全文获取类型
收费全文 | 58311篇 |
免费 | 3556篇 |
国内免费 | 71篇 |
专业分类
耳鼻咽喉 | 591篇 |
儿科学 | 1852篇 |
妇产科学 | 1590篇 |
基础医学 | 8375篇 |
口腔科学 | 1354篇 |
临床医学 | 5276篇 |
内科学 | 12063篇 |
皮肤病学 | 1034篇 |
神经病学 | 5146篇 |
特种医学 | 2225篇 |
外国民族医学 | 5篇 |
外科学 | 7741篇 |
综合类 | 260篇 |
一般理论 | 26篇 |
预防医学 | 4981篇 |
眼科学 | 1230篇 |
药学 | 4364篇 |
中国医学 | 89篇 |
肿瘤学 | 3736篇 |
出版年
2023年 | 563篇 |
2022年 | 437篇 |
2021年 | 1021篇 |
2020年 | 900篇 |
2019年 | 1009篇 |
2018年 | 1728篇 |
2017年 | 1579篇 |
2016年 | 1599篇 |
2015年 | 1457篇 |
2014年 | 1667篇 |
2013年 | 2753篇 |
2012年 | 3777篇 |
2011年 | 4003篇 |
2010年 | 1922篇 |
2009年 | 1295篇 |
2008年 | 3121篇 |
2007年 | 3205篇 |
2006年 | 3013篇 |
2005年 | 2858篇 |
2004年 | 2661篇 |
2003年 | 2487篇 |
2002年 | 2574篇 |
2001年 | 1628篇 |
2000年 | 1784篇 |
1999年 | 1252篇 |
1998年 | 401篇 |
1997年 | 318篇 |
1996年 | 294篇 |
1995年 | 254篇 |
1994年 | 237篇 |
1992年 | 529篇 |
1991年 | 484篇 |
1990年 | 487篇 |
1989年 | 449篇 |
1988年 | 470篇 |
1987年 | 466篇 |
1986年 | 451篇 |
1985年 | 482篇 |
1984年 | 415篇 |
1983年 | 349篇 |
1982年 | 251篇 |
1979年 | 406篇 |
1978年 | 258篇 |
1977年 | 248篇 |
1975年 | 247篇 |
1974年 | 277篇 |
1973年 | 276篇 |
1972年 | 245篇 |
1970年 | 260篇 |
1968年 | 253篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Martin Døssing Steffen Groth Jørgen Vestbo Ole Lyngenbo 《International archives of occupational and environmental health》1990,62(3):209-212
Summary Among 701 Copenhagen plumbers we examined the lung function of 23 never smokers, who had removed asbestos insulation and intermittently been exposed to high levels of asbestos for about 25 years without being exposed to welding fume. The plumbers had significantly lower TLC, MEF25, MEF50, closing volume and closing capacity in comparison to 23 never smoking electricians without asbestos exposure. There was no reduction in TLCO. Pulmonary clearance of aerosolized 99mTc-DTPA was normal indicating that the asbestos had not induced increases in pulmonary epithelial permeability. However, in 11 of the 23 plumbers the 99m-Tc-DTPA ventilation scintigrams had a slightly irregular and spotty appearance, which together with the results of the lung function tests are suggestive of small airways' dysfunction. None of the subjects had symptoms or clinical signs of lung disease. 相似文献
52.
After p.o. administration of 5-piperidino-7-[N-pentyl-N-(beta- hydroxyethyl)]amino-s-triazolo[1,5-a]pyrimidine (1; AR 12463) more than 15 metabolites were isolated from urine and feces of male Wistar rats. Only small amounts of unchanged 1 were observed. The structure of 12 metabolites was elucidated or proposed on the basis of UV-, 13C NMR- and mass spectra. Main metabolites are 5-piperidin-4'-olyl-7-[N-pentyl-N-(beta- hydroxyethyl)]amino-s-triazolo[1,5-a]pyrimidine and 5-piperidin-4'-olyl-7-[N-pent-4-olyl-N-(beta-hydroxyet hyl)]amino-s- triazolo[1,5-a]pyrimidine. The other metabolites are mainly hydroxy- or ketopentyl derivatives and piperidinoles or piperidinones, respectively. Conjugates of most of the metabolites were identified, but the ratio phase-I/II metabolites was about 3:1. In contrast to trapidil, 5-methyl-7-diethylamino-s- triazolo[1,5-a]pyrimidine, no hydroxy derivatives of the bicyclic system were observed. The major part of unchanged 1 and metabolites is excreted via kidneys. 相似文献
53.
To study interactions of head and eye during various motor tasks in a clinical environment, a recording system is needed which should be characterized by high precision and reliability. A computer-assisted optoelectronic method based on the SELSPOT system is described. All the equipment was specially designed for neuro-ophthalmologic purposes and fulfills the requirements. A range of programs was developed using several types of signal processing algorithms, allowing simultaneous one-dimensional and two-dimensional representation of motor acts of the head and eye, including separate analysis of slow and rapid movements. Thus, the method is suitable for analyzing physiologic and pathologic mechanisms of complex interactions. The quality of this novel SELSPOT application is demonstrated by recordings made during induced circular movements. 相似文献
54.
International comparisons show that populations having a high consumption of fish experience low incidence of breast cancer. We compared death rates from breast cancer among socioeconomic groups in a prospective study of 533,276 Norwegian women aged 35–54 years who were followed from 1970 through 1985. Compared with the reference group (wives of unskilled workers) the fishermen's wives had a decreased risk of breast cancer with a relative risk (RR) of 0.67 (95% confidence interval [CI]=0.47–0.94) adjusted for age and the number of children. Among fishermen's wives who were parous, adjustment for age at first birth gave an RR of 0.62 (CI=0.43–0.91). This study supports the hypothesis that certain aspects of diet, i. e., fish consumption, may be associated with lower breast-cancer mortality.Drs Lund and Bønaa are with the Institute of Community Medicine, University of Tromsø, Tromsø, Norway. Address correspondence to Dr Lund, Institute of Community Medicine, University of Tromsø, N-9037 Tromsø, Norway. 相似文献
55.
VIM thalamic stimulation for tremor in a patient with IgM paraproteinaemic demyelinating neuropathy. 总被引:1,自引:0,他引:1
Evzen R?zicka Robert Jech Katerina Zárubová Jan Roth Dusan Urgosík 《Movement disorders》2003,18(10):1192-1195
We demonstrate the effect of deep brain stimulation of the ventral intermediate thalamic nucleus on intractable action tremor, in a 72-year-old man suffering from neuropathy associated with monoclonal gammopathy. 相似文献
56.
Resistant strains of Escherichia coli were obtained by stepwise cultivation in subinhibitory concentrations of two antimicrobially active amine oxides. Changes in the chemical composition of the outer membrane of the resistant strains were accompanied also by different antigenic reactions. New precipitation lines were revealed by double immunodiffusion and immuno-electrophoretic methods. The results of immunochemical analysis confirm the findings that the resistance to amphiphilic compounds is associated with the outer membrane which limits the access of antimicrobially active molecules to their sites of action in the cytoplasmic membrane. 相似文献
57.
The study was performed to assess the ethiological role of bile in acute pancreatitis provoked by closed duodenal loop in rat. In group I a closed duodenal loop was created by method of Nevalainen. A similar operation was performed in group II, but the common pancreatico-biliary duct was ligated just under the liver. In the control group (group C) only the mobilization of duodenum was performed. After 24 hours the mortality rate was 20% in group I, but 0% in group II and C. The amount of ascitic fluid showed significant elevation in group I versus II and group C, and in group II as compared to group C, too. The serum amylase was significantly higher in group I than group II and group C, and in group II was also higher as compared to group C. Serum total protein differed significantly between all groups, while albumin and total calcium were significantly lower in group I than group II, but group II was only slightly reduced versus group C. Histology showed no differences between groups I and II, but both differed significantly from group C. In conclusion bile seems to be an aggressive factor in pathogenesis of acute pancreatitis induced by closed duodenal loop in rat, but other factors may play more important roles. 相似文献
58.
Striae distensae are an appreciable cosmetic problem for many pregnant women. Preventive application of a water/oil massage cream was tested in a group of 24 gravidae (control group: 26 patients). In the untreated control group striae distensae were observed in two-thirds of the patients, whereas the prophylactically-treated gravidae showed development of striae in only one third of the group given the test preparation. Better results were obtained in women with a favourable constitutional predisposition than in patients with a tendency to overweight. The massage cream was well tolerated by all gravidae. 相似文献
59.
Circular stereotactic callosotomy: A preliminary report 总被引:1,自引:0,他引:1
P. Nádvornik P. Krupa J. Chrastina V. Smrčka Z. Novák E. Zbofřilová 《Acta neurochirurgica》1997,139(4):359-360
Summary The authors propose a new method for performing Stereotactic callosotomy, which they have named circular callosotomy. The operating device is the original Riechert-Mundinger's string electrode, which can be protruded through a side window and by rotating the probe it is possible to cut the commisural pathways to the extent required. The anatomical results of the operation can be checked using MRI scanning. 相似文献
60.
Glutamine and Other Amino Acid Losses During Continuous Venovenous Hemodiafiltration 总被引:2,自引:0,他引:2
I. Novák V. rámek H. Pittrová Z. Ruavý P. Têinský S. Lacigová M. Eiselt L. Kohoutková E. Veselá K. Opatrný Jr. 《Artificial organs》1997,21(5):359-363
Abstract: Serum amino grams and daily losses of glutamine (Gin) and other amino acids (AAs) into diafiltrate were measured during the first 5 days of continuous venovenous hemodiafiltration (CVVHDF) in 6 ICU patients with acute renal failure (ARF). Four patients had ARF as a part of multiple organ failure (MOF) of septic origin, and 2 patients had isolated ARF because of primary renal disease. During the study, all the patients received defined total parenteral nutrition (TPN). The mean daily AA losses into dialysate were relatively low (0.61 ± 0.1 g N ) and reached 4.5% of the daily AA substitution. Gln represented 32.7 ± 5.9% of the total AA losses (0.19 ± 0.04 g N ). Serum levels of Gin (p = 0.002) and of most other AAs were significantly lower in the patients than in the control subjects (AA analysis in 16 healthy volunteers). Phenylalanine (Phe) was the only AA that was increased significantly (p < 0.01) in the patients. The mean patient serum concentrations of Phe and tyrosine were significantly higher (p < 0.03) than the correspondent concentrations in dialysate, but the lysine concentration was higher in dialysate (p < 0.03). The serum and dialysate concentrations of other AAs did not differ. Gin in serum decreased significantly (p < 0.03) on the second day of CVVHDF but returned to the baseline levels subsequently. Serum concentrations of Phe increased on the second day of CVVHDF (p < 0.05). Serum concentrations of other AAs remained stable during the whole study. We conclude that Gin losses into dialysate during CVVHDF are relatively low, but CVVHDF itself may induce changes in Gin metabolism and distribution that are reflected by a decrease of serum Gin levels at the institution of this treatment. Therefore, the need for Gin supplementation in ICU patients is even greater in the first days of CVVHDF. 相似文献