全文获取类型
收费全文 | 11883篇 |
免费 | 1120篇 |
国内免费 | 15篇 |
专业分类
耳鼻咽喉 | 129篇 |
儿科学 | 298篇 |
妇产科学 | 188篇 |
基础医学 | 1665篇 |
口腔科学 | 317篇 |
临床医学 | 1472篇 |
内科学 | 2228篇 |
皮肤病学 | 160篇 |
神经病学 | 905篇 |
特种医学 | 353篇 |
外科学 | 2003篇 |
综合类 | 261篇 |
一般理论 | 7篇 |
预防医学 | 1199篇 |
眼科学 | 251篇 |
药学 | 886篇 |
中国医学 | 5篇 |
肿瘤学 | 691篇 |
出版年
2022年 | 102篇 |
2021年 | 218篇 |
2020年 | 122篇 |
2019年 | 202篇 |
2018年 | 270篇 |
2017年 | 208篇 |
2016年 | 209篇 |
2015年 | 252篇 |
2014年 | 286篇 |
2013年 | 457篇 |
2012年 | 709篇 |
2011年 | 754篇 |
2010年 | 434篇 |
2009年 | 358篇 |
2008年 | 643篇 |
2007年 | 634篇 |
2006年 | 593篇 |
2005年 | 616篇 |
2004年 | 561篇 |
2003年 | 568篇 |
2002年 | 483篇 |
2001年 | 272篇 |
2000年 | 298篇 |
1999年 | 254篇 |
1998年 | 118篇 |
1997年 | 124篇 |
1996年 | 102篇 |
1995年 | 97篇 |
1994年 | 105篇 |
1993年 | 88篇 |
1992年 | 199篇 |
1991年 | 179篇 |
1990年 | 165篇 |
1989年 | 163篇 |
1988年 | 156篇 |
1987年 | 157篇 |
1986年 | 138篇 |
1985年 | 159篇 |
1984年 | 116篇 |
1983年 | 105篇 |
1982年 | 74篇 |
1981年 | 71篇 |
1979年 | 110篇 |
1978年 | 69篇 |
1977年 | 75篇 |
1973年 | 87篇 |
1972年 | 74篇 |
1971年 | 73篇 |
1970年 | 61篇 |
1968年 | 59篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
171.
Vedhara K Nott KH Richards SM Bradbeer C Davidson EA Ong EL Snow MH 《AIDS patient care》1995,9(6):276-280
Despite uncertainty over their reliability, CD4+ cell counts are used extensively in both clinical and research settings to document progression in HIV infection. We examined, therefore, whether the performance of a simple statistical test would facilitate greater accuracy in the use of this marker. CD4+ cell count data were collected from a cohort of deceased (N = 60) and living HIV-positive gay men (N = 100). Pearson's product moment correlation coefficients were calculated for each individual in order to examine the association between CD4+ counts and time since diagnosis. Correlations of 0.7 or greater were obtained in approximately 50 percent of cases in each cohort. For these individuals, CD4+ cell counts were deemed to be a reliable indicator of rate of progression. The results suggest that the proposed technique ensures greater precision in the use of CD4+ cell counts and that the technique cna be used in individuals with either complete (deceased patients) or partial (living patients) CD4+ data. 相似文献
172.
The biomedical model that has long been central to medical practice is gradually being expanded to a broader biopsychosocial model. Relationship-building skills commensurate with the new paradigm need to be understood by educators and taught to medical practitioners. The person-centered, or humanistic, model of psychologist Carl Rogers provides a theoretical approach for the development of effective biopsychosocial relationships. The Barrett-Lennard Relationship Inventory (BLRI) was developed in 1962 as an assessment instrument for the person-centered model. In this article, the person-centered model and the use of the BLRI as an assessment instrument of this model are discussed. Current and potential uses of the BLRI are explored. 相似文献
173.
Psychological and behavioral factors associated with colorectal cancer screening among Ashkenazim. 总被引:5,自引:0,他引:5
BACKGROUND: Psychological and behavioral factors related to annual colorectal cancer (CRC) screening were examined in a sample of Ashkenazi Jewish individuals. Identification of factors related to regular CRC screening in this population is important because of the possibility of a heightened incidence of CRC. METHODS: Eligible participants were 171 Ashkenazi Jewish adults 40 years or older attending an educational program about breast cancer genetics. Compliance with recommended guidelines for digital rectal examination and fecal occult blood test in the past year were dependent measures. Demographic variables, family history of CRC, perceived risk, physician recommendation, and worry about cancer were independent measures. RESULTS: Digital rectal examinations and fecal occult blood tests had been obtained in the past year by 46 and 31% of the participants, respectively. A logistic regression showed that physician recommendation was related significantly to obtaining digital rectal examinations. Physician recommendation and education were related significantly to obtaining fecal occult blood tests. Although participants with family histories of CRC perceived themselves as being at increased risk of developing CRC, and were more worried about developing colon cancer, they were no more likely to adhere to CRC screening guidelines than those without such histories. CONCLUSIONS: Overall, compliance with recommended CRC screening was low even among high-risk individuals. Physicians play a key role in motivating people to comply with CRC screening. Physicians need to en courage all asymptomatic patients 50 years and older to be screened for CRC. 相似文献
174.
175.
Clinically, the most apparent difference between the primary and permanent dentitions is the physiologic loss of the primary tooth by root resorption. Root resorption is associated with loss of integrity of the periodontal ligament (PDL), followed by recruitment of resorptive cells that remove root structure. We therefore cultured primary dentition PDL fibroblasts (PPDL cells) to investigate in vitro their production of matrix metalloproteinases (MMPs) and tissue inhibitors of MMP (TIMPs), and the effects of soluble factors produced by these cells on osteoclast-like cell differentiation. These studies demonstrate that PPDL cells in vitro have a heterogeneous morphology, and they constitutively synthesize 92-kDa gelatinase, 72-kDa gelatinase, and 53/57-kDa procollagenase as well as TIMP-1, -2, and a third inhibitor of matrix metalloproteinase, as determined by substrate gel zymography and immunoblot analysis. Compared with PDL cells from the permanent dentition, PPDL cells generally produced a greater amount of collagenase but similar amounts of the gelatinases and inhibitors. PPDL cells were treated with pro-inflammatory cytokines to determine their effect on the expression of matrix-degrading enzymes and inhibitors. Interleukin-1alpha and tumor necrosis factor-alpha enhanced the constitutive expression of proteinases but not that of inhibitors in PPDL cells. Conditioned media from PPDL cell lines inhibited the differentiation of osteoclast-like cells in mouse bone marrow cultures. These findings indicate that PPDL cells may modulate the cascade of root resorption both by their regulated production of proteinases and inhibitors and by synthesis of unknown soluble factor(s) that may regulate osteoclast development. 相似文献
176.
Cloning and functional expression of alternative spliced variants of the human metabotropic glutamate receptor 8 总被引:2,自引:0,他引:2
Malherbe P Kratzeisen C Lundstrom K Richards JG Faull RL Mutel V 《Brain research. Molecular brain research》1999,67(2):201-210
Two new spliced variants of the human metabotropic glutamate receptor 8 (HmGluR8), designated HmGluR8b and HmGluR8c, were identified in a human fetal brain cDNA library. The HmGluR8b and c differ from previously reported HmGluR8a by the out-of-frame insertions of 55-bp and 74-bp, respectively. The 55-bp insertion which contains a stop codon resulted in substitution of the last 16 amino acids in the C-terminus of HmGluR8a with 16 different amino acids in HmGluR8b. The 74-bp insertion introduces a frame shift in the predicted translation resulting in termination of the polypeptide before the putative seven transmembrane domains. Thus, the predicted HmGluR8c protein is 501 amino acids long and could represent a secreted isoform of the receptor. The pattern of mRNA expression of mGluR8 variants in human brain were analyzed by RT-PCR, Northern blot and in situ hybridization. Both HmGluR8a and b are expressed with similar abundance in fetal and adult brains. The in situ hybridization results indicate a predominantly glial cell expression of HmGluR8c in human brain. The three isoforms were transiently expressed in CHO cells from Semliki Forest Virus vectors. [3H]l-AP4 binding was performed on the cell membranes and the saturation curves showed the presence of a binding site with KD values of 249 and 182 nM and Bmax values of 13.6 and 10.5 pmoles/mg protein for HmGluR8a and b, respectively. For the six mGluR ligands studied, a similar rank order of potency was observed on both HmGluRa and b: l-AP4>l-SOP=l-CCG I>l-glutamate>DCG IV>LY 354740. 相似文献
177.
Long-term potentiation at excitatory amino acid synapses on midbrain dopamine neurons 总被引:4,自引:0,他引:4
Evidence suggests that a process analogous to long-term potentiation (LTP) may underlie the enhanced behavioural responses attending chronic administration of amphetamine and cocaine in animals (behavioural sensitization). Augmented excitatory amino acid (EAA)-mediated transmission at the level of midbrain dopamine neurons has been implicated as a change critical to the development of sensitization. Here we provide an initial demonstration that EAA synapses on dopamine neurons can undergo plasticity. Tetanic stimulation of the subthalamic nucleus induced a long-lasting increase (39.2 +/- 10.4%) in the amplitude of excitatory postsynaptic potentials recorded in dopamine neurons of the substantia nigra. This LTP, which did not occur in the presence of NMDA antagonists, may constitute the mechanism that lies at the heart of sensitization. 相似文献
178.
Revision total knee arthroplasty (TKA) consumes more time, more work, and more supplies than primary TKA. This study compared the hospital cost of primary and revision TKA after the introduction of cost-containment programs (implant standardization, clinical pathway, and competitive bid implant purchasing) at our hospital. Hospital financial records of 207 primary unilateral TKA operations and 32 revision TKA operations performed from October 1993 through September 1995 were analyzed. A cost-accounting system provided actual hospital cost data for each procedure. Accurate calculation of hospital income or loss was determined for all 239 procedures. The average hospital length of stay was 4.7 days for primary unilateral TKA and 5.1 days for revision TKA. There were 26 three-component revision operations and 6 one- or two-component revision operations. The average hospital cost was $10,421 for primary TKA and $11,906 for revision TKA. The average net hospital income (hospital revenue - hospital expense) was $3211 for primary TKA and $1853 for revision TKA. The payer mix included indemnity insurance, Medicare, Medicaid, managed care, and workmen's compensation. All payers were profitable except for Medicaid and selected managed care contracts for both primary and revision TKA. As a result of cost-containment programs, revision TKA can be profitable at our institution. 相似文献
179.
Laparoscopic prosthetic reinforcement of hiatal herniorrhaphy 总被引:3,自引:0,他引:3
BACKGROUND/AIMS: Primary repair of a large hiatal hernia is associated with a published recurrence rate of up to 10%; anecdotal rates even higher than this have been reported to the authors. The use of prosthetic material in the repair of other abdominal wall defects has often produced better results than primary repair. We wanted to compare laparoscopic primary repair of large hiatus hernias with laparoscopic primary repair reinforced with prosthetic. METHODS: Thirty-one patients with symptomatic gastroesophageal reflux and a hiatal defect 8 cm or greater were randomized to Nissen fundoplication with posterior cruroplasty (n = 16) or Nissen cruroplasty, and onlay of polytetrafluoroethylene (PTFE) mesh (n = 15). All patients underwent preoperative esophagogastroduodenoscopy (EGD) and barium esophagography. After posterior cruroplasty with interrupted nonabsorbable suture, the mesh reinforcement group had an onlay of PTFE placed around the hiatus. A radial slit with 3 cm 'keyhole' (to accommodate the esophagus) was cut into the PTFE. The prosthetic was stapled to the diaphragm, and the two leaves of the slit were stapled to each other. All patients underwent EGD at 3 months and all had esophagrams every 6 months postoperatively. Follow-up ranged from 12 to 36 months. RESULTS: Length of hospital stay was equal in both groups (2 days). The average cost to the patient with PTFE was USD 1,050 higher than to the patient with primary repair. There were 2 complications (1 pneumonia, 1 urinary retention) in the PTFE group, and 1 complication (pneumothorax) in the primary repair group. There were 3 recurrences (18.8%) in the primary group (p = 0.08, chi(2) test). CONCLUSION: The use of PFTE reinforcement for primary repair of large hiatal hernias may result in a lower rate of recurrent herniation compared to primary repair alone. Copyright Copyright 1999 S.Karger AG, Basel 相似文献
180.