全文获取类型
收费全文 | 22895篇 |
免费 | 1642篇 |
国内免费 | 56篇 |
专业分类
耳鼻咽喉 | 232篇 |
儿科学 | 700篇 |
妇产科学 | 420篇 |
基础医学 | 2690篇 |
口腔科学 | 247篇 |
临床医学 | 3606篇 |
内科学 | 4400篇 |
皮肤病学 | 298篇 |
神经病学 | 2133篇 |
特种医学 | 650篇 |
外科学 | 3358篇 |
综合类 | 279篇 |
一般理论 | 43篇 |
预防医学 | 2303篇 |
眼科学 | 427篇 |
药学 | 1335篇 |
中国医学 | 52篇 |
肿瘤学 | 1420篇 |
出版年
2024年 | 34篇 |
2023年 | 235篇 |
2022年 | 459篇 |
2021年 | 966篇 |
2020年 | 510篇 |
2019年 | 753篇 |
2018年 | 891篇 |
2017年 | 640篇 |
2016年 | 672篇 |
2015年 | 743篇 |
2014年 | 1044篇 |
2013年 | 1238篇 |
2012年 | 1970篇 |
2011年 | 2014篇 |
2010年 | 1063篇 |
2009年 | 895篇 |
2008年 | 1528篇 |
2007年 | 1501篇 |
2006年 | 1303篇 |
2005年 | 1204篇 |
2004年 | 1174篇 |
2003年 | 1003篇 |
2002年 | 871篇 |
2001年 | 134篇 |
2000年 | 126篇 |
1999年 | 130篇 |
1998年 | 159篇 |
1997年 | 113篇 |
1996年 | 105篇 |
1995年 | 84篇 |
1994年 | 82篇 |
1993年 | 76篇 |
1992年 | 56篇 |
1991年 | 63篇 |
1990年 | 45篇 |
1989年 | 63篇 |
1988年 | 37篇 |
1987年 | 54篇 |
1986年 | 37篇 |
1985年 | 53篇 |
1984年 | 39篇 |
1983年 | 44篇 |
1982年 | 51篇 |
1981年 | 44篇 |
1980年 | 43篇 |
1979年 | 40篇 |
1978年 | 42篇 |
1977年 | 19篇 |
1976年 | 28篇 |
1975年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
1.
2.
C Edward Hoffler Kurt D Hankenson Joshua D Miller Sukhinderdeep K Bilkhu Steven A Goldstein 《Journal of orthopaedic research》2006,24(8):1687-1698
To understand in situ behavior of osteocytes, we characterized a model of osteocytes in their native bone matrix and demonstrated real-time biologic activity of osteocytes while bending the bone matrix. Using 43 male Sprague-Dawley rats, dumbbell-shaped explants were harvested from stainless steel femoral implants after 6-12 weeks and incubated in culture medium or fixed. Sixteen specimens were used to determine bone volume density (BV/TV), volumetric bone mineral density (BMD) and histology for different implantation periods. Osteocyte viability was evaluated by L-lactate dehydrogenase (LDH) activity in 12 cultured explants. Confocal microscopy was used to assess tracer diffusion in three explants and changes in osteocyte pH of a mechanically loaded explant. From 6 to 12 weeks, explant BV/TV and volumetric BMD trended up 92.5% and 101%, respectively. They were significantly and highly correlated. Tissues were uniformly intramembranous and all bone cell types were present. Explants maintained LDH activity through culture day 8. Diffusion at 200 microM was limited to 1,209 Da. Explants appeared capable of reproducing complex bone biology. This model may be useful in understanding osteocyte mechanotransduction in the context of a physiologically relevant bone matrix. 相似文献
3.
Scott S Auerbach Joshua G Dekeyser Matthew A Stoner Curtis J Omiecinski 《Drug metabolism and disposition》2007,35(3):428-439
The constitutive androstane receptor (CAR; NR1I3) regulates the expression of genes involved in xenobiotic metabolism. Alternative splicing of the human CAR gene yields an array of mRNAs that encode structurally diverse proteins. One form of CAR, termed CAR2, contains an additional four amino acids (SPTV) that are predicted to reshape the ligand-binding pocket. The current studies show a marked, ligand-independent, CAR2-mediated transactivation of reporters containing optimal DR-3, DR-4, and DR-5 response elements, and reporters derived from the natural CYP2B6 and CYP3A4 gene promoters. Overexpression of the RXRalpha ligand binding domain was critical for achieving these effects. CAR2 interaction with SRC-1 was similarly dependent on the coexpression of RXRalpha. Mutagenesis of Ser233 (SPTV) to an alanine residue yielded a receptor possessing higher constitutive activity. Alternatively, mutating Ser233 to an aspartate residue drastically reduced the transactivation capacity of CAR2. The respective abilities of these mutagenized forms of CAR2 to transactivate a DR-4 x 3 reporter element correlated with their ability to interact with RxRalpha and to recruit SRC-1 in a ligand-regulated manner. Together, these results demonstrate a robust RXRalpha-dependent recruitment of coactivators and transactivation by CAR2. In addition, CAR2 displays novel dose responses to clotrimazole and androstanol compared with the reference form of the receptor while at the same time retaining the ability to bind CITCO. This result supports a hypothesis whereby the four-amino-acid insertion in CAR2 structurally modifies its ligand binding pocket, suggesting that CAR2 is regulated by a set of ligands distinct from those governing the activity of reference CAR. 相似文献
4.
BACKGROUND CONTEXT: Multiple lytic lesions of the spine usually represent metastatic or infectious disease processes. PURPOSE: To describe an extremely rare presentation of an uncommon disease process. STUDY DESIGN/SETTING: Case report/university hospital. METHODS: We describe the management of a patient who presented with a pathological fracture of C3 and multiple lytic lesions of the cervical spine. RESULTS: After reconstructive surgery, the final pathological diagnosis was fibrous dysplasia. CONCLUSION: Fibrous dysplasia is rarely seen in the cervical spine and may mimic other pathological processes. The surgical and medical management of spinal fibrous dysplasia is described. 相似文献
5.
Israel Liberzon Stephan F Taylor K Luan Phan Jennifer C Britton Lorraine M Fig Joshua A Bueller Robert A Koeppe Jon-Kar Zubieta 《Neuropsychopharmacology》2007,61(9):1030-1038
BACKGROUND: Functional neuroimaging studies have detected abnormal limbic and paralimbic activation to emotional probes in posttraumatic stress disorder (PTSD), but few studies have examined neurochemical mechanisms that underlie functional alterations in regional cerebral blood flow. The mu-opioid neurotransmitter system, implicated in responses to stress and suppression of pain, is distributed in and is thought to regulate the function of brain regions that are implicated in affective processing. METHODS: Here we examined the micro-opioid system with positron emission tomography and the micro-opioid receptor-selective radiotracer [11C] carfentanil in 16 male patients with PTSD and two non-PTSD male control groups, with (n = 14) and without combat exposure (n = 15). Differences in micro-opioid receptor binding potential (BP2) were detected within discrete limbic and paralimbic regions. RESULTS: Relative to healthy controls, both trauma-exposed groups had lower micro-opioid receptor BP2 in extended amygdala, nucleus accumbens, and dorsal frontal and insular cortex but had higher BP2 in the orbitofrontal cortex. PTSD patients exhibited reduced BP2 in anterior cingulate cortex compared with both control groups. Micro-opioid receptor BP2 in combat-exposed subjects without PTSD was lower in the amygdala but higher in the orbitofrontal cortex compared with both PTSD patients and healthy controls. CONCLUSIONS: These findings differentiate the general response of the micro-opioid system to trauma from more specific changes associated with PTSD. 相似文献
6.
Harold T. Kyriazi George E. Carvell Joshua C. Brumberg Daniel J. Simons 《Brain research》1996,712(2):325
Extracellular single-unit recordings were made in somatosensory cortical barrels of fentanyl-sedated rats. Whiskers were deflected singly or in paired combinations. lontophoretically-applied (−)-baclofen disproportionately reduced weak responses, and phaclofen disproportionately increased them, resulting in more tightly focused or more broadly focused receptive fields, respectively. Both drugs had only minor effects on surround inhibition. In light of previous findings, we conclude that GABAA and GABAB mechanisms both act to enhance spatial contrast, but that the former plays a much greater role in enhancing temporal resolution. 相似文献
7.
American Diabetes Association The initial draft of this paper was prepared by Rebecca G. Schafer MS RD ; Betsy Bohannon MS RD; Marion J. Franz MS RD; Janine Freeman RD; Alberta Holmes MS RD; Sue McLaughlin RD; Linda B. Haas RN; Davida F. Kruger MSN RN; Rodney A. Lorenz MD; Molly M.McMahon MD 《Journal of the American Dietetic Association》1997,97(1):52-53
8.
9.
10.