全文获取类型
收费全文 | 9207篇 |
免费 | 730篇 |
国内免费 | 88篇 |
专业分类
耳鼻咽喉 | 198篇 |
儿科学 | 278篇 |
妇产科学 | 150篇 |
基础医学 | 1097篇 |
口腔科学 | 167篇 |
临床医学 | 1228篇 |
内科学 | 1862篇 |
皮肤病学 | 64篇 |
神经病学 | 571篇 |
特种医学 | 435篇 |
外国民族医学 | 2篇 |
外科学 | 1217篇 |
综合类 | 207篇 |
一般理论 | 5篇 |
预防医学 | 1022篇 |
眼科学 | 279篇 |
药学 | 801篇 |
中国医学 | 8篇 |
肿瘤学 | 434篇 |
出版年
2023年 | 59篇 |
2022年 | 77篇 |
2021年 | 157篇 |
2020年 | 92篇 |
2019年 | 179篇 |
2018年 | 163篇 |
2017年 | 124篇 |
2016年 | 142篇 |
2015年 | 172篇 |
2014年 | 240篇 |
2013年 | 310篇 |
2012年 | 460篇 |
2011年 | 458篇 |
2010年 | 289篇 |
2009年 | 219篇 |
2008年 | 353篇 |
2007年 | 436篇 |
2006年 | 384篇 |
2005年 | 364篇 |
2004年 | 302篇 |
2003年 | 308篇 |
2002年 | 292篇 |
2001年 | 283篇 |
2000年 | 289篇 |
1999年 | 260篇 |
1998年 | 126篇 |
1997年 | 136篇 |
1996年 | 129篇 |
1995年 | 108篇 |
1994年 | 116篇 |
1993年 | 87篇 |
1992年 | 216篇 |
1991年 | 254篇 |
1990年 | 194篇 |
1989年 | 192篇 |
1988年 | 171篇 |
1987年 | 178篇 |
1986年 | 172篇 |
1985年 | 179篇 |
1984年 | 124篇 |
1983年 | 105篇 |
1981年 | 66篇 |
1979年 | 101篇 |
1978年 | 68篇 |
1976年 | 72篇 |
1974年 | 65篇 |
1973年 | 68篇 |
1972年 | 73篇 |
1971年 | 62篇 |
1970年 | 59篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
Bailey SH Shapiro SB Mone MC Saffle JR Morris SE Barton RG 《American journal of surgery》2000,180(6):517-21; discussion 521-2
BACKGROUND: Current standard of care dictates that central venous catheter (CVC) insertion should be followed by an immediate chest radiograph to confirm appropriate position and rule out complications. We hypothesized that a subset of monitored intensive care unit patients exists that is at low risk for complications and might safely have radiographic evaluation of line placement deferred until the next scheduled radiograph. METHODS: Data regarding patient and procedural characteristics were obtained prospectively for 184 CVC placed between March 1, 1998, and June 30, 1999. Retrospective data regarding complications were obtained by chart review for an additional 174 CVC placed during the study period but for which data sheets were not completed. All procedures were followed by chest radiography. RESULTS: We documented a complication rate of 9% with the vast majority (25 of 31, 81%) of complications consisting of incorrect positioning. The number of needle passes was greater in the group suffering pneumothorax and arterial puncture than the uncomplicated group (5.6 versus 1.9, P = 0.008). "Straightforward" operator gestalt (P = 0.04) and number of needle passes <3 (P = 0.03) were factors correlating with the absence of complications. These factors had negative predictive values of 94% and 96%, respectively. CONCLUSION: Placement of CVC is safe in experienced hands. In monitored intensive care unit patients who undergo a "straightforward" procedure with <3 needle passes, chest radiograph can be safely deferred until the next scheduled examination. 相似文献
122.
Mariani J Ou R Bailey M Rowland M Nagley P Rosenfeldt F Pepe S 《The Journal of thoracic and cardiovascular surgery》2000,120(4):660-667
BACKGROUND: Recovery of cardiac function after cardiac surgery and other interventional cardiac procedures in elderly patients is inferior to that in younger patients, suggesting that the aged myocardium is more sensitive to ischemia and other stresses. Although convincing data from animal studies of senescence now exist, there is a dearth of controlled in vitro studies that examine the specific response of aged human myocardium to the stress of hypoxia or ischemia. OBJECTIVE: We sought to determine the effect of age on the capacity of human atrial trabeculae to recover contractile function after in vitro hypoxic or ischemic stress. METHODS: Atrial pectinate trabeculae were dissected from the tip of 58 right atrial appendages harvested during an operation in patients aged between 34 and 89 years and electrically stimulated at 1 Hz in oxygenated Ringer's solution at 37 degrees C. Tissues experienced 30 minutes of either hypoxia (N(2) and perfusate) or simulated ischemia (humidified N(2) without perfusate) and were returned to normoxia for recovery of function for 30 minutes. Developed force and other contractile variables were determined during each period. RESULTS: Under normoxic conditions, no significant age difference was observed for any contractile function variable. However, after hypoxia, the old (70-89 years) and intermediate age groups (60-69 years) showed reduced recovery of developed force (48.5% +/- 22.2% [n = 11] and 44.9% +/- 19% [n = 12], respectively) compared with that found (66.4% +/- 19.7% [n = 15]) in the younger (34-59 years) group (mean +/- SD, P =.02). Similarly, after simulated ischemia, the groups of 70- to 89-year-old and 60- to 69-year-old subjects showed reduced recovery of developed force (35.7% +/- 17% [n = 5] and 51.1% +/- 11.8% [n = 9], respectively) compared with that found (68.2% +/- 10.4% [n = 6]) in the group of 34- to 59-year-old subjects (P =.01). Multivariable analysis, comparing 20 factors of surgical patient characteristics and recovery of developed force, found that only age (P =.01) and hypertension (P =.01) were predictors of reduced recovery of developed force after either hypoxia or simulated ischemia. CONCLUSIONS: In aged human atrial myocardium, the capacity to recover contractile function after in vitro hypoxia or simulated ischemia is reduced compared with the younger myocardium of mature adults. These findings suggest that enhanced myocardial protective strategies may be indicated for elderly patients undergoing cardiac surgery. 相似文献
123.
Our understanding of the actions of extracellular ATP in controlling kidney function via stimulation of P2 receptors is still at an early stage. Recently, several groups, including our own, have begun to address this subject: in this brief review, we discuss some of these effects and speculate on likely function of extracellular nucleotides in the kidney. 相似文献
124.
Epidermal growth factor receptor mutations and gene amplification in non-small-cell lung cancer: molecular analysis of the IDEAL/INTACT gefitinib trials. 总被引:15,自引:0,他引:15
Daphne W Bell Thomas J Lynch Sara M Haserlat Patricia L Harris Ross A Okimoto Brian W Brannigan Dennis C Sgroi Beth Muir Markus J Riemenschneider Renee Bailey Iacona Annetta D Krebs David H Johnson Giuseppe Giaccone Roy S Herbst Christian Manegold Masahiro Fukuoka Mark G Kris José Baselga Judith S Ochs Daniel A Haber 《Journal of clinical oncology》2005,23(31):8081-8092
PURPOSE: Most cases of non-small-cell lung cancer (NSCLC) with dramatic responses to gefitinib have specific activating mutations in the epidermal growth factor receptor (EGFR), but the predictive value of these mutations has not been defined in large clinical trials. The goal of this study was to determine the contribution of molecular alterations in EGFR to response and survival within the phase II (IDEAL) and phase III (INTACT) trials of gefitinib. PATIENTS AND METHODS: We analyzed the frequency of EGFR mutations in lung cancer specimens from both the IDEAL and INTACT trials and compared it with EGFR gene amplification, another genetic abnormality in NSCLC. RESULTS: EGFR mutations correlated with previously identified clinical features of gefitinib response, including adenocarcinoma histology, absence of smoking history, female sex, and Asian ethnicity. No such association was seen in patients whose tumors had EGFR amplification, suggesting that these molecular markers identify different biologic subsets of NSCLC. In the IDEAL trials, responses to gefitinib were seen in six of 13 tumors (46%) with an EGFR mutation, two of seven tumors (29%) with amplification, and five of 56 tumors (9%) with neither mutation nor amplification (P = .001 for either EGFR mutation or amplification v neither abnormality). Analysis of the INTACT trials did not show a statistically significant difference in response to gefitinib plus chemotherapy according to EGFR genotype. CONCLUSION: EGFR mutations and, to a lesser extent, amplification appear to identify distinct subsets of NSCLC with an increased response to gefitinib. The combination of gefitinib with chemotherapy does not improve survival in patients with these molecular markers. 相似文献
125.
S Gananadha TDB Yan J Zhao P Clingan D Glenn DL Morris 《Journal of Medical Imaging and Radiation Oncology》2005,49(5):396-399
Hepatic artery infusion (HAI) chemotherapy is associated with higher response rates compared to systemic chemotherapy in those patients with unresectable liver malignancies. Operative hepatic artery catheter (HAC) insertion has significant morbidity and mortality, especially in patients with high‐volume disease, some of whom may not respond to HAI chemotherapy. We report our experience in 45 patients with high‐volume liver disease who were initially treated with HAI chemotherapy via a radiologically placed temporary HAC to try to select the responders who then went on to have an operative HAC. In these 45 patients who had 62 radiologically placed HAC, we found very few major complications, and certainly no complications such as cholecystitis, vascular or malperfusion problems. 相似文献
126.
127.
Emily Banks Gillian Reeves Valerie Beral Diana Bull Barbara Crossley Moya Simmonds Elizabeth Hilton Stephen Bailey Nigel Barrett Peter Briers Ruth English Alan Jackson Elizabeth Kutt Janet Lavelle Linda Rockall Matthew G Wallis Mary Wilson Julietta Patnick 《British medical journal》2004,328(7451):1291-1292
128.
Joe E.Acker Ⅲ Todd J.Crocco Marc K.Eckstein Edward C.Jauch Neil M.Meltzer John W.Munn Charles Sand Jeffrey L.Saver Brian Eigel Brian R.Gilpin Mark Schoeberl Penelope Solis Katie B.Hortort 曹勇军 李瑞霞 刘芳 刘春风 《国际脑血管病杂志》2008,16(7):481-498
尽管卒中的预防、诊断、治疗和康复已取得一些进展,但卒中在美国仍然是第三大死亡原因和长期残疾的主要原因.每年约有70万人新发或复发卒中[1].在过去10年里,急性卒中诊治的一些进展,包括纤溶和其他短期疗法的引入,突出显示了急诊医疗服务(emergency medical services,EMS)机构和急诊医疗服务体系(emergency medical services systems,EMSS)在优化卒中医疗中的关键作用[2-7]. 相似文献
129.
130.
Michelle N. Vu Kumari G. Lokugamage Jessica A. Plante Dionna Scharton Aaron O. Bailey Stephanea Sotcheff Daniele M. Swetnam Bryan A. Johnson Craig Schindewolf R. Elias Alvarado Patricia A. Crocquet-Valdes Kari Debbink Scott C. Weaver David H. Walker William K. Russell Andrew L. Routh Kenneth S. Plante Vineet D. Menachery 《Proceedings of the National Academy of Sciences of the United States of America》2022,119(32)
The furin cleavage site (FCS), an unusual feature in the SARS-CoV-2 spike protein, has been spotlighted as a factor key to facilitating infection and pathogenesis by increasing spike processing. Similarly, the QTQTN motif directly upstream of the FCS is also an unusual feature for group 2B coronaviruses (CoVs). The QTQTN deletion has consistently been observed in in vitro cultured virus stocks and some clinical isolates. To determine whether the QTQTN motif is critical to SARS-CoV-2 replication and pathogenesis, we generated a mutant deleting the QTQTN motif (ΔQTQTN). Here, we report that the QTQTN deletion attenuates viral replication in respiratory cells in vitro and attenuates disease in vivo. The deletion results in a shortened, more rigid peptide loop that contains the FCS and is less accessible to host proteases, such as TMPRSS2. Thus, the deletion reduced the efficiency of spike processing and attenuates SARS-CoV-2 infection. Importantly, the QTQTN motif also contains residues that are glycosylated, and disruption of its glycosylation also attenuates virus replication in a TMPRSS2-dependent manner. Together, our results reveal that three aspects of the S1/S2 cleavage site—the FCS, loop length, and glycosylation—are required for efficient SARS-CoV-2 replication and pathogenesis.SARS-CoV-2 emerged in late 2019 and has caused the largest pandemic since the 1918 influenza outbreak (1). An unusual feature of SARS-CoV-2 is the presence of a furin cleavage site (FCS) in its spike protein (2). The CoV spike is a trimer of spike proteins composed of the S1 and S2 subunits, responsible for receptor binding and membrane fusion, respectively (1). After receptor binding, the spike protein is proteolytically cleaved at the S1/S2 and S2′ sites to activate the fusion machinery. For SARS-CoV-2, the spike protein contains a novel cleavage motif recognized by the host cell furin protease (PRRAR) directly upstream of the S1/S2 cleavage site that facilitates cleavage prior to virion release from the producer cell. This FCS, not found in other group 2B CoVs, plays a key role in spike processing, infectivity, and pathogenesis as shown by our group and others (3, 4).Importantly, another novel amino acid motif, QTQTN, is found directly upstream of the FCS. This QTQTN motif, also absent in other group 2B CoVs, is often deleted and has been pervasive in cultured virus stocks of the alpha, beta, and delta variants (5–8). In addition, the QTQTN deletion has been observed in a small subset of patient samples as well (9–11). Because this deletion has been frequently identified, we set out to characterize it and determine whether it has consequences for viral replication and virulence. Using our infectious clone (12, 13), we demonstrated that the loss of this motif attenuates SARS-CoV-2 replication in respiratory cells in vitro and pathogenesis in hamsters. The QTQTN deletion results in reduced spike cleavage and diminished capacity to use serine proteases on the cell surface for entry. Importantly, mutations of glycosylation-enabling residues in the QTQTN motif results in similar replication attenuation despite intact spike processing. Together, our results highlight elements in the SARS-CoV-2 spike in addition to the FCS that contribute to increased replication and pathogenesis. 相似文献