全文获取类型
收费全文 | 3497篇 |
免费 | 334篇 |
国内免费 | 115篇 |
专业分类
耳鼻咽喉 | 47篇 |
儿科学 | 86篇 |
妇产科学 | 79篇 |
基础医学 | 552篇 |
口腔科学 | 99篇 |
临床医学 | 551篇 |
内科学 | 648篇 |
皮肤病学 | 60篇 |
神经病学 | 225篇 |
特种医学 | 151篇 |
外国民族医学 | 2篇 |
外科学 | 500篇 |
综合类 | 101篇 |
一般理论 | 5篇 |
预防医学 | 284篇 |
眼科学 | 113篇 |
药学 | 317篇 |
中国医学 | 2篇 |
肿瘤学 | 124篇 |
出版年
2021年 | 33篇 |
2019年 | 42篇 |
2018年 | 45篇 |
2017年 | 44篇 |
2016年 | 40篇 |
2015年 | 53篇 |
2014年 | 70篇 |
2013年 | 114篇 |
2012年 | 140篇 |
2011年 | 161篇 |
2010年 | 109篇 |
2009年 | 106篇 |
2008年 | 131篇 |
2007年 | 193篇 |
2006年 | 154篇 |
2005年 | 127篇 |
2004年 | 104篇 |
2003年 | 110篇 |
2002年 | 108篇 |
2001年 | 100篇 |
2000年 | 112篇 |
1999年 | 92篇 |
1998年 | 71篇 |
1997年 | 71篇 |
1996年 | 64篇 |
1995年 | 47篇 |
1994年 | 55篇 |
1993年 | 43篇 |
1992年 | 76篇 |
1991年 | 73篇 |
1990年 | 73篇 |
1989年 | 70篇 |
1988年 | 78篇 |
1987年 | 66篇 |
1986年 | 57篇 |
1985年 | 55篇 |
1984年 | 60篇 |
1983年 | 58篇 |
1982年 | 37篇 |
1981年 | 35篇 |
1980年 | 49篇 |
1979年 | 65篇 |
1978年 | 39篇 |
1977年 | 43篇 |
1976年 | 48篇 |
1975年 | 44篇 |
1973年 | 37篇 |
1972年 | 39篇 |
1971年 | 30篇 |
1970年 | 27篇 |
排序方式: 共有3946条查询结果,搜索用时 0 毫秒
71.
72.
73.
Penick EC Nickel EJ Powell BJ Liskow BI Campbell J Dale TM Hassanein RE Noble E 《Journal of studies on alcohol》1999,60(2):188-202
OBJECTIVE: This study directly compared the clinical validity of 11 empirically defined alcoholism typologies to determine whether some typologies are clinically more valid than others. METHOD: A sample of 360 hospitalized alcoholic men were extensively evaluated at entry into the study and again 1 year later. Twenty-three measures of clinical validity were employed; 15 were postdictive and 8 were predictive. Postdictive retrospective measures obtained at entry into the study included family history, age of onset and lifetime course characteristics associated with alcoholism severity, general psychopathology and psychosocial functioning. Predictive outcome measures drawn from information obtained during the 1-year follow-up included: abstinence, alcoholism severity and clinician ratings of outcome. The measures were subjected to various statistical analyses, including factor analysis. RESULTS: We found that all of the alcoholism typologies met at least 7 of the 23 a priori measures of clinical validity. The correlations between these conceptually and methodologically disparate typologies were often striking. Exploratory factor analysis, which explained 35% of the variance, suggested three possible underlying dimensions to account for the overlap among typologies: (1) age and its correlates, including age-of-alcoholism onset; (2) "pure" alcoholism versus psychiatrically heterogeneous alcoholism that encompassed antisocial personality disorder; and (3) current severity of psychiatric distress, impairment and dysfunction. CONCLUSIONS: No single method of subtyping alcoholics clearly emerged as superior. All demonstrated some degree of predictive and postdictive clinical validity. Most methods of subtyping correlated positively with each other at moderate, but typically significant, levels. 相似文献
74.
75.
M C Fournié-Zaluski P Coric S Turcaud E Lucas F Noble R Maldonado B P Roques 《Journal of medicinal chemistry》1992,35(13):2473-2481
In order to evaluate the possible advantages of potentiating the effects of the endogenous enkephalins, to obtain analgesia without the serious drawbacks of morphine, it was essential to design systemically active compounds which inhibit the two metabolizing enzymes, aminopeptidase N (APN) and neutral endopeptidase 24.11 (NEP). A new concept combining the idea of "prodrug" and "mixed inhibitor" was therefore developed. Given the high efficiency of beta-mercaptoalkylamines as APN inhibitors and of N-(mercaptoacyl) amino acids as NEP inhibitors, compounds associating these molecules through disulfide or thioester bonds, which are known to increase lipophilicity and to favor passage across the blood-brain barrier, have been synthesized. An HPLC study indicated that the disulfide bridge was resistant to serum enzymes but was cleaved by brain membrane homogenates, suggesting that the active inhibitors were released in the central nervous system. The validity of the approach was verified by the efficient antinociceptive responses obtained in the hot plate test in mice after iv administration of disulfide-containing inhibitors (ED50s of from 4 to 26 mg/kg on the jump latency time). The analgesic potencies of the "mixed inhibitor-prodrug" RB 101 [H2NCH(CH2CH2SCH3)CH2SSCH2CH(CH2Ph)CONHCH( CH2Ph)COOCH2Ph] after iv administration were three times greater than those of a similar combined dose of its two constitutive moieties. The separation of the two diastereoisomers constituting RB 101 showed that the analgesia has a stereochemical dependence, the (S,S,S)-isomer being more active than the (S,R,S)-isomer. Furthermore, in the tail flick test in the rat, RB 101 gave 38% analgesia at a dose of 80 mg/kg. Due to its high efficiency and its longer pharmacological effect, RB 101 was selected for a complete study of its analgesic properties. 相似文献
76.
One hundred and twenty-one patients receiving 140 courses of aminoglycoside-therapy (76% gentamicin and 24% tobramycin) were retrospectively studied to assess the monitoring practices for these drugs. Compliance with specific items of the monitoring guidelines ranged from 16 to 93%. An education program regarding aminoglycoside monitoring, particularly the use of serum aminoglycoside concentrations, is necessary in the study institutions. 相似文献
77.
Neil H Segal Paul Pavlidis William S Noble Cristina R Antonescu Agnes Viale Umadevi V Wesley Klaus Busam Humilidad Gallardo Dianne DeSantis Murray F Brennan Carlos Cordon-Cardo Jedd D Wolchok Alan N Houghton 《Journal of clinical oncology》2003,21(9):1775-1781
PURPOSE: To develop a genome-based classification scheme for clear-cell sarcoma (CCS), also known as melanoma of soft parts (MSP), which would have implications for diagnosis and treatment. This tumor displays characteristic features of soft tissue sarcoma (STS), including deep soft tissue primary location and a characteristic translocation, t(12;22)(q13;q12), involving EWS and ATF1 genes. CCS/MSP also has typical melanoma features, including immunoreactivity for S100 and HMB45, pigmentation, MITF-M expression, and a propensity for regional lymph node metastases. MATERIALS AND METHODS: RNA samples from 21 cell lines and 60 pathologically confirmed cases of STS, melanoma, and CCS/MSP were examined using the U95A GeneChip (Affymetrix, Santa Clara, CA). Hierarchical cluster analysis, principal component analysis, and support vector machine (SVM) analysis exploited genomic correlations within the data to classify CCS/MSP. RESULTS: Unsupervised analyses demonstrated a clear distinction between STS and melanoma and, furthermore, showed that CCS/MSP cluster with the melanomas as a distinct group. A supervised SVM learning approach further validated this finding and provided a user-independent approach to diagnosis. Genes of interest that discriminate CCS/MSP included those encoding melanocyte differentiation antigens, MITF, SOX10, ERBB3, and FGFR1. CONCLUSION: Gene expression profiles support the classification of CCS/MSP as a distinct genomic subtype of melanoma. Analysis of these gene profiles using the SVM may be an important diagnostic tool. Genomic analysis identified potential targets for the development of therapeutic strategies in the treatment of this disease. 相似文献
78.
79.
Hypospadias trends in two US surveillance systems 总被引:6,自引:0,他引:6
OBJECTIVE: Hypospadias is a common congenital anomaly, the cause of which is unknown. Unexplained increases in the rates of hypospadias occurred in five European countries in the 1970s and 1980s. We examined data from two birth defects surveillance systems in the United States for evidence of similar trends. METHODOLOGY: The Metropolitan Atlanta Congenital Defects Program (MACDP) provided birth prevalence rates from 1968 to 1993. The nationwide Birth Defects Monitoring Program (BDMP) provided rates from 1970 to 1993. MACDP data are population-based and could be categorized by the severity of the hypospadias. BDMP data allowed analysis of rate trends for the four census regions of the United States. RESULTS: Data from both surveillance systems showed an approximate doubling of hypospadias rates in the 1970s and 1980s. MACDP data showed that the rate of severe cases increased while the ratio of mild to severe cases decreased. BDMP data showed that hypospadias rates increased markedly in all four regions of the United States. CONCLUSIONS: The observed increases are unlikely to be attributable to increased sensitivity of the surveillance systems or the identification of more mild cases by physicians over time, because either trend would have increased rather than decreased the ratio of mild to severe cases. If real, these trends represent the largest number of cases and the first report of an increase in hypospadias rates outside of Europe. Additional investigation of a possible increase in hypospadias rates is warranted. 相似文献
80.
Black tea and mammary gland carcinogenesis by 7,12- dimethylbenz[a]anthracene in rats fed control or high fat diets 总被引:3,自引:1,他引:3
Epidemiological studies suggest that tea may reduce cancer risk, and in
laboratory rodents, chemopreventive effects of tea or purified extracts of
tea have been demonstrated in lung, gastrointestinal tract and skin. There
is some evidence of chemoprevention by tea in the mammary gland, but the
data are not conclusive. In order to evaluate more fully the possible
influence of black tea on 7,12-dimethylbenz[a]anthracene (DMBA)-induced
mammary gland tumors in the female S-D (Sprague-Dawley) rat, three large
studies were performed: experiment 1, tumorigenesis in rats fed AIN-76A
diet and given 25 mg/kg DMBA and 1.25 or 2.5% whole tea extract or water to
drink; experiment 2, tumorigenesis in rats given 15 mg/kg DMBA and the same
diet and fluids as in experiment 1; experiment 3, tumorigenesis in rats fed
control or HF (high fat, corn oil) diet and given 15 mg/kg DMBA and 2% tea
or water to drink. Tea was given throughout the experiment; DMBA was given
by gastric gavage at 8 weeks of age. There was no consistent effect of tea
on tumorigenesis in rats fed AIN-76A diet; there was, however, evidence in
experiment 3 of a reduction of tumorigenesis by tea in rats fed the HF
diet. In experiment 3, rats fed the HF diet and given water showed the
expected increase in tumor burden (number and weight) compared with rats
fed control diet. However, rats fed the HF diet and given 2% tea showed no
increase in tumor burden; their tumor burden was significantly lower than
in rats fed the HF diet and given water (P < 0.01) and was not different
from rats fed control diet and given water or tea. In addition, in
experiment 3, the number of malignant tumors per tumor- bearing rat was
increased by the HF diet in water-drinking rats (P < 0.01) but not in
tea-drinking rats. Therefore, it appears that tea partially blocked the
promotion of DMBA-induced mammary tumorigenesis by the HF diet.
相似文献