全文获取类型
收费全文 | 3439篇 |
免费 | 271篇 |
国内免费 | 19篇 |
专业分类
耳鼻咽喉 | 11篇 |
儿科学 | 76篇 |
妇产科学 | 64篇 |
基础医学 | 550篇 |
口腔科学 | 30篇 |
临床医学 | 420篇 |
内科学 | 892篇 |
皮肤病学 | 31篇 |
神经病学 | 275篇 |
特种医学 | 61篇 |
外国民族医学 | 1篇 |
外科学 | 418篇 |
综合类 | 67篇 |
一般理论 | 8篇 |
预防医学 | 274篇 |
眼科学 | 53篇 |
药学 | 247篇 |
中国医学 | 23篇 |
肿瘤学 | 228篇 |
出版年
2023年 | 28篇 |
2022年 | 56篇 |
2021年 | 115篇 |
2020年 | 64篇 |
2019年 | 87篇 |
2018年 | 87篇 |
2017年 | 68篇 |
2016年 | 74篇 |
2015年 | 87篇 |
2014年 | 87篇 |
2013年 | 149篇 |
2012年 | 248篇 |
2011年 | 269篇 |
2010年 | 137篇 |
2009年 | 120篇 |
2008年 | 187篇 |
2007年 | 217篇 |
2006年 | 177篇 |
2005年 | 159篇 |
2004年 | 153篇 |
2003年 | 124篇 |
2002年 | 127篇 |
2001年 | 103篇 |
2000年 | 105篇 |
1999年 | 60篇 |
1998年 | 43篇 |
1997年 | 45篇 |
1996年 | 33篇 |
1995年 | 16篇 |
1994年 | 20篇 |
1993年 | 27篇 |
1992年 | 58篇 |
1991年 | 44篇 |
1990年 | 46篇 |
1989年 | 33篇 |
1988年 | 41篇 |
1987年 | 28篇 |
1986年 | 27篇 |
1985年 | 27篇 |
1984年 | 17篇 |
1983年 | 19篇 |
1982年 | 20篇 |
1981年 | 10篇 |
1980年 | 11篇 |
1979年 | 16篇 |
1978年 | 9篇 |
1976年 | 7篇 |
1975年 | 5篇 |
1974年 | 8篇 |
1970年 | 5篇 |
排序方式: 共有3729条查询结果,搜索用时 15 毫秒
121.
122.
The differentiation of Leydig cells, steroidogenesis, and the spermatogenetic wave in the testis of Necturus maculosus 总被引:3,自引:0,他引:3
The study of seminiferous tubule--Leydig cell interactions in relation to specific germ cell stages during the cycle of the seminiferous epithelium is extremely difficult in most mammalian species due to the continual presence of different spermatogenetic stages in the testis from the onset of puberty. The problem is also compounded by the uniform distribution of both seminiferous tubules and interstitial tissue throughout the entire testis. This difficulty can be circumvented, however, by studying certain species where there is a topographical distribution of germ cell stages within the testis. The urodele amphibian Necturus maculosus exhibits a breeding cycle during which a longitudinal wave of spermatogenesis occurs along the length of the testis, resulting in a spatial and temporal segregation of differentiating germ cells. Moreover, this topographical pattern of spermatogenesis is also reflected in the degree of development of adjacent Leydig cells. This anatomical arrangement allows distinct testicular regions to be obtained using a dissecting microscope. The isolated zones, containing germ cells and Leydig cells in various stages of development, were analyzed for 17 alpha-hydroxylase, C-17,20-lyase, and aromatase activities (key enzymes for the synthesis of androgens and estrogen), estrogen binding, and cytochrome P-450 content. Functional parameters were then correlated with the morphology of Leydig cells in the various zones observed by both light and electron microscopy. It was found that there existed a distinct correlation between the state of differentiation of the leydig cells, their steroidogenic potential, and the distribution of estrogen receptors. These results in Necturus indicate indicate in this species, at least, the steroidal microenvironment of different germ cell associations may be quite specific. 相似文献
123.
124.
Chen Y Mak AF Wang M Li J 《Journal of biomedical materials research. Part B, Applied biomaterials》2006,77(2):315-322
Collagen and apatite were coprecipitated as a composite coating on poly L-lactic acid (PLLA) in an accelerated biomimetic process. The incubation solution contained collagen (1 g/L) and simulated body fluid with 5 times inorganic ionic concentrations as human blood plasma. The coating formed on PLLA films and scaffolds after a 24-h incubation was characterized by using energy-dispersive X-ray spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy (SEM). It was shown that the coating contained carbonated bonelike apatite and collagen, which was similar in composition to natural bone. SEM showed a complex composite coating of submicron bonelike apatite particulates combined with collagen fibrils. It is expected that such biocomposite coating may better facilitate cell interaction and osteoconductivity. This work provided an efficient process to obtain bonelike apatite/collagen composite coating, which is potentially useful in bone tissue engineering. 相似文献
125.
Patrick Ying Kit Yue Nai Ki Mak Yuen Kit Cheng Kar Wah Leung Tzi Bun Ng David Tai Ping Fan Hin Wing Yeung Ricky Ngok Shun Wong 《Chinese medicine》2007,2(1):6-21
In Chinese medicine, ginseng (Panax ginseng C.A. Meyer) has long been used as a general tonic or an adaptogen to promote longevity
and enhance bodily functions. It has also been claimed to be effective in combating stress, fatigue, oxidants, cancer and
diabetes mellitus. Most of the pharmacological actions of ginseng are attributed to one type of its constituents, namely the
ginsenosides. In this review, we focus on the recent advances in the study of ginsenosides on angiogenesis which is related
to many pathological conditions including tumor progression and cardiovascular dysfunctions. 相似文献
126.
Sasaki T Wada T Kishimoto H Irie-Sasaki J Matsumoto G Goto T Yao Z Wakeham A Mak TW Suzuki A Cho SK Zuniga-Pflucker JC Oliveira-dos-Santos AJ Katada T Nishina H Penninger JM 《The Journal of experimental medicine》2001,194(6):757-768
The dual specificity kinases mitogen-activated protein kinase (MAPK) kinase (MKK)7 and MKK4 are the only molecules known to directly activate the stress kinases stress-activated protein kinases (SAPKs)/c-Jun N-terminal kinases (JNKs) in response to environmental or mitogenic stimuli. To examine the physiological role of MKK7 in hematopoietic cells, we used a gene targeting strategy to mutate MKK7 in murine T and B cells and non-lymphoid mast cells. Loss of MKK7 in thymocytes and mature B cells results in hyperproliferation in response to growth factor and antigen receptor stimulation and increased thymic cellularity. Mutation of mkk7 in mast cells resulted in hyperproliferation in response to the cytokines interleukin (IL)-3 and stem cell factor (SCF). SAPK/JNK activation was completely abolished in the absence of MKK7, even though expression of MKK4 was strongly upregulated in mkk7(-/-) mast cell lines, and phosphorylation of MKK4 occurred normally in response to multiple stress stimuli. Loss of MKK7 did not affect activation of extracellular signal-regulated kinase (ERK)1/2 or p38 MAPK. mkk7(-/-) mast cells display reduced expression of JunB and the cell cycle inhibitor p16INK4a and upregulation of cyclinD1. Reexpression of p16INK4a in mkk7(-/-) mast cells abrogates the hyperproliferative response. Apoptotic responses to a variety of stimuli were not affected. Thus, MKK7 is an essential and specific regulator of stress-induced SAPK/JNK activation in mast cells and MKK7 negatively regulates growth factor and antigen receptor-driven proliferation in hematopoietic cells. These results indicate that the MKK7-regulated stress signaling pathway can function as negative regulator of cell growth in multiple hematopoietic lineages. 相似文献
127.
Sara A. Wettergreen Jason Brunner Sunny A. Linnebur Laura M. Borgelt 《Medical teacher》2018,40(2):193-198
Objectives: The primary objective of this study was to compare faculty assessment and third year students' self-assessment of performance in clinical case discussions. The secondary objective was to evaluate if student characteristics influence self-assessments.Methods: This retrospective analysis compared faculty and student self-assessment scores for two clinical case discussions using Spearman’s correlation and Wilcoxon’s signed ranks test. Chi-squared test was used to compare frequency of faculty and student self-assessments indicating the highest possible rating for the pooled score and for each individual component. The pooled score included three individual components: level of engagement, quality of contribution, and professionalism.Results: Pooled faculty and student self-assessments correlated for both the first (r?=?0.41, p?0.001) and second (r?=?0.35; p?0.001) clinical case discussions. The frequency that faculty and student self-assessment ratings were the highest possible pooled score was similar for both the first (51.3% vs. 44.7%, respectively, p?=?0.25) and second (58.6% vs. 47.4%, p?=?0.05) clinical case discussions. Student characteristics (age, gender, and grade point average at graduation) did not influence self-assessments.Conclusions: Students’ self-assessment correlated with faculty assessment of performance during clinical case discussions. Increased use of self-assessments for professional development in pharmacy and other healthcare professional curricula should be considered. 相似文献
128.
Amanatullah DF Mallon ZO Mak WH Borys D Tamurian RM 《American journal of orthopedics (Belle Mead, N.J.)》2011,40(9):476-478
Osteoid osteoma is the most common bone-producing tumor that typically presents with "throbbing night pain" and that improves dramatically with use of low-dose salicylates. Few cases of pelvic osteoid osteoma have been reported, and most have involved patients younger than age 30. Surgical excision classically has been the treatment of choice, but, recently, less invasive modalities, including radiofrequency ablation, have begun to supplant surgical management of osteoid osteoma, resulting in a decrease in the need for definitive surgical diagnosis and treatment. We present a rare case of osteoid osteoma in the pelvis of a woman older than age 30. 相似文献
129.
130.
Bridges CB Lim W Hu-Primmer J Sims L Fukuda K Mak KH Rowe T Thompson WW Conn L Lu X Cox NJ Katz JM 《The Journal of infectious diseases》2002,185(8):1005-1010
In 1997, outbreaks of highly pathogenic influenza A (H5N1) among poultry coincided with 18 documented human cases of H5N1 illness. Although exposure to live poultry was associated with human illness, no cases were documented among poultry workers (PWs). To evaluate the potential for avian-to-human transmission of H5N1, a cohort study was conducted among 293 Hong Kong government workers (GWs) who participated in a poultry culling operation and among 1525 PWs. Paired serum samples collected from GWs and single serum samples collected from PWs were considered to be anti-H5 antibody positive if they were positive by both microneutralization and Western blot testing. Among GWs, 3% were seropositive, and 1 seroconversion was documented. Among PWs, approximately 10% had anti-H5 antibody. More-intensive poultry exposure, such as butchering and exposure to ill poultry, was associated with having anti-H5 antibody. These findings suggest an increased risk for avian influenza infection from occupational exposure. 相似文献