全文获取类型
收费全文 | 2518篇 |
免费 | 148篇 |
国内免费 | 20篇 |
专业分类
耳鼻咽喉 | 24篇 |
儿科学 | 57篇 |
妇产科学 | 37篇 |
基础医学 | 250篇 |
口腔科学 | 35篇 |
临床医学 | 277篇 |
内科学 | 507篇 |
皮肤病学 | 134篇 |
神经病学 | 208篇 |
特种医学 | 316篇 |
外科学 | 325篇 |
综合类 | 23篇 |
一般理论 | 4篇 |
预防医学 | 214篇 |
眼科学 | 20篇 |
药学 | 90篇 |
肿瘤学 | 165篇 |
出版年
2021年 | 30篇 |
2020年 | 21篇 |
2019年 | 33篇 |
2018年 | 29篇 |
2017年 | 32篇 |
2016年 | 27篇 |
2015年 | 31篇 |
2014年 | 50篇 |
2013年 | 73篇 |
2012年 | 109篇 |
2011年 | 105篇 |
2010年 | 52篇 |
2009年 | 56篇 |
2008年 | 100篇 |
2007年 | 108篇 |
2006年 | 116篇 |
2005年 | 138篇 |
2004年 | 98篇 |
2003年 | 107篇 |
2002年 | 102篇 |
2001年 | 85篇 |
2000年 | 72篇 |
1999年 | 67篇 |
1998年 | 36篇 |
1997年 | 37篇 |
1996年 | 34篇 |
1995年 | 39篇 |
1994年 | 36篇 |
1993年 | 33篇 |
1992年 | 43篇 |
1991年 | 54篇 |
1990年 | 32篇 |
1989年 | 45篇 |
1988年 | 53篇 |
1987年 | 33篇 |
1986年 | 27篇 |
1985年 | 46篇 |
1984年 | 40篇 |
1983年 | 34篇 |
1982年 | 25篇 |
1980年 | 22篇 |
1979年 | 49篇 |
1978年 | 26篇 |
1977年 | 18篇 |
1976年 | 19篇 |
1974年 | 29篇 |
1973年 | 32篇 |
1971年 | 18篇 |
1970年 | 19篇 |
1968年 | 17篇 |
排序方式: 共有2686条查询结果,搜索用时 15 毫秒
61.
Use of Population‐based Data to Demonstrate How Waitlist‐based Metrics Overestimate Geographic Disparities in Access to Liver Transplant Care 下载免费PDF全文
D. S. Goldberg B. French G. Sahota A. E. Wallace J. D. Lewis S. D. Halpern 《American journal of transplantation》2016,16(10):2903-2911
Liver allocation policies are evaluated by how they impact waitlisted patients, without considering broader outcomes for all patients with end‐stage liver disease (ESLD) not on the waitlist. We conducted a retrospective cohort study using two nationally representative databases: HealthCore (2006–2014) and five‐state Medicaid (California, Florida, New York, Ohio and Pennsylvania; 2002–2009). United Network for Organ Sharing (UNOS) linkages enabled ascertainment of waitlist‐ and transplant‐related outcomes. We included patients aged 18–75 with ESLD (decompensated cirrhosis or hepatocellular carcinoma) using validated International Classification of Diseases, Ninth Revision (ICD‐9)–based algorithms. Among 16 824 ESLD HealthCore patients, 3‐year incidences of waitlisting and transplantation were 15.8% (95% confidence interval [CI] : 15.0–16.6%) and 8.1% (7.5–8.8%), respectively. Among 67 706 ESLD Medicaid patients, 3‐year incidences of waitlisting and transplantation were 10.0% (9.7–10.4%) and 6.7% (6.5–7.0%), respectively. In HealthCore, the absolute ranges in states' waitlist mortality and transplant rates were larger than corresponding ranges among all ESLD patients (waitlist mortality: 13.6–38.5%, ESLD 3‐year mortality: 48.9–62.0%; waitlist transplant rates: 36.3–72.7%, ESLD transplant rates: 4.8–13.4%). States' waitlist mortality and ESLD population mortality were not positively correlated: ρ = ?0.06, p‐value = 0.83 (HealthCore); ρ = ?0.87, p‐value = 0.05 (Medicaid). Waitlist and ESLD transplant rates were weakly positively correlated in Medicaid (ρ = 0.36, p‐value = 0.55) but were positively correlated in HealthCore (ρ = 0.73, p‐value = 0.001). Compared to population‐based metrics, waitlist‐based metrics overestimate geographic disparities in access to liver transplantation. 相似文献
62.
Joshua Halpern Sameer Mittal Keith Pereira Shivank Bhatia Ranjith Ramasamy 《Asian journal of andrology》2016,18(2):234-238
There are several options for the treatment of varicocele, including surgical repair either by open or microsurgical approach, laparoscopy, or through percutaneous embolization of the internal spermatic vein. The ultimate goal of varicocele treatment relies on the occlusion of the dilated veins that drain the testis. Percutaneous embolization offers a rapid recovery and can be successfully accomplished in approximately 90% of attempts. However, the technique demands interventional radiologic expertise and has potential serious complications, including vascular perforation, coil migration, and thrombosis of pampiniform plexus. This review discusses the common indications, relative contraindications, technical details, and risks associated with percutaneous embolization of varicocele. 相似文献
63.
64.
65.
巨噬细胞迁移抑制因子最初是由于能抑制体外巨噬细胞随机迁移而被发现,现在它作为一种重要的调节因子参与一系列炎症性疾病过程.我们最近发现,巨噬细胞迁移抑制因子的缺失使一些由炎症介质诱发的白细胞-内皮细胞相互作用减弱,提示巨噬细胞迁移抑制因子在炎症反应中起作用的机制之一是促进白细胞聚集.…… 相似文献
66.
Direct measurement of nitroxide pharmacokinetics in isolated hearts situated in a low-frequency electron spin resonance spectrometer: implications for spin trapping and in vivo oxymetry. 下载免费PDF全文
G M Rosen H J Halpern L A Brunsting D P Spencer K E Strauss M K Bowman A S Wechsler 《Proceedings of the National Academy of Sciences of the United States of America》1988,85(20):7772-7776
The pharmacokinetics of two nitroxides were investigated in isolated rat hearts situated in a low-frequency electron spin resonance spectrometer. The spin labels 2,2,3,3,5,5-hexamethyl-1-pyrrolidinyloxy and 3-carboxy-2,2,5,5-tetramethyl-1-pyrrolidinyloxy were chosen for their physiochemical analogy to the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) and its corresponding spin-trapped adduct, 2-hydroxy-5,5-dimethyl-1-pyrrolidinyloxy (DMPO-OH). The bioreductive rates of the two nitroxides were measured during constant perfusion as well as during ischemia and are discussed in terms of a two-compartment pharmacokinetic model. These data provide information necessary to the design and application of spin traps to detect oxy radicals during reperfusion of ischemic tissue and suggest the feasibility of monitoring free-radical processes in intact, functioning mammalian tissues by using a low-frequency electron spin resonance spectrometer. 相似文献
67.
Inhibition of concanavalin A-induced acute T cell dependent hepatic damage in mice by hypothyroidism
Haim Shirin Iris Dotan Moshe Papa Yoram Maaravi Husein Aeet Lillian Zaidel Zipora Matas Rafael Bruck Steven F Moss Zamir Halpern Ran Oren 《Liver international》1999,19(3):206-211
Abstract: Aims/Background: Concanavalin A (Con A) activates T lymphocytes and causes acute T-cell-mediated hepatic injury in mice. Decreased thyroid hormonal production is associated with a variety of immunological manifestations, including inactivation of macrophages with reduced TNF production and reduced soluble IL-2 receptors in the serum. We have recently shown that hypothyroidism prevents the development of cirrhosis and also minimizes hepatic damage in rats with fulminant hepatic failure. In the present study we examined the effects of hypothyroidism on a mouse model of Con A induced T cell-mediated acute hepatitis. Methods: Hypothyroidism was induced both medically (MMI, PTU) and surgically. Eight groups of 10 mice each were studied: euthyroid controls (2 groups: water, Con A) and hypothyroid (6 groups: MMI, PTU, Surgical, MMI-Con A, PTU-Con A, Surgical-Con A). Results: Hepatic inflammation was significantly decreased in each of the Con A treated hypothyroid groups of mice. The serum transaminases, TNF-α and IL-6 levels were significantly elevated in the Con A treated group while near normal levels were found in the hypothyroid Con A treated groups (mean±SE AST: 1499±18 vs 78±10 IU/1, p<0.001; TNF: 2500±250 vs 135± 15 pg/ml. p<0.001, IL-6: 12,200±300 vs 1260±140 pg/ml, p<0.001, respectively). Conclusions: Hypothyroidism, independent of the mode of induction, can effectively inhibit the development of acute T cell-mediated liver damage in mice. These results suggest that some decrease in thyroid function might have a role in the prevention of immune mediated liver diseases. 相似文献
68.
Fibronectin binding to thrombin-stimulated platelets: evidence for fibrin(ogen) independent and dependent pathways 总被引:2,自引:0,他引:2
Plasma fibronectin binds in a specific and saturable manner to thrombin- stimulated platelets. gamma-Thrombin stimulated 80% as much fibronectin binding to platelets as alpha-thrombin with conversion of less than or equal to 1% of platelet fibrinogen to fibrin. Afibrinogenemic and normal platelets bound similar quantities of fibronectin in the presence of calcium or magnesium-ethylene glycol tetra-acetic acid (EGTA). These observations indicate that fibronectin can interact with platelets without involvement of fibrin or fibrinogen. Nevertheless, two different effects of fibrin(ogen) on fibronectin binding were observed. First, exogenous fibrinogen inhibited fibronectin binding to thrombin-stimulated platelets. This inhibition was unidirectional, as fibronectin did not inhibit fibrinogen binding to ADP or thrombin- stimulated cells. Second, formaldehyde-fixed cells with surface- associated fibrin bound significant quantities of fibronectin. This interaction required calcium and did not occur on fixed cells with or without surface-bound fibrinogen. A portion of the ligand bound to fixed cells with surface-associated fibrin was modified to form a derivative with a molecular weight identical to that of the fibronectin subunit cross-linked to the alpha-chain of fibrin. This high mol wt derivative was also observed to a variable extent with living cells in the presence of magnesium or calcium but not in the presence of magnesium-EGTA. Thus, fibronectin binds to platelets by at least two mechanisms: (1) a fibrin(ogen)-independent pathway that requires divalent ions and is inhibited by exogenous fibrinogen; and (2) a fibrin-dependent pathway with an absolute calcium requirement. With nonaggregated, thrombin-stimulated platelets, the former pathway appears to predominate. 相似文献
69.
The Effect of Replacement of Methionine by Homocystine on Survival of Malignant and Normal Adult Mammalian Cells in Culture 总被引:5,自引:6,他引:5 下载免费PDF全文
Barbara C. Halpern Brian R. Clark Dorothy N. Hardy Richard M. Halpern Roberts A. Smith 《Proceedings of the National Academy of Sciences of the United States of America》1974,71(4):1133-1136
In tissue cultures of normal adult and malignant mammalian cells, homocystine has been substituted for methionine in a medium rich in folic acid and cyanocobalamin. Normal adult cells thrive. Three highly malignant cell types from three different species, including man, die. 相似文献
70.
M S Halpern J M England G C Kopen A A Christou R L Taylor Jr 《Proceedings of the National Academy of Sciences of the United States of America》1996,93(2):824-827
We have compared the tumorigenicity of two src oncogenes, v-src and c-src(527), whose respective protein products pp60v-src and pp60c-src(527) show a different spectrum of amino acid substitutions vis-à-vis the c-src protooncogene-encoded product pp60c-src. Whereas the extent of primary tumor growth induced by c-src(527) was quite similar in the two chicken lines tested, the extent of v-src-induced tumor growth showed a marked line dependence. As examined with a line of chickens that shows immune-mediated regression of v-src-induced tumors, a weaker tumor immunity, as correlated with a greater level of primary tumor growth, resulted from inoculation of c-src(527) DNA than of v-src DNA. These observations indicated that the v-src-specific amino acid substitutions define a major tumor antigenicity. That a separate src-associated antigenicity is also targetable by the tumor immune response followed from the finding that the level of protective immunity against the growth of c-src(527) DNA-induced tumors was augmented under conditions of the prior regression of v-src DNA-induced tumors. As this latter antigenicity may include one or more c-src(527)-encoded peptides that are equivalent to c-src-encoded self peptides, these observations suggest that a host tolerance to pp60c-src can be broken so as to permit a tumor immune response based on recognition of self peptides of pp60c-src(527). 相似文献