全文获取类型
收费全文 | 27209篇 |
免费 | 1793篇 |
国内免费 | 252篇 |
专业分类
耳鼻咽喉 | 426篇 |
儿科学 | 432篇 |
妇产科学 | 591篇 |
基础医学 | 3930篇 |
口腔科学 | 700篇 |
临床医学 | 2349篇 |
内科学 | 5173篇 |
皮肤病学 | 587篇 |
神经病学 | 2025篇 |
特种医学 | 1678篇 |
外科学 | 4349篇 |
综合类 | 309篇 |
一般理论 | 10篇 |
预防医学 | 1114篇 |
眼科学 | 663篇 |
药学 | 2346篇 |
1篇 | |
中国医学 | 271篇 |
肿瘤学 | 2300篇 |
出版年
2023年 | 163篇 |
2022年 | 384篇 |
2021年 | 709篇 |
2020年 | 389篇 |
2019年 | 665篇 |
2018年 | 719篇 |
2017年 | 593篇 |
2016年 | 689篇 |
2015年 | 1020篇 |
2014年 | 1261篇 |
2013年 | 1433篇 |
2012年 | 2130篇 |
2011年 | 2089篇 |
2010年 | 1299篇 |
2009年 | 1188篇 |
2008年 | 1628篇 |
2007年 | 1559篇 |
2006年 | 1459篇 |
2005年 | 1383篇 |
2004年 | 1241篇 |
2003年 | 1086篇 |
2002年 | 957篇 |
2001年 | 777篇 |
2000年 | 764篇 |
1999年 | 604篇 |
1998年 | 235篇 |
1997年 | 226篇 |
1996年 | 190篇 |
1995年 | 160篇 |
1994年 | 143篇 |
1993年 | 111篇 |
1992年 | 246篇 |
1991年 | 186篇 |
1990年 | 180篇 |
1989年 | 173篇 |
1988年 | 151篇 |
1987年 | 107篇 |
1986年 | 101篇 |
1985年 | 72篇 |
1984年 | 78篇 |
1983年 | 50篇 |
1982年 | 53篇 |
1981年 | 50篇 |
1980年 | 44篇 |
1979年 | 58篇 |
1978年 | 45篇 |
1977年 | 50篇 |
1974年 | 37篇 |
1972年 | 44篇 |
1971年 | 42篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
Wei-Jei Lee MD Jan-Show Chu MD Shyh-Jinn Houng MD Mei-Fu Chung BaN Shin-Ming Wang MD Dr. Kai-Mo Chen MD 《Annals of surgical oncology》1995,2(3):246-251
Background: Tumor growth and metastases require the development of new vessels (angiogenesis). Angiogenesis, assessed by microvessel count using immunocytochemical stain of endothelial cells, has been shown to predict metastases and correlate with early death. Recently developed color Doppler mapping can detect the “tumor flow signals” in breast cancer and help to distinguish it from benign lesions. The question is, does this tumor vascularization assessed by color Doppler mapping correlate with the angiogenesis assessed by immunocytochemistry? Methods: Eighty-four patients admitted for breast surgery were studied. The final diagnosis was made by pathology for 52 malignancies and 32 benign lesions. The color Doppler mapping of the breast lesion was made preoperatively. The following parameters were assessed: (a) vessel location (peripheral or central); (b) density of color Doppler signals; and (c) maximum systolic velocity. Tumor angiogenesis was assessed by microvessel count under light microscopy using the platelet/endothelial cell adhesion molecule antibodies (CD31) method. The correlation between maximum velocity and microvessel count of breast cancer was examined. The clinical significance of maximum flow velocity of breast cancer with various clinicopathologic factors was assessed. Results: Color signals were detected in 48 cases of 52 malignancies (92%). All tumors demonstrated signals at the periphery of the lesion but in only 13 (27%) were the signals detected within the tumor. Color signals were scored as + + or + + + in 44 (92%) patients. Pulsed wave blood flow was shown in all these 48 tumors, with maximum velocities varying from 4 to 36 cm/s. Among the 32 benign lesions, color signals were detected in 10 (31%) and all were peripheral and scored subjectively as +. Evaluation of these color Doppler mapping parameters shows no significant correlation with microvessel counts using CD31 monoclonal antibodies. However, there was a positive association (p<0.05) between nodal metastases and higher tumor flow velocity in T1 (<2 cm) breast tumors but not in larger tumors. Conclusion: Although the color Doppler mapping has been shown to be useful in distinguishing benign from malignant breast lesions, the intensity of signal and velocity of flow had no correlation with the extent of angiogenesis of breast cancer. The presence of high-flow tumor signal in early breast carcinoma is significantly associated with the presence of axillary lymph node metastases. 相似文献
142.
Regulation of type I collagen and interstitial collagenase mRNA expression in human dermal fibroblasts by colchicine and D-penicillamine 总被引:1,自引:0,他引:1
Sclerosis is a disease process in which idiopathic hardening occurs in the skin and/or internal organs as a result of the accumulation of type I collagen, induced mainly by transforming growth factor-beta. Colchicine and D-penicillamine are widely used for its treatment. Their effects are known to be due to post-translational down-regulation of type I collagen synthesis, with colchicine also up-regulating interstitial collagenase. To determine whether or not they have any pre-translational effect on type I collagen and MMP-1, and also to observe their effects on the action of TGF-beta, cultured neonatal foreskin fibroblasts were treated with colchicine and D-penicillamine, singly and together. The amount of type I collagen and MMP-1 mRNA were quantitated by Northern blot hybridization. Colchicine suppresses the basal level of type I collagen mRNA but minimally stimulates the mRNA expression of MMP-1, whereas D-penicillamine does not have any significant effects on either. Colchicine was also able to significantly suppress the TGF-beta-induced up-regulation of type I collagen mRNA expression. 相似文献
143.
Clinical trials of porcelain veneers for chairside colour modifications may require the use of a trial resin with various colours of tints. The bond strength effects of four different solvents used for removal of trial resin from etched porcelain specimens were investigated. Fifty-six porcelain specimens were fabricated, flattened by a metallurgically standard method, etched with hydrofluoric acid and silane treated. The specimens were divided into four groups at random. The trial resin material was cleaned with different solvents prior to bonding of a dual cure resin composite button. After bonding the specimens were stored in water at 37 degrees C for 7 days. Shear bond strength results were as follows: acetone (control) group, 12.9+/-2.9 MPa; ethanol group, 15.1+/-4.6 MPa; methanol group, 11.5+/-2.9 MPa; methylene chloride group, 11.3+/-2.4 MPa. No significant differences were measured (ANOVA, P>0.05). The results indicated that the resin-porcelain bond strengths were not affected by the type of solvent used to remove trial resin. This procedure is recommended for clinical cases when resin composite is used for the try-in of etched porcelain bonded restorations. 相似文献
144.
145.
RATIONALE AND OBJECTIVES: To evaluate the short-term effects of a new nitinol stent on canine arteries. METHODS: Eighteen nitinol mesh stents were placed in abdominal aortas, common iliac arteries, and renal arteries of six dogs. Angiography was performed to evaluate the patency rates and structural changes of arteries at 1 day, 3 weeks, 4 weeks, and 10 weeks after stent insertion. Gross and light microscopic examinations were performed after angiography. RESULTS: On angiography, the patency rate was 100%, and no thrombosis was observed. All side branches from stented segments were patent. The mean neointimal thickness over and between stent wires was 94 and 167 microns. No difference was found between the aorta and the small vessels. Histologically, the neointima was covered with endothelium and was composed of subintimal fibrosis with mild inflammation. CONCLUSIONS: The new type of nitinol mesh stent showed a high patency rate, with no thrombosis and relatively thin neointimal proliferation. 相似文献
146.
147.
A meta-analysis of randomized controlled trials of laparoscopic versus conventional appendectomy 总被引:18,自引:0,他引:18
BACKGROUND: Despite many randomized controlled trials, the merits of laparoscopic appendectomy remain unclear. A meta-analysis may provide insights not evident from any individual studies. DATA SOURCES: Systematic literature search yielded 17 trials (1,962 subjects) of true randomized design with usable statistical data comparing laparoscopic and conventional appendectomy in adults. The effect sizes for operating time, hospitalization, postoperative pain, return to normal activity, wound infection, and intra-abdominal abscess were calculated, using the random effects model to allow for heterogeneity. An estimate of the robustness of all positive findings was also calculated. RESULTS: Modest but statistically significant effect sizes were found for four of the six outcome measures. Laparoscopic appendectomy takes 31% longer to perform, but results in less postoperative pain, faster recovery (by 35%), and lower wound infection rates (by 60%). CONCLUSION: Laparoscopic appendectomy offers significant improvement in postoperative outcomes at the cost of a longer operation. 相似文献
148.
Sore throat is a common postoperative complaint, occurring most often following tracheal intubation. Factors such as tracheal-tube size and cuff design have been shown to be important causative factors. Routine tracheal intubation for elective surgical procedures can result in pathological changes, trauma and nerve damage which may also account for postoperative throat symptoms. Sore throat following the use of a laryngeal mask appears to be related to the technique of insertion but the contribution of intracuff pressure remains to be clarified. It would appear, however, that high intracuff pressure is associated with nerve palsies due to neuropraxia and nerve compression. Careful insertion techniques for both the tracheal tube and laryngeal mask are of paramount importance in the prevention of airway trauma and postoperative sore throat. 相似文献
149.
Chung CJ Fordham LA Barker P Cooper LL 《AJR. American journal of roentgenology》1999,173(6):1583-1588
OBJECTIVE: The objective of this original report is to describe the characteristic chest imaging findings in children with primary congenital pulmonary lymphangiectasia who survive infancy. CONCLUSION: In children with primary congenital pulmonary lymphangiectasia, increased interstitial markings decrease over time and increased hyperinflation is associated with persistent patchy areas of ground-glass opacity. 相似文献
150.
Kim MJ Park S Kim NK Kim MJ Chung JJ Outwater EK 《Journal of computer assisted tomography》1999,23(1):94-95
We report the transrectal ultrasonographic (TRUS) and endorectal surface coil MR findings for paragonimiasis involving the perirectal space. The patient presented with voiding difficulty. TRUS showed a well demarcated, oval-shaped hyperechoic mass in the perirectal space. On endorectal MR images, the lesion was depicted as a well defined cystic mass with homogeneous intermediate signal intensity on T1-weighted images and heterogeneous hyperintensity on T2-weighted images. Ectopic paragonimiasis can appear as a well defined cystic mass in the peritoneum and should be included in the differential diagnosis of cystic mass in the abdomen and pelvic cavity, including the perirectal space. 相似文献