全文获取类型
收费全文 | 316569篇 |
免费 | 12497篇 |
国内免费 | 760篇 |
专业分类
耳鼻咽喉 | 6968篇 |
儿科学 | 9538篇 |
妇产科学 | 9265篇 |
基础医学 | 48446篇 |
口腔科学 | 6932篇 |
临床医学 | 23745篇 |
内科学 | 66203篇 |
皮肤病学 | 8944篇 |
神经病学 | 27425篇 |
特种医学 | 12028篇 |
外国民族医学 | 13篇 |
外科学 | 48594篇 |
综合类 | 2800篇 |
现状与发展 | 3篇 |
一般理论 | 205篇 |
预防医学 | 17964篇 |
眼科学 | 10302篇 |
药学 | 16020篇 |
中国医学 | 250篇 |
肿瘤学 | 14181篇 |
出版年
2021年 | 2939篇 |
2020年 | 1813篇 |
2019年 | 2911篇 |
2018年 | 3570篇 |
2017年 | 2609篇 |
2016年 | 3086篇 |
2015年 | 6768篇 |
2014年 | 9022篇 |
2013年 | 13027篇 |
2012年 | 15182篇 |
2011年 | 15833篇 |
2010年 | 10750篇 |
2009年 | 10279篇 |
2008年 | 15374篇 |
2007年 | 16021篇 |
2006年 | 15958篇 |
2005年 | 15816篇 |
2004年 | 14903篇 |
2003年 | 12765篇 |
2002年 | 11078篇 |
2001年 | 2237篇 |
2000年 | 1854篇 |
1999年 | 2487篇 |
1998年 | 3478篇 |
1997年 | 3197篇 |
1996年 | 3240篇 |
1995年 | 3294篇 |
1994年 | 3168篇 |
1993年 | 3010篇 |
1992年 | 2800篇 |
1991年 | 2460篇 |
1990年 | 2205篇 |
1989年 | 2027篇 |
1988年 | 1934篇 |
1987年 | 1883篇 |
1986年 | 1928篇 |
1985年 | 1842篇 |
1984年 | 2270篇 |
1983年 | 2042篇 |
1982年 | 2694篇 |
1981年 | 2478篇 |
1980年 | 2359篇 |
1979年 | 1752篇 |
1978年 | 2016篇 |
1977年 | 1655篇 |
1930年 | 1698篇 |
1928年 | 1570篇 |
1926年 | 1613篇 |
1925年 | 1577篇 |
1924年 | 1626篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
Herbert Radner Yosuf El-Shabrawi Robert H. Eibl Oliver Brüstle Lukas Kenner Paul Kleihues Otmar D. Wiestler 《Acta neuropathologica》1993,86(5):456-465
Introduction into fetal rat brain cells of a replication-defective retroviral vector harboring v-Ha-ras and v-gag-myc rapidly causes the induction of highly malignant undifferentiated neuroectodermal tumors following transplantation into the brains of syngeneic hosts [Wiestler, et al. (1992) Cancer Res. 52: 3760–3767]. In the present study, we have investigated the modulating effect of the developmental stage of neural target cells and of the dose of the retroviral vector used in the grafting experiments. Exposure of fetal cells from embryonic day (E)12 or E14 produced a 100% incidence of malignant neuroectodermal tumors which led to the death of recipient animals after a median latency period of 32 days. A 100-fold reduction of the virus dose from 2.062×106 to 2.062×104 focus-forming units/ml resulted in a lower tumor incidence of 25%. Of six neural grafts exposed to v-Ha-ras and v-myc at E16, only one showed evidence of tumorigenesis (low-grade astrocytoma and hemangioma). All other transplants were morphologically normal for observation periods of 26 weeks, indicating a marked loss of transforming activity of ras and myc in more advanced stages of brain development. In retrovirus-exposed donor cells which caused the development of neural tumors in recipient rats, malignant transformation was also evident during culture in vitro, usually after 9–12 days. Oncogene complementation was also studied in the newborn rat brain. After microinjection of the retroviral vector into the brain at postnatal day (P)0, P1 and P3, 5 out of 20 animals (25%) developed a total of seven brain tumors. Histopathologically, three of these neoplasms were malignant neuroectodermal tumors which, in contrast to those induced in fetal brain transplants showed evidence of focal glial and/or neuronal differentiation. In addition, we observed one oligodendroglioma, two hemangiomas and a malignant hemangioendothelioma. These data indicate that neural precursor cells and endothelia of the rat brain represent the major target cells for the complementary action of ras and myc and that the use of target cells from later developmental stages (E16 and postnatal) leads to the induction of both primitive and more differentiated neoplasms.These studies were supported by the Fonds zur Förderung der wissenschaftlichen Forschung in Österreich (Erwin Schrödinger fellowship, JO501-MED), by the Swiss National Science Foundation and by the Cancer League of the Kanton of Zürich 相似文献
62.
63.
Dr. Michael Gosland Pharm.D. Dr. Bert Lum Pharm.D. Dr. Julia Schimmelpfennig Pharm.D. Dr. James Baker Pharm.D. Dr Michael Doukas M.D. 《Pharmacotherapy》1996,16(1):16-39
Cisplatin in combination with other cytotoxic agents is the backbone for a potential cure of testicular germ cell neoplasms and is a critical factor in the substantial activity observed in the treatment of small cell lung cancer, bladder cancer, and ovarian germ cell tumors. Resistance to cisplatin at the onset of treatment or at relapse limits its curative potential, however. Laboratory studies using both cells selected for cisplatin resistance by exposure to sublethal concentrations and biopsy specimens from patients' tumors provide insights for the potential mechanisms of resistance. The mechanisms identified in vitro include a complex and wide array of related and unrelated pathways such as alterations in cellular drug transport, enhanced DNA repair dependent and independent of signal transduction pathways, and enhanced intracellular detoxification such as glutathione and metallothionein systems. Studies of these mechanisms have identified a number of agents with known potential for administration to humans and that reverse cisplatin resistance in vitro; for example, reversal of cellular accumulation defects by dipyridamole; inhibition of DNA repair by hydroxyurea, pentoxifylline, and novobiocin; inhibition of the glutathione system by ethacrynic acid and buthionine sulfoximine; and inhibition of signal transduction pathways by cyclosporine, tamoxifen, and calcium channel-blocking agents. Current phase I clinical trials are focusing on the most effective doses and schedules to administer these agents in combination with cisplatin. Initial uncontrolled trials in limited numbers of patients suggest that the addition of modulators of cisplatin has the potential to reverse resistance in patients previously failing therapy. Another promising avenue for circumventing cisplatin resistance is the development of noncross-resistant platinum analogs. 相似文献
64.
Data on 232 members of a single pedigree, descended from two pairs of original parents, were made available to the participants of Genetic Analysis Workshop 8 (GAW8). In addition to information concerning age and sex, measurements for 10 quantitative traits and genotypes at 22 polymorphic marker loci were also provided for a subset of 193 of these family members. © 1993 Wiley-Liss, Inc. 相似文献
65.
66.
67.
68.
69.
Dr. Robert L. Geggel David R. Fulton Harvey L. Chernoff Richard Cleveland Thomas J. Hougen 《Pediatric cardiology》1987,8(4):279-283
Summary An infant girl is described who had cor triatriatum and partial anomalous pulmonary venous connection of the left pulmonary
veins to the coronary sinus, the first report of this combination of lesions. The infant also had a Dandy-Walker malformation
and multiple facial and intrathoracic hemangiomas. The cardiac diagnosis was made by two-dimensional echocardiography. Cardiac
catheterization and angiography confirmed the findings and also demonstrated a persistent left superior vena cava draining
to the coronary sinus. The infant underwent successful surgical repair. Partial anomalous pulmonary venous connection and
left superior vena cava not infrequently are associated with cor triatriatum. Although two-dimensional echocardiography is
sensitive for the detection of cor triatriatum, preoperative cardiac catheterization is necessary to identify unequivocally
systemic and pulmonary venous connections. 相似文献
70.
Unfractionated cytokines have been shown to induce in vitro proliferation of neonatal rat Schwann cells but the nature of the mitogen(s) is not known. A mixture of rabbit antibodies specific for recombinant interleukin-1α (IL-1α) and interleukin-1β (IL-1β) inhibited Schwann cell proliferation induced by unfractionated human cytokines whereas antibodies to interleukin-2 (IL-2) and control IgG did not. However, purified human IL-1 and recombinant human IL-1α or β did not induce Schwann cell proliferation on their own. 相似文献