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   15799篇
  免费   646篇
  国内免费   53篇
耳鼻咽喉   303篇
儿科学   1035篇
妇产科学   705篇
基础医学   1757篇
口腔科学   351篇
临床医学   1220篇
内科学   3462篇
皮肤病学   528篇
神经病学   970篇
特种医学   358篇
外科学   2408篇
综合类   329篇
一般理论   2篇
预防医学   1254篇
眼科学   324篇
药学   909篇
  1篇
中国医学   47篇
肿瘤学   535篇
  2021年   114篇
  2020年   77篇
  2019年   124篇
  2018年   140篇
  2017年   133篇
  2016年   122篇
  2015年   200篇
  2014年   250篇
  2013年   326篇
  2012年   444篇
  2011年   485篇
  2010年   306篇
  2009年   316篇
  2008年   487篇
  2007年   544篇
  2006年   566篇
  2005年   504篇
  2004年   444篇
  2003年   404篇
  2002年   439篇
  2001年   376篇
  2000年   388篇
  1999年   344篇
  1998年   236篇
  1997年   251篇
  1996年   276篇
  1995年   224篇
  1994年   214篇
  1993年   216篇
  1992年   259篇
  1991年   249篇
  1990年   218篇
  1989年   203篇
  1988年   189篇
  1987年   203篇
  1986年   149篇
  1985年   125篇
  1984年   108篇
  1983年   88篇
  1982年   75篇
  1981年   86篇
  1979年   61篇
  1959年   345篇
  1958年   759篇
  1957年   868篇
  1956年   771篇
  1955年   803篇
  1954年   780篇
  1949年   182篇
  1948年   125篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
A case of systemic lupus erythematosus (SLE) that developed 2 years after beginning hemodialysis is reported. The patient had not been given any drug implicated in the production of SLE. She had been treated with deferoxamine, an in vitro inhibitory of DNA synthesis. The difficulty of the diagnosis is emphasized. Clinical improvement after prednisone treatment was impressive. SLE may appear even in patients receiving hemodialysis, despite immunological depression derived from chronic uremia.  相似文献   
62.
Interleukin-1 (IL-1) is a cytokine produced by the macrophage-monocyte system that has important effects on immunological responses and inflammatory reactions. Several clinical studies have shown that severe protein energy malnutrition adversely effects cell-mediated immune responses and the functional state of macrophages. The objective of this study was to analyse IL-1 production by adherent cells stimulated in vitro with lipopolysaccharide B (LPS) from patients with alcoholic cirrhosis of the liver and its possible relationship with nutritional states. Forty-five patients with alcoholic cirrhosis and 28 healthy donors were investigated. A combined index of nine anthropometric and biochemical parameters was used to evaluate nutritional status of cirrhotic patients, allowing a distinction to be made between those patients with acceptable nutrition (group I: 40%), those with slight malnutrition (group II: 37.7%), and those with severe malnutrition (group III: 22.3%). IL-1 activity was significantly lower in the cirrhosis patients than in the controls (P less than 0.001). This activity also was significantly lower in samples obtained from cirrhotics with severe malnutrition than in those with acceptable nutrition (P less than 0.05); the combined index and the sole anthropometric index gave the same results, suggesting that malnutrition may play a role in the immunoregulatory disturbances in the pathogenesis of alcoholic liver disease.  相似文献   
63.
Background: Interleukin-6 is a pleiotropic cytokine with a wide range of physiological activities. It plays an important role in the immuno-neuro-humoral axis during stress and surgery.
Methods: Serum interleukin-6 in parturients was measured on hospital admission, immediately after birth and 12 and 24 hours later. All parturients had uncomplicated pregnancies, and delivered vaginally without (n=31) or with (n=20) epidural analgesia, or underwent Caesarean section under epidural (n=20) or general (n=10) anaesthesia.
Results: Serum interleukin-6 assayed immediately following Caesarean section was low, but peaked 12 hours later, irrespective of the anaesthetic technique or other foetomaternal characteristics. Patients who delivered vaginally showed the highest interleukin-6 levels immediately after delivery. These were positively correlated with serum interleukin-6 on admission and duration of labour. Serum interleukin-6 was significantly higher in parturients who had epidural analgesia, and was significantly lower in those receiving intravaginal prostaglandins compared to those without prostaglandins.
Conclusion: The interleukin-6 response after Caesarean section can be explained by a generalized acute phase response to surgery, with no anaesthetic, maternal or neonatal interference. The rapid increase in peripartum serum interleukin-6 levels after vaginal delivery reflects, in part, cervical ripening or labour, their physiological triggers and psychological or physical stress. Regional anaesthesia, duration of labour and exogenous prostaglandin administration can modulate the peripartum interleukin-6 response and subsequently the physiological effects of this cytokine.  相似文献   
64.
One of the major difficulties in left heart catheterization through the interatrial septum is to ensure that the Brockenbrough needle tip is correctly laid on the fossa ovalis floor (FOF), which is the only area where the puncture must be done. The difficulties may be enhanced in patients with atrial enlargement and subsequent distortion of the anatomical structures. In order to reduce the hazards of the septal puncture, an electrocardiographic mapping of the right atrial endocardium was performed using the Brockenbrough needle as an exploratory electrode in a group of 20 patients. When the tip of the needle was laid against the FOF, the endoatrial electrocardiogram (EAE) registered a slight or no injury curve, even when the pressure was tight enough to perforate the septum. On the contrary, the pressure on any other area of the muscular septum or atrial walls elicited a bizarre monophasic injury curve. The peculiar electrocardiographic response of the FOF to the pressure exerted by the Brockenbrough needle tip was a valuable aid to identify the area where the transseptal puncture must be done. In addition, the sudden changes in the P wave morphology immediately after the septal perforation, provided the first clue that the left atrium has been reached.  相似文献   
65.
The effects of N-n-propylajmaline (prajmalium) on the Na and Ca currents of single frog atrial and ventricular cells were studied by means of the whole-cell patch-clamp technique. Prajmalium (10(-9) to 10(-6) M) depressed the Na current (INa) in a dose- and use-dependent manner. In the same range of concentrations, prajmalium induced a dual effect on the high (ICaL) and low (ICaT) threshold Ca currents (the latter being only present in atrial cells). At a low concentration (10(-9) M), prajmalium increased both Ca currents while at high concentrations (10(-6) M) it depressed them. Prajmalium appeared very potent on ICaT although this current is generally reported to be barely sensitive to agonists and drugs. The action of the drug was also accompanied by a shortening in the half-time of inactivation of the Ca currents and a slight hyperpolarizing shift of their availability curves. The increase in ICaL by prajmalium was not prevented by prazosin (10(-7) M) nor by propranolol (10(-6) M), and it was also observed after ICaL had been fully stimulated by isoproterenol (10(-7)M). Nifedipine (10(-6) M), however, was able to prevent or block the prajmalium-induced increase in ICaL. Some similarities between the actions of prajmalium and dihydropyridine agonists on Ca currents are discussed.  相似文献   
66.
The synthesis and irreversible alpha-blocking activity in the rat vas deferens of a series of tetra- and diamine disulfides 2-38, structural analogues of benextramine (BHC), are described. All compounds containing a central cystamine moiety displayed an irreversible alpha-adrenergic blockade at concentrations ranging from 10(-4) to 6 X 10(-6)M. Potency was increased in cystamines N,N'-disubstituted with 6-aminohexyl groups, especially when the outer nitrogen atoms bear arylalkyl substituents or are enclosed in a ring. However, N,N,N',N'-tetrasubstituted cystamines were poor blockers. Structural specificity in the outer portion of the tetramine disulfide is low, since many types of substituents gave rise to potent alpha-blockers. Even replacement of the outer amines with nonbasic ethers or amides was observed to maintain irreversible alpha-blockade.  相似文献   
67.
68.
69.
70.
A retrospective follow-up study to ascertain the relationship between the level of serum zinc and its rate of change during gestation and birthweight was conducted in 476 women of lower socioeconomic status. Serum zinc concentrations measured at approximately 16 (early) and 32 weeks (later) in gestation were both found to be significant predictors of birthweight. Even after controlling for gestational age at birth and other determinants of birthweight, for each microgram/dl increase in serum zinc early and later in pregnancy, birthweight increased by 5.8 and 8.6 g, respectively. Furthermore, after adjustment for initial zinc levels both the total change (beta = -7.0, P = 0.0007) and the rate of change (beta = -60.8, P = 0.007) in serum zinc during pregnancy were inversely associated with birthweight, i.e., the larger the fall in serum zinc during pregnancy, the smaller the infant. Low serum zinc level (less than 60 micrograms/dl) late in pregnancy was associated with greater than a five-fold increase in the odds (OR = 5.8, 95% CI = 1.8, 16.4) of giving birth to a low birthweight infant. The results of this study suggest a threshold for maternal serum zinc below which the prevalence of low birthweight increases rapidly.  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