全文获取类型
收费全文 | 11891篇 |
免费 | 745篇 |
国内免费 | 60篇 |
专业分类
耳鼻咽喉 | 99篇 |
儿科学 | 182篇 |
妇产科学 | 154篇 |
基础医学 | 1554篇 |
口腔科学 | 200篇 |
临床医学 | 1158篇 |
内科学 | 2824篇 |
皮肤病学 | 394篇 |
神经病学 | 1133篇 |
特种医学 | 653篇 |
外科学 | 1759篇 |
综合类 | 39篇 |
一般理论 | 2篇 |
预防医学 | 525篇 |
眼科学 | 149篇 |
药学 | 692篇 |
中国医学 | 19篇 |
肿瘤学 | 1160篇 |
出版年
2024年 | 8篇 |
2023年 | 56篇 |
2022年 | 113篇 |
2021年 | 223篇 |
2020年 | 166篇 |
2019年 | 234篇 |
2018年 | 277篇 |
2017年 | 230篇 |
2016年 | 298篇 |
2015年 | 350篇 |
2014年 | 454篇 |
2013年 | 592篇 |
2012年 | 970篇 |
2011年 | 944篇 |
2010年 | 643篇 |
2009年 | 546篇 |
2008年 | 875篇 |
2007年 | 937篇 |
2006年 | 893篇 |
2005年 | 858篇 |
2004年 | 737篇 |
2003年 | 643篇 |
2002年 | 659篇 |
2001年 | 111篇 |
2000年 | 71篇 |
1999年 | 108篇 |
1998年 | 102篇 |
1997年 | 98篇 |
1996年 | 68篇 |
1995年 | 68篇 |
1994年 | 40篇 |
1993年 | 59篇 |
1992年 | 20篇 |
1991年 | 31篇 |
1990年 | 16篇 |
1989年 | 23篇 |
1988年 | 15篇 |
1987年 | 18篇 |
1986年 | 17篇 |
1985年 | 13篇 |
1984年 | 14篇 |
1983年 | 13篇 |
1982年 | 17篇 |
1981年 | 14篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1975年 | 7篇 |
1973年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Montesinos-Rongen M Akasaka T Zühlke-Jenisch R Schaller C Van Roost D Wiestler OD Siebert R Deckert M 《Brain pathology (Zurich, Switzerland)》2003,13(4):534-538
Primary central nervous system lymphomas (PCNSL) constitute diffuse large B-cell lymphomas arising in and remaining confined to the brain. Little information is available on cytogenetic changes in PCNSL, and recurrent chromosomal translocations have not yet been identified. Fluorescence in situ hybridization (FISH) of a series of 13 PCNSL from immunocompetent patients revealed 3 cases with signal patterns of a BCL6-specific probe suggesting a breakpoint in this oncogene locus in chromosome band 3q27. Here, we describe cloning of the translocation breakpoints by long-distance inverse polymerase chain reaction (LDI-PCR) in 2 of these tumors. Both breakpoints affected the first intron of BCL6. In one PCNSL, the HSPCA (HSP90A) gene in 14q32.31 was identified as BCL6 partner. In the second lymphoma, the gene encoding glyceraldehyde-3-phosphate dehydrogenase (GAPD) on 12p13.31 was detected as a hitherto unknown partner of BCL6. Our results suggest translocation-mediated BCL6 oncogene activation as a so far unknown pathogenetically relevant mechanism in PCNSL. 相似文献
72.
73.
Enzymatic digestion of adult human articular cartilage yields a small fraction of the total available cells 总被引:1,自引:0,他引:1
Jakob M Démarteau O Schäfer D Stumm M Heberer M Martin I 《Connective tissue research》2003,44(3-4):173-180
We investigated whether different protocols for the digestion of adult human articular cartilage influence the cell yield and capacity to attach and proliferate in culture dishes. Chondrocyte yields were expressed as a percentage of the total number of cells in the tissue, determined both histologically (using the dissector method) and biochemically (measuring the DNA content of tissue digests). Human cartilage specimens (n = 79) were digested using different protocols based on combinations of collagenase II (CGN), trypsin/EDTA, hyaluronidase, and tosyllysylchloromethane (TLCM). Yields of viable chondrocytes were the highest within a specific range of CGN concentrations and digestion times, but always < 22% of the total available cells. The combination of CGN with trypsin/EDTA or TLCM accelerated the digestion process but did not significantly increase cell yields. The percentage of viable cells that attached to culture dishes ranged 75-85% (< 19% of the total) and was reduced by TLCM. Doubling times of attached cells were comparable in all experimental groups. Our results indicate that chondrocyte yields and capacity to attach and proliferate are not highly sensitive to the specific isolation protocol used. However, typically used cartilage digestion protocols yield only a small fraction of the total available cells, possibly introducing an uncontrolled selection of certain chondrocyte subpopulations. 相似文献
74.
Jean-Aimé Simoneau Margit Kaufmann Karl-Thomas Härtner Dirk Pette 《Pflügers Archiv : European journal of physiology》1989,414(6):629-633
This study compares changes in contractile properties, Parvalbumin content, and Ca2+-uptake by the sarcoplasmic reticulum (SR) of low-frequency stimulated rat and rabbit tibialis anterior (TA) muscles. Time to peak tension increased 1.8-fold in 35-day stimulated rabbit TA, while no change occurred in rat TA. Isometric twitch tension increased 2-fold in rabbit TA, but was unaltered in rat TA. Parvalbumin (PA) content was more than 90% reduced in rabbit TA, but only 60% in rat TA after 35 days. At this time, PA content of the stimulated rat TA was still higher than that of normal rabbit TA. Taking into account the suggested role of PA as a cytosolic Ca2+ buffer, its decrease could lead to an impaired free Ca2+-decay with a prolonged active state and a higher tension output during a single twitch. This would explain why chronic stimulation led to an increase in isometric twitch tension in rabbit TA, but not in rat TA. The 1.6-fold rise in half-relaxation time of 35-day stimulated rat and rabbit TA most likely resulted from a 50% reduced Ca2+-uptake by the SR, due to a still unknown modification of the Ca2+-transport ATPase. 相似文献
75.
Copolymers of L -lactide with D -lactide 1 According to IUPAC the name dilactide is preferred to lactide. , glycolide 2 IUPAC name: diglycolide. , ε-caprolactone and trimethylene carbonate, and networks with spiro-bis-dimethylene-carbonate (2,4,7,9-tetraoxaspiro[5.5]undecane-3,8-dione) were prepared in bulk at standardized polymerization conditions. The properties of the nascent copolymers were evaluated with respect to the nature of the comonomer. Copolymerization with comonomers entailing low glass transition temperature simultaneously reduces the crystallinity. 300 MHz 1H nuclear magnetic resonance is shown to be a useful technique for the determination of the average monomer sequence lengths in ε-caprolactone and trimethylene carbonate copolymers. The presence of crystallizable L -lactide sequences, due to differences in monomer reactivity, has a large effect on the thermal properties of the copolymer as well as on the long-term degradation characteristics. 相似文献
76.
Differences in maintenance of CD8+ and CD4+ bacteria-specific effector-memory T cell populations 总被引:1,自引:0,他引:1
Schiemann M Busch V Linkemann K Huster KM Busch DH 《European journal of immunology》2003,33(10):2875-2885
Our knowledge about the kinetics and dynamics of complex pathogen-specific CD8(+) T cell responses and the in vivo development of CD8(+) memory T cells has increased substantially over the past years; in comparison, relatively little is known about the CD4(+) T cell compartment. We monitored and directly compared the phenotypical changes of pathogen (Listeria monocytogenes)-specific CD8(+) and CD4(+) T cell responses under conditions leading to effective and long-lasting protective immunity. We found that the general kinetics of bacteria-specific CD8(+) and CD4(+) T cells during the effector and post-effector phases are synchronized. However, later during the memory phase, CD8(+) and CD4(+) T cell populations differ substantially. Whereas CD8(+) memory T cell populations with immediate effector function are readily detectable in lymphoid and non-lymphoid tissues and remain remarkably stable in size, antigen-specific CD4(+) effector-memory T cells decline continuously in frequency over time. These findings have important implications for the better understanding of the in vivo development of protective immunity towards intracellular pathogens. 相似文献
77.
Rademakers R Melquist S Cruts M Theuns J Del-Favero J Poorkaj P Baker M Sleegers K Crook R De Pooter T Bel Kacem S Adamson J Van den Bossche D Van den Broeck M Gass J Corsmit E De Rijk P Thomas N Engelborghs S Heckman M Litvan I Crook J De Deyn PP Dickson D Schellenberg GD Van Broeckhoven C Hutton ML 《Human molecular genetics》2005,14(21):3281-3292
78.
Dirk Schulze Markus Rapedius Tobias Krauter Thomas Baukrowitz 《The Journal of physiology》2003,552(2):357-367
Phosphatidylinositol phosphates (PIPs, e.g. PIP2 ) and long-chain acyl-CoA esters (e.g. oleoyl-CoA) are potent activators of K atp channels that are thought to link K atp channel activity to the cellular metabolism of PIPs and fatty acids. Here we show that the two types of lipid act by the same mechanism: oleoyl-CoA potently reduced the ATP sensitivity of cardiac (Kir6.2/SUR2A) and pancreatic (Kir6.2/SUR1) K atp channels in a way very similar to PIP2 . Mutations (R54Q, R176A) in the C- and N-terminus of Kir6.2 that greatly reduced the PIP2 modulation of ATP sensitivity likewise reduced the modulation by oleoyl-CoA, indicating that the two lipids interact with the same site. Polyvalent cations reduced the effect of oleoyl-CoA and PIP2 on the ATP sensitivity with similar potency suggesting that electrostatic interactions are of similar importance. However, experiments with differently charged inhibitory adenosine phosphates (ATP4- , ADP3- and 2'(3')- O -(2,4,6-trinitrophenyl)adenosine 5'-monophosphate (TNP-AMP2- )) and diadenosine tetraphosphate (Ap4 A5- ) ruled out a mechanism where oleoyl-CoA or PIP2 attenuate ATP inhibition by reducing ATP binding through electrostatic repulsion. Surprisingly, CoA (the head group of oleoyl-CoA) did not activate but inhibited K atp channels (IC50 = 265 ± 33 μM). We provide evidence that CoA and diadenosine polyphosphates (e.g. Ap4 A) are ligands of the inhibitory ATP-binding site on Kir6.2. 相似文献
79.
Hysterectomy in six European countries 总被引:2,自引:0,他引:2
Gynaecologists have been criticized in recent years because of their attitude towards hysterectomy; it is often stated that they are too ready to consider hysterectomy to be indicated and that hysterectomies are carried out too frequently.In order to obtain insight into the incidence of hysterectomy, 2066 women between 40 and 70 yr of age, composing a sample covering 6 European countries, were asked whether they had undergone this operation. Of the total sample, 11.4% had been hysterectomized, the highest percentage being found in Italy (15.5%) and the lowest in France (8.5%).The most important factor that influenced the relative frequency of hysterectomy was age: the percentage of women who had undergone hysterectomy increased with age up to 55–59 yr, but fell thereafter. Another significant factor was civil status; there were fewer divorcees or widows at the moment of operation than married or never-married women.The relationship between the incidence of hysterectomy and age is a parabolic one. To explain this curve the authors postulate that two trends must have played a rôle: firstly; a greater need for hysterectomy with increasing age and, secondly a decrease in the reluctance of the gynaecological profession to perform a hysterectomy and/or of women to undergo this operation.Statistical analysis confirms the existence of this second trend over the period 1960–1975. The chances of a young woman losing her uterus before her 70th year went up linearly to 19.8% in 1975. By extrapolation a figure of 21% is obtained for 1980. Satisfaction with the result of the operation was lowest in Italy and Germany; satisfaction was also lowest in rural areas. 相似文献
80.
Dr. Thomas Menke Petra Niklowitz Bernhard Schlüter Dirk Buschatz Eckardt Trowitzsch Werner Andler 《Somnologie - Schlafforschung und Schlafmedizin》2003,7(2):37-42
Summary Question of the study Respiratory instability as well as tissue damage by free radicals (oxidative stress) have been hypothesized to play a role in cases of sudden and unexpected infant death in the first year of life. The ratio of the oxidized/reduced form of redox compounds in the circulation could be used as a marker of oxidative stress. Therefore, the sleep apnoea rate and redox status of coenzyme Q10 (CoQ10) (percentage of the oxidized form in total CoQ10) were measured in a population of clinically healthy infants in their first year of life in order to study whether a physiological parameter of respiratory instability is related to a biochemical parameter of oxidative stress. Patients and methods Between May and December 1999, 323 infants in the first year of life were referred to a paediatric sleep laboratory. Sleep apnoea rate, periodic breathing and parameters of oxygenation (SaO2 and TcPO2 ) were calculated based on polysomnographic recordings. The CoQ10 redox status was calculated based on high-pressure liquid chromatographic (HPLC) analysis. Results Statistical analysis showed an age-dependent decrease in apnoea rate ( r = – 0.38) and CoQ10 redox status ( r = – 0.40). An increased CoQ10 redox status (median: 16.6 %; range: 7.3 – 29.7 %) was found in infants with high apnoea rates above the 90th percentile of a reference group in comparison with infants with apnoea rates below the 90th percentile of a reference group (median: 10.4 %; range: 5.1 – 20.4 %; P = 0.031). Conclusions These findings may indicate that high apnoea rates are accompanied by increased formation of free radicals in clinically healthy infants in the first year of life. 相似文献