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   1691篇
  免费   73篇
  国内免费   24篇
耳鼻咽喉   23篇
儿科学   10篇
妇产科学   8篇
基础医学   176篇
口腔科学   13篇
临床医学   109篇
内科学   490篇
皮肤病学   37篇
神经病学   71篇
特种医学   41篇
外科学   477篇
综合类   21篇
预防医学   53篇
眼科学   13篇
药学   93篇
中国医学   4篇
肿瘤学   149篇
  2023年   6篇
  2022年   15篇
  2021年   24篇
  2020年   19篇
  2019年   31篇
  2018年   30篇
  2017年   21篇
  2016年   28篇
  2015年   22篇
  2014年   35篇
  2013年   38篇
  2012年   69篇
  2011年   79篇
  2010年   47篇
  2009年   33篇
  2008年   83篇
  2007年   90篇
  2006年   85篇
  2005年   73篇
  2004年   70篇
  2003年   76篇
  2002年   80篇
  2001年   72篇
  2000年   62篇
  1999年   88篇
  1998年   44篇
  1997年   24篇
  1996年   23篇
  1995年   15篇
  1994年   21篇
  1993年   20篇
  1992年   55篇
  1991年   46篇
  1990年   46篇
  1989年   31篇
  1988年   31篇
  1987年   28篇
  1986年   30篇
  1985年   22篇
  1984年   16篇
  1983年   9篇
  1982年   3篇
  1979年   10篇
  1978年   5篇
  1976年   3篇
  1971年   3篇
  1930年   2篇
  1926年   2篇
  1912年   2篇
  1907年   2篇
排序方式: 共有1788条查询结果,搜索用时 15 毫秒
101.
We investigated expression of ameloblastin and sheathlin, recently cloned enamel matrix proteins from the rat and pig, in forming enamel immunocytochemically and immunochemically, using region-specific antibodies. The results obtained from the rat and pig were essentially the same. Antibodies which recognize the N-terminal region stained the secretory machinery of the secretory ameloblast and the entire thickness of the enamel matrix, especially the peripheral region of the enamel rod. Immunostained protein bands were observed near 65 or 70 kDa and below 20 kDa. C-terminal-specific antibodies stained the secretory machinery of the ameloblast and the immature enamel adjacent to the secretion sites. Immunostained protein bands were found ranging from 25 to 70 kDa. Antibodies which recognize a region in the protein just prior to the C-terminal region stained the cis-side of the Golgi apparatus but not the enamel matrix. Immunostained protein bands were observed of about 55 kDa. These results suggest that post-translational and post-secretory modifications of ameloblastin and sheathlin are similar to each other, and further showed that their cleaved N-terminal polypeptides concentrate in the prism sheath. We propose that sheathlin and ameloblastin share the same role in amelogenesis and should be classified as sheath proteins.  相似文献   
102.
103.
Abstract: Flow visualization is widely applied to evaluate rotary blood pumps; however, it is very difficult to visualize flow near the vanes of centrifugal blood pumps because the rotational speed of the impeller is usually several thousand rpm. In this study, a tracer method with a high speed video camera that can take more than 2,000 frames/s was utilized for flow visualization together with computer-assisted image measurement. This method visualized the complex secondary flow pattern near the vanes of the impeller, such as the vortex and recircula-tion. It also visualized the enhanced washout effect by the secondary washout vanes on the backside of the impeller. The proposed method was effective to analyze the flow pattern in the centrifugal blood pump by providing useful information for better design of the pump hemolysis and thrombus formation.  相似文献   
104.
A review of ten surgical cases of medullary carcinoma of the thyroid (MCT) demonstrates the usefulness of establishing a preoperative cytological diagnosis through the immunochemical staining of calcitonin (CT) and CEA in fine-needle aspiration (FNA) biopsy smears. If MCT is suspected after routinely performing May-Grünwald-Giemsa stained cytology of an FNA biopsy in the outpatient clinic, then CT and CEA staining is recommended for confirmation of MCT. The advantages of this immunochemical staining include that it can be carried out in the outpatient clinic within one day and also that it is much less costly than measuring serum CT and CEA.  相似文献   
105.
Summary A new computerized apparatus was constructed to measure the resonant frequency of human ulnain vivo with high sensitivity and reproducibility. Experimental studies using aluminum bar and dried human bone revealed the importance of the ulna being positioned parallel to the radius, approximately 90 degree flexion of the elbow joint, and minimal muscle activity in order to demonstrate maximum resonant frequency of ulna. Measurement of bone resonance in monkeysin vivo and after removal of the bonein vitro showed good agreement. Product of F (maximum resonant frequency in Hz) and L (ulnar length in cm), FL, indicating the speed of propagation of sound wave through the ulna, showed a significant positive correlation with bone mineral content/bone width (BM/BW) measured by Norland-Cameron apparatus and age-bound decline in both sexes. Patients with osteomalacia and primary hyperparathyroid bone disease tended to have higher FL values than expected from BM/BW. Two-dimensional display of FL and BM/BW thus appears to be useful in distinguishing osteoporosis from osteomalacia better than the use of BM/BW alone.  相似文献   
106.
A patient evaluated for heart failure was found by routine radionuclide angiography to have a large internal iliac arteriovenous fistula of presumed postoperative origin. The value of radionuclide angiography is described with a review of the literature on such unusual cases.  相似文献   
107.
Xylooligosaccharides (XOS) are mainly composed of two or three xylose units with beta-1,4 linkages. They are obtained by hemicellulose hydrolysis, which is relatively abundant in the cell walls of grains. XOS increases the number of intestinal Bifidobacterium in humans, and maintains the fecal water content within the normal range. To examine the effect of XOS intake on severe constipation in pregnancy, which is predominant in the third trimester, thirty constipated pregnant women were treated with 4.2 g XOS daily for 4 wk. During the study, the clinical efficacy was assessed using a daily diary. The subjects indicated the number of stools and the clinical symptom scores. Twenty-nine subjects completed the study. The mean number of stools was 1.1 +/- 0.4 in the pre-treatment week, and increased in weeks 1-4 of XOS administration to 5.3 +/- 2.1, 5.9 +/- 2.5, 6.2 +/- 2.2 and 6.7 +/- 1.9, respectively. At the end of the study, 27 subjects could defecate spontaneously. The occurrence of very loose or very hard stools decreased and the stool consistency normalized. The stool color changed from dark to yellowish brown. No side effects were observed. XOS intake was highly effective for the reduction of severe constipation in pregnant women without adverse effects.  相似文献   
108.
BACKGROUND AND OBJECTIVES: To investigate whether endogenous opioids might be involved in the mechanisms that underlie hemorrhagic shock-induced analgesia, formalin tests were performed after hemorrhage and reinfusion in naloxone pretreated and untreated rats. METHODS: Twenty-four adult male Sprague-Dawley rats were divided into control (n = 6), saline (n = 6), naloxone 10 mg/kg (n = 6), and naloxone 100 mg/kg (n = 6) groups. The mean blood pressure (mBP) was kept at 50 to 60 mm Hg for 30 minutes by draining arterial blood in the saline group and the naloxone groups. After 15 minutes of returning mBP to normal levels by reinfusion of the drained shed blood, 10% formalin (3.7% formaldehyde solution, 0.1 mL) was injected into the left rear paw. Nociceptive behaviors were observed for 1 hour after the formalin injection. RESULTS: Nociceptive behaviors of the posthemorrhagic shock groups were significantly lower than those of the control group. No significant difference was seen in nociceptive behaviors among the saline and naloxone groups. CONCLUSION: Naloxone did not reverse the hemorrhagic shock-induced analgesia, which suggests that endogenous opioids might not be a major factor that governs stress-induced analgesia (SIA) after hemorrhagic shock.  相似文献   
109.
BACKGROUND/AIMS: The therapeutic effect of cyclosporine A (CsA) in combination with steroids varies greatly for frequent-relapse minimal change nephrotic syndrome (FRMCNS). The association between the sensitivity of peripheral blood lymphocytes (PBLs) to CsA in vitro and the therapeutic effect of CsA in FRMCNS were investigated. METHODS: The sensitivity of PBLs in vitro and the therapeutic effect of CsA in 23 FRMCNS patients were compared. The length of time to complete remission (CR) and the number of relapses were compared using the 50% inhibitory concentration (IC(50)) of CsA in the presence of a T-cell mitogen. RESULTS: FRMCNS patients were divided into 2 groups: a low sensitivity group with an IC(50) of >14.8 ng/ml (GII, n = 10), and a high sensitivity group with an IC(50) of <14.8 ng/ml (GI, n = 13). Comparison of the length of time to CR between the 2 groups showed that GI reached CR earlier than GII (p < 0.01). GI had significantly fewer relapses than GII when CsA was administered for 12 months or longer (p < 0.01). CONCLUSION: Lymphocyte sensitivity to CsA has the potential to be an important clinical indicator of the antiproteinuric effect and relapse rate in FRMCNS.  相似文献   
110.
This study was performed to retrospectively compare changes in the levels of total cholesterol, non-HDL cholesterol, triglycerides, and immunosuppressive drugs, cyclosporine A and steroids in patients with living-relation renal transplants with those from non-heart-beating donors. We experienced 11 cases of kidney transplants from non-heart-beating donors during the period from April 1995 to May 2003. We evaluated 13 cases of kidney transplants from living-relation donors during the same period. The immunosuppressants used included mainly cyclosporine A as well as mycophenolate mofetil or azathioprine, steroid and ALG, or basiliximab. Over-night fasting lipids (total cholesterol, triglycerides and HDL cholesterol) were studied before renal transplantation and repeated after renal transplantation at 1, 3, 6 and 12 months. The levels of total cholesterol and triglycerides remained in the normal range before transplantation. However, the levels of total cholesterol increased siginificantly 1 and 3 months after transplantation from non-heart-beating donors and remained at higher levels up to 12 months after transplantation. A similar pattern in the levels of triglycerides was observed. The levels of HDL cholesterol remained unchanged and stayed in the normal range before and 1, 3, 6, and 12 months after transplantation from non-heart-beating donors. On the other hand, significant increases in non-HDL cholesterol were observed 3 and 6 months after transplantation from non-heart-beating donors. After transplantation from living-relation donors, levels of total cholesterol, triglycerides, and non-HDL cholesterol remained unchanged and remained in the normal range up to 12 months after transplantation. Although there were no significant differences in the total dosage of cyclosporine A between the patients with living-relation donors and those with non-heart-beating donors, a significant increase in the total dosage of methylprednisolone was observed in patients with non-heart-beating donors compared with those in the patients with living-relation donors. Renal function recovery in patients with living-relation donors was better than in those with non-heart-beating donors. These results may suggest that significant increases in total cholesterol, especially non-HDL cholesterol and triglycerides, were probably partly due to an increased use of immunosuppressants, steroids. It is necessary to aggressively control post-transplant hyperlipidemia and important to reduce or withdraw steroids in the selected, low-risk recipients as early as possible from the viewpoint of preventing post-transplant hyperlipidemia.  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