全文获取类型
收费全文 | 6832篇 |
免费 | 720篇 |
国内免费 | 30篇 |
专业分类
耳鼻咽喉 | 65篇 |
儿科学 | 332篇 |
妇产科学 | 83篇 |
基础医学 | 806篇 |
口腔科学 | 164篇 |
临床医学 | 681篇 |
内科学 | 1307篇 |
皮肤病学 | 368篇 |
神经病学 | 457篇 |
特种医学 | 470篇 |
外科学 | 991篇 |
综合类 | 178篇 |
一般理论 | 8篇 |
预防医学 | 517篇 |
眼科学 | 44篇 |
药学 | 451篇 |
中国医学 | 3篇 |
肿瘤学 | 657篇 |
出版年
2021年 | 72篇 |
2019年 | 78篇 |
2018年 | 94篇 |
2017年 | 62篇 |
2016年 | 78篇 |
2015年 | 84篇 |
2014年 | 106篇 |
2013年 | 144篇 |
2012年 | 197篇 |
2011年 | 201篇 |
2010年 | 163篇 |
2009年 | 142篇 |
2008年 | 228篇 |
2007年 | 253篇 |
2006年 | 262篇 |
2005年 | 245篇 |
2004年 | 227篇 |
2003年 | 243篇 |
2002年 | 192篇 |
2001年 | 207篇 |
2000年 | 226篇 |
1999年 | 213篇 |
1998年 | 128篇 |
1997年 | 141篇 |
1996年 | 155篇 |
1995年 | 123篇 |
1994年 | 93篇 |
1993年 | 92篇 |
1992年 | 161篇 |
1991年 | 192篇 |
1990年 | 181篇 |
1989年 | 174篇 |
1988年 | 212篇 |
1987年 | 186篇 |
1986年 | 159篇 |
1985年 | 199篇 |
1984年 | 114篇 |
1983年 | 123篇 |
1982年 | 74篇 |
1981年 | 71篇 |
1980年 | 62篇 |
1979年 | 109篇 |
1978年 | 101篇 |
1977年 | 82篇 |
1976年 | 79篇 |
1975年 | 72篇 |
1974年 | 93篇 |
1973年 | 100篇 |
1972年 | 72篇 |
1971年 | 72篇 |
排序方式: 共有7582条查询结果,搜索用时 15 毫秒
101.
R.J.Mc Ivor R.A. Davies A. Wieck M.N. Marks N. Brown I.C. Campbell S.A. Checkley R. Kumar 《Journal of affective disorders》1996,40(3):131-136
We have examined the responsiveness of dopamine sensitive neurones in the postpartum period in woman with a history of major depression who are at high risk of experiencing a recurrence of illness in the postpartum period. Fourteen women were assessed at 36 weeks of pregnancy and during the 3 months following delivery, using the Schedule for Affective Disorders and Schizophrenia, including its change version. They were not depressed at initial assessment. Five of the 14 women went on to experience a postpartum relapse (2 major depressive disorder, 2 generalised anxiety disorder, 1 panic disorder). On the fourth day postpartum, ie before relapse, the growth hormone response to the dopamine agonist apomorphine was measured as an index of the functional state of hypothalamic dopamine D2 receptors. Women who subsequently relapsed had a significantly greater growth hormone response to apomorphine than those who remained well. This was particularly marked in women with anxiety/panic. The development of increased sensitivity of hypothalamic dopamine D2 receptors in the postpartum period appears to predict the onset of depressive and anxiety disorders. 相似文献
102.
Andrew D Chantry John A Snowden Charles Craddock Karl Peggs Claire Roddie Jenny I O Craig Kim Orchard Keiren E Towlson Rachel M Pearce David I Marks 《Biology of blood and marrow transplantation》2006,12(12):1310-1317
Relapsed acute myeloid leukemia (AML) in adults has a poor prognosis if treated with chemotherapy alone. Case series have previously supported the role of myeloablation and autologous transplantation as a potentially curative treatment. This study aimed to use the large numbers and extended follow-up data in the British Society of Blood and Marrow Transplantation (BSBMT) registry database to establish long-term outcomes and relate these to biological and procedural factors. The BSBMT registry database was used to retrospectively identify 152 adult patients (age, 16-69 years) with AML in second remission treated with autologous transplantation in 1982-2003. Cytogenetic data were available for 68% of the patients; of these, at diagnosis, 42% had good risk features, 57% had standard risk features, and 1% had poor risk features. Conditioning regimens varied; autologous rescue was provided with bone marrow (BM) (71%), peripheral blood stem cells (PBSCs) (18%), or both (11%), which were harvested during first complete remission (CR1) and/or second CR (CR2). Median follow-up was 84 months (range, 2-200 months). At 10 years, actuarial overall survival (OS) was 32%, progression-free survival (PFS) was 28%, and relapse rate (RR) was 57%. The 100-day nonrelapse mortality (NRM) was 7%, rising to 11% at 1 year and to 14% at 10 years. OS was significantly related to M3 subtype (5-year OS, 66%; P = .005), patient age at diagnosis (P = .005) and transplantation (P = .026), and length of CR1, with greatest significance if the patient was dichotomized at CR1 duration of < 8 months or > or = 8 months (P = .0001). There was no difference in OS between regimens containing total body irradiation (TBI) and chemotherapy alone (P = .7). In relation to the nature of autologous graft material, there was improved OS (P = .025) and PFS (P = .009) with the use of cells harvested entirely in CR1 compared with cells harvested in CR2 or in both CR1 and CR2. Engraftment times were significantly shortened with the use of PBSCs alone or in combination with BM compared with BM alone (P = .0001), but there was no significant long-term impact on OS, PFS, RR, or NRM. This study provides long-term follow-up data in one of the largest series of patients with standard-risk and good-risk AML in CR2 treated with autologous transplantation and supports earlier observations that long-term survival is achievable in about 1/3 of patients overall and in about 2/3 of patients with M3 with a relatively low NRM. Outcomes are better in patients with CR1 > or = 8 months by use of grafts obtained entirely in CR1 and use of PBSCs. TBI conditioning did not confer an advantage. Randomized studies against unrelated donor transplantation are warranted. 相似文献
103.
J. Toth C. Schultze-Werninghaus B. Marks A. F. P. Temmel P. Stübner S. Jäger F. Horak 《Allergy》1998,53(12):1172-1177
Background Preceding mucosal response to one allergen leads to the priming of the nasal mucosal response to another allergen. This study aimed t o determine whether environmental allergens, especially ubiquitous animal dander, can induce nasal priming.
Methods We investigated 26 grass-pollen-allergic subjects with additional sensitization to other aeroallergens. We performed continuous allergen challenge for 2 h with 1500 Dactylis glomerata pollen/m3 in the Vienna challenge chamber. The nasal flow at 150 Pa was examined, and subjective scores were obtained every 15 min. Statistical analysis was calculated from the area under curve of nasal flow reduction by Student's f-test and the Mann-Whitney U-test. Alpha was 0.05.
Results In subjects with positive cat-dander RAST (class of ≥ 3), besides grass-pollen allergy, the specific nasal allergic reaction to Dactylis challenge was significantly pronounced (P <0.01). and an earlier onset of reaction was evident. TTie same results were obtained with additional sensitization to dog dander (P<0.05). Concomitant sensitization to mugwort also led to escalating symptoms (P<0.05).
Conclusions These results indicate that a specific nasal allergic reaction is augmented by environmental priming caused by ubiquitous animal dander and possibly is influenced by the daily use of spices. 相似文献
Methods We investigated 26 grass-pollen-allergic subjects with additional sensitization to other aeroallergens. We performed continuous allergen challenge for 2 h with 1500 Dactylis glomerata pollen/m
Results In subjects with positive cat-dander RAST (class of ≥ 3), besides grass-pollen allergy, the specific nasal allergic reaction to Dactylis challenge was significantly pronounced (P <0.01). and an earlier onset of reaction was evident. TTie same results were obtained with additional sensitization to dog dander (P<0.05). Concomitant sensitization to mugwort also led to escalating symptoms (P<0.05).
Conclusions These results indicate that a specific nasal allergic reaction is augmented by environmental priming caused by ubiquitous animal dander and possibly is influenced by the daily use of spices. 相似文献
104.
Osteopetrosis, a metabolic bone disease characterized by a generalized sclerosis of the skeleton, is inherited as an autosomal recessive in a number of mammalian species. The pathogenesis of congenital osteopetrosis is mediated by a reduction in bone resorption as a result of decreased osteoclast function. This hypothesis is based on both functional and structural evidence of reduced bone resorption in all mutations examined to date. The present study examined the histology of cartilage and bone, the ultrastructure of osteoclasts, and the morphology of mineralized bone surfaces in a lethal osteopetrotic mutation, the osteosclerotic (oc) mouse. Histologically, epiphyseal cartilage growth plates, especially the hypertrophic zone, are markedly thickened in oc mice and metaphyses contain excessive osteoid, features characteristic of rickets. Transmission electron microscopy revealed that less than one-quarter of osteoclasts in oc mice demonstrated evidence of ruffled border formation compared with three-quarters of the osteoclasts in normal littermates. In mutants, ruffled borders were less elaborate and cytoplasmic processes penetrated into bone surfaces, suggesting that bone may be removed by mechanical rather than by enzymatic means. There was little morphological evidence of cartilage degradation and broad laminae limitantes persisted in mutants. Mineralized surfaces that undergo resorption in normal mice showed no evidence of bone resorption by scanning EM in mutants. The presence of a rachitic condition, the observations of reduced bone resorption, and the possible contribution of undermineralized matrices to decreased bone resorption are charcteristics of the osteosclerotic mutation which suggest that it is a unqiue csteopetrotic mutant in which to study both the development and regulation of skeletal metabolism. 相似文献
105.
Sandy C. Marks 《Developmental dynamics》1977,149(2):289-297
Osteoclasts have been observed for the first time in toothless (tl ) rats, a mutation which inherits osteopetrosis as an autosomal recessive. The ability of tl rats to raise the serum calcium concentration after injection of parathyroid extract was severely limited when compared with normal littermates. In addition, osteopetrosis in tl rats is not cured by radiation and infusion of normal spleen or bone marrow cells from normal littermates, a method known to cure osteopetrosis in mutants of this and other species. This indirect evidence for a reduction in bone resorption as a cause of osteopetrosis in this mutation and the failure of transplanted cells to cure the disease are discussed in relation to the development and function of osteoclasts. 相似文献
106.
The osteopetrotic (os) rabbit is a lethal mutation of autosomal recessive inheritance characterized by hypocalcemia, hypophosphatemia, fibrosis of marrow spaces, and ultrastructural abnormalities in both osteoclasts and osteoblasts. Procedures involving the transplantation of cells from normal hemopoietic tissues, which are sources of osteoclast precursors, are known to cure osteopetrosis in several mutations including some children. We tested the ability of transplanted bone marrow and/or spleen from normal littermates to reverse the skeletal sclerosis in os rabbits. Treatment of 15 neonatal mutants consisted of immunosuppression by whole-body irradiation followed by transplantation of normal bone marrow and/or spleen cell suspensions. This treatment failed to prolong life span or to cure osteopetrosis judged radiographically and histologically for up to 3 weeks posttreatment, the longest time of survival. These data indicate that transplantation of stem cells from multiple hemopoietic tissues, procedures known to cure osteopetrosis in other mutations, is not effective in the os rabbit. These results support the hypothesis that the skeletal microenvironment is not capable of supporting the development and function of normal osteoclasts in this mutation. 相似文献
107.
The United States has the highest incidence of firearm-related deaths among the Western industrialized nations. Firearms are the second leading cause of injury death. In 1982, the National Center for Health Statistics showed that firearms killed more than 33,000 individuals: 1,756 unintentionally, 16,573 by suicide, 13,841 by homicide, 376 by legal action, and 540 of undetermined intent. In terms of the total number of years of life lost, trauma in general contributed more years than heart disease and cancer combined for the year 1975. The southern regions of the United States tend to have higher firearm-related death rates than other regions of the country. Data collected within Arkansas are consistent with this trend. Handguns are the most frequently used firearms in fatal injuries. Unfortunately, data on nonfatal injuries are lacking. The emotional and economic costs of firearm-related death and injury are staggering. The estimated daily cost of hospitalization is $2100, and the average length of hospitalization is 10 days. The emotional impact of a gun-related injury or death will be felt immediately by 950,000 people per year. The economic loss resulting from "premature" deaths due to firearms is estimated to be nearly $4 billion annually. Unfortunately, the firearm is so ingrained in the American experience that one must conclude gunshot injuries and fatalities are simply part of the cost of living in America today. 相似文献
108.
Patterns of contrast enhancement of benign and malignant hepatic neoplasms during bolus dynamic and delayed CT 总被引:7,自引:0,他引:7
Bolus dynamic and delayed computed tomographic (CT) scans of the liver were evaluated in 43 patients with 54 hepatic hemangiomas and 111 patients with primary or secondary malignant hepatic neoplasms. Twelve patterns of contrast enhancement were recognized during the bolus dynamic phase and delayed scanning. A "typical" CT pattern for hemangiomas (present in 29 of 54 hemangiomas [53.7%]) was established: (a) diminished attenuation prior to intravenous contrast medium administration (excluding lesions arising in a liver with diffuse fatty infiltration), (b) peripheral contrast enhancement during the bolus dynamic phase, and (c) complete isodense fill-in on delayed scan images. Using these criteria, we distinguished hemangiomas from malignant neoplasms in most patients. Only one of 63 (1.6%) malignant neoplasms manifested these typical CT criteria of hemangioma. There is an 86% chance that a lesion with the typical CT appearance of hemangioma is actually a hemangioma, even when found in a patient with a known nonhepatic primary neoplasm. 相似文献
109.
Induction of plasma membrane alterations in AKR-2B mouse embryo fibroblasts by endogenous growth factors from malignant human cells 总被引:1,自引:0,他引:1
M E Marks M G Brattain 《International journal of cancer. Journal international du cancer》1984,33(1):139-146
AKR-2B mouse fibroblasts were treated with 50 micrograms/ml of crude transforming growth factor (TGF) of human origin. Cell surface proteins of treated cells were radioiodinated and compared to untreated cells at various times after the addition of TGF. Treated cells showed a severalfold increase (approximately 6-fold) in cell surface 125I incorporation relative to normal cells at 24 h. Electrophoretic comparison of treated and untreated cells showed large increases in the labelling of cell surface proteins of mol. wt. 50,000-90,000 from TGF-exposed cells between 10 and 24 h post treatment. By 48 h post treatment, the electrophoretic profiles of TGF-exposed cells had returned to a pattern similar to that of untreated cells. However, even after a 48 h exposure to TGF, the cells retained a transformed morphology indicating that the electrophoretic alterations were not simply due to the morphological transformation induced by TGF. The electrophoretic pattern of TGF-treated cells at 24 h post treatment was similar to that of AKR-2B cells permanently transformed by treatment with methylcholanthrene, but was clearly distinct from that induced by treatment of normal AKR-2B cells with epidermal growth factor (EGF). EGF induced an increase in a protein of mol. wt. 60,000 in the electrophoretic profiles taken 24 h post treatment. As with TGF, the appearance of electrophoretic profiles of EGF-treated cells returned to "normal" by 48 h. Again, these alterations did not appear to be dependent upon morphological changes since EGF-treated cells showed a morphological transformation similar to that of cells treated with TGF, and this was maintained throughout the 48 h experimental period. 相似文献
110.
N. M. Wilson G. B. Marks A. Eckhardt A. M. Clarke F. P. Young F. L. Garden W. Stewart T. M. Cook E. R. Tovey 《Anaesthesia》2021,76(11):1465-1474
Respirable aerosols (< 5 µm in diameter) present a high risk of SARS-CoV-2 transmission. Guidelines recommend using aerosol precautions during aerosol-generating procedures, and droplet (> 5 µm) precautions at other times. However, emerging evidence indicates respiratory activities may be a more important source of aerosols than clinical procedures such as tracheal intubation. We aimed to measure the size, total number and volume of all human aerosols exhaled during respiratory activities and therapies. We used a novel chamber with an optical particle counter sampling at 100 l.min-1 to count and size-fractionate close to all exhaled particles (0.5–25 µm). We compared emissions from ten healthy subjects during six respiratory activities (quiet breathing; talking; shouting; forced expiratory manoeuvres; exercise; and coughing) with three respiratory therapies (high-flow nasal oxygen and single or dual circuit non-invasive positive pressure ventilation). Activities were repeated while wearing facemasks. When compared with quiet breathing, exertional respiratory activities increased particle counts 34.6-fold during talking and 370.8-fold during coughing (p < 0.001). High-flow nasal oxygen 60 at l.min-1 increased particle counts 2.3-fold (p = 0.031) during quiet breathing. Single and dual circuit non-invasive respiratory therapy at 25/10 cm.H2O with quiet breathing increased counts by 2.6-fold and 7.8-fold, respectively (both p < 0.001). During exertional activities, respiratory therapies and facemasks reduced emissions compared with activities alone. Respiratory activities (including exertional breathing and coughing) which mimic respiratory patterns during illness generate substantially more aerosols than non-invasive respiratory therapies, which conversely can reduce total emissions. We argue the risk of aerosol exposure is underappreciated and warrants widespread, targeted interventions. 相似文献