全文获取类型
收费全文 | 45697篇 |
免费 | 4572篇 |
国内免费 | 1230篇 |
专业分类
耳鼻咽喉 | 232篇 |
儿科学 | 1732篇 |
妇产科学 | 394篇 |
基础医学 | 6129篇 |
口腔科学 | 884篇 |
临床医学 | 4694篇 |
内科学 | 10181篇 |
皮肤病学 | 1094篇 |
神经病学 | 2400篇 |
特种医学 | 778篇 |
外国民族医学 | 4篇 |
外科学 | 3798篇 |
综合类 | 7018篇 |
现状与发展 | 4篇 |
一般理论 | 1篇 |
预防医学 | 2996篇 |
眼科学 | 577篇 |
药学 | 4235篇 |
27篇 | |
中国医学 | 3077篇 |
肿瘤学 | 1244篇 |
出版年
2024年 | 181篇 |
2023年 | 972篇 |
2022年 | 1223篇 |
2021年 | 2240篇 |
2020年 | 2070篇 |
2019年 | 1806篇 |
2018年 | 1751篇 |
2017年 | 1860篇 |
2016年 | 1990篇 |
2015年 | 1842篇 |
2014年 | 3306篇 |
2013年 | 3587篇 |
2012年 | 3154篇 |
2011年 | 3303篇 |
2010年 | 2455篇 |
2009年 | 2398篇 |
2008年 | 2326篇 |
2007年 | 2091篇 |
2006年 | 1836篇 |
2005年 | 1645篇 |
2004年 | 1288篇 |
2003年 | 1055篇 |
2002年 | 908篇 |
2001年 | 797篇 |
2000年 | 664篇 |
1999年 | 574篇 |
1998年 | 519篇 |
1997年 | 430篇 |
1996年 | 392篇 |
1995年 | 315篇 |
1994年 | 292篇 |
1993年 | 260篇 |
1992年 | 266篇 |
1991年 | 202篇 |
1990年 | 178篇 |
1989年 | 156篇 |
1988年 | 152篇 |
1987年 | 132篇 |
1986年 | 114篇 |
1985年 | 147篇 |
1984年 | 106篇 |
1983年 | 78篇 |
1982年 | 72篇 |
1981年 | 73篇 |
1980年 | 65篇 |
1979年 | 46篇 |
1978年 | 41篇 |
1977年 | 38篇 |
1976年 | 29篇 |
1974年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Lactate/H+ transport kinetics were determined by means of the pH-sensitive probe BCECF in sarcolemmal giant vesicles, obtained from
rat skeletal muscle, and related to variations in lactate/H+ transport capacity. Vesicle preparations were made from red and white muscles, mixed muscles, denervated muscles, muscles
of old rats and rats that had been subjected to high-intensity training, endurance training, repeated exposure to hypoxia,
and hypothyroid or hyperthyroid treatments. The lactate/H+ transport capacity of red muscles was greater than that of white muscles, and this difference was associated with a higher
maximal transport rate (V
max) in red muscles, whereas the K
m was similar in the two muscle types. High-intensity training and hyperthyroidism increased the lactate/H+ transport capacity by enhancing V
max without affecting K
m. Similarly, a reduced transport capacity with old age and hypothyroidism was due to a decrease in V
max. The denervation-induced decline in lactate/H+ transport capacity resulted from both an increased K
m and a reduced V
max. The present data show that muscle type differences and most changes in the lactate/H+ transport capacity are mediated by modifications in V
max, which is expected to represent the number of membrane transporter molecules. K
m is unaffected by most treatments and appears to be independent of fibre type.
Received: 10 February 1998 / Received after revision: 21 April 1998 / Accepted: 24 April 1998 相似文献
82.
Image processing is a critical part of obtaining high-quality digital radiographs. Fortunately, the user of these systems does not need to understand image processing in detail, because the manufacturers provide good starting values. Because radiologists may have different preferences in image appearance, it is helpful to know that many aspects of image appearance can be changed by image processing, and a new preferred setting can be loaded into the computer and saved so that it can become the new standard processing method.Image processing allows one to change the overall optical density of an image and to change its contrast. Spatial frequency processing allows an image to be sharpened, improving its appearance. It also allows noise to be blurred so that it is less visible. Care is necessary to avoid the introduction of artifacts or the hiding of mediastinal tubes. 相似文献
83.
84.
J Rothrock M Patel P Lyden C Jackson 《Cephalalgia : an international journal of headache》1996,16(1):44-49
We compared data from 243 patients with episodic migraine (EM) and 132 patients with chronic daily headache (CDH). We divided the matter group into those with tension-type headache only (CDH Type 1) and those with headaches having migrainous features (CDH Types 2+3) and compared each with the EM group and all three groups with one another. CDH Type l patients differed from those in the other groups by virtue of gender (more often male) and mean age at headache onset (older). The CDH Types 2+3 and EM groups differed only in that the former were more likely to have undergone a brain-imaging study. These data suggest that CDH Type 1 may represent a distinct headache syndrome, while CDH Types 2+3 closely resemble episodic migraine. 相似文献
85.
86.
87.
The conversion of multiple whole blood donors to apheresis donors is a challenge since a rapidly expanding apheresis donor base could erode homologous collections. We addressed this concern with a plan to enhance apheresis recruitment as well as donations among homologous donors with types O and B blood. Focusing the donor's attention on blood type as it relates to type-specific product needs was the basis of our approach. A matrix was used to recruit the desired types for the desired procedures (whole blood, platelet/plasma apheresis). The matrix instructed donors of blood types O, A-, and B- to primarily give whole blood and to give apheresis as a secondary donation. Donors AB, A+, and B+ were primarily directed to apheresis donations, whole blood donation being secondary. A+ and O- donors only gave their secondary donation if they were at maximum donations with the primary donation. The collections by blood type in percentages for 12 months of 1992/93 for whole blood were O+ 38.9, 0- 7.3, A+ 29.5, A- 5.7, B+ 11.9, B- 2.1, AB+ 3.7, AB+ 0.7. For apheresis it was 0+ 36.2, 0- 6.7, A+ 33.0, A- 6.6, B+ 10.4, B- 1.2, AB+ 4.9, AB+ 1.0. In 1992/93, A+ and B+ apheresis collections as compared to total apheresis collections increased by 4.9% and 13.7%, respectively. For O group apheresis donations, a decrease of 2.5% was shown and A+ whole blood donations decreased by 5.35%. During the same period of time, total apheresis collections increased by 3,058 units. We demonstrated that integration of apheresis recruitment with type-specific whole blood recruitment yielded significant increases of type-specific products. 相似文献
88.
89.
For the past 10 years the alfa-hydroxyacids and the bovine collagen injection have been used for peeling and the correction of multiple skin diseases. Until now, such progressive achievement has occurred in separate parallels just like the indications that have been held distinct. However, the studies carried out in order to clarify the mechanical action of the two substances have shown a common and fundamental denominator: the stimulation of synthesis of the new collagen in the patient's skin. On the basis of these results and the existence of common clinical indications of the use of glycolic acid and collagen, the authors have worked out a protocol involving a combined and contemporary application in progressive steps. They developed the rationales of such protocol and analyzed the results of its application on a number of carefully selected patients for a clinical comparison and on a sample of rats for a histological comparison. They have concluded that the contemporary use of glycolic acid and bovine collagen is a simple and safe method whose synergy action leads to more intense and long-lasting effects than the ones observed in the isolated application of the two substances. The authors have also obtained interesting and significant histological results. 相似文献
90.
Morphologic characterization of osteoblast-like cell cultures isolated from newborn rat calvaria 总被引:4,自引:0,他引:4
Dominique Masquelier Béatrice Herbert Nadine Hauser Pascal Mermillod Edgard Schonne Claude Remacle Ph.D. 《Calcified tissue international》1990,47(2):92-104
Summary Two methods for harvesting osteoblast-like cell populations from newborn (10 days) rat calvaria were compared. The first one
consisted in culturing the periosteum-free bones and then trypsinizing the cells on the bone surface. The second one involved
the migration of the osteoblasts on glass fragments before trypsinization. Since the plating efficiency, the proportion of
alkaline phosphatase-positive cells, the population doubling time, and the calcium deposition were more adequate, the second
method was used to further characterize the behavior of the cultures. During the first week of culture, the cells featured
shapes similar to those observedin vivo on the surface of periosteum-free calvaria. They formed multilayers and, in the presence of ascorbic acid, synthetized an
organic matrix containing exclusively type I collagen. Later, small amounts of type III collagen appeared. The cells were
embedded in the matrix and progressively acquired the morphologic phenotype of osteocyte-like cells. The matrix mineralized
in the presence of β-glycerophosphate. The technique of dropinoculation (high concentration of cells in a small volume of
medium) promoted the multilayer formation and the achievement of large mineralized plates (about 1 cm2) in 3 weeks of culture. 相似文献