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   595篇
  免费   80篇
  国内免费   47篇
耳鼻咽喉   3篇
儿科学   22篇
妇产科学   3篇
基础医学   108篇
口腔科学   44篇
临床医学   96篇
内科学   122篇
皮肤病学   15篇
神经病学   12篇
特种医学   149篇
外科学   53篇
综合类   11篇
预防医学   16篇
药学   48篇
肿瘤学   20篇
  2022年   1篇
  2021年   8篇
  2020年   3篇
  2019年   4篇
  2018年   4篇
  2017年   2篇
  2016年   4篇
  2015年   11篇
  2014年   5篇
  2013年   13篇
  2012年   9篇
  2011年   12篇
  2010年   8篇
  2009年   9篇
  2008年   17篇
  2007年   36篇
  2006年   8篇
  2005年   13篇
  2004年   5篇
  2003年   14篇
  2002年   18篇
  2001年   17篇
  2000年   28篇
  1999年   38篇
  1998年   33篇
  1997年   39篇
  1996年   31篇
  1995年   31篇
  1994年   26篇
  1993年   27篇
  1992年   29篇
  1991年   20篇
  1990年   19篇
  1989年   26篇
  1988年   21篇
  1987年   13篇
  1986年   17篇
  1985年   22篇
  1984年   8篇
  1983年   8篇
  1982年   7篇
  1981年   10篇
  1980年   7篇
  1979年   4篇
  1978年   7篇
  1977年   14篇
  1976年   9篇
  1975年   4篇
  1971年   2篇
  1969年   1篇
排序方式: 共有722条查询结果,搜索用时 125 毫秒
51.
52.
We analyzed retrospectively 27 individuals with C-2, C-3 fractures, 8 of whom were treated with a Philadelphia collar rather than the more commonly used halo vest. Successful fusion without neurological deficit occurred in all cases whether treatment was by Philadelphia collar (n = 8), halo apparatus (n = 16), or prolonged bed rest (n = 3). There was an increase in subluxation in 3 patients in both the Philadelphia collar group and the halo apparatus group. However, 1 of the 3 in the collar group was uncooperative and discarded his collar during treatment. If he is excluded, the subluxation rate in the Philadelphia collar group is 27%; the rate in the halo group is 19%. The Philadelphia collar seems to be an acceptable means of stabilizing the neck in C-2, C-3 fractures, but one must consider the degree of cervical movement in the collar (as detected by dynamic x-ray films), patient reliability, and patient age. The presence of subluxation did not preclude successful fusion in either the Philadelphia collar or the halo vest groups.  相似文献   
53.
Responses to the synthetic terpolymer L-glutamic acid, L-lysine, L-tyrosine (GLT) in the mouse are controlled by H-2-1inked Ir-GLTgenes. (Responder × nonresponder) F(1) hybrid mice, themselves phenotypic responders, can be primed with GLT to develop specific helper cells capable of interacting with 2,4-dinitrophenyl hapten (DNP)-primed F(1) B cells in response to DNP-GLT. Unlike the indiscriminant ability of F(1) helper T cells for conventional antigens (i.e. not Ir gene-controlled), which can help B cells of either parental type (as well as F(1)) equally well, GLT-primed F(1) T cells can only provide help under normal circumstances for B lymphocytes of responder parent origin; they are unable to communicate effectively with nonresponder parental B cells (1, and the present studies). The present studies reveal, however, that the induction of a parental cell-induced allogeneic effect during priming of F(1) mice to GLT actually dictates the direction of cooperating preference that will be displayed by such F(1) helper cells for B cells of one parental type or the other. Thus, F(1) T cells, primed to GLT under the influence of an allogeneic effect induced by parental BALB/c cells, develop into effective helpers for nonresponder A/J B cells, but fail to develop effective helpers for responder BALB/c B cells, and vice-versa. In contrast, F(1) T cells, primed to GLT under the influence of an allogeneic effect induced by either parental type, display significantly enhanced levels of helper activity for B cells derived from F(1) donors. These results are interpreted to reflect the existence of two interdependent events provoked by the allogeneic effect: one event augments the differentiation of GLT-specific helper T cells belonging to the subset corresponding to the opposite parental type; this would explain the development of increased helper activity provided to partner B cells of opposite parental type (as well as of F(1) origin). The second event, we postulate, involves the production of responses against the receptors which normally self-recognize native cell interaction determinants; this form of anti-idiotype response is restricted against self- recognizing receptors of the same parental type used for induction of the allogeneic effect, hence explaining diminished helper activity of such F(1) cells for partner B lymphocytes of corresponding parental type.  相似文献   
54.
Bony malformations of the orbit and alterations to the soft tissue in Apert syndrome contribute to ophthalmic dysfunction. Recognised structural malformation of the sphenoid and ethmoid sinuses, together with corresponding deformities in the anterior and middle cranial base, are characteristic. Our aim was to explore the underlying structural components of disfigurement and the consequent development of the orbit in patients with Apert syndrome over time by studying 18 preoperative computed tomographic (CT) scans of affected patients and 36 scans from controls. Cephalometric measurements related to the orbit were collected, and analysed with Materialise software. The patients with Apert syndrome had larger than normal external orbital horizontal angles between the ages of 6 months and 2 years. The inside horizontal angle was narrower at 16.36° before 6 months, and continued to decrease into adulthood. The ethmoid and sphenoid side angles in affected patients consistently increased, starting at 7.93% and 14.68% of the external horizontal angle, respectively, during the first 6 months of age, and becoming 20.55% and 11.69%, respectively, in adulthood. In unaffected patients, both angles were less than 3% of the external horizontal angle overall. The orbital vertical angle also changed synchronously, with increasingly wide lateral orbits and shortened anteroposterior orbits. The anterior protrusion of the lateral orbital wall resulted from superior and posterior rotation of a curved, greater wing of the sphenoid, while the widened median orbital wall was caused by the widened ethmoid sinus. These resulted in bony deformities of the orbit, which predisposed to the visual impairments of Apert syndrome.  相似文献   
55.
The facial malformations of Crouzon syndrome involve the entire cranio-orbito-zygomatic region. The detailed sequence of changes in orbit, zygoma, and maxilla over time, the mutual influence among these three anatomical structures, and their relationship with the cranial base were studied to determine the sequence and timing of deformity. Preoperative CT scans of 36 patients with Crouzon syndrome (mean age 10.84 ± 14.70 years; 14 male, 22 female) and CT scans of 54 control subjects (mean age 8.53 ± 13.22 years; 29 male, 25 female) were divided into five subgroups by age: 0–6 months, 6 months–2 years, 2–6 years, 6–18 years, and 18–62 years. Craniofacial morphometric cephalometrics were analyzed using Materialise software. Crouzon orbit anteroposterior length was shorter before 6 months (P = 0.021) and remained shorter into adulthood (P < 0.001). Globe projection was greater across all age subgroups (P < 0.001), reaching a peak at 6 months to 2 years (P < 0.001). The increased medial orbital width was the most remarkable and persistent secondary deformity (P < 0.001). The zygoma anterior protrusion was retruded before 6 months of age (P < 0.001), but then improved gradually. The width of maxilla was greater by 24% in the Crouzon cohort (P < 0.001), with a difference of 16% before 6 months (P = 0.024), and was developed earlier than the shortened anteroposterior length. Crouzon high and shallow orbital walls are distinctive. Maxillary widening developed before the malformation of sphenoid. The anteroposterior position of zygoma is likely a principal deformity, rather than a reflection of the intrinsic shape of the bone.Level of Evidence: II  相似文献   
56.
While the precise incidence of androgenetic alopecia is unknown, it is universally acknowledged to be the most common hair problem in men. Balding is generally associated with ageing; consequently, the desire to prolong a youthful appearance inevitably leads to demands for effective treatments. Further, changing attitudes in modern society have resulted in people becoming concerned about their appearance and less tolerant about conditions that might be alleviated by medical intervention. The importance of hair loss upon quality of life has been underestimated by the medical profession. Clinicians failing to accept hair loss as an important medical problem ignore the real distress suffered by a significant proportion of those affected. New options for treatment that selectively target the metabolic pathways involved in the balding process are showing promise. The first generation of such drugs, Propecia, is now available in some countries and other molecules are currently under development.  相似文献   
57.

Summary

This study examined the effects of quercetin on spontaneously contracting portal veins isolated from healthy young adult male and female Wistar rats (250–300 g). Quercetin (10-7–10-4 M) always produced significant biphasic effects, comprising an initial brief stimulant effect (rise in basal tone), followed by a sustained, longer-lasting secondary relaxant (inhibitory) effect on the venous tissues. The initial brief contractions of the venous muscle preparations were not modified by preincubation of the tissues with prazosin (10-6 M), suggesting that the initial upsurge in basal tone and increases in contractile frequencies of the venous tissues were probably not mediated via alpha1-adrenoceptor stimulation. However, preincubation of the tissues with nifedipine (10-7 M) significantly suppressed (p < 0.05) or attenuated the initial stimulant effect of quercetin, suggesting that the flavonoid might be activating L-type voltage-dependent calcium channels. The vasorelaxant effect of quercetin was partially but not significantly (p > 0.05) inhibited by L-NAME (100 μM) or indomethacin (10 μM), suggesting that the vasorelaxant effect of the flavonoid was unlikely to be mediated via endothelium-dependent relaxing factor (EDRF), or through prostacyclin (PGI2) pathways. N-p-tosyl-l-phenylalanine-chloromethyl-ketone (TPCK, 3 μM) significantly (p < 0.01) antagonised quercetin-induced relaxations, suggesting that cAMP-dependent protein kinases might have contributed, at least in part, towards the vasorelaxant effect of quercetin on rat isolated portal veins.  相似文献   
58.
Purified CD34+ Lin- Thy+ stem cells do not contain clonal myeloma cells   总被引:6,自引:0,他引:6  
High-dose therapy with autologous marrow or peripheral blood stem cell (PBSC) rescue has been extensively applied in the treatment of multiple myeloma (MM) patients during the past 10 years resulting in improved event-free and overall survival when compared with standard chemotherapy. However, relapses are common and cure is unlikely in the majority of patients. Because both bone marrow and PBSCs are contaminated with myeloma cells it is conceivable that relapse after autotransplantation originates at least in part from autografted tumor cells. In this study, mobilized PBSCs were examined for the presence of myeloma cells based on immunophenotyping and sensitive polymerase chain reaction (PCR)-based techniques. In addition, CD34+ Lin- Thy+ stem cells were purified from mobilized PBSC harvests of 10 MM patients by sequentially using counterflow elutriation centrifugation, treatment with phenylalanine methylester, and flow sorting, using 5-parameter gating (propidium iodide, forward scatter, side scatter, CD34+ v Lin- and CD34+ v Thy+). Virtually all mobilized unsorted PBSC preparations contained myeloma cells in sufficient quantities (range, < 0.01 to > 10%) potentially causing a disease relapse. Stem cell purification led to an overall enrichment by about 50-fold in all 10 patients; approximately 90% of the final cell population expressed CD34+ Lin- Thy+ with no evidence of myeloma cell contamination based on flow cytometric analysis of CD38bright cells (< 0.1%). Quantitative PCR amplification of patient-specific complementarity determining region III (CDRIII) DNA sequences showed depletion of clonal B cells by 2.7 to 7.3 logs, with the highest log reduction noted in the samples initially containing the most tumor cells. Our results show that purification of CD34+ Lin- Thy+ cells depletes myeloma cells to undetectable levels from up to 10% present in unsorted PBSCs, thus offering a tool to investigate whether MM relapse after autotransplantation can be reduced markedly.  相似文献   
59.
Respiratory insufficiency in neuronopathic and neuropathic disorders   总被引:1,自引:0,他引:1  
Twenty-nine patients with a neuronopathic or neuropathic disorder were referred for assessment of respiratory insufficiency between 1978 and 1994. Diagnoses included spinal muscular atrophy (6), chronic idiopathic demyelinating neuropathy (4), Vialetto-van Laere syndrome (3), hereditary motor and sensory neuropathy (3) and a miscellaneous group (5). We also describe seven patients with Guillain-Barre syndrome (GBS) who required long-term ventilatory support for over 6 months to 7 years after the initial illness. Respiratory insufficiency occurred as a consequence of respiratory muscle weakness, impaired bulbar function and restrictive lung defects. In some groups presentation was with progressive nocturnal hypoventilation culminating in acute respiratory failure. Five patients with GBS or chronic idiopathic demyelinating neuropathy were weaned from ventilatory support up to 18 months after the initial illness. The remaining 24 patients required continuous or nocturnal ventilatory support using intermittent positive-pressure ventilation (13), negative pressure ventilation (4), nasal-mask-delivered intermittent positive-pressure ventilation (4), nasal-mask-delivered continuous positive-pressure ventilation (3), mouthpiece-assisted ventilation by day (2) and rocking bed (1). None have been weaned from support after a period of ventilation ranging from one month to 10 years. Eight patients have subsequently died.   相似文献   
60.
The decision about which metopic synostosis patients should undergo surgery remains controversial. Multiple measures for radiographic severity have been developed in order to determine the optimal criteria for treatment. The aim of this study was to perform an extensive craniomorphometric analysis of patients who underwent surgery for metopic synostosis to validate and compare the various severity scales developed for this non-syndromic craniosynostosis. A comparative morphometric analysis was performed using computed tomography scans of preoperative metopic synostosis patients (n = 167) and normal controls (n = 44). Measurements included previous and newly developed metopic severity indices. Volumetric and area analyses were used to determine the degree of anterior cranial area and potential volume restrictions. Of the severity indices measured, the frontal angle, endocranial bifrontal angle (EBF), adjusted EBF (aEBF), anterior cranial fossa angle, horizontal cone angle, and bitemporal/biparietal distance ratio were significantly different in the metopic subjects relative to controls overall. However, metopic index, orbital rim angle, foramen ovale distance, and cranial volume exhibited no significant difference from controls. Only the frontal angle and aEBF correlated with the changes in anterior cranial dimensions observed in metopic synostosis. In conclusion, the frontal angle and aEBF provide the most accurate measures of severity in metopic synostosis.  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