全文获取类型
收费全文 | 13888篇 |
免费 | 739篇 |
国内免费 | 95篇 |
专业分类
耳鼻咽喉 | 89篇 |
儿科学 | 289篇 |
妇产科学 | 130篇 |
基础医学 | 2220篇 |
口腔科学 | 97篇 |
临床医学 | 1390篇 |
内科学 | 3119篇 |
皮肤病学 | 371篇 |
神经病学 | 1343篇 |
特种医学 | 590篇 |
外科学 | 2076篇 |
综合类 | 48篇 |
一般理论 | 2篇 |
预防医学 | 672篇 |
眼科学 | 227篇 |
药学 | 982篇 |
中国医学 | 42篇 |
肿瘤学 | 1035篇 |
出版年
2023年 | 58篇 |
2022年 | 81篇 |
2021年 | 264篇 |
2020年 | 159篇 |
2019年 | 225篇 |
2018年 | 325篇 |
2017年 | 206篇 |
2016年 | 238篇 |
2015年 | 276篇 |
2014年 | 381篇 |
2013年 | 531篇 |
2012年 | 929篇 |
2011年 | 1054篇 |
2010年 | 616篇 |
2009年 | 546篇 |
2008年 | 892篇 |
2007年 | 1027篇 |
2006年 | 923篇 |
2005年 | 968篇 |
2004年 | 893篇 |
2003年 | 876篇 |
2002年 | 851篇 |
2001年 | 145篇 |
2000年 | 128篇 |
1999年 | 157篇 |
1998年 | 218篇 |
1997年 | 170篇 |
1996年 | 172篇 |
1995年 | 114篇 |
1994年 | 113篇 |
1993年 | 113篇 |
1992年 | 105篇 |
1991年 | 73篇 |
1990年 | 57篇 |
1989年 | 73篇 |
1988年 | 69篇 |
1987年 | 56篇 |
1986年 | 56篇 |
1985年 | 44篇 |
1984年 | 55篇 |
1983年 | 56篇 |
1982年 | 46篇 |
1981年 | 38篇 |
1980年 | 44篇 |
1979年 | 37篇 |
1978年 | 29篇 |
1977年 | 29篇 |
1974年 | 34篇 |
1973年 | 26篇 |
1972年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Paolo Sportoletti Beatrice Del Papa Mariangela De Ioanni Lorenzo Moretti Elisabetta Bonifacio Vania Lanterna Alain Bell Katia Fettucciari Eugenia Carnevali Tiziana Zei Franca Falzetti Massimo F Martelli Antonio Tabilio Mauro Di Ianni 《Biology of blood and marrow transplantation》2006,12(12):1250-1260
T-cell homeostasis is regulated by several molecules; among these, interleukin (IL)-7 plays an essential role in the survival and homeostatic proliferation of peripheral naive T cells. In a previous study, we investigated whether human mesenchymal stromal cells (MSCs) could be engineered with the IL-7 gene to produce functional level of this cytokine. In the present study, we analyzed the impact of different quantities of IL-7 produced by MSCs on the survival and proliferation of a negative immunoselected naive (CD3(+)/CD45RA(+)) T-cell population. Co-cultivation of peripheral naive T cells with MSCs producing low (16 pg/mL) or high (1000 pg/mL) IL-7 levels or in the presence of exogenous IL-7 (0.01 ng/mL and 100 ng/mL) maintained the CD3(+)/CD45RA(+) naive T-cell phenotype. Chemokine receptor CCR7(+) expression was also maintained among this T-cell population. Naive T-cell molecular characteristics were maintained as assessed by the Vbeta spectratyping complexity score, which showed the maintenance of a broad T-cell repertoire. No Th1 or Th2 differentiation was observed, as assessed by interferon-gamma or IL-4 accumulation. In contrast, only MSCs producing high amounts of IL-7 caused increased activation (CD25 31.2% +/- 12% vs 10% +/- 3.5%; P < .05), proliferation (CD71 17.8+/-7% vs 9.3%+/-3, P < .05), apoptosis (assessed by annexin V: 18.6% +/- 5% vs 14.9% +/- 2.6%; P > .05), and the phase S cell cycle (15% vs 6.9%, P > .05). Exogenous IL-7 exhibited no significant effect. In conclusion, we demonstrated that IL-7 produced by MSCs has a dose-independent effect on naive T-cell survival while exerting a dose-dependent effect on activation/proliferation. Due to the continuous production of IL-7 by engineered cells, our system is more efficacious than exogenous IL-7. 相似文献
102.
Jean -Paul Richalet Claude Soulard Alain Nitenberg Bernard Teisseire Jean de Bovée Sadino Séroussi 《European journal of applied physiology》1981,47(1):27-39
Summary Conditions of oxygen extraction by the myocardium have been studied in 12 subjects (44±9 years old) with pure mitral stenosis without clinical, metabolic or electrical sign of coronary insufficiency.Oxygen-hemoglobin equilibrium curves (OHEC) have been determined on arterial, mixed venous and coronary sinus blood, at rest and during a moderate (60 W, 10 min) exercise performed on a bicycle ergometer in supine position. Physiological values, at rest and during exercise, of the following functional parameters of the OHEC were determined in the in-vivo conditions of pH and PCO2P50, nHill, DS max = maximal value of OHEC slope (DS=SO2/PO2), PDS max, SDS max. The concentration of plasma electrolytes capable to modify one of these parameters was controlled in each blood sample.In coronary sinus blood, P50 rises from 27.5±1.7 to 28.9±1.6 Torr during exercise (p<0.01). At rest, Hill's n in myocardial venous blood (2.67±0.09) is significantly higher than in arterial blood (2.61±0.08, p<0.01). A decrease in DS max (2.67±0.20 to 2.53±0.12%. Torr–1; p<0.01) and an increase in PDS max (20.9±1.9 to 22.6±2.1 Torr, p<0.01) are observed. At rest, the myocardial venous point (PcsO2, ScsO2) is not significantly distinct from the maximal slope point (PDS max, SDS max). After 1 min of exercise, a small gap appears which becomes significant at the end of the exercise (PDS max-PcsO2=0.2 Torr at rest, 2.7 Torr after exercise; SDS max-ScsO2=4.1% at rest, 7.9% after exercise). DS value at the myocardial venous point is only 2% at rest and 6% after exercise, lower than its maximal value.The gap between venous point and DS max point could constitute an error signal in the regulation loop of the coronary circulation. The existence of a physiological receptor, sensitive to instant variations in myocardial tissue PO2 and able to maintain venous point near DS max point could be considered. 相似文献
103.
Mory F Carlier JP Alauzet C Thouvenin M Schuhmacher H Lozniewski A 《Journal of clinical microbiology》2005,43(10):5380-5383
Metronidazole resistance among Prevotella spp. is rare. We report here the first case of bacteremia due to a high-level metronidazole-resistant Prevotella sp. responsible for treatment failure. 相似文献
104.
Handra-Luca A Couvelard A Sauvanet A Fléjou JF Degott C 《Virchows Archiv : an international journal of pathology》2004,445(2):203-205
We report an unusual type of mucinous cystadenoma of the pancreas, characterised by a predominantly solid gross appearance due to the presence of an abundant ovarian-type stroma. The tumour, located in the body of the pancreas, was discovered after episodes of acute pancreatitis. It was composed of several mucus-secreting benign cysts placed within a highly cellular ovarian-type stroma, composed of undifferentiated spindle cells with mild atypia but without any increase of mitotic activity and with a low proliferative index. These cells expressed oestrogen and progesterone receptors, but they did not express CD34, CD117, p53 protein or bcl-2. Recognition of this peculiar mainly solid mucinous cystadenoma containing an abundant ovarian-type stroma is difficult. It is conceivable that the mesenchymal component described in our case could represent an early stage in the development of sarcoma in mucinous cystadenoma of the pancreas. 相似文献
105.
Mehnert P Malchaire J Kampmann B Piette A Griefahn B Gebhardt H 《European journal of applied physiology》2000,82(1-2):52-60
The prediction of the mean skin temperature used for the Required Sweat Rate index was criticised for not being valid in
conditions with high radiation and high humidity. Based on a large database provided by 9 institutes, 1999 data points obtained
using steady-state conditions, from 1399 experiments and involving 377 male subjects, were used for the development of a new
prediction model. The observed mean skin temperatures ranged from 30.7 °C to 38.6 °C. Experimental conditions included air
temperatures (T
a) between 20 and 55 °C, mean radiant temperatures (T
r) up to 145 °C, partial vapour pressures (P
a) from 0.2 to 5.3 kPa, air velocities (v
a) between 0.1 and 2 m/s, and metabolic rates (M) from 102 to 620 W. Rectal temperature (T
re) was included in the models to increase the accuracy of prediction. Separate models were derived for nude (clothing insulation,
Icl, ≤0.2 clo, where 1 clo=0.155 m2 · °C · W−1, which is equivalent to the thermal insulation of clothing necessary to maintain a resting subject in comfort in a normally
ventilated room, air movement=10 cm/s, at a temperature of 21 °C and a humidity of less than 50%) and clothed (0.6 ≤ Icl ≤ 1.0 clo) subjects using a multiple linear regression technique with re-sampling (non-parametric bootstrap). The following
expressions were obtained for nude and clothed subjects, respectively: T
sk=7.19 + 0.064T
a + 0.061T
r + 0.198P
a− 0.348v
a + 0.616T
re and T
sk=12.17 + 0.020T
a + 0.044T
r + 0.194P
a − 0.253v
a + 0.0029M + 0.513T
re. For the nude and clothed subjects, 83.3% and 81.8%, respectively, of the predicted skin temperatures were within the range
of ±1 °C of the observed skin temperatures. It is concluded that the proposed models for the prediction of the mean skin temperature
are valid for a wide range of warm and hot ambient conditions in steady-state conditions, including those of high radiation
and high humidity.
Accepted: 7 February 2000 相似文献
106.
Vergu E Mallet A Golmard JL 《Journal of acquired immune deficiency syndromes (1999)》2002,30(3):263-270
OBJECTIVE: To study the role of resistance characteristics of viral mutants in the prediction of virologic and immunologic response to antiretroviral therapy in HIV-infection. METHODS: This study is based on a mathematical model that generates viral and immunologic dynamics of HIV infection, taking into account drug-resistant mutants and therapy. We analyzed predictive factors of the increase in CD4 cell count and of the decrease in viral load from baseline after 6 months of HAART on a sample of 300 simulated individuals. The set of potential predictors was constituted by patients' state at initiation of therapy and by resistance characteristics of viral strains at that time. Predictive models, obtained by stepwise regression, were selected and compared using Mallows' Cp criterion. RESULTS: In addition to baseline viral load and CD4 cell count, known to influence response to therapy, baseline CD8 cell count and resistance characteristics of detectable strains are shown to improve the accuracy of the prediction. On the contrary, resistance parameters of low frequency viral mutants have no predictive value. CONCLUSIONS: Characteristics of preexisting detectable resistant mutants as determinants of virologic and immunologic response to antiretroviral therapy increase the capacity to predict the outcome of the treatment. Therefore, the use of phenotypic and genotypic testing could be crucial and should be considered for the choice of therapy. 相似文献
107.
Lura Brianna Caddle Jeremy L. Grant Jin Szatkiewicz Johann van Hase Bobbi-Jo Shirley Joerg Bewersdorf Christoph Cremer Alain Arneodo Andre Khalil Kevin D. Mills 《Chromosome research》2007,15(8):1061-1073
Radiation exposure is an occupational hazard for military personnel, some health care professionals, airport security screeners,
and medical patients, with some individuals at risk for acute, high-dose exposures. Therefore, the biological effects of radiation,
especially the potential for chromosome damage, are major occupational and health concerns. However, the biophysical mechanisms
of chromosome instability subsequent to radiation-induced DNA damage are poorly understood. It is clear that interphase chromosomes
occupy discrete structural and functional subnuclear domains, termed chromosome territories (CT), which may be organized into
‘neighborhoods’ comprising groups of specific CTs. We directly evaluated the relationship between chromosome positioning,
neighborhood composition, and translocation partner choice in primary lymphocytes, using a cell-based system in which we could
induce multiple, concentrated DNA breaks via high-dose irradiation. We critically evaluated mis-rejoining profiles and tested
whether breaks occurring nearby were more likely to fuse than breaks occurring at a distance. We show that CT neighborhoods
comprise heterologous chromosomes, within which inter-CT distances directly relate to translocation partner choice. These
findings demonstrate that interphase chromosome arrangement is a principal factor in genomic instability outcomes in primary
lymphocytes, providing a structural context for understanding the biological effects of radiation exposure, and the molecular
etiology of tumor-specific translocation patterns. 相似文献
108.
Control of interneurone firing pattern by axonal autoreceptors in the juvenile rat cerebellum 总被引:2,自引:0,他引:2
Recent work has shown that certain neurones have axonal GABAA receptors, whose tonic activation modifies their firing properties and neurotransmitter release capability. In addition, results obtained in interneurones of the molecular layer of the cerebellum indicate that action potential-released GABA binds back to the axon that released it, generating an autoreceptor current. In the present paper, we show that at physiological Cl− i concentration (15 m m ) and at 34–36°C, the autoreceptor current generates a large amplitude (up to 21 mV) afterdepolarization that lasts for about 150 ms, and that occasionally leads to double firing. Furthermore we show that elimination of the afterdepolarization, by either blocking GABAA receptors, or eliminating the autoreceptor currents through prolonged whole-cell recording, decreases burst firing. I h (a hyperpolarization-activated current) was previously found to be prominent in interneurone axons. We show that blocking I h leads to an increase in the amplitude of the autoreceptor current as well as of the associated afterdepolarization, suggesting a shunting effect of I h on autoreceptor-mediated afterdepolarization. Conversely, blocking I h accentuates burst firing. The effects of autoreceptor-mediated afterdepolarization on firing are prominent during a period of development when interneurone synapses are stabilized and vanish by postnatal day 17 (PN 17), together with the expression of the autoreceptor current. Altogether, this work reveals a new role for autoreceptors in the regulation of cell excitability and firing pattern, which may contribute to the development and stabilization of the cerebellar network. 相似文献
109.
Philippe Hup Cline Rouveirol Isabel Brito Pierre Neuvial Philippe La Rosa Eric Viara Nicolas Stransky Gaëlle Pierron Elodie Mani Caroline Brennetot Isabelle Jannoueix Nadge Gruel Alain Aurias Olivier Delattre Franois Radvanyi Emmanuel Barillot 《European journal of medical genetics》2005,48(4):467-468
110.
Association of DLG5 R30Q variant with inflammatory bowel disease 总被引:6,自引:0,他引:6
Daly MJ Pearce AV Farwell L Fisher SA Latiano A Prescott NJ Forbes A Mansfield J Sanderson J Langelier D Cohen A Bitton A Wild G Lewis CM Annese V Mathew CG Rioux JD 《European journal of human genetics : EJHG》2005,13(7):835-839
Crohn's disease (CD) and ulcerative colitis (UC) are chronic inflammatory diseases of the gastrointestinal system known as the inflammatory bowel diseases (IBD). Recently, Stoll and colleagues reported a novel finding of genetic variation in the DLG5 gene that is associated with IBD (CD and UC combined). We present here a study of the genetic variation described in that report in two well-powered, independent case-control cohorts and one family-based collection, and confirm the proposed association between IBD and the R30Q variant of DLG5 in two of the three studies. We are, however, unable to replicate the other proposed association to the common haplotype described in Stoll et al and suggest that this other finding could conceivably have been partially a statistical fluctuation and partially a result of LD with the replicated R30Q association. This study provides support for the hypothesis that DLG5 constitutes a true IBD risk factor of modest effect. 相似文献