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   189078篇
  免费   1857篇
  国内免费   46篇
耳鼻咽喉   1237篇
儿科学   7098篇
妇产科学   3343篇
基础医学   19326篇
口腔科学   1774篇
临床医学   13532篇
内科学   33388篇
皮肤病学   1103篇
神经病学   17936篇
特种医学   9331篇
外科学   30205篇
综合类   2383篇
一般理论   6篇
预防医学   18767篇
眼科学   3028篇
药学   10246篇
中国医学   647篇
肿瘤学   17631篇
  2023年   78篇
  2022年   179篇
  2021年   290篇
  2020年   229篇
  2019年   325篇
  2018年   22209篇
  2017年   17550篇
  2016年   19798篇
  2015年   1274篇
  2014年   1257篇
  2013年   1382篇
  2012年   7846篇
  2011年   21874篇
  2010年   19278篇
  2009年   12001篇
  2008年   20221篇
  2007年   22475篇
  2006年   1323篇
  2005年   2955篇
  2004年   4114篇
  2003年   5025篇
  2002年   3083篇
  2001年   571篇
  2000年   682篇
  1999年   417篇
  1998年   392篇
  1997年   334篇
  1996年   221篇
  1995年   203篇
  1994年   182篇
  1993年   141篇
  1992年   149篇
  1991年   218篇
  1990年   231篇
  1989年   218篇
  1988年   160篇
  1987年   133篇
  1986年   119篇
  1985年   126篇
  1984年   80篇
  1983年   78篇
  1980年   70篇
  1975年   53篇
  1974年   55篇
  1938年   80篇
  1935年   65篇
  1934年   55篇
  1933年   65篇
  1932年   106篇
  1930年   52篇
排序方式: 共有10000条查询结果,搜索用时 25 毫秒
911.
Introduction  The aim of the present study was to evaluate the effects of erythropoietin (EPO) on the histopathology of testes after unilateral testicular torsion and detorsion. Materials and methods  Twenty-five male Sprague–Dawley rats weighing 120 g were used in this study. The rats were randomly divided into three groups, a sham group consisting of five rats and the other two groups consisting of ten rats. In group 1 (sham group), right orchiectomy with no additional intervention was performed. In group 2 (T/D group), torsion was created by rotating the testis 720° in a clockwise direction for 4 h. After a 4-h torsion period, the right testis was detorted and replaced into the scrotum for 4 h. After the torsion, 0.5 cc 0.9% NaCl solution was injected once and three times in a week (total 12 doses). In group 3 (T/D + erythropoietin; EPO group), the same surgical procedure was done as in group 1, but EPO 1,000 IU/kg was injected just before the detorsion and three times in a week. At the end of each procedure, bilateral orchiectomies were performed for the histopathological examinations in all groups. Results  We examined the testes weight, vascularization of the region between the seminiferous tubules, percentage of necrotic seminipherous tubules, and maturation of spermatogenesis in terms of necrosis, sertoli cells, maturation arrest of spermatogenesis, hypospermatogenesis, and normal spermatogenesis of torsioned testis tissues with and without EPO treatment. Extremely significant differences in testicular weight were observed in group 1 compared to groups 2 and 3 (P < 0.001). Conclusion  Administration of EPO significantly influenced the rescue of testicular function by preserving the intact seminiferous tubular morphology, lowering the percentage of necrotic seminipherous tubules, and significantly reducing histological damage (P < 0.05).  相似文献   
912.
This study was designed to determine the effect of molsidomine (MO), a precursor of nitric oxide (NO) donor, on hypoxia inducible factor alpha (HIF-1α) and Sonic hedgehog (Shh) levels considered to be involved in the development of testes ischemia/reperfusion (I-R) injury. Torsions were created by rotating ipsilateral testes 720° in a clockwise direction for 6 h and 1-h detorsion of the testis was performed. A sham operation was performed in group 1 (control, n = 7). In group 2 (I-R/Untreated, n = 7), following 6 h of unilateral testicular torsion, 1-h detorsion of the testis was performed. No drug was given. In group 3 (I-R/MO), after performing the same surgical procedure as in group 2, a NO donor MO was given at the starting time of reperfusion. In group 4 (I-R/L-NAME), after performing the same surgical procedure as in group 2, L-NAME was given at the starting time of reperfusion. Testes malondialdehyde (MDA) levels were determined as well as examining the testes histologically. Treatment of rats with MO produced a significant reduction in the levels of MDA and histopathological score compared to testes I-R groups. The Sonic hedgehog (Shh) expression in the basement membrane of the tubuli seminiferi, and sertoli and germinal cells in testicular tissue, were greatly increased in the I-R/MO group compared to groups 1, 2 and 4. Additionally, the HIF-1α expression in the interstitial spaces in testicular tissue were greatly increased in the I-R/MO group. The results suggest that MO has a protective effect against ischemia/reperfusion injury in rat testes and may affect Shh and HIF-1α signaling pathway.  相似文献   
913.
Background  Three-field lymph node dissection for thoracic esophageal cancer is associated with high morbidity and reduced quality of life after surgery. Consequently, minimized lymphadenectomy would be desirable, if appropriate. In the present study, we retrospectively analyzed the status of involved nodes and the direction of metastatic lymphatic flow from tumors into involved nodes to determine whether submucosal squamous cell esophageal cancers are potential candidates for minimized lymphadenectomy. Methods  We enrolled 199 patients who received esophagectomy with extensive lymph node dissection between 1989 and 2005 and retrospectively analyzed their prognoses, distribution of solitary metastatic lymph nodes, and the direction of metastatic lymphatic flow from the tumor, taking into consideration tumor location and depth. Results  Of these patients with submucosal cancers, 83% had 1 or 2 involved nodes, and their esophageal cancer-specific 5-year survival rate was 66%. Solitary lymph node metastasis did not occur in neck lymph nodes in lower thoracic submucosal esophageal cancers, and the direction of metastatic lymphatic flow from the tumor was almost always in one direction. By contrast, T2–4 cancers with 2–4 involved nodes had bidirectional metastatic lymphatic flow from the tumor. Conclusions  There was a difference in the status of lymph node metastasis and the direction of metastatic lymphatic flow from tumors into involved nodes between submucosal and T2–4 thoracic squamous cell esophageal cancers. This analysis may be useful for developing an approach to minimized lymphadenectomy for thoracic esophageal cancers.  相似文献   
914.
This paper reports a novel method for reconstructing the posterolateral structures [lateral collateral ligament (LCL), popliteus tendon, popliteofibular ligament] based on an anatomical study of a cadaveric dissection. The popliteus tendon was found to always be attached to the anterior–inferior portion of the femoral attachment site of the LCL, and the average distance from the origin of the popliteal tendon in the femoral side to that of the LCL was 18.5 mm (17–20). The insertion site of the LCL in the fibular side was located anterior–inferior-superficially and the popliteofibular ligament was inserted into the posterior–superior-deep portion around the styloid process. Two femoral tunnels and one fibular head tunnel were made at the proximal and distal portion of the anatomical insertion sites.  相似文献   
915.
Introduction  Recently, several publications investigated the rotational instability of the human knee joint under pivot shift examinations and reported the internal tibial rotation as measurement for instrumented knee laxity measurements. We hypothesize that ACL deficiency leads to increased internal tibial rotation under a simulated pivot shift test. Furthermore, it was hypothesized that anatomic single bundle ACL reconstruction significantly reduces the internal tibial rotation under a simulated pivot shift test when compared to the ACL-deficient knee. Methods  In seven human cadaveric knees, the kinematics of the intact knee, ACL-deficient knee, and anatomic single bundle ACL reconstructed knee were determined in response to a 134 N anterior tibial load and a combined rotatory load of 10 N m valgus and 4 N m internal tibial rotation using a robotic/UFS testing system. Statistical analyses were performed using a two-way ANOVA test. Results  Single bundle ACL reconstruction reduced the anterior tibial translation under a simulated KT-1000 test significantly compared to the ACL-deficient knee (P < 0.05). After reconstruction, there was a statistical significant difference to the intact knee at 30° of knee flexion. Under a simulated pivot shift test, anatomic single bundle ACL reconstruction could restore the intact knee kinematics. Internal tibial rotation under a simulated pivot shift showed no significant difference in the ACL-intact, ACL-deficient and ACL-reconstructed knee. Conclusion  In conclusion, ACL deficiency does not increase the internal tibial rotation under a simulated pivot shift test. For objective measurements of the rotational instability of the knee using instrumented knee laxity devices under pivot shift mechanisms, the anterior tibial translation should be rather evaluated than the internal tibial rotation. This study was supported in part by a grant of the German Speaking Association of Arthroscopy (AGA).  相似文献   
916.
Background  Patients with pancreatic tumors that induce hypoglycemia present with a myriad of symptoms. Laboratory testing can frequently result in data challenging to the clinician to confirm the biochemical diagnosis. Proinsulin, in addition to insulin levels, may be essential in evaluating and diagnosing an insulinoma. Methods  The objective of this case report is to demonstrate the potential importance of proinsulin levels in the evaluation of tumor-induced hypoglycemia. We report a 49-year-old woman with an unusual clinical presentation. Unlike many patients with tumor-induced hypoglycemia, her fasting glucose levels were fairly unimpressive, her insulin levels were undetectable during a prolonged fast, and she had elevated proinsulin levels. Results  The inpatient fast was remarkable for levels of serum glucose 53 mg/dl or higher, a serum insulin <2 uIU/ml, C-peptide 0.7–1.1 (nl 0.8–3.1 ng/ml), and proinsulin 29.2–36.8 pmol/l (nl ≤ 18.8 pmol/l). CT scanning of the abdomen revealed multiple pancreatic lesions. A laparoscopic distal pancreatectomy led to the removal of multiple neuroendocrine tumors, which stained only for proinsulin and not for other pancreatic tumor markers. Postoperatively, she normalized her biochemical serum studies and has remained symptom-free 2 years later. Conclusions  The measurement of proinsulin plays an important part in the diagnostic workup of neuroendocrine tumors causing hypoglycemia. These potentially malignant tumors can be treated adequately with minimally invasive surgery.  相似文献   
917.
This article reports an analysis of 75 consecutive lower limb amputees who developed painful neuroma requiring surgical excision after lower limb amputation following landmine explosions. This retrospective study analyses the results of 75 patients who were treated for painful neuroma after lower limb amputation following landmine explosions between the years 2000 and 2006. The average time period from use of prosthesis to start of symptoms suggesting neuroma was 9.6 months. The average time period from start of pain symptoms to neuroma surgery was 7.8 months. All clinically proven neuromas were surgically resected. In the mean follow-up of 2.8 years, all patients were satisfied with the end results and all were free of any pain symptoms. Painful stump with clinical diagnostic findings of neuroma described above may be regarded as neuroma without requiring any further imaging modalities and is an indication for surgery if conservative measures fail.  相似文献   
918.
Summary  The diagnosis of tethered cord syndrome (TCS) without typical conus medullaris symptoms and the radiological features such as a low set conus medullaris or dysraphic malformation is difficult. We report 11 year old identical twin brothers with TCS associated with the conus at the normal level. Their presenting symptom was progressive leg pain and both patients underwent surgical interruption of the filum terminale. The pain recurred in one patient treated surgically only after symptom became worse but resolved immediately in the other sibling treated promptly. We indicate the importance of early diagnosis and treatment of TCS to obtain excellent long-term outcome despite the absence of a low set conus or specific symptoms. Furthermore, when a twin or sibling of an affected person has neurological symptoms and the cutaneous signature of spinal dysraphism, radiological examination should be performed to establish the cause.  相似文献   
919.
Noggin is a major extracellular antagonist to bone morphogenetic proteins (BMPs) which binds to BMPs and blocks binding of them to BMP-specific receptors and negatively regulates BMP-induced osteoblastic differentiation. In this study, we investigated the effect of noggin silencing by transfection of small interfering RNA (siRNA) on BMP-induced osteoblastic differentiation in vitro and ectopic bone formation in vivo induced by recombinant human BMP-2 (rhBMP-2). Noggin mRNA expression was up-regulated in response to rhBMP-2 in C2C12 cells, a myoblastic cell line, in dose- and time-dependent fashion as determined by real-time RT-PCR assay. Silencing of noggin expression by transfection of noggin siRNA suppressed BMP-stimulated noggin expression, resulting in acceleration of BMP-induced osteoblastic differentiation. For in vivo noggin silencing, siRNA was injected locally into back muscles and transfected into local cells by electroporation, where rhBMP-2-retaining (5 μg) collagen disks had been surgically placed. The implants were harvested at 2 weeks after surgery from experimental and control group mice and analyzed by radiological and histological methods. As a result, bone mineral content of ossicles ectopically induced by rhBMP-2 was significantly increased by silencing of noggin. Our findings suggest that silencing of noggin enhances the osteoblastic differentiation of BMP-responding cells in vitro and new bone formation induced by rhBMP-2 in vivo by eliminating negative regulation of the effects of BMP. RNA interference might be useful for intensifying the effects of BMP in promoting new bone (callus) formation in repair of damaged bone.  相似文献   
920.
Aim  In general, arthroscopy is considered the “gold standard” for the evaluation of cartilage lesions. In this multicenter survey, we ascertained the general opinion of surgeons regarding arthroscopic cartilage diagnoses. Method  A total of 301 highly experienced arthroscopists (instructors of the AGA, the German-speaking society of arthroscopy) were contacted in writing with a request to complete the survey. Results  The data from 105 respondents (34.8% of those contacted) were used for the investigation. In the grading of the cartilage lesions, the Outerbridge classification was most frequently used (n = 87), followed by the ICRS protocol (n = 8) and the Insall score (n = 3). The majority (61%) of the arthroscopic surgeons felt that differentiation between healthy cartilage and low-grade cartilage lesions was simple. For differentiation between grade I and grade II lesions, and for differentiation between grade II and grade III lesions, 41.9 and 51.4%, respectively, thought that there was a “need for improvement”. In the case of grade IV lesions, 70.5% of the surgeons thought that the diagnosis was valid. The respondents also judged the utility of incorporating objective measurements (e.g., intraoperative biomechanical tests): 13.3% (n = 14) responded that such measurements would be “very useful” and 61.9% (n = 65) responded that they would be “somewhat useful”. Conclusions  Among surgeons, arthroscopy was not perceived to be as reliable as a “gold standard” for the diagnosis of cartilage lesions. The majority of experienced arthroscopists felt unsure of the results in general, or at least in some cases. A universal and definitive grading system for lesions appears to be needed. For questionable cases, measurement devices are needed for objective cartilage grading.  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