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   8310篇
  免费   471篇
  国内免费   16篇
耳鼻咽喉   52篇
儿科学   299篇
妇产科学   189篇
基础医学   1172篇
口腔科学   408篇
临床医学   918篇
内科学   1307篇
皮肤病学   85篇
神经病学   856篇
特种医学   211篇
外科学   1146篇
综合类   40篇
一般理论   7篇
预防医学   729篇
眼科学   37篇
药学   700篇
中国医学   4篇
肿瘤学   637篇
  2021年   62篇
  2020年   69篇
  2019年   82篇
  2018年   140篇
  2017年   112篇
  2016年   123篇
  2015年   126篇
  2014年   164篇
  2013年   316篇
  2012年   383篇
  2011年   325篇
  2010年   242篇
  2009年   210篇
  2008年   435篇
  2007年   425篇
  2006年   413篇
  2005年   464篇
  2004年   368篇
  2003年   420篇
  2002年   388篇
  2001年   165篇
  2000年   158篇
  1999年   164篇
  1998年   126篇
  1997年   137篇
  1996年   112篇
  1995年   90篇
  1994年   84篇
  1993年   90篇
  1992年   183篇
  1991年   170篇
  1990年   151篇
  1989年   143篇
  1988年   120篇
  1987年   122篇
  1986年   126篇
  1985年   111篇
  1984年   112篇
  1983年   101篇
  1982年   85篇
  1981年   66篇
  1980年   65篇
  1979年   79篇
  1978年   71篇
  1977年   70篇
  1976年   56篇
  1975年   59篇
  1974年   58篇
  1973年   60篇
  1970年   45篇
排序方式: 共有8797条查询结果,搜索用时 15 毫秒
991.
Rheumatoid arthritis (RA) is one of our most common disabling diseases today. Whether or not RA also existed in ancient times has been questioned and debated in recent years. Supporters of the view of recent onset claim that evidence of the existence of RA in antiquity can be found neither in old literature nor in paintings--and most important--convincing paleopathological finds are lacking. The following presentation reviews the results of an examination of skeletons found during an excavation of a neolithic burial place in the island of Gotland, Sweden. In two skeletons there were marked peripheral changes in both large and small joints. These changes are compatible with in vivo presence of a chronic aseptic polyarthritis. Different diagnostic possibilities for such polyarticular joint disease are discussed. It is suggested that RA might be the most probable alternative although other possibilities cannot be excluded.  相似文献   
992.
Neuropeptide Y (NPY), a regulatory peptide in both the central and peripheral nervous systems, has recently been found in neuroendocrine tumors as well as in the bone marrow of rat and certain autoimmune mice, but not in human bone marrow. To investigate a possible role for NPY in the human hematopoietic system, we have prospectively studied NPY-like immunoreactivity in plasma (P-NPY-LI) and NPY mRNA in bone marrow from children with acute leukemia. Northern blot showed high levels of NPY mRNA in bone marrow and peripheral lymphoblasts from children with B-cell precursor leukemia. In situ hybridization showed NPY mRNA in malignant B-cell precursor lymphoblasts. No NPY mRNA was detected in the bone marrow of children with T-cell leukemia. P-NPY-LI was higher (P less than .001) in 51 children with leukemia (200:50 to 385 pmol/L, median:interquartile range) compared to 51 age-matched healthy controls (37:20 to 52 pmol/L). P-NPY-LI was higher (P less than .001) in those with favorable clinical risk classification. Elevated P-NPY-LI, compared with the upper age-adjusted reference limit, was only found in children with B-cell precursor leukemia (31 of 40), whereas all children with B-cell, T-cell, or myeloid leukemia (n = 11) had normal P-NPY-LI (P less than .001). During the 2- to 46-month follow-up, children with elevated P-NPY-LI had better (P less than .001) outcome compared to those with normal P-NPY-LI (79.4% v 34.6% probability for event-free survival).  相似文献   
993.
994.
A retrospective serological study was performed on sera from 1982-83 and 1989 to investigate the incidence of Chlamydia pneumoniae infection in hospital treated patients with pneumonia in Orebro County. Paired sera from 231 patients were available and 3 cases (1.3%) of C. pneumoniae infection were documented by microimmunofluorescence. The results differ from those reported by others implying regional differences of C. pneumoniae as causative agent of pneumonia. The findings from Orebro County do not support any change in current antibiotic policy and we still regard penicillin as the first drug of choice in community-acquired pneumonia.  相似文献   
995.
Laminins are alphabetagamma heterotrimeric extracellular proteins that regulate cellular functions by adhesion to integrin and nonintegrin receptors. Laminins containing alpha4 and alpha5 chains are expressed in bone marrow, but their interactions with hematopoietic progenitors are unknown. We studied human bone marrow cell adhesion to laminin-10/11 (alpha5beta1gamma1/alpha5beta2gamma1), laminin-8 (alpha4beta1gamma1), laminin-1 (alpha1beta1gamma1), and fibronectin. About 35% to 40% of CD34(+) and CD34(+)CD38(-) stem and progenitor cells adhered to laminin-10/11, and 45% to 50% adhered to fibronectin, whereas they adhered less to laminin-8 and laminin-1. Adhesion of CD34(+)CD38(-) cells to laminin-10/11 was maximal without integrin activation, whereas adhesion to other proteins was dependent on protein kinase C activation by 12-tetradecanoyl phorbol-13-acetate (TPA). Fluorescence-activated cell-sorting (FACS) analysis showed expression of integrin alpha6 chain on most CD34(+) and CD34(+)CD38(-) cells. Integrin alpha6 and beta1 chains were involved in binding of both cell fractions to laminin-10/11 and laminin-8. Laminin-10/11 was highly adhesive to lineage-committed myelomonocytic and erythroid progenitor cells and most lymphoid and myeloid cell lines studied, whereas laminin-8 was less adhesive. In functional assays, both laminin-8 and laminin-10/11 facilitated stromal-derived factor-1alpha (SDF-1alpha)-stimulated transmigration of CD34(+) cells, by an integrin alpha6 receptor-mediated mechanism. In conclusion, we demonstrate laminin isoform-specific adhesive interactions with human bone marrow stem, progenitor, and more differentiated cells. The cell-adhesive laminins affected migration of hematopoietic progenitors, suggesting a physiologic role for laminins during hematopoiesis.  相似文献   
996.
Capsaicin-induced cough in humans.   总被引:14,自引:0,他引:14  
We have evaluated the properties of capsaicin as a selective cough-inducing agent in healthy human subjects. Despite frequent coughing, the subjects could inhale repeated breaths of capsaicin aerosol during 60 s without difficulty. Cough started immediately on inhalation and was most intense during the first 30 s. Cough always disappeared promptly when the capsaicin inhalation was terminated. The cough response was well reproducible and concentration-dependent up to 10 microM; at higher concentrations there was a distinct plateau of the cough response. Specific airway conductance was not changed 3 min after 50 microM capsaicin. Capsaicin (> or = 10 microM) had a burning taste, but there were no visual signs of pharyngitis or laryngitis. Citric acid (nebulized solutions 0.125 to 32%) had a choking effect and could be administered only as single breaths. There was no correlation between the cough response to citric acid and to capsaicin. Inhaled lidocaine (20 and 80 mg from nebulized solutions) caused a dose-dependent inhibition of capsaicin-induced cough. Lidocaine suppressed citric acid-induced cough as effectively as capsaicin-induced cough. In conclusion, we have characterized capsaicin-induced cough and demonstrated that it can be a useful tool in the study of cough reactivity and for evaluation of antitussive agents in humans. Capsaicin may be complementary to citric acid and may offer experimental advantages over this traditional tussive stimulus.  相似文献   
997.
Endoscopic sphincterotomy (ES) for common bile duct calculi (CBDC) was performed on 210 patients, and 190 of these were available for follow-up. One hundred seventy-three patients (91%) were successfully treated with ES alone, whereas 17 patients required operation. Stone size was of importance to attain complete clearance of CBDC as larger stones (greater than 1 cm) were significantly more difficult to extract endoscopically than smaller stones (p less than 0.01). A comparison between patients with one CBDC and those with two or more show a statistically significant difference in that the former group is easier to treat successfully (p less than 0.001).  相似文献   
998.

Background

Patients with synchronous colorectal liver metastases (sCRLM) are increasingly operated with liver resection before resection of the primary cancer. The aim of this study was to compare outcomes in patients following the liver-first strategy and the classical strategy (resection of the bowel first) using prospectively registered data from two nationwide registries.

Methods

Clinical, pathological and survival outcomes were compared between the liver-first strategy and the classical strategy (2008–2015). Overall survival was calculated.

Results

A total of 623 patients were identified, of which 246 were treated with the liver-first strategy and 377 with the classical strategy. The median follow-up was 40 months. Patients chosen for the classical strategy more often had T4 primary tumours (23% vs 14%, P = 0.012) and node-positive primaries (70 vs 61%, P = 0.015). The liver-first patients had a higher liver tumour burden score (4.1 (2.5–6.3) vs 3.6 (2.2–5.1), P = 0.003). No difference was seen in five-year overall survival between the groups (54% vs 49%, P = 0.344). A majority (59%) of patients with rectal cancer were treated with the liver-first strategy.

Conclusion

The liver-first strategy is currently the dominant strategy for sCRLM in patients with rectal cancer in Sweden. No difference in overall survival was noted between strategies.  相似文献   
999.
Objective: To perform a subgroup analysis on those patients in STOP-Hypertension-2 who had isolated systolic hypertension. Design and methods: The STOP-Hypertension-2 study evaluated cardiovascular mortality and morbidity in elderly hypertensives comparing treatment with conventional drugs (diuretics, beta-blockers) with that of newer ones [angiotensin-converting enzyme (ACE) inhibitors, calcium antagonists]. In all, 6614 elderly patients with hypertension (mean age 76.0 years, range 70-84 years at baseline) were included in STOP-Hypertension-2. In the present subgroup analysis of STOP-Hypertension-2, isolated systolic hypertension was defined as systolic blood pressure at least 160 mmHg and diastolic blood pressure below 95 mmHg, in accordance with the Syst-Eur and Syst-China study criteria. In total, 2280 patients in STOP-Hypertension-2 met these criteria. In the study, patients were randomized to one of three treatment groups: “conventional” antihypertensive therapy with beta-blockers or diuretics (atenolol 50 mg, metoprolol 100 mg, pindolol 5 mg, or fixed-ratio hydrochlorothiazide 25 mg plus amiloride 2.5 mg daily); ACE inhibitors (enalapril 10 mg or lisinopril 10 mg daily); or calcium antagonists (felodipine 2.5 mg or isradipine 2.5 mg daily). Analysis was by intention to treat. Results: The blood pressure lowering effect in patients with systolic hypertension was similar with all three therapeutic regimens: 35/13 mmHg in the conventional group (n = 717), 34/12 mmHg in the ACE inhibitor group (n = 724), and 35/13 mmHg in the calcium antagonist group (n = 708). Prevention of cardiovascular mortality, the primary endpoint of the study, did not differ between the three treatment groups. All stroke events, i.e. fatal and non-fatal stroke together, were significantly reduced by 25% in the newer-drugs group compared with the conventional group (95% CI 0.58-0.97; p = 0.027). This difference was attributable to reduction of non-fatal stroke while fatal stroke events did not differ between groups. New cases of atrial fibrillation were significantly increased by 43% (95% CI 1.02-1.99; p = 0.037) on “newer” drugs compared with “conventional” therapy, mainly attributable to the calcium antagonists. There were no significant differences between the three treatment groups with respect to the risks of myocardial infarction, sudden death or congestive heart failure. Conclusions: The analysis demonstrated that “newer” therapy (ACE inhibitors/calcium antagonists) was significantly better (25%) than “conventional” (diuretics/beta-blockers) in preventing all stroke in elderly patients with isolated systolic hypertension.  相似文献   
1000.
Inhibition of oxidative metabolism is often found to decrease contractility of systemic vascular smooth muscle, but not to reduce global [Ca(2+)](i). In the present study, we probe the hypothesis that it is associated with an altered pattern of intracellular Ca(2+) oscillations (waves) influencing force development. In the rat tail artery, mitochondrial inhibitors (rotenone, antimycin A, and cyanide) reduced alpha(1)-adrenoceptor-stimulated force by 50% to 80%, but did not reduce global [Ca(2+)](i). Less relaxation (about 30%) was observed after inhibition of myosin phosphatase activity with calyculin A, suggesting that part of the metabolic sensitivity involves the regulation of myosin 20-kDa light chain phosphorylation, although no decrease in phosphorylation was found in freeze-clamped tissue. Confocal imaging revealed that the mitochondrial inhibitors increased the frequency but reduced the amplitude of asynchronous cellular Ca(2+) waves elicited by alpha(1) stimulation. The altered wave pattern, in association with increased basal [Ca(2+)](i), accounted for the unchanged global [Ca(2+)](i). Inhibition of glycolytic ATP production by arsenate caused similar effects on Ca(2+) waves and global [Ca(2+)](i), developing gradually in parallel with decreased contractility. Inhibition of wave activity by the InsP(3) receptor antagonist 2-APB correlated closely with relaxation. Furthermore, abolition of waves with thapsigargin in the presence of verapamil reduced force by about 50%, despite unaltered global [Ca(2+)](i), suggesting that contraction may at least partly depend on Ca(2+) wave activity. This study therefore indicates that mitochondrial inhibition influences Ca(2+) wave activity, possibly due to a close spatial relationship of mitochondria and the sarcoplasmic reticulum and that this contributes to metabolic vascular relaxation.  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