全文获取类型
收费全文 | 8693篇 |
免费 | 597篇 |
国内免费 | 23篇 |
专业分类
耳鼻咽喉 | 42篇 |
儿科学 | 252篇 |
妇产科学 | 248篇 |
基础医学 | 1318篇 |
口腔科学 | 181篇 |
临床医学 | 1016篇 |
内科学 | 1660篇 |
皮肤病学 | 240篇 |
神经病学 | 1156篇 |
特种医学 | 217篇 |
外科学 | 705篇 |
综合类 | 67篇 |
一般理论 | 9篇 |
预防医学 | 793篇 |
眼科学 | 300篇 |
药学 | 531篇 |
中国医学 | 20篇 |
肿瘤学 | 558篇 |
出版年
2023年 | 78篇 |
2022年 | 118篇 |
2021年 | 206篇 |
2020年 | 186篇 |
2019年 | 215篇 |
2018年 | 272篇 |
2017年 | 212篇 |
2016年 | 222篇 |
2015年 | 270篇 |
2014年 | 300篇 |
2013年 | 456篇 |
2012年 | 734篇 |
2011年 | 718篇 |
2010年 | 375篇 |
2009年 | 339篇 |
2008年 | 642篇 |
2007年 | 590篇 |
2006年 | 548篇 |
2005年 | 518篇 |
2004年 | 480篇 |
2003年 | 446篇 |
2002年 | 434篇 |
2001年 | 63篇 |
2000年 | 38篇 |
1999年 | 60篇 |
1998年 | 83篇 |
1997年 | 72篇 |
1996年 | 66篇 |
1995年 | 45篇 |
1994年 | 50篇 |
1993年 | 41篇 |
1992年 | 28篇 |
1991年 | 22篇 |
1990年 | 17篇 |
1989年 | 15篇 |
1988年 | 15篇 |
1987年 | 19篇 |
1986年 | 19篇 |
1985年 | 17篇 |
1984年 | 21篇 |
1983年 | 16篇 |
1982年 | 23篇 |
1980年 | 16篇 |
1978年 | 22篇 |
1977年 | 14篇 |
1976年 | 12篇 |
1975年 | 12篇 |
1971年 | 12篇 |
1970年 | 11篇 |
1968年 | 11篇 |
排序方式: 共有9313条查询结果,搜索用时 15 毫秒
41.
Retrospective analysis of selective lymphadenectomy in apparent early-stage endometrial cancer. 总被引:8,自引:0,他引:8
Janiel M Cragun Laura J Havrilesky Brian Calingaert Ingrid Synan Angeles Alvarez Secord John T Soper Daniel L Clarke-Pearson Andrew Berchuck 《Journal of clinical oncology》2005,23(16):3668-3675
PURPOSE: Selective lymphadenectomy is widely accepted in the management of endometrial cancer. Purported benefits are individualization of adjuvant therapy based on extent of disease and resection of occult metastases. Our goal was to assess effects of the extent of selective lymphadenectomy on outcomes in women with apparent stage I endometrial cancer at laparotomy. PATIENTS AND METHODS: Patients with endometrial cancer who received primary surgical treatment between 1973 and 2002 were identified through an institutional tumor registry. Inclusion criteria were clinical stage I/IIA disease and procedure including hysterectomy and selective lymphadenectomy (pelvic or pelvic + aortic). Exclusion criteria included presurgical radiation, grossly positive lymph nodes, or extrauterine metastases at laparotomy. Recurrence and survival were analyzed using Kaplan-Meier analysis and Cox proportional hazards model. RESULTS: Among 509 patients, the median number of lymph nodes removed was 15 (median pelvic, 11; median aortic, three). Pelvic and aortic node metastases were found in 24 (5%) of 509 patients and 11 (3%) of 373 patients, respectively. Patients with poorly differentiated cancers having more than 11 pelvic nodes removed had improved overall survival (hazard ratio [HR], 0.25; P < .0001) and progression-free survival (HR, 0.26; P < .0001) compared with patients having poorly differentiated cancers with 11 or fewer nodes removed. Number of nodes removed was not predictive of survival among patients with cancers of grade 1 to 2. Performance of aortic selective lymphadenectomy was not associated with survival. Three (27%) of 11 patients with microscopic aortic nodal metastasis are alive without recurrence. CONCLUSION: These data add to the literature documenting the possible therapeutic benefit of selective lymphadenectomy in management of patients with apparent early-stage endometrial cancer. 相似文献
42.
Cytochrome P450 epoxygenases as EDHF synthase(s) 总被引:2,自引:0,他引:2
The metabolism of arachidonic acid by cytochrome P450 (CYP) epoxygenases generates epoxyeicosatrienoic acids (EETs) which affect numerous cellular process including Ca(2+) signaling and the activity of Ca(2+)-dependent K(+) channels. The expression of the CYP epoxygenase(s) that generate EETs in endothelial cells is not constitutive but is determined by a number of physical (fluid shear stress and cyclic stretch) and pharmacological stimuli which also affect responses attributed to an endothelium-derived hyperpolarizing factor (EDHF). This review summarizes the role played by EETs, and the enzymes that generate and metabolize them, in EDHF-mediated responses. 相似文献
43.
Bertil Abrahamsson Tamsin Albery Anna Eriksson Ingrid Gustafsson Marie Sj?berg 《European journal of pharmaceutical sciences》2004,22(2-3):165-172
The aims of the present study was to investigate if food components, as represented by a multi-component nutritional drink for tube feeding, could affect tablet disintegration of standard tablets in vitro as well as in vivo and propose a mechanism for potential food effects on tablet disintegration. The tablet disintegration was delayed between 5 min and more than 1h in the simulated gastric fed medium compared to a simple buffer. This effect was dependent on the tablet composition. A similar delay in tablet disintegration was also found in vivo after administration of the nutritional drink to three Labradors as observed by removing the tablet from the stomach at different times through a gastric fistula. The delay in tablet disintegration appeared to be caused by precipitation of a film, mainly consisting of protein, on the tablet surface as indicated by disintegration studies with pure nutrients, identification by IR spectroscopy of contents of precipitates obtained in a model study were the nutrients were incubated with different tablet excipients and visual observations of tablets exposed to the simulated fed medium. The drug dissolution of a soluble compound, metoprolol tartrate, from a standard tablet was also strongly delayed in the simulated fed medium. In conclusion, food, could significantly delay tablet disintegration and drug dissolution in the stomach by formation of a film around the tablets. This effect could be monitored by a simple in vitro disintegration test using a test medium based on a nutritional drink. More studies are needed to investigate the significance of the slow tablet disintegrations on bioavailability and for which types of food the present effect occurs. 相似文献
44.
Laura M. Carlson Michelle Angrish Avanti V. Shirke Elizabeth G. Radke Brittany Schulz Andrew Kraft Richard Judson Grace Patlewicz Robyn Blain Cynthia Lin Nicole Vetter Courtney Lemeris Pamela Hartman Heidi Hubbard Xabier Arzuaga Allen Davis Laura V. Dishaw Ingrid L. Druwe Hillary Hollinger Ryan Jones J. Phillip Kaiser Lucina Lizarraga Pamela D. Noyes Michele Taylor Andrew J. Shapiro Antony J. Williams Kristina A. Thayer 《Environmental health perspectives》2022,130(5)
Background: Per- and polyfluoroalkyl substances (PFAS) are a large class of synthetic (man-made) chemicals widely used in consumer products and industrial processes. Thousands of distinct PFAS exist in commerce. The 2019 U.S. Environmental Protection Agency (U.S. EPA) Per- and Polyfluoroalkyl Substances (PFAS) Action Plan outlines a multiprogram national research plan to address the challenge of PFAS. One component of this strategy involves the use of systematic evidence map (SEM) approaches to characterize the evidence base for hundreds of PFAS.Objective: SEM methods were used to summarize available epidemiological and animal bioassay evidence for a set of PFAS that were prioritized in 2019 by the U.S. EPA’s Center for Computational Toxicology and Exposure (CCTE) for in vitro toxicity and toxicokinetic assay testing.Methods: Systematic review methods were used to identify and screen literature using manual review and machine-learning software. The Populations, Exposures, Comparators, and Outcomes (PECO) criteria were kept broad to identify mammalian animal bioassay and epidemiological studies that could inform human hazard identification. A variety of supplemental content was also tracked, including information on in vitro model systems; exposure measurement–only studies in humans; and absorption, distribution, metabolism, and excretion (ADME). Animal bioassay and epidemiology studies meeting PECO criteria were summarized with respect to study design, and health system(s) were assessed. Because animal bioassay studies with exposure duration (or reproductive/developmental study design) were most useful to CCTE analyses, these studies underwent study evaluation and detailed data extraction. All data extraction is publicly available online as interactive visuals with downloadable metadata.Results: More than 40,000 studies were identified from scientific databases. Screening processes identified 44 animal and 148 epidemiology studies from the peer-reviewed literature and 95 animal and 50 epidemiology studies from gray literature that met PECO criteria. Epidemiological evidence (available for 15 PFAS) mostly assessed the reproductive, endocrine, developmental, metabolic, cardiovascular, and immune systems. Animal evidence (available for 40 PFAS) commonly assessed effects in the reproductive, developmental, urinary, immunological, and hepatic systems. Overall, 45 PFAS had evidence across animal and epidemiology data streams.Discussion: Many of the PFAS were data poor. Epidemiological and animal evidence were lacking for most of the PFAS included in our search. By disseminating this information, we hope to facilitate additional assessment work by providing the initial scoping literature survey and identifying key research needs. Future research on data-poor PFAS will help support a more complete understanding of the potential health effects from PFAS exposures. https://doi.org/10.1289/EHP10343 相似文献
45.
46.
Miethbauer S Günther W Schmidtke KU Heiser I Gräfe S Gitter B Liebermann B 《Journal of natural products》2008,71(8):1371-1375
Both the phytopathogenic fungus Ramularia collo-cygni and the hyperparasite R. uredinicola biosynthesize a number of red and yellow anthraquinone derivatives called rubellins. The new compounds uredinorubellins I and II, which were isolated from R. uredinicola, contribute to understanding the biosynthesis pathway that leads from simple anthraquinones to the rubellins. In addition, we isolated for the first time such simple compounds as chrysophanol and helminthsporin from both Ramularia species. A blue compound isolated from the mycelium of R. collo-cygni was revealed to be a unique 9,4-anthracenedione derivative. Structure elucidation by (1)H and (13)C NMR of the new but unstable compound caeruleoramularin was possible only by feeding the fungus different labeled (13)C acetates. The photodynamic activity of the uredinorubellins was comparable to rubellin D, whereas chrysophanol and caeruleoramularin did not display such activity. 相似文献
47.
48.
49.
50.