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   1004篇
  免费   68篇
  国内免费   46篇
耳鼻咽喉   10篇
儿科学   30篇
妇产科学   23篇
基础医学   121篇
口腔科学   31篇
临床医学   158篇
内科学   108篇
皮肤病学   7篇
神经病学   101篇
特种医学   92篇
外科学   169篇
综合类   38篇
一般理论   2篇
预防医学   104篇
眼科学   20篇
药学   52篇
中国医学   1篇
肿瘤学   51篇
  2021年   16篇
  2020年   7篇
  2018年   19篇
  2017年   9篇
  2016年   12篇
  2015年   7篇
  2014年   11篇
  2013年   49篇
  2012年   37篇
  2011年   36篇
  2010年   34篇
  2009年   27篇
  2008年   32篇
  2007年   66篇
  2006年   28篇
  2005年   51篇
  2004年   25篇
  2003年   27篇
  2002年   24篇
  2001年   26篇
  2000年   32篇
  1999年   41篇
  1998年   24篇
  1997年   27篇
  1996年   7篇
  1995年   16篇
  1994年   16篇
  1993年   13篇
  1992年   30篇
  1991年   21篇
  1990年   19篇
  1989年   25篇
  1988年   32篇
  1987年   15篇
  1986年   21篇
  1985年   25篇
  1984年   23篇
  1983年   25篇
  1982年   7篇
  1981年   13篇
  1980年   9篇
  1979年   13篇
  1978年   10篇
  1976年   9篇
  1975年   7篇
  1974年   7篇
  1973年   7篇
  1972年   8篇
  1971年   7篇
  1966年   7篇
排序方式: 共有1118条查询结果,搜索用时 31 毫秒
1.
双波长紫外分光光度法测定贝母中腺苷和胸苷的含量   总被引:4,自引:0,他引:4  
将4种贝母的甲醇提取物经薄层色谱法粗分离后,直接用双波长紫外分光光度法测定其含量。结果表明,该方法线性关系好,腺苷和胸苷标准曲线的相关系数均为0.9999,同时也发现平贝、炉贝和伊贝中腺苷都占核苷总量60%以上,而浙贝中仅占约40%,提示贝母生药的抗凝血活性可能与贝母中核苷类化合物的种类和含量的差别有关。  相似文献   
2.
A variety of nutritional factors influence the bioavailability of calcium and increase a woman's risk of osteoporosis. Eight healthy women completed an 8-week metabolic study designed to investigate the effect of nonalcoholic carbonated beverage consumption on calcium metabolism. Compared with women receiving a control diet, women consuming a diet high in nonalcoholic carbonated beverages demonstrated similar mean serum levels of calcium, ionized calcium, phosphorus, alkaline phosphatase, parathyroid hormone, 1,25-dihydroxyvitamin D3, and osteocalcin. Twenty-four-hour urine volume, creatinine clearance, calcium-creatinine ratio, and phosphorus-creatinine ratio were similar during consumption of the diet high in nonalcoholic carbonated beverages and the control diet. Twenty-four-hour cyclic adenosine monophosphate-creatinine ratio was significantly lower in women consuming the diet high in nonalcoholic carbonated beverage compared with women receiving the control diet (342 +/- 27.4 nmol/mmol vs 409 +/- 22.1 nmol/mmol). Consumption of a diet high in nonalcoholic carbonated beverages on a short-term basis does not appear to affect adversely the serum or urinary markers of calcium metabolism.  相似文献   
3.
Use of carbon fibers for repair of abdominal-wall defects in rats   总被引:3,自引:0,他引:3  
Carbon in the form of 8-micron fibers induces growth of connective tissue. The purpose of this study was to measure and histologically characterize tissue ingrowth occurring in carbon fibers implanted for up to 12 months in abdominal-wall defects in rats, compared with polypropylene mesh. Carbon fibers induced significantly more tissue ingrowth than polypropylene mesh at 6 to 12 months postoperatively. The predominant tissues associated with carbon fibers and polypropylene mesh were dense connective tissue and fat, respectively. Fragmentation of the implants did not occur, and implant debris was not found in the regional lymph nodes. Carbon fibers are potentially useful for reinforcing abdominal-wall defects.  相似文献   
4.
We used arthrotomography to study the glenoid labrum in 114 patients. Sixty-nine of the patients had anatomic instability of the shoulder (including recurrent dislocation and subluxation of the shoulder), and 45 patients had functional instability of the shoulder (denoted by chronic pain, clicking of the joint, and the sensation that an unstable condition exists without the objective signs of it). Labral tears were revealed arthrotomographically in 86% of the patients with anatomic instability, while only 40% of the patients with functional instability had labral abnormalities, and these were primarily of minor severity. Fifty-six patients (44 of whom had anatomic instability; 12, functional instability) required surgery. The surgical findings were correlated with the arthrotomographic findings, and no false-positive results were revealed. However, arthrotomography demonstrated only part of the pathologic condition of two patients. These results confirm that there is a strong correlation between labral pathologic conditions and anatomic instability of the shoulder. Arthrotomographic studies have a great impact on the selection of therapy in cases of both anatomic and functional instability of the shoulder.  相似文献   
5.
6.
BACKGROUND: Multicolored Asian lady beetles (Harmonia axyridis) have been used as a biological control agent against crop-destroying aphids in the United States. Outside their natural habitat, H. axyridis seeks refuge in homes during fall and winter, leading to patient complaints and symptoms of rhinitis, wheezing, and urticaria on exposure to the beetles. OBJECTIVE: To gain a better understanding of the character and spectrum of allergic disease provoked by exposure to home-infesting lady beetles. METHODS: Eight patients with allergic symptoms suspected of being caused by H. axyridis and consistent with an IgE-mediated process were identified and interviewed. A whole-body extract from H. axyridis was prepared. Western blots using the patients' serum identified specific IgE antibodies in the extract. Through a novel technique, immunohistochemical analysis using beetle sections overlayed with patient serum was performed. A random survey of allergists from across the United States was also performed to evaluate experience with cases of lady beetle allergy. RESULTS: Western blots revealed IgE binding to 5 proteins with molecular weights of approximately 8.6, 21, 28, 31, and 75 kDa. Specific IgE bound to proteins localized in the beetle's mouth and leg areas. The allergist survey revealed positive responses in North Central, Mid-Atlantic and New England states. CONCLUSION: In 8 patients with allergic symptoms on exposure to high levels of lady beetles, specific IgE bound to proteins from H. axyridis. There was also an increased frequency of suspected cases of lady beetle allergy in endemic areas.  相似文献   
7.
8.
The kindling technique has been reported to produce a long-lasting enhancement in both the early and late phases of evoked potentials triggered from the kindled focus. It also alters paired-pulse facilitation and depression in the pathways which support these phenomena. The present experiment was designed to determine whether the drugs which antagonize secondary generalization in the kindling model also antagonize kindling-enhanced excitation in the pathways leading out of the focus. Multiple doses of phenytoin, carbamazepine, and clonazepam were therefore tested against single- and double-pulse evoked potentials triggered from the focus in rats that had been subjected to parital kindling from either the amygdala or the cortex. Responses were recorded in monosynaptic sites and in the mesencephalic reticular formation--a polysynaptic site thought to play an important role in secondary generalization. No drug-related effects were found on early evoked potential components, either in the single-pulse or the double-pulse paradigm. Kindling-enhanced late components ("late waves"), however, were clearly and selectively antagonized by clonazepam.  相似文献   
9.
Growth of Trypanosoma musculi in vitro has been achieved. The number of parasites increased by more than 1,500-fold in less than 8 days under the most suitable conditions. The rate and magnitude of growth was comparable to that which occurs in inoculated murine hosts. Maximum growth was displayed in cultures composed of RPMI 1640 medium supplemented with fetal calf serum, murine spleen cells, and foreign erythrocytes (sheep). No growth occurred in the absence of spleen cells. The adherent, macrophage-rich population supported parasite growth much better than did the nonadherent population. Parasite growth was excellent in the presence of irradiated spleen cells or of cells from thymectomized, irradiated, bone marrow-reconstituted mice. The important cells appeared to be macrophages. The beneficial effect of sheep erythrocytes probably resulted from preoccupation or stimulation of phagocytes. Soluble substances released by spleen cell cultures promote parasite growth, as was shown by experiments with double-compartment culture vessels. The utility of this culture system for analysis of host immune responses against the trypanosome was demonstrated.  相似文献   
10.
The aim of this study was to determine the relationship between calcium ionophore A23187-induced acrosome reaction (AR) and sperm fertilizing ability. Semen samples remaining after preparation for standard IVF were studied in 109 patients who had sperm concentrations > or =20 x 10(6)/ml. Ionophore-induced AR was performed on motile spermatozoa selected by centrifugation on a Percoll gradient. Semen analysis was performed using standard methods. Patients with higher (>50%, n = 76) fertilization rates had significantly higher ionophore-induced AR than patients with lower (<50%, n = 33) fertilization rates (49 +/- 14 versus 38 +/- 21%, P < 0.05). When the data from all patients were analysed by logistic regression, only the percentage sperm motility in insemination medium and ionophore-induced AR were significantly related to fertilization rates. Similar results were also obtained when the data from a subgroup of patients with poor (<15% normal) sperm morphology were analysed. However, when patients with normal sperm morphology > or =15% were analysed separately, only sperm count and the percentage of spermatozoa with progressive motility in semen were significantly related to fertilization rates. In conclusion, ionophore- induced AR was significantly related to fertilization rates in vitro mainly in patients with teratozoospermic semen. Tests for ionophore- induced AR may provide additional information about sperm fertilizing ability but may not indicate specific defects of the physiological AR.   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