全文获取类型
收费全文 | 441篇 |
免费 | 39篇 |
国内免费 | 52篇 |
专业分类
耳鼻咽喉 | 3篇 |
儿科学 | 16篇 |
基础医学 | 45篇 |
口腔科学 | 11篇 |
临床医学 | 104篇 |
内科学 | 103篇 |
皮肤病学 | 7篇 |
神经病学 | 14篇 |
特种医学 | 71篇 |
外科学 | 42篇 |
综合类 | 19篇 |
预防医学 | 25篇 |
眼科学 | 4篇 |
药学 | 46篇 |
肿瘤学 | 22篇 |
出版年
2018年 | 5篇 |
2016年 | 5篇 |
2015年 | 3篇 |
2014年 | 7篇 |
2013年 | 17篇 |
2012年 | 8篇 |
2011年 | 8篇 |
2010年 | 12篇 |
2009年 | 10篇 |
2008年 | 8篇 |
2007年 | 48篇 |
2006年 | 12篇 |
2005年 | 20篇 |
2004年 | 6篇 |
2003年 | 6篇 |
2002年 | 15篇 |
2001年 | 14篇 |
2000年 | 10篇 |
1998年 | 19篇 |
1997年 | 11篇 |
1996年 | 20篇 |
1995年 | 15篇 |
1994年 | 20篇 |
1993年 | 10篇 |
1992年 | 8篇 |
1991年 | 11篇 |
1990年 | 8篇 |
1989年 | 14篇 |
1988年 | 7篇 |
1987年 | 11篇 |
1986年 | 10篇 |
1985年 | 12篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1978年 | 8篇 |
1977年 | 13篇 |
1976年 | 11篇 |
1975年 | 12篇 |
1974年 | 11篇 |
1973年 | 10篇 |
1972年 | 6篇 |
1971年 | 5篇 |
1970年 | 8篇 |
1969年 | 6篇 |
1968年 | 3篇 |
1940年 | 2篇 |
排序方式: 共有532条查询结果,搜索用时 15 毫秒
11.
Cystic hypersecretory carcinoma (CHC) is a rare variant of intraductal carcinoma. A CHC in a 50-year-old woman was excised and processed for light and electron microscopy and immunohistochemistry. The tumor had a marked cystic appearance. The walls of the cysts consisted of epithelial and myoepithelial cells and a well-developed basement membrane. The epithelial cells contained well-developed rough-surfaced endoplasmatic reticulum and Golgi apparatus. Secretory granules were not detected, with the exception of a few mucus-producing cells. The secretion was predominantly homogenous, reminiscent of thyroid colloid, and demonstrated distinct PAS positivity. The cells displayed a strong labeling with epithelial membrane antigen (EMA) and EMA-positive structures were observed within the intraluminal secretion, too. Some of these were stained by alcian blue. In addition, the colloid-like material was admixed with mucus showing a filamentous internal structure and lipid droplets resulting in some heterogenity of the secretion. Intraductal micropapillary proliferation in some of the cysts and adjacent nondistended ducts was a further defining feature of the tumor. Steroid hormone receptor and Ki-67 proliferation marker immuno his Tochemistry showed scattered positivity among the tumor cells. These results are in agreement with previous observations and further clarify the nature of this low-grade in situ cancer. 相似文献
12.
Richard M. Libbin Albert Hirschman Philip Person Norman C. Blumenthal 《Calcified tissue international》1992,51(1):62-66
Summary Cartilage is encountered in the skeletons of many advanced invertebrates, yet it never calcifies or is replaced by bone. In an attempt to account for the absence of bone in invertebrates, we tested a hypothesis proposing that absence or inadequate quantities of several enzymes associated with vertebrate osteogenesis may underlie the failure of the invertebrates to evolve bone. The enzymes examined were alkaline phosphatase, alanyl -naphthylamidase, and neutral protease. Their activities were measured in the gill cartilage of the Atlantic horseshoe crab, Limulus polyphemus, and the odontophore cartilage of the marine whelk, Busycon canaliculatum. Animals were collected from the Cape Cod area. Samples of cartilage of Limulus perichondrium, various nonskeletal tissues, and neonatal rat calvaria, the latter as a reference standard, were homogenized in 0.1 M phosphate buffer (pH 7.1) and analyzed for protein content and the above-mentioned enzyme activities. Alkaline phosphatase specific activity was readily detected in most tissues except the invertebrate cartilage specimens in which it was present only at near-trace levels. Naphthylamidase and protease activities were present in all tissues. In a single experiment, higher phosphatase values were recorded for Limulus cartilage retaining perichondrium, but in a subsequent trial assaying cartilage retaining perichondrium, denuded cartilage, and isolated perichondrium separately, it was demonstrated that phosphatase activity resided primarily within the perichondrium. Exposure of thick cryostat sections to p-nitrophenyl phosphate confirmed the suspicion that alkaline phosphatase activity was present principally in the perichondrium. In view of the strong association between alkaline phosphatase and vertebrate cartilage mineralization it is proposed that extremely low levels of this enzyme may contribute to the failure of invertebrate cartilage to be replaced by bone. 相似文献
13.
14.
The purpose of the paper is to describe how residents express preferences for end-of-life (EOL) care. For this qualitative study, we conducted semi-structured interviews and completed conventional content analysis to describe how residents’ expressed their preferences for care at the end of life. Sixteen residents from four nursing homes (NH) in southeastern Pennsylvania participated in this study. Residents were on average 88 years old, primarily non White, and widowed. Three key domains emerged from the analyses: Preferences for Today, Anticipating the End of My Life, and Preferences for Final Days. Residents linked their everyday living and EOL preferences by using ‘if and then’ logic to convey anticipation and readiness related to EOL. These findings suggest new strategies to start discussions of EOL care preferences with NH residents. 相似文献
15.
Current patterns of infection in multiple myeloma 总被引:2,自引:0,他引:2
In twenty-six of fifty-five patients with multiple myeloma admitted to The Mount Sinai Hospital between January 1, 1969, and June 30, 1970, a total of twenty-nine infections were found. Gram-negative organisms accounted for 72 per cent of the thirty-nine isolates obtained from these patients. Fourteen patients had urinary tract infections with negative blood cultures (patients without septicemia), and eleven others had a total of thirteen episodes of bacteremia (patients with septicemia). The group of patients without septicemia could not be distinguished from those with septicemia in respect to age, sex, drug therapy, blood urea nitrogen and serum calcium levels, or white blood cell and differential counts. Gram-negative isolates were obtained from six of eight patients with pneumonia. Almost all the patients had low serum levels of immunoglobulins M and A (IgM and IgA). Tuberculin skin tests gave negative reactions in the eight patients tested. 相似文献
16.
BACKGROUND:
Flavonoids are polyphenolic substances with antioxidant properties, and they are found in different vegetables and fruits. Epidemiological studies have shown that the consumption of flavonoids reduces the prevalence of cardiovascular diseases. The use of synthetic antioxidants, however, has been limited because of their toxicity. Therefore, medical researchers have intensified their quest to find natural antioxidants.OBJECTIVES:
To investigate the effect of several pure flavonoids, such as kaempferol, quercetin, morin and rutin, on red blood cell hemolysis and evaluate their -SH capacity as an indicator of membrane protection.METHODS:
The rate of hemolysis and cell membrane -SH capacity were determined by spectrophotometry. Red blood cell peroxidation was induced using 2,2′-azo-bis-(2-amidinopropane) dihydrochloride. The effect of each flavonoid on hemolysis was examined at three concentrations (0.5 μg/mL, 5 μg/mL and 10 μg/mL), however, only the greatest concentration (10 μg/mL) of each flavonoid was used to study the effect on -SH groups.RESULTS:
In all cases, the antioxidant activity was dose-dependent. Rutin showed the highest inhibitory effect on hemolysis among flavonoids (42.5%). The protective effect of kaempferol, rutin and morin against -SH group oxidation measured 7.7%, 23.3% and 26.4%, respectively.CONCLUSIONS:
Results showed that flavonoids and flavonoid-containing plants can be used as natural antioxidants for the treatment and prevention of disease conditions, the pathogenesis of which is mediated by lipid peroxidation. 相似文献17.
18.
Does laser trabeculoplasty prevent steroid glaucoma? 总被引:4,自引:0,他引:4
OBJECTIVE: To investigate the effect of laser trabeculoplasty in the normal myopic eye on steroid intraocular pressure responsiveness in patients undergoing radial keratotomy. MATERIALS AND METHODS: Diode laser trabeculoplasty was performed on 94 patients with myopia undergoing radial keratotomy who were then started on dexamethasone drops. Intraocular pressures were measured by applanation tonometry compensated for corneal flattening. RESULTS: Twenty-eight percent of patients had an intraocular pressure increase of 6 mm Hg or more by the fourth week. CONCLUSION: Laser trabeculoplasty does not prevent steroid intraocular pressure increase in patients with myopia. 相似文献
19.
Khaled?Alanezi G?Scott?Milencoff Frank?GH?Baillie Andre?Lamy John?D?UrschelEmail author 《BMC surgery》2002,2(1):4
Background
Canadian trauma units have relatively little experience with major cardiac trauma (disruption of a cardiac chamber) so injury outcome may not be comparable to that reported from other countries. We compared our outcomes to those of other centers. 相似文献20.
Objective : This study was carried out to evaluate the significance of amniotic fluid protein ingestion and absorption on fetal growth.
Methodology : Neonates with small bowel atresia during a 30 year period were studied retrospectively.
Results : There were 56 patients enlisted, 17 with duodenal atresia, 18 with jejunal atresia and 21 with ileal atresia. The percentage of mothers with polyhydramnios and the percentage of premature babies decreases as the intestinal atresia becomes more distal. The mean gestational age and the mean birthweight increase as the intestinal atresia becomes more distal. On the other hand, the percentage of the neonates with birthweight below the 50th and the 10th percentiles do not differ significantly as the intestinal atresia becomes more distal.
Conclusions : It appears that the variation of birthweights in babies with different levels of small bowel atresia may be due to the difference in gestation caused by polyhydramnios. The effect of amniotic fluid protein absorption on fetal bodyweight could not be demonstrated clinically in this study. 相似文献
Methodology : Neonates with small bowel atresia during a 30 year period were studied retrospectively.
Results : There were 56 patients enlisted, 17 with duodenal atresia, 18 with jejunal atresia and 21 with ileal atresia. The percentage of mothers with polyhydramnios and the percentage of premature babies decreases as the intestinal atresia becomes more distal. The mean gestational age and the mean birthweight increase as the intestinal atresia becomes more distal. On the other hand, the percentage of the neonates with birthweight below the 50th and the 10th percentiles do not differ significantly as the intestinal atresia becomes more distal.
Conclusions : It appears that the variation of birthweights in babies with different levels of small bowel atresia may be due to the difference in gestation caused by polyhydramnios. The effect of amniotic fluid protein absorption on fetal bodyweight could not be demonstrated clinically in this study. 相似文献