全文获取类型
收费全文 | 6577篇 |
免费 | 490篇 |
国内免费 | 24篇 |
专业分类
耳鼻咽喉 | 82篇 |
儿科学 | 149篇 |
妇产科学 | 100篇 |
基础医学 | 943篇 |
口腔科学 | 164篇 |
临床医学 | 638篇 |
内科学 | 1551篇 |
皮肤病学 | 85篇 |
神经病学 | 657篇 |
特种医学 | 261篇 |
外科学 | 1023篇 |
综合类 | 59篇 |
一般理论 | 5篇 |
预防医学 | 366篇 |
眼科学 | 131篇 |
药学 | 334篇 |
中国医学 | 8篇 |
肿瘤学 | 535篇 |
出版年
2023年 | 60篇 |
2022年 | 101篇 |
2021年 | 187篇 |
2020年 | 134篇 |
2019年 | 167篇 |
2018年 | 199篇 |
2017年 | 148篇 |
2016年 | 163篇 |
2015年 | 197篇 |
2014年 | 264篇 |
2013年 | 330篇 |
2012年 | 524篇 |
2011年 | 503篇 |
2010年 | 325篇 |
2009年 | 259篇 |
2008年 | 467篇 |
2007年 | 445篇 |
2006年 | 391篇 |
2005年 | 384篇 |
2004年 | 314篇 |
2003年 | 308篇 |
2002年 | 268篇 |
2001年 | 56篇 |
2000年 | 40篇 |
1999年 | 55篇 |
1998年 | 49篇 |
1997年 | 37篇 |
1996年 | 40篇 |
1995年 | 45篇 |
1994年 | 30篇 |
1993年 | 41篇 |
1992年 | 32篇 |
1991年 | 32篇 |
1990年 | 29篇 |
1989年 | 32篇 |
1988年 | 39篇 |
1987年 | 34篇 |
1986年 | 25篇 |
1985年 | 22篇 |
1984年 | 28篇 |
1983年 | 27篇 |
1982年 | 28篇 |
1981年 | 26篇 |
1980年 | 13篇 |
1979年 | 21篇 |
1978年 | 16篇 |
1975年 | 12篇 |
1974年 | 17篇 |
1973年 | 13篇 |
1972年 | 13篇 |
排序方式: 共有7091条查询结果,搜索用时 15 毫秒
31.
Seropositivity for and Intestinal Colonization with Entamoeba histolytica and Entamoeba dispar in Individuals in Northeastern Brazil
下载免费PDF全文
![点击此处可从《Journal of clinical microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Lucia L. Braga Yacy Mendonca Clece A. Paiva Andrea Sales Andre L. M. Cavalcante Barbara J. Mann 《Journal of clinical microbiology》1998,36(10):3044-3045
In a slum community in northeastern Brazil 20% of a sample population was colonized with Entamoeba histolytica or Entamoeba dispar and 10.6% was colonized with E. histolytica alone. No correlation between seropositivity for anti-GalNAc lectin antibody and colonization was found. These results suggest that colonization does not necessarily produce immunity to reinfection. 相似文献
32.
33.
Effects of Orally Administered Epidermal Growth Factor on Enteropathogenic Escherichia coli Infection in Rabbits 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《Infection and immunity》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Andre Buret Merle E. Olson D. Grant Gall James A. Hardin 《Infection and immunity》1998,66(10):4917-4923
The increased intestinal absorption induced by epidermal growth factor (EGF) is associated with diffuse lengthening of brush border microvilli. The aim of this study was to examine the in vivo effects of oral administration of EGF during infection with enteropathogenic Escherichia coli. New Zealand White rabbits (4 weeks old) received orogastric EGF daily starting 3 days prior to infection with enteropathogenic E. coli RDEC-1 and were compared with sham-treated infected animals and uninfected controls. Weight gain, food intake, fecal E. coli, and stool consistency were assessed daily. On day 10, segments of jejunum, ileum, proximal, and distal colon were assessed for gram-negative bacterial colonization, disaccharidase activities, and epithelial ultrastructure. Effects of EGF on E. coli RDEC-1 proliferation were studied in vitro. E. coli RDEC-1 caused diarrhea and reduced weight gain. Seven days postinfection, the small and large intestines were colonized with numerous bacteria, brush border microvilli were disrupted, and maltase and sucrase activities were significantly reduced in the jejunum. Daily treatment with EGF prevented the occurrence of diarrhea and reduction of weight gain. These effects were associated with significant inhibition of E. coli colonization in the small and large intestine, improved jejunal maltase and sucrase activities and reduced microvillous injury. EGF did not affect the proliferation of E. coli in vitro. The findings suggest that EGF protects the gastrointestinal tract against colonization by enteropathogenic E. coli. 相似文献
34.
Nano-C60 cytotoxicity is due to lipid peroxidation 总被引:20,自引:0,他引:20
This study examines the biological effects of water-soluble fullerene aggregates in an effort to evaluate the fundamental mechanisms that contribute to the cytotoxicity of a classic engineered nanomaterial. For this work we used a water-soluble fullerene species, nano-C60, a fullerene aggregate that readily forms when pristine C60 is added to water. Nano-C60 was cytotoxic to human dermal fibroblasts, human liver carcinoma cells (HepG2), and neuronal human astrocytes at doses 50 ppb (LC50=2–50 ppb, depending on cell type) after 48 h exposure. This water-soluble nano-C60 colloidal suspension disrupts normal cellular function through lipid peroxidation; reactive oxygen species are responsible for the membrane damage. Cellular viability was determined through live/dead staining and LDH release. DNA concentration and mitochondrial activity were not affected by the nano-C60 inoculations to cells in culture. The integrity of cellular membrane was examined by monitoring the peroxy-radicals on the lipid bilayer. Subsequently, glutathione production was measured to assess the cell's reaction to membrane oxidation. The damage to cell membranes was observed both with chemical assays, and confirmed physically by visualizing membrane permeability with high molecular weight dyes. With the addition of an antioxidant, l-ascorbic acid, the oxidative damage and resultant toxicity of nano-C60 was completely prevented. 相似文献
35.
Memory T lymphocytes generated by Mycobacterium bovis BCG vaccination reside within a CD4 CD44lo CD62 ligand(hi) population
下载免费PDF全文
![点击此处可从《Infection and immunity》网站下载免费的PDF全文](/ch/ext_images/free.gif)
In the lungs of mice vaccinated with Mycobacterium bovis BCG, there was an accumulation of CD4 cells expressing the activated effector phenotype CD44hi CD62 ligandlo) (CD62Llo) which were capable of secreting gamma interferon. Upon cell transfer, however, cells expressing a resting/na?ve phenotype (CD44lo CD62Lhi) were capable of protecting the recipients from a virulent challenge infection, suggesting the emergence of T-cell memory from within this subset. 相似文献
36.
Lura Brianna Caddle Jeremy L. Grant Jin Szatkiewicz Johann van Hase Bobbi-Jo Shirley Joerg Bewersdorf Christoph Cremer Alain Arneodo Andre Khalil Kevin D. Mills 《Chromosome research》2007,15(8):1061-1073
Radiation exposure is an occupational hazard for military personnel, some health care professionals, airport security screeners,
and medical patients, with some individuals at risk for acute, high-dose exposures. Therefore, the biological effects of radiation,
especially the potential for chromosome damage, are major occupational and health concerns. However, the biophysical mechanisms
of chromosome instability subsequent to radiation-induced DNA damage are poorly understood. It is clear that interphase chromosomes
occupy discrete structural and functional subnuclear domains, termed chromosome territories (CT), which may be organized into
‘neighborhoods’ comprising groups of specific CTs. We directly evaluated the relationship between chromosome positioning,
neighborhood composition, and translocation partner choice in primary lymphocytes, using a cell-based system in which we could
induce multiple, concentrated DNA breaks via high-dose irradiation. We critically evaluated mis-rejoining profiles and tested
whether breaks occurring nearby were more likely to fuse than breaks occurring at a distance. We show that CT neighborhoods
comprise heterologous chromosomes, within which inter-CT distances directly relate to translocation partner choice. These
findings demonstrate that interphase chromosome arrangement is a principal factor in genomic instability outcomes in primary
lymphocytes, providing a structural context for understanding the biological effects of radiation exposure, and the molecular
etiology of tumor-specific translocation patterns. 相似文献
37.
Bogers JJ Chatterjee S Jacobs W Fallon PG Dunne DW Langermans JA Deelder AM Thomas AW Van Marck EA 《Virchows Archiv : an international journal of pathology》2004,445(3):285-291
Adults and children have differences in their susceptibility to schistosomiasis. Whether this age-dependent innate susceptibility influences parasite-caused granulomogenesis is difficult to assess in humans. Therefore, we exposed juvenile and adult female rhesus monkeys to primary infection with Schistosoma mansoni. Hepatic and intestinal granuloma formation was observed in both pre-pubescent and adult monkeys. Two distinct stages of granulomas were discerned, the exudative and the productive stage. In the intestine, more granulomas were generated in the colon than in the ileum. In contrast to the adult animals, the juvenile rhesus monkeys had higher numbers of colonic granulomas, these higher numbers being predominantly of the more advanced productive stage. Juvenile animals had a statistically non-significant increased worm burden. These results suggest that juvenile rhesus monkeys have a significantly more intense and advanced colonic response towards entrapped S. mansoni eggs after primary schistosome infections and, thereby, are more susceptible to parasite infection.Research protocols involving non-human primates received ethical clearance by the Institutional Animal Care and Use Committee of the Biomedical Primate Research Centre (Rijswijk, The Netherlands), according to Dutch Law. 相似文献
38.
Verhell Coleta; de Graaff Graaff Esther; Bakker Cathy E.; Willemsen Rob; Willems Patric J.; Meijer Nicolle; Galjaard Hans; Reuser Arnold J.J.; Oostra Ben A.; Hoogeveen Andre 《Human molecular genetics》1995,4(5):895-901
FMR1 protein expression was studied in different tissues. Inhuman, monkey and murine tissues, high molecular mass FMR1 proteins(6780 kDa) are found, as shown in lymphobiastoid celiiines. The identity of these proteins was confirmed by theirabsence in tissues from patients with the fragile X syndromeand a FMR1 knock-out mouse. An IIe367Asn substitution in theFMR1 protein did not aiter the transiation, processing and localizationof FMR1 proteins in lymphoblastoid cells from a patient carryingthis mutation. All the high molecular mass FMR1 proteins isolatedfrom normal lymphoblastoid cells and cells from the patientwith the IIe367Asn substitution were able to bind RNA. However,the FMR1 proteins of the patient had reduced affinity for RNAbinding at high salt concentrations. In some human, monkey andmurine tissues low molecular mass FMR1 proteins (3941kDa) were found, which had the same N terminus as the 6790kDa isoforms, but differ in their C terminus and are thereforemost likely the result of carboxy-terminal proteolytic cleavage.These low molecular mass FMR1 proteins did not bind RNA, incontrast with the high molecular mass FMR1 proteins. The significanceof these low molecular mass proteins remains to be studied. 相似文献
39.
Andre Tehe Chantal Maurice Debra L Hanson Marie Y Borget Nadine Abiola Matthieu Maran Daniel Yavo Zuzana Tomasik Jürg B?ni J?rg Schüpbach John N Nkengasong 《Journal of clinical virology》2006,37(3):199-205
BACKGROUND: Quantification of HIV-1 RNA remains difficult to implement in Africa. Simple and inexpensive tests for antiretroviral treatment (ART) monitoring are needed. OBJECTIVE: To evaluate an HIV-1 p24 ELISA, which combines efficient virus disruption, heat-denaturation and signal amplification, in a West African setting. STUDY DESIGN: Eighty-six HIV-1 infected patients from Abidjan, C?te d'Ivoire, were tested for p24, HIV-1 RNA, and CD4+ count at baseline, and twice within 8 months after ART initiation. RESULTS: All patients responded to ART with a minimal HIV-1 RNA drop of 0.5 log(10) at first follow-up. Forty-one (47.7%) then rebounded >0.5 log(10) or persisted above 1000 copies/mL by week 24. The predicted baseline concentration of p24 corresponding to 100,000 copies/mL of HIV-1 RNA, above which ART is recommended, was 4546 fg/mL (95% confidence interval 3148-6566). A prediction model of virologic failure, occurring after an initial response to ART, correctly classified 84% of patients using baseline p24, p24 change on therapy, and achievement of undetectable p24 as explanatory variables. The model and further bootstrap evaluation suggested a good ability to discriminate between sustained or failing virologic response to ART. CONCLUSION: HIV-1 p24 and RNA based-ART monitoring in a low-resource country dominated by HIV-1 CRF02 AG appeared comparable. 相似文献
40.
Psychological test scores of 13 identical and six fraternal pairs of twins aged 77–88 years were analyzed. These individuals are the survivors of a group of senescent twins studied earlier. The identical twins remained more similar than the fraternal ones, and there was a remarkable conservation of cognitive abilities in most individuals. Moreover, preservation of intelligence and longevity may be related. 相似文献