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   9731篇
  免费   567篇
  国内免费   53篇
耳鼻咽喉   123篇
儿科学   192篇
妇产科学   124篇
基础医学   1240篇
口腔科学   223篇
临床医学   758篇
内科学   2519篇
皮肤病学   135篇
神经病学   602篇
特种医学   416篇
外科学   1494篇
综合类   49篇
一般理论   1篇
预防医学   287篇
眼科学   247篇
药学   743篇
中国医学   27篇
肿瘤学   1171篇
  2023年   123篇
  2022年   226篇
  2021年   413篇
  2020年   198篇
  2019年   242篇
  2018年   273篇
  2017年   201篇
  2016年   271篇
  2015年   236篇
  2014年   270篇
  2013年   367篇
  2012年   571篇
  2011年   647篇
  2010年   339篇
  2009年   235篇
  2008年   416篇
  2007年   452篇
  2006年   421篇
  2005年   432篇
  2004年   378篇
  2003年   374篇
  2002年   351篇
  2001年   220篇
  2000年   233篇
  1999年   233篇
  1998年   78篇
  1997年   86篇
  1996年   71篇
  1995年   74篇
  1994年   55篇
  1993年   53篇
  1992年   165篇
  1991年   139篇
  1990年   159篇
  1989年   147篇
  1988年   126篇
  1987年   126篇
  1986年   143篇
  1985年   88篇
  1984年   97篇
  1983年   72篇
  1982年   31篇
  1979年   57篇
  1978年   34篇
  1976年   30篇
  1975年   36篇
  1974年   43篇
  1972年   33篇
  1971年   37篇
  1970年   39篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.

Background

Intrahepatic and extrahepatic recurrence remains a significant problem for hepatocellular carcinoma (HCC). The aim of this study was to determine the usefulness of diffusion-weighted magnetic resonance imaging (DWI) for histological tumor grading and preoperative prediction of early HCC recurrence within 6 months of operation.

Methods

A total of 44 patients who had undergone hepatic resection for HCC (50 nodules) were reviewed retrospectively. DWI was performed within 30 days before hepatectomy, and apparent diffusion coefficients (ADCs) were measured using 2 methods: mean ADC and minimum-spot ADC. Relationships between ADCs and histological differentiation and between ADCs and early recurrence of HCC were analyzed.

Results

Mean ADC was significantly lower in poorly differentiated HCC (n = 18, 1.07 ± 0.15 × 10?3 mm2/s) than in moderately differentiated HCC (n = 29, 1.29 ± 0.21 × 10?3 mm2/s; P < .05). Minimum-spot ADC was significantly lower in poorly differentiated HCC (n = 18, 0.69 ± 0.19 × 10?3 mm2/s) than in well-differentiated HCC (n = 3, 1.15 ± 0.10 × 10?3 mm2; P < .01) or in moderately differentiated HCC (n = 29, 0.98 ± 0.18 × 10?3 mm2/s; P < .0001). Of 34 patients who were able to be observed for >6 months after resection, 9 showed early recurrence. Minimum-spot ADC was significantly lower in patients with early recurrence (n = 9, 0.64 ± 0.24 × 10?3 mm2/s) than in patients without early recurrence (n = 25, 0.88 ± 0.19 × 10?3 mm2/s; P < .05). On multivariate analysis, minimum-spot ADC was a significant risk factor for early recurrence (P < .05).

Conclusion

Quantitative measurement of ADC of HCC with magnetic resonance diffusion weighted imaging is a promising functional imaging tool in the prediction of histological grade and early recurrence before treatment.  相似文献   
102.
Background: The study hypothesizes that nitrous oxide (N2O) releases opioid peptide in the brain stem, which results in inhibition of [gamma]-aminobutyric acid-mediated (GABAergic) neurons that tonically inhibit the descending noradrenergic inhibitory neurons (DNIN), resulting in activation of DNIN. In the spinal cord, activation of DNIN leads to the release of norepinephrine, which inhibits nociceptive processing through direct activation of [alpha]2 adrenoceptor and indirect activation of GABAergic neurons through [alpha]1 adrenoceptor. Arising from this hypothesis, it follows that GABAergic neurons will modulate the antinociceptive effect of N2O in diametrically opposite directions at supraspinal and spinal levels. The authors have tested this tenet and further examined the effect of midazolam, a GABA-mimetic agent, on N2O-induced antinociceptive effect.

Methods: Adult male Fischer rats were administered muscimol (GABAA receptor agonist) intracerebroventricularly (icv), gabazine (GABAA receptor antagonist) intrathecally (intrathecal), or midazolam intraperitoneally (intraperitoneal). Fifteen minutes later, they were exposed to air or 75% N2O and were subjected to the plantar test after 30 min of gas exposure. In some animals administered with midazolam, gas exposure was continued for 90 min, and the brain and spinal cord were examined immunohistochemically.

Results: The N2O-induced antinociceptive effect, which was attenuated by icv muscimol, intrathecal gabazine, and intraperitoneal midazolam. Midazolam inhibited N2O-induced c-Fos expression (a marker of neuronal activation) in the pontine A7 and spinal cord.  相似文献   

103.
Okada S  Shikata K  Matsuda M  Ogawa D  Usui H  Kido Y  Nagase R  Wada J  Shikata Y  Makino H 《Diabetes》2003,52(10):2586-2593
Diabetic nephropathy is a leading cause of end-stage renal failure. Several mechanisms, including activation of protein kinase C, advanced glycation end products, and overexpression of transforming growth factor (TGF)-beta, are believed to be involved in the pathogenesis of diabetic nephropathy. However, the significance of inflammatory processes in the pathogenesis of diabetic microvascular complications is poorly understood. Accumulation of macrophages and overexpression of leukocyte adhesion molecules and chemokines are prominent in diabetic human kidney tissues. We previously demonstrated that intercellular adhesion molecule (ICAM)-1 mediates macrophage infiltration into the diabetic kidney. In the present study, to investigate the role of ICAM-1 in diabetic nephropathy, we induced diabetes in ICAM-1-deficient (ICAM-1(-/-)) mice and ICAM-1(+/+) mice with streptozotocin and examined the renal pathology over a period of 6 months. The infiltration of macrophages was markedly suppressed in diabetic ICAM-1(-/-) mice compared with that of ICAM-1(+/+) mice. Urinary albumin excretion, glomerular hypertrophy, and mesangial matrix expansion were significantly lower in diabetic ICAM-1(-/-) mice than in diabetic ICAM-1(+/+) mice. Moreover, expressions of TGF-beta and type IV collagen in glomeruli were also suppressed in diabetic ICAM-1(-/-) mice. These results suggest that ICAM-1 is critically involved in the pathogenesis of diabetic nephropathy.  相似文献   
104.
PURPOSE: The purpose of this study was to detail the pathomechanics and pathoanatomy of fracture dislocations of the ring finger and small finger carpometacarpal (CMC) joint by duplicating the pathomechanics of the fist blow. METHODS: A custom-made jig was used to position 20 fresh-frozen cadaver upper extremities in forearm neutral rotation, 90 degrees of elbow flexion, 20 degrees of wrist extension, and 20 degrees and 30 degrees of flexion at the ring and small finger CMC joint, respectively. First 7.7 kg of weight were dropped from a height of 0.76 m to 1.1 m to axially load the ring and small metacarpal (MC) heads through a custom-made apparatus. Fluoroscopic examination before and after loading, and detailed dissection after loading, were used to identify any osseous and/or ligamentous injuries. RESULTS: The most common fractures were a dorsal capitate fracture and a middle MC dorsal base fracture. The most common combinations of fractures were the dorsal capitate and dorsal hamate fractures. Multiple fractures often were identified in a number of locations including dorsally: the capitate, hamate, and index through small metacarpal bases, and volarly: the hook of the hamate and the middle through the small MC bases. CONCLUSIONS: The patterns of injuries encountered at the ring and small CMC joints can be explained by the direction and force of the applied load, position of the CMC joint at the time of loading, and the constraints imposed by specific CMC ligaments. A detailed analysis of the fracture patterns and associated ligament anatomy suggests that the typical ring and small carpometacarpal fracture dislocations are a more complex combination of fractures than identified by plain radiographs alone. The complexity of these injuries is greater than previously recognized and is most likely the result of a combination of axial load and shear stresses resulting in carpal fractures and ligament avulsions as well as fracture dislocations. This study suggests that computed tomography may be the preferred diagnostic imaging method for complete assessment of these injuries.  相似文献   
105.

Background

C1 lateral mass screw was widely used for fixation of the upper cervical spine. However, massive bleeding from the C1–2 venous plexus is sometimes encountered. In this study, we proposed an alternate method for C1 lateral mass screw insertion, which involves insertion of the screws caudally from the C2 nerve root to reduce bleeding from C1–2 venous plexus.

Methods

Seven patients with atlantoaxial lesions were included in this study. The mean age at surgery was 65.9 (34–82) years. The mean follow-up period was 23.1 (12–38) months. All patients underwent atlantoaxial fusion with C1 lateral mass screws, which were inserted caudally from the C2 nerve root. All screws were inserted using O-arm based navigation system. Operative time, blood loss, C2 nerve root injury and perioperative complications were investigated. The accuracy of C1 screws and bone union were evaluated using postoperative computed tomography.

Results

A total of 13 C1 lateral mass screws were inserted using this method. The mean operative time was 224 (144–305) min. The mean blood loss was 209 (100–357) g. One perioperative complication was observed, which was recurrent laryngeal nerve palsy. There were no vertebral artery or spinal cord injuries. No case of massive bleeding from the C1–2 venous plexus was observed. One patient complained of postoperative occipital neuralgia, which disappeared in 2 weeks. No malposition of C1 lateral mass screws was observed on postoperative computed tomography. Bone union was observed in all patients.

Conclusion

The C1 lateral mass screw insertion caudally from the C2 nerve root may become an alternate method for insertion of C1 screws.  相似文献   
106.
Background  We evaluated the prognostic value of the preoperative serum carcinoembryonic antigen (CEA) level in patients with colorectal cancer (CRC). Patients and Methods  The study group comprised 638 patients. The optimal cutoff value for the preoperative serum CEA level was determined. Predictive factors of recurrence were evaluated using multivariate analyses. The relapse-free time was investigated according to the CEA level. Results  All patients underwent potentially curative resection for CRC without distant metastasis, classified as stage I, II, or III. The optimal cutoff value for preoperative serum CEA level was 10 ng/ml. Elevated preoperative serum CEA level was observed in 92 patients. Multivariate analysis identified tumor–node–metastasis (TNM) stage and preoperative serum CEA level as independent predictive factors of recurrence. The relapse-free survival between CEA levels >10 ng/ml and <10 ng/ml significantly differed in patients with stage II and III. However, there was no significant difference in relapse-free survival between CEA levels >10 ng/ml and <10 ng/ml in patients with stage I. Conclusion  Preoperative serum CEA is a reliable predictive factor of recurrence after curative surgery in CRC patients and a useful indicator of the optimal treatment after resection, particularly for cases classified as stage II or stage III.  相似文献   
107.
Intravesical Bacillus Calmette-Guerin (BCG) therapy is commonly used against superficial urothelial carcinoma, especially carcinoma in situ (CIS). We report a case of tuberculous epididymitis that occurred during a course of intravesical BCG therapy. A 76-year-old man had received intravesical BCG therapy for multiple superficial bladder cancer and CIS in prostatic urethra after transurethral resection of bladder tumor (TUR-Bt). He recognized hard nodules in the left scrotum after 4 times intravesical BCG therapy. Skin fistula in scrotum occurred 5 months later. We performed left orchiectomy with scrotum skin resection. Histological diagnosis was tuberculous epididymitis. Postoperatively, he was administered chemotherapy consisting of isoniazid, refampin and ethambutol.  相似文献   
108.
A lobectomy with a resection of the pulmonary artery is less invasive than a pneumonectomy. However, it seems to be extremely difficult to perform this technique using video-assisted thoracic surgery with technical limitations because this technique is associated with an increased operative risk even in an open thoracotomy. Between April 2002 and December 2006, a curative video-assisted thoracic surgery lobectomy including a mediastinal lymphadenectomy was performed in 121 patients with primary non-small cell lung cancer. Five of those patients underwent a thoracoscopic lobectomy with the partial removal and reconstruction of the pulmonary artery. The causes of the pulmonary artery resection included two direct invasions of the artery, two invasions of the arterial branch, and one calcified lymphadenopathy involving the branch. No patients required a blood transfusion. No complications attributable to the technique or mortality were seen. No patients showed an abnormal blood flow through the reconstructed vessel. There were no local recurrences on the pulmonary artery. A video-assisted thoracic surgery lobectomy including a partial resection and reconstruction of the pulmonary artery is a complex procedure for patients with non-small cell lung cancer. It is feasible when all associated technical issues are properly addressed.  相似文献   
109.
Previously, we reported that allogeneic skin grafts were rapidly rejected by CD28 and CD40 ligand double deficient mice mediated by CD8+ T cells. These results indicated that some elements in addition to CD28- and CD40-mediated costimulation provide stimulatory signals for the activation of donor-specific CD8+ T cells. In this report, we investigated the role of inflammation associated with transplantation on costimulation-independent priming of CD8+ T cell during graft rejection. B6 RAG1 KO mice were transplanted with BALB/c-skin and adoptively transferred with syngeneic CD8+ T cells the same day or 50 days after transplantation. When blockade of CD28- and CD40-mediated costimulation failed to prevent acute rejection of freshly transplanted skin grafts, it efficiently delayed rejection of well-healed skin grafts. These results showed that factors associated with transplantation have essential roles in inducing costimulation blockade-resistant allograft rejection. Costimulation blockade failed to prevent acute graft-infiltration of NK cells and increasing expression of intragraft IL-12 and IL-15. These factors may trigger the graft-infiltration and priming of CD8+ T cells to induce costimulation blockade-resistant allograft rejection.  相似文献   
110.
This report presents a case of bilateral multiple sclerosing hemangiomas of the lung in a 73-year-old woman. A computed tomography (CT) scan of the chest showed a total of three well-defined small nodules in the right and left lower lobes of the lung. Because malignant metastatic lung tumors were highly suspected, a wedge resection of the left lower lobe was performed to obtain a definitive diagnosis. Histopathologically, two tumors of the left lower lobe were composed of epithelial-like cuboidal cells covering the surface of papillary protrusions and sheets of round to polygonal cells underneath the epithelial-like cells. The final diagnosis was that both tumors were sclerosing hemangiomas. After surgery the residual lesion of the right lower lobe was carefully followed by chest CT. The size of the right lung nodule did not change over the course of 9 years, and no new lesion has emerged.  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