全文获取类型
收费全文 | 16815篇 |
免费 | 1449篇 |
国内免费 | 46篇 |
专业分类
耳鼻咽喉 | 198篇 |
儿科学 | 454篇 |
妇产科学 | 435篇 |
基础医学 | 2471篇 |
口腔科学 | 824篇 |
临床医学 | 1515篇 |
内科学 | 3849篇 |
皮肤病学 | 395篇 |
神经病学 | 1512篇 |
特种医学 | 588篇 |
外科学 | 2193篇 |
综合类 | 107篇 |
一般理论 | 8篇 |
预防医学 | 1419篇 |
眼科学 | 283篇 |
药学 | 943篇 |
中国医学 | 48篇 |
肿瘤学 | 1068篇 |
出版年
2023年 | 118篇 |
2022年 | 236篇 |
2021年 | 454篇 |
2020年 | 301篇 |
2019年 | 491篇 |
2018年 | 623篇 |
2017年 | 443篇 |
2016年 | 477篇 |
2015年 | 530篇 |
2014年 | 671篇 |
2013年 | 814篇 |
2012年 | 1163篇 |
2011年 | 1133篇 |
2010年 | 722篇 |
2009年 | 631篇 |
2008年 | 903篇 |
2007年 | 976篇 |
2006年 | 846篇 |
2005年 | 815篇 |
2004年 | 682篇 |
2003年 | 613篇 |
2002年 | 527篇 |
2001年 | 353篇 |
2000年 | 326篇 |
1999年 | 366篇 |
1998年 | 148篇 |
1997年 | 140篇 |
1996年 | 100篇 |
1995年 | 104篇 |
1994年 | 97篇 |
1993年 | 93篇 |
1992年 | 234篇 |
1991年 | 209篇 |
1990年 | 179篇 |
1989年 | 198篇 |
1988年 | 169篇 |
1987年 | 147篇 |
1986年 | 162篇 |
1985年 | 153篇 |
1984年 | 112篇 |
1983年 | 92篇 |
1982年 | 50篇 |
1981年 | 56篇 |
1979年 | 72篇 |
1978年 | 61篇 |
1976年 | 46篇 |
1975年 | 51篇 |
1974年 | 40篇 |
1973年 | 54篇 |
1972年 | 47篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
Luís Mariano Isabel Vila?a Jorge Almeida Mota Garcia Maria Júlia Maciel 《Revista portuguesa de cardiologia》2007,26(3):265-270
Apical ballooning is a novel clinical entity reported in different contexts of physical and psychological stress, which is more common in middle-aged women. Of unknown etiology, the syndrome is characterized by a sudden and transient dilatation of the left ventricular apex in the absence of obstructive atherosclerotic coronary disease or evidence of myocardial necrosis, with total late recovery of ventricular function. The authors report the case of a 53-year-old woman who was admitted to the emergency room with left arm ischemia and low cardiac output, requiring ventilatory support. Left catheterization showed typical medial and apical myocardial dysfunction, with normal coronary arteries. Transesophageal echocardiography revealed a thrombus attached to the lower face of the aortic arch, which probably explained the thromboembolism of the arm but was unlikely to be the cause of the left ventricular dysfunction since there were no enzymatic or electrocardiographic signs of myocardial necrosis and normal wall motion was fully recovered. 相似文献
23.
24.
C J Buggé S R Gautam L E Parke J T Mason D B Garcia 《Journal of pharmaceutical sciences》1990,79(12):1095-1098
An HPLC method is described for the simultaneous and rapid determination of sulfasalazine (salicylazosulfapyridine) and two of its metabolites, sulfapyridine and N-acetylsulfapyridine, in human serum. The range of quantitation is 0.1 to 12 micrograms/mL for sulfasalazine and sulfapyridine and 0.25 to 12 micrograms/mL for N-acetylsulfapyridine. Serum is mixed with acetonitrile containing the internal standard sulfamethazine and the ion-pairing agent tetraethylammonium chloride. The acetonitrile extract is concentrated and analyzed by HPLC, using a new polymer-based column, and detected by UV spectroscopy at 270 nm. This paper is the first both to describe the simultaneous analysis of all three of the compounds from serum and to present sulfasalazine concentration-time data following oral administration to humans. 相似文献
25.
V Dietz M Lezana C Garcia Sancho R Montesano 《International journal of epidemiology》1992,21(4):800-806
In 1985, the Pan American Health Organization adopted the goal of eradication of poliomyelitis from the Americas by 1990. Strategies to accomplish this included high vaccination coverage, aggressive outbreak control, and active surveillance for acute flaccid paralysis (AFP). Although the sensitivity of AFP surveillance for detecting paralytic poliomyelitis cases is high, studies have shown the specificity to be low. In 1990, 2497 notified cases of AFP were investigated in the Americas of which 2146 had stool specimens collected. However, only 18 were confirmed as poliomyelitis by isolation of wild poliovirus from stool specimens, 71 were classified as being compatible with poliomyelitis. Cases of AFP due to causes other than poliomyelitis result in extensive but unnecessary outbreak control measures. To predict, at initial clinical evaluation, the likelihood of future confirmation as a case of poliomyelitis, likelihood ratios (LR) were calculated for different combinations of clinical characteristics of AFP cases (249) from Mexico in 1989 and 1990. The best predictors in a child with AFP were proximal muscle involvement which progressed '4 days together with fever at onset of paralysis, and proximal and unilateral involvement with either fever at onset or paralysis which progressed '4 days. The odds would increase by 12 that the child would eventually be confirmed as poliomyelitis (19), based on a stool culture positive for wild poliovirus (95% confidence interval (CI) 2.6-55.9). A guide for use in the field is proposed whereby local health officials, often with little training in neurological evaluation, can predict at initial clinical examination the likelihood that an AFP case will subsequently be confirmed as poliomyelitis.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
26.
We describe a fibrolamellar carcinoma of the liver in a 12-year-old girl and review the literature concerning the occurrence of this distinct hepatic neoplasm in children up to the age of 16 years. The results of our electron microscopic and immunohistologic studies suggest that some cells of this tumor exhibit neuroendocrine differentiation. This finding has important theoretical implications relative to the tumor's histogenesis and practical implications with respect to the search for tumor markers of clinical usefulness and possibly for therapy. 相似文献
27.
Tony M. Keaveny Tania P. Pinilla R. Paul Crawford David L. Kopperdahl Albert Lou 《Journal of orthopaedic research》1997,15(1):101-110
We sought to quantify the systematic and random errors associated with-artifacts in the platens compression test for trabecular bone. Our hypothesis was that while errors may depend on anatomic site, they do not depend on apparent density and therefore have substantial random components. Trabecular bone specimens were first tested nondestructively using newly developed accurate protocols and then were tested again using the platens compression test. Percentage differences in modulus between the techniques (bovine) proximal tibia [n = 18] and humerus [n = 17] and human lumbar spine, [n = 9] were in the range of 4-86%. These differences did not depend on anatomic site (p = 0.21) and were only weakly dependent on apparent density and specimen aspect ratio (r2 < 0.10). The mean percentage difference in modulus was 32.6% representing the systematic component of the end-artifact error. Neglecting the minor variations explained by density and specimen size (approximately 10%), an upper bound on the random error from end-artifacts in this experiment was taken as the SD of the modulus difference (±18.2%). Based on a synthesis of data taken from this study and from the literature, we concluded that the systematic underestimation error in the platens compression test can be only approximated and is in the range of 20-40%; the substantial random error (±12.5%) confounds correction, particularly when the sample size is small. These errors should be considered when interpreting results from the platens test, and more accurate testing techniques should be used when such errors are not acceptable. 相似文献
28.
The DNA content and regional DNA heterogeneity in correlation with clinicopathologic parameters and patient survival were investigated in epithelioid sarcoma. Such neoplasms preponderantly manifest diploid DNA content and a remarkably stable intratumoral and intertumoral DNA content. Small tumor size (less than 5.0 cm) and low S-phase fraction (less than 5%) were significant prognostic factors in this study. Ploidy status, mitotic rate, age, and postsurgical treatment were not significantly correlated with survival. 相似文献
29.
Cynthia S. Pomerleau Anne W. Garcia Ovide F. Pomerleau Oliver G. Cameron 《Psychoneuroendocrinology》1992,17(6):627-638
Nicotine intake, menstrual and smoking withdrawal symptomatology, and baseline cortisol and MHPG were assessed in nine women smokers under conditions of ad lib smoking and overnight abstinence in three menstrual phases (early follicular, mid-to-late follicular, and late luteal). A trend towards higher nicotine intake p <0.100 was observed in the mid-to-late follicular phase. Although me menstrual symptomatology was not significantly elevated during the smoking abstinence condition overall, abstinence appeared to prevent the normal reduction in symptomatology during the mid-to-late follicular phase that occurred under conditions of ad lib smoking. Menstrual and withdrawal symptoms were highly correlated, and both were most pronounced during the late luteal/abstinence condition. The smoking-specific item “craving” reflected this pattern, though in attenuated form, suggesting that the observed exacerbation of withdrawal symptomatology was not simply due to generalized dysphoria, as queried in both instruments. MHPG was significantly elevated in the late luteal phase, whereas cortisol was significantly higher during ad lib smoking than during abstinence and tended to be highest in the mid-to-late follicular phase. Further investigation will be needed to determine the functional significance of these findings for understanding and treating smoking in women. 相似文献
30.
Alterations in the superoxide dismutase gene of an isoniazid-resistant strain of Mycobacterium tuberculosis. 下载免费PDF全文
Y Zhang M J Garcia R Lathigra B Allen C Moreno J D van Embden D Young 《Infection and immunity》1992,60(6):2160-2165
Genetic analysis of a set of six Mycobacterium tuberculosis strains differing in virulence for the guinea pig revealed an altered restriction enzyme fragmentation pattern associated with the superoxide dismutase (SOD) gene in a low-virulence, isoniazid-resistant strain. In addition, it was found that the SOD enzyme produced by the isoniazid-resistant strain differed in its electrophoretic mobility from the SOD of other M. tuberculosis strains. Detailed analysis of these strain-specific differences showed that the restriction fragment length polymorphism resulted from the presence of a copy of a repetitive element 552 bp upstream of the SOD gene and that the anomalous electrophoretic mobility arose from a single nucleotide change, resulting in replacement of an aspartic acid residue by histidine in the SOD enzyme of the isoniazid-resistant strain. Possible relationships between genetic changes and strain-dependent differences in virulence are discussed. 相似文献