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   8430篇
  免费   424篇
  国内免费   39篇
耳鼻咽喉   238篇
儿科学   84篇
妇产科学   122篇
基础医学   942篇
口腔科学   156篇
临床医学   514篇
内科学   2065篇
皮肤病学   129篇
神经病学   952篇
特种医学   263篇
外科学   1567篇
综合类   17篇
预防医学   235篇
眼科学   120篇
药学   622篇
中国医学   14篇
肿瘤学   853篇
  2023年   56篇
  2022年   100篇
  2021年   164篇
  2020年   126篇
  2019年   147篇
  2018年   202篇
  2017年   149篇
  2016年   150篇
  2015年   199篇
  2014年   236篇
  2013年   293篇
  2012年   443篇
  2011年   459篇
  2010年   263篇
  2009年   246篇
  2008年   385篇
  2007年   436篇
  2006年   392篇
  2005年   414篇
  2004年   389篇
  2003年   376篇
  2002年   369篇
  2001年   273篇
  2000年   264篇
  1999年   224篇
  1998年   85篇
  1997年   68篇
  1996年   55篇
  1995年   49篇
  1994年   67篇
  1993年   51篇
  1992年   197篇
  1991年   173篇
  1990年   141篇
  1989年   179篇
  1988年   124篇
  1987年   132篇
  1986年   100篇
  1985年   95篇
  1984年   61篇
  1983年   57篇
  1979年   53篇
  1978年   30篇
  1977年   29篇
  1976年   29篇
  1975年   32篇
  1974年   37篇
  1973年   33篇
  1972年   32篇
  1968年   26篇
排序方式: 共有8893条查询结果,搜索用时 15 毫秒
81.
82.
The effect of renal dysfunction on clinical outcomes following fractional flow reserve (FFR)-guided deferral of revascularization remains unelucidated.We retrospectively analyzed 224 patients with atherosclerotic coronary lesions who underwent deferred revascularization based on an FFR of >0.80. The median follow-up interval was 28.1 months. Patients were divided into 2 groups: the hemodialysis (HD) and the non-HD group. The non-HD group was further classified into 2 subgroups according to their estimated glomerular filtration rate (eGFR) level: eGFR <45, equivalent to chronic kidney disease stage 3b-5 and eGFR ≥45. We evaluated major adverse cardiac events (MACE), defined as a composite of cardiac death, myocardial infarction, and any revascularization.MACE occurred in 36 patients (16.1%). The rate of HD was significantly higher in the MACE group (19% vs 6%, P < .01). In non-HD patients, the eGFR was significantly lower in the MACE group (51.2 vs 63.2 mL/min/1.73 m2, P < .01). Overall, univariate Cox regression analysis revealed a significant relationship between HD and MACE (HR 2.91, P = .01), as did the multivariate model (HR 2.90, P = .01). Of the MACE, more deaths occurred in HD patients (15.8% vs 2.9%, P = .03). Among non-HD patients, eGFR <45 (HR 2.70, P = .02), FFR (per 0.01, HR 0.87, P < .01), and low-density lipoprotein cholesterol (per 10 mg/dL, HR 1.17, P = .02) were independent predictors of MACE. Any revascularization was more common in patients with eGFR<45 than in those with eGFR ≥45 (21.4% vs 7.3%, P = .02). Kaplan–Meier estimates revealed that the HD group showed a significantly lower MACE-free survival rate than the nonHD group (log-rank P < .01). In non-HD patients, the eGFR<45 group showed a lower MACE-free survival rate than the eGFR ≥45 group (log-rank P = .01).HD and reduced eGFR in non-HD patients were associated with adverse cardiac events after FFR-guided deferral of revascularization.  相似文献   
83.
84.
85.
86.
87.
Human B-cell differentiation factor (BCDF) was purified to homogeneity by sequential filtration and chromatography of culture supernatants from TCL-Na1 cells on an AcA34 gel column and then on a Mono P column with fast protein liquid chromatography and reversed-phase HPLC. A 5300-fold enrichment in specific activity of BCDF with about 25% recovery was attained. The homogeneity of purified BCDF was evidenced by the following: (i) the specific activity was 1.7 X 10(7) units/mg of protein, (ii) only two bands, Mr 19,000 and 21,000, were identified by NaDodSO4/PAGE under reduced as well as nonreduced conditions, and (iii) BCDF activity was recovered from the gel after NaDodSO4/PAGE in the fractions corresponding to protein bands of Mr 19,000 or 21,000. Purified BCDF induced Ig secretion in Epstein-Barr virus-transformed cell lines; as little as 3 pM gave 50% of the maximum reaction achieved by 30-80 pM BCDF. Purified BCDF induced Ig production in activated B cells without any effect on cell growth. Purified BCDF did not show any activity of interleukin 1 or 2, B-cell stimulatory factor (BSF)p-1, B-cell growth factor II (BCGF-II), or interferon. Since BCDF was isolated and characterized as described, we propose that the BCDF that induces the final differentiation of B cells into high-rate Ig-secreting cells be designated BSFp-2.  相似文献   
88.
Development and validation of a salmon prolactin radioimmunoassay   总被引:1,自引:0,他引:1  
A highly specific radioimmunoassay (RIA) for the measurement of prolactin (PRL) in the plasma and pituitary of salmonid fishes was developed using a rabbit antiserum to chinook salmon (Oncorhynchus tschawytscha) PRL. The PRLs purified from chinook salmon and chum salmon (O. keta) pituitaries showed exactly the same competitive inhibition curves in the RIA, regardless of iodination of either hormone. The displacement curves for pituitary extracts and plasma from several salmonids, including chum, coho, and amago salmon, rainbow trout, and Japanese charr, were parallel to the salmon PRL standard, whereas those from the eel, goldfish, carp, and tilapia showed negligible cross-reactivity. Negligible cross-reactivity was also seen with plasma from hypophysectomized rainbow trout or coho salmon. None of the mammalian PRL or growth hormone (GH) preparations, bullfrog PRL, or presumptive chum salmon "gonadotropin" and eel "PRL" cross-reacted in the PRL RIA. Presumptive chum salmon GH showed less than 0.05% cross-reactivity. The RIA sensitivity was less than 0.1 ng of the salmon PRL standard per milliliter. The immunoreactive plasma PRL levels in mature chum salmon were below 1 ng/ml in seawater. The plasma PRL in females increased to about 8 ng/ml 1 day after transfer to fresh water, and high levels (2-4 ng/ml) were maintained during 3-7 days after the transfer. In contrast, when males were transferred to fresh water, an increase in plasma PRL was seen only 1 day after the transfer. A significant decrease in plasma osmolality was observed in both males and females after transfer to fresh water. No change was observed either in plasma PRL or osmolality, when fish were transferred from seawater to seawater.  相似文献   
89.
A rare case of glioblastoma fed by meningeal branches of the external carotid artery was reported. A 63-year-old female was transferred to our hospital suffering from gait disturbance and dysarthria. CT and MRI revealed brain tumor and paratumoral hemorrhage with a large cyst that was heterogeneously enhanced and existed in the right fronto-temporal region. Right external carotid arteriography demonstrated the tumor stain markedly fed by the right middle meningeal artery and the accessory meningeal artery. Subtotal removal operation was carried out uneventfully using the right fronto-temporal craniotomy. The histological diagnosis was glioblastoma. After the operation the patient was in good condition, and was transferred to another hospital for the purpose of the synchronized chemoradiotherapy. It is well known that any glioma invades the meninges. However, we rarely encountered an intra-axial glioma fed by a meningeal blood supply. A meningeal-invaded glioma may make difficult its differentiation from meningioma. We concluded that there is necessity for close examination of the intra-axial brain tumors invaded and fed by meningeal blood supply.  相似文献   
90.
We investigated the effects of dietary restriction (DR), an experimental intervention known to suppress several strain-specific diseases, on the prevalence of osteonecrosis of the caput femoris in spontaneously hypertensive rats (SHR). At 6 weeks of age, the food intake of DR rats was restricted to 65% of the mean intake of control rats fed ad libitum (AL). Acute osteonecrosis of the caput femoris without reparative tissue response (RTR) was observed at 10 and 15 weeks in both DR and AL groups; no such acute lesion was seen at 20 and 30 weeks. The prevalence of osteonecrosis, osteonecrosis with/without reparative tissue response was significantly reduced in DR rats at 15 and 20 weeks, but not at 10 weeks. DR reduced the body weight by 30% and the length of the femur by 10%. Ossification of the caput femoris, known to be delayed in AL rats compared with Wistar Kyoto rats, was also restored by DR. Our results showed that dietary restriction reduced the prevalence of osteonecrosis and modulated the mechanical factors involved in the lesion. They also indicate that utilization of dietary restriction is a useful research tool for investigating the underlying mechanisms of osteonecrosis of the caput femoris in SHR. Received: 4 March 1997 / Accepted: 9 July 1998  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