首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   896篇
  免费   54篇
  国内免费   19篇
耳鼻咽喉   3篇
儿科学   38篇
妇产科学   38篇
基础医学   75篇
口腔科学   30篇
临床医学   116篇
内科学   129篇
皮肤病学   6篇
神经病学   97篇
特种医学   126篇
外科学   60篇
综合类   17篇
预防医学   76篇
眼科学   2篇
药学   33篇
中国医学   2篇
肿瘤学   121篇
  2022年   3篇
  2021年   11篇
  2020年   6篇
  2019年   25篇
  2018年   18篇
  2017年   14篇
  2016年   18篇
  2015年   19篇
  2014年   19篇
  2013年   30篇
  2012年   40篇
  2011年   36篇
  2010年   42篇
  2009年   50篇
  2008年   46篇
  2007年   42篇
  2006年   34篇
  2005年   35篇
  2004年   25篇
  2003年   24篇
  2002年   19篇
  2001年   25篇
  2000年   16篇
  1999年   17篇
  1998年   32篇
  1997年   33篇
  1996年   27篇
  1995年   24篇
  1994年   25篇
  1993年   20篇
  1992年   13篇
  1991年   11篇
  1990年   14篇
  1989年   18篇
  1988年   21篇
  1987年   13篇
  1986年   19篇
  1985年   13篇
  1984年   8篇
  1983年   12篇
  1982年   13篇
  1981年   7篇
  1980年   7篇
  1979年   2篇
  1978年   4篇
  1976年   3篇
  1975年   8篇
  1974年   2篇
  1970年   2篇
  1941年   1篇
排序方式: 共有969条查询结果,搜索用时 11 毫秒
961.
Selective venous sampling (SVS) is a useful technique to localize a number of hormone-producing tumours, such as parathyroid tumours, when other imaging techniques are inconclusive. Typically, a 5 French selective single end-hole catheter and standard hydrophilic wire are utilized to access the required vessels and an attempt made to withdraw blood. However, most interventional radiologists are familiar with the difficulty and limited success in withdrawing venous blood through an end-hole catheter. We describe a simple, cheap and novel technique utilizing a micro-wire that we have developed in our interventional suite to overcome this common problem. Having reached the target site with the selective end-hole catheter, a Tuohy Borst adapter is attached to the catheter end. A 0.018-inch micro-wire is then inserted through the selective end-hole catheter such that the distal wire tip exits the distal catheter tip. The purpose of the micro-wire exiting the catheter is to both straighten the catheter tip to a position parallel to the vessel, allowing easier aspiration as well as physically preventing blockage of the catheter by the vein intimal wall collapse on suction. The 5-ml sample required for PTH assay is then successfully obtained via the Tuohy Borst adapter.  相似文献   
962.
ATP-binding cassette transporter ABCG2 [breast cancer resistance protein (BCRP)] is a member of the ABC transporter superfamily that actively extrudes xenotoxins from cells and is a major determinant of the bioavailability of many compounds. ABCG2 expression is strongly induced during lactation in the mammary gland and is related to the active secretion of drugs into the milk. The presence of drug residues and environmental pollutants in milk is an outstanding problem for human milk consumption and milk industrial processes, involving important risks to public health and the dairy industry. In cows, a single nucleotide polymorphism (SNP) in this protein has been described previously (Tyr581) and is associated with higher fat and protein percentages and lower milk yield. However, whether this amino acid substitution affects ABCG2-mediated drug transport in cows, including milk secretion, required further exploration. We cloned the two variants of bovine ABCG2 and evaluated the effect of this SNP on mitoxantrone accumulation assays performed in ovine primary fibroblasts transiently expressing either of the variants. It is interesting to note that statistically significant differences in activity between both variants were observed, and the Ser581 variant was related with an increased efflux activity. In addition, we demonstrated that genistein is a very good inhibitor of bovine ABCG2 and identified new inhibitors of the transporter, such as the macrocyclic lactones, ivermectin, and selamectin. Moreover, the inhibitory effect of these compounds on human and murine ABCG2 homologs was confirmed using transduced Marbin-Dabin canine kidney II cells. These findings may have important implications regarding the presence of drug residues in milk and drug interactions affecting the pharmacological behavior of ABCG2 substrates.  相似文献   
963.
964.
965.
Donoghue K, Mazzoncini R, Hart J, Zanelli J, Morgan C, Dazzan P, Morgan KD, Murray RM, Jones PB, Doody GA. The differential effect of illicit drug use on cognitive function in first‐episode psychosis and healthy controls. Objective:: Illicit drug use can result in impairment in cognitive function in healthy individuals. Individuals with a psychotic disorder also show a deficit in cognitive function. Drug use may simply contribute to the characteristic cognitive deficit found in psychosis or alternatively result in a ‘double deficit’. This study aims to investigate the association between drug use and cognitive function at the first‐episode of psychosis and in community‐matched controls. Method:: One hundred and seventy‐seven patients at the first episode of psychosis completed a battery of neuropsychological tests. Those that had used drugs in the previous year (n = 80) were compared with those who had not used drugs in the previous year (n = 97). A subsample of the first‐episode psychosis patients were compared with community‐matched controls (n = 110) according to drug‐use status. Results:: Patients with a first episode of psychosis who had used drugs performed equally to those who had not used drugs on neuropsychological tests. In contrast, healthy controls who had used drugs in the previous year performed worse on tests of executive function and working memory compared with those controls that had not used drugs. Conclusion:: There are differential associations of illicit drug misuse with cognitive function for first‐episode psychosis patients and healthy controls.  相似文献   
966.
背景:经高温处理的煅烧骨具有类似自然骨的连续微孔结构,良好的生物相容性和降解性。 目的:观察牛煅烧骨的生物相容性、细胞相容性及毒性。 方法:①细胞相容性实验:将牛煅烧骨与第3 代已诱导的Wistar大鼠骨髓间充质干细胞复合培养。②溶血实验:将煅烧骨浸提液、生理盐水与双蒸水加入兔血中。③凝血实验:将煅烧骨加入兔血浆中。④急性毒性实验:在昆明种小鼠尾静脉分别注射煅烧骨浸提液、生理盐水。⑤微核实验:在小鼠腹腔分别注射煅烧骨浸提液、生理盐水与环磷酰胺。⑥局部刺激性实验:将煅烧骨浸提液、生理盐水分别注射于兔两侧脊柱皮下。⑦热源检测实验:在兔耳静脉注射煅烧骨浸提液。⑧皮下植入实验:将煅烧骨材料植入Wistar大鼠背部皮下。 结果与结论:煅烧骨材料无细胞毒性,具有良好的细胞及血液相容性;对皮肤、肌肉无刺激作用;对心、肝、肾重要器官无毒性作用;皮下植入后对周围组织无刺激作用,能够部分降解吸收并被机体组织替代;无致热作用,对凝血功能无影响,对小鼠骨髓细胞无抑制及毒性作用。  相似文献   
967.
A patient who wished to be treated for infertility by intracytoplasmic sperm injection (ICSI) was referred to our group for assessment. Upon clinical examination, a ptosis (partial closure of the eyelid) was noted, and histology revealed ragged red fibres in the skeletal muscle. Southern blot analysis of spermatozoa and skeletal muscle revealed the presence of multiple mitochondrial DNA deletions. This kind of rearrangement may be of nuclear origin since three nuclear loci have been ascribed to multiple mitochondrial DNA deletions in humans. Since mitochondrial DNA is maternally transmitted, the use of ICSI was feasible. However, an alteration of nuclear gene product affecting the integrity of mitochondrial DNA, and thus sperm mobility, might be transmitted to the offspring with the risk of developing a mitochondrial DNA disease.   相似文献   
968.
969.
The major histocompatibility complex (MHC) Class I and II cell surface antigens responsible for the recognition of self vs non-self were studied in patients with documented Hirschsprung's disease. Monoclonal antibodies reactive with monomorphic determinants of human lymphocyte antigen (HLA)-A,B,C (Class I) and HLA-DR (Class II) were used to demonstrate immunohistochemically the expression of MHC antigens in 27 biopsy specimens from a variety of colorectal disorders. The rectal specimens examined from patients with Hirschsprung's disease showed an unexpected, marked elevation of Class II antigens with abnormal localization in the mucosa and lamina propria. This ectopic expression was not seen in any portion of the small or large bowel of patients who did not have Hirschsprung's disease. Furthermore, proximal normal colon of children with Hirschsprung's disease failed to show increased expression of Class II antigen. In an attempt to better define the effector arm at a cellular level, the distribution of helper T cells (CD4+), cytotoxic/suppressor T cells (CD8+) and natural killer cells (NK; CD16+) was examined in 5 cases. In Hirschsprung's disease, rectal infiltration of CD8+ and CD16+ cells was found, but not CD4+ cells. Ectopic expression of Class II antigen with increased numbers of rectal T cells and NK cells suggested that an early immunologic event may be causal in Hirschsprung's disease.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号