全文获取类型
收费全文 | 4306篇 |
免费 | 440篇 |
国内免费 | 8篇 |
专业分类
耳鼻咽喉 | 39篇 |
儿科学 | 79篇 |
妇产科学 | 162篇 |
基础医学 | 539篇 |
口腔科学 | 58篇 |
临床医学 | 494篇 |
内科学 | 693篇 |
皮肤病学 | 78篇 |
神经病学 | 346篇 |
特种医学 | 133篇 |
外科学 | 777篇 |
综合类 | 132篇 |
一般理论 | 10篇 |
预防医学 | 436篇 |
眼科学 | 90篇 |
药学 | 320篇 |
中国医学 | 5篇 |
肿瘤学 | 363篇 |
出版年
2022年 | 32篇 |
2021年 | 112篇 |
2020年 | 63篇 |
2019年 | 109篇 |
2018年 | 105篇 |
2017年 | 94篇 |
2016年 | 71篇 |
2015年 | 73篇 |
2014年 | 114篇 |
2013年 | 154篇 |
2012年 | 226篇 |
2011年 | 212篇 |
2010年 | 131篇 |
2009年 | 102篇 |
2008年 | 199篇 |
2007年 | 203篇 |
2006年 | 187篇 |
2005年 | 182篇 |
2004年 | 164篇 |
2003年 | 166篇 |
2002年 | 160篇 |
2001年 | 112篇 |
2000年 | 98篇 |
1999年 | 98篇 |
1998年 | 40篇 |
1997年 | 42篇 |
1996年 | 40篇 |
1995年 | 46篇 |
1994年 | 29篇 |
1993年 | 38篇 |
1992年 | 87篇 |
1991年 | 88篇 |
1990年 | 71篇 |
1989年 | 69篇 |
1988年 | 53篇 |
1987年 | 70篇 |
1986年 | 55篇 |
1985年 | 52篇 |
1984年 | 59篇 |
1983年 | 45篇 |
1982年 | 30篇 |
1981年 | 37篇 |
1979年 | 45篇 |
1978年 | 34篇 |
1977年 | 31篇 |
1973年 | 32篇 |
1972年 | 33篇 |
1970年 | 28篇 |
1969年 | 43篇 |
1968年 | 34篇 |
排序方式: 共有4754条查询结果,搜索用时 234 毫秒
61.
Sánchez-Partida LG Windsor DP Eppleston J Setchell BP Maxwell WM 《Journal of andrology》1999,20(2):280-288
The fertility of ewes after artificial insemination and the relationship between fertility and motility characteristics assessed by a computerized motility analysis system were examined with ram semen frozen in diluents reported to improve postthaw motility. The percentages of motile and progressive spermatozoa were better when frozen in proline- or glycine betaine-containing or HEPES-based, rather than Tris-based, diluents (P < 0.01). The fertility of spermatozoa frozen in diluents containing proline or glycine betaine was slightly reduced, whereas when both compatible solutes were present, the reduction was more pronounced, in comparison with semen frozen in Tris- or HEPES-based diluents (9.5 versus 71.1 and 66.6%; P < 0.01). Fertility of frozen-thawed spermatozoa was higher after laparoscopic insemination than after cervical or transcervical insemination (P < 0.01). Similarly, higher fertility was obtained after cervical insemination with fresh than with frozen-thawed semen (32.4 versus 11.3%; P < 0.01). Furthermore, loss of embryos was lower after laparoscopic insemination of ewes with semen frozen in a Tris diluent than with semen frozen in proline diluents, in glycine betaine diluents, or in proline-plus-glycine betaine diluents (0.0 versus 26.0, 38.5, and 60.0%; P < 0.001). A wide variation in the postthaw percentage of motile (31.6-59.7%) and progressive (22.6-43.1%) spermatozoa and in the fertility of spermatozoa from individual rams was also observed after laparoscopic (29.2-59.7%) or cervical insemination (8.7-30.5%). Postthaw motility results from immediately after thawing and fertility results from experiments where intrauterine insemination was performed with semen frozen in proline- or glycine betaine-containing or HEPES- or Tris-based diluents were pooled and subjected to a pairwise correlation procedure. The correlation analysis showed relationships between some of the motility characteristics (P < 0.01), but there were no relationships between the motility characteristics and fertility. 相似文献
62.
63.
Maxwell RA Gibson JB Fabian TC Proctor KG 《The Journal of trauma》2000,49(2):200-9; discussion 209-11
BACKGROUND: The purpose of this study was to test whether polynitroxylation (PN) improved the therapeutic profile of hemoglobin-based oxygen-carrying compounds (HBOCs) that were unpolymerized (alphaalphaHb) or 70% polymerized (polyHb) in a clinically relevant model that combines pulmonary injury and reperfusion. To our knowledge, four different HBOC formulations have never been compared in the same trauma model. METHODS: Anesthetized, ventilated swine (n = 45) received a unilateral lung contusion + 25% hemorrhage. After 60 minutes, 250 mL of either PNalphaalphaHb (n = 5), alphaalphaHb (n = 10), PNpolyHb (n = 6), polyHb (n = 5), or normal saline (NaCl, n = 10) was administered for 20 minutes, followed by standard crystalloid resuscitation for 30 minutes, and supplemental crystalloid as required for 6 hours to maintain heart rate <100 beats/min and mean arterial pressure >70 mm Hg. RESULTS: Nine of 45 deaths occurred before resuscitation. Survival time was 395 minutes with NaCl versus 303 minutes with alphaalphaHb (p = 0.03) or 238 minutes with PNalphaalphaHb (p = 0.04). With both polymerized HBOCs, survival was 480 minutes (polyHb vs. alphaalphaHb, p = 0.005; PNpolyHb vs. PNalphaalphaHb, p = 0.006). All HBOCs were pressors (all p < 0.05) and all reduced the supplemental fluid required to maintain systemic hemodynamics during resuscitation (all p < 0.05). By 90 minutes postresuscitation, cardiac index was 112% of baseline with NaCl (p < 0.02), but was 78% with alphaalphaHb (p = not significant), 63% with PNalphaalphaHb (p < 0.01), 79% with PNpolyHb (p < 0.01), and 67% with polyHb p < 0.02). Relative to NaCI, no HBOC altered trauma-induced neutrophilia, thrombocytopenia, or the trauma-induced increases in bronchoalveolar lavage protein or bronchoalveolar lavage neutrophils. CONCLUSION: After resuscitation from chest trauma, we observed the following: (1) all HBOCs reduced fluid requirements and increased right and left ventricular afterload versus NaCl, which further compromised an already marginal cardiac performance; (2) mortality was less with polyHbs relative to alphaalphaHb, but the pressor action was unchanged; (3) the pressor action was less with polynitroxylated compounds relative to the unmodified HBOC, but this chemical modification had no effect on mortality; and (4) the pressor action of HBOCs must be attenuated by strategies other than polymerization or polynitroxylation for these compounds to be safe, effective resuscitants in humans. 相似文献
64.
Christina R Maxwell Yuling Liang Bryanne D Weightman Stephen J Kanes Ted Abel Raquel E Gur Bruce I Turetsky Warren B Bilker Robert H Lenox Steven J Siegel 《Neuropsychopharmacology》2004,29(4):739-746
Auditory evoked potentials have been used in a variety of animal models to assess information-processing impairments in schizophrenia. Previous mouse models have primarily employed a paired click paradigm to assess the transient measures of auditory gating. The current study uses stimulus trains at varied interstimulus intervals (ISI) between 0.25 and 8 s in mice to assess the effects of chronic olanzapine and haloperidol on auditory processing. Data indicate that olanzapine increases the amplitude of the N40, P80, and P20/N40 components of the auditory evoked potential, whereas haloperidol had no such effect. The ISI paradigm also allowed for an evaluation of several components of the mouse evoked potential to assess those that display response properties similar to the human P50 and N100. Data suggest that the mouse N40 displays an ISI response relationship that shares characteristics with the human N100, whereas the P20 appears more consistent with the human P50 across the ISI range evaluated in this task. This study suggests that olanzapine may help improve N100 impairments seen in schizophrenia, while haloperidol does not. 相似文献
65.
PARP inhibitor rucaparib induces changes in NAD levels in cells and liver tissues as assessed by MRS
下载免费PDF全文
![点击此处可从《NMR in biomedicine》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Gilberto S. Almeida Carlo M. Bawn Martin Galler Ian Wilson Huw D. Thomas Suzanne Kyle Nicola J. Curtin David R. Newell Ross J. Maxwell 《NMR in biomedicine》2017,30(9)
Poly(adenosine diphosphate ribose) polymerases (PARPs) are multifunctional proteins which play a role in many cellular processes. Namely, PARP1 and PARP2 have been shown to be involved in DNA repair, and therefore are valid targets in cancer treatment with PARP inhibitors, such as rucaparib, currently in clinical trials. Proton magnetic resonance spectroscopy (1H‐MRS) was used to study the impact of rucaparib in vitro and ex vivo in liver tissue from mice, via quantitative analysis of nicotinamide adenosine diphosphate (NAD+) spectra, to assess the potential of MRS as a biomarker of the PARP inhibitor response. SW620 (colorectal) and A2780 (ovarian) cancer cell lines, and PARP1 wild‐type (WT) and PARP1 knock‐out (KO) mice, were treated with rucaparib, temozolomide (methylating agent) or a combination of both drugs. 1H‐MRS spectra were obtained from perchloric acid extracts of tumour cells and mouse liver. Both cell lines showed an increase in NAD+ levels following PARP inhibitor treatment in comparison with temozolomide treatment. Liver extracts from PARP1 WT mice showed a significant increase in NAD+ levels after rucaparib treatment compared with untreated mouse liver, and a significant decrease in NAD+ levels in the temozolomide‐treated group. The combination of rucaparib and temozolomide did not prevent the NAD+ depletion caused by temozolomide treatment. The 1H‐MRS results show that NAD+ levels can be used as a biomarker of PARP inhibitor and methylating agent treatments, and suggest that in vivo measurement of NAD+ would be valuable. 相似文献
66.
67.
68.
69.
70.
The synthesis of 14C‐labeled, 13CD2‐labeled saxagliptin,and its 13CD2‐labeled 5‐hydroxy metabolite
下载免费PDF全文
![点击此处可从《Journal of labelled compounds & radiopharmaceuticals》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Scott B. Tran Brad D. Maxwell Kai Cao Samuel J. Bonacorsi 《Journal of labelled compounds & radiopharmaceuticals》2014,57(3):136-140
14C‐labeled saxagliptin, 13CD2‐labeled saxagliptin, and its 13CD2‐labeled 5‐hydroxy metabolite were synthesized to further support development of the compound for biological studies. This paper describes new syntheses leading to the desired compounds. A total of 3.0 mCi of 14C‐labeled saxagliptin was obtained with a specific activity of 53.98 μCi/mg (17.13 mCi/mmol). The radiochemical purity determined by HPLC was 99.29%, and the overall radiochemical yield was 3.0% based upon 100 mCi of [14C]CH2I2 starting material. By following similar synthetic routes, 580.0 mg of 13CD2‐labeled saxagliptin and 153.1 mg of 13CD2‐labeled 5‐hydroxysaxagliptin metabolite were prepared. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献