全文获取类型
收费全文 | 152814篇 |
免费 | 12233篇 |
国内免费 | 4988篇 |
专业分类
耳鼻咽喉 | 1061篇 |
儿科学 | 2847篇 |
妇产科学 | 1466篇 |
基础医学 | 23636篇 |
口腔科学 | 2956篇 |
临床医学 | 15276篇 |
内科学 | 20171篇 |
皮肤病学 | 1494篇 |
神经病学 | 7316篇 |
特种医学 | 3149篇 |
外国民族医学 | 22篇 |
外科学 | 12613篇 |
综合类 | 24159篇 |
现状与发展 | 11篇 |
一般理论 | 25篇 |
预防医学 | 10799篇 |
眼科学 | 4188篇 |
药学 | 16454篇 |
15篇 | |
中国医学 | 7904篇 |
肿瘤学 | 14473篇 |
出版年
2024年 | 319篇 |
2023年 | 1812篇 |
2022年 | 3861篇 |
2021年 | 5344篇 |
2020年 | 4720篇 |
2019年 | 4883篇 |
2018年 | 4786篇 |
2017年 | 4754篇 |
2016年 | 4890篇 |
2015年 | 4943篇 |
2014年 | 7714篇 |
2013年 | 8673篇 |
2012年 | 7267篇 |
2011年 | 8415篇 |
2010年 | 7315篇 |
2009年 | 7196篇 |
2008年 | 7249篇 |
2007年 | 8335篇 |
2006年 | 7664篇 |
2005年 | 7702篇 |
2004年 | 6747篇 |
2003年 | 5989篇 |
2002年 | 4423篇 |
2001年 | 4392篇 |
2000年 | 3579篇 |
1999年 | 3340篇 |
1998年 | 2356篇 |
1997年 | 2082篇 |
1996年 | 2195篇 |
1995年 | 2102篇 |
1994年 | 1847篇 |
1993年 | 1688篇 |
1992年 | 1443篇 |
1991年 | 1256篇 |
1990年 | 1049篇 |
1989年 | 990篇 |
1988年 | 933篇 |
1987年 | 714篇 |
1986年 | 533篇 |
1985年 | 607篇 |
1984年 | 635篇 |
1983年 | 396篇 |
1982年 | 491篇 |
1981年 | 418篇 |
1980年 | 361篇 |
1979年 | 301篇 |
1978年 | 247篇 |
1977年 | 201篇 |
1976年 | 237篇 |
1975年 | 149篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Hwang JL Huang LW Hsieh BC Tsai YL Huang SC Chen CY Hsieh ML Chen PH Lin YH 《Human reproduction (Oxford, England)》2003,18(1):45-49
BACKGROUND: The introduction of GnRH antagonists such as cetrorelix acetate has made possible the simplification of ovarian stimulation. However, the most effective protocol for their administration has not yet been clearly defined. METHODS: Forty women with male-factor infertility undergoing 40 ICSI cycles were included in the study. Clomiphene citrate at 100 mg a day was given from cycle day 3 through day 7. hMG at 150 IU was given on cycle days 4, 6 and 8, and was adjusted from day 9 according to the follicular and hormone responses. Cetrorelix acetate at 2.5 mg was administered when the leading follicle reached 14 mm. The remaining 0.5 mg was divided into two 0.25 mg injections for possible later use. Serum FSH, LH, estradiol and progesterone levels were measured daily from the day of cetrorelix acetate injection until hCG was given. RESULTS: Serum LH level was suppressed effectively for 4 days. Four patients (10%) needed one or two additional injections of 0.25 mg cetrorelix acetate. No premature LH surge was detected in any of the women treated. Sixteen women became pregnant (40%), of which 14 pregnancies (35%) were ongoing at the time of writing. CONCLUSIONS: This study demonstrates that this new protocol is feasible for couples with male-factor infertility undergoing ICSI. 相似文献
992.
A novel serine protease of the mammalian HtrA family is up-regulated in mouse uterus coinciding with placentation 总被引:2,自引:0,他引:2
Nie GY Li Y Minoura H Batten L Ooi GT Findlay JK Salamonsen LA 《Molecular human reproduction》2003,9(5):279-290
This paper characterizes a novel gene, previously identified as uniquely regulated at implantation in mouse uterus. We cloned its full mRNA sequence encoding a serine protease possessing an IGF-binding domain and named it pregnancy-related serine protease (PRSP). PRSP is structurally similar to mammalian HtrA1 (56% amino acid similarity). Northern analysis revealed that the expression of PRSP mRNA was low before pregnancy, but it was increased at implantation and markedly up-regulated post-implantation. In-situ hybridization localized low levels of mRNA expression to the epithelium and stroma during very early pregnancy, but high expression to the decidual cells on day 8.5, primarily at the mesometrial pole where the placenta was forming. By day 10.5, PRSP mRNA was detected in the placenta. We also cloned an alternatively spliced PRSP mRNA that is expressed at a very low level. We located PRSP gene on chromosome 5 and established its intron/exon structure, which unambiguously explains how the two mRNA variants are produced through alternative splicing. Based on PRSP protein domain structure and its unique expression during pregnancy, we propose that PRSP plays an important role in the formation/function of the placenta. 相似文献
993.
Yoshioka S Fujiwara H Higuchi T Yamada S Maeda M Fujii S 《Molecular human reproduction》2003,9(6):311-319
Melanoma cell adhesion molecule (MCAM) was originally reported to be involved in the invasion and progression of melanoma. It was also shown to be responsible for the attachment of cells to endothelial cells. In this study, we demonstrated by immunohistochemistry that immunoreactive MCAM was not expressed on granulosa cells in the pre-ovulatory follicle, but it was clearly detected in large luteal cells in corpora lutea from the mid-luteal phase of the menstrual cycle. Northern blotting analysis confirmed the expression of MCAM mRNA in corpus luteum. MCAM was weakly detected by immunocytochemical staining in human luteinizing granulosa cells isolated from patients undergoing IVF treatment. Its expression was found to be increased during time in culture of these cells. Flow cytometry and Northern blot analysis revealed that MCAM expression on luteinizing granulosa cells was enhanced when the cells were cultured for 5 days in the presence of hCG (1 IU/ml) or cytokines such as interleukin-1alpha (10 ng/ml) and tumour necrosis factor-alpha (10 ng/ml). No significant difference of MCAM expression was observed between the cultures under normoxic (20% oxygen) and hypoxic (1% oxygen) conditions. These results indicate that luteinizing granulosa cells express MCAM and that MCAM expression is regulated by LH/hCG and cytokines during luteinization. Since MCAM has been reported to mediate cellular interaction with endothelial cells, this molecule may play a role in neovascularization during corpus luteum formation in the human ovary. 相似文献
994.
Detailed investigation of factors influencing amplification efficiency and allele drop-out in single cell PCR: implications for preimplantation genetic diagnosis 总被引:16,自引:0,他引:16
Preimplantation genetic diagnosis (PGD) of single gene disorders relies on PCR-based tests performed on single cells (polar bodies or blastomeres). Despite the use of increasingly robust protocols, allele drop-out (ADO; the failure to amplify one of the two alleles in a heterozygous cell) remains a significant problem for diagnosis using single cell PCR. In extreme cases ADO can affect >40% of amplifications and has already caused several PGD misdiagnoses. We suggest that an improved understanding of the origins of ADO will allow development of more reliable PCR assays. In this study we carefully varied reaction conditions in >3000 single cell amplifications, allowing factors influencing ADO rates to be identified. ADO was found to be affected by amplicon size, amount of DNA degradation, freezing and thawing, the PCR programme, and the number of cells simultaneously amplified. Factors found to have little or no affect on ADO were local DNA sequence, denaturing temperature (94 or 96 degrees C) and cell type. Consideration of the causal factors identified during this study should permit the design of PGD protocols that experience little ADO, thus improving the accuracy of PGD for single gene disorders. 相似文献
995.
Ozçelik B Serin IS Basbug M Uludag S Narin F Tayyar M 《Human reproduction (Oxford, England)》2003,18(8):1703-1706
BACKGROUND: Our main aim was to investigate the effects of melatonin (ME), possibly the most powerful free-radical scavenger, on the prevention of i.p. adhesion formation in rat uterine horn. Our secondary aim was to determine whether different methods of administration of ME were beneficial. METHODS: Animals were randomly assigned into seven groups, each consisting of 13 rats. Measured serosal injury was created using a standard technique. While control and two sham groups were not given ME, two of the remaining four groups were given a single dose of 10 mg/kg (2 mg) of ME i.p. immediately after injury and 30 min prior to injury respectively. In the two other groups, ME treatment was continued daily for 5 days. All animals were killed 2 weeks after surgery and adhesions were determined and scored by a examiner blinded to the test. RESULTS: The extent, severity and total scores of adhesion were found to be significantly reduced in all of the ME treatment groups when compared with control and sham groups. There were no statistically significant differences between the treatment groups. CONCLUSIONS: This study showed that even single dose ME therapy was effective in the prevention of post- operative i.p. adhesion formation. 相似文献
996.
BACKGROUND: This study evaluated the role of conscious sedation in pain relief during termination of first trimester pregnancy by suction evacuation (SE) under local anaesthesia. METHODS: A hundred women undergoing SE before 12 weeks gestation were randomized by computer using the sealed envelope method to receive placebo (saline) or conscious sedation (2 mg midazolam and 25 microg fentanyl) i.v. 5 min before cervical dilatation. Paracervical block was given to all patients, 2 min later. Pain scores during and after SE, post-operative side-effects and satisfaction level were compared. RESULTS: No statistically significant differences in pain scores were found between the two groups. Post-operative side-effects such as dizziness (P = 0.015) and drowsiness (P < 0.001) were significantly more severe in the conscious sedation group. However, patients in the conscious sedation group reported better satisfaction levels than the control group (P = 0.003). CONCLUSION: The use of conscious sedation significantly improved patient satisfaction during termination of first trimester pregnancy by SE under local anaesthesia, despite a lack of improvement in pain relief and the presence of increased severe dizziness/drowsiness in the post-operative period. 相似文献
997.
Espinosa M Noé G Troncoso C Ho SB Villalón M 《Human reproduction (Oxford, England)》2002,17(8):1964-1972
BACKGROUND: Cervical mucus is a heterogeneous mixture of water, ions and mucins that form a hydrophilic polymer gel. Mucins, the main components of mucus, are condensed inside secretory granules and swell to become a hydrogel after exocytosis. Using human cervical secretory cell primary cultures, the effect of [Ca(2+)] and [H(+)] on the swelling velocity of mucin granules was investigated in vitro. METHODS and RESULTS: Immunocytochemistry demonstrated that estrogen and progesterone receptors were expressed in cultured secretory cells along with mucins type 1, 4, 5AC and 5B. Exocytosis of secretory cells, recorded by videomicroscopy, showed that during swelling, the radius of the secretory granule matrix followed first-order kinetics. An increase in extracellular [Ca(2+)] from 1 to 4 mmol/l or a reduction in pH from 7.4 to 6.5 was seen to produce a significant decrease in the velocity of swelling of the secretory granule matrix. CONCLUSIONS: The inverse relationship observed between the diffusion of the granular matrix and the extracellular [Ca(2+)] or [H(+)] suggested that changes in cation concentration might drastically affect the swelling characteristics of mucins and provide a control mechanism for the observed viscoelastic properties of mucus. 相似文献
998.
Morel F Gallon F Amice V Le Bris MJ Le Martelot MT Roche S Valéri A Derrien V Herry A Amice J De Braekeleer M 《Human reproduction (Oxford, England)》2002,17(10):2552-2555
BACKGROUND: Several studies have shown an increased frequency of constitutional chromosome aberrations in male and female partners of couples examined prior to ICSI. We conducted a cohort study to determine whether there was an increase in numerical sex chromosome mosaicism among couples undergoing ICSI compared with fertile couples. METHODS: Cytogenetic investigations were performed in 228 females and 208 males seen for ICSI between January 1997 and March 2001. They were matched to control females and males. RESULTS: Sex chromosome loss or gain was observed in at least one cell from 24.1% of ICSI women in comparison with 22% of controls (not significant). A significant difference between these two groups was found when X chromosome loss in at least two cells was considered, 9.6% for ICSI females versus 4.8% for controls (P = 0.01). No significant difference was observed between male groups concerning loss or gain of the X or Y chromosome. CONCLUSION: Our results support previously published studies indicating that the loss of an X chromosome in a single cell in females undergoing ICSI is probably an artefact. However, they suggest that a woman could have true sex chromosome mosaicism when two 45,X0 cells are found. 相似文献
999.
Culture of menstrual endometrium with peritoneal explants and mesothelial monolayers confirms attachment to intact mesothelial cells 总被引:2,自引:0,他引:2
Witz CA Allsup KT Montoya-Rodriguez IA Vaughn SL Centonze VE Schenken RS 《Human reproduction (Oxford, England)》2002,17(11):2832-2838
BACKGROUND: To evaluate adhesion of menstrual endometrium (ME) to intact peritoneal mesothelium. METHODS: Explants of peritoneum were cultured for 1 h with ME (n = 6). Specimens were serially sectioned for haematoxylin and eosin stain and immunohistochemistry using an anti-cytokeratin antibody to label mesothelium. Confocal laser scanning microscopy (CLSM) was performed to identify an intact layer of mesothelial cells (MC) underlying sites of ME attachment. Also, ME and MC were labelled with Cell-Tracker dyes. ME was cultured with mesothelial monolayers for 1 h (n = 10). Cultures were examined with differential interference contrast and CLSM. Optical sections were taken and a three-dimensional model was constructed. RESULTS: In the peritoneal explants, ME adhered to intact mesothelium. There was no evidence of transmesothelial invasion. CLSM of sections of the explants demonstrated an intact monolayer of cytokeratin positive cells below the sites of ME implantation. Cytokeratin negative and positive ME cells adhered to mesothelial cells. Likewise, the ME attached to cultured mesothelium. Orthogonal sections and three-dimensional reconstruction confirmed an intact monolayer of mesothelium underlying ME attachment sites. CONCLUSIONS: This study confirms that ME adheres rapidly to intact peritoneal mesothelium. Further studies are needed that characterize the mechanisms of ME adhesion to, and migration through, mesothelial cells. 相似文献
1000.
Pre-eclampsia, one of the most significant health problems inhuman pregnancy, complicates 6-7% of all gestations and is theleading cause of fetal growth retardation, infant morbidityand mortality, premature birth and maternal death. Recent researchimplicates free radicals in the pathophysiology of pre-eclampsia.This review covers the biochemistry of nitric oxide (NO) andpossible interactions with other free radicals. Studies in therat show that pregnancy is associated with enhanced productionand responsiveness to NO in both reproductive tissues and bloodvessels. Rats infused with NG-nitro-L-arginine methyl ester(L-NAME, a NO synthase inhibitor) have been used as an animalmodel of pre-eclampsia, and the effects of steroid hormoneson blood pressure in this model have been tested. Results suggestthat pre-eclampsia may be a state of NO deficiency. However,in humans there seem to be contradictions regarding the involvementof NO in maternal adaptation to pregnancy. It is suggested thatNO may be one of several systems that act in concert to maintaina symbiotic relationship between mother and fetus. However,the input of each system may be genetically determined. 相似文献