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   12594篇
  免费   508篇
  国内免费   115篇
耳鼻咽喉   94篇
儿科学   167篇
妇产科学   203篇
基础医学   1625篇
口腔科学   163篇
临床医学   607篇
内科学   3257篇
皮肤病学   197篇
神经病学   1123篇
特种医学   718篇
外科学   2208篇
综合类   33篇
预防医学   367篇
眼科学   80篇
药学   734篇
中国医学   43篇
肿瘤学   1598篇
  2023年   56篇
  2022年   101篇
  2021年   171篇
  2020年   99篇
  2019年   129篇
  2018年   163篇
  2017年   146篇
  2016年   192篇
  2015年   215篇
  2014年   257篇
  2013年   338篇
  2012年   497篇
  2011年   634篇
  2010年   374篇
  2009年   343篇
  2008年   597篇
  2007年   615篇
  2006年   631篇
  2005年   666篇
  2004年   715篇
  2003年   799篇
  2002年   799篇
  2001年   268篇
  2000年   314篇
  1999年   320篇
  1998年   226篇
  1997年   226篇
  1996年   185篇
  1995年   174篇
  1994年   185篇
  1993年   153篇
  1992年   249篇
  1991年   239篇
  1990年   250篇
  1989年   222篇
  1988年   235篇
  1987年   165篇
  1986年   145篇
  1985年   128篇
  1984年   120篇
  1983年   105篇
  1982年   90篇
  1981年   66篇
  1980年   64篇
  1979年   75篇
  1978年   69篇
  1977年   43篇
  1976年   37篇
  1975年   46篇
  1974年   34篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
An attempt was made to detect a pancreatic tumor antigen (PTA) in transplantable pancreatic adenocarcinomas induced by N-bis(2-hydroxypropyl)nitrosamine (DHPN) in hamsters. Antibody against antigenic protein was raised by immunizing rabbits with whole homogenate of the tumors transplanted into the back of hamsters. PTA was purified by affinity chromatography and shown to have the physicochemical properties of a glycoprotein with a molecular weight of 800,000, migrating in the beta regions upon agarose gel electrophoresis. Loss of immunological properties was observed after heating at 65 degrees C for 30 min. Enzyme immunoassay revealed that the levels of PTA in the serum and tissue showed a positive correlation with the induction of the presence of tumor, and size of the tumor. It is tentatively suggested that PTA values above 150 ng/ml serum are indicators of tumors, because in normal hamsters the PTA range is from 25 to 130 ng/ml serum. Immunohistochemically, PTA was demonstrated to be localized within the cytoplasm of epithelial tumor cells of well-differentiated tubular adenocarcinomas.  相似文献   
32.
The carcinogenic activity of endogenously synthesized N-nitrosobis(2-hydroxypropyl)amine(BHP) was investigated in male Wistar rats administered bis(2-hydroxypropyl)amine(BHPA) mixed in powder diet at a concentration of 1%, and sodiumnitrite (SN) dissolved in distilled water at concentrationsof 0.15 and 0.3%, for 94 weeks. Urinary excretion of BHP wasdetected in rats given 1% BHPA and 0.3% SN but not in the groupsreceiving either of these precursors alone. Nasal cavity, lung,esophagus, liver and urinary bladder tumors were found in animalstreated with combinations of 1% BHPA and 0.15 or 0.3% SN, suggestingthat the target organs of the endogenously synthesized BHP aresimilar to those affected when the carcinogen is administeredexogenously. The incidences of nasal cavity and lung tumorsreached 74 and 58% in rats given 1% BHPA and 0.3% SN, respectively.Tumors at sites other than target organs were only found atlevels similar to those previously reported for spontaneoustumors in male Wistars. The present results clearly indicatedthe tumor inducibility of a nhrosatable amine, BHA, throughan endogenous nitrosation by feeding to rats in conjunctionwith nitrite, and provide further suggestive evidence that endogenousnitrosations of environmental nitrosatable amines can be a potentialrisk factor in human cancer development.  相似文献   
33.
Editorial     
  相似文献   
34.
To improve the outcome of invasive Candida infections, earlier empirical therapy before the establishment of the definitive diagnosis is considered to be necessary. However, appropriate use of empirical therapy for suspected candidiasis in febrile non-neutropenic surgical patients has not been defined. According to the guidelines from the Infectious Diseases Society of America, empirical therapy of suspected candidiasis in this setting should be limited to patients with Candida colonization of multiple sites, multiple other risk factors, and absence of any other causes of fever. A corrected colonization index which takes into account both the density and the degree of colonization of Candida spp. was shown to be the independent factors that predict subsequent candidal infection. It may also be appropriate to commence empirical therapy on the basis of a positive serodiagnostic test. Beta-D glucan is a cell-wall constituent of fungi, which is assumed to be a marker of fungal sepsis. However, it has been shown that beta-D-glucan can also be detected in patients without fungal infections, such as those on haemodialysis, and its positive predictive value is relatively low. The mono-utilization of beta-D-glucan for the assessment of fungal infection should therefore be avoided. The combined assessment of beta-D-glucan and extent of colonization with Candida spp. is believed to have the advantage of lessening the likelihood of a false positive reaction of beta-D-glucan.  相似文献   
35.
Our previous study demonstrated that pro-gastrin-releasing peptide(31–98), or ProGRP, is a specific tumor marker in patients with small cell lung carcinoma (SCLC). Using a newly developed, highly sensitive enzyme-linked immunosorbent assay (ELISA) for ProGRP, we analyzed 1,446 samples including those obtained from 478 lung cancer patients to evaluate the clinical usefulness of this ELISA. Several properties indicated that ProGRP is a useful tumor marker for SCLC. First, ProGRP was specifically elevated in SCLC patients. In non-SCLC patients and patients with non-tumorous lung diseases, its serum level was very rarely elevated. Secondly, ProGRP was a reliable marker, in terms of the marked elevation of serum ProGRP levels in SCLC patients. Thirdly, serum ProGRP levels were elevated in SCLC patients even at a relatively early stage of this disease. Fourthly, changes in the serum ProGRP level showed an excellent correlation with the therapeutic responses in SCLC patients. Neuron-specific enolase (NSE) is accepted as a tumor marker of SCLC patients. With the aim of comparing ProGRP and NSE as tumor markers for SCLC patients, we measured serum NSE levels in all samples collected in the present study. We found that ProGRP was superior to NSE in terms of sensitivity, specificity and reliability. Therefore, we consider that ProGRP can play a major role as a clinical tumor marker for SCLC patients.  相似文献   
36.
37.
Epidural midazolam with saline--optimal dose for postoperative pain]   总被引:3,自引:0,他引:3  
Optimal dose of epidural midazolam with saline for postoperative pain relief was investigated. Forty three patients for upper abdominal surgery were divided into 5 groups. Each group had either 10 ml saline only (saline group), 10 ml saline + midazolam 0.025 mg.kg-1 (0.025 group), 10 ml saline + midazolam 0.05 mg.kg-1 (0.05 group), 10 ml saline + midazolam 0.075 mg.kg-1 (0.075 group), or 10 ml saline + midazolam 0.1 mg.kg-1 (0.1 group) administered epidurally for complaint of postoperative pain. Blood pressure (BP), heart rate (HR), respiratory rate (RR) and sedation score (SS) were monitored for 120 minutes, and the time interval for next analgesics (TNA) was checked. In each group, BP was unchanged compared with preinjection level. HR changes were less in 0.05 and 0.1 group than in others. RR changes were less in 0.025 and 0.05 group than in others. Optimal SSs were obtained in 0.025 and 0.05 groups. In 0.075 and 0.1 groups, many patients fell into complete sleep (not responded to verbal command). TNA was about 2 hours in 0.025 and 0.05 groups, over 6 hours in 0.075 and 0.1 groups. Complete sleep was the cause of long TNA in 0.075 and 0.1 groups. It was concluded that optimal dose of epidural midazolam with saline 10 ml was 0.05 mg.kg-1 for postoperative pain relief after upper abdominal surgery.  相似文献   
38.
The song nuclei of the male zebra finch (Poephila guttata) contain larger neurons than those of the female. This gender difference arises after hatching as a result of cell atrophy in the female and cell growth in the male. Implantation of estrogen in female chicks induces masculine differentiation of neurons in their song nuclei. The effects of estrogen on neuron size decline steeply after posthatching day 35 when neuronal atrophy begins. Estrogen loses its masculinizing effects completely after day 45 when the adult level of neuronal atrophy is reached. Thus, the end and the intensity of hormone action appear to be correlated with the timing of neuronal atrophy.  相似文献   
39.
40.
Transganglionic transport of horseradish peroxidase-wheat germ agglutinin conjugate was used to study the central projection of primary afferent neurons innervating facial and intraoral structures. The examined primary neurons innervating the facial structures were those comprising the frontal and zygomaticofacial nerves and those innervating the cornea, while the primary neurons innervating the intraoral structures included those innervating the mandibular incisor and molar tooth pulps and those comprising the palatine nerve. The primary afferents innervating the facial structures project to the lateral or ventral parts of the trigeminal principal, oral and interpolar subnuclei, and to the rostral cervical spinal dorsal horn across laminae I through V, with a greater proportion being directed to the spinal dorsal horn. The primary afferents innervating the intraoral structures terminate in the dorsomedial subdivisions of the trigeminal principal, oral and interpolar subnuclei, and in laminae I, II, and V of the medial medullary dorsal horn, with a much denser projection being distributed to the rostral subnuclei. In addition to the above brain stem trigeminal sensory nuclear complex, they project to the supratrigeminal nucleus, caudal solitary tract nucleus, and paratrigeminal nucleus. These observations agree with previously reported data that the central projection of trigeminal nerve is organized in different manners for the facial and intraoral structures. Furthermore, the present findings in conjunction with our previous studies clarify that the central projection of primary afferents from the facial skin is organized in a clear somatotopic fashion and that the terminal fields of primary afferents from the intraoral structures extensively overlap in the brain stem trigeminal nuclear complex particularly in its rostral subdivisions. The central mechanism of trigeminal nociception is discussed with particular respect to its difference between the facial and intraoral structures.  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