapid increase in crosslink density entrapped the LC droplets within the polymer to give poor phase separation, small droplet size, and low diffraction efficiency at high content. The HPDLC film was driven only with the addition of MG due to the increased droplet size with a minimum driving voltage of 18 V at 6.0 wt% MG. With the addition and an increasing amount of MG, the biodegradation of the composite film in a buffer solution was significantly increased in proportion to its amount. 相似文献
175.
Hyun-Ju Chung Dong-Hoon Lee Do-Wan Kim Sung-Joon Park Yu-Soo Lee Jung-Hwan Hong Joong-Mann Kim Hee-Je Kim 《Optics & Laser Technology》2001,33(3):269
We propose a simple power supply for a longitudinally pulsed CO2 laser with long pulse duration by the switching control of AC line (60 Hz) on HV leakage transformer primary, which can generate long pulse of about 3 ms compared to a typical pulsed power supply. In this power supply, a low voltage open loop control for high voltage discharge circuit is employed to avoid the HV sampling or switching, and AC line voltage switched directly by a SCR is applied to the leakage transformer primary. Thus, there is no need of a rectified bridge and an energy-storage capacitor in the discharge circuit, and the leakage transformer allows one to omit a current-limiting resistor. In order to control the laser output power, the pulse repetition rate is adjusted up to 60 Hz. A ZCS circuit and a PIC one-chip microprocessor are used to control the gate signal of SCR precisely. 相似文献
176.
177.
Al-Mahmnur Alam Mohammad Kamruzzaman Sang Hak Lee Young Ho Kim Hae Jin Jo Sung Hong Kim Sang-Ryoul Park 《Journal of luminescence》2012,132(3):789-794
A new spectroflurometric method for the determination of adenosine disodium triphosphate (ATP) is developed. Fluorometric interaction between ATP and enoxacin (ENX)–Eu3+ complex was studied using UV–vis and fluorescence spectroscopy. Weak luminescence spectra of Eu3+ were enhanced after complexation with ENX at 589 nm and 614 nm upon excitation at 395 nm due to energy transfer from the ligand to the lanthanide ion. It was observed that luminescence spectrum of Eu3+ was strongly enhanced further at 614 nm after incorporation of ATP into the ENX–Eu3+ complex. Under optimal conditions, the enhancement of luminescence at 614 nm was responded linearly with the concentration of ATP. The linearity was maintained in the range of 1.5×10?10–1.15×10?8 M (R=0.9973) with the limit of detection (3σ) of 4.71×10?11 M. The relative standard deviation (RSD) for 9 repeated measurements of 1×10?9 M ATP was 1.25%. Successful determinations of ATP in soil, milk, and a pharmaceutical formulation with the proposed method were demonstrated. 相似文献
178.
Hye Young Kwon Jun Taek Woo Dea Uk Lee Tae Whan Kim Young Ju Park 《Solid State Communications》2009,149(1-2):52-55
Strained potential profiles and electronic subband energies of InAs/GaAs coupled double quantum dots (DQDs) were calculated by using a three-dimensional finite-difference method (FDM) taking into account shape-based strain and nonparabolic effects. The interband transition energies from the ground electronic subband to the ground heavy-hole band (E1-HH1) in the InAs/GaAs DQDs, as determined from the FDM calculations taking into account strain and nonparabolic effects, were in reasonable agreement with the experimental peaks corresponding to the (E1-HH1) interband transition energies at several temperatures, as determined from the temperature-dependent photoluminescence spectra. 相似文献
179.
Valentina Simonetti Jason Y. Park Nicholas J. Panaro Larry J. Kricka 《Journal of nanoparticle research》2008,10(2):365-368
Nylon nanorods and nanotubes (200 nm diameter) were fabricated by the membrane wetting technique (solvent and melt wetting)
from a range of nylons (6; 6,6; 6,9; 6,10; 6,12; 11; 12, 6(3)T) and nylon blended with different dyes (Nylon Cast Blue, Nylon
6/6 Black) or with molybdenum disulfide (Nylon cast MDS). The 65-μm long nylon nanotubes and nanorods were characterized by
scanning electron microscopy. The nanoscale nylon 6,6 served as an effective high surface area alternative to a nylon membrane
as a solid support in a chemiluminescent assay for nylon-bound biotinylated nucleic acids based on streptavidin- alkaline
phosphatase and chemiluminescent detection of the bound alkaline phosphatase label with the dioxetane substrate, CDP-Star.
Layer-by-layer deposition of the cationic polymer (Sapphire-II™; Tropix) onto the nylon 6,6 nanostructures prior to UV-cross-linking
with biotinylated DNA resulted in further enhancement of binding and detection of biotinylated DNA. 相似文献
180.