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   11827篇
  免费   784篇
  国内免费   55篇
耳鼻咽喉   77篇
儿科学   365篇
妇产科学   347篇
基础医学   1658篇
口腔科学   184篇
临床医学   1359篇
内科学   2438篇
皮肤病学   270篇
神经病学   1349篇
特种医学   378篇
外科学   1016篇
综合类   95篇
一般理论   1篇
预防医学   1020篇
眼科学   362篇
药学   654篇
中国医学   26篇
肿瘤学   1067篇
  2024年   15篇
  2023年   134篇
  2022年   222篇
  2021年   454篇
  2020年   289篇
  2019年   416篇
  2018年   392篇
  2017年   314篇
  2016年   360篇
  2015年   369篇
  2014年   480篇
  2013年   689篇
  2012年   985篇
  2011年   997篇
  2010年   525篇
  2009年   426篇
  2008年   760篇
  2007年   789篇
  2006年   684篇
  2005年   589篇
  2004年   589篇
  2003年   528篇
  2002年   528篇
  2001年   60篇
  2000年   52篇
  1999年   80篇
  1998年   92篇
  1997年   66篇
  1996年   53篇
  1995年   45篇
  1994年   47篇
  1993年   43篇
  1992年   36篇
  1991年   44篇
  1990年   20篇
  1989年   26篇
  1988年   20篇
  1987年   27篇
  1985年   26篇
  1984年   28篇
  1983年   20篇
  1982年   31篇
  1981年   32篇
  1980年   32篇
  1979年   19篇
  1978年   23篇
  1977年   17篇
  1976年   16篇
  1975年   16篇
  1974年   17篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
The termwell-baby clinic (literally, a clinic that concerns itself with healthy infants) is probably better known in the United States, where such clinics exist, than in central Europe, where, on the whole, they do not. For the convenience of readers accustomed to it a formal definition is proffered: A well-baby clinic is a service center, with emphasis on physical and mental hygiene and prophylaxis, where mothers are seen with their young, healthy infants and helped to understand and manage the infant's unfolding maturation [1: p. 5] and development [1: p. 5]. This may serve to differentiate well-baby clinics, on the one hand, from clinics for sick children and child guidance clinics (usually resorted to after disturbances have emerged) and, on the other hand, from maternity and child welfare clinics, whose primary object is to safeguard physical health. (Maternity and child welfare clinics are also known as family health clinics, child health clinics, and infant welfare clinics. The extent to which they can cater to the psychological needs of mother and infant depends on their staff's training.)This paper forms part of a research project entitled Childhood Pathology: Impact on Later Mental Health, which is being conducted at the Hampstead Child-Therapy Course and Clinic, London. The project is financed by National Institute of Mental Health Grant MH-05683-11. Appreciation is expressed to Anna Freud, Elizabeth Model, Professor A. J. Solnit, and Dr. Josefine Stross for their valuable suggestions. The authors acknowledge with gratitude the freedom to quote from the Well-Baby Clinic's annual reports, compiled by the clinic's pediatrician, Dr. Josefine Stross, with the active help of her past assistants, Annemarie Curson, Manna Friedmann, and Joyce Robertson, and her present assistants, Irene Freud and E. Model.This paper was originally published in German, in volume 2 of theJahrbuch der Psychohygiene, Ed. Gerd Biermann, Ernst Reinhardt Verlag, München/Basel, 1974.  相似文献   
52.
53.
Isolated rat hepatocyte couplets were used to perform the comparative study of two widely used immunosuppressors, cyclosporin A (CsA) and tacrolimus (FK506) on hepatocanalicular function. We assessed canalicular function by counting the percentage of couplets that were able to accumulate the fluorescent cholephile, cholyl-lysyl-fluorescein (CLF), into the canalicular vacuole between the two cells, i.e., canalicular vacuole accumulation (CVA) of CLF. Compared to controls (DMSO-treated cells), CsA, in the approximate range of concentrations used therapeutically, caused inhibition of CVA of CLF, disorganization of the bile salt export pump (Bsep) localization at canalicular level resulting in its relocation into the cell, and disruption of the pericanalicular F-actin cytoskeleton. In contrast, FK506, at both approximately therapeutic and supratherapeutic concentrations, had no deleterious effect upon CVA of CLF, upon the localization of the bile salt transporter at the canalicular membrane, or on the organization of the pericanalicular F-actin cytoskeleton. These results point to transporter and cytoskeletal disorganization as contributors or determinants of CsA-induced cholestasis at canalicular level, whereas FK506 does not appear to produce these cholestasis-determining responses even at supratherapeutic concentrations.  相似文献   
54.
There are several genes that code for enzymes, including various forms of superoxide dismutase and glutathione peroxidase, that protect the cell against oxidative damage that, in turn, can lead to carcinogenesis. There are a few common genetic polymorphisms in these genes that lead to altered proteins. Three that have been identified are SOD2 Val-9Ala, GPX1 Pro198Leu, and the GPX1 GCG repeat (three alleles with four, five, or six repeats). The SOD2 variant has been associated with increased breast cancer risk in two studies. The GPX1 variants have not been studied with respect to breast cancer, but Pro198Leu has been associated with lung cancer. We conducted a case-control study of these three polymorphisms in incident, invasive breast cancer in Caucasian women under 55. There were 399 cases and 372 controls genotyped, of whom 488 were premenopausal, 208 postmenopausal, and 75 of unknown menopausal status. We were unable to replicate the previously observed association with SOD2 Val-9Ala and also found no association between breast cancer and GPX1 Pro198Leu. However, the allele of GPX1 containing four GCG repeats was significantly associated with breast cancer risk in premenopausal women (odds ratio, 1.55; 95% confidence interval, 1.04-2.30 for carriers versus noncarriers). There is a significant trend of increasing risk with increasing number of alleles with four GCG repeats (P = 0.03). This variant has not previously been reported to be associated with breast cancer.  相似文献   
55.
OBJECTIVES: Most research on hospital falls has focused on predictors of falling, whereas less is known about predictors of serious fall-related injury. Our objectives were to characterize inpatients who fall and to determine predictors of serious fall-related injury. METHODS: We performed a retrospective observational study of 1,082 patients who fell (1,235 falls) during January 2001 to June 2002 at an urban academic hospital. Multivariate analysis of potential risk factors for serious fall-related injury (vs no or minor injury) included in the hospital's adverse event reporting database was conducted with logistic regression to calculate adjusted odds ratios (aORs) with 95% confidence intervals (CI95) RESULTS: The median age of patients who fell was 62 years (interquartile range, 49-77 years), 50% were women, and 20% were confused. The hospital fall rate was 3.1 falls per 1,000 patient-days, which varied by service from 0.86 (women and infants) to 6.36 (oncology). Some (6.1%) of the falls resulted in serious injury, ranging by service from 3.1% (women and infants) to 10.9% (psychiatry). The most common serious fall-related injuries were bleeding or laceration (53.6%), fracture or dislocation (15.9%), and hematoma or contusion (13%). Patients 75 years or older (aOR, 3.2; CI95, 1.3-8.1) and those on the geriatric psychiatry floor (aOR, 2.8; CI95, 1.3-6.0) were more likely to sustain serious fall-related injuries. CONCLUSIONS: There is considerable variation in fall rates and fall-related injury percentages by service. More detailed studies should be conducted by floor or service to identify predictors of serious fall-related injury so that targeted interventions can be developed to reduce them.  相似文献   
56.
PURPOSE: To investigate the relationships between biomarker changes in breast cancer during neoadjuvant (preoperative) endocrine therapy. PATIENTS AND METHODS: The IMPACT trial compared the preoperative use of tamoxifen with anastrozole alone or in combination in postmenopausal women (n = 330) with primary breast cancer. Biomarkers were measured in tumor biopsy specimens taken at baseline, and after 2 and 12 weeks of treatment. RESULTS: 52 (93%) of 56, 46 (85%) of 54, and 37 (84%) of 44 patients in the anastrozole, tamoxifen, and combination groups, respectively. There was a significantly greater suppression of Ki67 in the anastrozole-treated group than in the tamoxifen- or combination-treated groups, which is parallel to the greater efficacy seen for anastrozole over these two treatments in the Arimidex, Tamoxifen, Alone or in Combination adjuvant trial. A positive relationship was noted between estrogen-receptor level and Ki67 suppression in all patients. Ki67 was reduced to a greater extent in progesterone receptor-positive tumors compared with progesterone receptor-negative tumors. HER-2-negative tumors tended to show a greater reduction in Ki67 compared with HER-2-positive tumors, but the difference was only significant in the tamoxifen group after 2 weeks, and in the anastrozole group after 12 weeks. CONCLUSION: These results confirm the value of Ki67 as a molecular marker, and provide information regarding the relationships between treatment-induced changes in Ki67 and other important biomarkers. Studies such as this should help integrate agents targeted at growth factor signaling with endocrine agents in breast cancer.  相似文献   
57.
PURPOSE: It has been hypothesized that tumors with high interstitial fluid pressure (IFP) and/or hypoxia respond poorly to chemotherapy (CT) because of poor drug delivery. Preclinical studies have shown that paclitaxel reduces the IFP and improves the oxygenation (pO(2)) of tumors. Our aim is to evaluate the IFP and pO(2) before and after neoadjuvant CT using sequential paclitaxel and doxorubicin in patients with breast cancer tumors of >/= 3 cm. PATIENTS AND METHODS: Patients were randomly assigned, according to an institutional review board-approved phase II protocol, to receive neoadjuvant sequential CT consisting of either four cycles of dose-dense doxorubicin at 60 mg/m(2) every 2 weeks followed by nine cycles of weekly paclitaxel at 80 mg/m(2) (group 1) or vice versa, with paclitaxel administered before doxorubicin (group 2). Patients were re-evaluated clinically and radiologically. The IFP (wick-in-needle technique) and pO(2) (Eppendorf) were measured in tumors at baseline and after completing the administration of the first and second drug. RESULTS: IFP and pO(2) were measured in 54 patients at baseline and after the first CT. Twenty-nine and 25 patients were randomly assigned to groups 1 and 2, respectively. Paclitaxel, when administered first, decreased the mean IFP by 36% (P = .02) and improved the tumor pO(2) by almost 100% (P = .003). In contrast, doxorubicin did not have a significant effect on either parameter. This difference was independent of the tumor size or response measured by ultrasound. CONCLUSION: Paclitaxel significantly decreased the IFP and increased the pO(2), whereas doxorubicin did not cause any significant changes. Tumor physiology could potentially be used to optimize the sequence of neoadjuvant CT in breast cancer.  相似文献   
58.
Ramucirumab plus paclitaxel is considered the standard of care in the second-line treatment of gastric carcinoma (GC). The aim of this study was to evaluate plasma vascular endothelial growth factor-A (VEGF-A), VEGF-D, and circulating soluble VEGF receptor-2 (sVEGFR-2) as possible markers of resistance or response to ramucirumab administered with paclitaxel in pretreated metastatic GC patients. Plasma samples were collected at different time points (on days 1 and 15 of the first 3 cycles, at best radiologic response and at disease progression). VEGF-A, VEGF-D and sVEGFR-2 were analysed by ELISA. Correlations of biomarker baseline levels or dynamic changes with outcome measures were assessed. Progression-free survival (PFS) was the primary endpoint of the study. Forty-one patients were enrolled. VEGF-A and VEGF-D, but not sVEGFR-2, values significantly increased during treatment compared to baseline (P < 0.001). A positive correlation between VEGF-A and sVEGFR-2 at cycle 2 was found (P=0.045). At univariate analysis, higher baseline levels of VEGF-A were associated with worse OS (P=0.015). Early increase of sVEGFR-2 levels after the first treatment cycle was the only factor associated with longer PFS (6.6 vs. 3.6 months, P=0.049) and OS (18.6 vs. 5.2 months, P=0.008). Significance of sVEGFR-2 early increase was retained at multivariate analysis for OS (HR 0.32; 95% CI 0.12-0.91; P=0.032). The reported results confirmed the prognostic role of baseline VEGF-A and, with the limitations of the limited sample size and the lack of a control arm, suggested that the early increase of sVEGFR-2 after 1 cycle of treatment could be a potential predictive biomarker of benefit from second-line ramucirumab plus paclitaxel in GC.  相似文献   
59.
SARS-CoV-2 is a global challenge due to its ability to mutate into variants that spread more rapidly than the wild-type virus. Because the molecular biology of this virus has been studied in such great detail, it represents an archetypal paradigm for research into new antiviral drug therapies. The rapid evolution of SARS-CoV-2 in the human population is driven, in part, by mutations in the receptor-binding domain (RBD) of the spike (S-) protein, some of which enable tighter binding to angiotensin-converting enzyme (ACE2). More stable RBD-ACE2 association is coupled with accelerated hydrolysis of furin and 3CLpro cleavage sites that augment infection. Non-RBD and non-interfacial mutations assist the S-protein in adopting thermodynamically favorable conformations for stronger binding. The driving forces of key mutations for Alpha, Beta, Gamma, Delta, Kappa, Lambda and Omicron variants, which stabilize the RBD-ACE2 complex, are investigated by free-energy computational approaches, as well as equilibrium and steered molecular dynamic simulations. Considered also are the structural hydropathy traits of the residues in the interface between SARS-CoV-2 RBD and ACE2 protein. Salt bridges and π-π interactions are critical forces that create stronger complexes between the RBD and ACE2. The trend of mutations is the replacement of non-polar hydrophobic interactions with polar hydrophilic interactions, which enhance binding of RBD with ACE2. However, this is not always the case, as conformational landscapes also contribute to a stronger binding. Arginine, the most polar and hydrophilic among the natural amino acids, is the most aggressive mutant amino acid for stronger binding. Arginine blockers, such as traditional sartans that bear anionic tetrazoles and carboxylates, may be ideal candidate drugs for retarding viral infection by weakening S-protein RBD binding to ACE2 and discouraging hydrolysis of cleavage sites. Based on our computational results it is suggested that a new generation of “supersartans”, called “bisartans”, bearing two anionic biphenyl-tetrazole pharmacophores, are superior to carboxylates in terms of their interactions with viral targets, suggesting their potential as drugs in the treatment of COVID-19. In Brief: This in silico study reviews our understanding of molecular driving forces that trigger mutations in the SARS-CoV-2 virus. It also reports further studies on a new class of “supersartans” referred to herein as “bisartans”, bearing two anionic biphenyltetrazole moieties that show potential in models for blocking critical amino acids of mutants, such as arginine, in the Delta variant. Bisartans may also act at other targets essential for viral infection and replication (i.e., ACE2, furin cleavage site and 3CLpro), rendering them potential new drugs for additional experimentation and translation to human clinical trials.  相似文献   
60.
BACKGROUND Patients with skull defects sometimes develop neurological deficits, which have been grouped under “the syndrome of the trephined”. The deficits are usually nonspecific or nonlocalizing, such as apathy or diffuse headaches. We report, to our knowledge, a first case of severe midbrain syndrome associated with a skull defect. Cranioplasty dramatically resolved the patient's symptoms. A midbrain syndrome represents the main manifestation of the syndrome of the trephined and can be corrected by cranioplasty. CLINICAL PRESENTATION A 38-year-old man with head trauma and epidural hematoma initially had normal eye motility. He developed a skull defect after infection following cranioplasty. He presented with onset of neurological symptoms one year after head trauma with a skull defect, a small divergent and vertical strabismus, elevation deficit of both eyes, headaches and fatigue. Over several months he developed severe bilateral deficit of adduction, elevation, depression and convergence. He had neuropsychological deficits, fatigue, headaches and impaired coordination. Neuroimaging and lumbar puncture did not show evidence of increased intracranial pressure or hydrocephalus. INTERVENTION Cranioplasty using Palacos was performed one-and-a-half years after trauma. Immediately after surgery, the patient noted remarkable improvement in his symptoms. Headaches and fatigue disappeared within two days. Two weeks after cranioplasty the patient had orthotropia and virtually normal ocular motility. Neurological symptoms completely disappeared. Recovery remained sustained for over 5 years after cranioplasty. CONCLUSION To our knowledge, this represents the first case of the syndrome of the trephined in which the neurological deficits map primarily to the brainstem and show rapid improvement following cranioplasty. We show that cranioplasty in patients with large skull defects is indicated for more then cosmetic reasons and should be considered even after longer periods following a trauma.  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