全文获取类型
收费全文 | 11381篇 |
免费 | 865篇 |
国内免费 | 87篇 |
专业分类
耳鼻咽喉 | 97篇 |
儿科学 | 279篇 |
妇产科学 | 254篇 |
基础医学 | 2145篇 |
口腔科学 | 155篇 |
临床医学 | 1246篇 |
内科学 | 2393篇 |
皮肤病学 | 224篇 |
神经病学 | 738篇 |
特种医学 | 453篇 |
外科学 | 1549篇 |
综合类 | 107篇 |
一般理论 | 2篇 |
预防医学 | 737篇 |
眼科学 | 132篇 |
药学 | 1073篇 |
中国医学 | 13篇 |
肿瘤学 | 736篇 |
出版年
2023年 | 67篇 |
2022年 | 70篇 |
2021年 | 166篇 |
2020年 | 144篇 |
2019年 | 210篇 |
2018年 | 259篇 |
2017年 | 222篇 |
2016年 | 221篇 |
2015年 | 252篇 |
2014年 | 330篇 |
2013年 | 449篇 |
2012年 | 570篇 |
2011年 | 519篇 |
2010年 | 310篇 |
2009年 | 321篇 |
2008年 | 481篇 |
2007年 | 512篇 |
2006年 | 443篇 |
2005年 | 413篇 |
2004年 | 393篇 |
2003年 | 335篇 |
2002年 | 318篇 |
2001年 | 323篇 |
2000年 | 321篇 |
1999年 | 315篇 |
1998年 | 163篇 |
1997年 | 132篇 |
1996年 | 138篇 |
1995年 | 104篇 |
1994年 | 135篇 |
1993年 | 107篇 |
1992年 | 240篇 |
1991年 | 241篇 |
1990年 | 274篇 |
1989年 | 294篇 |
1988年 | 268篇 |
1987年 | 222篇 |
1986年 | 231篇 |
1985年 | 243篇 |
1984年 | 179篇 |
1983年 | 160篇 |
1982年 | 94篇 |
1981年 | 88篇 |
1979年 | 110篇 |
1978年 | 82篇 |
1976年 | 70篇 |
1975年 | 74篇 |
1974年 | 99篇 |
1973年 | 91篇 |
1972年 | 69篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
B Kappel J Nielsen K Brogaard Hansen M Mikkelsen A J Therkelsen 《British journal of obstetrics and gynaecology》1987,94(1):50-54
The clinical significance of placental perforation and blood-stained amniotic fluid was studied in a group of 7238 Danish women undergoing mid-trimester amniocentesis for prenatal diagnosis under ultrasound guidance. The risk of spontaneous abortion was significantly increased both in pregnancies where the placenta was perforated and in those with blood-stained amniotic fluid. The risk estimate nearly doubled after placental perforation and more than doubled with a bloody tap. It is concluded that for women at relatively low risk of a fetal genetic abnormality, the indication of the amniocentesis should be reconsidered if a placental perforation is unavoidable. 相似文献
32.
B. W. Nielsen T. Bjerke T. M. E. Damsgaard T. Herlin K. Thestrup-Pedersen P. O. Schiøtz 《Inflammation research》1992,35(3-4):170-178
Increased osmotic pressure has been reported to cause non-cytotoxic histamine release (HR) from human basophils, as well as a potentation of HR induced by anti-IgE. In this study, the effects of hyperosmolar Na–K-acetate (300–600 mOsm/kg H2O) on HR was studied in washed human blood cells from newborns, adult volunteers and patients with severe atopic dermatitis. These three patient groups represesented 3 very distinct populations with respect to total plasma IgE content, medians were <0.2 IU/ml, 20.5 IU/ml and 2508 IU/ml, respectively. Increasing osmolarity to 500 mOsm/kg H2O caused little HR in the absence of other stimuli, whereas at 600 mOsm/kg H2O a significant increase in spontaneous HR was seen. The HR induced by anti-IgE and Concanavalin A, acting through the IgE-receptor, was increased approximately twofold at 500 mOsM/kg H2O. Responses were highly correlated to results at 300 mOsm/kg H2O. The use of 600 mOsm/kg H2O buffers caused a further increase in most, but not all blood samples. The potentiation of IgE-receptor-mediated HR when using hyperosmolar media was clearly independent of plasma IgE contents, and did not change the concentration-response to anti-IgE. In contrast, HR induced by the IgE-receptor-independent stimuli, Formyl-met-leu-phe and calcium ionophore A 23187, were not enhanced at all by incrased osmotic pressure. We conclude, that hyperosomolar media selectively enhance IgE-receptor-mediated HR. The use of hyperosmolar media may therefore be beneficial in a diagnostic application of washed blood HR assays use in allergy diagnosis. 相似文献
33.
A prospective, consecutive study of the aetiology of treatment-associated diarrhoea was conducted in 25 patients with disseminated germ cell cancer treated with intensive chemotherapy. Clostridium difficile was isolated in 45% of the diarrhoea episodes, which makes this species the most important bacterial pathogen in the development of clinically significant diarrhoea in this group of immunocompromised patients. 相似文献
34.
35.
J. Viby Mogensen M.D. Ph.D. E. Jensen M. Werner H. Kirkegaard Nielsen 《Acta anaesthesiologica Scandinavica》1988,32(1):45-48
A new method for monitoring neuromuscular function based on measurement of acceleration is presented. The rationale behind the method is Newton's second law, stating that the acceleration is directly proportional to the force. For measurement of acceleration, a piezo-electric ceramic wafer was used. When this piezo electrode was fixed to the thumb, an electrical signal proportional to the acceleration was produced whenever the thumb moved in response to nerve stimulation. The electrical signal was registered and analysed in a Myograph 2000 neuromuscular transmission monitor. In 35 patients anaesthetized with halothane, train-of-four ratios measured with the accelerometer (ACT-TOF) were compared with simultaneous mechanical train-of-four ratios (FDT-TOF). Control ACT-TOF ratios were significantly higher than control FDT-TOF ratios: 116 +/- 12 and 98 +/- 4 (mean +/- s.d.), respectively. In five patients not given any relaxant during the anaesthetic procedure (20-60 min), both responses were remarkably constant. In 30 patients given vecuronium, a close linear relationship was found during recovery between ACT-TOF and FDT-TOF ratios. It is concluded that the method fulfils the basic requirements for a simple and reliable clinical monitoring tool. 相似文献
36.
C Nielsen P C G?tzsche C M Nielsen J Gerstoft B F Vestergaard 《Antiviral research》1992,18(3-4):303-316
An assay based on production of HIV antigen in cultures of CD4+ lymphocytes infected 'in vitro' with cell-free virus was established. Using this assay it was possible to isolate, propagate and reliably determine the zidovudine susceptibility of HIV isolates from all patients despite differences in cellular tropism and syncytium inducing capacity. Using this assay, differences in zidovudine susceptibility of 52 serial isolates obtained from 16 patients before and after initiation of therapy were examined. HIV with a 10- to 100-fold reduced susceptibility to zidovudine were isolated from 13 patients as early as 4 months after initiation of therapy. Number of months of zidovudine treatment was strongly associated with development of viral resistance, and high CD4 cell counts tended to be associated with lower rates of development of resistance. That patients can harbor mixtures of virus strains with different susceptibility to zidovudine was confirmed by the differences in susceptibility between isolates obtained simultaneously from CD4+ lymphocyte and plasma, and by the differences in susceptibility between virus strains isolated from clones of CD4+ lymphocytes. 相似文献
37.
Reversal of postmenopausal vertebral bone loss by oestrogen and progestogen: a double blind placebo controlled study 总被引:3,自引:0,他引:3
N Munk-Jensen S Pors Nielsen E B Obel P Bonne Eriksen 《British medical journal (Clinical research ed.)》1988,296(6630):1150-1152
Because of uncertainty about the place of hormones in the treatment of postmenopausal bone loss vertebral and forearm bone loss was measured by absorptiometry in early postmenopausal women before and after continuous or sequential treatment with combined oestrogen and progestogen in a double blind placebo controlled trial. Treatment with hormones significantly reversed the vertebral bone loss. The net gain in vertebral bone density amounted to 6.4% a year with continuous supplementation and 5.4% a year with sequential supplementation; the net gain in forearm bone density was lower (3.6% with continuous and 3.7% with sequential supplementation). Before a policy of supplementation with hormones can be recommended to all postmenopausal women with the aim of reducing the incidence of vertebral crush fractures further studies with different doses and combinations of hormones, administered over several years, are needed. 相似文献
38.
Sanja Kezic J. B. Nielsen 《International archives of occupational and environmental health》2009,82(6):677-688
Skin is an important route of entry for many chemicals in the work place. To assess systemic uptake of a chemical in contact
with the skin, quantitative information on dermal absorption rates of chemicals is needed. Absorption rates are mainly obtained
from studies performed with intact, healthy skin. At the work place, however, a compromised skin barrier, although not necessarily
visible is common, e.g. due to physical and chemical damage. As reviewed in this article, there are several lines of evidence
that reduced integrity of the skin barrier may increase dermal absorption of chemicals in the occupational setting. An impaired
skin barrier might lead not only to enhanced absorption of a specific chemical, but also to entrance of larger molecules such
as proteins and nanoparticles which normally are not able to penetrate intact skin. In addition to environmental influences,
there is increasing evidence that some individuals have an intrinsically affected skin barrier which will facilitate entrance
of chemicals into and through the skin making these persons more susceptible for local as well for systemic toxicity. This
review addresses mechanisms of barrier alteration caused by the most common skin-damaging factors in the occupational settings
and the consequences for dermal absorption of chemicals. Furthermore, this review emphasizes the importance of maintained
barrier properties of the skin. 相似文献
39.
This paper introduces the design and implementation of a generic wireless and Real-time Multi-purpose Health Care Telemedicine system applying Bluetooth protocol, Global System for Mobile Communications (GSM) and General Packet Radio Service (GPRS). The paper explores the factors that should be considered when evaluating different technologies for application in telemedicine system. The design and implementation of an embedded wireless communication platform utilising Bluetooth protocol is described, and the implementation problems and limitations are investigated. The system is tested and its telecommunication general aspects are verified. The results showed that the system has (97.9 +/- 1.3)% Up-time, 2.5 x 10(-5) Bit Error Rate, 1% Dropped Call Rate, 97.4% Call Success Rate, 5 second transmission delay in average, (3.42 +/- 0.11) kbps throughput, and the system may have application in electrocardiography. 相似文献
40.
Truitt C Ellis Vance G Nielsen Marisa B Marques James K Kirklin 《Blood coagulation & fibrinolysis》2007,18(1):45-48
The alpha angle alpha (degrees) is a thrombelastographic measure of clot propagation. A parametric measurement of clot propagation [maximum rate of thrombus generation (MRTG), dynes/cm2 per s], however, has recently been utilized. Thus, the relationship of changes in alpha with changes in MRTG were determined. alpha and MRTG values obtained from 859 thrombelastograms was collected from nine studies. Data were analyzed and the relationship between alpha and MRTG defined with commercially available software. Additional comparisons were made retrospectively from whole-blood and plasma data obtained from 33 normal individuals. Data from the nine studies demonstrated that MRTG increased in an exponential fashion compared with increases in alpha (R2 = 0.88, P < 0.001). Whole-blood alpha values were in the range 66.7-74.7 whereas MRTG values were 5.5-10.8, and plasma alpha values were 65.1-77.9 with corresponding MRTG values of 3.5-12.0. Assessment of clot propagation utilizing MRTG provides a more parametric evaluation than the determination of alpha. While normal alpha values may vary by only 12-20%, MRTG values vary by approximately 200-300%. The MRTG should be progressively utilized to a greater extent in both laboratory and clinical settings to parametrically quantify clot growth kinetics with thrombelastography. 相似文献