全文获取类型
收费全文 | 214211篇 |
免费 | 14351篇 |
国内免费 | 901篇 |
专业分类
耳鼻咽喉 | 2216篇 |
儿科学 | 5581篇 |
妇产科学 | 4314篇 |
基础医学 | 30611篇 |
口腔科学 | 5116篇 |
临床医学 | 20482篇 |
内科学 | 45087篇 |
皮肤病学 | 3789篇 |
神经病学 | 20473篇 |
特种医学 | 8646篇 |
外国民族医学 | 51篇 |
外科学 | 30902篇 |
综合类 | 2423篇 |
现状与发展 | 2篇 |
一般理论 | 217篇 |
预防医学 | 15862篇 |
眼科学 | 4361篇 |
药学 | 14944篇 |
2篇 | |
中国医学 | 406篇 |
肿瘤学 | 13978篇 |
出版年
2023年 | 996篇 |
2022年 | 1684篇 |
2021年 | 3785篇 |
2020年 | 2555篇 |
2019年 | 3674篇 |
2018年 | 4496篇 |
2017年 | 3388篇 |
2016年 | 3918篇 |
2015年 | 4527篇 |
2014年 | 6290篇 |
2013年 | 8977篇 |
2012年 | 13293篇 |
2011年 | 14022篇 |
2010年 | 8444篇 |
2009年 | 7793篇 |
2008年 | 12817篇 |
2007年 | 13638篇 |
2006年 | 13099篇 |
2005年 | 13198篇 |
2004年 | 12686篇 |
2003年 | 11909篇 |
2002年 | 11404篇 |
2001年 | 3621篇 |
2000年 | 3307篇 |
1999年 | 3544篇 |
1998年 | 2946篇 |
1997年 | 2340篇 |
1996年 | 2035篇 |
1995年 | 1930篇 |
1994年 | 1673篇 |
1993年 | 1690篇 |
1992年 | 2215篇 |
1991年 | 2166篇 |
1990年 | 1937篇 |
1989年 | 1910篇 |
1988年 | 1655篇 |
1987年 | 1664篇 |
1986年 | 1547篇 |
1985年 | 1491篇 |
1984年 | 1325篇 |
1983年 | 1209篇 |
1982年 | 1204篇 |
1981年 | 1139篇 |
1980年 | 974篇 |
1979年 | 986篇 |
1978年 | 748篇 |
1977年 | 754篇 |
1976年 | 636篇 |
1975年 | 663篇 |
1974年 | 663篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
201.
In contrast to the systolic blood pressure at the posterior tibial artery, the evaluation of pressure at the digital artery of the foot before and after exercise in patients with peripheral arterial disease is not well known. Twenty three patients with peripheral vascular disease were examined. The systolic pressure was measured by means of an ultrasound velocity detector at the brachial and posterior tibial artery. Digital artery pressure was determined with photoplethysmography. Pressures were measured before and within 5 and 10 minutes after a treadmill test. Ankle and toe index was calculated. At rest the toe index is lower than the ankle index and after a treadmill test the decrease in toe index occurs in parallel to the ankle index. 相似文献
202.
203.
M G Van Luijtelaar F G Wouterlood J A Tonnaer H W Steinbusch 《Synapse (New York, N.Y.)》1991,8(3):162-168
Degeneration of neurons in the central nervous system is associated with morphological changes. Previous observations made at the light microscopical level indicated degeneration of serotonin-immunoreactive (IR) fibers in the aged rat brain. In this study, a comparison at the ultrastructural level was made between serotonin-IR normal thin and aberrant swollen varicose fibers in the caudate-putamen complex of the aged rat. Ultrastructural features such as the size and content of the thin varicose fibers resembled those in the caudate-putamen complex of the young rat as reported by others. The aberrant profiles were swollen, reaching a size of 6 microns. Their vesicles varied in size and were no longer uniformly round. Moreover, distorted mitochondria and membrane-filled vacuolelike structures were a common feature of the aberrant profiles. These changes are indicative of a degenerative process and give further evidence that, whereas many serotonergic fibers are preserved at high age, other serotonergic fibers are degenerating in the caudate-putamen complex of the aged rat. 相似文献
204.
Peter T Ellison 《American journal of human biology》2005,17(1):113-118
The fetal origins hypothesis, or Barker hypothesis, is both stimulating and challenging for evolutionary human biologists. While evidence of a correlation between conditions around the time of birth and later health outcomes has been presented before, the more recent evidence of a connection between fetal growth and chronic disease risk later in life has attracted considerable attention among epidemiologists and human biologists. Several themes that are fundamental to human biology emerge from an engagement with the fetal origins hypothesis. Among them are the tension between concepts of pathology, constraint, and adaptation; the importance of a life history perspective that embraces the notion of trade-offs; the question of environmental predictability; and the mechanisms of energy mobilization and allocation. Bringing the insights of evolutionary biology to bear on the fetal origins hypothesis illustrates the value of the field now known as evolutionary medicine. 相似文献
205.
Costimulatory molecules of the B7 family regulate the activation of T lymphocytes. T cell activation is promoted by binding of B7 molecules to CD28 and inhibited by binding to CTLA-4 (CD152). The balance between positive signals through CD28 and negative signals through CTLA-4 is critical for the fate of the T cell and is subject to tight regulation. Recent in vitro and in vivo studies have significantly advanced our understanding of the function of the CTLA-4 receptor. The results of these experiments suggest that CTLA-4 is critical for the induction of self-tolerance, and that it may have distinct signaling functions in resting and activated T cells. In resting T cells, CTLA-4 crosslinking leads to cell-cycle arrest, whereas in activated T cells, CTLA-4 crosslinking induces apoptosis. In this article, we will review the physiologic functions of the CTLA-4 receptor. 相似文献
206.
Male subfertility induced by acute scrotal heating affects embryo quality in normal female mice 总被引:5,自引:0,他引:5
Jannes P; Spiessens C; Van der Auwera I; D'Hooghe T; Verhoeven G; Vanderschueren D 《Human reproduction (Oxford, England)》1998,13(2):372-375
The aim of this experiment was to design a suitable mouse model for male
subfertility in which to study the effect of decreased sperm quality on
embryo quality in vivo and in vitro. To achieve male subfertility, testes
of adult male mice were immersed in water at either 42 degrees C (heated)
or 33 degrees C (controls) during 20 min. Twenty-eight days after
treatment, all heat stressed males showed a significant decrease in
relative testis weight [384.7 mg in controls (286.7-460.6) versus 323 mg in
stress heated groups (117.9-405.6); P < 0.001], sperm concentration
[3.75 x 10(6)/ml (2.75-7.25) versus 1.00 x 10(6)/ml (0-4.00); P < 0.001]
and progressive sperm motility [57.5% (48.0-79.0) versus 42.5% (14.0-66.0);
P < 0.001]. Moreover, after mating to heat exposed males, not only the
number of pregnant females (20/22 versus 18/30) but also the weight of
their embryos [275.4 mg (78.7-339.4) versus 261.8 mg (68.1-339.0); P <
0.001] was significantly lower at 14.5 days post coitum when compared to
controls. Neither the number of resorption sites nor the number of viable
embryos per pregnant female was significantly different between groups.
Also, the in-vitro fertilization rate of oocytes, fertilized by spermatozoa
collected from heat stressed males, was significantly lower (44.9%; P <
0.0001) when compared to controls (65.1%; P < 0.0001). In conclusion,
the results of this study suggest that male subfertility induced by acute
scrotal heating may result in impaired sperm quality, reduced embryo weight
in vivo and decreased fertilization rate in vitro.
相似文献
207.
208.
209.
This report looks at outpatient treatment of nasopharyngeal inlet stenosis, a more commonly seen postoperative complication of uvulopalatopharyngoplasty (UPPP). It does not study the effectiveness of the UPPP for treatment of obstructive sleep apnea syndrome (OSAS). The authors evaluated six patients who had a UPPP for OSAS, all of whom developed stenosis in the nasopharyngeal inlet ranging from 14 mm to complete closure. Two patients had failed rotation flap repairs. The carbon dioxide laser was used to treat these patients in the office under a local anesthesia in a staged manner. We now have patients from 3 months to 12 months follow-up who have had stenosis treated successfully. We believe that the postoperative complication of nasopharyngeal inlet stenosis after UPPP can be treated in a safe and cost-effective manner in the office setting. 相似文献
210.
Jürgen Schlegel Beate Ullrich Gabriele Stumm Peter Gass Ina-Maria Harwerth Nancy E. Hynes Marika Kiessling 《Acta neuropathologica》1993,86(5):473-479
The present study investigated the expression of c-erbB-2 in 59 meningiomas, including different histological subtypes and anaplastic variants, by immunocytochemistry and molecular biological techniques. Immunohistochemistry using the monoclonal antibody FWP-51 directed against c-erbB-2-encoded oncoprotein gp185 demonstrated variable degrees of immunoreactivity in all meningiomas. The intensity of immunostaining correlated with the degree of expression as assessed by Western analysis in 28 meningiomas using polyclonal antiserum 21N. There was no correlation between the degree of expression and histological variants. Immunoreactivity of all menigiomas was distinctly less intense, however, than that of the human breast cancer cell line SK-BR-3, and slightly lower than that of brain metastases of breast and ovarian carcinomas that served as positive controls for both methods. By Southern analysis all meningiomas showed a single copy of the c-erbB-2 gene. Non-neoplastic arachnoid cap cells also exhibited c-erbB-2 expression and the degree of immunoreactivity was comparable with the majority of meningiomas. These data argue against an overexpression of c-erbB-2 in meningiomas, but rather indicate a cell-type-specific constitutive expression of the c-erbB-2 gene product in meningiomas and their putative progenitor cells. Since a subgroup of meningiomas is known to express progesterone receptors (PR), gp185 immunoreactivity was compared to the hormone receptor status using monoclonal antibody KD68. Fifty-six percent meningiomas showed PR immunoreactivity, but there was no statistically significant correlation with the degree of gp185 expression.This study was supported by a grant of the Tumorzentrum Heidelberg/Mannheim (M.K., No. 10028060) 相似文献