全文获取类型
收费全文 | 2347213篇 |
免费 | 175088篇 |
国内免费 | 3322篇 |
专业分类
耳鼻咽喉 | 32057篇 |
儿科学 | 75904篇 |
妇产科学 | 62703篇 |
基础医学 | 348260篇 |
口腔科学 | 63628篇 |
临床医学 | 211401篇 |
内科学 | 457561篇 |
皮肤病学 | 51741篇 |
神经病学 | 185357篇 |
特种医学 | 88021篇 |
外国民族医学 | 489篇 |
外科学 | 353978篇 |
综合类 | 47516篇 |
现状与发展 | 12篇 |
一般理论 | 848篇 |
预防医学 | 182809篇 |
眼科学 | 54366篇 |
药学 | 175143篇 |
11篇 | |
中国医学 | 4575篇 |
肿瘤学 | 129243篇 |
出版年
2021年 | 19004篇 |
2019年 | 19566篇 |
2018年 | 27093篇 |
2017年 | 20375篇 |
2016年 | 22762篇 |
2015年 | 25659篇 |
2014年 | 36120篇 |
2013年 | 53980篇 |
2012年 | 74734篇 |
2011年 | 79452篇 |
2010年 | 47091篇 |
2009年 | 44580篇 |
2008年 | 74643篇 |
2007年 | 79531篇 |
2006年 | 80340篇 |
2005年 | 77834篇 |
2004年 | 74413篇 |
2003年 | 71742篇 |
2002年 | 69402篇 |
2001年 | 108763篇 |
2000年 | 111475篇 |
1999年 | 93523篇 |
1998年 | 26999篇 |
1997年 | 23664篇 |
1996年 | 24059篇 |
1995年 | 22724篇 |
1994年 | 20900篇 |
1993年 | 19715篇 |
1992年 | 72010篇 |
1991年 | 70076篇 |
1990年 | 68401篇 |
1989年 | 65677篇 |
1988年 | 60310篇 |
1987年 | 59130篇 |
1986年 | 55226篇 |
1985年 | 53011篇 |
1984年 | 39317篇 |
1983年 | 33400篇 |
1982年 | 19860篇 |
1979年 | 35869篇 |
1978年 | 25652篇 |
1977年 | 21235篇 |
1976年 | 20334篇 |
1975年 | 21820篇 |
1974年 | 26151篇 |
1973年 | 24802篇 |
1972年 | 23201篇 |
1971年 | 22039篇 |
1970年 | 20248篇 |
1969年 | 19316篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
972.
The B cell functional response following ligation of surface(s) lgM is dependent upon the differentiation stage of the populationstudied: cross-linking slgM promotes proliferation of restingtonsillar follicular mantle (FM) B lymphocytes but induces apoptosisin the susceptible Epstein- Barr virus genome-negative Burkittlymphoma (BL) cell line Ramos (Ramos-BL). This study investigateswhether phosphatidylinositol-3-kinase (Pl3-kinase), which hasbeen reported to be intimately involved in the regulation ofcellular growth, plays a role in the regulation of these sig-promoted B cell responses, and uses the selective and irreversibleinhibitor of Pl3-kinase activity, wortmannin (Wm). In Ramos-BLB cells, at 8 h post-treatment, Wm triggers a transient increasein apoptosis of 16 ± 6.9% with a concomitant cellularloss of 16 ± 6.1% from the G1 phase of cell cycle; [3H]thymidineincorporation also decreases by 33 ± 5.0%, from 37,274c.p.m. ± 10% to 25,127 c.p.m. ± 4.0%. Moreover,at 72 h culture, Wm inhibits anti-lgM-induced FM B lymphocytelevels of [3H]thymidine incorporation typically by 47% and triggers80% apoptosis from the G0G1 phase of cell cycle. Ramos-BL Bcells exhibit high basal levels of Pl3-kinase activity, as determinedby immunoprecipitation with antibody to the p85 regulatory subunitof Pl3-kinase and 32P incorporation into phosphatidylinositol,which is not significantly affected by anti-lgM stimulation;by contrast, anti-lgM stimulates significant Pl3-kinase activityover negligible basal levels in FM B lymphocytes. Pre-treatmentwith Wm inhibits Pl3-kinase activity in both cell types. Takentogether these data indicate that in Ramos-BL B cells slgM-triggeredgrowth arrest and apoptosis is Pl3- kinase independent, whereasPl3-kinase activity is critical for slgM-triggered mitogenesisof FM B lymphocytes. Thus Pl3-kinase plays a pivotal role inthe regulation of both normal and neoplastic B lymphocyte progressionthrough the cell cycle, such that if this Pl3-kinase-dependentpathway is inhibited these cells default to apoptosis. 相似文献
973.
Rik C. Schoemaker Joop M. A. van Gerven Adam F. Cohen 《Journal of pharmacokinetics and pharmacodynamics》1998,26(5):581-593
The most widely applied model relating drug concentrations to effects is the Emax
model. In practice, concentration–effect relationships often deviate from a simple linear relationship but without reaching a clear maximum because a further increase in concentration might be associated with unacceptable or distorting side effects. The parameters for the Emax
model can only be estimated with reasonable precision if the curve shows sign of reaching a maximum, otherwise both EC50
and Emax
estimates may be extremely imprecise. This paper provides a solution by introducing a new parameter (S0
) equal to Emax/EC50
that can be used to characterize potency adequately even if there are no signs of a clear maximum. Simulations are presented to investigate the nature of the new parameter and published examples are used as illustration. 相似文献
974.
Y Nishizawa T Shoji S Tanaka M Yamashita A Morita M Emoto T Tabata T Inoue H Morii 《American journal of kidney diseases》1998,31(4):655-661
Leptin is a newly found hormone secreted by adipocytes that regulates food intake, thermogenesis, and body fat. We measured plasma leptin levels in 103 patients with chronic renal failure treated by hemodialysis and 167 age- and gender-matched healthy control subjects to examine the impact of renal failure on plasma leptin levels and the influence of leptin on body composition measured by dual-energy X-ray absorptiometry. Hemodialysis patients showed a significant decrease in both body fat mass and lean body mass compared with those of the control subjects. Plasma leptin was significantly elevated in the hemodialysis group over the controls. In both groups, leptin was higher in female than male subjects, and it correlated positively with percent body fat. The subjects were divided into six categories according to percent body fat, and plasma leptin levels were compared between the two groups in the same category. Leptin of hemodialysis patients was significantly higher than that of the control subjects in the percent body fat categories of 30 or greater, whereas there was no statistically significant difference in leptin concentrations in the lower percent body fat categories. This was also true in the comparison in each gender, and leptin levels in female subjects showed a more remarkable difference between the hemodialysis and control groups in obese categories. Multiple regression analysis in all subjects indicated that plasma leptin levels were independently affected by percent body fat, plasma insulin concentration, gender, and renal failure. The positive impact of renal failure on leptin remained significant in the subjects with percent body fat of 30 or greater in the multiple regression model, whereas it was no longer significant in the remaining lean subjects. In multiple regression analysis of factors affecting fat mass index and lean mass index, leptin level was selectively associated with fat mass index, but not with lean mass index, regardless of percent body fat ranges. These results indicate that renal failure is an important factor affecting plasma leptin levels, especially in obese female subjects, and that hyperleptinemia was closely related to fat mass but not to lean body mass in hemodialysis patients. 相似文献
975.
A species-specific nucleotide sequence of Mycobacterium tuberculosis encodes a protein that exhibits hemolytic activity when expressed in Escherichia coli. 总被引:3,自引:2,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)
Species-specific proteins may be implicated in the unique pathogenic mechanisms characteristic of Mycobacterium tuberculosis. In previous studies, a 3.0-kb species-specific DNA fragment of M. tuberculosis was identified (C. A. Parra, L. P. Londoño, P. del Portillo, and M. E. Patarroyo, Immun. 59:3411-3417, 1991). The nucleotide sequence of this 3.0-kb fragment has been obtained. This sequence was shown to contain two open reading frames (ORFs) whose putative gene products share 68.9% identity between each other. The major ORF shows 57.8% similarity with PLC-N and 53.2% similarity with PLC-H, two phospholipase C enzymes from Pseudomonas aeruginosa. The major ORF was amplified by PCR and cloned into the pGEX-5T expression vector. Cell extracts of Escherichia coli overexpressing this glutathione S-transferase fusion protein were shown to produce beta-hemolysis suggestive of phospholipase activity. Since phospholipase C enzymes have been reported as virulence factors of P. aeruginosa and also of the intracellular pathogen Listeria monocytogenes, it is possible that the proteins identified in this study could also play a role in sustaining tuberculosis infection in humans. 相似文献
976.
A. Schettino C. Giordano A. Parisi G. Calabrò 《Journal of the European Academy of Dermatology and Venereology》1995,4(2):153-154
We describe a mild form of drug-induced pemphigus in a woman with essential arterial hypertension treated with captopril. Complete recovery was observed three weeks after the therapy had been discontinued. 相似文献
977.
New latex reagent using monoclonal antibodies to capsular polysaccharide for reliable identification of both oxacillin-susceptible and oxacillin-resistant Staphylococcus aureus. 总被引:5,自引:5,他引:0
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)
J M Fournier A Bouvet D Mathieu F Nato A Boutonnier R Gerbal P Brunengo C Saulnier N Sagot B Slizewicz et al. 《Journal of clinical microbiology》1993,31(5):1342-1344
A new latex agglutination test (Pastorex Staph-Plus, Sanofi Diagnostics Pasteur), consisting of a mixture of latex particles coated with fibrinogen and immunoglobulin G for the detection of clumping factor and protein A and latex particles sensitized with monoclonal antibodies directed to Staphylococcus aureus serotype 5 and 8 capsular polysaccharides, was compared with three commercially available rapid agglutination methods for the identification of 220 isolates of S. aureus (61 oxacillin resistant) and 128 isolates of coagulase-negative staphylococci. The sensitivity for identification of S. aureus was high with the Pastorex Staph-Plus test (98.6%) compared with those of the other tests, which ranged from 91.8 to 84.5%. Test sensitivities for the identification of oxacillin-resistant S. aureus were as follows: Pastorex Staph-Plus, 95.1%; Pastorex Staph, 73.8%; Staphyslide, 72.1%; and StaphAurex, 49.2%. 相似文献
978.
P. A. Milligan P. E. McGill C. W. Howden A. W. Kelman B. Whiting 《European journal of clinical pharmacology》1993,45(6):507-512
Summary A randomised crossover study was performed in subjects with rheumatoid arthritis (or other arthropathies) to investigate if any alteration in the steady pharmacokinetics of the NSAID piroxicam (a drug which is extensively metabolised via cytochrome P450) or its major metabolites occurred as a result of coadministering either cimetidine or nizatidine.Twelve females and 2 males with mean age, weight, and albumin concentrations of 58 years, 61 kg, and 40 g·L–1 respectively, completed the study. Comparisons were made between the following parameters: plasma piroxicam AUCs [AUC0-24(P)], plasma 5-hydroxypiroxicam AUCs [AUC0-24(5-OHP)], the ratio of these i.e. AUC0-24(5-OHP):AUC0-24(p), the % piroxicam daily dose excreted in urine as 5-hydroxypiroxicam (before and after glucuronidase incubation); and the mean of the steady state trough piroxicam, and 5-hydroxypiroxicam concentrations (obtained during each study phase in addition to the wash-out period).A statistically significant difference as a result of initiating either cimetidine or nizatidine was obtained only for the ratio AUC0-23(5-OHP):AUC0-24(P). This was indicative of a weak potential to inhibit piroxicam hydroxylation.No clinically significant alteration in the steady state pharmacokinetics of piroxicam occurred in these subjects as a result of cimetidine or nizatidine coadministration. Consequently it is unlikely that any adverse events would arise from these combinations. 相似文献
979.
980.
Sarah A. Taylor Jacqueline Benedetti David Schuller Stephen P. Richman Goronwy O. Broun Alexander Hantel 《Investigational new drugs》1993,11(2-3):227-229
Summary Twenty-two patients with recurrent or metastatic squamous cell carcinoma of the head and neck were treated with piroxantrone 150 mg/m2 intravenously every 21 days. There were no objective responses. The 95% upper confidence bound for response is 15%. Primary toxicity was hematologic. 相似文献