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   25769篇
  免费   2397篇
  国内免费   46篇
耳鼻咽喉   236篇
儿科学   732篇
妇产科学   703篇
基础医学   3538篇
口腔科学   802篇
临床医学   2710篇
内科学   5322篇
皮肤病学   325篇
神经病学   2697篇
特种医学   1115篇
外国民族医学   1篇
外科学   3253篇
综合类   669篇
一般理论   25篇
预防医学   2228篇
眼科学   679篇
药学   1760篇
  2篇
中国医学   38篇
肿瘤学   1377篇
  2021年   322篇
  2020年   217篇
  2019年   353篇
  2018年   445篇
  2017年   338篇
  2016年   346篇
  2015年   397篇
  2014年   557篇
  2013年   960篇
  2012年   1266篇
  2011年   1338篇
  2010年   695篇
  2009年   697篇
  2008年   1239篇
  2007年   1296篇
  2006年   1351篇
  2005年   1354篇
  2004年   1324篇
  2003年   1210篇
  2002年   1234篇
  2001年   543篇
  2000年   524篇
  1999年   494篇
  1998年   296篇
  1997年   248篇
  1996年   250篇
  1995年   267篇
  1994年   241篇
  1993年   222篇
  1992年   418篇
  1991年   480篇
  1990年   433篇
  1989年   360篇
  1988年   411篇
  1987年   360篇
  1986年   356篇
  1985年   370篇
  1984年   343篇
  1983年   257篇
  1982年   210篇
  1981年   231篇
  1980年   211篇
  1979年   280篇
  1978年   225篇
  1977年   219篇
  1976年   194篇
  1975年   197篇
  1974年   223篇
  1973年   172篇
  1972年   188篇
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
21.
22.
This study was designed to assess the effects of acute nickel chloride administration on behavioral and autonomic thermoregulation in the rat. In one experiment, male rats of the Fischer 344 strain were injected with nickel chloride (IP) at dosages of 0 to 24.0 mg/kg and placed in an environmental chamber maintained at an ambient temperature (Ta) of 10 or 20 degrees C. Colonic temperature was measured 60 min postinjection. Nickel chloride caused a dose-related decrease in colonic temperature, and the hypothermia was accentuated at the cooler Ta. In a second study, rats injected with 0, 6.0, 12.0, or 24.0 mg/kg nickel chloride were placed in a temperature gradient which allowed the rats to select their preferred thermal environment. Nickel chloride at dosages of 12.0 and 24.0 mg/kg caused a significant reduction in the selected Ta. At these dosages the rats were also significantly hypothermic at 60 min postinjection. In a third experiment, whole-body oxygen consumption (i.e., metabolic rate) was measured at Ta's of 10, 20, and 30 degrees C following a 12.0 mg/kg injection of nickel chloride. Nickel chloride caused an initial depression in metabolic rate and hypothermia at Ta's of 10 and 20 degrees C but not at 30 degrees C. In conclusion, (a) nickel chloride affects both behavioral and autonomic control of thermoregulation in the rat and appears to induce a regulated decrease in body temperature and (b) the behavioral thermoregulatory response of the rat is less sensitive to nickel chloride when compared to the mouse.  相似文献   
23.
The utility of the dexamethasone suppression test (DST) in the diagnosis of depression was examined in an outpatient sample of 29 stroke patients. Results indicated that the DST's sensitivity was 15%, its specificity was 67%, and its positive predictive value was 48%. These findings suggest that the DST yields no more information than would be gained from random assignment of the diagnosis of depression. Therefore, it is not a useful measure of mood in these patients.  相似文献   
24.
The role of timing of transplant nephrectomy after renal transplantation has not been well defined. This report compares the morbidity, mortality, and hospitalization costs of 37 patients undergoing transplant nephrectomy within 14 days after graft failure and return to dialysis, with 31 patients undergoing delayed transplant nephrectomy (less than 14 days after graft failure and return to dialysis). This analysis revealed that there were no significant (P greater than .05) differences in patient morbidity and mortality between these groups. There was, however, a substantial increase (P less than .05) in the cost of hospitalization in the delayed nephrectomy group. For this reason, we recommend early nephrectomy after renal transplant failure in order to minimize the cost of health care for these patients undergoing failed cadaver donor transplant nephrectomy.  相似文献   
25.
Molecular determinants of cetuximab efficacy.   总被引:17,自引:0,他引:17  
PURPOSE: To investigate whether mRNA expression levels of cyclin D1 (CCND1), cyclooxygenase 2 (Cox-2), epidermal growth factor receptor (EGFR), interleukin 8 (IL-8), and vascular endothelial growth factor (VEGF), all members of the EGFR signaling pathway, are associated with clinical outcome in patients with EGFR-expressing metastatic colorectal cancer (CRC) treated with cetuximab. PATIENTS AND METHODS: Thirty-nine patients with metastatic CRC, refractory to both irinotecan and oxaliplatin, were enrolled on IMCL-0144 and treated with single-agent cetuximab. The intratumoral mRNA levels of CCND1, Cox-2, EGFR, IL-8, and VEGF were assessed from paraffin-embedded tissue samples using laser-capture microdissection and quantitative real-time polymerase chain reaction. RESULTS: There were 21 women and 18 men with a median age of 64 years (range, 35 to 83 years). Higher gene expression levels of VEGF were associated with resistance to cetuximab (P = .038; Kruskal-Wallis test). The combination of low gene expression levels of Cox-2, EGFR, and IL-8 was significantly associated with overall survival (13.5 v 2.3 months; P = .028; log-rank test). Both findings were independent of skin toxicity that was itself significantly correlated to survival. Patients with a lower mRNA amount of EGFR had a longer overall survival compared with patients that had a higher mRNA amount (7.3 v 2.2 months; P = .09; log-rank test). Patients with lower expression of Cox-2 had a significantly higher rate of grade 2 to 3 skin reactions under cetuximab treatment. CONCLUSION: This pilot study suggests that gene expression levels of Cox-2, EGFR, IL-8, and VEGF in patients with metastatic CRC may be useful markers of clinical outcome in single-agent cetuximab treatment.  相似文献   
26.
27.
28.
V Dave  G W Gordon  K D McCarthy 《Glia》1991,4(5):440-447
Very little information is available concerning the pharmacology of type 2 astroglia. During the past decade it has become apparent that two distinct lineages of astroglial cells can be defined in vitro. These two lineages are commonly referred to as type 1 and type 2 and are distinguished from each other on the basis of their morphological features and antigenic phenotypes. In contrast to type 1 astroglia, very little is known about the pharmacology of type 2 astroglia. The lack of information concerning the responsiveness of these cells stems primarily from difficulties encountered in isolating large numbers of type 2 astroglia free of other cell types. In the present study video- and photometer-based imaging systems were used to monitor the influence of a series of neuroligands on the intracellular calcium levels of individual cerebral type 2 astroglia in order to assess their expression of calcium-mobilizing receptors. The responses of 85 immunocytochemically identified cerebral type 2 astroglia to bradykinin (BK), norepinephrine (NE), histamine (HIST), carbachol (CARB), 2-methyl-thio ATP (2MT-ATP), glutamate (GLUT), and serotonin (5-HT) were analyzed. Approximately 50% of cerebral type 2 astroglia responded to BK, NE, HIST, CARB, and 2MT-ATP whereas only 16% and 9% of the cells responded to GLUT and 5-HT, respectively. The number of neuroligands that increased calcium in individual cells ranged from 0 to 6. These responses are quite similar to those previously demonstrated in cultured cerebral type 1 astroglia. No pattern of receptor co-expression was observed for the different neuroligands tests.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
29.
Interaction with adenosine A1 receptors is a possible contributory mechanism to the anticonvulsant effects of carbamazepine (CBZ) and the dihydropyridine calcium antagonists. We measured the binding of [3H]cyclohexyladenosine to adenosine A1 receptors in mouse brain stem, cerebellum, and cortex after oral administration of nifedipine, nimodipine (NMD), and CBZ for 7 days and compared the results with binding in control mice. Equilibrium dissociation constant (Kd) and receptor numbers (Bmax) were calculated using Scatchard and saturation isotherm analyses. Mean Kds (SEM) in control brain stem, cerebellum, and cortex were 2.09 (0.31), 2.39 (0.2), and 3.12 (0.28) nM, respectively. Results of Bmax for the same areas were 188 (26), 280 (24), and 449 (54) fmol/mg protein. Nifedipine (p less than 0.005) and NMD (p less than 0.02) raised the Kd of A1 receptors only in the cerebellum, and CBZ increased cerebellar Bmax (p less than 0.05). These minor effects on A1 receptors in CF1 mice, when given in doses previously shown to have anticonvulsant properties in these animals, do not suggest that alteration in A1 receptor activity is an important mechanism for the anticonvulsant effects of these drugs.  相似文献   
30.
Extramarital involvement (EMI) occurs with high prevalence among couples in clinical and community settings, frequently resulting in considerable distress both to participants and their spouses. The field lacks a synthesized review of this literature. Without such a synthesis, it has been difficult for researchers and clinicians to have an understanding of what is and is not known about EMI. This article reviews the large and scattered EMI literature using a framework that encompasses multiple source domains across the temporal process of engaging in and responding to EMI. In addition, this review delineates conceptual and methodological limitations to previous work in this area and articulates directions for further research.  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