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   8330篇
  免费   400篇
  国内免费   61篇
耳鼻咽喉   77篇
儿科学   176篇
妇产科学   67篇
基础医学   1023篇
口腔科学   112篇
临床医学   458篇
内科学   2562篇
皮肤病学   71篇
神经病学   646篇
特种医学   348篇
外科学   1450篇
综合类   16篇
一般理论   1篇
预防医学   248篇
眼科学   75篇
药学   489篇
中国医学   40篇
肿瘤学   932篇
  2023年   54篇
  2022年   99篇
  2021年   140篇
  2020年   98篇
  2019年   157篇
  2018年   164篇
  2017年   138篇
  2016年   185篇
  2015年   158篇
  2014年   215篇
  2013年   287篇
  2012年   449篇
  2011年   519篇
  2010年   275篇
  2009年   243篇
  2008年   415篇
  2007年   483篇
  2006年   474篇
  2005年   567篇
  2004年   532篇
  2003年   558篇
  2002年   577篇
  2001年   124篇
  2000年   116篇
  1999年   121篇
  1998年   155篇
  1997年   114篇
  1996年   102篇
  1995年   99篇
  1994年   104篇
  1993年   99篇
  1992年   105篇
  1991年   81篇
  1990年   97篇
  1989年   76篇
  1988年   86篇
  1987年   73篇
  1986年   58篇
  1985年   54篇
  1984年   49篇
  1983年   38篇
  1982年   26篇
  1981年   19篇
  1980年   25篇
  1979年   22篇
  1978年   14篇
  1977年   15篇
  1975年   17篇
  1974年   18篇
  1973年   14篇
排序方式: 共有8791条查询结果,搜索用时 15 毫秒
81.
BACKGROUND: Peritoneal calcification is an uncommon complication of continuous ambulatory peritoneal dialysis (CAPD), which is mainly observed in patients on long-term therapy. Although some asymptomatic patients must have microscopic calcification in their peritoneum, little information on this topic has been published. Recent studies have revealed active participation of adhesive/chemotactic protein osteopontin (OPN) in dystrophic calcification. METHODS: Peritoneal tissue was obtained by biopsy or at autopsy from 18 CAPD patients (median duration, 122 months), 5 control haemodialysis (HD) patients, and 3 pre-CAPD patients. The distribution of calcium deposits and OPN protein was determined by von Kossa staining and immunohistochemistry, respectively. Smooth muscle cells and macrophages were identified with anti-alpha smooth muscle actin (alpha-SMA) and anti-CD68 antibodies. RESULTS: Calcium deposits with various configurations were observed in specimens from 12 of the 18 CAPD patients. They included massive calcification facing the peritoneal cavity, scattered granular or crystalloid deposits in the submesothelial stroma, and oval-shaped deposits formed within hyalinized vasa. Most were present in highly sclerosed areas and accompanied by extracellular OPN precipitation. Cytoplasmic OPN was detected in infiltrating leukocytes, granulation tissue cells, fibroblast-like cells and mast cells. Computerized tomography examination also detected peritoneal calcification in seven of the CAPD patients. No calcium deposits or OPN staining was detected in control specimens. CONCLUSIONS:The results of our study suggest that microscopic peritoneal calcification is frequent in patients on CAPD for more than 10 years. Myofibroblast infiltration, OPN expression, calcium deposition, and associated OPN precipitation seem to be components of the peritoneal changes in such patients.  相似文献   
82.
BACKGROUND: This study assessed the calcium-activating mechanisms mediating glomerular arteriolar constriction by angiotensin II (Ang II). METHODS: Immunohistochemical and physiological studies were carried out, using antibody against transient receptor potential (TRP)-1 and an isolated perfused kidney model. RESULTS: Immunohistochemical experiments demonstrated that TRP-1 proteins were transcribed on both afferent and efferent arteriolar myocytes. In the first series of physiological experiments, Ang II (0.3 nmol/L) considerably constricted afferent (20.2 +/- 0.9 to 14.9 +/- 0.7 microm) and efferent arterioles (18.4 +/- 0.7 to 14.0 +/- 0.7 microm). The addition of nifedipine (1 micromol/L) restored decrements in afferent (to 20.0 +/- 0.8 microm) but not efferent arteriolar diameters. Further administration of SKF-96365 (100 micromol/L), a TRP channel blocker, reversed efferent arteriolar constriction (to 16.2 +/- 0.8 micromol/L). In the second group, although 2-aminoethoxydiphenyl borate (100 micromol/L), an inhibitor of inositol trisphosphate-induced calcium release (IP3CR), did not alter glomerular arteriolar diameters, it prevented Ang II-induced afferent arteriolar constriction and attenuated efferent arteriolar constriction (18.8 +/- 0.8 to 16.9 +/- microm). Subsequent removal of extracellular calcium abolished residual efferent arteriolar constriction (to 19.1 +/- 0.8 microm). CONCLUSIONS: Our data provide evidence that Ang II elicits IP3CR, possibly inducing a cellular response that activates voltage-dependent calcium channels on afferent arterioles. The present results suggest that Ang II-induced efferent arteriolar constriction involves IP3CR and calcium influx sensitive to SKF-96365.  相似文献   
83.
Symptomatic volar subluxation of the abductor pollicis longus and the extensor pollicis brevis tendons developed in a 29-year-old man after a sprain that occurred with the wrist in flexion and ulnar deviation. The extensor retinaculum, which forms the extensor compartment, was partially avulsed from its insertion on the radius. Palmar abduction and extension of the thumb with the wrist flexed produced subluxation of the tendons over the volar side of the radius ridge where the retinaculum forming the first extensor compartment attached. Nonoperative treatment including steroid injection and splinting was ineffective. Surgery was performed to reconstruct a new tendon restraint with part of the extensor retinaculum.  相似文献   
84.
Introduction Flat foot and/or metatarsal primus varus are the major causes of hallux valgus, and it is important to correct these deformities in order to prevent the recurrence of this condition. We demonstrate the clinical and radiological assessment of the correction of hallux valgus, metatarsal primus varus, and flat foot after proximal oblique-domed osteotomy of the metatarsus with distal soft tissue reconstruction. Materials and methods Twenty-seven feet of 22 patients with moderate or severe hallux valgus who had undergone proximal oblique-domed osteotomy were studied. After the adductor hallucis tendon was cut at the attachment of the proximal phalanx and at the sesamoid bone, the osteotomy was performed 3 cm dorsal-distal to the metatarsocuneiform joint to transfer distal fragment approximately 5 mm in the plantar direction, and rotated laterally decreasing the first–second intermetatarsal angle to 5 degrees. Results The mean AOFAS score was 54.1 ± 2.8 points at pre-operation and 92.8 ± 4.8 points at the most recent follow-up (P < 0.0001). Significant improvement was seen between the hallux valgus angle (P < 0.0001), first–second intermetatarsal angle (P < 0.0001), first–fifth intermetatarsal angle (P < 0.0001), talar pitch (P = 0.0032), and calcaneal plantar angle (P = 0.0327) before surgery and at one year after surgery. The average improvement of the talar pitch and calcaneal plantar angle was 2.6 ± 1.4 and 2.4 ± 1.5 degrees, respectively. Conclusion This study suggest that proximal oblique-domed osteotomy of the metatarsal as a surgical procedure for the treatment of moderate or severe hallux valgus with flat foot can be recommended to correct the longitudinal arch of the foot and the first–second intermetatarsal angle.  相似文献   
85.
A 68-year-old Japanese woman complaining of general fatigue and intermittent high fever was admitted to our hospital. Abdominal ultrasonography showed two tumors in the lateral segment of the liver, with soft tissue in the left hepatic vein that was considered to be a tumor embolus. A diagnosis of cholangiocarcinoma was made based on various radiological and laboratory examinations and therefore a surgical resection was performed. Microscopically, the tumor consisted of inflammatory cells, which had aggressively invaded the hepatic vein and Arantius' duct. The pathological diagnosis was inflammatory pseudotumor (IPT) that had invaded the hepatic vein. Although many cases of hepatic IPT have been previously reported, cases of hepatic IPT massively invading the hepatic vein are very rare as far as we could determine, based on a literature search. We herein report this case and discuss the diagnosis and treatment regarding hepatic IPT with massive venous invasion.  相似文献   
86.
Lee JE  Kim JS  Choi IH  Tagawa M  Kohsaka T  Jin DK 《Renal failure》2002,24(5):567-575
Hemolytic uremic syndrome (HUS) is the most common cause of acute renal failure in children worldwide. Shiga toxin (Stx) associated HUS, the most common type, is now known to be caused by Escherichia coli O157:7, which produces Stxl or the more potent, Stx2. Since the renal tubule is the major tissue affected in the course of HUS and Stx2 is known to be toxic to the renal tubular cells (RTC), we attempted to elucidate the mechanism of renal injury in HUS by studying the alteration of cytokines in the RTC evoked by Stx2. cDNA-array is a powerful tool for evaluating changes in the expression of a group of critical genes and also gives insights on the overview of the gene activation. In this study, we purified Stx2 from the E. coli O157:7, which was isolated from a typical diarrhea-associated HUS patient and then tried to compare the cytokine gene expression between the stimulated RTC and un-stimulated RTC using cDNA-array. Our results showed that one third of the examined cytokine genes were up regulated at least twice by the addition of Vtx2. These up-regulated genes represented the chemokines (macrophage related cytokines), fibrosis-related cytokine (TNF, PDGF) and leukemia inhibitory factors. However, the expression of IL-6, one of the pleiotropic cytokines, was significantly decreased and this finding was confirmed by northern analysis. Our results suggest that VT2 up-regulates the pro-inflammatory cytokines and fibrosis prone growth factors in RTC and that the inhibition of the activation of these cytokines may ameliorate the renal tubular injury in the HUS caused by E. coli O157:7.  相似文献   
87.
SUMMARY: A comparative immunohistological study was performed for the glomerular deposition of complements (C1q and C3c), fibrin/fibrinogen‐related antigen (FRA), the expression of intercellular adhesion molecule‐1 (ICAM‐1), and the infiltration of leucocytes bearing β2 integrins (leucocyte function associated antigen‐1 (LFA‐1), complement receptor 3 (CR3) and complement receptor 4 (CR4)) on renal biopsy specimens from 49 cases with Henoch‐Schoenlein purpura nephritis (HSPN), and 49 age‐matched cases with immunoglobulin A nephropathy (IgAN). the glomerular expression of ICAM‐1 was signifcantly correlated with the glomerular infiltration of leucocyte function associated antigen (LFA)‐1+ leucocytes in both diseases, and with that of CR3+ leucocytes in HSPN. the expression of ICAM‐1 was closely localized with the infiltration of LFA‐1+ leucocytes in the study with double immunostaining. the incidence and intensity of glomerular deposition of FRA were significantly higher in HSPN than in IgAN (P< 0.001), and those of C3c were significantly lower in HSPN than in IgAN (P< 0.001). the glomerular deposition of FRA was significantly correlated with the glomerular infiltration of CR4+ leucocytes in HSPN (P<0.05) but not in IgAN. In contrast, the glomerular deposition of C3c was significantly correlated with the glomerular infiltration of CR4+ leucocytes in IgAN (P<0.05), but not in HSPN. Studies with double immunostaining revealed a close association of CR4+ leucocytes with FRA deposition in HSPN and with C3c deposition in IgAN, respectively. the number of glomerular leucocytes bearing β2 integrins was significantly correlated with urinary protein at the time of renal biopsy in both diseases. These results suggested the differential roles of β2 integrins in the induction of glomerular injury in HSPN and IgAN. the ICAM‐1/LFA‐1 interaction may commonly be involved in the glomerular infiltration of leucocytes in both diseases. the ICAM‐1/CR3 interaction may be involved only in HSPN. Complement receptor 4 may function as a fibrin/fibrinogen receptor in HSPN, while CR4 may function as a complement receptor in IgAN.  相似文献   
88.
We report the case of a 58-year-old woman with low-grade astrocytoma, who developed massive intracranial hemorrhage as the first presentation of this disease, and become comatose and subsequently underwent an emergency craniotomy. A small amount of tumor-like tissue was observed on the wall of the hematoma cavity. Histological analysis of the resected specimen indicated diffuse astrocytoma [World Health Organization (WHO) grade II]. The patient was discharged without neurological deficits 2 weeks after the operation. A non-enhanced tumor-like nodule was observed on magnetic resonance imaging 3 months after the operation, which was monitored carefully but was not treated by adjuvant therapy. The tumor grew gradually, and a second operation was performed 3 years after the first, in which the tumor was completely resected. Histological analysis of the resected specimen again indicated diffuse astrocytoma (WHO grade II). Although rare, brain tumors, including low-grade astrocytoma, should be considered a possible cause of subcortical hemorrhage in patients without risk factors for intracranial hemorrhage.  相似文献   
89.
Cell-contracted collagen gels could provide rejection-free biomaterials for tissue engineering, but their application is limited by relatively low mechanical strength. We developed a special type I collagen construct (based on embedded fibroblasts) that was formed into a gel thread by using two anchors to constrain gel contraction in one direction. Each gel thread contained 2 mg of type I collagen and 1.0 x 10(6) fibroblasts, and had an initial volume of 3 mL. After 9 days in culture, this preparation was transformed into a thread-like construct measuring 26 x 2.3 x 0.21 mm. Investigation of the microstructure showed that the collagen fibrils longitudinally between two cells had most aligned with the direction of the constraint stress and had assumed higher density than those in the freely contracted controls. During culturing, the constraint stress first increased then decreased, with implications for the nature of the interaction between the embedded cells and collagen matrix. Under uniaxial tensile testing, the ultimate stress and material modulus increased by factors of 6 and 16, respectively, compared with controls, while the maximal strain decreased by 590%. Compared with the similar constructs in the literature, the thread gel was fabricated by means of a novel mold configuration so that it contracted to thread shape much faster, and more importantly, the constraint force was firstly reported in this article. The improved mechanical properties show that the gel thread could be an effective biomaterial for such tissue engineering applications as the fabrication of blood vessels, ligaments, and tendon grafts.  相似文献   
90.
Background: The purpose of the present study was to examine the expression of cell cycle regulators [p53, p21WAF1/CIP1 (p21), and Rb] and apoptosis related proteins Bax and Bcl-XL and to evaluate the relationship between their expressions and clinicopathological findings in patients with superficial squamous cell carcinomas of the esophagus.Methods: We immunohistochemically investigated the expression of p53, p21, Rb, Bax, and Bcl-XL in 79 patients with superficial esophageal carcinoma.Results: p21 overexpression was found in mucosal carcinoma (P = 0.05) and a high Bcl-XL score was observed for submucosal carcinoma (P = 0.03). The patients with high Bcl-XL score had more frequent lymphatic invasion and lymph node metastasis than did those with low Bcl-XL score (P < 0.05). Univariate analysis revealed significantly shorter survival in patients with high Bcl-XL expression than in those with low Bcl-XL expression, but Bcl-XL expression was not identified as an independent prognostic factor by multivariate analysis.Conclusions: Because Bcl-Xl expression correlated well with depth of tumor invasion, lymphatic invasion, and lymph node metastasis, examination of Bcl-XL expression will help to estimate the properties in superficial squamous cell carcinoma of the esophagus.  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