全文获取类型
收费全文 | 3401篇 |
免费 | 144篇 |
国内免费 | 26篇 |
专业分类
耳鼻咽喉 | 41篇 |
儿科学 | 51篇 |
妇产科学 | 47篇 |
基础医学 | 338篇 |
口腔科学 | 142篇 |
临床医学 | 211篇 |
内科学 | 825篇 |
皮肤病学 | 46篇 |
神经病学 | 186篇 |
特种医学 | 248篇 |
外科学 | 556篇 |
综合类 | 7篇 |
一般理论 | 1篇 |
预防医学 | 182篇 |
眼科学 | 65篇 |
药学 | 229篇 |
中国医学 | 2篇 |
肿瘤学 | 394篇 |
出版年
2023年 | 22篇 |
2022年 | 37篇 |
2021年 | 53篇 |
2020年 | 26篇 |
2019年 | 42篇 |
2018年 | 51篇 |
2017年 | 40篇 |
2016年 | 39篇 |
2015年 | 41篇 |
2014年 | 71篇 |
2013年 | 88篇 |
2012年 | 120篇 |
2011年 | 141篇 |
2010年 | 85篇 |
2009年 | 67篇 |
2008年 | 127篇 |
2007年 | 142篇 |
2006年 | 145篇 |
2005年 | 154篇 |
2004年 | 150篇 |
2003年 | 140篇 |
2002年 | 171篇 |
2001年 | 147篇 |
2000年 | 174篇 |
1999年 | 137篇 |
1998年 | 57篇 |
1997年 | 37篇 |
1996年 | 32篇 |
1995年 | 41篇 |
1994年 | 29篇 |
1993年 | 27篇 |
1992年 | 93篇 |
1991年 | 86篇 |
1990年 | 62篇 |
1989年 | 81篇 |
1988年 | 58篇 |
1987年 | 58篇 |
1986年 | 70篇 |
1985年 | 59篇 |
1984年 | 44篇 |
1983年 | 36篇 |
1982年 | 15篇 |
1979年 | 32篇 |
1978年 | 20篇 |
1977年 | 23篇 |
1976年 | 17篇 |
1975年 | 26篇 |
1974年 | 22篇 |
1973年 | 19篇 |
1972年 | 21篇 |
排序方式: 共有3571条查询结果,搜索用时 0 毫秒
41.
42.
Matsuo H Tsukada S Nakata T Chairoungdua A Kim DK Cha SH Inatomi J Yorifuji H Fukuda J Endou H Kanai Y 《Neuroreport》2000,11(16):3507-3511
Amino acid transport system L has been proposed to be one of the major nutrient transport systems at the blood-brain barrier. Using immunohistochemical analyses, a system L transporter LAT1 was shown to be expressed in the brain capillary endothelial cells in rats. Because LAT1 was coexpressed with 4F2 heavy chain which brings LAT1 to the plasma membrane, LAT1 is proposed to be functional in the plasma membrane of brain capillary endothelial cells. Both LAT1 and 4F2hc immunoreactivities were detected in a double line appearance surrounding endothelial cell nuclei, suggesting both proteins are present in the luminal and abluminal membranes. LAT1 is, thus, a blood-brain barrier system L transporter responsible for the permeation of aromatic or branched-chain amino acids and amino acid-related drugs such as L-DOPA. 相似文献
43.
BACKGROUND: The minimum alveolar concentration (MAC)-awake is a traditional index of hypnotic potency of an inhalational anesthetic. The MAC-awake of xenon, an inert gas with anesthetic properties (MAC = 71%), has not been determined. It is also unknown how xenon interacts with isoflurane or sevoflurane on the MAC-awake. METHODS: In the first part of the study, 90 female patients received xenon, nitrous oxide (N2O), isoflurane, or sevoflurane supplemented with epidural anesthesia (n = 36 for xenon and n = 18 per group for other anesthetics). In the second part, 72 additional patients received either xenon or N2O combined with the 0.5 times MAC-awake concentration of isoflurane or sevoflurane (0.2% and 0.3%, respectively, based on the results of the first part; n = 18 per group). During emergence, the concentration of an assigned anesthetic (xenon or N2O only in the second part) was decreased in 0. 1 MAC decrements every 15 min from 0.8 MAC or from 70% in the case of N2O until the patient followed the command to either open her eyes or to squeeze and release the investigator's hand. The concentration midway between the value permitting the first response to command and that just preventing it was defined as the MAC-awake. RESULTS: The MAC-awake were as follows: xenon, 32.6 +/- 6.1% (mean +/- SD) or 0.46 +/- 0.09 MAC; N2O, 63.3 +/- 7.1% (0.61 +/- 0.07 MAC); isoflurane, 0.40 +/- 0.07% (0.35 +/- 0.06 MAC); and sevoflurane, 0.59 +/- 0.10% (0.35 +/- 0.06 MAC). Addition of the 0.5 MAC-awake concentrations of isoflurane and sevoflurane reduced the MAC-awake of xenon to 0.50 +/- 0.15 and 0.51 +/- 0.16 times its MAC-awake as a sole agent, but that of N2O to the values significantly greater than 0.5 times its MAC-awake as a sole agent (0.68 +/- 0.12 and 0.66 +/- 0.14 times MAC-awake; P < 0.01, analysis of variance and Dunnett's test). CONCLUSIONS: The MAC-awake of xenon is 33% or 0.46 times its MAC. In terms of the MAC-fraction, this is smaller than that for N2O but greater than those for isoflurane and sevoflurane. Unlike N2O, xenon interacts additively with isoflurane and sevoflurane on MAC-awake. 相似文献
44.
Sakai K Oyama Y Okada Y Akaike N Nakata M Chikahisa L 《Environmental toxicology and pharmacology》2001,10(3):95-101
Tri-n-butyltin (TBT), one of environmental pollutants accumulated in mollusks, at nanomolar concentrations decreases cellular content of glutathione (GSH), suggesting that TBT increases cell vulnerability to oxidative stress because GSH has a role in catabolizing hydrogen peroxide (H(2)O(2)). In order to examine this possibility, the effect of tri-n-butyltin chloride (TBTCl) on rat thymocytes suffering from oxidative stress induced by H(2)O(2) was examined using a flow cytometer with four fluorescent probes; ethidium bromide, 2',7'-dichlorofluorescin diacetate, 5-chloromethylfluorescein diacetate and annexin-V-FITC. TBTCl at concentrations ranging from 100 nM to 1 μM attenuated H(2)O(2)-induced decrease in cell viability in a dose-dependent manner. It was unlikely that TBTCl reduced H(2)O(2)-induced oxidative stress because TBTCl failed to affect H(2)O(2)-induced oxidation of intracellular molecule (2',7'-dichlorofluorescin) and H(2)O(2)-induced decrease in cellular content of GSH. Results suggest that TBTCl may inhibit the pathway of cell death induced by H(2)O(2) or that TBTCl may induce a protective substance against the oxidative stress produced by H(2)O(2). 相似文献
45.
Potentiation of tumor response to radiation or chemoradiation by selective cyclooxygenase-2 enzyme inhibitors 总被引:15,自引:0,他引:15
Nakata E Mason KA Hunter N Husain A Raju U Liao Z Ang KK Milas L 《International journal of radiation oncology, biology, physics》2004,58(2):369-375
Cyclooxygenase-2 (COX-2) is an enzyme expressed primarily in pathologic states, such as inflammatory disorders and cancer, where it mediates prostaglandin production. Its overexpression is associated with more aggressive biologic tumor behavior and adverse patient outcome. Increasing evidence shows that agents that selectively inhibit COX-2 enhance tumor response to radiation or chemotherapeutic agents. This article gives an overview of some of this evidence. In addition, we describe new results showing that celecoxib, a selective COX-2 inhibitor, enhanced response of A431 human tumor xenografts in nude mice to radiation by an enhancement factor (EF) of 1.43 and to the chemotherapeutic agent docetaxel by an EF of 2.07. Celecoxib also enhanced tumor response when added to the combined docetaxel plus radiation treatment (EF = 2.13). Further experiments showed that selective COX-2 inhibitors enhanced tumor cell sensitivity to ionizing radiation, involving inhibition of cellular repair from radiation damage and cell cycle redistribution as mechanisms for some cell types. The results show that selective COX-2 inhibitors have the potential to improve tumor radiotherapy or radiochemotherapy, and this therapeutic strategy is currently under clinical testing. 相似文献
46.
47.
Neeraj Sood Victoria L. Shier Haley Nakata Richard Iorio Jay R. Lieberman 《The Journal of arthroplasty》2019,34(4):609-612.e1
Background
Comprehensive Care for Joint Replacement (CJR) is a Medicare initiative to test the impact of holding a hospital accountable for services provided during an episode of care for a lower extremity joint arthroplasty on costs and quality. This study examines whether hospital participation in CJR is associated with having programs focused on improving posthospitalization care or reducing costs using a survey of orthopedic surgeons.Methods
Seventy-three (of 104) orthopedic surgeon members of the Hip Society, a national professional organization of hip surgeons, completed the survey.Results
Surgeons practicing in CJR hospitals were more likely to report that their hospital had implemented programs focused on improving posthospitalization care or reducing costs. Surgeons in CJR hospitals were significantly more likely to report that the hospital had a narrow network of skilled nursing facilities to enhance care and limit length of stay in skilled nursing facilities (83% vs 47%, P < .01). Surgeons in CJR hospitals were also more likely to report the hospital provides incentives or some type of gainsharing. There were no statistically significant differences in implementation of having programs to reduce costs or improve care during hospitalization.Conclusion
Participation in CJR is associated with higher utilization of hospital practices aimed at improving postdischarge care and higher utilization of linking surgeon compensation to cost and quality. 相似文献48.
49.
Masaki Y Sumiyoshi M Suwa S Ohta H Matsunaga E Tamura H Takaya N Mineda Y Kojima S Nakata Y 《International heart journal》2005,46(2):323-326
Dissection of the sinus of Valsalva is an extremely rare accident during percutaneous coronary intervention (PCI), but it can lead to serious complications such as dissection of the ascending aorta. We experienced a localized dissection of the right coronary cusp without coronary artery involvement that was induced by a guiding catheter during PCI in a patient with acute myocardial infarction. The localized dissection showed pooling of the contrast medium in the acute phase, but it subsided spontaneously after 12 days without any sequelae. Manipulation of the guiding catheter should be performed with great caution not only in the coronary artery but also in the sinus of Valsalva. 相似文献
50.
SOS-inducible DNA repair proteins, RuvA and RuvB, of Escherichia coli: functional interactions between RuvA and RuvB for ATP hydrolysis and renaturation of the cruciform structure in supercoiled DNA. 总被引:11,自引:4,他引:11 下载免费PDF全文
T Shiba H Iwasaki A Nakata H Shinagawa 《Proceedings of the National Academy of Sciences of the United States of America》1991,88(19):8445-8449
The ruv operon is induced by treatments that damage DNA and is regulated by the LexA repressor. It encodes two proteins, RuvA and RuvB, that are involved in DNA repair, recombination in RecE and RecF pathways, and mutagenesis. RuvB protein was previously purified and has ATP-binding activity and weak ATPase activity. To study the biochemical properties of RuvA and its interaction with RuvB, we purified RuvA protein to near homogeneity from an over-producing strain. RuvA bound more efficiently to single-stranded DNA than to double-stranded DNA. RuvA bound to DNA greatly enhanced the ATPase activity of RuvB; the enhancing effect of various forms of DNA was in the order of supercoiled DNA greater than single-stranded DNA greater than linear double-stranded DNA. UV irradiation further enhanced the ATPase stimulatory effect of supercoiled DNA dose dependently. The RuvA-RuvB complex has an activity that renatures the cruciform structure in supercoiled DNA. From these experiments and previous work, we infer that the RuvA-RuvB complex may promote branch migration in recombination and may correct irregular structures in DNA, such as cruciforms and hairpins, to facilitate DNA repair using ATP as the energy source. 相似文献