全文获取类型
收费全文 | 168644篇 |
免费 | 3612篇 |
国内免费 | 1775篇 |
专业分类
耳鼻咽喉 | 1682篇 |
儿科学 | 6246篇 |
妇产科学 | 2867篇 |
基础医学 | 21094篇 |
口腔科学 | 4288篇 |
临床医学 | 10983篇 |
内科学 | 32551篇 |
皮肤病学 | 3300篇 |
神经病学 | 10046篇 |
特种医学 | 3335篇 |
外国民族医学 | 2篇 |
外科学 | 26452篇 |
综合类 | 9921篇 |
现状与发展 | 1篇 |
一般理论 | 4篇 |
预防医学 | 8725篇 |
眼科学 | 3308篇 |
药学 | 17922篇 |
11篇 | |
中国医学 | 6217篇 |
肿瘤学 | 5076篇 |
出版年
2022年 | 1300篇 |
2021年 | 2442篇 |
2020年 | 1297篇 |
2019年 | 12771篇 |
2018年 | 12418篇 |
2017年 | 5665篇 |
2016年 | 1313篇 |
2015年 | 1334篇 |
2014年 | 2929篇 |
2013年 | 4692篇 |
2012年 | 2970篇 |
2011年 | 3095篇 |
2010年 | 2595篇 |
2009年 | 2445篇 |
2008年 | 2884篇 |
2007年 | 3885篇 |
2006年 | 4126篇 |
2005年 | 4003篇 |
2004年 | 3155篇 |
2003年 | 3236篇 |
2002年 | 3122篇 |
2001年 | 3109篇 |
2000年 | 3328篇 |
1999年 | 3001篇 |
1998年 | 3082篇 |
1997年 | 2437篇 |
1996年 | 2271篇 |
1995年 | 2635篇 |
1994年 | 2444篇 |
1993年 | 1920篇 |
1992年 | 1515篇 |
1991年 | 1501篇 |
1990年 | 1262篇 |
1989年 | 988篇 |
1988年 | 1030篇 |
1987年 | 1004篇 |
1986年 | 837篇 |
1985年 | 5417篇 |
1984年 | 7298篇 |
1983年 | 5840篇 |
1982年 | 6276篇 |
1981年 | 5726篇 |
1980年 | 4921篇 |
1979年 | 4975篇 |
1978年 | 4070篇 |
1977年 | 3057篇 |
1976年 | 3529篇 |
1975年 | 2740篇 |
1974年 | 2528篇 |
1973年 | 2231篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Pseudotypes of vesicular stomatitis virus with envelope antigens provided by murine mammary tumor virus. 总被引:12,自引:0,他引:12
Infection of two mouse mammary carcinoma cell lines with vesicular stomatitis virus (VSV) resulted in the formation of at least two types of particles containing the VSV genome but expressing different envelope characteristics (VSV pseudotypes). One of these VSV pseudotypes was infectious for a cell line derived from normal mouse mammary epithelial cells and mouse embryo cells but noninfectious for 3T3 cells, mink lung cells, and Vero cells. If mouse mammary tumor cells were treated with dexamethason some days prior to infection with VSV, the titer of this pseudotype was significantly increased. In contrast, the second pseudotype was infectious for mink cells, but not for the other cell lines tested, and the titer of this second pseudotype was unaffected by the presence of dexamethasone. The first pseudotype was found to be almost completely neutralized by anti-murine mammary tumor virus (MuMTV) serum whereas the second pseudotype was only partially neutralized at a higher antiserum concentration. Neither pseudotype showed the neutralization, host range, or interference properties of either ecotropic or xenotropic murine C-type viruses. These results suggest that the first pseudotype is VSV(MuMTV). The other pseudotype is less well defined but conceivably may represent a xenotropic MuMTV. In the course of these studies, a filterable agent was observed in GR mammary carcinoma cultures that reactivated the infectivity of VSV neutralized by antiserum. This agent was transmissible to mink cells. 相似文献
992.
The serum levels of IgE, IgG, IgA, and IgM of 27 American-born Filipino children 5 to 17 years of age were measured and found to be significantly higher than those of a control group of 24 Caucasian children of similar age distribution and attending the same general pediatric clinics. The geometric mean of serum IgE of the Filipinos was 227 U. per milliliter and of the Caucasians, 69 U. per milliliter (p < 0.01). The geometric means of other serum immunoglobulin levels of the Filipinos by comparison with the Caucasians were: IgG, 1,303 and 1,010 mg. per 100 ml. (p < 0.01); IgA, 195 and 120 mg. per 100 ml. (p < 0.001); and IgM, 141 and 92 mg. per 100 ml. (p < 0.02), respectively. The incidence of atopic disease was higher in the Filipino study group (48 per cent) than in the Caucasian control group (25 per cent); eczema was especially prevalent in the Filipino group. Elevated serum IgE levels were associated with atopic disease in both racial groups; however, there was no correlation between serum level of IgG, IgA, or IgM and atopy. 相似文献
993.
Limor Broday Craig A Hauser Irina Kolotuev Ze'ev Ronai 《Developmental dynamics》2007,236(11):3129-3136
The C. elegans hypodermis is a single epithelial cell layer separated from the musculature by a thin basement membrane on its basal surface. The hypodermis secretes the extracellular material of the cuticle from its apical surface. The regulation of cuticle synthesis and apical secretion is not well understood. UNC-95 is a component of the muscle dense bodies and M-lines, which are integrin-based adhesion complexes required for force transduction to the cuticle. Using gene expression profiling and in vivo assays, we show that, in unc-95 mutant worms, there is an increase in expression levels of a group of hypodermal and pharyngeal genes related to cuticle structure and molting. Moreover, the cuticle structure of unc-95 mutant adult is impaired. Our findings suggest that aberrant force transduction from the structurally impaired muscle attachments across the basement membrane to the underlying hypodermis elicits intercellular signaling that plays a role in regulating cuticle synthesis and patterning. 相似文献
994.
Clinicopathological significant and prognostic influence of cadherin-17 expression in gastric cancer 总被引:5,自引:0,他引:5
Ito R Oue N Yoshida K Kunimitsu K Nakayama H Nakachi K Yasui W 《Virchows Archiv : an international journal of pathology》2005,447(4):717-722
Cadherin-17 (CDH17), also called liver–intestine cadherin, is a structurally unique member of the cadherin superfamily. Our
serial analysis of gene expression demonstrated that CDH17 was one of the most up-regulated genes in advanced gastric carcinomas.
CDH17 expression is known to be regulated by Cdx2. In the present study, we examined the expression of CDH17 in primary gastric
carcinoma tissues by immunohistochemistry, and analyzed the correlation of CDH17 expression with clinicopathological characteristics
and patients prognosis. CDH17 expression was detected in 63/94 (67%) of gastric adenocarcinomas in addition to intestinal
metaplasia. The expression of CDH17 tended to be associated with intestinal type carcinoma, and carcinomas with CDH17 expression
was significantly more frequent in advanced stage cases (80%) than in early stage (53%). The prognosis of patients with positive
CDH17 expression was significantly poorer than that of the negative cases (P=0.0314). However, multivariate analysis revealed that CDH17 was not an independent prognostic factor. Six of seven cases
that showed positive expression of Cdx2 simultaneously expressed CDH17 protein. These results suggested that the expression
of CDH17 was characteristic of the advanced gastric carcinoma that is associated with poor prognosis. 相似文献
995.
OBJECTIVE: To examine, using direct observation methodology, differences in family functioning at mealtime between families of school-age children with cystic fibrosis (CF) and families of school-age children without a chronic illness. METHOD: Family functioning was rated using the McMaster Mealtime Interaction Coding System (MICS) during a videotaped dinner among 28 families of children with CF and 27 families of non-ill, age-matched peers. Families were rated on overall family functioning and on six dimensions of the MICS: task accomplishment, communication, affect management, interpersonal involvement, behavior control, and role allocation. RESULTS: Ratings for families of a child with CF were significantly lower than they were for comparison families on overall family functioning and on four of the six MICS dimensions: communication, affect management, interpersonal involvement, and behavioral control. Moreover, a significantly greater percentage of families of children with CF were rated in the unhealthy range on overall family functioning and on five of six MICS dimensions. There was no relationship between family functioning and child weight status for children with CF. CONCLUSIONS: The current study suggests that for families of school-age children with CF, the family system is negatively affected during mealtime. Dietary interventions need to address family-centered, as well as child-centered, interventions to help families manage challenges presented during the family meal. 相似文献
996.
Inhaled lodoxamide tromethamine in the treatment of perennial asthma: a double-blind placebo-controlled study 总被引:1,自引:0,他引:1
J S Mann P Clement A Q Sheridan I Soryal A J Fairfax S T Holgate 《The Journal of allergy and clinical immunology》1985,76(1):83-90
The efficacy of lodoxamide tromethamine in the treatment of asthma was studied in a 16-week double-blind, placebo-controlled study of 68 perennial allergic subjects with asthma. Patients received either lodoxamide tromethamine, 0.25 mg four times daily, or placebo, administered by metered-dose inhaler. Response to treatment was assessed by analyzing changes in asthma symptoms, inhaled bronchodilator requirements, and pulmonary function when compared to a 2-week baseline period. Patients treated with lodoxamide tromethamine demonstrated an improvement in daytime breathing difficulty, cough, sputum production, and sleep (p less than 0.01 to 0.05), but improvement was not significantly different from that demonstrated by placebo-treated patients. Patients from both treatment groups were able to reduce their inhaled bronchodilators (p less than 0.01), but again no significant difference was apparent between lodoxamide tromethamine and placebo treatment, nor were there any differences in peak expiratory flow rate or FEV1 between the two groups. Seven patients who received lodoxamide tromethamine withdrew because of a sensation of heat and gastrointestinal symptoms. Thus, although lodoxamide tromethamine possesses potent mast cell-stabilizing activity in vitro, we have failed to demonstrate any useful long-term effect in the treatment of mild allergic asthma. 相似文献
997.
Renate Wachner Christian Wittekind Sabine von Kleist 《Virchows Archiv : an international journal of pathology》1984,402(4):415-423
Summary One hundred and twenty seven cases of lung tumors were studied by the immunoperoxidase technique for the presence of CEA and-HCG. Twenty-nine of these tumors were additionally stained for keratin and SP1. CEA and SP1 could be demonstrated in 80% of the studied cases, while-HCG was found in only 9%. SP1 revealed an almost identical staining pattern to CEA and keratin was found only in squamous cell carcinomas. The tissue positivity of none of these three markers correlated with tumor size, lymphnodal involvement or histological type.This study was supported by Deutsche Stiftung für Krebsforschung - Dr. Mildred Scheel-Stiftung 相似文献
998.
HTLV type I (U. S. isolate) and ATLV (Japanese isolate) are the same species of human retrovirus 总被引:6,自引:0,他引:6
Two independent isolates of human leukemia virus, human T-cell leukemia virus (HTLV) and adult T-cell leukemia virus (ATLV), are shown to be the same by blotting analysis using gene-specific probes and restriction enzymes. Therefore, Japanese ATL virus and Caribbean HTLV type I, which are exogenous for human, have a common origin. 相似文献
999.
Seminoma and sarcoidosis do not seem to be associated diseases, judging from epidemiologic data. The presence of these two diseases in the patient whose case is reported may have been coincidental. It was observed, however, that when the testis tumor appeared in this patient, the longstanding sarcoid lesions significantly increased. The patient developed neutropenic enterocolitis after chemotherapy for a non-hematologic malignancy. 相似文献
1000.
Cell-free translation of tobacco vein mottling virus RNA 总被引:1,自引:0,他引:1
Tobacco vein mottling virus (TVMV), a member of the potyvirus group, was translated in a rabbit reticulocyte cell-free system. The RNA was approximately 5% as active as rabbit globin mRNA in directing protein synthesis. Translation was stimulated approximately 15% by the cap analog pppm7G, a phenomenon which has also been observed with uncapped viral RNAs. Treatment with NaIO4 and NaB(3H]4 under conditions which label the caps of globin and ovalbumin mRNA failed to produce labeled cap structures in TVMV RNA. Approximately 20 polypeptides, ranging from 20,000 to 100,000 daltons, were produced in the reticulocyte system programmed with TVMV RNA. The predominant species (P75) had a molecular weight of 75,000. The same major polypeptides were produced in the wheat germ system, but there was relatively greater synthesis of the smaller polypeptides. Incubation of the reticulocyte system in the presence of cycloheximide following an initial period of synthesis failed to cause breakdown of larger polypeptides into smaller polypeptides. Preincubation of TVMV RNA with the reticulocyte system before addition of labeled amino acids caused greater synthesis of the smaller polypeptides, suggesting that they are derived from fragments of the RNA produced during the incubation. Translation of TVMV RNA which had been bound to oligo(dT)-cellulose yielded nearly the same spectrum of polypeptides, but synthesis of polypeptides smaller than 52,000 daltons was reduced. At low ionic strength, only polypeptides of 52,000 daltons and smaller were synthesized. At high ionic strength, P75 was essentially the only product synthesized. Antibody to whole virus precipitated many of the polypeptides, including P75, suggesting that they contain the coat protein sequence. No polypeptide with the electrophoretic mobility of authentic coat protein, however, was precipitated. Comparison of partial proteolytic digests of P75 and authentic coat protein provided further evidence for sequence homology. 相似文献