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   127551篇
  免费   7237篇
  国内免费   1097篇
耳鼻咽喉   1962篇
儿科学   1926篇
妇产科学   1890篇
基础医学   20351篇
口腔科学   3082篇
临床医学   11854篇
内科学   22802篇
皮肤病学   3978篇
神经病学   10357篇
特种医学   7299篇
外科学   16694篇
综合类   540篇
现状与发展   3篇
一般理论   27篇
预防医学   6703篇
眼科学   3223篇
药学   11457篇
中国医学   1457篇
肿瘤学   10280篇
  2023年   904篇
  2022年   2725篇
  2021年   4403篇
  2020年   2111篇
  2019年   2959篇
  2018年   3680篇
  2017年   3002篇
  2016年   3925篇
  2015年   5467篇
  2014年   6475篇
  2013年   7530篇
  2012年   11313篇
  2011年   10842篇
  2010年   6203篇
  2009年   5316篇
  2008年   7567篇
  2007年   7198篇
  2006年   6508篇
  2005年   6013篇
  2004年   5251篇
  2003年   4563篇
  2002年   3924篇
  2001年   3038篇
  2000年   2796篇
  1999年   2141篇
  1998年   907篇
  1997年   674篇
  1996年   513篇
  1995年   451篇
  1994年   391篇
  1993年   334篇
  1992年   756篇
  1991年   698篇
  1990年   639篇
  1989年   558篇
  1988年   466篇
  1987年   467篇
  1986年   334篇
  1985年   368篇
  1984年   261篇
  1983年   192篇
  1982年   134篇
  1981年   168篇
  1980年   128篇
  1979年   222篇
  1978年   162篇
  1976年   133篇
  1975年   120篇
  1974年   139篇
  1973年   119篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
A case of a paraffinoma in the urinary bladder is presented. Plain radiography and intravenous urography showed a low attenuation filling defect in the urinary bladder, and CT demonstrated a lobulated fat-attenuation mass floating in the urinary bladder.  相似文献   
132.
Perfusion is a crucial physiological parameter for tissue function. To obtain perfusion-weighted images and consequently to measure cerebral blood flow (CBF), a newly developed flow-sensitive alternating inversion recovery (FAIR) technique was used. Dependency of FAIR signal on inversion times (TI) was examined; signal is predominantly located in large vessels at short TI, whereas it is diffused into gray matter areas at longer TI. CBF of gray matter areas in the human brain is 71 ± 15 SD ml/100 g/min (n = 6). In fMRI studies, micro- and macrovessel inflow contributions can be obtained by adjusting TIs. Signal changes in large vessel areas including the scalp were seen during finger opposition at a TI of 0.4 s; however, these were not observed at a longer TI of 1.4 s. To compare with commonly used BOLD and slice selective inversion recovery techniques, FAIR and BOLD images were acquired at the same time during unilateral finger opposition. Generally, activation sites determined by three techniques are consistent. However, activation of some areas can be detected only by FAIR, not by BOLD, suggesting that the oxygen consumption increase couples with the CBF change completely. Relative and absolute CBF changes in the contralateral motor cortex are 53 ± 17% SD (n = 9) and 27 ± 11 SD ml/100 g/min (n = 9), respectively.  相似文献   
133.
134.
Nephrectomy during operative management of retroperitoneal sarcoma   总被引:4,自引:0,他引:4  
Background: Complete resection of a retroperitoneal sarcoma often requires removal of adjacent organs. In this study we evaluated the role of nephrectomy during operation for retroperitoneal sarcoma. Methods: Between July 1982 and July 1995, 75 of the 371 (20%) patients who underwent resection of retroperitoneal sarcoma at MSKCC underwent concommitant nephrectomy. Data concerning the reasons for nephrectomy, degree of sarcomatous renal involvement, and survival were retrospectively analyzed. Results: Fifty-four patients (72%) underwent nephrectomy during the initial resection, and 21 (28%) during a resection of a recurrent or persistent tumor. The most common reason for nephrectomy was total encasement by sarcoma (n=40; 53%), followed by dense adherence of the tumor to the kidney (n=21; 28%), and the direct invasion of the kidney by tumor (n=2; 3%). Pathology demonstrated an absence of kidney invasion in the majority of cases (55 of 75; 73%). Renal capsular invasion was present in 11 of 75 (15%), renal parenchymal invasion in 7 of 75 (9%), and renal vein invasion in 2 of 75 (3%) of cases. There were no significant differences in survival based on degree of sarcoma involvement of the kidney, tumor grade, or whether the resection was for primary or recurrent disease. The 53 patients who underwent a complete gross resection of all tumor had a significantly improved long-term survival compared to the 20 patients who did not (50% versus 20% DFS at 5 years, respectively; p<0.001). Conclusions: Decisions for concomitant nephrectomy during resection of retroperitoneal sarcoma should be based on whether this maneuver will provide a complete resection of all gross tumor, in which case the long-term disease-free survival of 50% is comparable to the reported 5-year survival of all patients with retroperitoneal sarcoma who are completely resected. Presented at the 49th Annual Cancer Symposium of the Society of Surgical Oncology, Atlanta, Georgia, March 21–24, 1996.  相似文献   
135.
This is the first preliminary report among two consecutive papers. Partial mastectomy(PM), axillary lymph node dissection(AD) and radiotherapy (RT) were performed on seventeen operable breast cancer patients who had been admitted from April 1991 to March 1992 to the department of surgery, Yongdong Severance Hospital for improved cosmetic appearance and better survival rate. Of seventeen patients, 47% were T1 lesion and 76% were stage I and II. Extensive intraductal component(EIC) within or around the tumor was also analyzed. Twenty nine per cent of the patients were EIC positive. The mean number of axillary lymph nodes was 21.5 after PM with AD and 20.5 after mastectomy. For radiotherapy, 4,500 rad was delivered to the breast parenchyma and 1,600 rad of boost to the primary tumor site using the electron beam method after surgery. All patients have since been living well without any local recurrence and were satisfied with breast preservation for the one-year follow-up period. We concluded that the PM, AD and RT can be another surgical treatment modality of breast cancer. A longer follow-up data will be followed on the second paper.  相似文献   
136.
In Alzheimer's disease (AD), pathological changes are found in the basal forebrain cholinergic system (BFCS), serotonergic raphe (RA), and noradrenergic locus coeruleus (LC) systems. The present study was designed to determine the extent to which selective damage in each of these systems individually could produce an impairment of memory, one of the clinical symptoms of AD. Rats were given selective lesions by injecting ibotenic acid into the nucleus basalis magnocellularis and medial septal area (i.e., BFCS); 5,7-dihydroxytryptamine into the medial and dorsal RA; and 6-hydroxydopamine (6-OHDA) into the LC or by ip injections of (2-chloroethyl)N-ethyl-2-bromobenzylamine HCl (DSP4). Levels of choline acetyltransferase (ChAT), norepinephrine, and serotonin verified lesion effectiveness and selectivity. Chronic changes in serotonergic-2 and beta-adrenergic receptors were also determined. Rats were tested in a delayed spatial alternation in a T-maze. BFCS lesions impaired choice accuracy with intertrial delays of 5, 30, and 60 s. RA lesions or DSP4 injections impaired choice accuracy only when the intertrial delay was 60 s. LC lesions (by 6-OHDA) did not impair choice accuracy at any delay. The results suggest that the pathological changes in the BFCS and RA are sufficient to produce the types of memory impairments associated with dementia, but the quantitative effects of pathology in these two systems are different.  相似文献   
137.
138.
The motor impairing effects and plasma concentrations of barbital and lorazepam were studied in the alcohol tolerant (AT) and alcohol non-tolerant (ANT) rat lines developed for low and high sensitivity to motor impairment from ethanol. The mixed (M) line, from which the AT and ANT rats were derived, was also included in the study. Like ethanol, barbital and lorazepam impaired the performance of the ANT rats more than that of the AT rats. The motor performance of the M rats was relatively more impaired after barbital than after lorazepam administration at the same dose used in the AT and ANT rats. At the two latter time points (2.5 and 3.5 h) the sensitive ANT rats had significantly higher serum barbital concentrations than the AT rats. The serum barbital concentrations of the AT and ANT rats did not differ, however, at the two first time points (0.5 and 1.5 h) of the tilting plane tests, although the ANT rats were significantly more intoxicated. The concentrations of lorazepam in plasma do not explain the differential motor impairment either, since the sensitive ANT rats had lower plasma concentrations than the insensitive AT rats. The results, thus, suggest that the selection involved in the development of the AT and ANT lines has not been specific for ethanol. The results also support the idea that ethanol, barbiturates and benzodiazepines have some modes of action in common.  相似文献   
139.
Temperature sensitive liposomes (TSL) containing adriamycin (ADM) and cytarabine (Ara-C) were prepared. ADM and Ara-C were selected as model compounds of amphiphilic and hydrophilic drug, respectively. Encapsulation efficiency of ADM entrapped into TSL was about twice greater than that of Ara-C. It might be due to different polarity of the drugs. Lipid compositions of TSL had no effect on the encapsulation efficiency of drugs. Thermal behavior of TSL using a differential scanning calorimetry (DSC) was also investigated. Phase transition temperature (Tc) of TSL was dependent on the lipid compositions of TSL.ADM broadened thermogram of TSL but Ara-C did not. However, Tc of TSL was not changed by any drug. Release rate of drugs was highly dependent on temperature. The release profile of ADM was similar to that of Ara-C. The maximum release rate of drugs from TSL was occurred at the near Tc and observed at 39–41°C for DPPC (Dipalmitoylphosphatidylcholine) only, 52–54°C for DSPC (Distearoylphosphatidylcholine) only, 41–43°C for DPPC and DSPC (3∶1), and 43–45°C for DPPC and DSPC (1∶1), respectively. Effect of human serum albumin (HSA) on the release rate of ADM was investigated. HSA had no significant effect on the release of ADM below Tc. However, ADM release from TSL was increased at the near and above Tc. The HSA-induced leakage of drug may result from the interaction of liposomal constituents with HSA structure at the near Tc. From the fact that the release profiles of ADM from freshly prepared TSL and stored TSL for 1 week at 4°C was not changed, the TSL was considered to be stable for at least 1 week at 4°C. Based on these findings, TSL may be useful to deliver drugs to preheated target sites due to its thermal behaviors.  相似文献   
140.
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