全文获取类型
收费全文 | 11858篇 |
免费 | 758篇 |
国内免费 | 23篇 |
专业分类
耳鼻咽喉 | 75篇 |
儿科学 | 417篇 |
妇产科学 | 233篇 |
基础医学 | 1382篇 |
口腔科学 | 156篇 |
临床医学 | 1296篇 |
内科学 | 1997篇 |
皮肤病学 | 148篇 |
神经病学 | 1546篇 |
特种医学 | 546篇 |
外科学 | 2010篇 |
综合类 | 122篇 |
一般理论 | 22篇 |
预防医学 | 1137篇 |
眼科学 | 108篇 |
药学 | 823篇 |
中国医学 | 24篇 |
肿瘤学 | 597篇 |
出版年
2023年 | 62篇 |
2022年 | 90篇 |
2021年 | 245篇 |
2020年 | 163篇 |
2019年 | 271篇 |
2018年 | 309篇 |
2017年 | 209篇 |
2016年 | 252篇 |
2015年 | 240篇 |
2014年 | 427篇 |
2013年 | 586篇 |
2012年 | 902篇 |
2011年 | 952篇 |
2010年 | 528篇 |
2009年 | 484篇 |
2008年 | 831篇 |
2007年 | 797篇 |
2006年 | 782篇 |
2005年 | 825篇 |
2004年 | 752篇 |
2003年 | 716篇 |
2002年 | 651篇 |
2001年 | 99篇 |
2000年 | 67篇 |
1999年 | 89篇 |
1998年 | 140篇 |
1997年 | 102篇 |
1996年 | 104篇 |
1995年 | 90篇 |
1994年 | 71篇 |
1993年 | 54篇 |
1992年 | 58篇 |
1991年 | 45篇 |
1990年 | 36篇 |
1989年 | 39篇 |
1988年 | 57篇 |
1987年 | 40篇 |
1986年 | 36篇 |
1985年 | 29篇 |
1984年 | 44篇 |
1983年 | 45篇 |
1982年 | 47篇 |
1981年 | 33篇 |
1980年 | 48篇 |
1979年 | 26篇 |
1978年 | 20篇 |
1977年 | 19篇 |
1976年 | 21篇 |
1972年 | 14篇 |
1971年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
73.
Grossman D Fernandez L Hopkins K Amastae J Garcia SG Potter JE 《Obstetrics and gynecology》2008,112(3):572-578
OBJECTIVE: To estimate how well a convenience sample of women from the general population could self-screen for contraindications to combined oral contraceptives using a medical checklist. METHODS: Women 18-49 years old (N=1,271) were recruited at two shopping malls and a flea market in El Paso, Texas, and asked first whether they thought birth control pills were medically safe for them. They then used a checklist to determine the presence of level 3 or 4 contraindications to combined oral contraceptives according to the World Health Organization Medical Eligibility Criteria. The women then were interviewed by a blinded nurse practitioner, who also measured blood pressure. RESULTS: The sensitivity of the unaided self-screen to detect true contraindications was 56.2% (95% confidence interval [CI] 51.7-60.6%), and specificity was 57.6% (95% CI 54.0-61.1%). The sensitivity of the checklist to detect true contraindications was 83.2% (95% CI 79.5-86.3%), and specificity was 88.8% (95% CI 86.3-90.9%). Using the checklist, 6.6% (95% CI 5.2-8.0%) of women incorrectly thought they were eligible for use when, in fact, they were contraindicated, largely because of unrecognized hypertension. Seven percent (95% CI 5.4-8.2%) of women incorrectly thought they were contraindicated when they truly were not, primarily because of misclassification of migraine headaches. In regression analysis, younger women, more educated women, and Spanish speakers were significantly more likely to correctly self-screen (P<.05). CONCLUSION: Self-screening for contraindications to oral contraceptives using a medical checklist is relatively accurate. Unaided screening is inaccurate and reflects common misperceptions about the safety of oral contraceptives. Over-the-counter provision of this method likely would be safe, especially for younger women and if independent blood pressure screening were encouraged. 相似文献
74.
Localization of porcine seminal plasma (PSP) proteins in the boar reproductive tract and spermatozoa
Spermadhesins are proteins containing a characteristic CUB domain, originally isolated from seminal plasma and ejaculated spermatozoa in domestic animals. Boar spermadhesins are multifunctional proteins exhibiting ligand-binding abilities with various endogenous ligands present in the male and female reproductive tracts and may play a role in the reproduction process. Porcine spermadhesins (AQN, AWN, PSP protein families) are secreted mainly by the seminal vesicles, but their mRNAs have been found also in the cauda epididymis and prostate. Unlike AQN and AWN spermadhesins, localization of porcine seminal plasma (PSP) proteins in the boar reproductive tract has not been completely resolved. This work has focused on PSP protein expression and localization in the boar reproductive organs and on spermatozoa. Using specific rabbit polyclonal antibodies (anti-PSP I and anti-PSP II), PSP I and PSP II proteins were immunodetected in tissue extracts and in secretory tissues of cauda epididymis, prostate, seminal vesicles and Cowper's glands on the blots and by an indirect immunofluorescence technique, respectively. Moreover, the ability of PSP proteins to bind to epididymal spermatozoa indicated their presence on cauda epididymal and ejaculated spermatozoa. Porcine seminal plasma proteins bind to the sperm surface at ejaculation and may modulate several aspects of sperm activity during reproduction. PSP proteins are produced not only by seminal vesicles and prostate, but also by epididymis. However, their prospective role in sperm epididymal maturation is not clear. Further characterization of seminal plasma protein forms expressed in the individual reproductive organs will help to understand their subsequent role in the reproduction process. 相似文献
75.
76.
77.
Agustina Heredia-Martinez Guillermo Rosa-Diez Jorge R. Ferraris Anna-Karin Sohlenius-Sternbeck Carina Nihlen Annika Olsson Jon O. Lundberg Eddie Weitzberg Mattias Carlstrm Rafael T. Krmar 《Nutrients》2022,14(12)
Nitric oxide (NO) contributes to maintaining normal cardiovascular and renal function. This bioactive signalling molecule is generally formed enzymatically by NO synthase in the vascular endothelium. NO bioactivity can also be attributed to dietary intake of inorganic nitrate, which is abundant in our diet, especially in green leafy vegetables and beets. Ingested nitrate is reduced to nitrite by oral commensal bacteria and further to NO systemically. Previous studies have shown that dialysis, by means of removing nitrate and nitrite from the body, can reduce NO bioactivity. Hence, dietary intervention approaches aimed to boost the nitrate–nitrite–NO pathway may be of benefit in dialysis patients. The purpose of this study was to examine the kinetics of plasma nitrate and nitrite after a single intake of nitrate-rich concentrated beetroot juice (BJ) in adult hemodialysis (HD) patients and in age-matched healthy volunteers (HV). Eight HD patients and seven HV participated in this single center, randomized, single-blind, placebo-controlled, crossover study. Each participant received a sequential single administration of active BJ (70 mL, 400 mg nitrate) and placebo BJ (70 mL, 0 mg nitrate) in a random order separated by a washout period of seven days. For the kinetic analysis, blood samples were collected at different time-points before and up to 44 h after BJ intake. Compared with placebo, active BJ significantly increased plasma nitrate and nitrite levels both in HD patients and HV. The area under the curve and the maximal concentration of plasma nitrate, but not of nitrite, were significantly higher in HD patients as compared with HV. In both groups, active BJ ingestion did not affect blood pressure or plasma potassium levels. Both BJs were well tolerated in all participants with no adverse events reported. Our data provide useful information in planning dietary nitrate supplementation efficacy studies in patients with reduced NO bioactivity. 相似文献
78.
Vladimir Mgevand Jon A Lutz Gregor J Kocher Philippe Dumont 《Interactive Cardiovascular and Thoracic Surgery》2022,35(1)
We report the case of a female patient with an obstructing well-differentiated neuroendocrine tumour in the apical segment of the completely atelectatic right lower lobe. Bronchoscopic debulking of the tumour lead to re-ventilation of the remaining lobe, allowing to perform a lung-sparing bronchoplastic resection of the affected segment by uniportal video-assisted thoracic surgery. 相似文献
79.
Tom Jefferson Carl J. Heneghan Elizabeth Spencer Jon Brassey Annette Plüddemann Igho Onakpoya David Evans John Conly 《Viruses》2022,14(8)
Systematic reviews of 591 primary studies of the modes of transmission for SARS-CoV-2 show significant methodological shortcomings and heterogeneity in the design, conduct, testing, and reporting of SARS-CoV-2 transmission. While this is partly understandable at the outset of a pandemic, evidence rules of proof for assessing the transmission of this virus are needed for present and future pandemics of viral respiratory pathogens. We review the history of causality assessment related to microbial etiologies with a focus on respiratory viruses and suggest a hierarchy of evidence to integrate clinical, epidemiologic, molecular, and laboratory perspectives on transmission. The hierarchy, if applied to future studies, should narrow the uncertainty over the twin concepts of causality and transmission of human respiratory viruses. We attempt to address the translational gap between the current research evidence and the assessment of causality in the transmission of respiratory viruses with a focus on SARS-CoV-2. Experimentation, consistency, and independent replication of research alongside our proposed framework provide a chain of evidence that can reduce the uncertainty over the transmission of respiratory viruses and increase the level of confidence in specific modes of transmission, informing the measures that should be undertaken to prevent transmission. 相似文献
80.
Open ring enhancement is considered highly specific for atypical demyelination. In this report we present a patient with a history of headache, ataxia and sensory disturbances in the lower extremities. A cranial MRI scan showed a large frontal lesion with mass effect, midline shift and with open ring enhancement. These findings are characteristics of tumefactive multiple sclerosis. Such lesions can be confused with neoplasms and abscesses. Open ring enhancement may help in differentiating atypical demyelination from a neoplasm or an abscess. 相似文献