全文获取类型
收费全文 | 2061706篇 |
免费 | 150595篇 |
国内免费 | 4216篇 |
专业分类
耳鼻咽喉 | 27082篇 |
儿科学 | 68092篇 |
妇产科学 | 56195篇 |
基础医学 | 301439篇 |
口腔科学 | 59924篇 |
临床医学 | 183357篇 |
内科学 | 398918篇 |
皮肤病学 | 47540篇 |
神经病学 | 157410篇 |
特种医学 | 76968篇 |
外国民族医学 | 302篇 |
外科学 | 312314篇 |
综合类 | 45361篇 |
现状与发展 | 4篇 |
一般理论 | 626篇 |
预防医学 | 154335篇 |
眼科学 | 49328篇 |
药学 | 152713篇 |
7篇 | |
中国医学 | 5101篇 |
肿瘤学 | 119501篇 |
出版年
2019年 | 15839篇 |
2018年 | 23171篇 |
2017年 | 17599篇 |
2016年 | 19351篇 |
2015年 | 21950篇 |
2014年 | 30283篇 |
2013年 | 44676篇 |
2012年 | 61646篇 |
2011年 | 65413篇 |
2010年 | 38601篇 |
2009年 | 36143篇 |
2008年 | 61112篇 |
2007年 | 65107篇 |
2006年 | 65828篇 |
2005年 | 62731篇 |
2004年 | 60769篇 |
2003年 | 57737篇 |
2002年 | 55886篇 |
2001年 | 107063篇 |
2000年 | 109544篇 |
1999年 | 90514篇 |
1998年 | 23584篇 |
1997年 | 20669篇 |
1996年 | 20993篇 |
1995年 | 19988篇 |
1994年 | 18363篇 |
1993年 | 17023篇 |
1992年 | 68321篇 |
1991年 | 66682篇 |
1990年 | 64461篇 |
1989年 | 62002篇 |
1988年 | 56596篇 |
1987年 | 55407篇 |
1986年 | 52010篇 |
1985年 | 49462篇 |
1984年 | 36358篇 |
1983年 | 31004篇 |
1982年 | 17342篇 |
1979年 | 32671篇 |
1978年 | 22898篇 |
1977年 | 19411篇 |
1976年 | 18273篇 |
1975年 | 19602篇 |
1974年 | 23714篇 |
1973年 | 22654篇 |
1972年 | 21246篇 |
1971年 | 19812篇 |
1970年 | 18437篇 |
1969年 | 17337篇 |
1968年 | 16239篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
The response of single detergent treated bovine retinal pigment epithelial cells in culture to ATP was measured with an image analyser. The most pronounced contraction was produced by 1.0 mM ATP with most change taking place in the first 10 min. At 1 h the area had decreased by about 33%, perimeter 22% and maximum length 25%. By way of comparison rabbit skin fibroblasts had a decreased area of approximately 40%, perimeter 25% and maximum length 22%. Bovine aortic smooth muscle cells on the other hand decreased in area by 55%, perimeter 40% and maximum length 36%. It is hoped that this assay may be used to evaluate drugs which could counteract contractile events in proliferative vitreoretinopathy. 相似文献
992.
Penetrating keratoplasty was performed in 106 cases of post-inflammatory corneal opacity with vascularization. Donor material obtained post mortem was preserved in a moist chamber, MK-medium at 4 degrees C or in culture medium at room temperature. 55.7% of patients gained a useful vision after keratoplasty. The post-operative spherical error of refraction was found to be -1.4 +/- 3.6 D and the astigmatic error of refraction -3.3 +/- 2.0 D. The post-operative visual acuity was found to be 0.2 +/- 0.2. The ocular pathology associated with keratoplasty is discussed. 相似文献
993.
S de Bustros J T Thompson R G Michels T A Rice B M Glaser 《The British journal of ophthalmology》1988,72(9):692-695
We used vitreous surgery to remove idiopathic epiretinal membranes from the macular area in 70 consecutive cases. The abnormal tissue was successfully removed in each case. Vision improved postoperatively in 61 eyes (87%), remained unchanged in six eyes (9%), and worsened in three eyes (4%). However, at the time of final examination vision was improved in only 47 eyes (67%), primarily because of the occurrence or progression of nuclear sclerosis, which occurred in 38 of 60 phakic eyes (63%). Four preoperative factors were associated with final visual acuity of 20/60 or better: (1) initial vision of 20/100 or better, (2) shorter preoperative duration of blurred vision, (3) thin epiretinal membrane, and (4) absence of traction retinal detachment. 相似文献
994.
995.
S C Joseph 《Journal of urban health》1988,64(6):506-512
996.
997.
Integration and differentiation of human embryonic stem cells transplanted to the chick embryo. 总被引:3,自引:0,他引:3
Ronald S Goldstein Micha Drukker Benjamin E Reubinoff Nissim Benvenisty 《Developmental dynamics》2002,225(1):80-86
Human embryonic stem (ES) cells are pluripotent cells that can differentiate into a large array of cell types and, thus, hold promise for advancing our understanding of human embryology and for contributing to transplantation medicine. In this study, differentiation of human ES cells was examined in vivo by in ovo transplantation to organogenesis-stage embryos. Colonies of human ES cells were grafted into or in place of epithelial-stage somites of chick embryos of 1.5 to 2 days of development. The grafted human ES cells survived in the chick host and were identified by vital staining with carboxyfluorescein diacetate or use of a green fluorescent protein-expressing cells. Histologic analysis showed that human ES cells are easily distinguished from host cells by their larger, more intensely staining nuclei. Some grafted cells differentiated en masse into epithelia, whereas others migrated and mingled with host tissues, including the dorsal root ganglion. Colonies grafted directly adjacent to the host neural tube produced primarily structures with the morphology and molecular characteristics of neural rosettes. These structures contain differentiated neurons as shown by beta-3-tubulin and neurofilament expression in axons and cell bodies. Axons derived from the grafted cells penetrate the host nervous system, and host axons enter the structures derived from the graft. Our results show that human ES cells transplanted in ovo survive, divide, differentiate, and integrate with host tissues and that the host embryonic environment may modulate their differentiation. The chick embryo, therefore, may serve as an accessible and unique experimental system for the study of in vivo development of human ES cells. 相似文献
998.
999.
1000.
M. Wensing A. H. Penninks† S. L. Hefle‡ J. H. Akkerdaas§ R. van Ree§ S. J. Koppelman† C. A. F. M. Bruijnzeel-Koomen A. C. Knulst 《Clinical and experimental allergy》2002,32(12):1757-1762
BACKGROUND: The risk for allergic reactions depends on the sensitivity of individuals and the quantities of offending food ingested. The sensitivity varies among allergic individuals, as does the threshold dose of a food allergen capable of inducing an allergic reaction. OBJECTIVE: This study aimed at determining the distribution of minimum provoking doses of hazelnut in a hazelnut-allergic population. METHODS: Thirty-one patients with a history of hazelnut-related allergic symptoms, a positive skin prick test to hazelnut and/or an elevated specific IgE level, were included. Double-blind, placebo-controlled food challenges (DBPCFC) were performed with seven increasing doses of dried hazelnut (1 mg to 1 g hazelnut protein) randomly interspersed with seven placebo doses. RESULTS: Twenty-nine patients had a positive challenge. Itching of the oral cavity and/or lips was the first symptom in all cases. Additional gastrointestinal symptoms were reported in five patients and difficulty in swallowing in one patient. Lip swelling was observed in two patients, followed by generalized urticaria in one of these. Threshold doses for eliciting subjective reactions varied from a dose of 1 mg up to 100 mg hazelnut protein (equivalent to 6.4-640 mg hazelnut meal). Extrapolation of the dose-response curve showed that 50% of our hazelnut-allergic population will suffer from an allergic reaction after ingestion of 6 mg (95% CI, 2-11 mg) of hazelnut protein. Objective symptoms were observed in two patients after 1 and 1,000 mg, respectively. CONCLUSION: DBPCFCs demonstrated threshold doses in half of the hazelnut-allergic patients similar to doses previously described to be hidden in consumer products. This stresses the need for careful labelling and strategies to prevent and detect contamination of food products with hazelnut residues. 相似文献