全文获取类型
收费全文 | 1853篇 |
免费 | 97篇 |
国内免费 | 7篇 |
专业分类
耳鼻咽喉 | 11篇 |
儿科学 | 88篇 |
妇产科学 | 21篇 |
基础医学 | 181篇 |
口腔科学 | 42篇 |
临床医学 | 118篇 |
内科学 | 373篇 |
皮肤病学 | 60篇 |
神经病学 | 102篇 |
特种医学 | 39篇 |
外科学 | 317篇 |
综合类 | 60篇 |
一般理论 | 11篇 |
预防医学 | 100篇 |
眼科学 | 124篇 |
药学 | 190篇 |
中国医学 | 8篇 |
肿瘤学 | 112篇 |
出版年
2023年 | 21篇 |
2022年 | 72篇 |
2021年 | 157篇 |
2020年 | 77篇 |
2019年 | 104篇 |
2018年 | 98篇 |
2017年 | 70篇 |
2016年 | 78篇 |
2015年 | 85篇 |
2014年 | 125篇 |
2013年 | 126篇 |
2012年 | 167篇 |
2011年 | 137篇 |
2010年 | 76篇 |
2009年 | 61篇 |
2008年 | 79篇 |
2007年 | 60篇 |
2006年 | 40篇 |
2005年 | 44篇 |
2004年 | 16篇 |
2003年 | 24篇 |
2002年 | 29篇 |
2001年 | 23篇 |
2000年 | 22篇 |
1999年 | 14篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 4篇 |
1992年 | 15篇 |
1991年 | 15篇 |
1990年 | 19篇 |
1989年 | 10篇 |
1988年 | 12篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1982年 | 2篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1975年 | 4篇 |
1972年 | 3篇 |
1966年 | 5篇 |
1965年 | 3篇 |
排序方式: 共有1957条查询结果,搜索用时 0 毫秒
61.
Nazima Sultana Prasanta K. Raul Diganta Goswami Dipankar Das Saidul Islam Varun Tyagi Bodhaditya Das Hemanta K. Gogoi Pronobesh Chattopadhyay Pakalapati S. Raju 《RSC advances》2020,10(16):9356
Background: Vector-borne diseases such as malaria, dengue, yellow fever, encephalitis and filariasis are considered serious human health concerns in the field of medical entomology. Controlling the population of mosquito vectors is one of the best strategies for combating such vector-borne diseases. However, the use of synthetic insecticides for longer periods of time increases mosquito resistance to the insecticides. Recently, the search for new environmentally friendly and efficient insecticides has attracted major attention globally. With the evolution of material sciences, researchers have reported the effective control of such diseases using various sustainable resources. The present investigation demonstrates a potent on-site biolarvicidal agent against different mosquito vectors such as Aedes albopictus, Anopheles stephensi and Culex quinquefasciatus. Methods: Stable and photo-induced colloidal silver nanoparticles were generated via the surface functionalization of the root extract of Cyprus rotundas. Characterizations of the nanoparticles were performed using assorted techniques, such as UV-visible spectroscopy, FTIR spectroscopy, DLS and HRTEM. The bioefficacy of the synthesized nanoparticles was investigated against different species of mosquito larvae through the evaluation of their life history trait studies, fecundity and hatchability rate of the treated larvae. Histopathological and polymerase chain reaction-random amplified polymorphic DNA (RAPD) analyses of the treated larvae were also examined to establish the cellular damage. Results: The synthesized nanoparticles showed remarkable larvicidal activity against mosquito larvae in a very low concentration range (0.001–1.00) mg L−1. The histopathological study confirmed that the present nanoparticles could easily enter the cuticle membrane of mosquito larvae and subsequently obliterate their complete intestinal system. Furthermore, RAPD analysis of the treated larvae could assess the damage of the DNA banding pattern. Conclusion: The present work demonstrates a potent biolarvicidal agent using sustainable bioresources of the aqueous Cyprus rotundas root extract. The results showed that the synthesized nanoparticles were stable under different physiological conditions such as temperature and photo-induced oxidation. The effectiveness of these materials against mosquito larvae was quantified at very low dose concentrations. The present biolarvicidal agent can be considered as an environmentally benign material to control the mosquito vectors with an immense potential for on-site field applications.The present work demonstrates a potent and stable biolarvicidal agent using sustainable bioresources. The synthesized nanomaterials can control the mosquito vectors at a very low concentration range (0.01–1.00 mg L−1) for on-site field applications. 相似文献
62.
The green synthesis of copper nanoparticles (CuNPs) using a leaf extract from Jatropha curcas (JC) has been documented in our present research work. The existence of flavonoids, tannins, glycosides, and alkaloids was confirmed by the phytochemical analysis of the plant extract and these chemicals can be used as reducing, stabilizing and capping agents. After six months, the JC-CuNPs were found to be stable without any evidence of agglomeration. The JC-CuNPs were characterised by XRD, FT-IR, SEM, TEM and UV-vis spectrophotometry. The average particle and crystal sizes of the JC-CuNPs were found to be 10 ± 1 and 12 ± 1 nm, respectively. The SPR peaks were found at 266 and 337 nm, measured using electronic spectroscopy, and the calculated optical band gap was found to be 3.6 eV at 337 nm, indicating the semiconductor behaviour of the JC-CuNPs. JC-CuNPs have potential photocatalytic activity against methylene blue (MB) compared with other dyes in the presence of sunlight and the rate constant (k) value is 2.30 × 10−4 s−1. The JC-CuNPs also have a binding property with CT-DNA through an intercalation mode and the binding constant (Kb) is 1.024 × 102 M−1.The green synthesis of copper nanoparticles (CuNPs) using a leaf extract from Jatropha curcas (JC) has been documented in our present research work. 相似文献
63.
The phenomenon of tissue expansion is observed in nature all the time. The same properties of the human skin to stretch and expand and yield extra skin if placed under continuous stress over a prolonged period of time has been utilised for reconstructive purposes with the help of a silicon balloon inserted under the skin and progressively filled with saline. The technique of tissue expansion is now more than three decades old and has been a value addition to our armamentarium in reconstructive surgery in all parts of the body. However, it still requires careful patient selection, meticulous planning and faultless execution to successfully carry out the process, which usually lasts for more than 8-12 weeks and involves two sittings of surgery. Any compromise in this process can lead to unfavourable results and complications, some minor, which allow continuance of the process to attain the expected goal and others major, which force abandonment of the process without reaching the expected goal. This article seeks to highlight the intricacies of the concept of tissue expansion, the technique related to flawless execution of the process and likely complications with emphasis on their management. We also present our results from a personal series of 138 patients operated over a period of 18 years between 1994 and 2012.KEY WORDS: Complications, tissue expansion, unfavourable results 相似文献
64.
Yair Lotan Aditya Bagrodia Niccolo Passoni Varun Rachakonda Payal Kapur Yull Arriaga Christian Bolenz Vitaly Margulis Ganesh V. Raj Arthur I. Sagalowsky Shahrokh F. Shariat 《European urology》2013
Background
Retrospective studies demonstrated that cell cycle–related and proliferation biomarkers add information to standard pathologic tumor features after radical cystectomy (RC). There are no prospective studies validating the clinical utility of markers in bladder cancer.Objective
To prospectively determine whether a panel of biomarkers could identify patients with urothelial carcinoma of the bladder (UCB) who were likely to experience disease recurrence or mortality.Design, setting, and participants
Between January 2007 and January 2012, every patient with high-grade bladder cancer, including 216 patients treated with RC and lymphadenectomy, underwent immunohistochemical staining for tumor protein p53 (Tp53); cyclin-dependent kinase inhibitor 1A (p21, Cip1) (CDKN1A); cyclin-dependent kinase inhibitor 1B (p27, Kip1); antigen identified by monoclonal antibody Ki-67 (MKI67); and cyclin E1.Intervention
Every patient underwent RC and lymphadenectomy, and marker staining.Outcome measurements and statistical analysis
Cox regression analyses tested the ability of the number of altered biomarkers to predict recurrence or cancer-specific mortality (CSM).Results and limitations
Pathologic stage among the study population was pT0 (5%), pT1 (35%), pT2 (19%), pT3 (29%), and pT4 (13%); lymphovascular invasion (LVI) was seen in 34%. The median number of removed lymph nodes was 23, and 60 patients had lymph node involvement (LNI). Median follow-up was 20 mo. Expression of p53, p21, p27, cyclin E1, and Ki-67 were altered in 54%, 26%, 46%, 15%, and 75% patients, respectively. In univariable analyses, pT stage, LNI, LVI, perioperative chemotherapy (CTx), margin status, and number of altered biomarkers predicted disease recurrence. In a multivariable model adjusting for pathologic stage, margins, LNI, and adjuvant CTx, only LVI and number of altered biomarkers were independent predictors of recurrence and CSM. The concordance index of a baseline model predicting CSM (including pathologic stage, margins, LVI, LNI, and adjuvant CTx) was 80% and improved to 83% with addition of the number of altered markers.Conclusions
Molecular markers improve the prediction of recurrence and CSM after RC. They may identify patients who might benefit from additional treatments and closer surveillance after cystectomy. 相似文献65.
E. Alçin A. Sahu S. Ramaswamy E. D. Hutz K. L. Keen E. Terasawa C. L. Bethea T. M. Plant 《Journal of neuroendocrinology》2013,25(5):488-496
Tonic gonadotrophin secretion throughout the menstrual cycle is regulated by the negative‐feedback actions of ovarian oestradiol (E2) and progesterone. Although kisspeptin neurones in the arcuate nucleus (ARC) of the hypothalamus appear to play a major role in mediating these feedback actions of the steroids in nonprimate species, this issue has been less well studied in the monkey. In the present study, we used immunohistochemistry and in situ hybridisation to examine kisspeptin and KISS1 expression, respectively, in the mediobasal hypothalamus (MBH) of adult ovariectomised (OVX) rhesus monkeys. We also examined kisspeptin expression in the MBH of ovarian intact females, and the effect of E2, progesterone and E2 + progesterone replacement on KISS1 expression in OVX animals. Kisspeptin or KISS1 expressing neurones and pronounced kisspeptin fibres were readily identified throughout the ARC of ovariectomised monkeys but, on the other hand, in intact animals, kisspeptin cell bodies were small in size and number and only fine fibres were observed. Replacement of OVX monkeys with physiological levels of E2, either alone or with luteal phase levels of progesterone, abolished KISS1 expression in the ARC. Interestingly, progesterone replacement alone for 14 days also resulted in a significant down‐regulation of KISS1 expression. These findings support the view that, in primates, as in rodents and sheep, kisspeptin signalling in ARC neurones appears to play an important role in mediating the negative‐feedback action of E2 on gonadotrophin secretion, and also indicate the need to study further their regulation by progesterone. 相似文献
66.
Currently, considerable efforts have been devoted to the detection and quantification of hazardous multi-analytes using a single probe. Herein, we have developed a simple, environment-friendly colourimetric sensor for the sensitive, selective and rapid detection of Ni2+ and Cu2+ ions using a simple organic Schiff base ligand L in methanol–Tris–HCl buffer (1 : 1 v/v, 10 mM, pH = 7.2). The probe L exhibited a binding-induced colour change from colourless to yellow and fluorescence quenching in the presence of both Ni2+ and Cu2+ ions. The interactions between L and the respective metal ions were studied by Job''s plot, electrospray ionisation-mass spectrometry (ESI-MS), Fourier-transform infrared spectroscopy (FT-IR), density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations. The limit of detection (LOD) of L towards Ni2+ and Cu2+ was calculated to be 7.4 × 10−7 M and 4.9 × 10−7 M, respectively. Furthermore, the L–Cu2+ complex could be used as a new cascade fluorescent-colourimetric sensor to detect CN− ions with a very low level of detection (40 nM). Additionally, L could operate in a wide pH range, and thus was successfully applied for the detection and quantification of Ni2+ and Cu2+ in environmental samples, and for building OR- and IMPLICATION-type logic gates.A novel colorimetric chemosensor L has been developed for the detection of Ni2+ and Cu2+ ions. The obtained L–Cu2+ complex can be used as a new cascade fluorescent-colorimetric sensor for the nanomolar detection of CN− ions. This chemosensor has practical application. 相似文献
67.
Jina Pakpoor Micheal Raad Andrew Harris Varun Puvanesarajah Joseph K. Canner Rohini Nadgir Amit Jain 《Journal of the American College of Radiology》2019,16(11):1522-1527
ObjectiveHigh-value care guidelines from multiple medical societies recommend against imaging for the initial evaluation of low back pain in the absence of red flag symptoms. We aimed to determine the current temporal and geographic landscape of imaging ordering patterns for this indication among US primary care providers.MethodsUsing a national commercial insurance claims database, we identified patients between 18 and 64 years old who presented to a primary care provider for an initial evaluation of low back pain between 2011 and 2016. Patients were identified via International Classification of Diseases codes, and the use of diagnostic imaging was identified by Current Procedural Terminology codes. Geographic regions were based on the location of patient residence.ResultsOverall, 627,118 encounters met inclusion criteria. Imaging acquisitions increased over time, from 14% of encounters in 2011 to 16% in 2016 (P < .01). Radiographs represented 96% of ordered imaging, CT 2%, and MRI 3%. The likelihood of having any imaging for low back pain varied significantly by US census region and by US state (P < .01). The greatest use of imaging was in the Midwest (13.9%) and the South (18.5%), and lowest in the Northeast and West (6.2% and 13.6%).DiscussionImaging utilization for the initial evaluation of low back pain by primary care providers has increased on a national level from 2011 to 2016, largely represented by radiographs. Significant regional variation also exists. Encouragingly, the use of advanced imaging has remained at a low level in the primary care setting (<1.0%). 相似文献
68.
69.
70.
In this study we show the effect of anti-sulfatide (RmAb) antibodies and inflammatory cytokines, TNF-alpha and IFN-gamma in inducing myelin basic protein (MBP) degradation in myelin isolated from control wild type (WT) and glia maturation factor (GMF)-deficient (GMF-KO) mice. GMF was not detected in isolated myelin from WT and GMF-KO mice although it is present in brains of WT mice. Our results show that calcium-dependent neutral protease activity caused significantly elevated degradation of 18.5 and/or 17.5kDa isoforms of MBP in WT myelin treated with RmAb or IFN-gamma. In contrast, MBP degradation in isolated myelin from GMF-KO mice remained unaffected following treatment with RmAb, IFN-gamma, or GM-CSF. Neither the 14kDa isoform of MBP nor proteolipid protein (PLP) showed an elevated degradation compared to controls. A virtual absence of GM-CSF, TNF-alpha and IFN-gamma in GMF-KO brain compared to WT was also evident when the animals were challenged with MOG 35-55. Additionally, the myelin from GMF-KO mice showed difference in distribution of myelin oligodendrocyte glycoprotein (MOG) and beta-tubulin in a sucrose density gradient myelin-axolemmal fractions compared to WT. Taken together, our data suggests a role for GMF in the biochemical organization of myelin and thereby its effect on MBP degradation induced by RmAb and IFN-gamma. 相似文献