全文获取类型
收费全文 | 27830篇 |
免费 | 2205篇 |
国内免费 | 44篇 |
专业分类
耳鼻咽喉 | 293篇 |
儿科学 | 1012篇 |
妇产科学 | 703篇 |
基础医学 | 3829篇 |
口腔科学 | 763篇 |
临床医学 | 3049篇 |
内科学 | 5581篇 |
皮肤病学 | 554篇 |
神经病学 | 2250篇 |
特种医学 | 1052篇 |
外国民族医学 | 3篇 |
外科学 | 3926篇 |
综合类 | 406篇 |
一般理论 | 43篇 |
预防医学 | 2560篇 |
眼科学 | 461篇 |
药学 | 1789篇 |
1篇 | |
中国医学 | 36篇 |
肿瘤学 | 1768篇 |
出版年
2022年 | 216篇 |
2021年 | 491篇 |
2020年 | 352篇 |
2019年 | 541篇 |
2018年 | 599篇 |
2017年 | 473篇 |
2016年 | 493篇 |
2015年 | 567篇 |
2014年 | 767篇 |
2013年 | 996篇 |
2012年 | 1465篇 |
2011年 | 1556篇 |
2010年 | 852篇 |
2009年 | 723篇 |
2008年 | 1360篇 |
2007年 | 1422篇 |
2006年 | 1358篇 |
2005年 | 1320篇 |
2004年 | 1132篇 |
2003年 | 1132篇 |
2002年 | 978篇 |
2001年 | 799篇 |
2000年 | 771篇 |
1999年 | 643篇 |
1998年 | 275篇 |
1997年 | 247篇 |
1996年 | 250篇 |
1995年 | 255篇 |
1994年 | 240篇 |
1993年 | 212篇 |
1992年 | 604篇 |
1991年 | 568篇 |
1990年 | 510篇 |
1989年 | 493篇 |
1988年 | 457篇 |
1987年 | 408篇 |
1986年 | 373篇 |
1985年 | 440篇 |
1984年 | 326篇 |
1983年 | 290篇 |
1982年 | 188篇 |
1979年 | 229篇 |
1978年 | 207篇 |
1977年 | 159篇 |
1976年 | 164篇 |
1975年 | 166篇 |
1974年 | 177篇 |
1973年 | 210篇 |
1972年 | 173篇 |
1971年 | 157篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
191.
Group A Streptococcal Antibodies in Subjects with or without Rheumatic Fever in Areas with High or Low Incidences of Rheumatic Fever
下载免费PDF全文
![点击此处可从《Clinical and Vaccine Immunology : CVI》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Elia M. Ayoub Beverly Nelson Stanford T. Shulman Douglas J. Barrett J. Douglas Campbell George Armstrong John Lovejoy Gerald H. Angoff Sol Rockenmacher 《Clinical and Vaccine Immunology : CVI》2003,10(5):886-890
The levels of streptococcal antibody titers in populations with or without rheumatic fever from an area with a relatively high incidence of rheumatic fever and an area with a low incidence of this disease were compared. Streptococcal antibody titers were determined for two populations, each of which included children without rheumatic fever (nonrheumatic children) and rheumatic fever patients. The two populations were derived from two separate geographic areas, one with a high incidence of rheumatic fever (Grenada) and another with a low incidence of this disease (central Florida). The results revealed an absence of consistent differences in the geometric mean antibody titers between the nonrheumatic subjects and the rheumatic fever patients from Grenada. In the population from Grenada, the mean anti-streptolysin O and anti-DNase B titers were higher in the nonrheumatic controls (P of 0.085 and 0.029, respectively). However, the mean titer of the antibody to the group A streptococcal cell wall carbohydrate was higher in the rheumatic fever patients than in the nonrheumatic controls (P = 0.047). This finding contrasted with the finding that the means of all three streptococcal antibody titers in the patients with rheumatic fever were significantly higher than those in the nonrheumatic subjects from Florida (P = 0.01-<0.001). The reason for this paradoxical finding became evident when the streptococcal antibody titers of the nonrheumatic subjects from Grenada and Florida were compared, revealing significantly higher levels of all three antibodies in the nonrheumatic subjects from Grenada than in the nonrheumatic subjects from Florida (P < 0.001). These results suggest that nonrheumatic individuals in an area with a high incidence of rheumatic fever have inordinately elevated levels of streptococcal antibodies in serum. The presence of elevated streptococcal antibody titers in such a population, which probably reflects a high background prevalence of streptococcal infections, should be taken into consideration when evaluating the role of the group A streptococcus in nonpurulent complications of infections. 相似文献
192.
Melanotic lesions in the internal organs of miniature swine 总被引:4,自引:0,他引:4
193.
Summary The effects on heart rate, oxygen uptake, and pulmonary ventilation of muscular exercises, including both dynamic contractions, either simple or combined, were studied in 4 male subjects, aged 21 to 23 years. The dynamic work consisted in cycling on an ergometric bicycle at three power levels: 40, 80, and 100 W. The static work consisted in pushing against, pulling and holding with the arms a 6, 9, 12, or 18 kg load. The physiological effects are expressed as cardiac cost (HR), oxygen cost (VO2) and ventilation cost (V). The physiological cost of the combined work increases according to the cycling power and to the isometric load developed. A statistical analysis shows that the costs of combined work are not different from the sum of the costs of the static and dynamic contractions measured separately. Thus, the physiological responses to the combinations investigated are of an additive type. 相似文献
194.
The repopulation of lymph nodes of dogs after 1200 R whole-body x-irradiation and intravenous administration of mononuclear blood leukocytes.
下载免费PDF全文
![点击此处可从《The American journal of pathology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
B. Nelson W. Calvo T. M. Fliedner E. Herbst C. Bruch H. P. Schnappauf H. D. Flad 《The American journal of pathology》1976,84(2):259-282
Fresh and cryopreserved autologous or allogeneic mononuclear blood cells (MBCs) intravenously injected in 1200 R total-body x-irradiated dogs repopulated lymph nodes within 10 days after tranfusion. Several parameters of the lymphopoietic regeneration were correlated with the number of cells transfused and with the number of colony-forming units contained in the cell suspension when they were cultured in agar (CFUc). Values within the normal or close to normal range were reached in the mesenteric nodes of most of the animals transfused with 10 X 10(9) MBC or more. These values were obtained when 5 X 10(5) CFUc or more were transfused. Axillary nodes showed lower values than mesenteric nodes. They were mostly under the normal range but well over those of the irradiated controls. Frozen and thawed MBCs seem to be as effective as fresh cells for lymphopoietic restoration. The mesenteric nodes of dogs transfused with allogeneic MBCs showed higher cellularity and larger cortical-paracortical areas than those of dogs tranfused with approximately the same number of autologous cells. The repopulation of lymph nodes parallels that of the marrow. 相似文献
195.
J. L. Hedrick K. Carter M. Sanchez R. Di Pietro S. Swanson S. Jayaraman J. G. McGrath 《Macromolecular chemistry and physics.》1997,198(2):549-559
A new route for the synthesis of high glass transition temperature, thermally stable polymer foams has been developed, using compositionally asymmetric microphase-separated block copolymers where the minor component (poly(propylene oxide)) is thermally labile and the major component (polyimide) is thermally stable. The minor component decomposes to low molecular weight species upon heating, and the decomposition products diffuse out of the film, leaving behind pores embedded in a matrix of the thermally stable component. In this study, the polyimide block was crosslinked with ethynyl functionalities to obtain a stable porous structure. The decomposition of the propylene oxide in the block copolymer was studied by thermogravimetric, dynamic mechanical and thermomechanical analyses. Mild conditions were required to avoid rapid depolymerization of the propylene oxide and plasticization of the polyimide matrix. The foams showed pore sizes with diameters up to a micrometer in size as well as the expected reduction in the mass density. 相似文献
196.
Lack of coordinated changes in metabolic enzymes and myosin heavy chain isoforms in regenerated muscles of trained rats 总被引:3,自引:0,他引:3
Bigard AX Mateo P Sanchez H Serrurier B Ventura-Clapier R 《Journal of muscle research and cell motility》2000,21(3):269-278
We investigated training-induced changes in biochemical properties and myosin heavy chain (MHC) composition of regenerated (cardiotoxin-injected) plantaris muscles (PLA) in rats either maintained sedentary (S, n = 9) or endurance trained on a treadmill over a 8-week period (T, n = 7). Both endurance training and regeneration altered the pattern of fast MHC expression. An analysis of the two-way interaction between training and regeneration showed that the relative content of type IIa MHC was affected (P < 0.05). The 140% increase in type IIa MHC observed in regenerated PLA from T rats compared with nontreated muscle of S rats, exceeded the 102% increase resulting from the combination of regeneration alone (26%) and training alone (61%). A similar interaction between training and regeneration was shown for the percentage of fibres expressing either type IIa or type IIb MHC (P < 0.05). In contrast, a significant increase in the citrate synthase (CS) activity was shown in PLA as a result of endurance training, without specific effect of regeneration. Furthermore, training-induced changes in CK and LDH isoenzyme distribution occurred to a similar extent in regenerated and non-treated PLA muscles, and thus did not follow the changes in MHC isoforms. An increase in the mitochondrial CK isozyme activity (mi-CK) was shown in both non-treated and previously degenerated PLA muscles (123 and 117%, P < 0.01, respectively), without specific effect of regeneration. The ratio of mi-CK to CS activity, an estimate of the mitochondrial specific activity of mi-CK was significantly increased by training (P < 0.02) and decreased by regeneration (P < 0.05). Taken together, these data suggest that while training and regeneration have cumulative effects on the pattern of fast MHC expression, the training-induced changes in the energy metabolism shown in mature non-treated myofibres are similar to those observed in regenerated fibres. 相似文献
197.
Daniel L. Hamilos MD John J. Oppenheimer MD Harold S. Nelson MD Sally Wenzel MD Sue Driscoll RN Richard F. Lockey MD David B. K. Golden MD Leland Fan MD Ralph J. Sanks RPh S. Allen Bock MD John W. Yunginger MD Donald Stevenson MD Timothy Sullivan MD Thomas Corbridge MD 《The Journal of allergy and clinical immunology》1993,91(6)
These guidelines are intended to reduce the potential for serious or life-threatening reactions when clinical research is conducted. The following issues were addressed: identifying the risks involved in the research, providing adequate safeguards in the protocol design and during withholding of medication, anticipating risks, minimizing the chances for human error, providing resuscitative equipment sufficient to deal with the most serious anticipated life-threatening reactions, planning for medical support in case of a life-threatening emergency, and optimizing the use of medical personnel and expertise to handle emergency situations. The guidelines also discuss important general issues about protocol design and implementation and the human subject consent form, which should facilitate the approval of protocols by the governing institutional review board.The guidelines are not meant to be inflexible or applicable to all research situations. However, it is our hope that they will allow for clinical research to be conducted in a manner that affords the research subjects a high degree of protection from unnecessary and possibly fatal injuries. 相似文献
198.
Coating hydroxyapatite (HA) onto metal implant surfaces using the plasma-spraying technique has been investigated in several laboratories as a means of improving the mechanical properties of the bulk ceramic. This study describes crystallographic changes which can occur during the plasma-spraying of calcium phosphate powders. A precipitated calcium-deficient apatite and a high temperature near-stoichiometric HA were each sprayed onto metal substrate in an argon plasma using several hydrogen gas flow conditions at various temperatures. The surfaces were examined by X-ray diffraction and scanning electron microscopy. The plasma-sprayed products were identified as a mixture of calcium phosphates including HA, beta-tricalcium phosphate (beta-TCP) and calcium oxide. Stoichiometric HA when plasma-sprayed showed the least (5%) degradation. Since beta-TCP is more resorbable than HA in vivo, varying the HA/beta-TCP ratio on the plasma-sprayed surface may provide a method to control surface dissolution of the coating. 相似文献
199.
Williams GC McGregor HA King D Nelson CC Glasgow RE 《Patient education and counseling》2005,57(1):39-45
There is considerable variation in care provided to patients with diabetes related to metabolic control, preventive services, and degree of patient-centered support. This study evaluates the relation of self-determination theory (SDT) constructs of clinician autonomy support, and patient competence to glycemic control, depressive symptoms, and patient satisfaction from baseline surveys of 634 patients of 31 Colorado primary care physicians participating in a program to improve diabetes care. Spearman correlations of autonomy support from one's clinician with patient competence, HbA1c, depressive symptoms and satisfaction were significant (R = -0.11 to 0.55, P < 0.005). Structural equation modeling demonstrated that autonomy support was significantly related to perceived competence, depressive symptoms, patient satisfaction, and indirectly to glycemic control. Perceived competence was significantly related to depressive symptoms, patient satisfaction and glycemic control. Further, the motivation constructs from SDT accounted for 5% of the variance in glycemic control, 8% of the variance in depression, and 42% of the variance in patient satisfaction. Quality improvement efforts need to pay greater attention to patient competence, satisfaction, and depression, in addition to glycemic control. Clinician autonomy support was found to be reliably measured and moderately correlated with psychosocial and biologic outcomes related to diabetes self-management. These results suggest training clinicians to increase their support of patient autonomy may be one important avenue to improve diabetes outcomes. 相似文献
200.